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Management of Fixed Deformity
at Total Knee Arthroplasty


In: Total Knee Arthroplasty
A Comprehensive Approach
Editors: Hungerford, D.S., Krackow, K.A., Kenna, R.V.

Copyright © 1984 Williams & Wilkens, Baltimore, Maryland


1. General Principles

Kenneth A. Krackow, M.D.

The surgical treatment of severe preoperative fixed deformity at total knee arthroplasty involves the appreciation of several basic principles. First, and most obvious, is the fact that fixed deformity means that the soft tissues about the knee are unbalanced. A relative contracture exists at the inner or concave side of the deformity, while a comparative "excess" in the soft tissue envelope exists on the opposite, convex side. If soft tissue balance is to result where major deformity existed, it will have to be achieved by surgical adjustment of the soft tissues themselves. Since the balance was not present preoperatively, if it is to exist postoperatively, it must be created intraoperatively. Soft tissue balancing per se will not be achieved by bone resection, and the surgeon must remember that the ultimate goal at surgery is to establish correct alignment of the tibia with respect to the femur and to create concurrently a balance of the tension in the surrounding capsular ligamentous sleeve.

BONE CUTS

Although correct bone resection recreates the proper alignment of the femur to the tibia, when performed alone, it will not have addressed the soft tissue imbalance. Bone resection does, however, establish the orientation of the prosthetic components with respect to the axes of the femur and tibia. Because of this, the surgeon is limited to orienting his distal femoral and proximal tibial cuts so that the resulting prosthetic joint will be appropriately aligned. Such proper alignment is independent of soft tissue balancing considerations and, rather, is dependent upon parameters of individual body build.

The authors have accepted the following as constituting proper alignment at total knee arthroplasty:

The prosthetic joint shall be centered on the mechanical axis of the lower extremity and shall be horizontal to the ground in anatomic two-legged stance (Fig. 11.1.1).

Figure 11.1.1. Proper knee and lower extremity alignment are symbolized here. A horizontal joint line exists with the knee joint being centered on the mechanical axis. Both lower extremities are adducted so that the feet are adjacent to the midline. A line from the center of the femoral head to the center of the knee passes through to the center of the ankle. A fixed trapezoid is formed by connecting the centers of the femoral heads, drawing the mechanical axes and connecting the centers of the ankles.

The definition of mechanical axis is standard, i.e., a line connecting the center of the femoral head with the center of the ankle.

Anatomic two-legged stance is that position assumed by a subject standing with knees extended and both lower extremities adducted so that the feet approach the midline. This orientation of an individual lower extremity is also very close to the position assumed during mid stance phase of normal gait.

If a prosthetic joint is to be well aligned, then the orientation of the distal femoral cut to the shaft of the femur and the orientation of the proximal tibial cut to the shaft of the tibia are predetermined for a given patient. This fact can be appreciated by first considering a situation wherein the distal femoral and proximal tibial cuts are properly oriented and the knee prosthesis is properly aligned in anatomic two legged stance. If, instead, a slightly different distal femoral cut had been made, one which has a greater valgus angulation with respect to the shaft of the femur, then the center of the femoral head would come to lie lateral to a line coming up from the center of the ankle through the center of the knee (Fig. 11.1.2). In this instance, if a mechanical axis line were constructed from the center of the femoral head to the center of the ankle, the mid point of the knee would lie medial to that line.

Figure 11.1.2. The result of an improper excessive valgus cut is symbolized. A distal femoral cut made in excessive valgus results in lateral positioning of the femoral head when the cut femur and tibia are brought together. Here a line drawn from the center of the femoral head to the center of the ankle passes lateral to the center of the knee.

Similarly, if in a second situation the distal femoral cut were made in relative varus, the femoral head would wind up medial to the knee, or alternately, the knee would lie outside the mechanical axis (Fig. 11.1.3).

Given a proper femoral cut, an improper proximal tibial cut would similarly displace the knee from the desired position on the mechanical axis (Fig. 11.1.4).

Figure 11.1.3. With an inappropriate varus distal femoral cut, the femoral head lies medial, and a line from the center of the femoral head to the ankle passes medial to the knee.
Figure 11.1.4. Improper orientation of the proximal transverse tibial cut similarly creates malalignment by displacing the center of the knee from the mechanical axis when the cut surfaces of the femur and tibia are opposed.

While it is true that an incorrect femoral cut could be balanced by an equally incorrect tibial cut made in the opposite sense, and that a joint centered on the mechanical axis would result, the prosthetic joint line would, however, no longer be horizontal. If anatomic two-legged stance were maintained, the joint line would assume an undesirable obliquity (Fig.1 1.1.5).

The fact that the inclinations of the distal femoral and proximal tibial cuts are fixed and determined individually according to body build may be appreciated from an additional viewpoint. Assuming that deformity has been corrected and that the extremities have been properly "straightened," the lines connecting the centers of the femoral heads, each femoral head to each respective ankle, and last, the centers of the ankles, form a trapezoid whose size and shape is unique for the patient (Fig. 11.1.6). The construction of such a trapezoid with the subject positioned in anatomic stance determines the inclination of that patient’s mechanical axes with the vertical, usually 2.5—3. Since the tibial shaft axis is coincident with the tibial segment of the mechanical axis, the orientation of the tibial cut with respect to the tibia itself must be the same as the orientation of the mechanical axis with a horizontal line.

Figure 11.1.5. An improper femoral cut has been balanced by an equally improper and complementary tibial cut. The prosthetic joint line remains centered on the mechanical axis, but it becomes tilted with respect to the horizontal.
Figure 11.1.6. A four-sided figure is formed by connecting the centers of the patient's femoral heads and the centers of his ankles, FF'A'A. Assuming that a patient has essentially equal extremity lengths and assuming that his preexisting valgus or varus deformities have been corrected bilaterally, this four-sided figure becomes an isosceles trapezoid. The angular orientation of the mechanical axes FA and F'A', therefore, depends upon the distance between the patient's femoral heads, his ankles, and the respective lengths of his femur and tibia. ø denotes the angulation measured between the mechanical axis and the veritical. ß denotes the angle formed between the mechanical axis and the shaft of the femur. ø is generally noted to be between 2.5 and 3°. ß ranges between 4° and 8°. ø depends upon the overall form of the trapezoid. ß depends upon the patient's femur. To achieve a horizontal joint line with the patient standing in anatomic position, the tibial cut must be made at an angle of ø plus ß. As the form of this trapezoid is dependent upon body build, and the angles ø and ß are depenndent upon the trapezoid and the structure of the femur, it follows that the proper angles for resection of the distal femur and proximal tibia are solely a function of body build.

As discussed in Chapter 4, regarding instrumentation, the inclination of the femoral cut relative to the vertical and the shaft of the femur is a combination of two angles; first the mechanical axis, and second the angle between this mechanical axis and the femoral shaft itself. This second angle depends solely upon the lengths of the femur and femoral neck, and the amount of femoral anteversion. It is also, therefore fixed for a given patient (Fig. 11.1.6). Thus, the relative inclination of the distal femoral cut to the vertical, and the orientation of the proximal tibial cut, also to the vertical, once realignment has been established, will be depended upon: the distance between the patient’s femoral heads, the distance between the centers of his ankles, the lengths of his femur and tibia, and the size of the angle between his femoral shaft and the femoral portion of his mechanical axis.

All of these are factors of bone structure and body build, quite independent of the degree or nature of any preexisting deformity.

SOFT TISSUE BALANCING

Although the orientation of distal femoral and proximal tibial cuts is fixed, the surgeon has some choice as to how much distal femur and proximal tibia may be removed, that is the depth of these cuts. Having determined the proper orientation of these cuts by preoperative planning, the surgeon must address the contracture or laxity in the surrounding soft tissue sleeve by either surgical release, soft tissue advancement, some combination of these two, or by performing deeper bone cuts and accepting some residual instability, generally from the convex side of the deformity.

