Subjective and Functional Outcome

Patients complete questionnaires and are interviewed for the assessment of symptoms, functional limitations, sports and occupational activity levels, and their perception of the overall knee condition according to the Cincinnati Knee Rating System (see Chapter 44, The Cincinnati Knee Rating System).¹³

Symptoms of pain, swelling, and giving-way are well-recognized consequences of ACL-deficiency.¹⁰⁸ However, in the knee with combined varus malalignment and ACL deficiency, several different knee subluxations may produce symptoms of instability. These include anterior subluxation of the tibia, separation of the lateral tibiofemoral compartment on walking (varus thrust), posterior subluxation of the lateral tibial plateau (with knee flexion and external tibial rotation), and excessive hyperextension or varus recurvatum with a back-knee or feeling of the knee joint going into hyperextension. By history and asking the patient to demonstrate the knee instability, the surgeon must carefully determine the subluxations present.

Physical Examination

A complaint of medial joint line pain may or may not correlate with the degree of medial compartment articular cartilage damage.^50,58 In the early stages, the patient usually complains of medial pain that occurs with sports activities, but not with daily activities. When pain occurs with daily activities, it is highly likely that extensive damage exists to the joint articular cartilage. Loss of the medial meniscus is the major risk factor for the progression of arthritis in the medial compartment.³⁷

The physical examination of the knee joint to detect all of the abnormalities in the varus-angulated knee is comprehensive (Table 31-2) and includes assessment of (1) the patellofemoral joint, especially possible extensor mechanism malalignment due to increased external tibial rotation and posterolateral tibial subluxation; (2) medial tibiofemoral crepitus on varus loading, indicative of articular cartilage damage even if not visible on radiographs; (3) pain and inflammation of the lateral soft tissues due to tensile overloading; (4) gait abnormalities (excessive hyperextension or varus thrust) during walking and jogging¹⁰⁴; and (5) abnormal knee motion limits and subluxations compared with the contralateral knee.¹⁰⁶

TABLE 31-2 Diagnosis of Abnormalities

Calculations to Determine Angular Correction

The preoperative calculations for HTO involve precise measurements to determine the amount of angular correction desired to redistribute tibiofemoral forces while not altering tibial slope and tibiofemoral joint obliquity in the frontal plane.^35,107 The normal tibiofemoral coronal alignment is shown in Figure 31-14. In varus angulated knees, there is a slight increase in obliquity due to medial tibiofemoral joint arthrosis principally involving the medial condyle. An opening wedge femoral osteotomy restores the joint obliquity. The more difficult issue related to joint obliquity involves correcting a valgus malalignment in which a change in joint obliquity is common. An opening wedge osteotomy corrects the joint obliquity, whereas a closing wedge tibial osteotomy increases joint obliquity and therefore is contraindicated.

FIGURE 31-14 The normal tibiofemoral coronal alignment.

Critical Points PREOPERATIVE PLANNING

• Determine angular correction to achieve redistribution of tibiofemoral forces without altering tibial slope.

• Take into account abnormal lateral tibiofemoral separation from deficient posterolateral structures.

• Measure weight-bearing line on bilateral standing hip-knee-ankle radiographs.

Weight-bearing line is dependent on femoral and tibial lengths and angular deformity.

• Measure tibial slope on lateral radiographs.

• Increasing tibial slope increases anterior tibial translation; potentially, tensile loads on the ACL.

• Decreasing tibial slope increases posterior tibial translation; potentially, tensile loads on PCL.

• Do not alter normal tibial slope unless it is markedly abnormal.

Tibial slope >2 standard deviations above normal.

• Do not alter a normal tibal slope in ACL-deficient or PCL-deficient knees.

• Maintain normal tibial slope: anterior gap at medial opening wedge should be half the posteromedial gap. Every millimeter of anterior gap change = 2° change in tibial slope.

Timing of HTO in Knees with Ligament Deficiencies

Primary Varus Knees

• Cruciate reconstruction with HTO or later (no abnormal lateral joint opening present).

Double Varus Knees

• HTO first.

• Posterolateral structures may shorten with valgus alignment.

• Perform cruciate, posterolateral reconstructions later if required.

Triple Varus Knees

• HTO first, cruciate and posterolateral reconstruction later.

Opening Wedge Advantages

• Avoids lateral dissection, fibular osteotomy.

• Large correction > 12°, avoids tibial shortening.

• Distal advancement or reconstruction of the MCL in chronic MCL ruptures.

• In subsequent posterolateral reconstructions, avoids proximal fibular osteotomy, allows FCL grafts to be fixated securely to proximal fibula.

Closing Wedge Advantages

• Faster healing.

• Earlier resumption of weight-bearing.

• Superior strength initial osteotomy fixation.

• Decreased risk early loss of correction, nonunion.

• More difficult to achieve correction at surgery.

• Large closing wedge may elevate patellar height and decrease lower limb length; reverse applies with opening wedge.

Opening Wedge HTO: Maintenance of Tibial Slope

• Opening wedge angle is dependent on the angle of coronal valgus correction and the angle of obliquity of the anteromedial tibial cortex.

• Every millimeter of alteration in gap height results in a change of 2° in tibial slope.

ACL, anterior cruciate ligament; HTO, high tibial osteotomy; MCL, medial collateral ligament; PCL, posterior cruciate ligament.

An undercorrection or overcorrection in the coronal plane may result if the surgeon fails to recognize the effect of lateral tibiofemoral separation on increasing varus angulation that results from slack or deficient lateral soft tissues. Inaccurate calculations may also arise from failure to use the WBL from double-stance, full-length, standing radiographs of both lower extremities to determine the angular deformity. A single-stance radiograph of the affected limb will show the maximum varus angulation due to lateral condylar lift-off. However, a double-stance radiograph helps to close the lateral tibiofemoral compartment so the true osseous alignment is calculated, which is required for surgical correction.

Sabharwal and Zhao¹²⁴ compared lower limb coronal alignment on full-length, standing radiographs with supine intraoperative hip-knee-ankle fluoroscopy measurements in 102 limbs. There was a statistically significant mean difference between the two techniques (mean, 13.4 mm deviation in the WBL, measured from the center of the joint). This difference in the two techniques is of concern in the preoperative planning and the final intraoperative osteotomy correction in the coronal plane. The reader should note that there was no description of accounting for the effect of abnormal lateral joint opening on the standing radiographs that would account for errors on full-length, standing radiograph preoperative measurements, as previously discussed. Further, at surgery there was no description of the fluoroscopy technique. The surgeon must verify medial and lateral tibiofemoral joint contact to account for possible opening of the medial or lateral tibiofemoral joint during the WBL measurement. The fluoroscopy technique involves the surgeon placing an axial load against the foot to overcome medial or lateral joint opening, which is verified by the fluoroscopic image. The lower extremity should be held in 10° of knee flexion and approximately 10° to 15° of external rotation (hip to ankle axial alignment simulating the foot progression angle). The limb alignment rod at the knee joint can be observed to move medial to lateral with internal to external limb rotation, which is another source of error in measuring the WBL intersection at the tibia. This is because the alignment rod is placed anterior to the true center of axial rotation at the ankle joint, and therefore, lower limb rotation induces this error. One advantage of the computerized navigation technique is that the WBL is centered through the hip-knee-ankle joints whereas an alignment rod or cord used at surgery is placed anterior to these respective joints.

An example of the potential effect of the failure to account for increased lateral joint opening is shown in Figure 31-15. The case represents a 38-year-old man whose full-length, standing radiograph shows a varus angular deformity (mechanical axis) of 7° and a 4-mm increase in lateral joint opening. The width of the tibial plateau is 81 mm. The equation to determine the angular deformity resulting from the lateral tibiofemoral separation distance is

FIGURE 31-15 Sketch of a standing AP roentgenogram. The lateral joint space is 8 mm on the left side and 4 mm on the right side. The calculated angular deformity resulting from the 4-mm joint opening is 3.7° of the total 7° of deformity. WBL, weight-bearing line.

S, lateral joint opening space; TW, tibial width.

Therefore, in this patient, the calculated amount of varus angular deformity caused by the lateral joint opening increase of 4 mm is

Failure to account for the lateral joint opening would result in approximately 4° of valgus overcorrection after HTO, assuming closure of the lateral tibiofemoral joint (Fig. 31-16). A WBL crossing the knee lateral to the 75% coordinate has the potential for a lift-off of the medial femoral condyle. Unicondylar weight-bearing resulting from distraction of the medial compartment is undesirable and could result in subsequent arthritis of the lateral compartment, medial collateral ligament (MCL) laxity, and a progressive valgus deformity (Fig. 31-17). The WBL-tibial intersection depends on the coronal mechanical axis angle and the femoral and tibial lengths of the patient; the senior author’s published study³⁵ showed the WBL axis to be more accurate than the anatomic axis for osteotomy correction.

FIGURE 31-16 The effect of abnormal lateral joint opening on varus angular deformity. With a varus moment applied through a fulcrum, or center of rotation (Q), lateral joint space opening (S) occurs in the presence of slack lateral soft tissues resulting in an additional α° of varus angular deformity.

FIGURE 31-17 A 32-year-old woman with abnormal lateral joint opening underwent HTO elsewhere. The preoperative planning failed to account for the abnormal lateral joint opening, which resulted in a severe valgus overcorrection and need for revision osteotomy.

