300. OUTCOME OF FEMORAL OSTEOLYSIS ABOVE CEMENTED FEMORAL STEMS NOT REMOVED AFTER CHANGING THE ACETABULAR IMPLANT

Abstract

Purpose of the study: When the acetabular component is revised alone, if the femoral stem has not been loosened, the question becomes what should be done about the osteolysis of the femur: Change the femoral piece systematically and graft the osteolysis? Curettage and grafting of the osteolysis? Curettage alone? This study reports the outcome of superior femoral osteolysis with a calcar granuloma and no other procedure (no curettage) after replacing the cup.

Material and methods: This was a retrospective analysis of 54 acetabular revisions performed from 1988 to 1998. The cemented femoral piece was stable, with no lucent line and in position since the initial implantation. The reoperation consisted in cementing a new polyethylene cup (< 32 mm) with or without a graft. The femoral head was initially ceramic (alumina 29 and zircon 25) and was preserved in ten cases (alumina) and changed systematically for the zircon heads. New heads were implanted: 20 alumina (32mm) and 24 metal. Calcar osteolysis was measured in mm² on the x-rays before and after changing the acetabular piece and then regularly every year to last follow-up (10 to 20 years).

Results: Preoperatively, superior femoral osteolysis was 156 mm² (48–576m²) situated in Guren zone 1 and 7. At last follow-up, it was 135 mm² (38–616 mm²) with no femoral loosening, decreased in 34 cases, unchanged in 11 and increased in 9. Spontaneous decline in preoperative osteolysis was observed when the bearing was alumina-polyethylne and the preoperative osteolysis was less than 100 mm². Increased osteolysis (minor but undeniable) was observed with the couple was metal-polyethylene and when the preoperative osteolysis was > 300 mm².

Discussion: If the superior femoral osteolysis does not compromise the stability of the femoral implant when undertaking isolated revision of the acetabular component alone, it can be neglected. Changing the bearing stabilizes the progression of the osteolysis and does not appear to compromise the mid-term outcome (15 years) for the femoral piece. Spontaneous decline of the osteolysis can be observed if the initial osteolysis is less than 1 cm² and if the new bearing is alumina-polyethylene.