Which of these four approaches the surgeon chooses to use, singly or in combination, will depend upon many individual considerations for each specific case. It must be remembered that this chapter addresses severe, fixed preoperative deformity wherein some specific action will be necessary if correct alignment and adequate stability are to be established. Furthermore, it must be understood that the authors have striven to address these problems and to use prostheses without rigid constraint in most severe cases because of the predictable, unsatisfactory results with more constrained units. Certainly, the use of hinges and other constrained devices would simplify such cases. However, for these patients, such simplification comes at too high a price in terms of component loosening, if they are to resume any reasonable activity level.

The authors of the subsections for this chapter accept the proposition that for most patients with severe deformity. TOTAL RECONSTRUCTION of the knee joint rather than simple replacement of surfaces is both desirable and achievable. When long-term prosthesis survival and the prospects for further revision and surgery are considered, the additional operative planning and surgical effort required by the relatively unconstrained prosthesis are deemed worthwhile for the vast majority of these patients.

2. Fixed Valgus Deformity

David S. Hungerford, M.D., and Dennis W. Lennox, M.D.

Fixed valgus deformity is more likely to require special surgical techniques than are other deformities. There are several reasons for this. First, the principal lateral stabilizers of the knee are muscles: the popliteus, the tensor fascia lata and the biceps femoris. This means that deformity is more likely to become fixed at an early stage. Second, more severe valgus deformity or deformity of long standing is likely to be associated with attenuation of medial capsular stabilizers. Because the principal medial stabilizers are not attached to muscles, residual static medial instability is likely to create functional instability. For these reasons, fixed valgus deformity is one of the more difficult problems to be addressed at total knee arthroplasty.

As with other fixed deformities, the goal is to appropriately align the lower extremity and properly position the individual prosthetic components. The order of cuts does not differ from the standard sequence detailed in Chapter 4. However, since there is a basic ligamentous imbalance, this will usually have to be addressed as an independent problem. In varus deformity, ligamentous imbalance may be only a function of lost bone stock. If that is the case, restoring alignment through replacement of lost bone with the prosthesis will automatically restore stability even with severe varus deformity. This may not always be the case, but most varus deformities fit within this concept. Valgus deformities become a problem at a much earlier stage, or lesser degree of deformity.

SOFT TISSUE STABILIZERS OF THE LATERAL ASPECT OF THE KNEE

Dynamic soft tissue stability of the lateral knee arises from four musculotendinous units: the iliotibial tract, the biceps femoris, the popliteus and the lateral head of the gastrocnemius. Additional stability is afforded by the posterolateral capsule-arcuate complex and the lateral collateral ligament. The anatomy of this area is comprehensively reviewed in Chapter 1. The predilection for valgus deformity to become fixed may reflect the observation that, of the six lateral stabilizers of the knee, four are musculotendinous units.

TYPES OF FIXED VALGUS DEFORMITY

Valgus deformities can best be understood by dividing them into two types, depending on medial stability. In Type I valgus deformity the elements include loss of lateral bone stock, shortened, tight lateral soft tissue components, and stable anatomically intact medial stabilizers (Fig. 11.2.1). In Type II valgus deformity, the medial stabilizing structures have been stretched out, allowing widening of the medial joint space (Fig. 11.2.2). Although most Type II deformities will be identified on weight-bearing films, not all will be so shown. Often the patient will not be putting significant weight on the affected leg or will be bracing one knee against the other when standing on both feet. If one suspects medial instability on the basis of clinical findings, and it is not shown radiologically, a stress film should be obtained.

Figure 11.2.1. Type I valgus deformity with lateral compartment bone loss, tight lateral soft tissue elements, but anatomically intact medial stabilizers.
Figure 11.2.2. Type II valgus deformity with all of the features of Type I plus medial soft tissue incompetence.

SURGICAL MANAGEMENT OF TYPE I FIXED VALGUS DEFORMITY

The correction of Type I valgus deformity is accomplished by lateral soft tissue release. This release alone is sufficient to allow appropriate alignment and stability of the limb since the medial stabilizers are competent. The surgical sequence for Type I deformity follows the standard technique through the exposure and the distal, anterior and posterior femoral cuts.

Prior to inserting jig IV and extending the knee, the lateral border of the tibia should be thoroughly inspected for the presence of marginal osteophytes. Occasionally, removal of a large lateral tibial osteophyte may obviate the need for lateral release. Loose bodies in the posterior recess must be removed as well as posterior and lateral osteophytes on the femur. These may tent capsular structures preventing correction of deformity.

With the spacer-tensor jig in place, the leg is extended. If the center of the ankle joint can be brought under the tip of the tibial alignment pin, the fixed deformity has already been corrected, and one can proceed utilizing standard technique. However, it is at this point that fixed deformity is demonstrated by the fact that the ankle cannot be brought underneath the tip of the alignment pin (Fig. 11.2.3). It is also at this point that Type I and Type IV deformities are differentiated. With the No. II jig in place and the lateral soft tissue sleeve distracted by expansion of the expandable arm, the medial side will be stable in Type I deformity and unstable in Type II deformity.

The lateral structures which may require release are depicted in Figure 11.2.4. In general the sequence of release would be: 1) iliotibial tract, 2) posterolateral capsule, 3) lateral collateral ligament, 4) popliteus tendon, 5) biceps femoris tendon, and 6) lateral head of gastrocnemius. This sequence is proposed only as a basic plan to guide soft tissue release. The structures released early in the sequence are those which are most commonly responsible for deformity and which, on release or lengthening, are most likely to allow correction. The minimum amount is released which will allow correction of the deformity.

Figure 11.2.3. With the spacer-tensor jig in place after the femoral bone cuts have been made, the center of the ankle cannot be brought underneath the tip of the tibial alignment pin.
Figure 11.2.4. Anatomy and levels of release and/or Z-plasty of structures involved in fixation of lateral deformity.


Just as each total knee arthroplasty is somewhat different, so too may the elements contributing to valgus deformity vary from individual to individual. Thus, preoperative and intraoperative palpation to determine which structures are responsible for lateral tightness should be utilized to guide soft tissue release rather than to adhere rigidly to a sequence of releases predetermined without regard to the particular knee under consideration. There is no substitute for intelligent intraoperative decision making.

A Z-plasty lengthening of lateral stabilizers is recommended over simple transection since some stability is afforded by repair. In the case of the musculotendinous units which afford dynamic stability, a lengthening procedure with repair seems preferable to tenotomy, particularly in the case of the strong iliotibial band which is a primary dynamic stabilizer of the lateral side of the joint.

TECHNIQUE OF LATERAL SOFT TISSUE RELEASE

Minimal soft tissue release laterally includes elevation of soft tissue from the lateral tibial plateau. If required, a next step will almost always include a Z-plasty with lengthening and subsequent repair of the iliotibial tract. This is performed near the insertion of the iliotibial tract without an additional incision. The iliotibial tract is palpated with the leg in full extension and the extensor mechanism everted to the lateral side. The anterior border of the tract is separated from the lateral retinaculum with which it blends. This accomplishes a lateral patellar release at the same time. Both the medial and lateral aspects of the iliotibial tract are then carefully isolated, and under direct vision the Z-plasty lengthening is performed. Correction should be tested by reinserting the spacertensor jig IV and extending the leg before proceeding to additional releases.

If release of the iliotibial tract is insufficient to allow correct limb alignment, then other structures to be released or lengthened in sequence include the posterolateral capsule, popliteus tendon, lateral collateral ligament, biceps femoris tendon and lateral head of the gastrocnemius muscle. To diminish the risk of damage to the peroneal nerve by excessive tension, a supplementary posterolateral incision is recommended when the lateral head of the gastrocnemius muscle and the biceps femoris tendon require release and Z-plasty. Decompression of the peroneal nerve should be performed as needed to avoid excessive tension. Proximal fibulectomy is one method to provide decompression of the peroneal nerve in severe valgus deformity correction but this is only rarely indicated.