Two methods are used to determine the correction wedge on preoperative radiographs.³⁵ First, the centers of the femoral head and tibiotalar joint (center of the talus) are marked on the full-length radiograph (Fig. 31-18). The desired correction in the WBL coordinate of the tibial plateau is identified and marked. This is usually placed at 62% of the tibial width (just at the down slope of the lateral tibial spine), which allows the WBL to pass through the lateral tibiofemoral compartment, providing a 2° to 3° angular valgus overcorrection. The 62% WBL coordinate is used if there is medial tibiofemoral articular cartilage damage and the intention is to transfer major loads to the lateral compartment. A 50% WBL coordinate is chosen if there is no medial tibiofemoral joint damage and the surgeon wishes to correct to a neutral axial alignment (e.g., prior to posterolateral reconstruction). One line is drawn from the center of the femoral head to the selected percent WBL intersection at the tibia, and a second line is drawn from the center of the tibiotalar joint to the same tibial coordinate position. The angle formed by the two lines intersecting at the tibia represents the angular correction required to realign the WBL through this coordinate. An alternative method was published³⁵ in which the previously discussed femoral and tibial axis lines intersect at the hinge point of the tibial osteotomy. This technique ends up with a similar measurement for the angular correction. However, the surgeon does not have the measured WBL tibial intersection required for intraoperative fluoroscopy verification.

FIGURE 31-18 Graphic depiction of the method used to calculate the correction angle of an HTO using a full-length AP radiograph of the lower extremity. The lines from the centers of the femoral head (CFH) and tibiotalar joint (CTTJ) converge in this example at the 62% coordinate.

The second method of determining the correction wedge involves cutting the full-length, standing radiograph horizontally through the line of the superior osteotomy cut (Fig. 31-19). A vertical cut of the lower tibial segment (opening or closing wedge) is made to converge with the first cut. The distal portion of the radiograph is aligned until the center of the femoral head, the selected WBL coordinate point on the tibial plateau, and the center of the tibiotalar joint are all colinear. With the radiograph taped in this position, the angle of the wedge formed by the overlap of the two radiographic segments is measured and compared with the value obtained using the first method. The mechanical axis is measured to determine the angular correction. If there is a discrepancy between the two correction wedge angles, the procedures should be repeated.

FIGURE 31-19 Graphic depiction of an alternative method used to calculate the correction angle of an HTO using a full-length AP radiograph of the lower extremity. The roentgenograph is cut to allow the center of the femoral head (CFH), the 62% coordinate, and the center of the tibiotalar joint (CTTJ) to become colinear. The angle of the resulting wedge of roentgenograph overlap equals the desired angle of correction. The example is provided for a closing wedge osteotomy. The same technique is used for an opening wedge osteotomy in which the medial tibial opening wedge is made to obtain the desired correction.

Calculations to Determine Tibial Slope and Clinical Indications to Change Tibial Slope

Lateral radiographs are examined and measurements made of the tibial slope. Abnormal posterior sloping of the tibia in the sagittal plane may occur after tibial osteotomy, tibial fractures, growth abnormalities, or rarely, as a congenital occurrence.

Several methods have been reported to measure the medial and lateral tibial slope based on lateral tibial radiographs (Table 31-3).^{17,20,24,25,41,63,79,82,146} Each method results in different slope values for the same tibia (Fig. 31-20), and all studies show high standard deviations and ranges, indicating that tibial slope may show variation among individual patients. Brazier and colleagues²⁰ measured 83 lateral knee radiographs and concluded that the methods of slope measurement of proximal tibial anatomic axis (PTAA) and posterior tibial cortex were more reliable than other methods. Genin and coworkers⁴¹ and Julliard and associates⁶³ recommended using the tibial mechanical axis to represent the true tibial slope. The PTAA is the authors’ preferred method for HTO, and the anterior tibial cortex measurement is used when cutting the proximal tibia during total knee arthroplasty (TKA).

FIGURE 31-20 Some reported radiographic techniques to measure the tibial slope. The values obtained depend on the anatomic site selected on the tibia. Selected literature references for reported values are shown in Table 31-3. ATC, anterior tibial cortex; FSA, fibular shaft axis; PFAA, proximal fibular anatomic axis; PTAA, proximal tibial anatomic axis; PTC, posterior tibial cortex; TMA, tibial mechanical axis.

(Reprinted with permission from Noyes, F. R.; Goebel, S. X.; West, J.: Opening wedge tibial osteotomy: the 3-triangle method to correct axial alignment and tibial slope. Am J Sports Med 33:378–387, 2005.)

Most authors have measured the medial tibial slope; only a few have measured and provided data on the lateral tibial slope.^79,146 The lateral tibial slope is less angled than the medial tibial slope. Few investigators have distinguished between the tibial plateau osseous slope and the change that would occur in slope if the articular cartilage and meniscus were added to the calculations. The osseous tibial slope is most commonly noted in the literature and is measured from sagittal radiographs. The true tibial slope, which includes the articular cartilage and meniscus, was noted to be 6° less than the osseous tibial slope, according to Jenny and colleagues.⁶⁰

Increasing the tibial slope increases anterior tibial translation and, potentially, tensile loads on the ACL or an ACL reconstruction (Fig. 31-21).³⁰ Conversely, decreasing the tibial slope theoretically would increase tensile loads on the PCL and shift the tibia to a more anterior position. Giffin and coworkers⁴⁴ reported in cadaveric knees that an increase of 5° in the tibial slope produced an anterior shift in the resting position of the tibia (maximum, 3.6 ± 1.4 mm at full extension). However, under a 200-N axial load, there was only a 2-mm anterior shift in the tibiofemoral contact position (30° and 90°) and no increase in ACL forces. The authors concluded that small changes in tibial slope under simulated weight-bearing conditions would have little effect on tibiofemoral position. However, they postulated that larger changes in tibial slope, such as 10°, would cause a greater anterior shift in the tibia resting and loaded positions that might require correction by biplanar osteotomy in knees with ACL injury undergoing HTO.

FIGURE 31-21 The effect of an increase in the tibial slope. The degree of tibial slope is based on proximal tibial anatomic axis (PTAA; Fig. 31-20).

In a second study conducted by Giffin and associates,⁴³ a 5-mm anterior opening wedge osteotomy in PCL-sectioned cadaveric knees was performed and an anterior shift in the tibia resting position of approximately 4 mm was measured. The beneficial effect of an increase in tibial slope in a PCL-deficient knee should be viewed in terms of functional loading conditions, and it is questionable whether the resting no-load position data are applicable to in vivo loading conditions. In this study, under a combined 134-N tibial translation load and 200-N axial compressive load, there was no statistical difference in the amount of posterior tibial subluxation between the PCL-deficient and the PCL-deficient-osteotomy knees. The data show that the tibia reached a similar abnormal posterior tibial position (mean 90° AP translation: intact knee 10 mm; PCL-deficient, 20.6 mm; PCL-deficient-osteotomy, 20.3 mm). The authors concluded that “increasing the tibial slope would improve stability in the PCL-deficient knee”; however, this would be true only for conditions of no posterior tibial loading not expected in functional activities. The data in this study may be viewed from an opposite standpoint to indicate that PCL graft reconstruction is warranted in symptomatic knees, because the opening wedge osteotomy is not effective in preventing posterior tibial subluxation under posterior tibial loading conditions.

In cadaveric knees, Agneskirchner and colleagues² studied the effect of an opening wedge osteotomy combined with a flexion osteotomy (to change the tibial slope) on tibiofemoral contact pressures and the resultant tibiofemoral position. The study reported that the flexion osteotomy shifted the tibiofemoral contact to a more anterior position (15° flexion osteotomy, ∼5 mm, 30° knee flexion), which “neutralized” the effect of sectioning the PCL and reduced pressures of the posterior half of the tibial plateau. The authors suggested in varus-angulated, PCL-deficient knees, with associated posterolateral knee ligament injury and knee hyperextension, that an associated change in tibial slope would have a beneficial effect. Only quadriceps-induced leg extension loading was used, without weight-bearing loads or posterior translational loads to determine the resultant tibiofemoral position under more physiologic loading conditions. The quadriceps loading (to resist the applied external flexion moment) changed with the quadriceps extension force, nearly doubling with the flexion osteotomy (without osteotomy, ∼550 N, with 15° flexion; with osteotomy, ∼1100 N quadriceps applied load). The increased quadriceps loading in fact increased joint contact pressures.

In contrast to the study just discussed, Rodner and coworkers¹²⁰ reported in cadaveric knees that an increase in tibial slope in the ACL-deficient knee at the time of a HTO has the potential to redistribute tibiofemoral contact pressures to a more posterior position on the tibial plateau. From a theoretical standpoint, a redistribution of pressures posterior on the tibial plateau would be detrimental to the long-term success of an HTO in ACL-deficient knees with meniscectomy and posterior tibial plateau articular damage. The cadaver knee studies involved uniaxial loading knee joint loads instead of the quadriceps loading in the study by Agneskirchner and colleagues,² thereby demonstrating the marked effect that in vitro experimental loading conditions have on joint contact pressures and study conclusions.

Brandon and associates¹⁹ measured the tibial slope in 100 ACL-deficient patients and 100 controls and reported that female and male patients had similar tibial slope measurements. ACL-deficient female and male patients had increases in tibial slope (mean values increased 3.6° and 2.4°, respectively), and the high-grade pivot-shift patient group had an increase in tibial slope (mean value increased ∼2°). The measurements show high standard deviations (∼35% of the mean values), and it is probable that the few degrees difference between patient groups is not clinically significant or would result in increased ACL load and anterior tibial displacement.

