Mechanical factors in loosening of Christiansen and Charnley arthroplasties.

A series of 96 Christiansen and 23 Charnley hip arthroplasties, mainly for osteoarthrosis, were followed for an average of 40 (15-93) months. Radiolucent zones at the cement bone interface and resorption of the calcar were more frequent in the Christiansen than in the Charnley hips. Medial and axial migration, and cement fracture often occurred concurrently, with a total frequency of 27/96 in the Christiansen and 4/23 in the Charnley subseries. Wide radiolucent zones in the acetabular cement bone interface were more frequent in the Christiansen hips. Six acetabular protrusions were observed in the Christiansen hips against none in the Charnley hips. The average Harris' hip scores were significantly higher for the Charnley than for the Christiansen hips. Reoperation for loosening was performed in two Charnley hips and 19 Christiansen hips.