Long-term outcomes of total hip arthroplasty with modular cementless stems for fused hips: a matched comparison study...

To report the long-term outcomes of conversion total hip arthroplasty (THA) for fused hips compared with primary THA for osteoarthritis.

We reviewed patients who underwent conversion THA for fused hips using cementless modular stems between January 1995 and December 2006 at a single institution. From the cohort of 46 patients with fused hips, one-to-one propensity score matching based on age, sex, and body mass index identified 37 matched pairs with osteoarthritis. The mean age and follow-up were 49.5 (range: 19-71) and 18.2 (range: 10-28) years, respectively. Clinical outcomes were assessed using the HHS and UCLA activity score. Implant survivorship was estimated with revision for any reason as the endpoint.

The mean HHS and UCLA activity score improved from 47.6 to 87.8 (P < 0.001) and 3.6 to 6.7 (P < 0.001), respectively. The final scores did not differ between the groups. A positive Trendelenburg sign was more frequent in the fused-hip group (29.7% vs. 8.1%, P = 0.018). In the fused-hip group, periprosthetic infection and periprosthetic fracture occurred in two hips each (5.4%). Sciatic nerve palsy occurred in one hip (2.7%) in the osteoarthritis group. The implant survivorship at 20 years was 79.0% in the fused-hip and 74.1% in the osteoarthritis group (log-rank, P = 0.548).

After a mean follow-up of 18 years, conversion THA for fused hips using cementless modular stems demonstrated favourable long-term outcomes comparable to those of primary THA for osteoarthritis, supporting conversion THA as a reliable treatment option.