Dejour and colleagues³² evaluated chronic ACL-deficient knees with monopodal lateral weight-bearing films (knee flexed 20° to 30° with the quadriceps contracted) and compared the anterior tibial translation with the tibial slope. The tibial slope was defined as the angle between the medial tibial plateau and the long axis of the tibia, which had an average value of 6°. The anterior tibial translation was defined as the distance between a parallel line at the posterior medial tibial plateau and a posterior point on the medial femoral condyle. The authors reported a statistically significant relationship between the standing anterior tibial translation and the tibial slope in both normal and chronic ACL-deficient knees. The regression line showed a 6-mm increase in anterior tibial translation for every 10° increase in tibial slope. However, it should be noted that a wide variation was present in the data between knees. For example, in chronic ACL-deficient knees with a tibial slope of 10°, anterior tibial translation varied from approximately –2° to 12°.

Griffin and Shannon⁴² recently summarized the clinical role of HTO with knee ligament instability, showing the benefit of an anterior opening wedge HTO for severe recurvatum and correcting an abnormal increased tibial slope in select patients who had failed multiple ligament reconstructions.

Marti and coworkers⁷⁷ recommended that knees with ACL insufficiency and associated medial arthritis with a tibial slope of 10° or more undergo correction at the time of a varus-producing osteotomy. However, no clinical data were provided to demonstrate whether a change in slope decreased instability symptoms. Other authors³³ discussed increases in ACL tensile loads when tibial slope exceeded 10° and postulated the need for correction, again without clinical data.

Griffin and Shannon⁴² noted that the anterior tibial subluxation with ACL insufficiency results in a “copula” owing to increased damage of the medial plateau; however, the effect of a medial meniscectomy on producing the same effect should be considered.

The authors of this chapter agree with recommendations to correct tibial slope when a distinct abnormality is present (Figs. 31-22 and 31-23). The published literature does not provide objective data regarding the degrees of abnormal increase or decrease in tibial slope when corrective osteotomy is indicated when there is an associated ACL or PCL insufficiency.

FIGURE 31-22 Radiographs of a 52-year-old physician referred for treatment after a closing wedge osteotomy (A) and subsequent ACL bone–patellar tendon–bone autograft (B) that failed. It would have been desirable to correct the abnormal tibial slope, which may have been a factor in the ACL graft failure.

FIGURE 31-23 A and B, Preoperative radiographs of a 24-year-old man with bilateral severe varus angulation with medial joint line pain. C and D, Postoperative radiographs after a biplanar opening wedge osteotomy that was done to correct the abnormal tibial slope. An iliac crest bone graft and locking plate with screws were used in the procedure.

It is probable that a change in AP shear forces, cruciate tensile loads, and tibiofemoral contact under dynamic conditions would not have clinical significance after a 5° change in the tibial slope when the preoperative tibial slope is in the normal range. Therefore, changing the tibial slope to alter the tibiofemoral contact position by a few millimeters to produce an anterior or posterior shift in tibia position (to an area of less cartilage damage) has the theoretical benefits, but has not been proved in clinical studies to be adopted as a treatment recommendation.

There are patients who have a distinctly abnormal tibial slope from a prior osteotomy or tibial fracture or a growth abnormality in which correction of the tibial slope is required prior to cruciate ligament surgery or other conditions discussed. Occasionally, ACL revision patients have an abnormally increased slope that should be corrected prior to repeat ACL surgery. Patients with a severe varus recurvatum require measurement of tibial slope and may fail posterolateral ligament surgery if the normal posterior tibial slope is reversed. Empirically, a tibial slope greater than 2 standard deviations above normal (e.g., a tibial slope of ≥15°) may be considered for correction. In these knees, at the time of HTO, it is possible to decrease the tibial slope to normal or below normal in ACL-deficient knees, or to increase the slope in PCL-deficient knees, to alter loads on the respective cruciate ligament and possibly change the abnormal “resting” tibiofemoral weight-bearing position.

A normal tibial slope should not be increased in ACL-deficient knees or decreased in PCL-deficient knees undergoing a varus-producing opening wedge osteotomy. The rule is described elsewhere in this chapter (Opening Wedge Osteotomy: Preservation of Tibial Slope) that the anterior gap at the medial opening wedge should be one half of the posteromedial gap to maintain a normal tibial slope.¹⁰⁵ For every 1 mm of anterior gap change, an approximately 2° change in tibial slope would be produced. This is based on the angle of the anteromedial tibial cortex, tibial width, and the AP distance where the gap measurement is made (see Table 31-5). It is common in opening wedge osteotomies to incorrectly produce a symmetrical anterior and posterior gap at the osteotomy site, which results in a considerable increase in the tibial slope, potentially leading to a decrease in knee extension and an increase in ACL tensile loads. For example, a change in the tibial slope by 10° would result if an anterior gap measurement error of only 5 mm occurred. The final tibial slope is verified at surgery by lateral fluoroscopic views.

If the surgeon elects to decrease the tibial slope, a staple may be placed at the tibial tubercle while the osteotomy is carefully closed anteriorly to the desired amount. In the senior author’s experience, biplanar corrections require the use of a more secure locking plate design to maintain the correction, because it is necessary to section most of the lateral tibial cortex hinge to close the anterior osteotomy gap (Fig. 31-24). Caution is required when closing the anterior osteotomy gap to apply only gentle hyperextension pressure on the tibia. If any resistance is obtained, it is necessary to further weaken the posterolateral tibial cortex (guide pin penetration) to prevent a lateral tibial plateau fracture just anterior to the remaining posterolateral cortex.

FIGURE 31-24 A and B, A biplanar correction of both the coronal and the sagittal alignment requires the use of a secure locking plate to maintain the correction, because it is necessary to remove more of the lateral tibial cortex hinge in order to close the anterior osteotomy gap.

Song and associates¹²⁷ reported that the normal tibial slope would be maintained if the gap or millimeters of opening along the anteromedial cortex of the anterior plate was two thirds the gap at the location of the posterior plate. The reader should note that the authors are referring to the location of two plates placed along the anteromedial tibial cortex and not the most posterior and anterior gap of the tibial opening wedge discussed in the Noyes and colleagues’ study¹⁰⁵ (anterior gap 50% of posterior gap). The data of the Noyes and colleagues’ study,¹⁰⁵ shown in part in Tables 31-6 and 31-7, allows the gap to be computed along the entire anteromedial cortex. The Song and associates’ study¹²⁷ does not specify where the two plates are placed, and the data in Table 31-7 are more precise to show the actual gap distance where one or two plates would be placed. Further, if the two thirds gap rule of Song and associates were mistakenly applied to the true anterior and posterior gaps along the opening wedge, an increase in tibial slope would occur.

Hohmann and coworkers⁵¹ retrospectively reviewed the radiographs of 67 patients who had a closing wedge HTO and reported a mean decrease of 4.9° in the tibial slope. They suggested that this occurred because of the triangular geometry of the tibia, with more bone removed than required from the anterolateral portion of the lateral tibia.

Timing of Procedures

The timing of HTO and ligament reconstructive procedures is based on several factors (Table 31-4 and Fig. 31-25). In primary varus knees that do not demonstrate abnormal lateral joint opening and external tibial rotation, the HTO and cruciate reconstruction may be performed at the same setting.⁹³ In double and triple varus knees, the ligament reconstructive procedures are performed after the HTO to reduce the risk of complications.¹⁰⁰ Prolonged rehabilitation and an increased risk of knee arthrofibrosis and motion problems have been described after HTO and ligament reconstructive procedures are performed simultaneously.^18,69,133

FIGURE 31-25 Timing of HTO and knee ligament reconstructive procedures.

(Reprinted with permission from Noyes, F. R.; Barber-Westin, S. D.: Revision anterior cruciate surgery with use of bone–patellar tendon–bone autogenous grafts. J Bone Joint Surg Am 83:1131–1143, 2001.)

The authors prefer to perform the HTO first and, after adequate healing of the osteotomy, the required ligament reconstructive procedures. In ACL-deficient double varus knees, an increase in the lateral tibiofemoral joint gap test contraindicates ACL reconstruction. HTO is effective in decreasing abnormal loads in the lateral and posterolateral tissues, allowing physiologic remodeling and shortening to occur, particularly when the deficiency of the posterolateral structures is only moderate (5–8 mm increased lateral joint opening, 10° increased external tibial rotation).^93,100 In a study conducted by the authors,⁹³ described later in this chapter (Authors’ Clinical Studies), 22 of 41 double varus knees (54%) had abnormally increased lateral joint opening on varus stress testing before osteotomy. Of these, only 5 (12%) had this abnormal joint opening at follow-up. A FCL and posterolateral reconstruction was avoided in these patients. In this same study, a subgroup of 11 patients (27%) did not require ACL reconstruction, because instability symptoms did not exist after the HTO.⁹³

In triple varus knees, the ACL and posterolateral structures are reconstructed after the HTO to allow all ligament structures to function together to resist anterior subluxation, abnormal lateral tibiofemoral joint opening, and varus recurvatum. These represent major surgical procedures that are always staged and not combined with the HTO.

Cruciate Graft Options

A four-strand semitendinosus-gracilis (STG) autograft may be harvested from the involved side with little morbidity. Most patients undergoing HTO will not be involved in strenuous athletics, and a STG autograft provides suitable stability for light recreational activities. In revision knees, an STG graft may be used if there are no enlarged femoral or tibial tunnels.

