Standing versus supine radiographs to evaluate femoral head penetration in the polyethylene liner after total hip arthroplasty.

Abstract

The linear penetration rates for ceramic femoral heads on conventional and highly cross-linked polyethylene were measured and compared with radiographs taken in the standing and supine position taken three weeks postoperatively and at final follow-up. Seventy-five patients (83 hips) with conventional polyethylene (group-1) and two hundred and seventy five patients (300 hips) with highly cross-linked polyethylene (group-2) were studied. Follow-up periods were 14.5years in group-1 and 8.6years in group-2. The average penetration rates in group-1 were 0.17mm/year in supine position and 0.18mm/year in standing position (P<0.05). On the other hand, the rates in group-2 were 0.03mm/year and 0.04mm/year respectively (P<0.05). Although there were statistical differences between groups, 0.01mm differences are probably not clinically relevant.