Anterior Cruciate Ligament Primary Reconstruction in Acute and Chronic Ruptures

Patients presenting with acute complete ruptures of the anterior cruciate ligament (ACL; >5 mm of increased anterior tibial translation and positive pivot shift test) are treated with rehabilitation until pain and swelling subside and joint motion and muscle function are restored. This delay markedly reduces the incidence of postoperative complications of knee motion limitations and muscle weakness. All patients with acute ruptures are profiled with regard to their desired future activity level to determine whether ACL reconstruction is warranted.¹³⁹ Those who wish to return to high-risk activities, including strenuous athletics or occupations involving pivoting, cutting, twisting, and turning, are considered for reconstruction. In patients with acute ACL ruptures and a concomitant displaced bucket-handle meniscus tear, surgery within 2 weeks is required to reduce the meniscus to a normal location and repair the tear. The ACL reconstruction may be performed at the same setting; however, knees with excessive swelling and pain undergo meniscus repair first. After an appropriate period of rehabilitation, ACL reconstruction is performed.

Patients involved in low-risk activities or who are willing to avoid strenuous athletic and occupational activities that place the knee at increased risk for giving-way episodes may not require ACL reconstruction. The patient is placed into a conservative treatment program that includes rehabilitation to regain muscle strength and neuromuscular function and counseling on the risk of future giving-way reinjuries and potential damage to the joint. Even with surgical reconstruction, patients are informed that an ACL rupture is a serious injury and it is unlikely that they will ever have a truly normal knee joint. The injury may also involve a bone bruise and chondral damage, with sequelae for future joint symptoms. The goal of conservative management is to prevent recurrent giving-way reinjuries, which are deleterious to the joint because they frequently result in meniscus tears and subsequent meniscectomy. It is important to categorize the knee joint as to the injury that has occurred. Repairable meniscus tears almost always indicate a concurrent ACL reconstruction. Otherwise, the success of the meniscus repair may be compromised.^40,108,157 DeHaven and coworkers⁴⁰ documented higher failure rates of meniscus repairs in knees with ACL deficiency than in knees with normal ACL function (46% and 5%, respectively) in a 10-year follow-up study. A grade III pivot shift and grossly positive Lachman test (increased ≥ 10 mm anterior tibial translation) indicate involvement of the secondary ligamentous restraints and, in the authors’ experience, an increased risk of giving-way reinjuries with recreational activities. Patients with physiologic laxity of other ligaments or partial tears (second-degree) of medial or lateral ligaments frequently have a grossly positive pivot shift test, as discussed in Chapter 3, The Scientific Basis for Examination and Classification of Knee Ligament Injuries.

Critical Points INDICATIONS

• Complete anterior cruciate ligament (ACL) rupture: >5 mm of increased anterior tibial translation, positive pivot shift test.

• Profile patient for desired future activity level.

• High-risk activities (pivoting, cutting, twisting, turning): reconstruct.

• Acute ACL rupture and concomitant displaced bucket-handle meniscus tear: surgery within 2 wk to repair meniscus, usually concurrent ACL reconstruction.

• Low-risk activities, willing to avoid strenuous activities that place the knee at increased risk for giving-way episodes: conservative treatment.

• Partial ACL tears: <50% fibers torn, conservative treatment; >50% torn in athlete, consider graft augmentation.

• Revision ACL

Address all pathologies before surgery: lower limb malalignment, muscle atrophy, limitation knee motion, gait abnormalities, misplaced tunnels.

Goals, outcome of surgery depend on preexisting joint damage, associated procedures required.

The rationale for the indications for ACL reconstruction is based on a study of 103 patients with chronic ACL ruptures.¹⁴¹ These knees had no other ligament injuries and had not undergone reconstruction. The patients were evaluated a mean of 5.5 years after the initial knee injury; a subgroup of 39 patients presented an average of 11 years postinjury. This study was not a natural history study, because all patients sought treatment owing to symptoms. After the initial injury, 82% of the patients returned to sports activities, which gave an initial false impression of the seriousness of the ACL disruption. After 5 years, only 35% were continuing athletics, often with recurrent symptoms of pain or swelling. A significant reinjury occurred in 36 patients within 6 months and in 53 patients within the 1st year after the initial injury. Moderate to severe symptoms of pain, swelling, and/or giving-way were reported in 32 patients during walking, in 45 patients during activities of daily living, and in 73 patients during turning or twisting athletic activities. Giving-way occurred in 22 patients during walking, in 34 patients during recreational sports, and in 66 patients during strenuous sports. Knees that had undergone meniscectomy had a two- to fourfold increase in pain and swelling symptoms. Radiographic findings lagged behind clinical findings, because 44% of patients in the subgroup 11 years from injury had moderate to severe arthritic changes. The “ring” sign was noted, which represents an osteophyte (Fig. 7-1) that forms around the circumference of the lateral tibial plateau. This is associated with an absence of a pivot shift phenomena, but abnormal anterior tibial translation, because the lateral femoral condyle rotation is restrained by the osteophyte and increased concavity of the lateral tibial plateau.

FIGURE 7-1 The “ring” sign (arrows) represents an osteophyte that forms around the circumference of the lateral tibial plateau with degenerative arthritis, which may diminish the pivot shift phenomena.

In a follow-up study, 84 of the initial 103 patients underwent a repeat evaluation 3 years after initiating a conservative and activity modification treatment program.¹³⁹ The frequently quoted “rule of thirds” represents the outcome of this study regarding the effects of an ACL injury on subsequent functional activities. Approximately one third of the patients showed improvement in symptoms and functional limitations with daily or recreational activities, one third did not improve, and one third became worse with continuing symptoms and limitations. Thirty percent of the patients were noncompliant with the activity modification recommendations and stated they would continue athletics despite symptoms and the increased risk for future arthritis (labeled “knee abusers”). These patients had the poorest overall prognosis with conservative management. This general rule of thirds is not specific to individual patients with chronic ACL insufficiency because it does not take into account the presence of meniscus and arthritis grading, compliance with activity modification, and maintenance of a muscle strengthening program. The frequency of giving-way episodes correlated with chronic pain, swelling, and functional limitations. The conclusion was reached that any giving-way episode with athletics, even if followed by periods of no giving-way or other symptoms, was to be absolutely avoided because meniscus tears and joint deterioration result. The results of this program show the importance of counseling the patient on the expected levels of athletic activity possible and following closely those who do not initially choose to have surgery to lessen the chance of significant arthritis in future years.

Partial ACL tears occur more frequently than suspected and present in a manner similar to complete ACL ruptures. These injuries frequently occur from a noncontact giving-way episode during jumping or pivoting and are often accompanied with a popping sensation and acute hemarthrosis. There is a limitation of full extension with pain on even gentle attempts to passively achieve 0°, mimicking a torn displaced meniscus, which requires magnetic resonance imaging (MRI) to exclude a mechanical block to knee extension. In a study reported by the senior author and associates¹⁴⁰ of 32 knees with a partial ACL tear verified arthroscopically, a tear to one or both menisci occurred in 53%. An average of 67 months (range, 24–110 mo) postinjury, 38% had progressed to complete ACL deficiency. The arthroscopic evaluation of the extent of ACL disruption was related to the prognosis and progression to complete ACL deficiency. Even though the arthroscopic evaluation does not define the true extent of ligament injury on a microscopic or functional basis, 86% of knees in which 75% of the ACL was torn progressed to ACL deficiency.¹³⁶ One half of the knees with an estimated injury involving 50% of the ligament progressed to ACL deficiency, even though major portions of the ACL were still intact, preventing a pivot shift phenomena. Only 12% of knees that had an estimated one fourth or less of the ligament torn progressed to complete ACL deficiency; therefore, these knees had a reasonably good prognosis for return to athletics.

Messner and Maletius¹⁰⁴ followed 22 consecutive patients with partial ACL ruptures (no more than 50% of the ACL fibers torn) a mean of 12 years postinjury; all but 1 were also reexamined a mean of 20 years postinjury. No patient required ACL reconstruction. Patients decreased their level of activity from contact sports to recreational activities. Few had an increase in anterior translation or the pivot shift test, and little differences were noted in symptoms between follow-up evaluations.

Based on these data, the following rules apply for the management of partial ACL tears. Knees with tears of 50% or less of the ACL fibers are not candidates for reconstructive surgery. The patients are advised that they need to be followed yearly. The chance for progression to complete ACL deficiency in the greater than 50% tear group is at least one in two knees. In the athletic individual, a single-graft augmentation is a consideration to provide stability and retain the remaining function of the ACL. In the more sedentary patient who may wish to choose a nonoperative treatment of a complete ACL rupture, a reconstruction is not warranted.

Revision ACL Reconstruction

Many factors influence the failure rate of ACL surgery.* The definition of a failed ACL reconstruction includes a return of knee instability (increased anterior tibial translation and internal tibial rotation as demonstrated by positive Lachman and pivot shift tests) and, in many cases, the presence of associated pathologies. These include limitation of knee motion with pain and stiffness, muscle atrophy from inadequate rehabilitation, articular cartilage damage, meniscectomy and its effects on joint symptoms and function, undiagnosed lower limb malalignment, and posterolateral (PL) or medial ligament deficiency. When present, each of these pathologies must be addressed and resolved before or during ACL revision. The goal is to restore the best possible function to the knee joint and lower extremity before ACL revision to maximize the success rate and minimize the possibility of failure of the revision procedure. Importantly, the patient and surgeon must address the goals of the revision because associated knee joint damage requires modification or elimination of strenuous, high-impact activities. Often, the patient has had multiple prior surgical procedures that have not achieved the desired outcome.^118,126,131 The potential of the revision operation in these cases to accomplish the patient’s goals must be realistically discussed.

A number of preoperative and operative issues are addressed in a methodical manner in order to salvage knee function and obtain a reasonable result after prior ACL procedures have failed. These may include the necessity to perform staged procedures to correct lower limb malalignment with an osteotomy or fill enlarged or misplaced tibial and femoral tunnels with a bone graft. Patients may require extensive rehabilitation to restore normal joint motion and neuromuscular control. The approach is taken to maximize every aspect of the patient’s knee condition and not accept any abnormality, such as a slightly misplaced tunnel or concurrent knee instability, in planning the revision procedure.

Other chapters in this book address issues related to correction of lower limb malalignment, arthrofibrosis, and muscle atrophy; procedures for articular cartilage defects; meniscus transplantation; and PL and medial ligament reconstructions. Although the timing of these procedures is addressed in this chapter, the principal focus relates to surgical planning and technique decisions that, in the authors’ experience, will improve the success of the ACL revision.

Patients presenting for ACL revision fall into one of three categories, each of which has a different prognosis. In the most ideal category are knees with a misplaced tibial or femoral tunnel that have intact menisci and articular cartilage and no associated ligament instability. In these cases, the revision procedure is similar to a primary ACL reconstruction in terms of an expected good functional outcome. In the most severe category are knees that had a previous meniscectomy, articular cartilage damage, associated ligament instabilities, or lower limb malalignment. These patients will have an expected less than ideal outcome and the revision represents a salvage situation. In the middle of these two extremes are patients who have partial or complete loss of meniscus function, associated cartilage damage, and a residual pivot shift from a failed ACL procedure, but no associated lower limb malalignment or other ligament instability. The outcome for providing stability in these cases is good; however, further joint deterioration will occur over time and counseling must be undertaken for activity modification. In select cases, indications exist for a partial cartilage restoration procedure, including meniscus transplantation. Clinical studies on ACL revision usually contain a selection bias regarding the inclusion of patients from these three categories, which accounts for the differences in reported outcomes between investigations. The majority of studies report that the outcome of ACL revision is inferior to that of primary reconstruction. Usually, the revision procedures are performed many months or years after the failure of the primary reconstruction, during which time further giving-way episodes and joint deterioration occur that compromise the final outcome.

A frequent clinical presentation after an ACL reconstruction with a vertical ACL graft is a negative or mildly positive Lachman test and a positive pivot shift test reproducing the patient’s complaints of residual giving-way with activities. These patients are candidates for an ACL revision in which the entire ACL graft is removed and an anatomic ACL graft replacement is performed. In select knees, the primary ACL graft is retained and a second graft is placed in a more suitable anatomic location to provide rotational stability, as is discussed later.

Effect of ACL and Lateral Structures on Anterior Tibial Translation and Internal Tibial Rotation Limits

The function of the ACL is discussed in Chapter 3, The Scientific Basis for Examination and Classification of Knee Ligament Injuries. Additional information regarding the restoration of ACL function related to surgical techniques and graft placement issues are discussed in this section. The ACL is the primary restraint to anterior tibial translation, providing 87% of the total restraining force at 30° of knee flexion and 85% at 90° of flexion.²⁹ The iliotibial band (ITB), midmedial capsule, midlateral capsule, medial collateral ligament (MCL), and fibular collateral ligament (FCL) provide a combined secondary restraint to anterior tibial translation. The posteromedial (PM) and PL capsule structures provide added resistance with knee extension. The secondary restraints may become deficient after an ACL injury or repeat giving-way episode, resulting in increased symptoms.

The ACL resists the coupled motions of anterior tibial translation and internal tibial rotation along with the lateral structures. In the authors’ laboratory, Wroble and colleagues¹⁹⁶ measured in ACL-deficient knees the simulated effect of lateral soft tissue injuries on internal tibial rotation and anterior tibial translation. The experimental design consisted of a six-degrees-of-freedom instrumented spatial linkage and loading of the knee joint under defined loads of 100 N anteroposterior (AP), 15 Nm varus-valgus, and 5 Nm internal-external tibial rotation torque. The limits of knee motions were determined in the intact knee and then after sectioning the ACL, ITB, lateral capsule, popliteus tendon and popliteofibular ligament, and PL capsule.

The effect of sectioning the ACL first, followed by the ITB and lateral capsule, is shown in Figure 7-2. Two distinct responses were measured. In the first set of knees (see Fig. 7-2A), there were only moderate increases in anterior tibial translation after ACL sectioning and negligible further increases after sectioning the ITB and lateral capsule. However, in the second set of knees (see Fig. 7-2B), much larger increases were noted in anterior tibial translation after sectioning the ACL and even greater increases were found after sectioning the ITB and lateral capsule. These findings are compatible with clinical tests after ACL injury in which, in some knees, there may be only a moderate increase in anterior tibial translation, whereas in others, a much larger increase is present. This concept is discussed in Chapter 3, The Scientific Basis for Examination and Classification of Knee Ligament Injuries, using the analogy of the bumper model to simulate the effect of the secondary restraints on motion limits once the ACL is removed. Clinically, an ACL graft would be expected to be subjected to greater in vivo forces in the second set of knees without the unloading provided by relatively “tight” secondary restraints. The increase in the magnitude of anterior translation in these physiologically loose knees after loss of the anterolateral structures results in a grade III pivot shift phenomenon. These knees require a high-strength, securely fixated ACL graft to resist these major displacements, and autografts are highly recommended in these grossly unstable knees, as is discussed later.

