Mid-term results and migration behaviour of a ti-alloy cemented stem.

Between 1991 and 1994, 147 patients (154 hips) underwent a primary cemented total hip replacement using the Ultima ti-alloy, collarless, double-tapered stem and a UHMWPE cup. The average age at operation was 66.4 years. Ninety-one patients (97 hips) were available for review with an average follow-up of 76 months. The Harris hip score had improved from pre-operative average of 43.1 (12.5-65.0) to the latest score of 88.9 (67.5-100). There were 11 revisions in total, eight of which were for aseptic stem loosening. The results of Kaplan-Meier survival analysis, based on stem revision for aseptic loosening as an end-point, was 92% at 8 years. Early stem migration analysis at 2 years was possible in 114 cases using digitised radiographs analysed by the EBRA method. Sixty-three stems had not migrated and 35 migrated less than 2 mm with only one of these ending in failure. Sixteen stems showed early migration of more than 2 mm and five of these failed. Early stem migration is predictive of stem failure. Osteolytic lesions occurred in 12 femurs and four of these stems failed.