ALUMINA-ON-ALUMINA TOTAL HIP ARTHROPLASTY. A MULTICENTER PROSPECTIVE STUDY

Abstract

Introduction. Alternative bearing surfaces to polyethylene have been introduced to avoid the appearance of osteolysis in THR. The aim of this study has been to perform prospective analysis of the data from a multi-center clinical trial for assessing the incidence of early alumina-specific-complications.

Material and Methods. We analysed 310 Cerafit cups associated with a Multicone-HA stem using alumina-on-alumina bearings implanted in four institutions from 1999 to 2003, with a mean follow-up of 4.7 years. Patients’ mean age was 52.8+13.4 years. Linear femoral head penetration was analysed using a software package.

Results. There were 4 revisions: 2 revisions due to dislocations resulting poor surgical technique (1 cup and 1 stem) and 2 revisions after a trauma (1cup and 1 stem). There was 1 alumina liner fracture 36 months after implant in a hip with a horizontal acetabular angle (35°) and a thin alumina liner (size 50/32). The other cases showed good clinical and radiographic results at the end of follow-up. The radiographic difference between the femoral head and cup centres at 6 weeks postsurgery was 2.48+0.60 mm, without changes in the course of the follow-up. The mean linear femoral head penetration was unreliable (0.00186+0.0032 mm/year) because it was below the mean error for the measurement system.

Conclusions. These data demonstrate that Cerafit Alumina-on-Alumina prostheses show excellent results after 5 years. Liner fractures are uncommon. Despite the blurred alumina images, the digitized method, although not totally accurate and used only for a general estimate, allows us to measure the approximate distance between the centre of the cup and the centre of the femoral head. Changes in linear femoral head penetration were not seen in any hip. Continued follow-up should determine if reduction in wear among the alumina-on alumina bearings results in less osteolysis.