DISLOCATION, A MAJOR CAUSE OF REVISION TOTAL HIP ARTHROPLASTY: STATISTICAL ANALYSIS OF FACTORS FAVOURING FAILURE AMONG 3000 HIPS COLLECTED OVER FIVE YEARS

Abstract

Purpose: Instability is a major cause of revision total hip arthroplasty (rTHA). It was the third leading cause (5%) after aseptic loosening (75.7%), and infection (7.2%) in the Swedish registry for 2000. The rate of dislocation is however variable depending on the reported series. We conducted a statistical analysis of nearly 3000 files of rTHA to study factors favouring failure.

Material and methods: AVIO, a watch association for orthopaedic implants, was created in 1994 to evaluate factors favouring failure of THA in France, and to furnish statistical data on prosthesis revision. About one hundred orthopaedic surgeons throughout France completed an information card for each revision for a five year period (September 1994 to September 1999). A total of 2926 card were analysed. Patient data (gender, side, number of revisions, age at implantation, age at removal, reason for THA, reason for revision, duration of THA) were cross analysed. The statistical analysis was conducted with chi-square tests and non-parametric tests. Significant results were compared with data in the literature. We present here the results concerning dislocation as the reason for revision.

Results: The rTHA for dislocation accounted for 9.2% of the revisions. Dislocation was the primary reason for revision in patients with repeated revisions and was also the main reason for revision in patients aged over 70 years (20.6%). In this group of older patients, 72.8% of the prostheses were implanted for degenerative disease.

Discussion: The original finding in this study, not clearly reported in the literature, is that dislocation is the primary cause of revision after 70 years, coming before aseptic acetabular loosening. Although mentioned by Charnley in 1979, very few studies (Newington in 1990, Edelund in 1992) have studied the relationship between dislocation and age.

Conclusion: Patient-related factors play an important role in the stability of THA. After 70 years, dislocation becomes the primary reason for revision and should be taken into consideration in our ageing population. This study has led us to modify our therapeutic strategy in patients aged over 70 years.