Lateral femoral sliding osteotomy

Transcription

1 Lateral femoral sliding osteotomy LATERAL RELEASE IN TOTAL KNEE ARTHROPLASTY FOR A FIXED VALGUS DEFORMITY J. Brilhault, S. Lautman, L. Favard, P. Burdin From Trousseau University Hospital of Tours, France W e treated 13 patients who had a fixed valgus deformity of the knee with a semiconstrained total knee arthroplasty combined with advancement of the lateral collateral ligament by means of a lateral femoral condylar sliding osteotomy. At follow-up of between one and 6.5 years all patients were assessed using the Knee Society score. The mean knee score improved from 32 to 88 and the functional score from 45 to 73. The mean tibiofemoral angle was corrected from 191 to 180. There was no postoperative tibiofemoral or patellar instability and, in most knees, distal transposition of the lateral femoral condyle achieved satisfactory stable alignment. J Bone Joint Surg [Br] 2002;84-B: Received 17 September 2001; Accepted after revision 26 February The importance of restoring mechanical alignment after total knee arthroplasty (TKA) is widely accepted. This, however, may be difficult in the presence of a fixed valgus deformity. 1 Good overall alignment with a horizontal tibiofemoral joint line is obtained when the bone cuts are perpendicular to the mechanical axis of the femur and the tibia. In doing this, however, the tibiofemoral gap created may have a trapezoidal shape, implying imbalance of soft tissues when using a standard, semiconstrained prosthesis. Two options have been proposed to correct such an imbalance. One is to tighten the medial collateral ligament, 2,3 and the other, used by most surgeons, is to release the lateral supporting structures. 1,2,4-9 The second option, especially when releasing the lateral collateral ligament (LCL), is still con- J. Brilhault, MD S. Lautman, MD L. Favard, MD, Professor of Orthopaedics P. Burdin, MD, Head and Professor of Orthopaedics Department of Orthopaedic Surgery and Traumatology, Trousseau University Hospital of Tours, Tours Cedex, France. Correspondence should be sent to Dr J. Brilhault British Editorial Society of Bone and Joint Surgery X/02/ $2.00 troversial and may cause postoperative mediolateral instability. 10 In order to prevent such instability we have developed a balancing technique using a sliding osteotomy of the lateral aspect of the lateral femoral condyle. It allows precise lengthening of the lateral structures while internal fixation by screws gives immediate stability and allows normal postoperative care. We now review the results of this technique in TKA for a fixed valgus deformity. We attempt to evaluate the amount of slide needed to achieve a rectangular tibiofemoral gap. Patients and Methods Between January 1994 and August 1999, 96 patients with valgus deformities underwent TKA. Thirteen presented with fixed valgus deformities (i.e. the valgus deformity was not passively correctable) and required a specific ligament balancing procedure to achieve correction of the deformity and proper ligamentous stability (Table I). There were 12 women and one man with a mean age at the time of surgery of 73 years (69 to 81). The diagnosis was osteoarthritis in 12 knees and rheumatoid arthritis in one. A lateral Keblish approach was used in 11 knees and a medial parapatellar approach in two. A tibial tubercle osteotomy was carried out in seven knees to facilitate exposure but not for distal patellofemoral realignment. A posterior stabilised prosthesis was used in 12 knees and a cruciateretaining design in one (Genesis I and II; Smith-Nephew- Richards, Memphis, Tennessee). Data were collected according to a prospectively designed protocol. All preoperative evaluations and surgical procedures were carried out by the two senior authors (LF and PB). All follow-up evaluations, and the assessment of the results, were by those who were not directly involved with the patients. The hospital records were reviewed and the pre- and postoperative radiographs re-evaluated. Clinical and radiological evaluations were done before and at a minimum of one year after surgery. Special attention was given to laxity in the frontal plane. The varus and valgus examination was undertaken in a routine clinical manner with the knee flexed to 20. Laxity was measured subjectively in degrees as follows: none (0 to 5 ), mild (6 to 9 ) and moderate (10 to 14 ) and recorded independently for the lateral and medial sides (Table II). Clinical data were summarised VOL. 84-B, No. 8, NOVEMBER

