Dislocations after total hip arthroplasty

During the 10-year period ending in 1978, 10,500 conventional total hip arthroplasties were performed at the Mayo Clinic; dislocation developed after 331 (3.2%) of these procedures. Cross correlations of the data were performed using multivariate analysis. This analysis showed that previous surgery on the hip was the most significant of the factors predisposing to dislocation, the incidence doubling from 2.4% (in hips without previous surgery) to 4.8% (in hips with previous surgery) (p < 0.001). The dislocation rate was 2.3% after an anterolateral approach and 5.8% after a posterior approach (p < 0.01). The size of the head of the femoral component was not a strongly influential factor. The incidence of dislocation was 17.6% in the hips that had osteotomy and avulsion of the greater trochanter, compared with 2.8% in those in which the trochanteric osteotomy united (p < 0.001). Reoperation for instability of the hip was performed in a third of the patients, but in 31% of the patients whose hip was reoperated on the instability persisted after the revision.