SURGICAL MANAGEMENT OF TYPE II VALGUS DEFORMITY

There are two possible ways to deal with this severe form of valgus deformity to achieve both correction of deformity and stability. In the first case lateral release, sufficient to correct the deformity, is performed prior to making the proximal tibial cut. Although this will align the limb, the knee will not be stable medially. To produce stability, a thick tibial plateau will have to be inserted to compensate for medial laxity. This, however, requires additional lateral release and results in lengthening the leg through the knee. Simply correcting the deformity puts the peroneal nerve at risk. Lengthening the leg through the knee potentiates that risk. For extreme cases of medial instability, such an approach is virtually impossible. The case depicted in Figure 11.2.5 would require 15 mm of prosthesis just to take up medial soft tissue slack, in addition to any bone resected to obtain a flat proximal tibial cut. Even for less severe cases of Type II deformity, the insertion of an excessively thick tibial component separates the femoral and tibial attachments of the posterior cruciate ligament, causing it to be prematurely and excessively tight in flexion.

Figure 11.2.5. Severe valgus deformity with traumatic medial soft tissue instability. It is impractical to provide medial soft tissue stability through insertion of a thick tibial component.


For these reasons, we prefer to produce stability in Type II deformity by medial soft tissue advancement. For moderate Type II deformity a limited lateral release, usually restricted to a Z-plasty lengthening of the iliotibial tract, is performed to allow alignment of the lower extremity prior to cutting the proximal tibia. The medial structures are advanced to produce stability after the prosthesis is implanted (see technique below).

For more severe forms of Type II deformity with extensive lateral contracture, the magnitude of the lateral release required can be diminished by proceeding first with a modest femoral shortening. Four millimeters of additional femoral shortening can be easily and quickly carried out and produces a significant decompressive effect on the lateral side. If one is already committed to a medial advancement, the additional medial instability which this additional femoral resection will produce is of no consequence. If it would not otherwise be necessary to effect a medial advancement, femoral shortening should not be employed. Thus, femoral shortening is contraindicated in Type I valgus deformity. If when the IA and IB jigs are in place in proper alignment, it can be seen that no bone will be removed from the lateral side, a few millimeters of the distal surface of the medial condyle can be removed with an oscillating saw. The IA and IB jigs are then repositioned and a femoral shortening will be automatically effected. If the need for femoral shortening is seen only after the spacer-tensor jig shows the magnitude and type of deformity, the following special technique is carried out.

TECHNIQUE OF FEMORAL SHORTENING

If needed, the distal femur can safely be removed to the level of the collateral ligaments. The distal femoral cutting jig, IA, is reinserted into the central anchoring hole, and a 3/16" drill pin is positioned laterally across the distal femur and acts as a spacer between the bone and jig (Fig. 11.2.6). Next, the distal femoral cutting jig, IB, is inserted into the IA jig and fixed with two 1/8" drill pins. Varus-valgus and flexion-extension alignment are then rechecked with the alignment guide. The assembled jigs IA and IB leads to the removal of 9 mm of distal femur when jig IA is flush against the distal femur. Therefore, by using the 3/16" drill pin (5 mm) to hold jig IA away from the initial cut surface, only an additional 4 mm of distal femur will be removed. A thicker interposing spacer will lead to a correspondingly thinner additional resection and vice versa. Assuming that, after this additional resection, full extension and proper tibial axial alignment are possible, the standard procedure for fixing in place the transverse tibial cutting jig V is followed. After additional femoral resection, it will be necessary to reposition jig III and recut the anterior femur to accommodate the femoral trial prosthesis.

Figure 11.2.6. Positioning the 3/16" drill as a spacer between the face of jig IA and the initial distal femoral cut prior to relocking jib IB in place to affect femoral shortening.

ALTERNATIVE TECHNIQUE FOR FEMORAL SHORTENING

For those who have the revision cutting block accessory to the Universal total knee instruments, this can also be used for recutting the distal femur. The details of the revision cutting block and its use are extensively presented in Chapter 19. Since this block can be precisely aligned with the original distal femoral cut, this avoids the need for additional realignment before recutting the distal femur (Fig. 11.2.7). Also, since jig V slides proximally or distally on the anterior projection of the revision block, it can be positioned to remove a precisely measured amount of distal femur, of virtually any desired thickness.

Figure 11.2.7. Anterior (A) and lateral (B) vies of the revision cutting block and jig V in position for carrying out femoral shortening.

COMPLETING THE TIBIAL CUT AND TRIAL REDUCTION

Once the axial alignment of the tibia can be obtained, the standard technique for removing the proximal tibia is followed. If it is necessary to make a deeper tibial cut because of lateral bone loss, care must be taken to preserve the tibial attachment of the posterior cruciate ligament. Once the cuts have been made, a trial reduction is carried out with the patella resurfaced and the quadriceps mechanism reduced. Varus-valgus and anterior-posterior stability are tested in full extension and at points throughout the range of movement. A slight amount of medial instability is well tolerated if the deformity has been fully corrected. Significant medial instability, however, must be corrected. If the medial instability at this point is only moderate, it may be possible to correct it by simply inserting the next size tibial spacer. Care should be taken to be certain that this does not excessively tense the posterior cruciate ligament, resulting in a block to flexion. An additional minimal lateral release may be necessary to allow insertion of the next thicker tibial component to take up minimal or moderate medial slack. Medial soft tissue advancement will be necessary for significant medial instability.

TECHNIQUE OF MEDIAL SOFT TISSUE ADVANCEMENT

Medial advancement is required for severe (Type II) valgus deformity. The customary skin incision must be extended distally to expose the pes anserinus tendons. The proximal margin of the pes anserinus insertion is identified and a superficial incision is made along the course of this upper border so that the pea group may be retracted distally. Flexion of the knee relaxes the pes group and facilitates the surgery (Fig. 11.2.8). The initial capsular incision is extended further distally, and all soft tissue attached to the medial tibial metaphysis proximal to the pea insertion are reflected posteriorly and proximally as a flap, utilizing careful sharp dissection (Fig. 11.2.9). These tissues include the medial capsule, periosteum, superficial medial collateral ligament, and eventually the posterior oblique portion of the medial collateral ligament. Having elevated this flap, the tibial attachment of the principal medial stabilizers of the knee can be advanced to provide proper axial physiologic balance.

Figure 11.2.8. Initial exposure of the medial capsular structures through reflection of the proximal half of the pes anserinus tendons.
Figure 11.2.9. Sharp dissection of the medial capsular structures including the superficial collateral ligament as a continuous flap.

Tibial component thickness is then selected, based upon that size which provides lateral stability. Reattachment of the capsular-ligamentous flap is performed only after the proper components are permanently seated. With the knee just short of full extension and the components held reduced, the medial flap is advanced distally to provide medial stability and is stapled in place (Fig. 11.2.10). The staples should fix at least the end of the superficial medial collateral ligament and any other substantially thicker portions of the flap. The pes group is then reapproximated and sutured in place.

Figure 11.2.10. Distal advancement and staple fiation of the medial capsular structures after the insertion of the prosthetic components.


Postoperative management differs from the usual protocol in that a knee immobilizer is worn at all times when ambulating. The immobilizer is removed for supervised range of motion exercises. Overall management of the patient’s activity must be determined by the surgeon, who must consider the soft tissue quality, bone and ligament fixation and the patient’s ability to follow instructions. Consideration may be given to postoperative bracing, although this is a rare requirement.

ILLUSTRATIVE CASES

Case P.L. A 79-year-old black woman complained of severe pain and instability in the right knee. Walking tolerance was 1 block. A 40 valgus deformity which was not passively correctible was present. Marked medial instability was evident clinically and radiologically. Roentgenograms demonstrated erosion of the lateral femoral condyle and lateral plateau of the tibia (Fig. 11.2.11). Numerous loose bodies were evident. Patellar subluxation was also present. Preoperative 100-point evaluation rating was 25.