2 1132 J. BRILHAULT, S. LAUTMAN, L. FAVARD, P. BURDIN Table I. Clinical details and Knee Society scores (maximum 100) for the 13 patients who required lateral release in TKA for a fixed valgus deformity Preoperative Follow-up Case Age (yrs) Gender Functional score Knee score Months Functional score 1 75 F F F F F M F F F F F F F Mean Knee score Table II. Medial and lateral laxity recorded preoperatively and at followup for the 13 patients who required lateral release in TKA for a fixed valgus deformity Preoperative Follow-up Case Medial laxity Lateral laxity Medial laxity Lateral laxity 1 None Mild Mild None 2 Mild None None None 3 None Moderate None None 4 None Moderate Mild None 5 None Mild None None 6 None Moderate Mild Mild 7 Mild Moderate None None 8 None None Mild None 9 None Mild None Mild 10 None Moderate Mild None 11 None Mild None None 12 None Mild Mild None 13 None Moderate None Mild using the 100-point scoring system developed by the Knee Society. 11 For radiological evaluation we used long-leg standing anteroposterior radiographs, with lateral and skyline views. 12 Alignment of the knee is reported here as the tibiofemoral mechanical angle (TFMA, Fig. 1). 4 The femoral mechanical axis was defined as the line drawn between the centre of the femoral head and the centre of the knee. The tibial mechanical axis was defined as a line drawn between the centre of the knee and the centre of the ankle. The TFMA was measured as the angle formed medially at the knee by the intersection of the femoral and tibial mechanical axes. The tilt of the femoral condylar surface was measured by the condylar-hip angle (CHA), defined as the angle formed medially between the femoral mechanical axis and the femoral knee joint line. The angle of the tibial plateau was measured by the plateau-ankle angle (PAA), defined as the angle formed medially between the tibial mechanical axis and the tibial knee joint line. 13 Patellar height was measured on a lateral view with the knee in 30 of flexion. We used the method of Insall and Salvati 14 to describe the patellar height and that of Caton et al 15 to describe the patellar articular height in relation to the tibiofemoral joint line. Using the skyline view, the tilting angle and the lateral shift of the patella were measured (Fig. 2). 16 The patellar tilt was defined as the angle between a line from the anterior limits of the femoral condyles and the equatorial line of the patella preoperatively, or a line drawn along the prosthesis-bone interface postoperatively. A medially open angle was defined as positive. Patellar lateral shift was defined as the distance between the crest of the patella and a line drawn through the central area of the femoral condyles. Postoperatively, we used the centre of the patellar prosthesis. A lateral translation was defined as positive. For statistical analysis we used the Wilcoxon rank test. Significance was accepted at a p value of less than Operative technique. We use a lateral parapatellar approach. The musculature of the anterior tibial compartment and the iliotibial band from Gerdy s tubercle are elevated subperiosteally. The meniscal-capsular-fat-pad flap is everted on the lateral inferior geniculate artery according to Keblish. 5 In severe valgus deformities, a stepcut osteotomy of the tibial tubercle is required to facilitate exposure and patellar eversion. Both cruciate ligaments are usually sacrificed. A retropatellar osteotomy, parallel to the anterior surface of the patella, is completed first. The thickness of the patellar button is chosen to approximate to the patient s own patellar thickness. Intramedullary instrumentation is used to fashion the distal femoral bone cut perpendicular to the femoral mechanical axis and based upon the preoperative radiographs. The medial femoral condyle is used as a reference to determine the level of distal femoral resection in order to remove an amount of bone medially which corresponds to the thickness of the femoral component. This preserves the level of the prosthetic joint line. Posterior condylar osteotomies are undertaken in the same way allowing for any erosive changes at the back of the lateral con- THE JOURNAL OF BONE AND JOINT SURGERY

