Instability of total hip prostheses at rotational stress: A roentgen stereophotogrammetric study

Abstract

Roentgen stereophotogrammetric analysis (RSA) has been carried out on 24 total hip prostheses (24 patients), which were all painful at weight-bearing. The examinations were made with the hip at distraction, compression, external and internal rotation. One acetabular component showed instability only at distraction-compression and one showed instability only at rotation. Four femoral components showed instability at distraction-compression and at rotation, six only at rotation, but none showed instability only at distraction-compression. Thus rotational provocation demonstrated instability in all unstable femoral components; rotational stress must be of importance in mechanical loosening of the femoral component.