PROSPECTIVE STUDY WITH 10 YEARS FOLLOW-UP OF THE AURA STEM-ALIZÉ CUP HIP BEARING

Abstract

Purpose: We report a retrospective series of 98 consecutive total hip prostheses implanted without cement: the Aura stem and the Alizé cup coated with hydroxyapatite; reviewed at mean 9.6 years. The purpose of this analysis was to examine implant stability and wear.

Material and methods: Total hip prostheses implanted in 98 patients from January 1991 to January 1992 were reviewed: 60 women and 38 men, operated on by the same surgeon using an Alizé cup and an Aura stem without cement. Mean age at implantation was 66.5 years (30–85). Mean follow-up was 9.67 years. We retained 56 patients for this analysis (17 patients had died, 13 were lost to follow-up, 9 could not be followed, and 3 stem removals (3.1%)). This was the first procedure in all patients. Clinical outcome was assessed with the Postel-Merle-d’Aubigné (PMA) score and with a self-administered questionnaire. Radiologically, we assessed stability (tilt, implant displacement) and implant wear using MetrOs software data processing of digitalized radiograms. We also searched for qualitative radiographic signs of bone reaction to the implant.

Results: The overall PMA score improved from 11.96 preoperatively to 17.42 at the 5-year assessment and then fell to 15.67 at last follow-up. At five years 94% of the patients (92 hips) were satisfied and 98.3% (56 hips) were reviewed at 10 years. There were two fractures of the ceramic head after direct fall on the greater trochanter (requiring replacement of the femoral implant, the head and the polyethylene insert). There was one infra-prosthetic fracture which required stem replacement. Analysis of the radiograms did not demonstrate any abnormal ossification or lucency. MetrOs was used on 52 files: mean wear was 0.77 mm at 10 years (0.16–2.24 mm): wear and impaction (0.789 mm) of the stem were significantly correlated at 10 years while stem tilt was negligible.

Discussion: This radioclinical analysis demonstrated that these hydroxyapatite coated implants are stable over time. The clinical results are satisfactory with a small regression of the PMA score related to patient ageing. The radiographic measurements obtained with a precise rigorous tool were very encouraging. We compared our results with those of series using comparable implants.