HYYDROXYAPATITE COATED FEMORAL COMPONENTS IN TOTAL KNEE ARTHROPLASTY; MEDIUM TERM RESULTS

Abstract

Purpose: To study the clinical and radiological results and survival of hydroxyapatite coated femoral components in total knee arthroplasty at a mean follow-up of eight years.

Materials and Methods: Between 1991and 1992 36 consecutive knees with disabling arthritis were replaced with Freeman Samuelson Total knee prostheses with hydroxyapatite coated femoral components. These patients were prospectively followed up according to a standardised protocol for a mean period of 8 years. (Range 7–9 years). Clinical and radiological examination was done at each follow up. 1 knee was lost to follow up at 7 years. 4 patients (6 knees) died at 4 years (1), 7 years(2), 8 years (2), 9 years (l). None had been revised at the time of death. The radiographs were studied for signs of loosening and presence of lucencies.

Survival analysis was done using Kaplan and Meir’s method and with revision as the criterion for failure.

Results: There were 15 males and 14 females. The average age at operation was 63 years. Two knees (1 patient) were revised due to aseptic loosening, in both, of the femoral component. The alignment of the component in these was poor with an oblique joint line. The tibial component of one other knee was revised due to osteolysis in the medial tibial condyle. In the remaining knees there was no radiological evidence of loosening.

The survival of the femoral component at a mean follow-up of 7 years was 94% when 31.5 knees were at risk, with revision for femoral aseptic loosening as the end point.

91 percent of patients were pain free and 96% had an uninterrupted walking distance more than 10 minutes. The average alignment was 7.20 valgus (range 00–100 valgus).

Conclusion: The results of total knee arthroplasty with hydroxyapatite coated femoral components are encouraging in the medium term although not as good as those with cemented fixation.