Tibial and Femoral Osteotomy for Varus and Valgus Knee Syndromes: Diagnosis, Osteotomy Techniques, and Clinical Outcomes

Subjective and Functional Outcome

Patients complete questionnaires and are interviewed for the assessment of symptoms, functional limitations, sports and occupational activity levels, and patient perception of the overall knee condition according to the Cincinnati Knee Rating System (CKRS; see Chapter 41 ).

Symptoms of pain, swelling, and giving way are well recognized consequences of ACL deficiency. However, in a 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. In the early stages, the patient usually complains of medial pain occurring with sports activities but not with daily activities. When pain occurs with daily activities, there is a high likelihood 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.

The physical examination of the knee joint to detect all of the abnormalities in a varus-angulated knee is comprehensive ( Table 26-2 ) and includes assessment of (1) the patellofemoral joint, especially possible extensor mechanism malalignment caused by 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 caused by tensile overloading; (4) gait abnormalities (excessive hyperextension or varus thrust) during walking and jogging ; and (5) abnormal knee motion limits and subluxations compared with the contralateral knee.

Diagnostic Clinical Tests

The medial posterior tibiofemoral step-off on the posterior drawer test is done at 90 degrees of flexion ( Fig. 26-10 ). This test is performed first to identify that the tibia is not posteriorly subluxated, indicating a partial or complete PCL tear. A KT-2000 (MEDmetric) arthrometer test may be done at 20 degrees of flexion (134-N force) to quantify total AP displacement. The Lachman test is performed at 20 degrees of knee flexion. The pivot shift test is done and the result recorded on a scale of 0 to III, with a grade of 0 indicating no pivot shift; grade I, a slip or glide; grade II, a jerk with gross subluxation or clunk; and grade III, gross subluxation with impingement of the posterior aspect of the lateral side of the tibial plateau against the femoral condyle.

FCL insufficiency is determined by the varus stress test at 0 and 30 degrees of knee flexion (see Fig. 26-10 ). The surgeon estimates the amount of joint opening (in millimeters) between the initial closed contact position of each tibiofemoral compartment, performed in a constrained manner avoiding internal or external tibial rotation, to the maximal opened position. The result is recorded according to the increase in the tibiofemoral compartment of the affected knee compared with that of the opposite normal knee. This comparison is crucial, and it is important to avoid measuring only the degrees of varus or valgus rotation in the involved knee.

An increase in medial joint opening may occur compared with the opposite knee that represents a pseudolaxity because the increase is actually caused by medial tibiofemoral joint narrowing. When the test is conducted under a varus stress, the medial joint opening returns the limb to a more normal alignment, and there is no true medial ligamentous damage. The true amount of medial and lateral tibiofemoral compartment opening is later confirmed during the arthroscopic examination with gap tests. The primary and secondary restraints that resist lateral joint opening have been described previously. The abnormal medial joint opening depends on the knee flexion angle at which the test is conducted and the integrity of the secondary restraints.

Tibiofemoral Rotation Test (Dial Test)

The tibiofemoral rotation test was first described by the senior author (F.R.N.) and is used to estimate the amount of posterior tibial subluxation (see Fig. 26-10 ). The test is conducted in the following manner: (1) the tibia is positioned at 30 degrees of knee flexion, in neutral rotation; (2) the position of the anterior aspect of the medial and lateral tibial plateaus are determined in reference to the femoral condyles by palpation; (3) the tibia is externally rotated to its maximum position; (4) the positions of the medial and lateral tibial plateaus are palpated to determine an abnormal posterior subluxation of the lateral compartment or anterior subluxation of the medial compartment; (5) the examiner observes the location of the tibial tubercle to determine any increase in external tibial rotation compared with the opposite normal knee; and (6) the test is repeated at 90 degrees of knee flexion and may also be conducted by starting at the neutral tibial rotation position, progressing to internal tibial rotation.

If an increase in external tibial rotation is present, it represents either a posterior subluxation of the lateral tibial plateau (indicating injury to the FCL and PMTL) or anterior subluxation of the medial tibial plateau (indicating injury to the superficial medial collateral ligament [SMCL] and posteromedial structures). In some knees, both anteromedial and posterolateral subluxations are present.