A total knee replacement was performed utilizing the PCA components and the Universal Total Knee Instruments. To bring the knee into correct alignment, femoral shortening of 3 mm and release of the iliotibial tract were necessary. The medial collateral ligament and medial capsule were advanced and fixed with staples. She required one manipulation postoperatively, but otherwise her course was uncomplicated. Active and active-assisted range of motion exercises were started 4 days after surgery, but she was protected with a knee immobilizer during ambulation for 6 weeks. Follow-up at 23 months showed a well-aligned knee with stable range of motion from 0 to 95, unlimited walking tolerance without external support, normal ascent and descent of stairs and, a 95-point rating on the 100-point scale (Fig. 11.2.12).

Figure 11.2.11. Standing film showing severe preoperative valgus deformity and medial joint line opening.
Figure 11.2.12.  Postoperative standing film showing normal alignment of the lower extemity and a horizontal joint line. The staples were used for fixing the advanced medial capsular structures.


Case M.T.
This 83-year-old white woman sustained a distal femoral fracture treated with a blade plate 10 years prior to admission, and subsequently suffered a tibial plateau fracture treated with traction 5 years prior to admission. Over the several months before presenting for this treatment, progressive deformity, pain and instability had rendered her nonambulatory (Fig. 11.2.13). Marked crepitation and patellar subluxation were noted on examination. Motion was limited to 10—80 of flexion. The valgus deformity of 35 was not passively correctible, and marked instability on the medial side was noted clinically and radiologically.

Figure 11.2.13. Preoperative standing and lateral films demonstrate the severe deformity, lateral compartment bone loss and medial side instability.


A total knee replacement was performed through a long medial patellar incision. The blade plate was transected utilizing the diamond wheel on the Midas Rex instrument, and the blade portion was removed. To achieve alignment, the iliotibial tract required Z-plasty as did the biceps femoris tendon, the lateral collateral ligament and the popliteus tendon. Because the complex tibial plateau fracture involved posterior displacement of that portion of the tibial plateau to which the posterior cruciate ligament is attached, Z-plasty lengthening of the posterior cruciate ligament was necessary to achieve adequate flexion. The medial capsule and superficial medial collateral ligament were advanced and fixed with staples. Osteotomy of the tibial tubercle was carried out in order to facilitate adequate exposure without a separate lateral incision. After the lateral structures had been lengthened by Z-plasty, but before the prosthesis was implanted, the peroneal nerve was mobilized to be certain that it was not under stretch with the correction of the deformity. Following this, the lateral structures were repaired through eversion of the extensor mechanism and flexion of the knee. All Z-plasty lengthenings of tendons were repaired with interrupted sutures and the tibial tubercle was reattached with oblique K-wires. Because of significant osteoporosis of the tibial tubercle, the repair was protected with a circumferential wire attached to a transverse bolt in the tibial crest (Fig. 11.2.14).

Figure 11.2.14. Postoperative standing and lateral films show restoration of normal alignment and horizontal joint line. The blade portion of the blade plate has been removed, the medial capsular structures have been advanced and fixed with staples, the tibial tubercle osteotomy has been internally fixed with K-wires and the repair has been protected by a circumferential wire attached to a transverse bolt in the tibial crest.


The patient was managed postoperatively in a splint and subsequently transferred to a continuous passive motion machine. She achieved 90 of flexion at the time of discharge, 4 weeks postoperatively and was independently ambulatory with a walker. At 8-month follow-up, she had 105 of stable flexion, full extension, normal alignment, no pain and a 5-block walking tolerance without support. The preoperative 100-point evaluation scale rating was 10 and the 8-month follow-up rating was 90.

Case K.T. A 42-year-old white man complained of progressively disabling right knee pain, valgus deformity and instability 14 years following a right lateral tibial plateau fracture and 4 years following a right lateral meniscectomy (Fig. 11.2.15). On examination marked patellofemoral crepitus was noted. The valgus deformity was not passively correctible, and there was marked medial instability. Roentgenograms demonstrated lateral tibial plateau depression with narrowing of the lateral joint space, osteophyte formation, subluxation of the patella and 18 of valgus deformity of the knee. A total knee replacement was carried out using the PCA total knee system and the Universal Total Knee Instruments. There was a large lateral plateau defect which required a bone graft using as bone stock the medial posterior femoral condyle which was resected in the course of making the femoral bone cuts. This was internally fixed with three pins. This bone graft provided a flat bed for implanting the resurfacing tibial component. It was therefore possible to implant all three components without methylmethacrylate. A Z-plasty lengthening of the iliotibial tract, popliteus tendon and lateral collateral ligament was necessary to appropriately align the lower extremity. The posterior cruciate ligament was preserved in function throughout the range of movement. The medial capsule and superficial medial collateral ligament were sharply reflected from the medial tibial metaphysis, advanced distally, stapled and reinforced with the pes anserinus tendons.

At 6-month follow-up, he had a well-aligned lower extremity (Fig. 11.2.16), stable range of movement from 0 to 105 of flexion, and no pain. Roentgenograms showed continuing intimate fit of the bone to the prosthetic components (Fig. 11.2.17).

Figure 11.2.15. Preoperative standing films show the degree of deformity, lateral compartment bone loss and medial compartment opening.
Figure 11.2.16. Long standing films postoperatively show restoration of alignment and horizontal joint line.
Figure 11.2.17. Anteroposterior (A) and lateral (B) fluoroscopic spot views at 6 months follow-up show intimate fit of the bone to the prosthetic components and evidence of incorporation of the bone graft to the lateral tibial plateau.


SUMMARY

Severe fixed valgus deformity of the knee often requires special techniques to achieve the operative goal of correction of deformity and correction of instability throughout an adequate range of movement. The alignment of the prosthetic component is not dependent upon the degree of deformity and cannot be varied to accommodate deformity. Therefore, proper positioning of the individual prosthetic components and achieving balanced soft tissue tension throughout the range of movement are interrelated, but nonetheless independent problems. Soft tissue balance can be achieved through igamentous release and/or lengthening combined with the possibility of femoral shortening and advancement of medial capsular structures. The alternatives available in the stepwise progression of the operative procedure have been presented with the rationale for the stepwise decision making which must take place at the various steps in the operative procedure. Operative techniques for lateral ligamentous release, femoral shortening and medial soft tissue advancement have also been presented. Illustrative cases demonstrate the sequence of steps to achieve satisfactory results in difficult cases.

3. Fixed Varus Deformity

Richard S. Laskins, M.D.

True varus deformities as seen in the arthritic patient (Fig. 11.3.1) occur at the joint level, and may be either mobile or fixed. Mobile deformities are correctible passively (Fig. 11.3.2), while fixed deformities are not (Fig. 11.3.3). Many knees demonstrate features of being both fixed and mobile; i.e., a knee may have a varusangulation on standing x-rays of 20, which, with stress, corrects to 10 of varus. The degree to which a deformity is fixed is determined by the severity of soft tissue contracture on the medial aspect of the knee. These structures include the deep capsular ligament, the superficial collateral ligament, the pes tendons, the posteromedial capsule and the posterior cruciate ligament.

There are no fixed rules to explain why some patients develop varus knee deformities, others develop valgus deformities, and still others develop one knee in valgus and one in varus (the so-called wind-swept pattern). As a general (but not inviolate) guide, varus appears to be more common in the short obese patient with osteoarthritis, and somewhat less common in the tall asthenic, or rheumatoid patient (4).