FIGURE 7-2 Limits of anterior translation for intact specimens and with the anterior cruciate ligament (ACL) and ACL/ALS cut (100 N). ALS, iliotibial band, lateral capsule. A, In these specimens, anterior translation in the intact state was low and, with sectioning of the ACL, moderate increases were found throughout the range of motion. Further sectioning of the ALS produced < 3 mm of increase in anterior translation, predominantly in the flexed knee. B, In this group of specimens, anterior translation in the intact state was higher than in the group of specimens shown in A at low flexion angles. After cutting the ACL, anterior translation was markedly increased in the 15°–30° of flexion range. After further sectioning of the ALS, large anterior translation increases were found at all flexion angles.

(A and B, From Wroble, R. R.; Grood, E. S.; Cummings, J. S.; et al.: The role of the lateral extra-articular restraints in the anterior cruciate ligament–deficient knee. Am J Sports Med 21:257–262; discussion 263, 1993.)

The effect of sectioning the lateral and posterolateral structures (PLS) is shown in Figure 7-3.¹⁹⁶ Sectioning of the FCL or PLS (popliteus tendon, popliteofibular ligament, PL capsule) produced statistically significant, but small, increases in anterior tibial translation at low flexion angles. The combined ACL-ALS (anterolateral structures; ITB, anterior and middle portions of the lateral capsule)–FCL-sectioned knee had large increases in anterior tibial translation, with the greatest changes occurring at higher flexion angles.

FIGURE 7-3 Limits of anterior translation for intact specimens and with serial sectioning of the ACL and lateral structures (100 N). Increases in anterior translation with sectioning the ACL are statistically significant at all flexion angles. For the ACL/PLS/FCL cut state, the only statistically significant increase was at 0° of flexion. For the ACL/ALS/FCL cut state, increases were statistically significant at 15° of flexion and above. Increases for the ALL cut state were statistically significant at all flexion angles. Anterior translation at 30° and 90° of flexion is approximately equal when the secondary lateral restraints are removed. ALS, iliotibial band, lateral capsule; FCL, fibular collateral ligament; PLS, posterolateral structures (popliteus tendon and popliteofibular ligament, posterolateral capsule).

(From Wroble, R. R.; Grood, E. S.; Cummings, J. S.; et al.: The role of the lateral extra-articular restraints in the anterior cruciate ligament–deficient knee. Am J Sports Med 21:257–262; discussion 263, 1993.)

The effect of sectioning the ACL and lateral structures on the limits of internal tibial rotation are shown in Figure 7-4. Sectioning of the ACL produced only a small increase in the final internal rotation limit. Sectioning of the ALS and the FCL produced a sequentially larger increase in internal tibial rotation. In select revision knees that have large increases in internal tibial rotation, the data support the role of a lateral extra-articular procedure to partially unload the ACL graft.

FIGURE 7-4 Limits of internal rotation for intact specimens and with the ACL, ACL/ALS, ACL/ALS/FCL, and ALL structures (ACL/ALS/FCL/PLS) cut (5 Nm). Increases in internal rotation with the ACL cut (statistically significant) are so small that they are clinically unimportant. With ACL/ALS sectioning, increases in internal rotation are statistically significant at 30° of flexion and above. Statistically significant increases are found at 15° of flexion and above in the ACL/ALS/FCL cut state and at all flexion angles for the ALL cut state. The effect of the PLS on restraining internal rotation in the extended knee can be seen by comparing the ACL/ALS/FCL curve and the ALL cut curve. The differences between these curves reflects sectioning the PLS. The largest differences are found at 15° and 30° of flexion.

(From Wroble, R. R.; Grood, E. S.; Cummings, J. S.; et al.: The role of the lateral extra-articular restraints in the anterior cruciate ligament–deficient knee. Am J Sports Med 21:257–262; discussion 263, 1993.)

The conclusions from this study support the ACL as the primary restraint to anterior tibial translation. The data show the ultimate limit for internal tibial rotation is resisted by the lateral extra-articular structures that are tightened by the internal tibial rotation. The ACL limits internal rotation in the midrange of the envelope of tibial rotation, but not at the final limit of internal rotation. This is an important concept because clinical and biomechanical studies frequently attempt to measure increases in internal tibial rotation after ACL surgery in an attempt to quantify ACL graft function. Accordingly, this approach would not be expected to be successful. When the ITB and lateral capsule are physiologically slack, the FCL and ACL assume increased importance in limiting internal rotation. In summary, ACL function is ideally described by the restraining effect of limiting the coupled motions of internal tibial rotation and anterior tibial translation. A positive pivot shift test represents the effect of both of these increased motions, accounting for the anterior subluxation of the lateral and medial tibiofemoral compartment.

The motions that occur during the pivot shift maneuver are shown in Figure 7-5. At the beginning of the tests, the lower extremity is simply supported against gravity. After ACL disruption, both anterior tibial translation and internal tibial rotation increase as the femur drops back and externally rotates with subluxation of the lateral tibiofemoral compartment. This position is accentuated as the tibia is lifted anteriorly. At approximately 30° knee flexion, the tibia is pushed posteriorly, reducing the tibia into a normal position with the femur. From position C to position A (see Fig. 7-5B), the knee is extended to again produce the subluxated position. In addition to major increases in anterior tibial translation, there is also an increase in internal tibial rotation (midrange limit increase).

FIGURE 7-5 A, (Right) Flexion-rotation drawer and pivot shift tests, subluxated position. With the leg held in neutral rotation, the weight of the thigh causes the femur to drop back posteriorly and rotate externally, producing anterior subluxation of the lateral tibial plateau. (Left) Reduced position. Gentle flexion and a downward push on the leg reduces the subluxation. This test allows the coupled motion of anterior translation–internal rotation to produce anterior subluxation of the lateral tibial condyle. B, The knee motions during the tests are shown for tibial translation and rotation during knee flexion. The clinical test is shown for the normal knee (open circle) and after ligament sectioning (dotted circle). The ligaments sectioned were the ACL, iliotibial band, and lateral capsule. Position A equals the starting position of the test, B is the maximum subluxated position, and C indicates the reduced position. The pivot shift test involves the examiner applying larger rotational loads, which increase the motion limits during the test.

(A, From Noyes, F. R.; Bassett, R. W.; Grood, E. S.; et al.: Arthroscopy in acute traumatic hemarthrosis of the knee. J Bone Joint Surg Am 62:687–695, 1980; B, from Noyes, F. R.; Grood, E. S.; Suntay, W. J.: Three-dimensional motion analysis of clinical stress tests for anterior knee subluxations. Acta Orthop Scand 60:308–318, 1989.)

The effect of the ACL in providing rotational stability to the motions of anterior translation and internal tibial rotation is shown in Figure 7-6. After ACL sectioning, there is an increase in medial and lateral compartment translation as the center of rotation shifts from inside the knee joint to outside the medial compartment. The medial ligamentous structures influence the new center of rotation. With injury to the medial ligament structures, the center of rotation shifts so far medially that a rotational motion is essentially lost, resulting in a gross anterior subluxation of both compartments. The data show the important surgical concept of restoring injured medial and lateral ligament structures to restore anterior knee stability in conjunction with the ACL.

FIGURE 7-6 Intact knee and after ACL sectioning: response to coupled motions of anterior tibial translation and internal tibial rotation. A, Intact knee. The center of rotation may vary between the medial aspect of the PCL and the meniscus border, based on the loads applied and physiologic laxity of the ligaments. B, ACL sectioned; note shift in center of tibial rotation medially. The effect of the increase in tibial translation and internal tibial rotation produces an increase in medial and lateral tibiofemoral compartment translation (anterior subluxation). The millimeters of anterior translation of the tibiofemoral compartment represents the most ideal method to define knee rotational stability (see Chapter 3, The Scientific Basis for Examination and Classification of Knee Ligament Injury). The center of rotation under a pivot shift type of test shifts to the intact medial ligament structures. If these are deficient, the center of rotation shifts outside the knee joint.

Division of the ACL into Anteromedial and Posterolateral Bundles

Controversy exists in published studies on the division of the ACL into two distinct fiber bundles. Some authors provide evidence of both an anatomic and a functional division, whereas others doubt that this division exists and argue that ACL fiber function is too complex to be artificially divided into two bundles. In some studies,^4,32 the anteromedial (AM) bundle is identified functionally at its femoral location as the proximal half of the attachment (knee in extension) that tightens with knee flexion. The PL bundle is identified as the distal half of the ACL femoral attachment that tightens with knee extension. The PL bundle is described to relax with knee flexion, as the ACL femoral attachment changes from a vertical to a horizontal structure. The problem is that this classic description of a reciprocal tightening and relaxation of the AM and PL bundles occurs under no anterior loading conditions. With substantial anterior tibial loading, and in particular with a coupled motion of anterior translation and internal tibial rotation, the majority of the ACL fibers are brought into a load-sharing configuration to a differing percentage, as is presented later.

The authors believe the characterization of the ACL into two fiber bundles represents a gross oversimplification not supported by biomechanical length-tension laboratory studies.^70,169 Zavras and coworkers²⁰⁵ published a comparative study on previously published isometric points for the ACL and concluded that the ACL isometric zone was high and proximal in the ACL attachment, close to the posterior end of Blumensaat’s line. This data, along with other studies, focused on placing grafts in the proximal aspect of the ACL attachment, in a so-called isometric position. The problem with applying published isometric data to the clinical situation is that the data are valid only for knee flexion-extension and do not indicate the most effective ACL graft position for controlling knee rotational loading as occurs during the pivot shift test. To date, data regarding the most effective graft positions to resist the coupled motions of anterior translation and internal rotation are not available. However, there are data on what graft placement positions are ineffective and should be avoided.

The length-tension behavior of ACL fibers is primarily controlled by the femoral attachment in reference to the center of femoral rotation, the coupled motions applied, the resting length of ACL fibers, and tibial attachment locations. In Chapter 3, The Scientific Basis for Examination and Classification of Knee Ligament Injuries, the concept of an isometric transition zone or contour plot is presented. The zone represents a central transition zone in which fibers undergo 2 mm of length change during knee flexion and extension. This zone is not an isometric zone, because the length change is not zero. All ACL fibers anterior to the zone lengthen with knee flexion, whereas the posterior fibers lengthen with knee extension. Under loading conditions, fibers in both the AM and the PL divisions contribute to resist tibial displacements. ACL fibers in the PL division attach in part posterior to the transitional zone and lengthen with knee extension. Note that the function of the ACL fibers is determined by the anterior-to-posterior direction (knee at extension) as well as the proximal-to-distal femoral attachment. Placement of a graft in an anterior or a posterior position has a large effect in producing deleterious lengthening and graft failure. The obvious example is a graft placed anterior to “residents’ ridge,” which is anterior to the femoral ACL attachment. The proximal-to-distal division used in two-bundle descriptions as the control of fiber length in knee flexion and extension oversimplifies the functional behavior of the ACL fibers, which are even more dependent on the AP femoral attachment.

The division of the ACL into two bundles was historically based on the tibial attachment site and not on a corresponding femoral attachment site. Recent studies project the tibial bundles onto two corresponding femoral sites. In these studies, to be described, the authors usually divide the ACL femoral attachment site at a midpoint into a corresponding AM and PL bundle. In the authors’ opinion, there is not at present convincing anatomic data to support a division of the ACL into two separate bundles, although one study⁵⁰ reported a bony ridge between the two femoral attachment bundles. Because of the lack of a clear anatomic division of the ACL into two bundles, there is discrepancy among authors on anatomic descriptions of the ACL “bundles” and recommendations for the surgical technique on tibial and femoral tunnels for two bundle graft reconstructions.

Colombet and associates³² measured the ACL femoral and tibial attachments of the AM and PL bundles in seven unpaired cadaveric knees. The reference position of the retroeminence ridge (RER), representing the posterior interspinous ridge anterior to the posterior cruciate ligament (PCL) attachment, provided an important landmark for measuring from this point to the posterior ACL attachment. The tibial measurement points are shown in Figure 7-7 and the mean values are displayed in Table 7-1. Note the ACL extends posteriorly on the tibia to a distance 10.3 ± 1.9 mm from the RER line (coordinate bg). There is a discrepancy in the published text where this measurement is reported to be 7.1 mm. The mean length of the ACL (coordinate ag) was 17.6 ± 2.1 mm. The distance between the center of the AM and the center of the PL bundle (coordinate ef) was 8.4 ± 0.6 mm. The authors reported that the AM bundle was an average of 17.8 ± 1.7 mm anterior to the RER. The center of the ACL attachment was 19 mm anterior to the RER line. The center of the PL and AM bundles was determined to lie at 52% and 36% of the tibial width (line described by Amis and Jakob⁵ that passes through the posterior corner of the tibial plateau and parallel to the medial tibial surface). The appearance of the ACL tibial attachments of the AM and PL bundles are shown in Figure 7-8 and represents a medial-to-lateral division, different from other authors who depict an anterior-to-posterior division.

FIGURE 7-7 Tibia in the axial view with tibial measurement points of ACL attachment (a–m). a, Anterior extent; b, posterior extent; c, medial extent; d, lateral extent; e, projection of the center of the anteromedial (AM) bundle onto the ACL attachment area; f, projection of the center of the posterolateral (PL) bundle onto the ACL attachment area; g, retroeminence ridge; h, posterior border of the tibial plateau; i, anterior border of the tibial plateau; l, lateral border of the tibial plateau; m, medial border of the tibial plateau.

(From Colombet, P.; Robinson, J.; Christel, P.; et al.: Morphology of anterior cruciate ligament attachments for anatomic reconstruction: a cadaveric dissection and radiographic study. Arthroscopy 22:984–992, 2006.)

FIGURE 7-8 Appearances of the tibial ACL attachments. The projection of the central fibers of the AM bundle onto the attachment area is shown by a white dot (point e), and similarly, the projection of the central fibers of the PL bundle is shown by a black dot (point f).

(From Colombet, P.; Robinson, J.; Christel, P.; et al.: Morphology of anterior cruciate ligament attachments for anatomic reconstruction: a cadaveric dissection and radiographic study. Arthroscopy 22:984–992, 2006.)

The corresponding femoral attachments of the ACL from this study are shown in Figures 7-9 and 7-10 and the mean values are provided in Table 7-2. The overall length of the ACL was 18.3 ± 2.3 mm, with the center of the AM and PL bundles a mean of 8.2 mm apart and approximately 5 mm from the proximal and distal end of the ACL attachment. The authors recommended that the center of the PL bundle be located 8 mm lower and “shallower” in the notch than the center of the AM bundle. The femoral attachment was 2.5 mm from the articular cartilage. Using the grid system of Bernard and colleagues¹⁹ (shown in Fig. 7-10), the center of the AM bundle was 26.4% ± 2.6%, and the center of the PL bundle was 32.3% ± 3.9% the length of Blumensaat’s line.