The tibiofemoral rotation test involves close observation of the location of the internal and external tibial rotation axis and comparison of the location of this axis with that in the normal knee. With posterior subluxation of the lateral tibial plateau during external tibial rotation, the examiner may detect a shift in the axis of tibial rotation to the medial tibiofemoral compartment. Alternatively, with an anterior subluxation of the medial tibial plateau, the center of tibial rotation shifts to the lateral tibiofemoral compartment as the maximal external tibial rotation position is reached.

The advantages of the tibiofemoral rotation test over the traditional posterolateral drawer test are (1) the knee may be positioned at varying flexion positions (30 and 90 degrees); (2) the tibia is less constrained because the foot is not held fixed to the examining table; and (3) the axis of tibial rotation can be observed as the tibia is rotated externally and internally. More information is gained when the tibiofemoral rotation tests are performed in a supine position. In the prone position, it is difficult to palpate the medial and lateral tibiofemoral position required to diagnose the abnormal compartment subluxations. The only indication for the prone dial test is a PCL-deficient knee in which the tibia can be gently displaced to a reduced anterior position during the rotation tests. In the supine position, the tibia can also be displaced anteriorly to prevent posterior subluxation, which makes the interpretation of the dial test more difficult.

A varus recurvatum test in both the supine and standing positions and the reversed pivot shift test are included in the assessment of posterolateral tibial subluxation. However, these represent qualitative tests that are difficult to measure in objective terms. Still, they provide useful information regarding the magnitude of the overall subluxation of the knee joint when two or more abnormal motion limits are present.

Radiographic Assessment

Radiographic assessment of lower limb alignment is based on full-length radiographs of the extremity with the patient in the standing position. Separation of the lateral tibiofemoral compartment may occur, preventing a correct assessment of true tibiofemoral osseous alignment. Double-stance, full-length AP radiographs showing both lower extremities from the femoral heads to the ankle joints are obtained. The knee is flexed 3 to 5 degrees to avoid a hyperextension position, and the foot angle is set to approximately 10 to 12 degrees. If separation of the lateral tibiofemoral joint is observed on radiographs, it is necessary to subtract the lateral compartment opening so that the true tibiofemoral osseous alignment is determined and a valgus overcorrection at surgery is avoided as is discussed under Preoperative Planning.

During varus-valgus testing at 30 degrees of flexion, the clinician should assess for a possible teeter-totter effect, in which simultaneous contact of the medial and lateral tibiofemoral compartments is not possible owing to advanced tibial obliquity and bone loss of the medial tibiofemoral joint.

Additional radiographs taken during the initial examination include a lateral at 30 degrees of knee flexion, weight-bearing PA at 45 degrees of knee flexion, and patellofemoral axial views. Telos medial or lateral stress radiographs may be required in select knees ( Fig. 26-11 ).

The height of both patellas is measured on lateral radiographs ( Fig. 26-12 ) to determine whether or not an abnormal patella infera or alta position exists that may be a factor in selecting an opening or closing wedge osteotomy, which would further decrease or elevate the patella position.

The clinical algorithm for the preoperative clinical and radiographic assessment to determine candidates for either a medial opening wedge or lateral closing wedge osteotomy is shown in Figure 26-13 .

Calculations to Determine Angular Correction

The preoperative calculations for HTO involve 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. The radiographic measurement and correction may require alteration at surgery with fluoroscopic analysis, as described. The normal tibiofemoral coronal alignment is shown in Figure 26-14 . In varus angulated knees, there is a slight increase in obliquity caused by medial tibiofemoral joint arthrosis principally involving the medial condyle.

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 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. A single-stance radiograph of the affected limb will show the maximum varus angulation caused by lateral condylar lift off; however, this should not be used for osteotomy calculations. A double-stance radiograph helps close the lateral tibiofemoral compartment so the osseous alignment is calculated, which is required for surgical correction.

Sabharwal and Zhao compared lower limb coronal alignment on full-length, standing radiographs to 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. There was no description of the effect of abnormal lateral joint opening on the standing radiographs that may account for errors in preoperative measurements. Furthermore, during 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 during HTO 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 degrees of knee flexion and approximately 10 to 12 degrees of external rotation (hip to ankle axial alignment simulating 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, and 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 26-15 . The case represents a 38-year-old man whose full-length, standing radiograph shows a varus angular deformity (mechanical axis) of 7 degrees 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:

Therefore, in this patient, the calculated amount of varus angular deformity caused by the lateral joint opening increase of 4 mm is 76.4 (4 mm)/81 mm = 3.7 degrees, or approximately 1 degree/mm increased lateral joint separation. Failure to account for the lateral joint opening would result in approximately 4 degrees of valgus overcorrection after HTO, assuming closure of the lateral tibiofemoral joint ( Fig. 26-16 ). A WBL crossing the knee lateral to the 75% coordinate has the potential for a lift off of the medial femoral condyle and a cosmetic abnormal valgus alignment. Unicondylar weight bearing resulting from distraction of the medial compartment is undesirable and could result in subsequent arthritis of the lateral compartment, MCL laxity, and a progressive valgus deformity ( Fig. 26-17 ). 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 study showed the WBL axis to be more accurate than the anatomic axis for osteotomy correction.