A bone–patellar tendon–bone (B-PT-B) autograft is preferred if there is gross anterior subluxation (grade III pivot shift). In knees undergoing revision ACL reconstruction in which the ipsilateral patellar tendon was previously harvested, the contralateral B-PT-B graft or the ipsilateral quadriceps tendon–patellar bone (QT-PB) graft is a preferred substitute.^94,98 However, care must be taken when harvesting these autografts from the same knee at the time of the osteotomy. The opposite knee may be used for graft harvest.

The use of allografts for ACL reconstruction is controversial owing to the higher graft stretch-out and failure rates compared with B-PT-B autografts, as discussed in detail in Chapter 7, ACL Primary and Revision Reconstruction: Diagnosis, Operative Techniques, and Clinical Outcomes.^90–92,101 If an allograft is required, the B-PT-B has an advantage of more secure bone fixation.

Graft preferences for PCL reconstruction are a two-strand QT-PB autograft or allografts, further described in Chapter 21, Posterior Cruciate Ligament: Diagnosis, Operative Techniques, and Clinical Outcomes.^95,97 The options for surgical restoration of deficient posterolateral structures are described in Chapter 22, Posterolateral Ligament Structures: Diagnosis, Operative Techniques, and Clinical Outcomes.

Opening versus Closing Wedge Osteotomy

The two most common operative techniques for correcting a varus deformity are the opening and the closing wedge tibial osteotomies. An opening wedge avoids the lateral dissection and fibular osteotomy. Knees that require a large angular correction of greater than 12° are candidates for the opening wedge procedure, because it avoids excessive tibial shortening.

Opening wedge osteotomy is advantageous in knees that have chronic medial ligamentous deficiency (MCL, posteromedial capsule), in which a distal advancement or reconstruction of the MCL is required. Knees with rupture of the posterolateral structures requiring posterolateral reconstruction are candidates for opening wedge osteotomy in order to avoid a proximal fibular osteotomy, because a FCL graft will be anchored to the proximal fibula. Opening wedge osteotomy is advantageous in cases of patella alta or decreased lower limb length that would be made worse by a closing wedge osteotomy. A patella infera is a contraindication for an opening wedge osteotomy. A significant patella alta is a relative contraindication for a closing wedge osteotomy.

The major disadvantage of an opening wedge osteotomy is that an appropriate structural corticancellous autograft or allograft is required to restore the anteromedial and posteromedial cortex, add fixation strength, and promote osseous union. Autogenous bone grafting of the open defect aids in achieving stability at the osteotomy site and promoting prompt union with reduced risk of varus collapse due to a delayed union. The potential for many weeks of crutch protection and added disuse effects of the lower limb is lessened by the autogenous grafting. The limited invasive procedure to obtain the outer iliac crest cortical cancellous autograft is discussed in detail in this chapter (Operative Technique: Opening Wedge Tibial Osteotomy).

Several opening wedge plate designs are available. The authors prefer a tibial plate with locking screws to achieve secure osseous fixation.¹²⁹ The reader is referred to the appropriate literature by the respective manufacturer, because each locking plate design is different and the recommended technique must be followed. There are rules that must be followed to avoid changing the tibial slope with the use of any fixation plate. A greater chance of increasing the posterior tibial slope exists if an opening wedge buttress plate is placed in an anterior position.²¹ With attention to this problem at surgery, the normal tibial slope in the sagittal plane can be preserved with any of the available plate designs.¹⁰⁵

A disadvantage of an opening wedge osteotomy is that transection of the superficial distal attachment of the MCL is required. In an opening wedge osteotomy of 5 mm, the MCL fibers may be incompletely transected at several different levels (pie-crust approach) to lengthen the ligament. However, osteotomies entailing a correction greater than 5 mm require distal MCL sectioning, careful reflection from the osteotomy site, and reattachment.

The closing wedge osteotomy has the advantage of faster healing and early resumption of weight-bearing because contact of two large cancellous surfaces of the proximal tibia is achieved. The initial interval fixation of the osteotomy is more secure than an opening wedge procedure, and there is less chance for a change in osteotomy position and loss of correction. It is more difficult (compared with the opening wedge technique) to achieve or change the desired amount of bone resection to obtain accurate angular alignment correction at surgery.

The closing wedge osteotomy involves more soft tissue dissection. Osteotomy of the fibula is preferred at the proximal fibular neck region. The lateral dissection must be meticulous to avoid the peroneal nerve. It is more tedious to resect more bone and alter the lower limb valgus correction should it be necessary to achieve additional angular correction. The triangular bone wedge is removed and saved should it be necessary to reinsert bone if an overcorrection is identified at surgery.

Brouwer and associates²² conducted a prospective clinical trial in 92 patients randomized to either an opening wedge (Puddu plate) or a closing wedge osteotomy. At 1 year postoperatively, a valgus alignment (defined as 0°–6° valgus) was noted in 79% of the closing wedge osteotomies compared with 56% of the closing wedge osteotomies. The authors concluded that the Puddu plate had insufficient strength to maintain the operative correction. The investigation had several flaws because it involved four surgeons and hip-knee-ankle radiographs were not obtained in the initial postoperative period. The number of opening wedge osteotomies that received autogenous bone grafting was not provided. The results emphasize the importance of determining that the appropriate valgus correction is achieved at surgery and maintained in the early postoperative period until union has occurred. The failure to achieve the desired valgus alignment would be expected to decrease long-term success rates. Full-standing weight-bearing hip-knee-ankle radiographs may be obtained by 3 to 4 weeks postoperative after either opening or closing wedge osteotomy to verify that correction has been achieved. In a small percentage of cases in which the correction is found not to be ideal on early postoperative radiographs, a revision angular correction may then be performed.

The use of an external fixator has been advocated with tibial osteotomy, with the advantage of allowing adjustments in lower limb alignment that is helpful in difficult or biplanar corrections.^130,139 A disadvantage of an external fixator is the risk of pin tract infection^74,130,139 and the 12-week period of time that the fixator is typically used. The use of an external fixator is ideal when both coronal lower limb alignment and tibial rotation need to be corrected.

Opening Wedge Osteotomy: Preservation of Tibial Slope

On cross-section, the proximal anteromedial tibial cortex has an oblique or triangular shape, whereas the lateral tibial cortex is more perpendicular at the posterior margin of the tibia. Because of this relationship, a medial opening wedge osteotomy that has an anterior tibial tubercle width equal to the width at the posteromedial margin would increase tibial slope, decrease knee extension, and possibly increase ACL tensile loads. A lateral closing wedge osteotomy with an equal anterior-to-posterior width or gap along the lateral tibial cortex tends to decrease the tibial slope by a few degrees, as is described next.

A study was conducted using three-dimensional analysis of the proximal tibia to determine how the angle of the opening wedge along the anteromedial tibial cortex influences the tibial slope (sagittal plane) and valgus correction (coronal plane) when performing a medial opening wedge osteotomy.¹⁰⁵

The data in this study on the obliquity of the anteromedial cortex of the proximal tibia relative to the posterior tibial cortex (Fig. 31-26) are presented from 35 magnetic resonance imaging (MRI) films in healthy young individuals (mean age, 32.7 yr).¹⁰⁵ Serial CT images of a cadaveric tibia were made in 1.25-mm slices and digitized using a computer-aided design package to create a solid model of the proximal tibia.

FIGURE 31-26 An axial cut of the proximal tibia at the diaphyseal-metaphyseal junction. The angle formed by the intersection of the mediolateral axis along the posterior tibia and the axis along the anteromedial tibial cortex is called the anteromedial cortex oblique angle (θ). This angle measures approximately 45° to the coronal plane.

A medial opening wedge osteotomy was created along the AP axis to include a hinge axis on the lateral margin of the tibia. The open wedge osteotomy was just proximal to the tibial tubercle, ending 20 mm below the cortical margin of the lateral tibial plateau. The distal portion of the tibia was rotated on the virtual model about the hinge axis through the lateral point of the osteotomy, maintaining the anatomic tibial slope (sagittal plane). Measurements of the width of the wedge angle and gap angle (Fig. 31-27) along the anteromedial tibial cortex were made from the resulting computerized model. Standard algebraic calculations were made using the law of triangles to determine the effect of different degrees of opening wedge osteotomy on coronal (valgus) and sagittal (tibial slope) alignment.

FIGURE 31-27 The distal portion of the tibia was rotated about an AP axis, which ran through the hinge point of the osteotomy to maintain the posterior tibial slope. A solid model of a high tibial osteotomy plate was placed at a series of positions around the medial aspect of the tibia, just anterior to the medial collateral ligament. The anteromedial cortex wedge angle is that angle formed along the oblique anteromedial tibial cortex during a prescribed opening wedge osteotomy (coronal plane). The gap angle is formed by planes that are perpendicular to the wedge angle along the anteromedial tibial surface.

The MRI measurement of the anteromedial tibial cortex oblique angle at the site of the opening wedge osteotomy was 45° ± 6° (range, 34°–56°). The opening wedge angle, along the anteromedial tibial cortex to maintain the tibial slope, was found to be dependent on the angle of coronal valgus correction (HTO coronal angle) and the angle of obliquity of the anteromedial tibial cortex. In Figure 31-28, the results are shown for the calculation of the opening wedge angle (along the anteromedial tibial cortex) for five different osteotomy corrections in the coronal valgus plane (2.5°–12.5°).