FIGURE 7-9 Femur in the sagittal view with femoral measurement points of the ACL attachment area (A–J). Both anatomic and corresponding surgical navigation terminology have been used for clarity. A, Distal border (“low” in the notch); B, proximal border (“high” in the notch); C, anterior border (“shallow” in the notch); D, posterior border (“deep” in the notch); E, projection of the center of the AM bundle onto the ACL attachment area; F, projection of the center of the PL bundle onto the ACL attachment area; G, posterior margin of the articular cartilage (“deep” in the notch); H, distal margin of the articular cartilage (“low” in the notch); I, “over-the-top” position (“high” in the notch); J, most anterior point of the roof of the notch.

(From Colombet, P.; Robinson, J.; Christel, P.; et al.: Morphology of anterior cruciate ligament attachments for anatomic reconstruction: a cadaveric dissection and radiographic study. Arthroscopy 22:984–992, 2006.)

FIGURE 7-10 Position of the centers of the AM and PL bundles on the grid described by Bernard et al.¹⁹

(From Colombet, P.; Robinson, J.; Christel, P.; et al.: Morphology of anterior cruciate ligament attachments for anatomic reconstruction: a cadaveric dissection and radiographic study. Arthroscopy 22:984–992, 2006.)

In the most extensive study to date, Edwards and coworkers⁴⁵ defined the ACL tibial attachment in 55 cadaveric specimens. In Figure 7-11, the tibial bony landmarks are depicted. The “over-the-back” ridge (RER) again corresponds to the interspinous ridge just anterior and proximal to the PCL attachment. In Figure 7-12, the authors present their recommendations for best-fit central and two tunnel positions. The center of the ACL attachment was 15 ± 2 mm (range, 11–18 mm) from the RER at 36% of the AP depth of the tibia. The center of the PL bundle anterior from the RER was 10 ± 1 mm (range, 8–13 mm) and the AM bundle was 17 ± 2 mm (range, 13–19 mm), corresponding to 29% and 46% of the tibial depth, respectively. The authors noted, in disagreement with other publications, that they were not able to define two separate anatomic bundles. Instead, they defined two functional bundles by observing the tightening and slackening behavior of the ACL fibers during flexion and extension.

FIGURE 7-11 Schematic diagram of the tibial plateau depicts the landmarks used in this study. A, Anterior tibial surface; B, apex of medial tibial spine; C, lateral border of medial tibial spine; D, “over-the-back” ridge; E, posterior tibial axis; F, width; G, depth.

(From Edwards, A.; Bull, A. M.; Amis, A. A.: The attachments of the anteromedial and posterolateral fibre bundles of the anterior cruciate ligament: part 1: tibial attachment. Knee Surg Sports Traumatol Arthrosc 15:1414–1421, 2007; with kind permission of Springer Science+Business Media.)

FIGURE 7-12 Schematic diagram of a left knee depicts the best-fit ellipses marking the centers of the AM and PL bundles (A); the positions of 6-mm tunnels placed in the posteromedial limits of the AM and PL bundles (B); and the center of the ACL attachment (C).

(From Edwards, A.; Bull, A. M.; Amis, A. A.: The attachments of the anteromedial and posterolateral fibre bundles of the anterior cruciate ligament: part 1: tibial attachment. Knee Surg Sports Traumatol Arthrosc 15:1414–1421, 2007; with kind permission of Springer Science+Business Media.)

Stabuli and Rauschning^174a reported the center of the ACL tibial attachment at 43% of the AP depth, which extended from 25% to 62% of the tibial width. These important landmarks provide a reference to measure lateral radiographs before and after ACL graft placement to avoid a posterior and vertical graft placement (Fig. 7-13). Siebold and associates¹⁷¹ performed a cadaveric study in 50 knees and documented the ACL tibial insertion using a digital image analysis system and divided the ACL into AM and PL bundles. The average AP length of the ACL tibial attachment was 14 mm (range, 9–18 mm). The average male ACL tibial insertion area was 130 mm² versus the average female knee of 106 mm². The average AP length of the ACL footprint in females was 14 mm (range, 9–18 mm), and in males, 15 mm (range, 12–18 mm). The average width of the ACL in all knees was 10 mm. The study concluded that two tibial bone tunnels cannot be placed at the anatomic centers of the AM and PL bundles because the space is too narrow and the tunnels would overlap. This highlights the difficulty of the ACL double-bundle technique in re-creating the native ACL fiber attachment.

FIGURE 7-13 Schematic drawing of tibial insertion of ACL and its orientation with the knee in extension. In this cryosectional knee specimen (right knee, midsagittal plane, medial view at 0° of flexion, i.e., in the extended knee position, specimen 5), the inclination of a tangent constructed to the intercondylar roof formed an angle of 42° with respect to the midsagittal femoral shaft axis. The anterior limit of the ACL was located at 11 mm (23.4%), the central part at 20 mm (42.6%), and the posterior limit at 29 mm (61.7%) when determined from the anterior tibial margin and calculated over the total sagittal diameter of the tibia, which measured 47 mm (100%). F, femur; P, patella; T, tibia; 1, quadriceps tendon; 2, patellar tendon; 3, Hoffa’s fat pad (corpus adiposum intrapatellare); 4, infrapatellar plica; 5, synovial fold of PCL; 6, roof of intercondylar fossa; 7, anterior tibial margin; 8, anterior limit of ACL; 9, central part of ACL; 10, posterior limit of ACL; 11, tibial attachment site of PCL at posterior intercondylar area; 12, posterior tibial margin at posterior intercondylar area; 13, popliteal artery.

(From Staubli, H. U.; Rauschning, W.: Tibial attachment area of the anterior cruciate ligament in the extended knee position. Anatomy and cryosections in vitro complemented by magnetic resonance arthrography in vivo. Knee Surg Sports Traumatol Arthrosc 2:138–146, 1994; with kind permission of Springer Science+Business Media.)

Zantop and colleagues²⁰⁴ performed a cadaveric study in 20 knees that outlined the AM and PL bundle locations at the tibial and femoral sites. The authors arrived at different conclusions from those of Siebold and associates.¹⁷¹ The tibia ACL division into the AM bundle was oriented from medial to lateral and occupied the anterior one half of the ACL footprint and was aligned with the anterior horn of the lateral meniscus. The center of the PL bundle was located 11 mm posterior and 4 mm medial to the anterior insertion of the lateral meniscus. The center of the AM bundle was located at 30% and the PL bundle was located at 40% on the lateral transtibial line.

Edwards and coworkers⁴⁶ described the anatomic locations of the ACL femoral attachments of the AM and PL bundles in a companion study in 22 cadaveric knees using a measurement grid system shown in Figure 7-14. The authors reported a wide variation in the size and shape of the ACL attachment and bundle arrangement that was selected (Fig. 7-15). Note that the AM and PL bundle divisions differ from the prior study. The femoral attachment was oriented at 37° to the long axis of the femur. The authors reported that the AM bundle extended to the posterior proximal limit of the femoral notch between the 10:30 and the 11:30 positions. The PL bundle was located between the 9:00 and the 10:30 positions. The authors reported that a 6-mm graft tunnel had the best fit if the AM bundle was located at 11 o’clock, 6 mm from the posterior outlet, and the PL bundle was located at 10 o’clock, 9 mm from the posterior outlet. The authors noted that other studies had different recommendations for the placement of two femoral tunnels in the double-bundle technique.

FIGURE 7-14 A, Measurement lines drawn parallel to the femoral shaft at the o’clock positions. B, Measurement lines drawn parallel to the femoral notch roof from the o’clock positions. C, The posterior condyle circle reference system. D, Measurement grid for describing the position of the centres of the two functional ACL bundle attachments, with numbered zones.

(A–D, From Edwards, A.; Bull, A. M.; Amis, A. A.: The attachments of the anteromedial and posterolateral fibre bundles of the anterior cruciate ligament: part 2: femoral attachment. Knee Surg Sports Traumatol Arthrosc online, 2007.)

FIGURE 7-15 ACL attachment outlines on the femur and the corresponding outlines on the tibia; femur above tibia in each case; all shown for the right knee.

(From Edwards, A.; Bull, A. M.; Amis, A. A.: The attachments of the anteromedial and posterolateral fibre bundles of the anterior cruciate ligament: part 2: femoral attachment. Knee Surg Sports Traumatol Arthrosc online, 2007.)

Rue and associates¹⁵⁹ in a cadaveric study used a transtibial-drilled femoral tunnel, placed at the 10:30 position, and determined the location of a single-graft femoral tunnel in relation to the AM and PL bundles. The authors placed the guide pin for the tibial tunnel approximately 7 mm anterior to the PCL, which would represent a posterior one third tibial attachment. The authors reported the transtibial drilling of the femoral tunnel resulted in the footprint of the AM occupying an average of 32% (range, 3%–49%) of the area of the tunnel, and the footprint of the PL bundle occupying an average of 26% (range, 7%–41%). In addition, the remainder of the area of the 10-mm tunnel did not overlap the ACL footprint. The wide ranges reported in this study for the location of the femoral tunnel in terms of the native ACL femoral attachment highlight the problems of using the tibial tunnel to drill the femoral tunnel.

Heming and colleagues⁷¹ reported the ACL tibial and femoral footprints in 12 cadaveric knees (Fig. 7-16). Note in Figure 7-16C, the orientation of the clock face places the 9 to 3 o’clock horizontal line at the base of the femoral condyles and not within the center of the notch, which is typically used by other authors. A guide pin placed between the ACL anatomic femoral and tibial attachment centers (as in a transtibial drilling technique) was only possible if the tibial tunnel started in a medial position close to the joint line that would be too short to be functional for ACL grafts. The study concluded that transtibial drilling techniques resulted in a more vertical graft orientation.

FIGURE 7-16 A, Right knee ACL tibial insertion. Measurements are the mean for the anterior-posterior length, medial-lateral width 10 mm from the posterior margin, distance from the PCL notch, and distance to the medial plateau articular cartilage. B, Right knee ACL femoral insertion. Measurements are the mean for the length, width 10 mm from the proximal margin, distance to the articular cartilage, and angle to the long axis of the femur in the sagittal plane. C, Right knee ACL femoral insertion in the coronal plane with the knee flexed 90°. The ACL insertion spanned the clock face from 10:14 to 11:23. The vertical 12 o’clock axis was perpendicular to the 3- to 9-o’clock axis drawn between the posterior femoral condyles. The vertical axis extended superiorly from a point midway between the walls of the notch to the apex of the notch.

(A–C, From Heming, J. F.; Rand, J.; Steiner, M. E.: Anatomical limitations of transtibial drilling in anterior cruciate ligament reconstruction. Am J Sports Med 35:1708–1715, 2007.)

ACL Function Defined by the Role of AM and PL Divisions

Sakane and coworkers,¹⁶⁰ in one of the first cadaveric robotic studies, reported the PL bundle provided the primary restraint to anterior tibial translation at low flexion angles. Increasing forces were reported in the AM bundle with knee flexion; these remained lower than the calculated in situ forces of the PL bundle.

The role of the ACL bundles in restraining rotational motions was examined by Zantop and associates²⁰³ in a robotic study. A 134-N anterior tibial load and a combined 10-Nm valgus and 4-Nm internal tibial torque were applied to cadaveric knees. Sectioning the PL bundle at 30° of flexion resulted in an approximately 7-mm increase in anterior tibial translation, whereas sectioning the AM bundle produced at 60° an approximately 9-mm increase in anterior translation. Similar data were reported at low flexion angles for the combined rotational loads. These data imply a near-absence of function of the remaining “intact” bundle. In contrast, Markolf and colleagues,⁹⁷ in a cadaveric study, reported that cutting the PL bundle resulted in an increase of only 1.1 mm at 10° flexion and 0.5 mm at 30° flexion. These authors questioned the need to reconstruct the PL bundle for restoration of normal ACL laxity.

Gabriel and coworkers,⁵⁵ in a robotic cadaveric experiment, removed all of the soft tissues to produce a femur-ACL-tibia specimen. For anterior tibial loading (Fig. 7-17), the AM bundle was reported to be nearly equal to the PL bundle at 15° of flexion, with increasing AM forces with knee flexion. Under the rotation loads of valgus and internal tibial rotation, the forces in the AM bundle exceeded those of the PL bundle (Fig. 7-18).

FIGURE 7-17 In situ force in the intact ACL and its AM and PL bundles in response to 134 N anterior tibial load.

(From Gabriel, M. T.; Wong, E. K.; Woo, S. L.; et al.: Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loads. J Orthop Res 22:85–89, 2004; reprinted with permission of Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc.)

FIGURE 7-18 In situ force in the intact ACL and its AM and PL bundles in response to combined rotatory load (10 Nm valgus and 5 Nm internal tibial torque).

(From Gabriel, M. T.; Wong, E. K.; Woo, S. L.; et al.: Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loads. J Orthop Res 22:85–89, 2004; reprinted with permission of Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc.)

Li and associates⁹⁰ used MRI and fluroscopic images of subjects performing a lunge to create three-dimensional models in which the AM and PL ACL attachments were outlined. The study reported that the AM and PL bundles reached their maximum elongation between full extension and 30° of flexion and did not demonstrate a reciprocal behavior with knee flexion-extension.

Giron and colleagues,⁶¹ in a cadaveric experiment, determined that a “deep” (proximal) femoral tunnel position could be achieved with either one of three techniques (double incision, transtibial, or anteromedial portal). However, Arnold and coworkers⁹ showed in cadaveric experiments that the ACL is entirely attached to the lateral femoral wall and that this attachment position was not able to be accessed through a transtibial tunnel (40% AP tibial measurement). The transtibial tunnel method resulted in the guide pin and drill hole placed at the junction of the proximal ACL attachment and femoral roof (Fig. 7-19).

FIGURE 7-19 Notch view, summary guiding pinholes; knees no. 1–5, schematic drawing.

(From Arnold, M. P.; Kooloos, J.; van Kampen, A.: Single-incision technique misses the anatomical femoral anterior cruciate ligament insertion: a cadaver study. Knee Surg Sports Traumatol Arthrosc 9:194–199, 2001; with kind permission of Springer Science+Business Media.)

Mae and associates,⁹⁶ in a cadaveric knee study, used a robotic simulator to study the effect of single- versus two-femoral tunnel ACL graft reconstruction. A single tibial tunnel was placed in the center of the ACL tibial attachment. The locations of the single and two tunnels were described at the 1:00 and 2:30 positions. The data for AP laxity and AP in situ graft forces at 44 N graft pretension showed little difference between the single- and the double-bundle grafts, both of which produced a mild to moderate overconstraint that limited anterior tibial translation. The study reported on the load-sharing between the normal ACL bundles (Fig. 7-20), which demonstrated that the PL bundle functioned more at low flexion angles, equal to the AM bundle at 10° of flexion, with a further increase in AM bundle function with increasing knee flexion. A study of load-sharing between the two bundles of a simulated pivot shift type of loading was not performed.

