History

ACL injuries typically occur in patients who participate in activities that require running, jumping, or cutting. The classic scenario is often a young female athlete who sustains an injury while her foot is planted and slightly flexed, with a pivot moment applied to the knee. The ensuing injury is often characterized as a “pop” or other traumatic event, and swelling from a hemarthrosis is often present within minutes to hours after this insult. The patient history from a partial disruption of the ACL or from a patient who continues to have laxity despite having undergone prior reconstruction can be more vague. In some instances of partial ACL disruption, a traumatic event may occur, as is the case with a complete tear; however, in many cases patients may report a minor event in which the knee may have felt as though it shifted or rolled. Patients may have even gone back to competitive play the same day or within a week of the initial injury. In rare cases, there may be the minor complaint of pain with certain activity, with no specific injury reported. Within the setting of prior ACL reconstruction, patients are usually good historians with regard to their symptoms due to their prior experience. The patient in this setting may state that the knee continues to feel unstable or has no strength, or the patient may be observed by coaches and the training staff to lack this confidence on the knee due to subtle differences from the noninjured leg. Determining the exact amount of morbidity from these symptoms can be challenging but is very important in deciding whether surgical intervention is warranted.

Physical Examination

The physical examination is very similar to that for most knee injuries. The knee is first inspected for any bruising or contusion that may indicate a more serious injury. The knee is checked for an effusion; if one is present and causing significant discomfort that impedes the physical examination, we will aspirate it from a superolateral portal. The range of motion is assessed; if limited, it may indicate concomitant meniscal pathology, although this is rarely seen with partial tears of the ACL. The knee is then examined for any tenderness along the joint line or joint line swelling, which also could represent the presence of meniscus pathology. The ligamentous evaluation is performed and compared with the contralateral extremity. The knee is checked first for valgus or varus instability at both 0 and 30 degrees. The Lachman and pivot-shift exams are then performed. The presence of a 2+ or 3+ Lachman with minimal shift may indicate involvement of the AM bundle with minimal involvement of the PL bundle. It is important to ascertain whether the patient is guarding or contracting the hamstrings, as these actions will impair the clinician’s ability to detect pathologic translations. The patient who has a large pivot shift with very minimal translation on the Lachman examination may have an isolated injury to the PL bundle. Rarely will patients have a positive anterior drawer sign, as the secondary stabilizers (medial meniscus/posteromedial corner) are usually preserved within this injury pattern. The exam concludes with determination of the KT-1000 and its comparison with the contralateral extremity. A normal KT does not preclude the presence of injury to a portion of the ACL and is no substitute for a good physical examination.

Imaging

We obtain plain radiographs in all patients to look for associated pathology. These radiographs include bilateral anteroposterior (AP) flexion weight-bearing views, a lateral view of the involved knee, and bilateral merchant or sunrise views. The radiographs are inspected for soft tissue swelling, an effusion, the presence of any fractures, physeal closure (for younger patients), and overall alignment. In patients who have undergone prior ACL reconstruction, the prior tunnel placement is evaluated as well as prior hardware placement and presence of tunnel expansion. Determination of joint space narrowing is paramount in determining prognosis, and any patient who demonstrates any evidence of arthrosis on the knee series is further evaluated with a long cassette to determine alignment. If significant side-to-side difference exists (greater than 3–5 degrees) on the alignment series, consideration is given to a realignment procedure to unload the affected compartment. We obtain a magnetic resonance imaging (MRI) scan in any patient suspected of having a partial ACL tear or continued laxity after prior single-bundle ACL reconstruction. The MRI is also useful to inspect for the presence of any meniscal or chondral pathology. Reviewing the MRI with an experienced radiologist is often necessary to accurately make the diagnosis and properly plan for surgical intervention. Studies have shown that MRI diagnosis of partial ACL tears can be challenging.^14,15 In one series, nine of nine complete tears were accurately diagnosed by MRI, whereas only 1 of 9 partial tears were correctly identified.¹⁴ Findings that were suggestive of partial ACL tears in this series were the presence of some intact fibers, thinning of the ligament, a mass posterolateral to the ACL, and a wavy or curved ligament. The MRI is inspected for the presence of a bone contusion, as this usually indicates a more severe injury. One study demonstrated that only 12% of patients with a partial tear of the ACL had a bone contusion in comparison to 72% with complete tears.¹⁶

Additional coronal imaging may help to better delineate injury to the PL bundle, whereas the sagittal images are usually sufficient to visualize the AM fibers.

Indications

The indications for PL bundle augmentation surgery are not solely based on the preoperative evaluation. A patient who has undergone a prior single-bundle reconstruction with adequate graft placement and incorporation but who continues to experience patholaxity is perhaps the optimal candidate for this procedure. Patients who have suspected partial tears of the ACL with a positive pivot-shift examination, minimal translation with the Lachman maneuver, and an MRI that confirms the presence of the AM bundle are also qualified candidates for this procedure; however, these patients should demonstrate that they have recurrent laxity after a rehabilitation program and functional bracing regimen. These parameters are further defined arthroscopically once the entire injury pattern to the ACL is delineated and the presence of an intact AM bundle and disrupted PL bundle is found at surgery. Contraindications to surgical intervention include a patient who is unwilling to cooperate with the rehabilitation program and a patient who lacks a full or near-full range of motion on physical examination. The presence of open physes is not an absolute contraindication to using this technique; however, we do advise that younger patients be braced until they have reached skeletal maturity.

