BACKGROUND: Distal femoral varus osteotomy is a procedure that is performed for the treatment of lateralcompartment osteoarthritis of the knee as well as for correction of the associated valgus deformity. However, its role remains controversial and its efficacy in the treatment of associated patellofemoral arthritis has not been well studied. The purpose of the present study was to evaluate the outcome after distal femoral osteotomy performed for the treatment of painful genu valgum and to assess the influence of patellofemoral arthritis on the results.
METHODS: Thirty patients (thirty knees) were managed with distal femoral varus osteotomy for the treatment of noninflammatory lateralcompartment arthritis of the knee associated with a valgus deformity. Twelve knees had isolated lateral-compartment arthritis, ten had mild-to-moderate degenerative changes in the other two compartments, and eight knees had severe patellofemoral arthritis in addition to lateral-compartment disease. The osteotomy site was fixed with a 90° blade-plate. After a mean duration of follow-up of ninety-nine months, all patients were evaluated with use of the Hospital for Special Surgery knee-rating system and a physical examination.
RESULTS: At the time of the most recent follow-up, twenty-five patients (83%) had a satisfactory result and two had a fair result according to the Hospital for Special Surgery rating system. The remaining three patients had had a conversion to a total knee arthroplasty. With conversion to total knee arthroplasty as the end point, the cumulative ten-year survival rate for all patients was 87% (95% confidence interval, 69% to 100%). Improvement in patellar tracking, which persisted at the time of the latest follow-up, was observed in seven of the eight knees with associated severe patellofemoral arthritis.
CONCLUSIONS: Distal femoral varus osteotomy with blade-plate fixation can be a reliable procedure for the treatment of lateral-compartment osteoarthritis of the knee associated with valgus deformity. The result of the osteotomy does not appear to be affected by the presence of severe patellofemoral arthritis.
The preferred site of the osteotomy for lateral-compartment osteoarthritis of the knee is the distal aspect of the femur if the valgus deformity is ≥12°1. However, the results of distal femoral osteotomy have varied. The most common complications of this procedure are non-union and failure of the internal fixation2. To achieve a high union rate, rigid fixation and good apposition of the osteotomy site are required. In this report, we describe a technique in which a blade-plate and a derotation screw are used to perform the distal femoral varus osteotomy.
Our technique is based on the method described by McDermott et al.3, with some modifications. The patient is placed in the supine position. A longitudinal medial incision, which is about 1 cm medial to the anteromedial incision used for primary total knee arthroplasty, is made on the distal part of the thigh beginning from the joint line of the knee and extending proximally for 15 cm. The vastus medialis is freed from the medial intermuscular septum and is reflected laterally to expose the medial femoral condyle and the femoral cortex. Care is taken to protect the femoral vessels in the adductor canal by elevating them through subperiosteal dissection of the medial femoral cortex throughout the procedure. A medial arthrotomy of the knee is performed to visualize the abnormality of the articular surface of the knee.
The knee is slightly flexed and externally rotated. A guidewire is passed from the medial part of the knee through the joint space to the lateral part of the knee parallel to the articular surfaces. A second guidewire is inserted into the medial femoral condyle 2 cm proximal to and parallel to the first guidewire (Fig. 1). A third guidewire is inserted medially into the distal aspect of the femur at about the upper margin of the anterior part of the articular surface of the femoral condyle and parallel to the second guidewire (Fig. 2). An anteroposterior radiograph is made at this time to confirm that the second and third guidewires are parallel to the joint line (Fig. 3).
A 4.5-mm drill is used to perforate three holes in the medial cortex of the femoral condyle proximal to the line of the second guidewire (Fig. 4). A chisel is inserted through the perforated holes and in a direction from the anterior half of the medial femoral condyle to the posterior half of the lateral femoral condyle parallel to the second guidewire and to a depth of 50 or 60 mm, depending on the size of the femoral condyle4 (Fig. 5). A fourth guidewire passing through the anterior surface of the femoral condyle may be necessary at this point to guide the direction of the chisel. Note that the long arm of the plate holder, which is used to hold the chisel, is in a line parallel to the long axis of the femoral shaft during insertion of the chisel (Fig. 6). This is important because, if it is not done, the plate will not be in line with the femoral shaft after insertion of the blade and the osteosynthesis may fail. Care must be taken to avoid chisel penetration of the anterior articular surface of the femoral condyle.
This procedure is indicated for patients with a painful deformity of the knee associated with a valgus tibiofemoral angle of ≥12° and narrowing of the lateral joint space. Associated patellofemoral arthritis of the knee is not a contraindication for this procedure. Patients who were selected for this procedure in our series had osteoarthritis of the knee in most instances, while some had posttraumatic arthritis. No patient had rheumatoid arthritis. Other, less common, indications are valgus deformity of the knee secondary to rickets, renal osteodystrophy, or neuromuscular diseases.
Contraindications include severe arthritis of the medial compartment of the knee, severe tricompartmental osteoarthritis, inflammatory arthritis, tibiofemoral subluxation, and patients who have a severe chronic illness or dementia or who are uncooperative. Relative contraindications are an age of more than sixty-five years or a history of septic arthritis of the knee. There is no contraindication to this procedure if the patient has an excessive valgus deformity of the knee. Two knees in our series had a tibiofemoral angulation of 27° of valgus.
Careful selection of patients is the key to the success of this procedure. Intraoperative assessment of the severity of the osteoarthritis of the medial compartment of the knee is mandatory. If there is subchondral bone exposure of the medial compartment, this procedure should be abandoned.