FIGURE 7-20 Graph shows force sharing between the normal ACL bundles under 100 N of anterior load.

(From Mae, T.; Shino, K.; Miyama, T.; et al.: Single- versus two-femoral socket anterior cruciate ligament reconstruction technique: biomechanical analysis using a robotic simulator. Arthroscopy 17:708–716, 2001.)

Yagi and colleagues¹⁹⁹ compared single- and double-bundle ACL hamstring reconstructions. A double-looped single-bundle hamstring graft was placed at approximately the 11 o’clock position and tensioned to 44 N, whereas each bundle of the double-bundle graft was tensioned to 44 N. The double-bundle graft had a total of 88 N of tension versus 44 N for the single-graft reconstruction. In response to a 134-N anterior load at 30° of flexion, the data showed an unexplained residual anterior tibial translation (intact, 6.4 mm ± 2.4 mm: single-bundle, 10.2 ± 2.5 mm), which would not be anticipated from a single graft in terms of resisting translation. The finding of a lax single graft most likely explains the reported decreased ability of the single graft to resist the combined rotation-translation motions.

Petersen and coworkers¹⁴⁶ concluded that the location of the ACL double-bundle grafts in clinical studies varied markedly at both the femoral and the tibial sites. In a cadaveric study, Petersen and coworkers¹⁴⁶ found that a two-tunnel tibial technique provided an advantage in resisting combined rotatory loads, simulating the pivot shift (anterior tibial translation, 7.5 mm vs. 9.5 mm, 30° flexion, 5 Nm internal rotation, 10 Nm valgus torque). Of note, the single tibial tunnel and graft was placed 7 to 8 mm anterior to the PCL; the authors stated that this was a position recommended by some surgeons.^74,107 As previously discussed, the posterior tibial tunnel position results in a more vertical ACL graft, with portions of the graft possibly even posterior to the native ACL tibial attachment. The addition of a second graft placed in a more anterior tibial position within the ACL footprint would be expected to provide better resistance to the loading conditions. Although the data do not provide evidence for a double-bundle ACL procedure, it does provide evidence to avoid placement of a single ACL graft in the posterior one third of the ACL tibial attachment.

Yamamoto and associates²⁰⁰ conducted a cadaveric robotic study that compared a single ACL graft placed in the 10:00 position on the lateral wall with an anatomic double-bundle reconstruction. This is one of the few published studies in which a single-graft lateral wall placement was used, avoiding a more proximal graft placement. Similar loading conditions were used as in the other robotic studies (anterior tibial load 134 N, combined rotatory load 10 Nm valgus and 5 Nm internal tibial torque). There was no statistical difference in the anterior tibial translation or in situ force at 30° knee flexion between the intact ACL, the single bundle, or the anatomic double-bundle reconstructions. Under the combined rotatory loading conditions, there were no differences in anterior tibial translation, internal tibial rotation, and ACL in situ graft forces, which is in direct contrast to other robotic experiments.

Markolf and colleagues⁹⁸ measured in cadaver knees a simulated pivot shift in the intact knee and then after single-bundle and double-bundle ACL reconstruction. The single-bundle reconstruction (placed at the anatomic AM bundle site) restored mean tibial rotations and lateral plateau displacements to levels similar to those of the intact knee, whereas the double-bundle reconstructions reduced coupled rotations and displacements to levels less than those in the intact knee. The authors concluded that the overconstraint induced by the double-bundle reconstructions has unknown clinical consequences and that the need for the added complexity of this procedure is questionable.

Cuomo and coworkers³⁸ reported on the effects of tensioning single- and double-bundle ACL reconstructions in cadaveric knees instrumented with a six-degrees-of-freedom system under defined loading conditions (anterior translation, 90 N; 5 Nm internal rotation torque). Different flexion positions were used for tensioning each of the grafts in the double-bundle construct. The single graft was tensioned at 20° knee flexion. All grafts had sufficient tension applied to restore the intact knee laxity (translation). Tensioning each of the grafts individually (AM bundle at 90°, PL bundle at 20°, varying which was tensioned first) resulted in overconstraining AP translation. In contrast, tensioning both the AM and the PL grafts simultaneously at 20° provided the best match for the intact knee AP translation throughout knee flexion. The data show the difficulty in tensioning two ACL grafts at the time of surgery in terms of matching the intact ACL load-sharing between fibers. With anterior loading, both the AM and the PL fibers participate in load-sharing, but at different percentages, as already discussed. For single-bundle ACL grafts placed within the center of the femoral and tibial attachments, higher overall graft tension occurred under anterior loading compared with the two graft bundles tensioned at 20° flexion. Importantly, the data show that tensioning of the AM and PL grafts under low tensions (20 N) provided the best results. The single graft required 38 ± 27 N to restore the native knee laxity.

Scopp and associates,¹⁶⁴ in cadaveric experiments, reported that a more oblique femoral tunnel placement (60° from vertical) was more effective in resisting internal rotational torques (difference 4.4°, 6.5 Nm) than a “standard” tunnel placement (30° from vertical). The femoral tunnel was drilled using a transtibial technique and, most likely, a posterior tibial tunnel placement. Anterior tibial translation values were not restored to normal (increased 2.5 and 2.2 mm, standard and oblique femoral tunnels).

Simmons and colleagues¹⁷² in cadaver experiments showed the deleterious effects of a more vertical tibial tunnel (70°, 80°) with impingement against the PCL and higher graft tension. A more oblique tibial tunnel and femoral tunnel in the 60° coronal plane did not impinge against the PCL. The study recommended a posterior tibial tunnel placement and more proximal ACL femoral attachment with use of a transtibial drilling technique, again showing the predominance of studies in the literature in which a more vertical graft orientation results.

Arnold and coworkers¹⁰ showed in cadavers that the passive ACL tension flexion-extension tension curve was not reproduced by femoral tunnels placed at the 10 and 11 o’clock position, but was reproduced by grafts in the 9 o’clock–positioned tunnels. A posterior tibial tunnel was used in this experiment.

In summary, a majority of in vitro robotic studies compare a double-bundle graft construct to a hybrid proximal femoral and posterior tibial orientation of a more vertical single-bundle graft construct and not a centrally placed femoral and tibial graft construct. Therefore, the published data apply specifically to this type of single-graft construct and show as expected that a vertical single graft is not positioned to resist rotational loading. It may be concluded that there are sufficient experimental data to recommend that this hybrid graft orientation be avoided in clinical practice.

There are incomplete in vitro data on the comparison of a anatomic single-graft construct (within central tibial and femoral tunnels) with a double-bundle construct.⁹⁴ There are also incomplete experimental data on the function of individual regions of ACL fibers in resisting coupled motions as occurs in the pivot shift phenomena, which is an important area for future study (Fig. 7-21). Other biomechanical studies reviewed show that a single ACL graft placed within the anatomic femoral and tibial attachments (avoiding a high femoral and posterior tibial position) restores rotatory stability and question the need for a double-bundle procedure.⁹⁸

FIGURE 7-21 The ACL attachment on the tibia is outlined, along with an approximated center of tibial rotation. After ACL sectioning, the center of tibial rotation shifts medially, restrained in part by the medial ligament structures. The ACL tibial fibers are divided into AM and PL bundles. It should be noted that the AM bundle is anatomically positioned to limit the coupled motions of internal tibial rotation and anterior translation under loading conditions; this effect has been frequently underestimated in biomechanical studies.

One theoretical advantage of a double-graft construct tensioned appropriately is that there is initially less graft tension in each of the graft strands compared with the overall tension in a single graft. Stated differently, a single graft will always exhibit much higher graft tension to resist anterior loading than two graft arms in which load-sharing occurs. There is also the theoretical advantage of tensioning the two graft strands at different knee flexion positions to exhibit a different percentage of sharing of the overall tension than a single graft. From an experimental standpoint, either a single-graft or a double-graft construct can be tensioned to restore normal motion limits; however, this may occur at the expense of high graft tensions, particularly in a single-graft construct. Thus, the advantage of a double-graft construct (either ACL or PCL) is to restore normal knee motion limits under the lowest graft tensile loads, which is advantageous during the graft healing and remodeling. A graft under lower loads has the theoretical advantage of less risk in stretching out with return of the abnormal motion limits. In addition, an ACL or a PCL graft under higher tension under cyclical loading conditions is at high risk of graft stretching and failure.¹⁶⁷ Again, it should be noted that either one or two ACL grafts do not restore native ACL fiber length-tension properties.

Clinical Measurement of ACL Graft Function during and after ACL Surgery

The assessment of ACL graft function must take into account the restoration of the normal coupled motion limits of anterior tibial translation and internal tibial rotation. During KT-2000 testing, only anterior tibial translation is assessed. If the knee joint has a 3-mm or lower increase in anterior tibial translation over the opposite knee, it can be assumed that there is not a positive pivot shift because this amount of constraint to anterior tibial translation also limits internal rotation. Conversely, if greater than 5 mm of increased anterior tibial translation exists, there is usually an abnormal increase in internal tibial rotation that results in a positive pivot shift test and patient complaints of giving-way. The problem is in knees that demonstrate 3 to 5 mm of increased anterior tibial translation, which may represent 20% to 30% of patients in clinical investigations,^{2,7,143,165,166} especially when allografts are used.¹³¹ This mild to moderate increase in anterior tibial translation results in a mildly positive Lachman test with a hard endpoint. However, along with an increase in internal tibial rotation, these knees may demonstrate a positive pivot shift and giving-way symptoms. Because the pivot shift test is highly subjective and variable between examiners (see Chapter 3, The Scientific Basis for Examination and Classification of Knee Ligament Injuries), an author may report a successful result based on the KT-2000 (anterior tibial translation) or a pivot shift test, whereas another examiner may grade the knee as a failure based on the method by which the pivot shift test is performed. There is a pressing need for clinical examination tools that incorporate tibial translations and rotations and the resultant subluxations in millimeters of the medial and lateral tibiofemoral compartments under defined loading conditions.

Bull and associates²⁵ were among the first authors to report intraoperative measurement of tibial translations and rotations using a three-dimensional motion analysis system. Robinson and colleagues¹⁵⁶ performed an ACL double-bundle reconstruction using computerized navigation techniques in 22 patients. Both the AM and the PL bundles contributed to resisting anterior tibial translation during the pivot shift tests. However, the PL bundle was more important than the AM bundle in controlling abnormal tibial rotation. It is probable that the AM bundle was placed in a more vertical proximal position adjacent to the intercondylar roof. Computerized navigation techniques allow for a highly accurate measurement of knee translations and rotations that may lead to the most objective means to measure knee kinematics during surgery. However, the exact location of ACL grafts and the loads applied by the examiner are variables still to be determined.

In a frequently quoted study, Tashman and coworkers¹⁷⁹ devised a unique methodology of dynamic in vivo measurements of patients after ACL reconstruction on a treadmill while running downhill, employing a biplanar radiographic system to measure tibiofemoral displacements. The reconstructed knees showed an increase in mean values of external tibial rotation (3.8° ± 2.3°) and adduction (2.8° ± 1.6°). The effect of these small differences from a clinical standpoint is unknown and future studies are required that involve more dynamic rotational movements in comparison with straight-ahead running to measure the rotational kinematics of the knee joint. The specific ACL graft femoral and tibial tunnel placement was not identified in this study.

Ristanis and associates¹⁵⁵ assessed 11 patients after a bone–patellar tendon–bone (B-PT-B) reconstruction using kinematic data from a six-camera optoelectronic system obtained during a jump landing and pivoting maneuver. The ACL reconstruction did not restore tibial rotation to normal values of the opposite uninvolved extremity or controls. The femoral tunnel was placed through an AM approach with the knee joint flexed to 120° to achieve a 10 to 11 o’clock lateral wall position. The tibial tunnel was placed into the center of the ACL footprint. The authors noted the limitation of the study in the movement of skin markers accurately representing true tibiofemoral joint rotations.

Monaco and colleagues¹⁰⁶ in patients undergoing ACL reconstruction evaluated the effect of a single-bundle reconstruction with an extra-articular procedure to a double-bundle ACL reconstruction. Computerized navigation instrumentation was used in the operating room before and after the ACL procedures. The addition of the PL bundle after the AM bundle did not have an effect in reducing AP translation or the limit of internal tibial rotation, and there were no significant differences between the single- and the double-bundle reconstructions. The extra-articular reconstruction significantly reduced the internal tibial rotation limit, as would be expected. The tibial placement of the graft was performed with the guide pin 7 mm anterior to the PCL insertion into the posterior ACL attachment. The authors did not determine the effect of either graft configuration on the coupled motions of the pivot shift test but only on the limit of internal tibial rotation alone.

The authors’ conclusions of single-graft versus double-bundle graft ACL studies are summarized in Table 7-3. The hypothesis presented is that an ideally placed single-graft construct (avoiding a vertical graft orientation) provides control of the abnormal pivot shift motions, avoiding the necessity and added complexity of a double-bundle graft reconstruction.

TABLE 7-3 Authors’ Conclusions of Single- versus Double-Bundle Anterior Cruciate Ligament Reconstructions

Recommended Tibial and Femoral ACL Graft Locations

Given the variation in ACL anatomic shapes between specimens, it is important during surgery to outline the individual size and shape of the ACL attachment for each knee. This can be done in a primary ACL reconstruction, but usually not in revisions. The cadaveric studies provide important anatomic reference landmarks. Because of the variation in ACL attachment shapes, it would be expected that there would exist variation between surgeons on the locations chosen for both single- and double-bundle ACL graft locations. Newer computer navigation techniques have been studied to aid in the placement of ACL grafts; however, it is unknown at present what anatomic points to select for graft tunnels that would correlate with clinical stability results.

The important landmarks for the ACL tibial attachments are the medial tibial spine, posterior interspinous ridge (RER) of the proximal PCL fossa, and the attachment of the lateral meniscus. The PCL is a poor soft tissue landmark for the posterior extent of the native ACL attachment. It should be noted that some authors⁷⁵ have advocated a guide pin and tibial tunnel placement 6 to 8 mm from the PCL, which would place the tibial tunnel in the posterior portion of the ACL. In some knees, the tibial tunnel would be posterior to the native ACL attachment and just a few millimeters from the RER or interspinous ridge. This posterior tibial tunnel produces a near-vertical ACL graft that would not be expected to resist rotational loads in obliterating the pivot shift phenomena, as already discussed.

