Purpose: To assess the clinical and radiological performance of the Ultima THR.

Material-Methods: Between January 1991 and July 1994, 147 consecutive patients (154 hips) underwent a primary THR using an all-polyethylene cemented cup and the Ultima Ti alloy smooth, collarless, double tapered, straight stem. 65% were females and primary diagnosis was OA or RA in the majority. The average age at operation was 66.4 years. At average follow-up of 76 months, 34 patients (35 hips) were dead and 5 were lost. Patients were annually assessed clinically (HSS) and radiologically. Radiographs were digitized and migration analysis and cup wear was performed using the EBRA method.

Results: There were 9 aseptic failures (5 stems, 1 cup and 3 both components). Cup migration analysis was possible in 106 cases. Migration was detected in 62 of them (18 proximal, 15 medial, and 29 combined). Proximal migration ranged from 0.8 mm-4.0 mm and medial migration from 1.0 mm–3.5 mm. The average cumulative linear cup wear was 0.2 mm. Stem migration analysis was possible in 114 cases. At 2 years, 35 stems subsided less than 1.5 mm. Migration of more than 1.5 mm was observed in 16 stems. Early subsidence of more than 1.5 mm was highly predictive for later revision.

Conclusions: Ti-stems have been criticised for high failure rate but the exact mechanism of loosening is multifactorial. Our revision rate and the low incidence of focal osteolysis, even in the presence of a small degree of stem subsidence, indicate that a smooth double tapered Ti-alloy cemented stem may offer a durable long-term solution.