Total hip prosthesis with screw rings. Results over 2 years of a series of 198 consecutive prostheses

: 198 screw rings implanted before january 1988, 156 were combined with cementless femoral components, and 42 with cemented femoral components (hybrids). Fifteen cases, which were initially included in the first group, became hybrid at 2 years due to replacement of the femoral component by a cemented stem. 21 screw rings (11 per cent) were revised, and replaced with cemented polyethylene sockets. In 7 cases, acetabular reconstruction was required. Revision was justified by roentgenographic instability in only 6 cases. Four other implants were revised due to persistent postoperative pain, although there was no measurable migration on successive roentgenograms. In the 10 remaining cases, revision was initially justified by the femoral component: screw rings were found to be mobile and were replaced in the same time. Symptoms related to screw rings were easier to identify in hybrid arthroplasties, in which cemented femoral components were usually asymptomatic. Fourty five cases had a complete 2 year follow-up (34 were initially hybrid, 11 became hybrid due to revision of the femoral component). Twenty four patients complained of durable postoperative groin pain. In 18 of these cases, pain completely disappeared within the 18 first months. At 2 years, 28 patients had no pain. In 149 cases with complete 2 year roentgenographic follow-up, 126 implants had never migrated, 6 migrated early but stabilized within the first postoperative year, and 17 showed progressive migration over the first two postoperative years, in which 7 were finally revised. These results are inferior to those reported with cement. Some failures were explained by poor implantation techniques or by wrong indications. Other failures remained unexplained, thus justifying a reduction of their use in our institution.