The ACL tibial attachment location recommended by the authors for a single graft is directly adjacent to the lateral meniscus anterior horn attachment as shown in Figure 7-22. The ACL attachment can be easily mapped at surgery based on the anatomic references provided. In some knees, the anterior extent of the ACL attachment may be obscured by soft tissues, and in these cases, the RER or posterior interspinous ridge of the PCL fossa is an important landmark. The center of the ACL will be 16 to 20 mm anterior to the RER or posterior interspinous ridge. The guide pin is most ideally placed eccentric and 2 to 3 mm anterior and medial to the true ACL center, because the ACL graft displaces to the posterior and lateral aspect of the tibial tunnel.³¹ The eccentric tunnel places the majority of the graft within the central tibial attachment and avoids the posterior attachment location. It is important that an impingement of the graft with the anterior intercondylar notch does not occur because the circular graft may occupy a portion of the native flattened ACL tibial attachment. A limited anterior notchplasty is often required. In many ACL revision knees, the bony ridge posterior to the ACL attachment (“no-man’s land”; Fig. 7-23) has been disrupted by a prior graft tunnel that extends 1 to 2 mm from the RER and requires a bone graft prior to the revision procedure. It is important that during the ACL tibial tunnel preparation (primary or revision surgery), the tibial drill not inadvertently penetrate into or beyond the posterior one third ACL attachment and adjacent posterior interspinous ridge to avoid a vertical graft orientation.

FIGURE 7-22 A, ACL tibial attachment is outlined along with the shaded region, indicating a central placement of an ACL graft and tibial tunnel. B, Arthroscopic ACL attachment anterior to the posterior edge of the lateral meniscus. C, Center of ACL attachment is marked and is anterior to the lateral meniscus posterior edge. D, Placement of central guide pin for single tunnel ACL reconstruction. FC, femoral condyle.

FIGURE 7-23 A, ACL femoral attachment shows the entire attachment on lateral wall of notch. B, Three points identified in proximal, middle, and distal portions of ACL attachment. C, Transtibial guide pin placement reaches only the proximal one third of ACL attachment with a portion of the femoral tunnel extending onto the notch roof when a central ACL tibial tunnel is used. D, ACL central point is reached with knee hyperflexion and AM portal or with a two-incision rear-entry technique. E, Final graft appearance on the lateral wall.

Important landmarks for the femoral attachment are the posterior articular cartilage, Blumenstaat’s line, and identification of the ACL attachment on the lateral femoral wall of the notch (in the regions outlined on the grid systems). Again, the emphasis is made that no ACL fibers extend to the intercondylar roof; all of the fibers are on the lateral wall.

For single grafts, the authors recommend a central anatomic ACL placement with the femoral guide pin 2 to 3 mm above the midpoint of the proximal-to-distal length of the ACL attachment and 8 mm from the posterior articular cartilage edge (see Fig. 7-23). A key is to define the ACL attachment at 20° to 30° of flexion with the arthroscope in the AM portal. After the joint is marked, the knee can be placed in 120° of flexion if an endoscopic technique is selected. A 9- to 10-mm-diameter tunnel occupies the central ACL attachment, leaving only the most proximal and distal few millimeters of the attachment not occupied by a graft. It is important that the ACL tunnel not be too distal because this shortens the intra-articular graft tibiofemoral length. The location for a single-tunnel ACL reconstruction is more distal than recommendations for a “one o’clock” tunnel that replaces only the proximal portion of the ACL femoral attachment. However, it has not been determined in clinical studies whether a difference exists between the one o’clock and the two o’clock femoral graft placement sites.

In Figure 7-24A, the hybrid graft position of a proximal femoral and posterior tibial position is shown, which the authors do not recommend. The preferred central anatomic tibial is presented in Figure 7-24B and femoral position is presented in Figure 7-24C. The placement of a double-bundle ACL reconstruction is shown in Figure 7-24D.

FIGURE 7-24 Summary of different femoral and tibial graft positions that are possible using AM and PL bundle terminology. A, Classic AM femur to PL tibia results in a vertical graft with a tibial tunnel placed too far posteriorly. B, A more central tibial tunnel is advantageous for control of rotational stability. C, The ideal central femoral-tibial tunnel locations for a single graft reconstruction. D, The placement of a two-bundle ACL reconstruction.

Graft Selection

The principles of ACL surgery are summarized in Table 7-4. Currently, there is no standard graft choice for ACL reconstruction. Autograft tissue sources include B-PT-B, quadriceps tendon–patellar bone (QT-PB), and semitendinosus-gracilis (STG) tendons. The authors prefer B-PT-B autogenous grafts in athletes, a recommendation supported by several long-term studies^{42,69,72,89,197} and in recent studies showing a higher rate of ACL primary reconstruction failure after allografts compared with allografts, especially in younger patients.^83,95 A B-PT-B autograft is not recommended if there is associated patellofemoral arthritis (Grade 2B classification; see Chapter 47, Articular Cartilage Rating Systems), anterior knee pain, or a history of patellar subluxation or dislocation. A B-PT-B autograft is not performed when patient issues suggest a decreased ability to follow the more involved rehabilitation program and initial pain related to this graft. In recreational athletes and more sedentary patients, a four-strand STG autograft is recommended. Newer fixation methods have increased the success rate, and the rehabilitation postoperatively is easier on the patient.

TABLE 7-4 Principles of Anterior Cruciate Ligament Surgery

In revision knees, if the ipsilateral patellar tendon was previously harvested, the contralateral patellar tendon is a valid graft source. Ipsilateral patellar tendon graft reharvest is not recommended owing to persistent changes on MRI and graft morphology reported in these knees 7 to 10 years postoperatively.^{20,85,88,91,93} A second option is a QT-PB graft taken from the same or the opposite knee, with grafting of any residual patellar bone defect. The quadriceps tendon has the greatest cross-sectional area (100 mm²) and is ideal in revision knees if the prior tunnels are in the desired anatomic ACL site but are slightly expanded. If autograft tissues are not available or the patient refuses a contralateral knee harvest, then a B-PT-B or Achilles tendon–bone allograft is recommended. A posterior or anterior tibialis allograft is not recommended.¹⁷³ It is desirable to have one portion of the graft with a bone plug for increased rate of graft healing in one of the tunnels. The authors use allografts that have not undergone irradiation sterilization.

Patient Setup and Positioning

The patient is instructed to use a soap scrub of the operative limb (“toes to groin”) the evening before and morning of surgery. Lower extremity hair is removed by clippers, not a shaver. Antibiotic infusion is begun 1 hour prior to surgery. A nonsteroidal anti-inflammatory drug (NSAID) is given to the patient with a sip of water upon arising the morning of surgery (which is continued until the 5th postoperative day unless there are specific contraindications to the medicine). The use of an NSAID and a postoperative, firm double-cotton, double-Ace compression dressing for 72 hours (cotton, Ace, cotton, Ace layered dressing) has proved very effective in diminishing soft tissue swelling and is used in all knee surgery cases. In complex multiligament surgery, the antibiotic is repeated at 4 hours and continued for 24 hours. A urinary indwelling catheter is not used unless there are specific indications. The patient’s urinary output and total fluids are carefully monitored during the procedure and in the recovery room. The knee skin area is initialized by both the patient and the surgeon before entering the operating room, with a nurse observing the procedure. The identification process is repeated with all operative personnel with a “time out” before surgery to verify the knee undergoing surgery, procedure, allergies, antibiotic infusion, and special precautions that apply. All personnel provide verbal agreement.

A single femoral nerve block is administered preoperatively or in the recovery room, which markedly decreases the need for analgesic medication. The patient is instructed to use crutches with decreased weight-bearing for 24 hours owing to decreased quadriceps function. Bupivacaine (Marcaine) or lidocaine installation is not recommended because high local doses may alter chondrocyte function and viability.^68,84,184 A fluid inflow–pressure-regulated pump is recommended over gravity infusion because hemostasis can be controlled and tourniquet use avoided in most cases. An electrocautery device is always available to control bleeding points.

With the patient in a supine position on the operative table and all extremities well padded, a tourniquet is placed on the middle to proximal thigh (Fig. 7-25A). A leg holder is used for the initial arthroscopic examination to provide for maximum opening of the medial and lateral tibiofemoral compartments during the gap tests and to provide necessary distraction for a meniscus repair or partial resection. A leg holder provides better visualization of the posterior meniscus regions over a lateral post. A low-profile leg holder is used, which is pressed into the operative bed mattress to decrease posterior thigh pressure; this is removed after the initial diagnostic arthroscopic procedure. The knee portion of the bed is flexed 60° to 90° and the bed midportion is retroflexed 15° to allow flexion of the hips to relieve undue tension on the femoral neurovascular structures. The uninvolved extremity is placed in a well-cushioned padded holder. An alternative approach described in the literature is to place the uninvolved extremity in an abducted and flexed position with a thigh and leg holder.

FIGURE 7-25 Initial operating room setup and patient positioning. A, Use of a thigh holder to achieve medial/lateral joint opening, particularly for meniscus repairs, that is removed for the ACL procedure. B, Patient in the supine position with a leg holder used to allow selected knee flexion positions, particularly hyperflexed position with AM portal pin placement for femoral tunnels.

After the arthroscopic procedures and removal of the leg holder, two positions may be used for the lower limb. The first is to adjust the operative bed to allow 90° of knee flexion. The knee can be flexed to 120° or more during the procedure, if necessary, by having the operative assistant flex the hip joint and knee joint. The second option is to position the operative bed flat and use an Alverado foot and leg holder or sandbag taped to the table to allow the knee joint to be flexed to the desired position (see Fig. 7-25B). The senior author prefers the second position when any associated medial, lateral, or PCL procedures are performed. The second position allows the surgical assistants to easily view and assist the associated ligament reconstructive procedures. With concurrent medial or lateral reconstructions, the surgical procedure is performed at 20° to 30° of flexion with a roll placed beneath the thigh. The knee joint can also be brought to full extension to determine that posterior capsular reconstructions do not constrain full knee extension.

Graft Harvest: B-PT-B Autograft

A tourniquet is inflated to 275 mm of pressure. This is usually the only time the tourniquet is inflated in the reconstructive procedure. A 3- to 4-cm vertical medial incision is made just adjacent to the medial border of the patella tendon, avoiding the tibial tubercle (Fig. 7-26). The incision is located just medial to the inferior pole of the patella. A proximal skin incision over the patella is not required because the patella is easily displaced distally during removal of the patella bone plug.

FIGURE 7-26 The technique the author recommends for harvest of a bone–patellar tendon–bone (B-PT-B) autograft. A, A 3- to 4-cm skin incision, just medial to the patellar tendon, is made to avoid the bony prominence of the patella and tibial tubercle. The index finger points to the planned tibial tunnel, which can be reached through this cosmetic incision. B, Mobilization of subcutaneous tissues to allow the cosmetically placed incision to be moved in a proximal-distal and medial fashion. Infrapatellar nerves when present are protected. C, A ruler measures the length of the patellar tendon and a 10-mm wide patellar tendon graft is marked by two or three ink dots. D, The patella is displaced distally and the patellar bone block removed. Note that the saw has a tape marking a 9-mm depth to prevent from cutting too deep into the patella. The saw is angled 10°–15° to produce a trapezoidal bone block. The saw carefully cuts the medial and lateral borders, making sure the bone beneath the tendon insertion has been cut to prevent a fracture of the graft. A similar technique is used for the tibial tubercle. E, Appearance of the graft after harvest. F, Preparation of the graft. Two nonabsorbable No. 2 sutures are placed in a distal drill hole in each bone plug. The bone tendon junction is marked. The graft is wrapped in a blood-soaked sponge with the goal of maintaining viability of some tendon cells. G, Theskin incision is displaced distally to reach the desired position for the coronal tibial tunnel, as described in the text. H, The core reamer is placed in the tibial tunnel for the graft harvest. I, The bone plug removed by the core reamer.

A cosmetic approach is used in which the plane beneath the subcutaneous tissues is dissected to allow for a limited skin incision. The skin incision is displaced proximally and distally as required for the graft harvest. Four vein retractors are placed into the proximal, distal, medial, and lateral aspects of the skin incision to allow for a rectangular skin opening for the graft harvest. A branch of the infrapatellar nerve may cross the middle of the patellar tendon and is preserved. The patient is advised preoperatively that there will be an area of decreased skin sensation just lateral to the patellar tendon because superficial nerve branches may be incised as a part of the procedure. An alternative technique is to use a proximal and distal skin incision, avoiding a vertical skin incision, which has less chance of a sensory skin loss but a greater chance of skin hypertrophic scar formation.

The retinaculum in the middle of the patellar tendon is incised and the dissection limited only to the midportion of the patellar tendon. The parapatellar tissues and blood supply to the tendon are not disturbed. The tendon should not be dissected to its edges because this damages the blood supply, particularly to the major vein and artery on the medial side of the tendon. In some knees, a branch of the infrapatellar nerve will cross the middle of the patella tendon and should be preserved. In these knees, the nerve provides a large area of cutaneous sensation over the lateral aspect of the knee. It should be noted that up to approximately one half of patients will later have an approximately 2-cm area of numbness just lateral to the patellar tendon from incision of small cutaneous nerve branches that are not visible during the procedure. Patients are warned of this potential loss of sensation preoperatively. The patellar retinaculum is carefully incised and reflected medially and laterally only for the width of the graft to be removed. The retinaculum is protected to allow for closure over the bone-grafted patellar defect. A similar procedure is used at the tibial tuberosity.

It is useful to have a precut 10-mm and 22-mm paper ruler held on a hemostat to place over the tendon and bone harvest sites to allow fine marks to be placed on the tissues to define graft dimensions.

The patellar tendon is incised in the midportion to the appropriate size, 9 to 10 mm. The patella is displaced distally into the wound using a forked retractor placed at the superior patellar margin. A powered handheld saw with a thin-width blade is marked with a SteriStrip 9 to 10 mm from the tip to prevent too deep a cut, which would weaken the patella. A trapezoidal bone block graft from the patella is removed by angling the fine saw 15° at each side of the cut. The bone cut is meticulous and proximally “cross-hatched,” as a deep cut is avoided. The bone cut extends to the inferior pole, and care is taken to protect the insertion site of the patellar tendon. A 4-mm osteotome gently removes the patella bone block without wedging the sidewalls, which could induce a lateral fracture. A similar procedure is followed in the harvest of the tibial bone block.

The tourniquet is deflated, and a cotton sponge is placed in the wound. The graft is later wrapped in the blood-soaked sponge, which provides protection of the graft, maintains a moist blood environment, and may allow cells to survive in the graft-remodeling process. It would be incorrect to have the graft openly exposed on the back table, which would allow drying, cell death, and possible air contamination. A second surgeon prepares the graft to decrease operative time.

The bone blocks are prepared so they will pass easily through the tunnels. The diameter of the tunnels will be configured 1 mm larger than the diameter of the bone block. The bone-tendon junction of each graft is marked for later identification. The graft preparation involves one 2-mm drill hole placed one third of the way from the end of each bone block for sutures. The end sutures allow the graft to be passed into the tunnel. A suture placed into the midportion of the graft would tilt the bone block, making passage into the tunnels difficult. The tibial portion of the graft is identified and will be later passed in a retrograde manner through the tibial tunnel into the femoral tunnel. The bone block tip is fashioned into a bullet tip configuration for tibial tunnel passage. Two No. 2 nonabsorbable Fiber-wire (Arthrex, Naples, FL) sutures are passed into the distal one third tibial bone block. The graft is wrapped in a blood-soaked sponge.