3 LATERAL FEMORAL SLIDING OSTEOTOMY 1133 Shift Tilt CHA Fig. 2a PAA TFMA Shift Tilt Fig. 1 Diagram showing alignment of the lower limb: tibiofemoral mechanical angle (TFMA), condylar hip angle (CHA) and plateau-ankle angle (PAA). Fig. 2b Diagram showing patellar axial positioning a) before operation and b) at follow-up. dyle. The posterior condylar line is used as the sole rotational reference. A proximal tibial cut perpendicular to the tibial mechanical axis is undertaken using extramedullary instrumentation. The resection is based on the medial tibial plateau. Once the bone cuts are achieved, the tibiofemoral gap is trapezoidal in shape. A lateral release is then required to correct the deformity and allow a rectangular tibiofemoral gap (Fig. 3). This requires a lateral femoral sliding osteotomy which is performed as follows (Fig. 4). Step 1. Using a thin reciprocating saw, a frontal cut is made at the distal angle of the anterior chamber parallel to the anterior femoral cortex. Step 2. An axial cut is then made perpendicular to the first cut, at the proximal part of the posterior condyle resection. Step 3. A sagittal cut is then made perpendicular to both first cuts. It separates a bone block which includes the insertions of the LCL and popliteus, and should be at least 5 mm thick. Step 4. The bone block is retracted to give access to the posterior compartment of the knee. A capsulotomy is undertaken along the proximal border of popliteus from the bone block to the midline. This is important to prevent a flexion contracture. Fig. 3 Diagram showing correction of the deformity and achievement of a rectangular tibiofemoral extension gap. VOL. 84-B, No. 8, NOVEMBER 2002

4 1134 J. BRILHAULT, S. LAUTMAN, L. FAVARD, P. BURDIN Step 1 Step 2 Fig. 4a Fig. 4b Step 3 Step 4 Fig. 4d Fig. 4c Diagrams of the lateral femoral bone block osteotomy showing a) the anterior cut (step 1), b) the proximal cut (step 2), c) the final cut (step 3), and d) the posterolateral capsulotomy (step 4). The best position for fixation of the bone block is determined using spacer blocks. Rectangular tibiofemoral gaps must be obtained both in flexion and extension. The distal slide of the bone block is adjusted with the knee extended with the appropriate spacer (Fig. 3). The posterior slide may be adjusted in the same way if necessary. The bone block is temporarily held by Kirschner wires to check the ligamentous tension and the stability of the knee. Two or three 3.5 mm screws are used for final fixation. The screw length usually corresponds to the thickness of the lateral condyle. Care THE JOURNAL OF BONE AND JOINT SURGERY

5 Table IV. LATERAL FEMORAL SLIDING OSTEOTOMY 1135 Table III. The tibiofemoral alignment pre- and postoperatively and at follow-up for 13 patients who required lateral release in TKA for a fixed vagus deformity Tibiofemoral mechanical angle (degrees) Condylar-hip angle (degrees) Plateau-ankle angle (degrees) Case Preoperatively Follow-up Preoperatively Follow-up Preoperatively Follow-up Mean Radiological patellar patterns preoperatively and at follow-up for the 13 patients who required lateral release in TKA or a fixed valgus deformity Tilt (degrees) Lateral shift (mm) Caton 15 method Insall-Salvati 14 method Case Preoperatively Follow-up Preoperatively Follow-up Preoperatively Follow-up Preoperatively Follow-up Mean should be taken not to interfere with the cruciate-substituting box. Any prominent bone is trimmed in order to accommodate the trial femoral component. In our experience this has never threatened the insertions of either the LCL or popliteus. With the knee now ready for a trial reduction an appropriate thickness of tibial insert is determined and the tibial component rotated into its correct alignment with the femur. Patellar stability is finally checked. After the components have been cemented, the lateral soft-tissue gap in flexion is determined after self-adjustment of the patellar tendon. The lateral composite flap is tailored to fill that gap in a tension-free manner. Skin closure over a drain is carried out in a routine tension-free fashion. A bulky compression dressing with splints is used for approximately three days. Rehabilitation is not delayed since internal fixation gives immediate stability and allows full weight-bearing and normal postoperative care. Results A constrained prosthesis has not been required after ligament balancing because of instability. All patellae were resurfaced and all components were cemented. The degree of transposition of the bone-block which was required in order to obtain a rectangular tibiofemoral gap, in both flexion and extension, was a distal displacement alone in 12 knees and a combined distal and posterior displacement in one. Although significant, the transpositions were sufficiently small not to threaten the insertion of the LCL and popliteus when trimming any prominent bone. There were five complications. Four patients developed a deep-vein thrombosis which was confirmed by Doppler examination, one had a superficial wound problem and one developed a pseudarthrosis of the sliding osteotomy. Reoperation was necessary for this last patient because of pain, albeit without instability. Bony fusion was achieved with a satisfactory outcome. There were no cases of palsy of the peroneal nerve or of patellar instability. The mean follow-up was 56 months (12 to 78). All patients were satisfied with the result of their operation and reported decreased pain and improved function. At followup, some degree of medial or lateral laxity persisted in eight knees (12 knees had medial or lateral laxity preoperatively). The clinical details are shown in Tables I and II. VOL. 84-B, No. 8, NOVEMBER 2002