Varus alignment of the leg as measured by the mechanical or anatomical axes may be caused by angulation through the femoral or tibial diaphysis (Fig. 11.3.4). Malunited fractures, or late results of skeletal dysplasias, rather than arthritis, are usually the etiologic causes in these cases. Roentgenograms extending from the hip to the ankle joint must always be obtained preoperatively lest such an angular diaphyseal deformity be inadvertently missed while one concentrated on knee pathology (Fig. 11.3.5).

Figure 11.3.4. Varus deformity due to cartilage loss.
Figure 11.3.5. X-rays of a 65-year-old patient with an overall varus deformity of the leg despite predominantly lateral compartment osteoarthritis. The cause: a malunited fracture of the tibial shaft.

There are three anatomic derangements associated with a varus knee deformity in the arthritic patient: cartilage loss, soft tissue contracture, and bone loss. Although these will be discussed individually, many patients manifest varus deformities on the basis of a combination of two or all three of these factors.

CARTILAGE LOSS

Cartilage loss from the medial femoral-tibial joint space is the basic abnormality in almost every patient with an arthritic varus knee (Fig.11.3.4). This loss causes a diminution of the "spacer height" on the medial aspect of the joint. Varus deformity, due to cartilage loss alone, is generally completely correctible, that is, completely mobile. At surgery, merely restoring the joint height by an implant of sufficient thickness suffices to correct the deformity (Fig. 11.3.6).

Theoretically, if only the medial femoral-tibial cartilage were lost, (Fig. 11.3.7) unicompartmental replacement would be an effective surgical procedure (Fig. 11.3.8). Unfortunately, results for such medial replacement vary widely. Marmor (16) noted excellent results in only 33 of 56 patients (50%), and poor results in over 21%. He still felt, however, that the procedure was a valuable one for general use. It is of interest to note that in his published cases the x-rays revealed that the preoperative varus deformity was not corrected completely at the time of surgery. Mallory and Dolibois (14) stated that they corrected the varus deformity using either the Marmor or polycentric prostheses, and that over 90% of their patients had excellent or good results. Similar, optimistic results were reported by Scott and Santore (18). Englebrecht et al. (3), however, noted a 22% failure rate and Insall and Walker (6) a 26% failure rate. In our series (11), there was a 35% failure rate, the causes of which were manifold: adverse effects of wear particles on the lateral, unreplaced compartment, patellofemoral symptoms, recurrence of the deformity, inadequate initial correction or overcorrection of the deformity. Cartier and Villers (1) have attempted to overcome the alignment problems through a series of preoperative roentgenographic measurements (Fig. 11.3.9) which are then used as guides at surgery to determine implant thickness and placement. Technetium-99 bone scans may be used in a manner analogous to Coventry’s (2) use in tibial osteotomies to ascertain the condition of the lateral tibiofemoral compartment (Fig. 11.3.10). With these types of modifications in technique, unicompartmental replacement may again emerge as a valid procedure. It may especially be useful in the patient with traumatic arthritis due to a previous tibial plateau fracture, or the patient with osteonecrosis of the medial femoral condyle.

Figure 11.3.6. Deformity completely corrected through use of the implant as a spacer.
Figure 11.3.7. "Unicompartmental" osteoarthritis in a 65-year-old man.
Figure 11.3.8. Operative treatment of this patient using unicompartment femoral-tibial resurfacing arthroplasty.
Figure 11.3.9. Preoperative mensuration diagram used in determining size of implant for the arthroplasty.
Figure 11.3.10. Technetium-99 bone scan. The knee on the reader's left has increased uptake most marked in the medial femoral-tibial and patellofemoral compartments (bicompartmental diseases). The knee on the reader's right has increased uptake in both medial and lateral femoral-tibial compartments as well as in the patellofemoral joint space (tricompartmental disease). Neither knee would do well if just the medial compartment were replaced.

BONE LOSS

Bone loss from the medial femoral condyle or the medial tibial plateau can certainly cause varus deformity in the arthritic knee (Fig. 11.3.11). This bone loss results from overload of the subchondral bony areas. With any degree of varus deformity, there is a medial displacement of the force resultant during the stance phase of gait (Fig. 11.3.12) (15). The response is a thickening and buildup of bony trabeculae in the subchondral area as predicted by Wolff (19) and Pauwels (17). As this overload increases, this ability to form new bone is overshadowed by the accumulation of microfractures, and eventually there is bony collapse.

Evaluation of bony loss on the tibial side may be made in the following manner. The anatomical axis is drawn in the standard manner described previously. A line is then drawn joining the superior outer portion of both tibial plateaus. This transtibial line (TTL) normally intersects the tibial portion of the anatomical axis forming an acute angle open medially at 87 3 (approximately 2—3 short of a right angle) (Fig. 11.3.13). Any medial acute angle less than this is an indication that there has been bone loss from the proximal medial tibial plateau (Fig. 11.3.14). A line can also be drawn connecting the most inferior portions of the femoral condyles. This should intersect the axis of the femoral shaft at an angle of between 7 and 11 less than a right angle, (the smaller angle in tall patients, and larger ones in patients with broad pelvis). Any angulation less than 7 between these two lines indicates either actual bone loss from the medial femoral condyle or at least that femoral condylar deformity is participating in the production of abnormal varus.

Figure 11.3.11. Varus deformity due to bony loss from the proximal tibia.
Figure 11.3.12. The resultant of body forces in a varus knee falls completely on the medial plateau.
Figure 11.3.13. The normal transitibial line. It intersects the anatomical axis of the tibia forming an angle of 88° medially.
Figure 11.3.14. An x-ray of a patient with medial plateau bony loss. The transtibial line intersects the anatomical axis of the tibia at an angle of 62°.

Correction of bone loss on the femoral side can be accomplished by adjusting the level of the distal femoral resection line in a manner so that a flat surface for implant support is obtained. Obviously one cannot resect the femur more proximal than the epicondylar insertion of the collateral ligaments. Fortunately for the average case, only small degrees of proximal resection are required.

Correction of bone loss on the tibial side is correctible in at least three ways (13):

1. Make the tibial resection cut at a lower level than normal (Fig. 11.3.15). This method is less applicable when such resection goes well below the tubercle of Gerdy with its iliotibial band insertion. The surgeon must recognize that such resection will cause lateral laxity especially as the knee is brought to full extension.

2. Make the tibial resection cut at the normal level (just below the joint surface) and fill in the resultant defect medially with acrylic cement (Fig. 11.3.16). This method is applicable for smaller degrees of bony loss and works well when the cement remains contained within a circumferential bony bed. When, however, there has been loss of bone extending out to and including the medial cortex, the cement may be unsupported. The use of mesh or supporting screws, although suggested by some surgeons, still places the cement in an unsupported position. In these cases, the third method is applicable.

3. Make the tibial resection at the normal level and bone graft the medial defect (Fig. 11.3.17A). This method is applicable to larger degrees of bone loss when the two previous methods are not feasible. A convenient source of autogenous bone is the posterior aspect of the femoral condyles. Any remaining cartilage is removed from the condylar fragment, and the bone is affixed to the depressed tibial plateau with two counter-sunk cancellous bone screws (Fig. 11.3.17B). The screws are inserted and angled anteriorly and laterally into the tibia. The newly formed plateau is then trimmed to the level of the previously resected lateral tibial plateau, and a standard or appropriate thickness tibial plateau component is used (Fig. 11.3.17C). This method has been used for over 2 years and in 14 cases of severe varus deformity with marked bone loss (Fig. 1 1.3.18A—C). We have not noted any increased settling of the tibial implant nor any increase in radiolucency about the component as compared with a similar group in which bone grafts were not used. In this group of patients, the limb is protected from weight bearing for approximately 12 weeks awaiting incorporation of the bone graft.