FIGURE 31-28 The anteromedial cortex opening wedge angle depends on the oblique angle of the tibial cortex with respect to the hinge axis. Each line represents the desired calculated degrees of correction for the opening wedge osteotomy in the true coronal (90°) plane.

(Reprinted with permission from Noyes, F. R.; Goebel, S. X.; West, J.: Opening wedge tibial osteotomy: the 3-triangle method to correct axial alignment and tibial slope. Am J Sports Med 33:378–387, 2005.)

The gap angle is perpendicular to the anteromedial oblique surface of the tibia with a vertex on the hinge axis posterior to the tibia. This is shown in Figure 31-29, in which the gap angle in degrees is shown for five different osteotomy corrections as a function of the obliquity of the anteromedial tibial cortex.

FIGURE 31-29 The magnitude of the gap angle changes with the obliquity of the anteromedial tibial cortex angle. Each line represents the calculated degrees of correction for the opening wedge osteotomy in the coronal plane.

(Reprinted with permission from Noyes, F. R.; Goebel, S. X.; West, J.: Opening wedge tibial osteotomy: the 3-triangle method to correct axial alignment and tibial slope. Am J Sports Med 33:378–387, 2005.)

As an example, a 10° coronal valgus correction (assuming a normal 45° obliquity of the anteromedial tibial cortex) would result in a 7° gap angle at the osteotomy site. An error in the anteromedial tibial cortex opening wedge angle would result in an error in the tibial slope. An example of this is shown in Figure 31-30, which represents the desired wedge angle for a 10° coronal correction. An equal anterior and posterior opening or gap at the osteotomy site would result in an increased tibial slope and loss of normal knee extension.

FIGURE 31-30 Left, Appropriate choice of the wedge angle to maintain the sagittal tibial slope. Right, Inappropriate wedge angle results in increased tibial slope.

These variables are shown in Table 31-5. For example, an error of 5 mm in the Y₂ gap (Fig. 31-31) at the tibial tubercle, assuming the length of the anteromedial cortex (L) is 45 mm, would result in an unexpected change in the tibial slope of 10°. As a general rule in this example, every millimeter of alteration in the gap height induces a change of 2° in the tibial slope.

FIGURE 31-31 The opening wedge angle along the anteromedial tibial cortex can be calculated using the three linear measurements along the osteotomy opening wedge. Y₁, gap anterior to Y₂; Y₂, posterior gap; L, length between Y₁ and Y₂.

The opening wedge angle can be set at surgery by measuring and altering the vertical gap (width) at two points along the osteotomy site, Y₁ and Y₂ (Fig. 31-32). This has importance in determining that the correct wedge angle is obtained prior to internal fixation at the osteotomy site. The site at which the vertical gap measurement is taken depends on the coronal distance from the hinge axis, obliquity of the anteromedial tibial cortex, and the distance along the osteotomy site on the anteromedial surface (Tables 31-6 and 31-7).

FIGURE 31-32 Vertical gap measurements of the opening wedge osteotomy are a function of distance from the hinge axis of the lateral tibial cortex for the opening wedge (X₁, X₂), oblique angle of the anteromedial tibial cortex (θ), and distance along the osteotomy site (L).

(Reprinted with permission from Noyes, F. R.; Goebel, S. X.; West, J.: Opening wedge tibial osteotomy: the 3-triangle method to correct axial alignment and tibial slope. Am J Sports Med 33:378–387, 2005.)

In Table 31-6, the millimeters of opening at the osteotomy site are based on the width of the tibia and the angle of correction. In Table 31-7, an average 45° oblique angle of the anteromedial cortex and a tibial width of 60 mm are assumed. This allows the surgeon to calculate at the time of surgery the desired gap height at two points along the osteotomy to maintain the tibial slope.

For example, the measurement of the posterior tibial width is made at the osteotomy site (X₁). The opening height at the most posteromedial point (Y₁) and the distance between the two measurement points (Y₁–Y₂) are used in Table 31-7 to determine the second opening height at a defined distance (L) along the osteotomy site to maintain tibial slope.

If the tibial plate is placed just anterior to the superficial MCL on the anteromedial tibial cortex, approximately 20 mm anterior to the most posteromedial point of the osteotomy, the osteotomy gap at this site can be determined. In Table 31-7, with a 10-mm posteromedial opening (Y₁), the correct width at the tibial plate would be 7.6 mm (tibial width, 60 mm).

For a 12-mm posteromedial opening, the correct width of the gap at the tibial plate would be 9.2 mm. A wider gap at the tibial plate would result in excessive valgus alignment and altered tibial slope. The change in the oblique angle of the anteromedial cortex, within the standard deviations reported, would have only a small and negligible effect on the width measurements of the opening wedge (see Table 31-7). To maintain the proper anterior and posterior gaps at the osteotomy site, appropriate distraction instruments at surgery are required to maintain the desired coronal and sagittal angular correction.

Final Recommendations to Obtain Correct Coronal and Slope Alignment

Step 1: Initial Operating Room Preparation

Preoperative calculations are made as previously described. The entire lower extremity is prepared and draped free with the tourniquet placed high on the proximal thigh to assist visual observation of lower limb alignment. If an autogenous iliac crest autograft is to be performed (authors’ choice), the ipsilateral anterior iliac crest is prepared and draped for the limited iliac crest bone harvest of the outer cortex. The patient is positioned to allow fluoroscopic views of the hip-knee-ankle WBL to verify the angular correction at surgery, and lateral views are obtained for tibial slope analysis.

Step 2: Knee Arthroscopy

Arthroscopy is performed at the time of the HTO to evaluate articular surfaces of the medial and lateral tibiofemoral compartments and patellofemoral joint to confirm that the patient is an appropriate candidate for the osteotomy. ACL-deficient knees may have associated meniscus tears that require repair¹²² or partial removal. Appropriate débridement of tissues, inflamed synovium, and notch osteophytes limiting knee extension is performed. In particular, a secondary weight-bearing area is established in varus-angulated knees in which the lateral tibial spine produces a bone erosion over the inner margin of the lateral femoral condyle. The femoral condylar bone erosion may be débrided to remove the painful weight-bearing site.

Step 3: Anterior Iliac Crest Bone Graft Harvest

A 4-cm incision is made over the anterior iliac crest and deepened to the periosteum (Fig. 31-34), which is sharply incised and reflected medially only to the inner cortex. Laterally, meticulous subperiosteal dissection is carried along the outer table of the pelvis, avoiding the lateral muscles. The graft size is defined on the outer cortex using electrocautery. In most patients, the graft will be 40 mm in length, 10 mm in width, and 30 mm in depth. However, in smaller patients, the graft may be smaller in width and approximately 8 mm in depth. Patients undergoing large osteotomies may require a longer graft of approximately 45 mm to 50 mm.

FIGURE 31-34 A, A 4-cm incision over the anterior iliac crest is made to harvest the iliac crest bone graft. The graft is composed of the anterior crest and outer iliac cortex; the inner table is not removed. B, The usual iliac crest bone graft dimensions are 40 mm in length, 10 to 12 mm in width, and 30 mm in depth.

(A and B, Reprinted with permission from Noyes, F. R.; Mayfield, W.; Barber-Westin, S. D.; et al.: Opening wedge high tibial osteotomy: an operative technique and rehabilitation program to decrease complications and promote early union and function. Am J Sports Med 34:1262–1273, 2006.)

Critical Points OPERATIVE TECHNIQUE OPENING WEDGE OSTEOTOMY

• Arthroscopy prior to HTO to assess all knee compartments, confirm HTO indicated, treat meniscus tears and notch osteophytes blocking knee extension.

• Anterior iliac crest meticulous dissection, remove outer cortex, do not disturb inner cortex or muscle attachments.

Harvest graft 40 mm in length, 10 mm in width, 30 mm in depth to produce three triangular bone grafts.

• HTO incision: 5 cm vertical medial tibia midway between tibial tubercle and posteromedial tibial cortex, starting 1 cm inferior to joint line.

• Partially detach gracilis and semitendinosus tendons at their tibial insertion, retract posteriorly exposing SMCL and posterior border of the tibia.

• Sharp periosteal incision anterior and posteromedial tibial border of the SMCL, meticulous subperiosteal dissection beneath the SMCL fibers. Protect inferior medial geniculate artery beneath the SMCL.

• Posterior tibial subperiosteal dissection to protect neurovascular structures. Wide dissection not necessary. Surgeon’s headlight always used.

• Small osteotomies ≤ 5 mm, “pie-crust” procedure using multiple transverse incisions may effectively lengthen SMCL.

• Osteotomies > 5 mm, transect distal SMCL attachment, carefully elevated to the tibial border, protected and reattached after osteotomy.

• Keith needle placed anteriorly and posteriorly at the joint space to verify the tibial slope and medial sagittal osteotomy plane.

• Anterior and posterior guide pins placed at slight obliquity to tibial shaft (∼15°), verify position with fluoroscopy, mark osteotomy line along the anteromedial cortex.

• Ensure guide pins are at least 20 mm distal to the lateral joint line to prevent lateral tibial plateau fracture.

• Begin osteotomy with oscillating saw for medial and anterior cortices. Follow by nonflexible thin ¾-inch osteotome placed anterior, directly above the guide pin, verified by fluoroscopy.

• Use ½-inch osteotomy for posterior cortex, with osteotome edge visualized and palpated posterior to the tibia as the osteotomy is advanced.

• Carry osteotomy to within 10 mm of the posterolateral cortex, confirm by fluoroscopy.