6 1136 J. BRILHAULT, S. LAUTMAN, L. FAVARD, P. BURDIN Fig. 5a Fig. 5b Case 12. Radiographs a) before operation and b) at follow-up. Radiological examination. The mean alignment of the limb had been corrected from 191 (183 to 203) to 180 (173 to 185) after operation. No patient had a significant change in patellar height as measured by the Insall-Salvati method. 14 Using the method of Caton et al, 15 the patellar articular height decreased, but stayed within the normal range (0.82 to 1.12). The patellar tilt increased and the lateral shift decreased. Radiological data are detailed in Tables III and IV. Discussion The technique of ligamentous balancing by lateral femoral sliding osteotomy was successful in restoring stable alignment in most patients with a fixed valgus deformity when using semiconstrained TKAs (Fig. 5). The most challenging aspect of a TKA in the presence of a valgus deformity is to conserve ligamentous stability after limb alignment. It is our view that this is possible by doing the bone cuts first and then respecting the LCL during ligament balancing. Primary bone cuts allow positioning of the components perpendicular to the mechanical axis of the limb. Once the bone cuts have been done achievement of a rectangular flexion-extension tibiofemoral gap implies a lateral opening of the tibiofemoral gap. Two structures are then involved, the posterior cruciate ligament (PCL) and the lateral stabiliser of the knee. The PCL provides a central pivot point which limits the lateral opening and suggests that it should be divided. Among the lateral structures, the iliotibial band is a secondary lateral stabiliser of the knee in extension. 11 Subperiosteal elevation from Gerdy s tubercle, in continuity with the anterior tibial fascia, which is offered by the lateral approach, allows sufficient exposure and lateral release. The lengthening of the iliotibial band by Z-plasty, VY-plasty, transverse section or multiple puncture techniques may allow excessive correction and lead to secondary instability in extension. As cadaver and surgical studies suggest, the LCL is the primary lateral stabiliser of the knee. When released, it allows greater distraction of the lateral space in flexion than in extension. 11 In our experience, release of the LCL allows a wide opening of the lateral aspect of the joint. This may be excessive and produce lateral instability in flexion. Alignment in the presence of a fixed valgus deformity implies the need for lengthening of the LCL just as lateral stability implies its retention. Krackow 2 proposed re-approximating the distal tendinous stump of the popliteus tendon to the distal remnant of the LCL in order to manage this problem, but secondary stretching of the repair may produce lateral instability. A lateral femoral sliding osteotomy allows precise lengthening of the LCL in the desired plane without producing excessive lateral opening in flexion. Internal fixation gives immediate stability and permits normal postoperative management, and bony fusion prevents secondary lengthening. Pseudarthrosis of the osteotomy is, however, the principal pitfall of the technique. Care must therefore be taken to achieve primary stability with good internal fixation. This is not always easy in the presence of significant osteoporosis. In such knees we suggest the use of a one-third tubular plate applied as a tension-band plate. The authors gratefully thank Mr T. J. Wilton, MA, FRCS, of the Derbyshire Royal Infirmary for his editorial assistance in the preparation of this manuscript. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. References 1. Stern SH, Moeckel BH, Insall JN. Total knee arthroplasty in valgus knees. Clin Orthop 1991;273: Krackow KA. Deformity. In: The technique of total knee arthroplasty. Baltimore: CV Mosby, 1990: THE JOURNAL OF BONE AND JOINT SURGERY

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