At the conclusion of the ACL reconstruction, closure of the patellar tendon graft harvest site is performed. The patella tendon is loosely approximated with 2-0 absorbable sutures. A coring reamer used for the femoral tunnel provides a large dowel of cancellous bone to completely fill the patella and tibia defects. The bone-grafted sites are smoothed to remove any pressure points. It is important to place two horizontal mattress sutures at the inferior pole of the patella and at the superior tendon attachment at the tibia to create a buttress or pocket to maintain the position of the bone graft at each site. Otherwise, the bone graft may displace and be a source of pain becaue it is located in the tendon rather than the bony defect. The patella retinaculum is carefully closed to provide a soft tissue covering over the patella defect. The retinaculum over the tibial tuberosity is not as well defined; however, the soft tissues are closed using 2-0 absorbable horizontal mattress sutures.

The meticulous technique described for the B-PT-B graft procedure is an important part of the operative procedure. The skin incision is medial to any bone prominences and does not extend over the patella. The dissection is limited entirely to that portion of the graft to be removed, protecting nerves and avoiding damage to the parapatellar vascular supply. The surgeon is seated, with the patient’s foot in the surgeon’s lap to directly visualize the wound and carefully control the saw blade. A headlight is always used to see the fine neural structures.

The use of the coring reamer (tibia or femoral tunnels) provides ample bone graft to completely fill the tibia and patella bone defects. The use of shavings or small amounts of bone obtained in the procedure is insufficient to completely fill these defects. If the tibial tuberosity defect is left partially unfilled, there will be ridges on either side of the defect that will prevent the patient from kneeling. If the defects are closed as described, kneeling with little to no discomfort is to be expected, equal to the opposite knee. In the authors’ opinion, this point has not been sufficiently stressed in the literature. A completely filled graft harvest site at the patella and tibial tubercle is required. Saving bone chips during the ACL tunnel preparation usually results in insufficient bone for both harvest sites. The added time to use the coring reamer bone-graft harvesting instruments provides the benefit of a quality bone graft for both the patellar and the tibial sites. Commercially sold bone allografts are available; however, the authors prefer to use the patient’s bone. The length of the bone block is 22 to 24 mm to facilitate passage.

Graft Harvest: QT-PB Autograft

A 5- to 6-cm longitudinal incision is made from the superior pole of the patella, extending to the midline proximally. The prepatellar retinaculum is reflected and protected for later closure over the grafted patellar defect. The quadriceps tendon and its junction with the vastus medialis obliquus and vastus lateralis obliquus (VLO) are identified. The proximal portion of the quadriceps tendon is identified and the graft harvest is carried 15 mm distal to the rectus femoris muscle-tendon attachment in order not to weaken this site. A 10-mm-wide tendon graft, through all three layers, is removed to a length of 60 to 70 cm (Fig. 7-27). The tendon attachment to the anterior superior pole of the patella is carefully identified and the synovial attachment protected. A power saw with the cutting blade marked with paper tape to a depth of 10 mm is used to cut the anterior cortex to produce a patellar bone graft 22 to 24 mm long by 9 to 10 mm wide. The bone graft is sized to 9 to 10 mm in diameter. The quadriceps tendon defect is closed with interrupted 0-Ethibond suture (Ethicon, Somerville, NJ). Two sutures of 0-nonabsorbable material are placed just proximal to the patellar bone defect to create a pocket for the bone graft obtained from the coring reamer. The core bone graft completely obliterates the patellar defect, and a meticulous closure of anterior tissues over the graft is performed, as already described.

FIGURE 7-27 A, The quadriceps tendon and vastus medialis oblique and vastus lateralis oblique muscles are identified proximally. A 9- to 10-mm wide tendon graft, through all three layers, which has a length of 80–90 cm, is removed. The graft harvest does not extend to the muscle tendon junction. A patellar bone graft is fashioned to be approximately 22–24 mm long by 9–10 mm wide by 9–10 mm in diameter. B, Usually, all three layers are sutured together at the end of the graft (2-0 nonabsorbable suture) with a running suture on both sides of the graft. C, Surgical case, initial skin incision. D, Measurement of graft width. E, Final harvest.

Graft Harvest: STG Autograft

The STG graft harvest procedure is shown in Figure 7-28. A 3- to 4-cm oblique incision is made over the palpated pes tendons. The incision is cosmetic and the plane beneath the subcutaneous tissues carefully dissected. The surgeon is seated, the bed is flexed 60°, and a headlight is routinely used. The sartorius fascia is incised directly proximal to the semitendinosus and gracilis palpated tendons over the distal superficial medial collateral ligament (SMCL) attachment. This provides a window and opening to protect the SMCL. The overlying fascia is incised proximally in the same oblique plane of the STG tendons.

FIGURE 7-28 A, A 2-cm longitudinal or oblique incision at the AM tibia region. B, An L-shaped incision at the pes tendon tibial attachment is performed and the tendon flap is reflected to identify the semitendinosus-gracilis (STG) tendon. C, Dissection of soft tissue to identify the STG and remove the gastrocnemius secondary attachment. D, “Push-pull” test to confirm that the STG tendons are free of attachments. E, Harvest of the STG using a closed-end harvester to prevent premature transection of the STG. F, Appearance of the long semitendinosus tendon obtained at harvest. G, Graft preparation with graft board. Nonabsorbable 3-mm tape at the proximal end and three 2-0 fiberwire fixation at the distal end. Running suture is used on each side of the STG graft.

It is worthwhile in the initial dissection to identify the STG tendons to protect them and not inadvertently section the tendons. This is best performed by extending the fascia, incise just above the gracilis tendon over its tibial insertion, and then at a 90° angle, lay back the insertion site distally. This allows the STG tendons to be viewed throughout their distal course to their tibial attachment. In most knees, the STG tendons are confluent and blend to make one tendinosus structure. Each tendon is identified and incised through the confluent distal tendon region. Each tendon is grasped at a 90° angle at its distal end and rolled two to three times around a straight hemostat, which allows tension to be placed on the tendon without producing damage.

The proximal extent of each tendon is palpated and superficial tissues removed, protecting the overlying sartorius fascia. The dissection plane is never carried close to the inferior sartorius or superior gracilis muscles to avoid injury to the saphenous nerve. The headlight provides excellent illumination in the proximal portion of the incision to protect any neurovascular structures. The proximal fascia about each tendon is bluntly dissected and the semitendinosus tendon attachment to the medial gastrocnemius fascia is incised. With tension on each tendon and a repetitive pulling motion, each tendon will freely displace 10 cm. It is important to determine that each tendon is completely free of tissues to allow the tendon harvester to pass freely. The closed-end graft harvester is passed along the trajectory of each tendon and each tendon is transected at 20 to 22 cm. There is a commercially available tendon harvester with a blunt tip that protects against inadvertent tendon transection and has a tendon cutter in its distal tip activated by the mechanism at the handle. The STG tendons are prepared (see Fig. 7-28). Each tendon is looped about a 3-mm tape and the tendon end sutured to itself with a No. 2 nonabsorbable suture. A third suture is added between both sutured tendon ends. A running 0-nonabsorbable suture is used to produce a tubed structure running from proximal to distal and then back to the proximal starting point. A metal graft-tensioning board (25–30 N tension) is used rather than a graft preparation board with plastic holders because the latter is difficult to sterilize to avoid a graft contamination problem. The graft is marked 25 mm from each end, wrapped in a blood-soaked sponge, and placed in a secure place on the back table.

ITB Extra-articular Tenodesis

Two clinical studies (Noyes and Barber¹¹² and Ferretti and coworkers⁴⁹) have shown statistically significant improvements in knee stability in knees with ACL revision or with gross instability and loss of secondary restraints that had an extra-articular tenodesis procedure for additional restraint of tibial internal rotation. The procedure is described here and the rationale for its use at the time of ACL reconstruction is discussed later in this chapter.

A lateral incision 8 to 10 cm in length is made at the midlateral aspect of the knee extending from Gerdy’s tubercle to the tibia proximally. The skin incision is undermined by subcutaneous dissection to increase the skin mobility and shorten the incision for cosmetic purposes. A strip of ITB is incised proximal to distal from the posterior one third of the band, which is 12 mm wide and 18 to 20 cm long with the tibial attachment intact (Fig. 7-29).

FIGURE 7-29 A, Cosmetic lateral incision is made just proximal to Gerdy’s tubercle. A 10-mm strip along the posterior one half of the iliotibial band (ITB) is harvested. The proximal skin flap is undermined to obtain a 20-mm-long graft. B, The ITB graft (10 mm wide) is dissected distally to Gerdy’s tubercle, where the tibial attachment is left intact. C, The ITB graft is looped around a guide pin placed just distal to the lateral intermuscular and proximal to the FCL attachment. The knee is flexed from 0 to 135°, neutral tibial rotation. D, The “isometric points” graft attachment sites for an extra-articular reconstruction measured by Kurosawa et al.^87a The points T1–F1 provided the least change in length with knee flexion (maximum % of strain, 11.6 ± 3.0%). The points T1–F2 offer a second choice, except that there is an increase in the percentage of strain with knee flexion compared with that at T1–F1. E, The graft is looped around a soft tissue screw and washer and both graft ends are sutured to each other and to the remaining posterior ITB. This forms a strong femoral-tibial structure that both incorporates the graft and reproduces the normal posterior ITB femoral tibial attachments. The knee is in neutral tibial rotation and graft overtensioning is avoided.

The most isometric point on the proximal and posterior aspect of the lateral femoral condyle is located (see Fig. 7-29D) and tested by using a guide pin placed at the proximal and posterior aspect of the lateral femoral condyle. The point for the femoral attachment of the ITB is usually at the anatomic ITB deep fiber insertion to the femur. This region is usually just distal to the lateral intramuscular septum and posterior and proximal to the lateral epicondyle and anterior to the gastrocnemius tubercle lateral attachment. The error is to place the ITB graft too anterior, which blocks knee flexion. The posterior placement allows the ITB graft to undergo increasing tension with knee extension. This area is curetted to remove soft tissues to allow for the ITB strip to be in contact with the overlying bone.

It is important in tensioning the ITB graft not to overconstrain the joint and block normal internal tibial rotation. After the ACL procedure is completed, the extra-articular tensioning and fixation is performed. The knee is placed at 30° of flexion and neutral rotation. The ITB strip is fixated around a soft tissue washer (Fig. 7-30) and cancellous screw and brought back upon itself to Gerdy’s tubercle. The screw is angulated anteriorly away from the ACL tunnel. The ITB strip is then sutured to itself with only mild tension applied to the ITB graft. The sutures are placed through the posterior one third of the remaining intact ITB just posterior to where the graft was harvested. This produces a strong restraint to abnormal internal tibial translation and anterior tibial translation. The knee is taken through a normal internal-external tibial rotation to ensure that there is no abnormal constraint to internal tibial rotation. The knee is flexed to 135°; usually, increasing knee flexion will provide for increased tension in the graft. There is no true isometric point for the femoral attachment of the graft for flexion-extension and tibial rotation motions. It is probable that even with precautions taken to not overconstrain knee motion, regaining full knee flexion may be more difficult when the extra-articular procedure is added.

FIGURE 7-30 A, Extra-articular ITB graft is shown looped around a soft tissue screw and anchor in a second patient. B, Final closure of the overall remaining ITB to the looped ITB graft.

The ITB is closed with absorbable sutures throughout the site where the graft was harvested. The patellar medial glide is examined at 30° knee flexion to ensure that closing the ITB does not limit the normal patellar mobility. The patella should have at least 10 mm of medial glide with a medially directed manual translation. If there is an abnormal restraint to medial patella mobility, a small lateral release is performed. The anterior fibers of the ITB, which make up the lateral retinaculum adjacent to the patella, are incised the required length to relieve the undue tension on these soft tissues due to closing the ITB defect, avoiding a release of the vastus lateralis tendon.

In the 1980s when extra-articular procedures were used frequently (instead of intra-articular ACL reconstruction), it was common for ITB reconstructive procedures to be routed underneath the FCL and then sutured to itself at Gerdy’s tubercle (Cooker-Arnold procedure). This represents a nonanatomic placement of the ITB graft that does not restore the posterior femoral-tibial ITB attachments that resist internal tibial rotation. In addition, there is concern that a soft tissue structure wrapped around the FCL could induce stretching of the FCL and allow for an increase in lateral joint opening. It is therefore recommended to secure the ITB graft to the femoral attachment discussed and to avoid looping the graft around the FCL.

ACL B-PT-B Graft Anatomic Tibial and Femoral Technique

A single-graft procedure is described in which the graft is located into the central anatomic tibial and femoral attachment locations, as already discussed. The graft placement for primary and revision knees specifically avoids the proximal ACL femoral attachment site and the posterior ACL tibial attachment site to avoid a vertical graft and allow the graft to resist rotational coupled motions in addition to anterior tibial translation (Fig. 7-31). This section describes using a single B-PT-B autograft or allograft procedure. The authors’ clinical studies support the concept of a single-graft technique for primary and revision procedures. One exception in revision knees is when a double-bundle procedure may be used in a knee in which a prior vertical ACL graft placement was performed that limits anterior tibial translation and a second coronal graft is added to provide control of tibial rotation.

FIGURE 7-31 A, A normal femoral notch is shown, which is viewed at arthroscopy by using the AM portal. 1 shows the normal space between the lateral femoral condyle and the PCL, which is occupied by the ACL. 2 shows the normal anterior notch that should not impinge on the graft. B, Revision ACL with failed ACL graft shows overgrowth of the lateral notch and notch roof, requiring a limited notchplasty. C, The lateral notch wall is visualized entirely posteriorly to the articular cartilage of the femoral condyle. D, The ACL femoral attachment is mapped out and a central small hole is made for placement of the guide pin. The resident’s ridge has been removed. The anterior notch region has not been disturbed. E, Final placement of a single-bundle graft within a central anatomic tibial and femoral placement that occupies over 75% of the attachment site.

Placement of Femoral Tunnel

As previously described, either a two-incision technique or an AM portal femoral tunnel placement with knee hyperflexion technique is used in primary and revision knees. Baer and associates¹³ recently reported in a cadaver study that at least 110° of knee flexion is required for femoral tunnel drilling through the AM portal to avoid potential injury to the peroneal nerve, the lateral condylar articular surface, the FCL, and the popliteus tendon. The use of the AM portal to place the femoral tunnel has the problems in some knees of difficulty with visualization at 100° to 120° of flexion, the potential for the drill to damage the medial femoral condyle, and a shorter femoral socket which may be a problem with a B-PT-B autograft. As with any of the ACL techniques, operator experience is necessary to achieve a successful result.

