Loosening 5 years after total hip replacement--a radiological study of the McKee-Farrar and Charnley prostheses.

In a prospective study, 138 patients who underwent total hip replacement by the McKee-Farrar or the Charnley technique were monitored yearly for 5 years by X-ray. Six variables were measured on anteroposterior and lateral projections to describe the position of the prosthesis. Lateral opening greater than 50 degrees and cover of the acetabular cup less than 1.5 cm correlated with an increased cup-loosening rate: 71% (98 of 138) were loose at the 5-year follow-up. However, only about one-third of all cup loosenings in the present series can be explained by nonoptimal position of the prosthesis. No significant difference emerged concerning loosening rate between the McKee-Farrar and the Charnley prostheses.