EARLY EXPERIENCE WITH KNEE JOINT SPARING DISTAL FEMORAL REPLACEMENTS

Abstract

When managing malignant bone tumours in the distal femur with limb salvage, resection and reconstruction with a distal femoral replacement (DFR) conventionally entails prosthetic replacement of the knee joint. In younger patients it is desirable to try to preserve the knee joint. We now use a new Joint-Sparing distal femoral prosthesis in those cases where it is possible to resect the tumour and preserve the femoral condyles. Purpose of study: To look at our early results with knee joint preserving DFR’s. Methods: Between June 2001 and March 2004 the prosthesis was implanted in 8 patients (5 males and 3 females) aged between 8 and 24 years at the time of surgery. The diagnosis was osteosarcoma in 6 cases and chondrosarcoma in 2 cases. All patients were followed regularly and knee range of movement was recorded as well as any complications that occurred. Patients were functionally evaluated using the MSTS Scoring System. Results: Six of the patients had a mean follow-up of 20 months (range 8–33) and in this group 4 had good knee flexion with a mean flexion of 122° (110–130), 1 patient had fair flexion of 60° and 1 patient had poor flexion of 20°. The mean fixed flexion deformity in the 3 patients who had such a deformity was 10° (5–15). There were no intraoperative complications but the patient with poor flexion required an arthrolysis and because of the poor result is under consideration for conversion to a conventional DFR. Two patients had follow-up periods of 3 months or less and are still in their early rehabilitation period. One patient in this group developed sepsis that resolved after an open washout. Conclusions: Our early results with this prosthesis, in the patients with adequate follow-up, have been good in the majority but the two cases of fair and poor knee flexion are disappointing. This particular problem may relate to design and technical factors, which will be discussed in detail.