In revision knees when the femoral tunnel is close to a prior tunnel, the two-incision procedure allows the guide pin to be more accurately placed and the tunnel divergence angle to be controlled more accurately than the endoscopic procedure. Importantly, the two-incision procedure carries a smaller risk of placing a less than ideal femoral tunnel, because there have been cases in which endoscopic revision is performed and the tunnel breaks into the old tunnel, producing a more complex problem.

In the two-incision technique, there are two approaches based on the necessity to add additional suture after fixation at the femoral site. The two choices are to drill the tunnel in a retrograde or antegrade procedure. In the retrograde-drilling procedure (Fig. 7-32), a lateral incision of 2 to 3 cm in length is made at the posterior one third of the ITB. The posterior one third of the ITB is incised for 4 to 6 cm to allow exposure. The interval posterior to the vastus lateralis is entered and the muscle protected. An S retractor is placed beneath the VLO to gently lift the muscle anteriorly, avoiding entering the proximal joint capsule. The proximal edge of the lateral femoral condyle is bluntly palpated with an instrument (over-the-top location), and the goal is to locate the tunnel entrance just anterior and not distal to this point. A 15-mm periosteal incision is made and an elevator used to remove soft tissues from the site for the tunnel proximal entrance.

FIGURE 7-32 The ACL procedure for a two-incision technique. A, The anatomic landmarks. The joint line, tibial tubercle, and fibula are marked. B, The 2-cm incision that is made in the posterior one third of the ITB, as described in the text. C, Electrocoagulation of vessels. D, Commercially available drill guide. E, Placement of the guide pin.

In most chronic ACL-deficient knees and revision knees, there is an overgrowth of cartilage and spur formation in the femoral notch, requiring a notchplasty to prevent ACL graft impingement. The notchplasty rules taught by the senior author since the mid 1980s and used in all the clinical studies reported later in this chapter are described in Table 7-5. In primary ACL knees, an anterior notchplasty of a few millimeters is almost always required owing to the central placement of the tibial tunnel and ACL graft within the central tibial attachment. A lateral notchplasty is performed when required when there is insufficient width (9–10 mm) between the PCL and the lateral femoral notch wall to accommodate the ACL graft.

TABLE 7-5 Notchplasty Techniques and Rules

1 The arthroscope is placed in the AM portal with instruments passed through a central portal (patellar tendon graft site or central patellar tendon portal). A mistake is to view the lateral wall of the notch through an anterolateral (AL) portal, which provides suboptimal visualization. In the presence of a prominent lateral resident’s ridge, it is often difficult if not impossible to view or identify with accuracy the ACL femoral attachment through the AL portal. Place the knee at 20°–30° flexion to view the ACL attachment, not a high flexion angle where the ACL is in a horizontal plane. 2 Measure the clearance of the lateral notch wall to the PCL to ensure there is 9–10 mm clearance for the graft. Remove the shallow notch to obtain this clearance, starting distally and progressing proximally up to the top of the notch entrance. This ensures an adequate lateral graft notch clearance throughout knee flexion, preventing graft abrasion from a stenotic lateral notch wall. Usually only 2–3 mm of the lateral notch is removed, and aggressive resection of the lateral wall beyond this should be avoided. 3 To ensure that the height of the notch is sufficient and will not impinge, place the notchplasty burr at the central ACL tibial attachment and gently bring the knee into full hyperextension. The burr should not impinge into the anterior notch. This defines the millimeters of the anterior and lateral aspect of the notch that are removed to prevent graft impingement. Normally, this is 3–4 mm; more is removed only when there is excessive hyperextension. 4 The anterior notch is gently curved, removing an A-shaped notch if present. Before graft passage, the arthroscope is placed within the tibial tunnel “worm’s-eye view” and the knee taken to full hyperextension, observing whether any portion of the anterior notch comes into view that would require removal. This provides for direct arthroscopic confirmation that there is no ACL graft impingement, and intraoperative fluroscopy is not required. 5 Avoid use of a commercially available “tunnel smoother,” because this is too aggressive. When placed in an intra-articular location within both femoral and tibial tunnels and moved proximally and distally, this instrument may remove the anterior aspect of the femoral tunnel and posterior aspect of the tibial tunnel, producing a vertical graft. 6 Once the anterior and lateral aspects of the femoral notch (shallow portion) are prepared, it is possible to completely view the deep portion of the notch, identify the appropriate place for the ACL graft on the lateral wall, and remove an anterior bone buttress in front of the ACL attachment (resident’s ridge). Maintain the knee at 20°–30° flexion. 7 The deep roof portion of the notch represents Blumenstaat’s line, and it is important not to elevate the notch because this would change the anatomic reference points for the native femoral ACL attachment. In addition, the lateral deep wall of the notch is not changed or removed in order to maintain the native ACL attachment location for the ACL graft. Only in rare instances is there overgrowth in this region and insufficient clearance between the lateral notch and the PCL. The tissue in this region is gently removed, and the PCL synovium is protected. A sharp curet is used to remove soft tissues on the lateral wall to the femoral condyle articular cartilage edge, which is the required reference for ACL graft placement. The mistake is made not to go deep enough in the notch on the lateral wall to view “around the corner,” because sometimes the notch wall will have a gentle deep lateral slope of a few degrees.

The ACL femoral attachment is mapped based on the bony landmarks already described. The location of the guide pin for an ACL central femoral tunnel is shown in Figures 7-23, 7-24, 7-31, and 7-33. The guidewire is placed within the central ACL attachment, which is midway between the lateral notch roof and the distal articular cartilage edge (2:00 to 2:30 position), 8 mm from the posterior articular cartilage edge. Clock locations are actually an inaccurate description of the tunnel location.^45,47 With the central femoral tunnel, the posterior back wall is 3 to 4 mm thick and the graft occupies approximately two thirds to three fourths of the ACL footprint. Always preserve 4 to 5 mm of the posterior back wall of the tunnel so that the graft is not placed too far posteriorly. Grafts placed too far posteriorly will have increased tension with knee extension and may potentially block full extension. A guide pin placed 8 mm from the posterior articular cartilage at the central ACL attachment will have a 4 mm posterior back wall for a 8-mm graft. A guide pin placed 10 mm from the posterior articular cartilage at the central ACL attachment would have a 5 mm posterior back wall for a 10-mm graft. One key to define the ACL attachment is to place the knee in 20° to 30° of flexion viewed through the AM portal and map out the oval attachment and center point, measuring the distance to the posterior articular cartilage. Once the ideal center point is selected, the knee is flexed to the position desired. It is easier to mark out the ACL femoral attachment when it is viewed in a vertical plane rather than the horizontal attachment plane with knee flexion. The tunnel is drilled to the appropriate diameter for a snug graft fit in the tunnel. The edges of the tunnel are chamfered to prevent graft abrasion. The technique with a rear-entry guide drill is shown in Figure 7-33.

FIGURE 7-33 A, The rear-entry drill guide system (Smith-Nephew, Endoscopy, ACUFEX, Andover, MA). B, Central ACL femoral attachment location. C, Passage of the guide through the second incision. D, Guide pin location on the lateral femoral wall. E, Drilling of the femoral tunnel from outside-in.

Techniques Using Other Grafts

With all other grafts, the same procedure is used with the following exception. In the two-incision technique with an STG graft, a femoral post is always used with the sutures tied first at the femoral site about the post (35-mm, 4.0-mm cancellous self-cutting screw with washer). An absorbable interference screw is added if the graft tunnel interface is not tight. At the tibia, the interference screw is first placed, followed by the suture post fixation. Using the combined interference screw and suture post provides sufficient graft strength fixation for rehabilitation to proceed equal to the B-PT-B graft. An alternative technique for a four-strand STG graft using a single pin transfixation is shown later in this chapter. The bone portion of the QT-PB or Achilles allograft is usually placed into the femoral tunnel; however, the graft can be reversed with the bone plug placed into the tibial tunnel and located appropriately to make up for an enlarged tibial tunnel that requires the bone portion of the graft.

A variety of techniques for femoral fixation (Fig. 7-34) and tibial fixation (Fig. 7-35) are available, based on the preference of the surgeon. The two-incision technique is preferred over the EndoButton technique. The tibial fixation is usually the weakest, and especially in revision surgery, a suture post is added. Interference screw fixation alone of an STG or soft tissue allograft is also not recommended. A suture post is commonly required to achieve adequate fixation.

FIGURE 7-34 A variety of ACL femoral fixation techniques. The interference screw alone is not recommended because it produces the lowest graft tensile strength to pull-out.

FIGURE 7-35 Various tibial fixation techniques. An interference screw alone is not recommended.

Alternative Procedures

Outside-In “Flip-Drill” for Femoral Tunnel

An alternative approach is to use a two-incision technique with the proximal skin incision only of sufficient length to accommodate the guide pin “flip-drill” to locate and drill the tunnel from inside-out (Fig. 7-36). This procedure provides a long femoral tunnel for graft healing and incorporation. It also allows control of the guide pin for the femoral tunnel to be oriented into the most ideal position to achieve good-quality bone for interference screw fixation and, in revision knees, to avoid prior tunnels. This technique avoids the necessity for tunnel drilling in a hyperflexed knee position, which is less ideal in revision knees when the femoral tunnel has to be controlled in an exact manner to avoid a prior misplaced tunnel.

FIGURE 7-36 Demonstration of the flip drill technique for femoral socket or tunnel. A and B, Placement and location of the drill guide. C, Central ACL anatomic tunnel placement. D, Placement of the flip drill. E, The flip drill is advanced at the femoral attachment. F, The drill end is “flipped” at a right angle to the pin. G, Creation of a femoral socket that can extend completely as a tunnel if desired. (Courtesy of Arthrex, Naples, FL.)

The steps for this technique are shown in Figure 7-36. The steps already described for locating the central femoral ACL guide pin placement are performed. A 10-mm incision is made at the posterior one third of the thigh and at the proximal margin of the lateral femoral condyle. The drill guide is placed and the blunt proximal guide sleeve bluntly advanced to the femur. The guide pin flip-drill is advanced and the position and entrance determined with the arthroscope in the AM portal. The drill socket is created. The tunnel joint entrance is chamfered to prevent graft abrasion. The graft is passed in a retrograde manner and fixed either endoscopically or retrograde with the tunnel extending proximally and using the second incision. When the bone quality on the femur is not ideal and a femoral suture post is desired, it is easy to enlarge the incision for visualization, extend the femoral tunnel to exit proximally, and provide a graft suture post.

Endoscopic ACL Reconstruction

Multiple endoscopic ACL reconstructive techniques have been described in the literature for B-PT-B and soft tissue grafts. The approach taken in this chapter is to describe some of these techniques without specifically endorsing one over another. Regardless of the technique the surgeon selects, the anatomic placement of the tibial and femoral tunnels is exactly what has previously been described and illustrated. In Figure 7-37, the all-inside B-PT-B ACL “RetroConstruction” procedure (Arthrex, Naples, FL) is shown as an example of an advanced endoscopic technique that the senior author has used. A complete description of this technique is available from the manufacturer. There is a learning curve for the tibial interference screw fixation. The femoral tunnel technique is the same as already described.

FIGURE 7-37 Endoscopic ACL reconstruction: RetroReconstruction Procedure. The overall length of the graft must be at least 5 mm shorter than the combined length of the femoral socket, intra-articular space, and tibial socket. A, In this example, the total distance is 90 mm and the tunnels allow adequate space for tensioning of the graft. B, The lateral portal is placed in standard fashion along the lateral edge of the patellar tendon. The medial portal should be placed just medial to the patellar tendon and inferior to standard position to facilitate femoral socket preparation. Medial portal incisions may be oriented horizontally to allow instruments to be moved in the transverse plane. C, Bring the knee to 120° of hyperflexion and place the Beath pin through the medial portal into the 2 o’ clock femoral position, already described. Ream the femoral socket to a 25-mm depth. Use a Beath pin to pass a graft-passing suture and dock the suture in the femoral socket for later use during graft passing. D and E, Place a RetroCutter that is 1 mm larger than the tibial graft diameter and drill the tibial socket as deep as possible without violating the distal cortex. F, Example: If the distance between the tibial plateau and the distal tibial cortex is 50 mm, as read off the drill sleeve, then drill the socket 40 mm deep. G and H, Retrieve both the femoral and the tibial graft-passing sutures out of the medial portal. A cannula may be used to avoid tissue bridges. Using the tibial-passing suture, tie a loop around a looped Nitinol wire. Place the graft sutures from the femoral end of the graft into the femoral-passing suture. Load the tibial graft sutures into the tibial-passing suture loop. I and J, Pass the tibial bone block into place while maintaining the wire anterior in the socket. Hyperflex the knee and fix the femoral side of the graft with a biointerference screw through the medial portal. Condition the graft under tension, as described previously. K, Pass the RetroScrew Driver over the Nitinol wire and into the joint. Remove the Nitinol wire and replace it with a FiberStick. Retrieve the FiberStick out the medial portal through a Shoehorn cannula. Attach the RetroScrew, 2 mm smaller than the socket diameter, to the FiberStick. L, Pass the RetroScrew into the joint and load on the RetroScrew Driver. This step requires practice. M, Keep tension on the graft while the screw is inserted into the tibial socket. A RetroScrew Tamp may be used to ease insertion of the screw and the tibial tunnel should be 2–3 mm larger at the anterior margin to facilitate the interference screw. Backup fixation may be accomplished by tying the tibial graft-passing sutures over a two-hole suture button on the anterior cortex with a sliding knot. (Courtesy of Arthrex, Naples, FL.)

Endoscopic Transfix ACL Reconstruction

Numerous procedures are described in which a cross-femoral pin is used to provide proximal graft fixation. The author has found this represents an alternative technique to the two-incision procedure with the use of a four-strand STG graft. An example of this procedure is shown in Figure 7-38. A complete description of this technique and videotape demonstration are available from the manufacturer. It is recommended that this technique be performed in a bioskills setting prior to patient application, because there are specific steps to master. Placement of the cross-pin requires caution to ensure that the tunnel is on the lateral femoral wall and central ACL attachment location, similar to the outside-in two-incision technique previously described. This means that the cross-pin will be entering in a relatively distal position on the femoral condyle and placed posteriorly to avoid damaging the FCL attachment. The common mistake is to locate the femoral tunnel high in the attachment, adjacent to the roof.

FIGURE 7-38 A, Endoscopic Transfix ACL reconstruction (Courtesy of Arthrex, Naples, FL). B, Placement of the AM incision. C, Placement of the tibial tunnel. D, A hyperflexion position and drilling through the AM portal are used for a central femoral ACL tunnel placement. E, Four-strand STG graft looped around the wire to be passed through the tibial tunnel. F, Placement of the TransFix implant is passed over the wire and into the lateral femoral condyle to secure the graft. Prior to placing the implant, the wire should move freely in a medial-to-lateral direction. The implant should be advanced gently into the femoral tunnel and seated with the end placed into the prepared lateral cortex. The tibial fixation is with a suture post and absorbable interference screw.