Figure 11.3.16. A second method of correcting for bony loss: the resection line is made at the normal subchondral level and the bony defect is filled by cement with or without mesh support; a normal thickness tibial implant is then used.
Figure 11.3.17. (A-C) A third method of correcting bony loss: the resection line is made at the normal subchondral level and the defect filled using bone from the adjacent femoral condyle. The bone is held in place by two countersunk cancellous screws. A normal thickness tibial implant is then used.
Figure 11.3.18. (A-C) A 72-year-old woman with marked bone loss medially. She was treated by grafting the defect using bone from the femoral condyle.

SOFT TISSUE CONTRACTURE

The third anatomic component of varus knee deformity in the arthritic patient is soft tissue contracture on the medial side of the knee (12). This contracture is adaptive, following and perpetuating any varus deformity from either cartilage loss or bony loss. The media! structures, including the deep capsular ligament, the pes tendons, the superficial capsular ligament, and the posteromedial capsule, can all become contracted (Fig. 11.3.19). This contracture is accentuated if there are any medial tibial plateau osteophytes lifting up and tenting the medial capsular ligamentous complex.

Treatment for soft tissue contracture consists first of removing all medial osteophytes from both the tibial plateau and the femoral condyle. Next, the entire medial capsule and deep capsular ligament are elevated as a half sleeve from their attachment to the proximal tibia. The dissection should progress around the tibia posteriorly as far as necessary to release the contracture, separating all the structures inserting onto the metaphysis. For more severe contracture, it may be necessary to elevate the insertion of the superficial collateral ligament and to cross-cut or elevate the attachment of the capsular sleeve and pes tendons distally, allowing the entire medial sleeve to recess proximally (Fig. 11.3.20). In these cases, resection of the posterior cruciate ligament is frequently required for full correction of the deformity. The capsular sleeve may be reattached to metaphyseal bone by staples or it may be allowed to heal without specific fixation in its new proximal position (Fig. 11.3.21). This author has not used fixation in his series and has observed no specific problems while others advocate reattachment of the soft tissue sleeve (5). These patients are routinely kept in a knee splint for approximately 3 weeks to allow this healing to occur.

Figure 11.3.19. Varus deformity in a patient with soft tissue contracture medially; this contracture is accentuated by the prominent tibial plateau7 osteophyte tenting up and tethering the medial structures.
Figure 11.3.20. Capsular release for soft tissue contracture medially.
Figure 11.3.21. The medial capsular flap is allowed to recess proximally.

For varus knees in which there is a combination of cartilage loss, bone loss, and soft tissue contracture, the suggested order of correction is as follows:

1. Resection of tibial plateau and femoral condylar marginal osteophytes.

2. Release of the medial capsular sleeve and, if necessary, proximal recession of the sleeve.

3. Correction of bone loss by one of the three methods described above.

4. Correction for cartilage loss by varying the height of the tibial implant used.

LATERAL SOFT TISSUE ADVANCEMENT

An additional technique for the management of severe varus deformity has been developed by Krackow (7) and employed by Krackow and Kenna (10). This approach involves tightening the soft tissue sleeve on the lateral side of the knee. It is emphasized that most patients with even moderate varus deformity will not require either the bone grafting technique or this lateral advancement. Most patients will tolerate a small to moderate amount of lateral laxity after total knee arthroplasty as long as good postoperative alignment has been achieved. However, with the very severe varus cases, these more extreme methods will be appropriate.

The lateral soft tissue advancement is particularly applicable in the following circumstances:

1. When, after medial soft tissue release and cementing of components, unacceptable lateral laxity exists.

2. When a situation analogous to Type II valgus deformity exists. That is, severe, longstanding varus deformity can create attenuation of the lateral soft structures to such a degree that unrealistic medial soft tissue release would be necessary to achieve ligamentous balance. In these cases, lateral advancement may be considered preferable to medial release.

3. When medial bone grafting seems undesirable either because the bone stock is of questionable quality, or the patient’s ability to comply with protracted partial weight bearing is uncertain.

TECHNIQUE OF LATERAL ADVANCEMENT

A straight incision, slightly posterolateral along the posterior edge of the fibular head, is made from 1 " above the joint line to 2" distal to the tip of the fibular head (Fig. 11.3.22). The peroneal nerve is identified and mobilized posterolaterally dividing the fascial roof created by the peroneus longus muscle where the peroneal nerve crosses the neck of the fibula. Subperiosteal dissection completely around the distal aspect of the fibular neck is performed.

Before osteotomizing the fibula, an appropriately sized hole is drilled from the tip of the fibula, in an intramedullary direction into the proximal fibular shaft (Fig. 11.3.23). This hole is tapped to receive an ASIF 6.5 mm cancellous screw, an ASIF 4.5 mm malleolar screw or a Vitallium lag screw, whichever the surgeon deems most appropriate according to the size of the fibula and the equipment available. It is important that this fixation hole be predrilled to assure accurate positioning of the fibular head after a segment of fibular neck is removed.

An oscillating saw is used to osteotomize the fibula approximately " to 1" distal to the tip of the fibula (Fig. 11.3.24). The osteotomy is made perpendicular to the fibular shaft axis. The resulting proximal fibular piece is grasped with a clamp and carefully dissected free from all capsular and fascial attachments to the lateral surface of the tibia, being careful to preserve the attachment of the biceps femoris tendon and the lateral collateral ligament to this piece of fibula. It is necessary that complete release from the tibia be achieved so that traction on the fibular head is restrained by the femoral attachment of the lateral collateral ligament. Otherwise adequate distal advancement of the lateral ligament will not be possible.

After final implantation of the femoral and tibial components, the knee is held in reduced position at approximately 10-20 degress of flexion. Gentle traction is placed on the fibular head which is brought alongside the remaining fibular shaft (Fig. 11.3.25). The amount of overlapping bone is marked and removed from the fibular shaft with an oscillating saw. Last, the knee is flexed, the tibia externally rotated, and the fibular head fixed with an intramedullary lag screw (Figs. 11.3.26 and 11.3.27). After wound closure the knee is protected in a splint unless a continuous passive motion device is employed. Range of motion, both active and gentle assisted passive motion, is begun in physical therapy at the standard time. Weight bearing during gait is performed for 6 weeks with a knee immobilizer in place, otherwise, postoperative management is identical to other cases of total knee arthroplasty.

Figure 11.3.22. The lateral slightly posterolateral incision is shown retracting the skin and subcutaneous tissues and displaying the fibular head with attached biceps tendon and underlying lateral tendon near the posterior aspect of the incision.
Figure 11.3.23. A preliminary longitundial drill hole is made from the tip of the fibula headed into the fibular shaft. This may be made through a small stab incision in the biceps femoris tissue at the tip of the fibula with the drill entering this soft tissue from its peripheral aspect and then pointing down into the fibular shaft. Alternately it may be possible and even more appropriate to retract the lateral collateral and biceps tendon latterally and drill this longitudinal hole directly into the tip of the fibula.
Figure 11.3.24. The fibula has been divided at the base of the fibular head, the cut being perpendicular to the axis of the fibular shaft. In this figure, the fibular head is shown mobilized from the proximal lateral flare of the tibia and its capsular attachments to the tibiofibular joint.
Figure 11.3.25. The fibular head is now advanced distally with the knee in approximately 10° of flexion. The amount of overlap present as the fibular head is drawn distally along the fibular shaft is marked, thereby determining the level of the second cut in the fibular shaft and the amount of fibula to be removed. It is this removal of a segment of fibular shaft which effects distal advancement of the lateral stabilizers.
Figure 11.3.26. A lag screw is shown in place holding the fibular head in good apposition to the fibular shaft. The surgeon may elect to place a washer under the screw head. If access to the tip of the fibula has been gained from within the soft tissues by retracting the lateral collateral and biceps thendon, then it will probably be necessary to make a stab wound in this soft tissue through which the screw driver is placed to tighten the lag screw. If access to the tip of the fibular was made initially through a stab wound in the tendon and lateral collateral ligament, then the screw is inserted through this same stab wound and tightened in standard fashion.
Figure 11.3.27. An anteroposterior view showing the lag screw in place holding the fibular head against the fibular shaft.