Anesthesia and Positioning

Patients undergoing this procedure receive a femoral nerve block within the preoperative holding area. Once within the operating suite, the patient is given conscious sedation and placed supine on the operating room table. A thorough examination under anesthesia (EUA) is undertaken to confirm the findings from the office examination. A tourniquet is applied to the proximal thigh of the operative limb, and the contralateral extremity is placed in a padded well leg holder flexed and abducted at the knee and hip so that the operative field is cleared of any obstruction. Care is undertaken to pad the peroneal nerve and heel of the uninvolved leg. The operative limb is then placed in an arthroscopic leg holder that allows for greater than 100 degrees of knee flexion, and the foot of the table is lowered. The leg is then elevated for 5 minutes, and the tourniquet inflated to 100 mmHg greater than the systolic pressure. The leg is then prepped with povidone-iodine (Betadine) solution and draped free in the usual fashion.

Surgical Landmarks and Diagnostic Arthroscopy

The knee is slightly flexed to 45 degrees, and the anatomical landmarks are identified. The inferior pole of the patella is drawn as well as the tibial tubercle. The borders of the patellar tendon and the anterior crest and posteromedial border of the tibia are identified. Three portholes are marked on the knee in the same fashion as in the double-bundle technique. The lateral porthole is located just off the lateral border of the patellar tendon with its most inferior border flush with the inferior border of the patella. The medial porthole is marked beginning at the inferior pole of the patella and extending distally just on the medial border of the patellar tendon. An accessory medial porthole that will later be used for the PL tunnel is marked approximately 2 cm medial to the AM porthole just at the level of the joint line. The tibial incision is marked on the AM aspect of the tibia midway between the anterior and posterior borders of the tibia. This incision is approximately 3 cm in length, beginning 2 cm distal to the medial joint line (Fig. 60-1).

Fig. 60-1 Surface landmarks for surgery (left knee). Note the accessory medial porthole (AMP) placement and the superior placement of the lateral porthole (LP). MP, Medial porthole.

Diagnostic arthroscopy is undertaken after establishment of the lateral and medial portholes. Placement of the lateral porthole slightly superiorly obviates the need for excessive fat pad débridement as the arthroscope is introduced proximal to this vital structure through this viewing porthole. All three portholes are used for viewing during the procedure, and the surgeon is encouraged to obtain different vantage points from each porthole to ensure proper anatomical position of the femoral tunnel. We begin our arthroscopy in the patellofemoral joint, débriding only the synovium that obstructs our view with a 4.5-mm full radius resector. The arthroscope is then swung down into the notch for a clear view of the ACL and posterior cruciate ligament (PCL). Varus stress is then applied to the knee in the figure-four position, and the lateral hemi-joint is inspected. Any articular or meniscal pathology is addressed at the time of inspection. The knee is then placed in slight flexion and valgus, and the medial hemi-joint is inspected. The scope is then brought back to the notch with the leg at 90 degrees of flexion (the neutral position). At this point, a spinal needle is used to localize the accessory medial porthole. The needle should be visualized above the anterior horn of the medial meniscus and should provide direct access to the origin of the PL bundle on the lateral femoral condyle (LFC). Placing the arthroscope in the medial porthole may help to delineate this more clearly. The accessory medial porthole is then incised with an upturned 11 blade, with care taken not to transect the anterior horn of the medial meniscus.

The notch is inspected for disruption of the fibers of the ACL. A probe is used to apply stress to the damaged ligament. Placing the knee in the figure-four position can aid in viewing the root of the lateral meniscus as it enters the tibia. Just anterior to this structure and often confluent with the lateral meniscus is the insertion of the PL bundle of the ACL. These fibers are followed proximally to the LFC and assessed for competence. The knee is then brought back to the neutral position, and the AM bundle is assessed. A thermal device and small radius resector are used to carefully dissect out the fibers of the ACL, removing only tissue that has no origin or insertion. Once this has been achieved, the rupture pattern of the ACL is clearly seen and reconstruction of the damaged portion can be undertaken. In the setting of prior single-bundle ACL reconstruction, the graft is inspected for proper position and preparation is made for insertion of a PL bundle.

Graft Preparation

Once the diagnosis has been confirmed, the graft is prepared by the surgical assistant on the back table. We prefer to use a looped tibialis anterior allograft for this procedure because the width and length of the graft are predictable. The graft is trimmed so that, when looped over, it will fit snugly into a 7-mm tunnel. A #2 braided suture is whipstitched up and down both ends of the graft for approximately 3 cm. Using a graft of at least 24 cm in total length will provide a looped graft of 12 cm, which is sufficient graft for the reconstruction. Once doubled over, the graft is secured via a loop to the Endobutton (Smith & Nephew, Andover, MA) device. Two sutures are then passed through the Endobutton device for later graft passage. An absorbable suture is used to suture the graft closed around the loop that secures the Endobutton. The graft is marked at two sites on its proximal end, one line indicating the tunnel length and the other indicating where the Endobutton can be flipped for femoral fixation (Fig. 60-2). The graft is then washed with antibiotic solution and placed in a moistened sponge until it will be used during the procedure.