Management of Graft Malposition

It is important in the operative technique to recognize whether an improper graft position has occurred so that steps may be taken to address the problem. An excessive anterior femoral tunnel results when all of the soft tissues have not been removed from the lateral femoral wall and the “around-the-corner” view posteriorly of the femoral condyle has not been achieved. It is important that the AM portal be used to view the entire lateral sidewall in selecting the ideal femoral tunnel position. When an anterior tunnel is adjacent, but has no communication with the selected femoral tunnel, an allograft bone dowel or interference screw placed in the tunnel, maintaining the proper location of the tunnel more posteriorly, is usually possible. If the anterior tunnel is large, extending posteriorly, a bone-graft procedure is indicated and ACL revision delayed. Excessive posterior placement of a femoral tunnel with a back-wall blow-out would provide a compromise to interference screw fixation. In these cases, a two-incision reorientation of the femoral tunnel is indicated, and a suture post is usually added to provide a combined interference screw–suture fixation.

An excessively posterior femoral tunnel results in shortening of the graft in extension; this requires an anterior adjustment in the tunnel. When the guide pin is placed in the femoral ACL attachment from either an inside-out or an outside-in approach, it is possible to start with a 6-mm acorn-shaped reamer to readjust the tunnel and subsequent tunnel entrance with a stepwise progression in the reamers. In this manner, the most ideal placement of the femoral tunnel may be achieved. A distal femoral tunnel past the 9 o’clock position may result in a graft impinging on the lateral femoral condyle, requiring excessive notchplasty. The final graft length is short and not ideal.

A tibial tunnel malposition posteriorly produces a vertical graft. A tibial tunnel placed too far anteriorly may result in anterior graft impingement or loss of the anterior tibial cortex for adequate interference screw fixation. A tibial tunnel placed too far medially or laterally may impinge on the PCL or lateral femoral condyle, respectively. Small adjustments may be made in medial or lateral graft position by placement of the interference screw in a medial or lateral placement. A posterior bone dowel allograft may be used in a posteriorly placed tunnel to displace the graft to a more central tibial location. Additional sutures are added to the graft for a tibial post, expecting that added fixation is necessary. The principle is never to accept a misplaced tibial or femoral tunnel and risk of a graft failure and revision knee problem.

A fracture of the bone portion of the graft, in which 15 mm of bone remains, may be managed by placing two additional sutures in the tendon portion of the graft and two sutures in the bone portion. An interference screw is used along with a suture post. If there is disruption at the bone-tendon junction, the senior author prefers to harvest an STG autograft instead of adding sutures to the tendon portion because the diameter of the patellar tendon is not ideal in the absence of the bone ends.

In cases of an Osgood-Schlatter disease or an accessory ossification of the patellar tendon at the patella attachment (that is not appreciated until the graft is harvested), it is possible to remove the excess bone that will not affect the length or integrity of the graft. However, it is best to avoid a graft from these locations in these disease states and inform the patient that an alternative graft source will be used. The problem is that it may be necessary in a large Osgood-Schlatter lesion to dissect intact tendon adjacent to the graft harvest site to remove the bony lesion entirely, which results in weakening of the tendon attachment site. This problem requires added postoperative protection and modification of the immediate rehabilitation program. B-PT-B fixation problems with interference screws are usually solvable by upsizing the screw diameter and adding a suture fixation post. It is important never to compromise the final graft fixation strength and accept a less than ideal fixation because this would potentially result in graft loosening in the early postoperative period.

It is more difficult to manage an enlarged tibial or femoral tunnel with an STG graft because the technique requires that a snug-diameter tunnel be placed to achieve a graft-tunnel interface to allow graft incorporation and avoid excessive tunnel widening. An absorbable interference screw may be necessary to compress one side of the graft into the tunnel, which would require modification of the postoperative rehabilitation to protect the graft during the initial healing stages. EndoButton techniques are frequently used with STG grafts, and problems may be encountered with inadvertent reaming of the femoral cortex and loss of fixation strength. Fixation with an interference screw provides a weaker graft fixation, and consideration of a two-incision technique with a suture post is warranted. A cross-pin fixation technique may also be used. When the EndoButton does not adequately flip and provide seating against the femoral cortex, it is necessary to add a longer length of the synthetic loop to the graft end and repeat measurements of the graft tunnel.

Identification of Tibial Tunnel Problems in Revision Knees and Need for Staged Bone-Grafting

The arthroscopic procedure is done in a standard manner and appropriate meniscus and débridement procedures are performed. It is next important to determine that the tibial and femoral tunnels can be placed into the ideal position before the autograft or allograft is harvested and prepared. The selection and preparation of autografts is described in the prior section and this is performed only after the tibial and femoral tunnels have been determined to be adequate or have been bone-grafted previously.

It is usually not difficult to identify the prior tibial tunnel entrance into the joint after removal of the soft tissues and graft material at the ACL attachment location. The adjacent lateral meniscus attachment may be encased in scar tissue and is preserved. The PCL, posterior ridge, medial tibial spine, and medial articular cartilage are all identified. The farthest extent of the posterior ACL tibial attachment is approximately 8 mm anterior to the posterior ridge (RER), as already discussed. This is a critical measurement because many primary ACL operative procedures place the ACL graft into the posterior one third of the ACL attachment. It is often the case that during the drilling procedure for the posterior tibial tunnel, or in using this tunnel for the femoral tunnel placement, the tunnel is enlarged posteriorly out of the native ACL footprint and extends to the RER. This situation results in a vertical ACL graft. Often, the preoperative MRI will allow measurements of the tunnel location relative to the AP width, as already described, and the surgeon is aware preoperatively of this problem (Fig. 7-39).

FIGURE 7-39 A series of four cases with enlarged tibial tunnels and vertical ACL graft orientation requiring staged bone grafting prior to ACL revision surgery. Often, the radiograph underestimates the extent of tunnel widening requiring bone grafting. If these tibial tunnels were accepted for a revision graft, the graft placement would remain too posterior, not in the ideal ACL central attachment, and a snug graft tunnel interface would not be established. Accordingly, bone grafting was required in all cases prior to revision surgery.

It may initially appear that the tibial tunnel is acceptable; however, after removing all of the soft tissues or when the tibial tunnel drilling is performed, the surgeon may discover that a posterior tibial tunnel exists that extends all the way to or through the RER, which is not acceptable for the revision graft. These cases require staged bone-grafting (Fig. 7-40). On occasion, the posterior tibial tunnel is located in the posterior one third of the native ACL attachment, with only a 5-mm bridge between the tunnel and the RER. If the tibial tunnel is not dilated requiring grafting, it is possible to drill and relocate the tibial tunnel approximately 8 mm anteriorly into a more advantageous central ACL attachment position. A cortical allograft dowel is positioned to occupy and fill the posterior one third of the tunnel, maintaining the graft in the ideal central position. Another technique is to fashion the bone plug of a revision allograft, maintaining an enlarged bone block to fill the posterior portion of the tibial tunnel and prevent the collagen portion of the graft displacing posteriorly. A third technique is to perform a double-bundle reconstruction with the posterior tibial tunnel used for the PL bundle (assuming the graft is placed into the native ACL tibial footprint and not located in an abnormal posterior position). A second anterior tibial tunnel is used for the AM bundle. Use of double-bundle grafts in a revision procedure requires that the femoral tunnel location also be ideal, which is often a problem. A misplaced femoral tunnel may prevent two additional tunnels to be adequately placed or the two additional tunnels could possibly weaken the femoral condyle.

FIGURE 7-40 A, A 31-year-old woman with failure of a primary ACL STG autograft and revision anterior tibial allograft of the left knee. B, A bone graft of a large tibial tunnel was performed with allograft. C and D, The allograft procedure did not provide a restitution of the tibial tunnel and a residual widening was present. E, A repeat bone graft using autogenous iliac crest was required to obtain bone of sufficient quality for an ACL revision.

In the authors’ opinion, the mistake that is possible at ACL revision is to accept a posterior tibial tunnel position for a single-graft procedure. If there is any question that the bone quality is not ideal and that the revision graft would be placed into the posterior one third of the native tibial attachment and result in a windshield effect on weakened bone posteriorly eroding through to the RER, it is preferable to proceed with the staged bone-grafting. The alternatives listed previously to relocate the graft tunnel are indicated only when good bone quality exists and the prior tibial tunnel does not extend beyond the native ACL attachment. In the authors’ experience, in the majority of revision cases involving a posteriorly placed tibial tunnel, the tunnel is frequently dilated and expanded. This is not suitable for bone incorporation into the revision graft, and there is little question that a staged bone-grafting is necessary.

Identification of Prior Femoral Tunnel in Revision Knees and Need for Staged Bone-Grafting

The arthroscope is placed in the AM portal to view the entire lateral notch and notch roof, and all soft tissues and graft material are removed. An angled curet, suction cutting device, and occasionally a radiofrequency probe are used. Any spurs or overgrowth of the notch are removed and a limited notchplasty performed to view the farthest posterior aspect of the lateral notch. A mistake is to not remove all of the lateral soft tissues adjacent to the lateral femoral condyle articular cartilage edge because this is the landmark for identification of the correct location of the revision graft. With a prior vertical tunnel or anterior tunnel, it is often possible to outline the native ACL attachment, which provides important identification landmarks for graft location. The ACL footprint is mapped out and the determination is made whether an ideal anatomic tunnel is possible, as described.

In a majority of revision cases, the index graft is placed in a vertical nonanatomic position on the roof of the intercondylar notch (Fig. 7-41), and it is possible to place the revision tunnel in the ideal central ACL anatomic attachment. The author uses the two-incision approach to reorient the tibial tunnel entirely away from the index tunnel. It is sometimes possible to perform an endoscopic approach using an AM portal to drill the femoral tunnel with a hyperflexed knee; however, the two-incision technique is preferable in most revision procedures. In posterior wall femoral blow-out situations, a reoriented tunnel wall can often be used and the bone portion of the graft fashioned so that the bone is placed in the posterior portion of the tunnel to maintain the collagen portion of the graft within the native ACL femoral footprint.

FIGURE 7-41 Patients who presented to the authors’ center for ACL revision with a vertical ACL graft, easily detected on anteroposterior (AP) and lateral radiographs and magnetic resonance imaging. The femoral graft location is primarily on the notch roof. In the authors’ experience, this vertical graft orientation is the primary cause for ACL failure.

The more difficult problem is the management of a dilated and slightly misplaced femoral tunnel that is at the native ACL attachment or perhaps extends a few millimeters beyond the native ACL attachment. The new tunnel will overlap and produce an enlarged dilated tunnel with portions extending beyond the native ACL footprint. There is a technique in which two stacked interference screws (absorbable or metallic) are used to provide a buttress against one side of a dilated tunnel to locate the graft within the ideal femoral attachment. However, this technique is possible only when the femoral tunnel is close to ideal and the stacked interference screw is truly used as a buttress screw against one side of the tunnel wall. The remainder of the femoral tunnel cannot be dilated or enlarged, and the bone quality about the femoral tunnel is not osteopenic and allows for graft fixation. The femoral tunnel does not extend to the roof of the notch or to the edge of the femoral articular cartilage.

As previously described for the tibial tunnel, the mistake that may be made is to accept a “slightly enlarged” femoral tunnel in which the graft placement is not ideal, such as too proximal or anterior on the lateral femoral wall. If there is any question, a bone-grafting procedure is performed and the revision procedure done 6 months later. Meniscus repairs may be done with the bone-grafting procedure to protect the meniscus, and a functional brace used until the revision procedure is performed.

Bone-Grafting Procedure for Tibial and Femoral Enlarged Tunnels

Principles are available to follow in performing bone-grafting of enlarged tunnels. The first is to adequately prepare the graft site by removing all soft tissues, curet, and place small drill holes into the cortical tunnel walls to provide the most ideal surface for bone-graft healing. Cultures of the removed soft tissues are obtained. Rarely, a gram stain and frozen section are necessary to exclude an occult infectious process within a tibial or femoral tunnel, particularly when an allograft was used. Second, it is ideal to use autogenous bone that is supplemented by allograft bone in larger defects. Third, the posterior tibial RER, when deficient, is replaced with good-integrity cortical-cancellous bone (such as a bicortical iliac crest autograft) and not cancellous bone, which is a weaker construct. The goal is to prevent the revision graft in the newly placed tunnel from enlarging the tunnel posteriorly by a windshield-wiper effect against poor-quality bone. The same situation applies to an enlarged dilated femoral tunnel in which the anterior shallow portion of the tunnel is grafted with a combined cortical-cancellous autograft to obtain a good-quality bone construct. The senior author prefers a “minimally invasive” iliac crest autograft procedure, removing only the superior and outer portions and not disturbing the inner table and muscle attachments. This procedure is described in detail in Chapter 31, Primary, Double, and Triple Varus Knee Syndromes: Diagnosis, Osteotomy Techniques, and Clinical Outcomes. The outer iliac crest can be fashioned into a rectangular or circular dowel that is wedged into the enlarged tibial or femoral tunnel, providing a near-complete filling of the expanded tunnel and likelihood of the revision procedure being performed in 3 to 5 months. Strips of cortical cancellous bone are packed into any remaining defects and, if necessary, supplemented with allograft iliac crest bone. In major defects, cancellous bone in the range of 5 to 8 mm fragments are packed between the cortical-cancellous strips. The bone-grafting procedure is easily performed in an arthroscopically assisted manner, enlarging the portals as necessary to deliver the bone graft into the femoral tunnel. The tibial tunnel is packed in a retrograde manner, observing the final position of the graft from an appropriate arthroscopic portal.

Thomas and colleagues¹⁸¹ performed staged ACL revision reconstruction in a series of 49 knees, all of which required bone-grafting of previous tibial tunnels to avoid overlap into correctly placed revision tunnels. The authors stressed the importance of ensuring good-quality bone stock to achieve anatomic ACL graft placement and adequate fixation. At follow-up a mean of 6 years postoperatively, only 2 of the revision knees had failed.

Bone-graft substitutes are commercially available; however, their role instead of autogenous or allograft bone has not been established in clinical studies. The authors recommend autogenous bone that is supplemented with allograft when necessary. It is probable that under certain circumstances, an allograft bone supplemented with a platelet gel or cancellous marrow cells will provide an equal alternative to autograft iliac bone. This procedure is being used for opening wedge osteotomy and may be applicable to enlarged tibial and femoral tunnels. There is a longer period of time for host replacement of an allograft in large expanded tunnels until the revision procedure is performed. With autogenous bone, the healing of the tunnels is prompt and predictable, and the revision may be performed within a few months. A computed tomography scan may be necessary to confirm bone-graft incorporation in suspect cases.

The postoperative rehabilitation program is described in Chapter 13, Rehabilitation of Primary and Revision Anterior Cruciate Ligament Reconstructions. The authors do not administer preoperative or intraoperative intra-articular anesthetic injections or use pain pump catheters postoperatively owing to the possible complication of adverse effects on articular cartilage.^68,84,154