Total knee arthroplasty after varus osteotomy of the distal part of the femur.

BACKGROUND

There is little information in the literature regarding the outcome of total knee arthroplasty following distal femoral varus osteotomy. The purpose of the present study was to evaluate the intermediate-term results of total knee arthroplasty following distal femoral varus osteotomy.

METHODS

The study group consisted of nine consecutive patients (eleven knees) who had had a total knee arthroplasty following varus osteotomy of the distal part of the femur. The average age of the patients was forty-four years (range, fifteen to seventy years) at the time of the arthroplasty. The results were evaluated with use of the Knee Society score preoperatively and after a mean duration of follow-up of 5.1 years. Radiographs made preoperatively and at the time of follow-up were evaluated for alignment in the coronal plane.

RESULTS

The mean Knee Society knee score was 35 points before the arthroplasty and 84 points after the arthroplasty. The mean Knee Society function score was 49 points before the arthroplasty and 68 points after the arthroplasty. The mean interval between the femoral osteotomy and the total knee replacement was fourteen years (range, two to thirty-two years). A constrained prosthesis was required in five of the eleven knees. Two knees had an excellent result, five had a good result, and four had a fair result. The mean arc of motion improved from 81.8 degrees to 105.9 degrees. The mean radiographic alignment was 3.6 degrees of valgus (range, 7 degrees of varus to 18 degrees of valgus) before the arthroplasty and 3.3 degrees of valgus (range, 1 degrees of valgus to 6 degrees of valgus) at the time of the latest follow-up. There were no infections or wound complications.

CONCLUSION

Total knee arthroplasty following distal femoral varus osteotomy decreases pain and improves knee function, but the procedure is technically demanding and is associated with inferior results when compared with those of primary arthroplasty performed in a patient without a prior femoral osteotomy. In the present series, the use of an intramedullary femoral alignment guide increased the tendency to place the femoral component in relative varus angulation (that is, in <5 degrees of valgus). We recommend checking the alignment of the femoral component with an extramedullary guide in knees that have had a previous distal femoral varus osteotomy.