Fig. 60-2 The allograft construct for posterolateral augmentation.

Technique for Reconstruction

During the diagnostic examination, the femoral site of the PL bundle is marked with the thermal device where the fibers are avulsed. Knowledge of the origin of the ACL bundles on the LFC is paramount if no fibers of the ACL are remaining (Fig. 60-3). In the absence of this landmark (as in chronic cases or augmentation of a prior single-bundle reconstruction), general guidelines for the PL insertion are a point 8 mm posterior to the anterior articular margin of the lateral femoral condyle and 5 mm superior to the inferior articular margin of the LFC. A -mm Steinman pin is introduced from the medial accessory porthole directly to this point. For optimal visualization, the arthroscope can be inserted into the medial porthole during preparation of the femoral tunnel (Fig. 60-4). The pin is tapped gently into the LFC to obtain initial purchase, and then the knee is flexed to approximately 115 to 120 degrees and the pin is sunk 5 to 10 mm into the condyle. The acorn reamer (7 mm) is then placed over the Steinman pin through the accessory medial porthole, and the femoral tunnel is drilled to a depth of 25 mm. The far cortex is then breached with the Endobutton drill, and the transcondylar length is measured with a depth gauge. If this length is greater than 35 mm, the tunnel is reamed an additional 5 mm for a total length of 30 mm. The tunnel length is then subtracted from the transcondylar length to determine the appropriately sized Endobutton, which is then fashioned to the graft by the surgical assistant.

Fig. 60-3 Anatomical relationship of the anteromedial (AM) bundle, posterolateral (PL) bundle, and lateral femoral condyle (LFC).

Fig. 60-4 A, The placement of the posterolateral tunnel (PL) is just off the articular surface of the lateral femoral condyle (LFC). B, The tunnel is then drilled over the Steinman pin. AM, Anteromedial bundle.

Attention is now turned to the tibial tunnel. It is paramount during this procedure that the tibial insertion of the PL bundle is accurately obtained so that the AM bundle is not compromised in any fashion. An incision is carried out based on our previous landmark, and the periosteum of the anteromedial tibia is exposed. The PL tibial insertion is identified at a site just medial to the attachment of the posterior horn of the lateral meniscus and slightly anterior to the PCL. The ACL director guide (Smith & Nephew, Andover, MA) is brought through the medial porthole and placed at this insertion site, set to 55 degrees. We prefer to use the direct “tip-to-tip” guide for accurate placement of the tunnel because the margin for error in this region is small. A -mm Steinman pin is drilled through this guide on the AM surface of the tibia (typically slightly medial to the halfway point of the anterior and posterior borders of the tibia). The pin is drilled so that the tip is visible within the joint. A curette is used to prevent overpenetration in this region (Fig. 60-5). The PL tibial tunnel is then reamed to a diameter of 7 mm, and debris is removed with a full-radius resector. The PL tunnel should avoid the AM footprint entirely and be almost obscured from view by the fibers of the AM bundle.

Fig. 60-5 A curette is used to prevent overpenetration upon drilling the posterolateral (PL) tibial tunnel. Note the presence of the anteromedial (AM) bundle anterior to the PL insertion. LFC, Lateral femoral condyle.

A Beath pin with a large looped suture on its distal end is then introduced through the accessory medial porthole and fashioned through the PL femoral tunnel out through the lateral aspect of the thigh. Care is taken to hyperflex the knee and retract the biceps manually to prevent injury to the common peroneal nerve with this maneuver. The looped suture is then brought into the joint and obtained via a suture grasper through the tibial PL tunnel. The sutures attached to the Endobutton are then fashioned through the loop, and the sutures are shuttled to the lateral aspect of the thigh (Fig. 60-6). The graft is then passed in standard fashion and the Endobutton loop is flipped, providing femoral fixation (Fig. 60-7). The knee is then cycled from 0 to 120 degrees 20 times while holding tension on the tibial side to check for isometry and remove any slack within the allograft tissue. The PL bundle is then tensioned between 0 and 10 degrees with a biointerference screw measuring 7 × 30 mm. This fixation is augmented with a small staple on the AM aspect of the tibia with the remainder of the allograft. The knee is then checked for stability and range of motion.

Fig. 60-6 Graft passage is assisted by shuttling the Endobutton sutures through the posterolateral (PL) tibial and femoral tunnels. AM, Anteromedial bundle; LFC, lateral femoral condyle.

Fig. 60-7 Final graft construct with crossing of the bundles with the knee in flexion. AM, Anteromedial bundle; LFC, lateral femoral condyle; PL, posterolateral bundle.