Two methods are used to determine the correction wedge on preoperative radiographs. First, the centers of the femoral head and tibiotalar joint (center of the talus) are marked on the full-length radiograph ( Fig. 26-18 ). 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 degrees of 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% to 54% 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., before 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 published 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.

The second method of determining the correction wedge involves cutting the full-standing radiograph horizontally through the line of the superior osteotomy cut ( Fig. 26-19 ). 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 collinear. 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.

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 abnormality.

Several methods have been reported to measure the medial and lateral tibial slope based on lateral tibial radiographs ( Table 26-3 ). Each method results in different slope values for the same tibia ( Fig. 26-20 ), and all studies show high standard deviations and ranges, indicating that tibial slope may show variation among individual patients. Brazier and colleagues 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 coworkers and Julliard and associates recommended using the tibial mechanical axis to represent the true tibial slope. The PTAA is our preferred method for HTO, and the anterior tibial cortex measurement is used when cutting the proximal tibia during total knee arthroplasty (TKA).

Most authors have measured the medial tibial slope; only a few have measured and provided data on the lateral tibial slope. 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 degrees less than the osseous tibial slope according to Jenny and colleagues.

Increasing the tibial slope increases anterior tibial translation and, potentially, tensile loads on the ACL or an ACL reconstruction ( Fig. 26-21 ). Conversely, decreasing the tibial slope theoretically would increase tensile loads on the PCL and shift the tibia to a more anterior position. Shelburne and colleagues studied how changes in posterior tibial slope affected tibial shear force, anterior tibial translation, and knee ligament loading during standing, squatting, and stance-phase walking activities. These authors used a validated computer modeling of the lower extremity and altered the posterior tibial slope in 1-degree increments up to a maximum of 10 degrees of change in slope. The results showed that anterior tibial translation increased as posterior tibial slope increased, and ACL force increased (for standing and walking) as tibial slope increased. It is important to note that the increased ACL force values were in the modest range because ACL force increased by 16 N for each degree of increase in posterior tibial slope. The model predicted a 6-N decrease in PCL force and a 15-N decrease in posterolateral ligament force for each degree increase in posterior tibial slope. Similar results were reported by Marouane and associates who used two finite element models of the knee joint to model the effect of changes in posterior tibial slope on ligament loads and tibial translation and to predict contact pressures of the lateral and medial plateau (under 100-N axial load). The data showed that, at mid stance in the gait model, a change in posterior tibial slope from –5 to +5 degrees resulted in a change in ACL force from –79 to +136 N from the 0 neutral reference point. This corresponded to a change in AP position from –1.2 to +1.2 mm from the 0 neutral position. In comparison, the study by Shelburne and colleagues showed an alteration in posterior tibial slope of –5 to +5 degrees in walking resulted in a change from –75 to +80 N in ACL force, as well as a change from –2.3 to +2.4 mm in anterior tibial translation relative to reference values. Accordingly, these studies show that there is the potential for higher ACL forces on a healing ACL graft substitute with an abnormal tibial slope; however, the increase in forces is in the modest range and well below predicted ACL graft rupture. It would thus be prudent to measure the tibial slope in patients undergoing ACL surgery and determine those outliers (±2 standard deviations) in whom a more conservative rehabilitation program should be used to protect the healing graft in the early to mid postoperative period. This suggestion may even have increased relevance with low-strength ACL grafts that have decreased healing potential, as shown with allografts. Marouane and associates reported in their second finite element model that a 1400-N axial load at 45 degrees of knee flexion at posterior tibial slopes of –5 degrees, neutral 0 degree, and 5 degrees produced calculated ACL forces of 102 N, 181 N, and 317 N, respectively.

Giffin and coworkers reported in cadaveric knees that an increase of 5 degrees in the tibial slope produced an anterior shift in the resting position of the tibia (maximum, 3.6 mm ± 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 degrees) 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, the 200-N axial load does not simulate larger weight-bearing loads with activity.