• Place thin spreader bars across osteotomy. Initial distraction requires several minutes to prevent fracture of the lateral cortex; if major resistance, place holes in lateral cortex with guide pin.

• Anterior gap of osteotomy should be half that of the posterior gap to maintain tibial slope. Maintain osteotomy gap; use anterior tibial staple, if necessary, and posterior wedge; confirm alignment by fluoroscopy.

• Apply and fixate locking plate with fluoroscopy verification, confirm final coronal and sagittal (slope) alignment.

• Suture SMCL fibers distally and secure to either plate screws or suture anchors to maintain tension. Reapproximate pes anserine tendons and sartorius fascia.

• Knees with chronic SMCL deficiency require distal advancement if the ligament appears normal without scar replacement.

• Semitendinosus augmentation of SMCL required in knees with scar replacement.

• When the SMCL is advanced distally or reconstructed, incise, reset, and repair medial meniscus attachments.

HTO, high tibial osteotomy; SMCL, superficial medial collateral ligament.

The inner iliac cortex is not dissected, the muscle attachments are not disturbed, which reduces postoperative pain, and a spacer of the iliac crest defect is not required. Additional cancellous bone is removed from the inner graft site. A drain is not required at the iliac crest harvest site. The wound is closed in layers with deep sutures to close the dead space. The graft is later fashioned into three carefully sized triangles: one triangle is placed posterior to the tibial plate to close the gap at the posterior tibial cortex, one triangle is placed in the midportion of the osteotomy deep to the plate, and one smaller-width triangle is placed in the gap in the anterior tibial cortex. In large osteotomy corrections (>10-mm gap), autogenous bone is always used and any remaining defect filled with corticocancellous freeze-dried tibial or iliac crest allografts.

Step 4: Initial Anteromedial Tibial Approach

The operative technique is shown in Figure 31-35. A 5-cm vertical skin incision is made medially midway between the tibial tubercle and the posteromedial tibial cortex, starting 1 cm inferior to the joint line. A vertical incision is preferred over an oblique or transverse incision because vertical incisions are subsequently used in knees progressing to partial or complete TKA. The sartorius fascia is incised in line with its fibers, proximal to the gracilis tendon, exposing the distal SMCL attachment.

FIGURE 31-35 A, Initial draping of the varus-aligned lower extremity with the right iliac crest draped for bone graft. B, Incision location, anterior third of the medial tibia. C, Initial exposure beneath the patella tendon under retraction. D, Initial subperiosteal dissection of the superficial medial collateral ligament (SMCL). The distal attachment has been incised. E, Posterior subperiosteal exposure to protect the neurovascular structures. F, Placement of the navigation femoral and tibial markers. G, A Keith needle placed at the anterior, and later the posterior, aspect of the joint line is used to outline the planned osteotomy. H, Two guide pins are placed under fluoroscopic control. I, A thin osteotomy blade is placed under fluoroscopic control. Different width blades are used to complete the osteotomy within 8 mm of the lateral cortex. J, Initial posterior cortex osteotomy using a thin power saw under direct visualization. K, Completion of the posterior cortex osteotomy to within 8 mm of the posterolateral cortex. L, Initial gentle dislocation of the osteotomy. M, Guide pin perforation of the dense posterolateral tibial cortex to weaken the bone owing to failure of the osteotomy gap to increase under gentle dislocation. N, Further dislocation of the osteotomy site. O, Use of computerized navigation to monitor valgus alignment. P, Staple is placed anterior to the tibial gap to control tibial slope. Q, Initial fixation of the osteotomy, maintaining the measured osteotomy correction. R, Confirmation of the anterior and posterior osteotomy gap measurement. S, Bicortical iliac crest autografts. T, Placement of the anterior, central and posterior iliac crest autografts. U, Fixation of the anterior border of the SMCL to the tibial plate.

The gracilis and semitendinosus tendons are partially detached at their tibial insertion in an L-shaped manner and retracted posteriorly to further expose the SMCL and posterior border of the tibia. The SMCL is transected at its most distal tibial attachment. Anteriorly, the retropatellar bursa is entered by incising the medial patellar retinaculum, allowing the patellar tendon to be lifted to expose the anterior tibia.

A sharp periosteal incision is made at the posteromedial tibial border, just posterior to the SMCL, to allow the distal SMCL to be dissected subperiosteally in a proximal direction and to allow meticulous posterior tibial subperiosteal dissection by a Cobb elevator. Care is taken to identify the inferior medial geniculate artery, which lies just beneath the SMCL. Only sufficient posterior tibial subperiosteal dissection is used to protect the neurovascular structures; wide dissection is not necessary. A malleable retractor is placed in the subperiosteal posterior tibial space.

Step 5: Proximal Osteotomy and Placement of Tibial Guide Pins

The patellar tendon and retropatellar bursa are exposed medially. The superior attachment of the tendon is recessed 5 mm using a scalpel to provide adequate exposure for the osteotomy. Retractors are placed anteriorly and posteriorly to complete the exposure. A Keith needle is placed in the anteromedial joint just above the tibia, and the distance is marked on the desired point of the osteotomy along the anteromedial cortex. A second Keith needle is placed at the posteromedial tibial joint space, and the same millimeters are marked to provide a measurement of the tibial slope. The two marks are connected to provide the osteotomy line perpendicular to the tibial slope.

A commercial guide system (Arthrex Opening Wedge Osteotomy System, Arthrex Inc., Naples, FL) may be used to facilitate guide wire placement (Fig. 31-36). A 2-mm guide pin is placed at the posteromedial cortex at the marked line and advanced across the tibia at an oblique angle. The anterior and posterior guide pins are placed at 15° of obliquity to the tibial shaft and verified by intraoperative fluoroscopy. An alternative technique is to place the site of the osteotomy directly above the posterior guide pin, maintaining the oblique angle of the pin across the osteotomy site without using the osteotomy guide system.

FIGURE 31-36 A–D, Correct placement for guide pin and subsequent osteotomy with a thin osteotome. The lateral cortex is preserved.

(A–D, Reprinted with permission from Noyes, F. R.; Barber-Westin, S. D.; Roberts, C. S.: High tibial osteotomy in knees with associated chronic ligament deficiencies. In Jackson RW [ed.]: Master Techniques in Orthopaedic Surgery, Reconstructive Knee Surgery. Philadelphia: Lippincott Williams & Wilkins, 2003; pp. 229–260.)

To prevent a fracture extending into the joint at the lateral tibial plateau, it is important for the guide pins to be at least 20 mm distal to the lateral joint line. An error that may occur is to have too much obliquity to the guide pin.

At this point, it is imperative to ensure that the medial osteotomy line (from anterior to posterior) is in line with the tibial slope based on the radiographs and prior anteromedial cortex joint line measurements by the Keith needles. A measurement of the perpendicular cut from the joint line confirms the distance of each guide pin from the articular surface of the tibia. The length of the posterior pin (medial to lateral cortex) is measured and used following the law of triangles¹⁰⁵ to determine tibial width and the millimeters of osteotomy opening to obtain the desired angular correction (see Table 31-6).

The osteotomy is initially performed using an oscillating saw for the medial and anterior cortices, followed by a nonflexible, thin ¾-inch and ½-inch osteotome, placed in the same orientation and anterior to the guide pin and verified by fluoroscopy. The lateral cortex is osteotomized to Gerdy’s tubercle, leaving the posterolateral tibial cortex hinge. A ½-inch osteotome is used for the posterior cortex, with the osteotome exposed 2 to 3 mm and viewed posterior to the tibia as the osteotome is advanced. The osteotomy is carried to within 10 mm of the posterolateral cortex. It is imperative that the lateral cortex not be fractured because this would produce loss of the lateral cortex buttress and potential collapse and loss of the angular correction. If a fracture of the lateral cortex does occur, with gross instability to the osteotomy site, the lateral tibial cortex may be secured with a two-hole small plate through a limited lateral incision to achieve stability.

Step 6: Opening Wedge Technique and Measurement of Gaps to Confirm Tibial Slope

Commercially available calibrated opening wedges are gently inserted into the osteotomy site to achieve the desired angular correction with the opening medial gap hinging on the intact posterolateral cortex (Fig. 31-37). This step requires several minutes to prevent fracture of the lateral tibial pillar. The spreader bars are inserted entirely across the osteotomy site to prevent a fracture extending into the lateral tibial plateau. If there is a rigid nonyielding response to the spreader bars, the lateral cortex is weakened with three to four guide pin perforations.

FIGURE 31-37 A and B, The use of a commercial (Arthrex Opening Wedge Osteotomy System, Arthrex, Inc., Naples, FL) osteotomy wedge to gradually open the osteotomy site.

(Reprinted with permission from Noyes, F. R.; Barber-Westin, S. D.; Roberts, C. S.: High tibial osteotomy in knees with associated chronic ligament deficiencies. In Jackson RW [ed.]: Master Techniques in Orthopaedic Surgery, Reconstructive Knee Surgery. Philadelphia: Lippincott Williams & Wilkins, 2003; pp. 229–260.)

The anterior gap of the osteotomy site should be one half of the posterior gap, following rules previously described to maintain the tibial slope.¹⁰⁵ The width of the tibial plate along the anteromedial cortex and just anterior to the SMCL is measured and is always less than the millimeters at the posterior medial gap owing to the angular inclination of the anteromedial tibial cortex.

In select cases as previously described, the tibial slope may be purposefully increased in PCL-deficient knees, decreased in ACL-deficient knees, or altered with abnormal knee hyperextension or flexion contracture. The method to complete the desired change in tibial slope and corresponding width of the anterior and posterior osteotomy sites has been presented in an earlier section of this chapter. A locking plate design is always used in single and biplanar corrections.