The procedure described provides good lateral stability with quite secure fixation of the advanced lateral soft tissues. Problems at the fibular osteotomy regarding the bone or peroneal nerve have not been observed in a small series of patients. Studies by Krackow and Brooks (8,9) demonstrate the safety of distal advancement of a lax collateral ligament with regard to maintenance of proper ligament tension throughout the motion cycle. Furthermore, the dissection employed and the management of the fibular head and lateral stabilizers are not too different from what one does during high tibial osteotomy for varus deformity.

CONCLUSION

Whether varus deformity is best managed by simple soft tissue release with osteophyte removal, major medical ligamentous revision, medial bone grafting, or lateral ligament advancement will depend upon many factors dependent upon the particular case at hand.

The one method that should not be used in correcting a varus deformity is that in which the resection plane of the proximal tibia is angulated. With such an approach, one or both of the following will occur. The prosthetic joint line will not be parallel to the floor in normal stance and/or residual varus deformity will be present. Asymmetrical loading will occur and premature loosening and increased cold flow can be expected. Protocols which suggest or require such resection and which do not suggest correction of soft tissue contractures when present should be viewed with great skepticism.

4. Fixed Flexion Contracture

Kenneth A. Krackow, M.D.

The previous sections addressing the handling of fixed varus and fixed valgus deformities have introduced some of the basic problems inherent in total knee arthroplasty when significant preoperative deformity exists. The problems encountered in the patient with severe flexion contracture derive from the same basic principles but present considerably different problems with regard to surgical technique, postoperative stability, and postoperative management.

Before addressing the surgical techniques and the pre- and postoperative regimens, the basic principles which lead to problems for the flexion contracture cases will be outlined. From the introduction to this chapter and the previous sections it should be clear that fixed deformity implies relative tightness of soft tissue structures at the concave side of the deformity, which, in the case of flexion contracture, is the posterior aspect of the knee. Certainly, the knee can always be brought into full extension by resecting a sufficient amount of bone from the distal femur and proximal tibia (Fig. 11.4.1). It would appear, initially, that this approach to the problem with treating fixed flexion contracture by generous bone resection as postoperative rehabilitation, and attention to the potential quadriceps lag would be all that were necessary.

The knee is, in this case, the convex side of the deformity; and the convex side of the deformity possesses a relative surplus of the soft tissue sleeve. One might predict in this line of reasoning, that with the quadriceps being a dynamic mechanism, there would not be any great problem with treating fixed flexion contracture by generous bone resection as postoperative rehabilitation, and attention to the potential quadriceps lag would be all that were necessary.

Such a cursory analysis of the flexion contracture situation is far from correct. As one corrects the deformity by bone resection alone, and as the knee is brought into extension, it is true that the surrounding soft tissue sleeve bulges anteriorly. In fact, most of the bulge is anterior, but there is also a bulge or surplus of soft tissue medially and laterally. This is demonstrated by Figures 11.4.1 and 11.4.2. Diagrammatically it is seen that with removal of bone to permit full extension, the anterior soft tissues bulge, or a relative quadriceps laxity develops. However, as the points on the medial and lateral sides of the knee come together with such bone resection, Figure 11.4.2 demonstrates how significant collateral laxity develops.

Figure 11.4.1. Sufficient distal femur and proximal tibia bone have been removed to allow full extension while providing space for the prosthesis. In the lateral view, the posterior soft tissues are shown without any laxity. Major laxity or redundance of tissue is seen to exist anteriorly at the extensor mechanism. Secondary laxity also develops in the collateral ligaments as shown in the anteroposterior projection.
Figure 11.4.2. The reason for the development of collateral laxity is shown in this line drawing. With removal of bone comprizing the trapezoidal region in the flexed, lateral figure, points a and b anteriorly approach one another. The tissue spanning this area obviously becomes redundant as seen in the extended lateral view. However, as point a approaches point b, so also point c approaches point d, and when viewed in the anteroposterior projection a definite but less severe redundancy of tissue is seen to develop in the region of the collaterals.

One important problem with the development of such collateral laxity is the fact that its presence may go totally unnoticed. As the surgeon brings the knee into maximal extension and assesses the overall situation, the posterior soft tissues become tight, blocking further extension or recurvatum. Not only do these posterior tissues block further extension or hyperextension, but they also provide medial and lateral stability if the knee is held in a position of maximum extension with these posterior tissues taut. However, as soon as even slight flexion is performed and the posterior tether is released, gross collateral laxity will be evident. In this general situation, there is not as much laxity in the medial and lateral tissue as there is anteriorly; however, the resulting laxity may still be functionally quite significant.

To summarize, bone resection alone to correct fixed flexion contracture can lead to collateral instability on both the medial and lateral sides of the knee and, furthermore, this laxity will generally not be evident if collateral stability is tested in maximal extension. The problem of collateral laxity after bone resection for the flexion contracture case has implications for some cases of pure valgus or pure varus fixed deformity. While a primary soft tissue imbalance after bone resection is, obvious on the convex and concave aspects of the knee, the flexion contracture situation illustrates how a secondary, less obvious soft tissue imbalance occurs on the sites "adjacent" to the main deformity. For the flexion contracture case, the secondary imbalance is seen to be medial-lateral. If bone resection alone is used to correct alignment in pure valgus or varus cases, the same type of secondary imbalance produces soft tissue laxity in the anterior and posterior aspects of the knee. The primary imbalance is certainly medial or lateral, but this secondary imbalance does occur, i.e., quadriceps lag and recurvation. This is not merely a theoretical consideration but rather is a clinical fact worth appreciating.

Removing bone to allow correction of the flexion deformity means that a larger amount of bone is resected than is replaced by the femoral and/or tibial components. As a result, the relationship of the attachment points of the ligaments to the resulting prosthetic joint line is altered. Aside from the general collateral laxity that can be expected to result, this relocation of the joint line with respect to the ligament attachment positions invites more specific problems.

It is seen in Figure 11.4.3 that bone resection from the distal femur alters and shortens the ligament separations in extension while changing them relatively little in flexion. It could be suggested that, in the case of flexion deformity, additional bone should be removed from the distal femur only. Although the collateral ligaments themselves would be lax in extension, the posterior soft tissues may provide medial-lateral stability at full extension and, with flexion, the collaterals would tighten and function normally. There is truth to this, but the problem can present that distal femoral bone resection is limited by the femoral attachments of the collaterals as well as the posterior cruciate ligament if there is hope of sparing this. If the surgeon were relying upon bone resection alone to correct the flexion contracture, he may then be forced to turn to the tibial side because of the proximity of the collateral ligament origins.

The "catch 22" is that when bone is resected from the tibia in order simply to achieve full extension, an inappropriate gap is created between the tibia and the posterior femur when the knee is brought into flexion.

This situation is shown in Figure 11.4.4. Note that bone has been excised simply to allow full extension. Implantation of the prosthesis cannot take place until further femur and proximal tibia are removed equal to the dimensions of the prosthesis. Otherwise, the flexion contracture would persist. As a result, the relative gap shown in the diagram will still exist with the knee in flexion even after prosthetic implantation.

Figure 11.4.3. Initial or extra resection of distal femur allows collateral ligament attachment points to approach one another when the knee is in extension. However, with maintenance of the posterior femoral condyles, these attachment points remain normally separated when the knee is flexed. In this manner, preliminary or relatively greater distal femoral excision promotes collateral laxity in extension and not in flexion.
Figure 11.4.4. The effect of preliminary or excessive tibial resection is shown in this series of drawings. Bone has been removed in the upper right figure to allow full extension without recurvatum, i.e., with the posterior tissue tight and no space between the distal femur and proximal tibia with the knee held in full extension. When the knee is flexed, however, the gap due to the excised tibial bone appears and a relative laxity in flexion is evident.