The second guidewire must be parallel to the transcondylar guidewire, and it should be verified by intraoperative radiographs. A slightly valgus position of the second guidewire is better than a varus position. When we insert the 90° blade-plate and apply compression on the medial femoral cortex to close the osteotomy medially, there is a tendency for the blade to lose its position and for the osteotomy to go into varus if the femoral bone is osteopenic. An anterior guidewire through the patellofemoral articulation is necessary for reference during insertion of the chisel into the femoral condyle.
Care must be taken when inserting the chisel through the medial cortex of the femoral condyle; the blade of the chisel should be parallel to the second guidewire, and the long arm of the plate holder should be parallel to the axis of the femoral shaft. If this is not done, when the 90° blade-plate is inserted and the osteotomy is closed, the tibiofemoral angulation will not be in the desired 0° and the plate will not line up with the medial cortex of the femoral shaft.
The 90° blade-plate used for osteosynthesis of the osteotomy in this report is bent from an AO 95° blade-plate (Synthes), which is designed for fixation of a supracondylar fracture of the femur and is applied laterally. There is no offset of the blade-plate. Therefore, when the blade-plate is inserted medially, there must be a gap between the plate and the medial femoral cortex. To avoid excessive medial displacement of the proximal fragment, which might cause technical difficulties if a total knee replacement is to be done, compression or crush of the medial cortex of the distal fragment is intended by inserting the blade-plate more laterally (Fig. 13, B). Because of the deep insertion of the blade into the femoral condyle, it is better to select a shorter blade length than a longer device. No patient in our series has reported discomfort of the knee because of softtissue impingement by the prominent blade medially.
The derotation screw, which transfixes from the medial cortex of the proximal fragment obliquely to the lateral cortex of the distal fragment after osteosynthesis, is important in this technique. It is placed after dynamic compression of the osteotomy is done. This special technique has not been previously mentioned in the method of distal femoral varus osteotomy. The derotation screw can be inserted through the first or second hole proximal to the bend in the blade-plate or through the femoral cortex outside the plate (Fig. 14). The screw provides rotational stability for the early rehabilitation program.
In the original study, some patients with osteopenia lost the position of the blade and had a varus deformity after the osteotomy was closed medially. We had to take out the blade-plate, bend it to >90°, reinsert it, and check the alignment radiographically. Currently, a wedge of cortical bone, which is removed from the osteotomy site, is placed in the slot between the blade and the medial femoral condyle when the femoral bone is osteopenic. With use of this technique, no knees, to date, have required rebending of the blade-plate to adjust for the loss of correction during insertion of the blade-plate.
Methylene blue is then used to mark the first line of the femoral osteotomy along the line of the third guidewire, which is just proximal to the anterior articular surface of the femoral condyle. The second line of the femoral osteotomy is 5 to 8 mm proximal to the first line medially and continues laterally to intersect the first line on the lateral femoral cortex (Fig. 6). The femoral osteotomy is done along the two lines with preservation of the lateral femoral cortex; the medially based wedge of bone, which is 5 to 8 mm wide, is removed (Fig. 7). The lateral femoral cortex is then perforated at three points with use of a 4.5-mm drill-bit (Fig. 8). The 95° AO dynamic-compression blade-plate (Synthes, Oberdorf, Switzerland) is bent to 90° with a bender (Fig. 9). The length of the blade (50 or 60 mm) is selected, depending on the size of the femoral condyle as determined by preoperative templating. The selected blade-plate is inserted through the created slot in the medial femoral condyle. The medial cortex of the femoral condyle above the blade insertion site is crushed by the blade-plate to allow direct contact of the plate with the medial cortex of the femoral shaft without translating the shaft medially. With this technique, the proximal fragment, which is smaller in diameter, is easily impacted into the wider distal fragment. If impaction does not occur, the spike of medial cortex or excessive cortices of the proximal fragment are trimmed. The screws are inserted according to the principle of the dynamic compression plate5 except for the hole, which is located just proximal to the bend in the blade-plate. Here a cortical screw is inserted obliquely from the medial cortex of the proximal fragment to the lateral cortex of the distal fragment to provide additional stability at the site of the osteotomy (Figs. 10, 11, and 12). Because the plate is in contact with the medial femoral cortex, the axis of the distal aspect of the femur is 90° to the knee-joint line. The tibiofemoral angle should be approximately 0° after the osteotomy and the osteosynthesis with the 90° blade-plate; this is the desired position as described by McDermott et al.3 (Fig. 13).
Drilling of the denuded subchondral bone of the lateral compartment and patellofemoral joint, if present, is performed following the technique advocated by Pridie6. A lateral retinacular release is performed if there is severe patellofemoral arthritis associated with lateral subluxation of the patella.
Postoperatively, the affected limb is immobilized in a hinged knee brace. Forty-eight hours after the operation, the patient is instructed to use a continuouspassive-motion machine and to start walking with use of crutches and without weight-bearing. The patient is discharged when a 90° arc of active knee flexion is achieved and the operative wound is dry and clean. Partial weight-bearing of the affected limb is commenced when initial healing of the osteotomy site has been confirmed radiographically, usually after six weeks. Full weight-bearing is permitted only after three months and after radiographs show good healing of the osteotomy site.
The original scientific article in which the surgical technique was presented was published in JBJS Vol. 87-A, pp. 127-133, January 2005
The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Department of Orthopaedic Surgery, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China
- Copyright © 2006 by The Journal of Bone and Joint Surgery, Incorporated