In a second study conducted by Giffin and associates, 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 PCL-deficient osteotomy knees. The data show that the tibia reached a similar abnormal posterior tibial position (mean, 90 degrees 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 colleagues 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 degrees of flexion osteotomy, ~5 mm, 30 degrees of knee flexion) that 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 that are required 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 degrees of flexion; with osteotomy, ~1100 N quadriceps applied load). In fact, the increased quadriceps loading increased joint contact pressures.

In contrast to the study just discussed, Rodner and coworkers reported in cadaveric knees that an increase in tibial slope in the ACL-deficient knee at the time of an 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, thereby demonstrating the marked effect that in vitro experimental loading conditions have on joint contact pressures and study conclusions.

Brandon and associates 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 degrees and 2.4 degrees, respectively), and the high-grade pivot shift patient group had an increase in tibial slope (mean value increased ~2 degrees). The measurements show high standard deviations (~35% of the mean values), and it is probable that the few degrees difference among patient groups are not clinically significant or would result in increased ACL load and anterior tibial displacement.

Dejour and colleagues evaluated chronic ACL-deficient knees with monopodal lateral weight-bearing films (knee flexed 20 to 30 degrees 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 degrees. 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-degree 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 degrees, anterior tibial translation varied from approximately –2 to 12 degrees.

Griffin and Shannon 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 coworkers recommended that knees with ACL insufficiency and associated medial arthritis with a tibial slope of 10 degrees 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 authors have discussed increases in ACL tensile loads when tibial slope exceeded 10 degrees and postulated the need for correction, again without clinical data.

Griffin and Shannon 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.

We agree with recommendations to correct tibial slope when a distinct abnormality is present ( Figs. 26-22 and 26-23 ). The published literature does not provide objective data regarding the degrees of abnormal increase or decrease in tibial slope when corrective osteotomy is indicated where there is an associated ACL or PCL insufficiency.

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-degree 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 theoretical benefits but has not been proven in clinical studies to be adopted as a treatment recommendation.

There are patients who have a distinctly abnormal tibial slope from a prior osteotomy, tibial fracture, or growth abnormality or an underlying genetic variability in which correction of the tibial slope is required before cruciate ligament surgery or other conditions discussed. Occasionally, ACL revision patients have an abnormally increased slope that should be corrected before ACL revision surgery. Empirically, a tibial slope 2 standard deviations above normal or more (based on the method) 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 altered in ACL-deficient knees or 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. For every 1 mm of anterior gap change, an approximate 2-degree change in tibial slope would be produced. This is based on the angle of the anteromedial tibial cortex, the tibial width, and the AP distance where the gap measurement is made (see Table 26-5 ). 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 increase in ACL tensile loads. For example, a change in the tibial slope by 10 degrees 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 after the osteotomy is carefully closed anteriorly to the desired amount. In the senior author's experience, biplanar corrections require the use of a secure locking plate design to maintain the correction because it is necessary to extend the osteotomy through the lateral tibial cortex to close the anterior osteotomy gap ( Fig. 26-24 ). 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 be sure the posterolateral tibial cortex has been osteotomized to prevent a lateral tibial plateau fracture from occurring just anterior to the remaining posterolateral cortex.

Song and associates 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 a Noyes and colleagues study (anterior gap 50% of posterior gap). The data of Noyes and colleagues' study allow the gap to be computed along the entire anteromedial cortex. The Song et al study does not specify where the two plates are placed, whereas data of the Noyes and colleagues' study show the actual gap distance where one or two plates would be placed.

Hohmann and coworkers retrospectively reviewed the radiographs of 67 patients who had a closing wedge HTO and reported a mean decrease of 4.9 degrees in the tibial slope. They suggested that this occurred because of the triangular geometry of the tibia, with a larger width of bone removed 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 26-4 and Fig. 26-25 ). 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. In double and triple varus knees, the ligament reconstructive procedures are performed after the HTO to reduce the risk of complications. Prolonged rehabilitation and an increased risk of knee arthrofibrosis and motion problems have been described after HTO and ligament reconstructive procedures are performed simultaneously.