This lengthy analysis and discussion has been presented not to show that fixed flexion contracture is an impossible situation to handle, but rather to describe its complexity and offer insight into what is or can be happening when one relies partially or totally on bone resection to correct the flexion deformity. Cases with as much as 65 degrees of fixed flexion contracture have been handled quite successfully with standard condylar types of prostheses. They are possible, but not simple.

With this background it is possible to appreciate how important it is to attempt to correct fixed flexion contracture by means other than, or in addition to, simple bone resection at the time of surgery.

PREOPERATIVE CORRECTION

Where practical, strong consideration should be given to correction of the fixed flexion contracture prior to total knee arthroplasty. The first nonsurgical approach beyond physical therapy is serial casting, even under anesthesia, if necessary. Serial casting for flexion contracture does several undesirable things, however. It creates pressure anteriorly on the skin over the knee and posteriorly at the Achilles tendon. The potential problems of pressure sores ought to be outlined to all patients undergoing serial casting.

Serial casting also creates a painful compression at the joint surfaces and promotes further degeneration of articular cartilage. While effects on intact articular cartilage are of concern for people with less degenerated joints, other than the attendant discomfort, such is not a concern for the patient who is to undergo total knee replacement. At this stage lateral x-rays are suggested to evaluate objectively the progress of correction during serial casting.

If serial casting is impractical or when it is terminated and deformity persists, consideration can be given to posterior soft tissue lengthening. Longitudinal posteromedial and posterolateral incisions may be preferred. They permit Z-plasty lengthening of the hamstring tendons, exposure of the peroneal nerve, and division of the posterior capsule without direct exposure of the popliteal vasculature and with minimal interruption of lymphatic drainage. Intra-articular pathology, it must be remembered, may be a major obstacle to straightening, and so one must palpate structures before releasing or lengthening them to be certain that such action will be helpful. The lateral knee x-ray of a 71-year-old rheumatoid patient demonstrates how a posterior soft tissue release would be doomed to failure (Fig. 11.4.5). The joint contours and severe degeneration in this case were such that further extension could not be achieved by posterior soft tissue release.

Posterior release, if at all successful, can be followed by serial casting.

Figure 11.4.5. Lateral x-rays of an elderly patient's rheumatoid knee demonstrate impressive molding of femoral and tibial joint surfaces. In this case, the irregular joint contours prevented extension despite posterior soft tissue release.

INTRAOPERATIVE CORRECTION

When moderately severe flexion contracture exists, greater than 30, after full exposure of the joint, this author will generally perform a preliminary resection of the distal aspect of the femoral condyles, removing 3-5 mm of bone. This maneuver avoids having to remake the anterior and posterior cuts as well as the distal cut later in the procedure. After this preliminary resection, the distal, anterior, and posterior femoral cuts are made. Next, any anterior tibial osteophytes blocking full extension are removed. In fact, if these are obvious, and especially in milder cases, they should probably be removed first.

With the use of a lamina spreader, while the knee is flexed 90, division of the posterior capsule is carefully performed. A perforation is made through the capsule behind the medial or lateral compartment, and a right angle clamp is used bluntly to dissect adjacent tissue away from the capsule prior to sharp division. If insufficient room for this dissection exists, some proximal tibia is removed (Fig. 11.4.6).

Figure 11.4.6. A lamina spreader is used to help gain access to the posterior capsule while capsular incision is being performed.

Additionally, the knee may be hyperflexed and with a periosteal elevator the attachments of the gastrocnemius heads elevated from just above the posterior femoral condyles. If full extension is still not achieved, a few more millimeters of proximal tibia are removed.

At this point, if correction is still imperfect, the options remaining are: 1) even more generous distal femoral or tibial resection, 2) hamstring lengthening, or 3) reliance on postoperative casting. Sometimes the posterior skin will feel tight and theoretically Z-plasty release could be performed. Surgical exposure as well as skin circulatory conditions would be unfavorable. This author has no experience with such "skin lengthening" and would not feel comfortable recommending it. The usual course at this stage is greater tibial resection and use of postoperative casting.

If full extension simply cannot be achieved, then the Universal Total Knee Instrumentation System described in Chapter 4 cannot be used in standard fashion, and instrumental improvisation must begin. An additional 6-7 mm of tibial bone is marked for resection. The line of the transverse tibial cut is marked with the aid of the alignment guide, and jig V can be secured to the tibia with 1/8 " drill pins to help with the accuracy of the cut. Care must be taken to orient the cut perpendicular to the axis of the tibia on viewing from the lateral aspect.

According to the discussion above, and this author’s experience, after performing the transverse tibial cut and achieving a trial reduction of the components, moderate to moderately severe medial and lateral instability may be evident. It is important to realize that this instability will generally not be evident when the knee is brought out to maximum extension, but will be relatively impressive as soon as the knee is even mildly flexed. An understanding of the phenomenon is important.

With the performance of a valgus stress test, the surgeon is attempting to detect medial opening and to effect rotation of the tibia with respect to the femur within the coronal or transverse plane and about a point somewhere within the lateral femoral portion of the knee. Any posterior soft tissue structures bridging the joint which are tight as a result of maximal extension, and which in this example lie medial to the axis of attempted rotation, will tend to prevent medial opening. However, as soon as these posterior structures are slightly relaxed, in the absence of a competent primary medial stabilizer, the medial side of the knee opens to valgus stress. This is the same phenomenon as that which occurs when one notes relatively good medial stability in forced full extension, despite medial collateral ligament injury when the posterior capsule and posterior cruciate ligament are not torn or significantly stretched.

Despite the presence of collateral instability as described above, the author has not had or seen a case where proximal or distal collateral ligament advancement was undertaken for pure flexion contracture deformity. However, this would be considered if the resulting collateral instability were obviously unacceptable. Generally, it is sufficient to plan for a simple knee cage or Lenox Hill brace in the more unstable cases and to allow the patient to convalesce. One patient in the author’s series for whom long-term use of a Lenox Hill brace was prescribed had 45 of fixed flexion contracture and 45 of valgus preoperatively. She discarded her brace at 8—9 months postoperatively as she found it unnecessary.

Immediately postoperatively, patients are placed in either a Jones dressing with a posterior plaster splint or a cylinder cast which is bivalved in the recovery room. Their flexion contractures have a great tendency to recur in the early postoperative period. A patient treated with a bivalved cylinder cast can have the cast replastered at 3—4 days postoperatively and then wedged into further extension if this is necessary to address residual flexion deformity. Those with casts have them removed by 7—8 days postoperatively unless there is some strong reason to retain this support. If such is the case, a manipulation under anesthesia is routinely performed sometime between the 7th and 14th day postoperatively. Most of the patients are managed without casts, that is, relying on splints, if necessary. However, for the more severe cases and when correction has been clearly incomplete, casting may be indicated.

It is very difficult to predict which patients, who start with fixed flexion contractures and persist with some fixed flexion contracture at 7— 14 days postoperatively, will correct with ordinary physical therapy. With resurfaced joints, some experience enough pain relief that they are able, gradually, to stretch out their flexion contracture. Others have too much muscle spasm and a 10—20 flexion contracture can persist. Despite this resistance in some cases, the flexion contracture patients as a group still achieve good results in that a mild residual flexion contracture does not generally present a major problem (Fig. 11.4.7).

Figure 11.4.7. Postoperative views of a 71-year-old patient with rheumatoid arthritis who had been nonambulatory with bilateral 65-70° knee flexion contractures.

Certainly, fixed flexion contracture is among the most difficult of total knee replacement situations. These cases are not easy to treat successfully and one cannot expect to get every patient with severe preoperative deformity to full extension permanently. However, these patients have lived and walked for many years with much greater flexion contracture than they have postoperatively and when their joints are resurfaced and their contracture moderately improved, they still may achieve, as far as they are concerned, a quite satisfactory final result.

References

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