Step 7: Intraoperative Verification of Desired Limb Alignment Correction

In addition to preoperative measurements of axial alignment (obtained from double-stance hip-knee-ankle radiographs) and calculations to correct for increased lateral joint opening as previously described, the surgeon must verify intraoperatively that the desired limb alignment has been achieved. After the selected wedge correction (which is maintained using one of the commercial wedge-shaped instruments), a small pad is positioned behind the knee to avoid hyperextension and the knee is placed in 5° flexion. With the lower limb lying on the table, the surgeon gently determines that there is closure of both the medial and the lateral tibiofemoral compartments viewed by fluoroscopy. An axial load is placed across the bottom of the foot to compress the knee joint in order to maintain the correct axial alignment. The lower limb is positioned in 12° to 15° of external rotation to simulate the normal lower limb position during gait. A rigid rod is placed at the center of the hip to the center of the ankle, verified by fluoroscopy, and the WBL at the tibia is determined. Adjustment in the millimeters of gap at the osteotomy site is made to obtain the preoperatively selected WBL. The procedure is repeated after internal plate fixation to verify the final alignment correction. The fluoroscopic technique for lower limb positioning to obtain accurate WBL measurements and verify the operative correction does take time and may require repeated steps. The lateral fluoroscopic view determines the final position of the tibial slope. The role of computer navigation is discussed later in this chapter (Role of Computerized Navigation for HTO).

Obtaining an alignment correction in which the WBL is transferred to the lateral tibiofemoral compartment within the desired 50% to 62% range is the key to achieving short- and long-term decreases in pain in the medial tibiofemoral compartment. The surgeon cannot simply rely on the preoperative calculations because the intraoperative hip-knee-ankle fluoroscopic measurements may indicate that the desired correction of the tibial WBL has not been achieved. This problem was demonstrated in a report by Marti and coworkers,⁷⁷ who described the accuracy of obtaining the desired alignment correction using preoperative and postoperative double-stance radiographs after opening wedge osteotomy in 32 knees. In their series, only 50% of the limbs demonstrated the desired correction on postoperative radiographs (±5° of calculated correction). An undercorrection was found in 31% and an overcorrection in 19%. The authors did not report on the use of intraoperative fluoroscopy to verify the lower limb correction. Many authors have described problems in obtaining the desired angular correction at surgery, with a substantial percentage of limbs remaining in varus or overcorrected into excessive valgus. The development of computerized navigation techniques to increase the accuracy of obtaining the desired tibial WBL and slope correction is, in the authors’ opinion, distinctly advantageous. Both fluoroscopy and computerized navigation techniques require defining accurate anatomic landmarks and precision to obtain accurate measurements.

Step 8: Placement of Bone Graft and Internal Fixation

An appropriate plate is selected and secured. The senior author uses only a locking plate design. If the surgeon elects to use allograft bone, added fixation is required for a longer period of time and a locking plate with screws is strongly recommended to prevent varus collapse at the osteotomy site. Various commercial locking plates and screw systems are available that provide added stability at the operative site.

The senior author recommends structural corticocancellous wedge bone grafts (autograft or allograft) and believes that synthetic grafts or cancellous grafts require further clinical evaluation before being accepted into practice. The clinical studies using these grafts have shown an unacceptable nonunion rate, as is discussed later in this chapter. The author prefers autograft iliac crest grafts or freeze-dried tibia or iliac crest corticocancellous allografts supplemented with a platelet gel.²⁹

The three corticocancellous bone graft triangular segments are fashioned based on direct measurements of the anterior and posterior widths at the osteotomy site. The three grafts are impacted tightly into the posterior, middle, and anterior portions of the osteotomy site to obliterate the space and provide added stability, particularly in the sagittal plane. Fluoroscopy is used to confirm the final alignment and tibial slope.

The SMCL fibers are sutured distally and secured either to the plate screws or to suture anchors to maintain tension. The pes anserine tendons and sartorius fascia are reapproximated. A Hemovac drain is rarely required. The tourniquet is deflated and hemostasis obtained. The wound is closed in layers in the usual manner. The lower limb is wrapped with cotton, and additional padding is placed posteriorly and over the peroneal nerve. A commercial ice delivery system with the bladder incorporated a few cotton layers from the wound is always used. A postoperative hinged brace and bilateral ankle-foot compression boots are applied.

The neurovascular status is immediately checked in the operating room and over the initial postoperative period. The importance of limb elevation for the 1st postoperative week and use of a venous compressive system is emphasized. Close observation for lower limb soft tissue swelling is mandatory. There is a high suspicion for a venous thrombosis, and therefore, aspirin is prescribed. There is also a low threshold for venous ultrasound of both lower extremities, which is obtained in the majority of patients in the first 3 to 7 postoperative days.

Management of the SMCL

There are three surgical approaches for management of the SMCL. In a small opening wedge osteotomy of 5 to 7 mm, a “pie-crusting” procedure using multiple transverse incisions at different places may effectively lengthen the SMCL. In larger opening wedge osteotomies, it is necessary to transect the distal attachment and perform a distal elevation of the attachment in a subperiosteal plane. This allows for the SMCL to be reattached distally after the opening wedge osteotomy with the posteromedial portion of the SMCL bridging the osteotomy site. Transecting the SMCL at the most distal attachment site preserves its length, allows excellent exposure and bone grafting, and allows the tibial fixation plate to be placed in a correct midline position. The tibial slope is not altered, and function of the SMCL is retained.

A third approach is used when distal advancement of the SMCL is required as a reconstructive procedure owing to SMCL insufficiency and abnormal medial joint opening. At the conclusion of the osteotomy and plate fixation, the SMCL is dissected to the medial joint, including the deep medial fibers. A posterior incision is made at the junction of the SMCL and posteromedial capsule (posterior oblique ligament). The anterior incision extends only to the joint and preserves the attachment of the medial patellofemoral ligament. The medial meniscus position is carefully examined when a distal advancement of the SMCL is performed. It may be necessary to incise the medial meniscus capsular attachment and then resuture the attachment to preserve the correct anatomic location of the meniscus when the SMCL is advanced.

The SMCL should appear relatively normal without scar replacement, because advancement of only scar tissue would not provide medial stability. In select cases, an STG augmentation of the SMCL may be necessary. The tendon is detached proximally and passed through a small drill hole at the femoral attachment anterior and posterior to the SMCL femoral attachment. The anterior and posterior tendon arms are sutured to the anterior and posterior fibers of the SMCL after the osteotomy is completed. The distal attachment of the tendons is not disturbed. Added tibial fixation at the distal tendons into the bone at the distal tibia may be required.

The need to surgically reconstruct the SMCL is infrequent; however, the surgical techniques presented allow for restoration of function when required. At the conclusion of the SMCL reconstruction, plication of the posteromedial capsule anteriorly to the SMCL is performed to remove any abnormal capsular laxity with the knee at full extension. Overtightening of the SMCL and posteromedial capsules is avoided. The repair allows for full knee extension and a normal range of flexion. The technique is described in further detail in Chapter 24, Medial and Posteromedial Ligament Injuries: Diagnosis, Operative Techniques, and Clinical Outcomes.

Step 1: Initial Operating Room Preparation and Arthroscopy

The entire lower extremity is prepared and draped free with the tourniquet placed high on the proximal thigh to assist visual observation of lower limb alignment. The patient is positioned to allow fluoroscopic views of the hip-knee-ankle WBL in order to verify the angular correction at surgery, and arthroscopy is performed as already described.

Step 2: Initial Anterolateral Tibial Approach

A sterile tourniquet is inflated, and an oblique incision is made 1 cm distal to the head of the fibula in a line directed to the center of the tibial tubercle (Fig. 31-38). The subcutaneous tissues are incised down to the fascia of the anterolateral tibial musculature. A fascial incision is made from the lateral aspect of the tibial tubercle sloping up proximally to the distal aspect of Gerdy’s tubercle and is extended posteriorly and laterally to the anterior bare area of the fibula. The anterior bare area of the fibula is an important and safe anatomic landmark. The FCL and peroneal nerve are safely avoided when one identifies this area, which is used to initiate the limited subperiosteal exposure of the fibular neck for the fibular osteotomy.

FIGURE 31-38 Closing wedge osteotomy technique. A, Skin incision. B, Exposure for the lateral tibial and fibular osteotomy. C, Landmarks for the skin incision. D, Subperiosteal dissection of the muscles to expose the lateral tibia and proximal fibula. E, Osteotomy of the fibula at the head-neck junction. F, Removal of the fibular bone. G, Placement of two guide pins at predetermined measured angles and depth for correction. H, Alternative use of a commercial guide system for guide pin placement. I, Removal of the bone wedge. J, Lateral gap is equal except for the anterior triangular portion where the gap narrows to prevent alteration of the tibial slope. K, Gentle closure of the osteotomy to protect the medial cortex. L, Determination of the WBL correction by fluoroscopy and computerized navigation, which is recommended.

Subperiosteal dissection on the tibia is initiated just distal to Gerdy’s tubercle, using a scalpel followed by a Cobb elevator. The dissection is continued just lateral to the patellar tendon and should be done cleanly, with a relatively bloodless field and without damage to muscle tissue. The retinaculum adjacent to the patellar tendon is incised and the retropatellar space entered. The patellar tendon is retracted anteriorly.