We prefer to perform the HTO first and, after adequate healing of the osteotomy, the required ligament reconstructive procedures are performed. 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 to 8 mm of increased lateral joint opening, 10 degrees of increased external tibial rotation). In a study conducted by us, described later in this chapter, 22 of 41 double varus knees (54%) had abnormally increased lateral joint opening on varus stress testing before osteotomy. Of these, only five (12%) had this abnormal joint opening at follow up. An FCL and posterolateral reconstruction was avoided in many patients. A subgroup of 11 patients (27%) did not require ACL reconstruction because instability symptoms did not exist after the HTO.

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, a 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 are preferred substitutes. 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 bone-patellar tendon-bone autografts as discussed in detail in Chapters 7 and 8 . 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 16 . The options for surgical restoration of deficient posterolateral structures are described in Chapter 17 .

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 degrees 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 to avoid a proximal fibular osteotomy because an FCL graft will be anchored to the proximal fibula. Opening wedge osteotomy is advantageous in cases of patella alta or decreased lower limb length which would be made worse by a closing wedge osteotomy. A significant patella infera is a relative 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 (with major corrections). Autogenous bone grafting of the open defect aids in promoting prompt union with reduced risk of varus collapse caused by a delayed union.

Several opening wedge plate designs are available. We prefer a tibial plate with locking screws to achieve secure osseous fixation. 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. With attention to this problem during surgery, the normal tibial slope in the sagittal plane can be preserved with any of the available plate designs.

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 if it is necessary to achieve additional angular correction. The triangular bone wedge is removed and saved in case it is necessary to reinsert bone during the procedure if an overcorrection occurs.

Brouwer and associates 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 to 6 degrees valgus) was noted in 79% of the closing wedge osteotomies compared with 56% of the opening 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 during 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. Disadvantages of an external fixator are the risk of pin tract infection and the 12-week period 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 3-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.

The data in this study on the obliquity of the anteromedial cortex of the proximal tibia relative to the posterior tibial cortex ( Fig. 26-26 ) are presented from 35 magnetic resonance imaging (MRI) films in healthy young individuals (mean age, 32.7 years). 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.

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. 26-27 ) 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.

The MRI measurement of the anteromedial tibial cortex oblique angle at the site of the opening wedge osteotomy was 45 ± 6 degrees (range, 34-56 degrees). 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 26-28 , 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 degrees).

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 26-29 , 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.

As an example, a 10-degree coronal valgus correction (assuming a normal 45-degree obliquity of the anteromedial tibial cortex) would result in a 7-degree 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 26-30 , which represents the desired wedge angle for a 10-degree 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.

These variables are shown in Table 26-5 . For example, an error of 5 mm in the Y ₂ gap ( Fig. 26-31 ) 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 degrees. As a general rule in this example, every millimeter of alteration in the gap height induces a change of 2 degrees in the tibial slope.

The opening wedge angle can be set at surgery by measuring and altering the vertical gap (width) at two points along the osteotomy site, Y ₁ and Y ₂ ( Fig. 26-32 ). This has importance in determining that the correct wedge angle is obtained before 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, the obliquity of the anteromedial tibial cortex, and the distance along the osteotomy site on the anteromedial surface ( Tables 26-6 and 26-7 ).

In Table 26-6 , the millimeters of opening at the osteotomy site are based on the width of the tibia and the angle of correction. In Table 26-7, an average 45-degree 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 (X ₁ ). The opening height at the most posteromedial point (Y ₁ ) and the distance between the two measurement points (Y ₁ -Y ₂ ) are used in Table 26-7 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 26-7 , with a 10-mm posteromedial opening (Y ₁ ), 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 26-7 ). 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

• 1.

  Determine the coronal valgus angular correction in degrees based on preoperative full-standing radiographs for the desired placement of the WBL at the tibial plateau and measure the tibial slope based on a lateral radiograph.

• 2.

  Determine the millimeters of opening at the posteromedial osteotomy site at surgery (Y ₁ gap) using the width of the tibia (X ₁ distance) for the coronal valgus correction based on the law of triangles (first triangle; see Table 26-6 ).

• 3.

  Determine the proper gap width of the osteotomy opening wedge along the anteromedial cortex to maintain tibial slope and the proper width beneath the tibial plate based on its location along the anteromedial cortex (see Table 26-7 ). The opening wedge gap will always be 3 to 4 mm less where the plate is located. If the tibial slope is to be increased or decreased, the effect on the degrees of tibial slope is shown in Table 26-5 .

• 4.

  Confirm final coronal and sagittal angular correction based on intraoperative fluoroscopy and early postoperative full standing and lateral radiographs.