EARLY FAILURE OF CHARNLEY ELITE: VERIFICATION OF RSA PREDICTIONS?

Abstract

Introduction: The Charnley Elite femoral component was first introduced in 1992 as a new design variant of the original Charnley femoral component (De Puy, Leeds, UK) with modified neck and stem geometry. The original component had undergone few changes in nearly forty years and has excellent long-term results.

Early migration of the new stem design was determined by Roentgen Stereophotogrammetric Analysis (RSA). Rapid early migration of a component relative to the bone, measured by RSA, is predictive of subsequent aseptic loosening for a number of femoral stems. As there was rapid early migration and rotation of the Charnley Elite stem, we predicted that the long-term results would be poor. An outcome assessment is required as stems of this type are still being implanted.

Materials and method: One hundred Charnley Elite stems, implanted in our centre between 1994 and 1997 were included in a prospective, cross-sectional follow-up study. Outcome measures include validated clinical scores (Charnley hip score, Harris hip score and Oxford hip score) and radiological scores (Gruen classification) as well as revision rates over the past 10 years.

Results: The preliminary analysis results are given. The mean time to follow-up was 8.28 years. 20 patients have died due to causes unrelated to their operations. 10 patients had stem revisions: 9 for aseptic loosening and 1 for a peri-prosthetic fracture. This indicates a significant 10% failure rate of the prosthesis in less than 10 years.

Preliminary clinical scores in the patients who had not undergone any subsequent surgery were adequate (Oxford Hip Score mean average of 23.9).

Thirteen percent of radiographs analysed had evidence of loosening, giving an overall loosening rate of 14% at 8 years.

Discussion and conclusion: The clinical follow-up supports the RSA predictions of early failure of the Charnley Elite femoral stem.