The dissection is continued posteriorly on the tibia. It is important to remain in a subperiosteal plane because of the proximity of neurovascular structures. The safe zone is just distal to Gerdy’s tubercle to avoid the peroneal nerve. Posteriorly, the dissection is completed across the width of the tibia in one location and is then carefully extended proximally and distally in this safe posterior tibial subperiosteal plane.

Step 3: Fibular Osteotomy

There are three options for the fibula when performing an HTO: proximal slide, proximal fibular osteotomy, and distal fibular osteotomy. A proximal slide (disruption of the tibiofibular joint) is strongly contraindicated because this shortens the FCL and posterolateral structures and may lead to a severe posterolateral instability in an already unstable knee.

The preferred procedure is a proximal fibular osteotomy through the fibular neck region (see Fig. 31-38). Meticulous surgical technique with protection and palpation of the peroneal nerve is essential. The peroneal nerve is always identified and partially dissected. In order to protect the fibers of the peroneal nerve, the lateral and posterior periosteal sleeve is carefully preserved and not retracted under tension. If there is any question as to the position of the nerve or chance of nerve damage, exposure of the entire nerve is indicated with direct visualization and protection.

The fibular bone section removed is 2 to 3 mm less than the computed tibial wedge to allow compaction at the fibular osteotomy site. Excellent bony apposition is achieved when the osteotomy is closed, and it is not necessary to add internal fixation. Careful inspection of the fibular osteotomy is done to remove any rough osteotomy edges that would be adjacent to the peroneal nerve.

An alternative choice for a fibular osteotomy is at the junction of the middle and distal thirds of the fibula through a 3-cm posterolateral incision. The peroneal muscles are retracted anteriorly and two bunion retractors can be used for exposure after subperiosteal exposure. A lateral section of the fibula is removed. The medial cortex of the proximal fibula is osteotomized at one site and allowed to slide to maintain bone contact and promote union. A bone graft from the tibial site is added. With this technique, it is not necessary to add internal fixation.

The surgeon should be well aware of the anatomic variability of the superficial peroneal nerve (SPN) in the middle third of the leg. Barrett and colleagues¹⁴ reported on this factor in 35 nonpaired and 40 paired cadaver lower extremities. The SPN was identified in the lateral compartment adjacent to the fascial septum in 72%, in the anterior compartment in 23%, or with a branch in both the anterior and the lateral compartments in 5% of the specimens. Ducic and coworkers,³⁴ in a study of 111 cadaver and clinical specimens, described a similar variability of the location of the SPN in the middle third of the leg. The SPN traveled to the lateral compartment in 70% of the specimens or split with branches in both the lateral and the anterior compartments in 16%. In 6% of the specimens, the SPN was found within the intermuscular septum, and in 8%, traveled only within the anterior compartment.

Step 4: Proximal Osteotomy: Removal of Tibial Wedge

The proximal tibial closing wedge osteotomy technique may be performed using commercially available calibrated osteotomy guide systems, or the bone cuts may be determined using a free-hand method. A smooth guide pin is placed transversely at the proximal tibia to the medial cortex, 25 mm distal to the joint line with the use of fluoroscopy to ensure proper placement. It is critical to leave at least 25 mm of proximal tibia to avoid a tibial plateau fracture. The transverse length of the guide pin determines proximal tibia width.

After the preoperative measurements and based on tibial width (see Table 31-6), the entry point of the second guide pin distally is marked with proper positioning of the guide pins confirmed with fluoroscopy. These guide pins determine the osteotomy triangular bone wedge that is removed to achieve the desired correction. It is important to determine whether the lateral cortex is entirely perpendicular at the osteotomy site. In some knees, there will be a slight triangular anterior slope where it is necessary to downsize the osteotomy gap anteriorly in order not to decrease the tibial slope. The width of the tibia anteriorly is measured and the anterior gap determined (see Table 31-6).

The initial osteotomy cuts are made using a micro-oscillating saw. Initially, only the outer cortex is cut and then the osteotomy is completed with thin osteotomies. An oscillating saw in the cancellous bone may wander and potentially change the correction angle.

A malleable retractor is placed in the subperiosteal plane posteriorly to protect the neurovascular structures at all times with the knee flexed 10°. The lateral half of the wedge is removed as a single piece. Portions of this bone wedge may rarely need to be replaced if an inadvertent overcorrection is obtained at surgery. The remaining triangular wedge of bone is removed under direct visualization.

The surgeon is seated, and a headlamp is always used to view the depth of the osteotomy. The osteotomy plane is maintained in a triangular plane, noting that at the midpoint of the tibia, the tibial width is one half that at the lateral cortex.

The 7 to 10 mm of the wedge adjacent to the posteromedial cortex is left intact to provide stability and prevent medial or lateral tibial translation or varus angulation postoperatively. The posterior tibial cortex of the wedge is removed under direct visualization. The patellar tendon is carefully protected.

Two to three perforations of the posteromedial cortex with a guidewire are often required before the osteotomy gap can be closed with a gentle valgus force that is applied over a few minutes to gradually deform the remaining medial cortex. An option is to use a commercially available compression device to close the osteotomy. Apposition of the bony surfaces of the tibia and fibula should be visualized and inspected.

It is important that the HTO does not increase or decrease the normal posterior tibial slope. The sagittal plane of the osteotomy should be perpendicular to the long axis of the tibia with the width of posterolateral cortex removed based on the coronal angular corrections required (see Table 31-6). In select cases, a biplanar osteotomy for correction of an abnormal tibial slope may be required, as already described. An opening or closing gap in the sagittal plane is performed to the necessary degrees of slope correction.

Step 5: Fluoroscopic Verification of the WBL for Corrected Alignment

Using fluoroscopy, an alignment guide rod (rigid 3–4 mm rod, 1 m in length) is positioned over the center of the femoral head and the center of the tibiotalar joint to determine the corrected WBL intersection at the tibial plateau. A large single staple may be placed across the lateral tibial osteotomy site for provisional fixation. During fluoroscopy, the lower limb is axially loaded at the foot to maintain closure of both the medial and the lateral tibiofemoral compartments at 5° to 10° flexion to avoid hyperextension. It is important to view by fluoroscopy that there is no abnormal opening of the medial or lateral compartment. The knee is taken through a gentle varus-valgus loading to palpate the respective compartments and confirm closure of both because significant errors in the final axial alignment occur if great care is not taken at this junction. A second source of error in the WBL tibial intersection occurs if the lower limb is positioned incorrectly with excessive hip internal or external rotation. The lower limb and foot are positioned with a normal 12° to 15° of external rotation, representing the normal gait foot progression alignment. The alignment guide rod represents a new WBL, which should agree with preoperative calculations. As discussed next, computerized navigation techniques have a distinct advantage in the authors’ opinion in improving the accuracy of the WBL determination and final lower limb alignment during the operative procedure. If necessary, further bone may be removed or added to the osteotomy to adjust the WBL.

Internal fixation of the osteotomy is achieved using an L-shaped plate. Two 6.5-mm cancellous screws are placed in the proximal tibia and three cortical screws are placed distal to the osteotomy (Fig. 31-39). Rarely, a 6.5-mm cancellous screw is placed in a lag fashion across the osteotomy site into the medial aspect of the proximal tibial bone for additional fixation. Newer locking plates and screws provide the advantage of more secure fixation. The final WBL is determined after fixation.

FIGURE 31-39 AP (A) and lateral radiographs (B) show the postoperative appearance after proximal tibial osteotomy, fibular osteotomy, and internal fixation.

(A and B, Reprinted with permission from Noyes, F. R.; Barber-Westin, S. D.; Hewett, T. E.: High tibial osteotomy and ligament reconstruction for varus angulated anterior cruciate ligament–deficient knees. Am J Sports Med 28:282–296, 2000.)

The tourniquet is released and hemostasis obtained. The fascia of the anterior compartment musculature is reattached to the anterolateral aspect of the tibial border with absorbable sutures. It is important to reattach the muscles with adequate suture fixation because muscle tension postoperatively may disrupt the muscle attachment site. A drain is not used.

The lower limb is wrapped with cotton and additional padding is placed posteriorly and over the peroneal nerve, followed by an Ace bandage, postoperative hinged brace, and bilateral ankle-foot compression boots. A commercial ice delivery system with the bladder incorporated over the initial cotton wrapping, a few layers from the wound, is always used. The neurovascular status is checked immediately in the operating room and carefully monitored in the initial postoperative period. A calf or foot compression system is used for the first 24 hours to promote venous blood flow. Aspirin is prescribed and, rarely in high-risk patients, low-molecular-weight heparin (LMWH) or warfarin sodium (Coumadin; Bristol-Myers Squibb Co., Plainsboro, NJ). Early rehabilitation emphasizes early quadriceps isometrics, range of knee motion, ankle pumping, and ambulation (see Chapter 33, Rehabilitation after Tibial and Femoral Osteotomy). The surgeon should have a high suspicion for venous thrombosis and a low threshold for ordering ultrasound evaluation in the postoperative period, which is obtained in the majority of patients in the first few days after surgery.

With the meticulous dissection technique described, a postoperative compartment syndrome should be an exceedingly rare occurrence, if at all. The operative limb is always elevated for the 1st postoperative week, except for periods of ambulation with crutches. The maximum swelling of limb tissues after HTO is usually present 48 to 96 hours postoperatively. The postoperative rehabilitation program is discussed in Chapter 33, Rehabilitation after Tibial and Femoral Osteotomy.