Impingement as a mechanism of dissociation of a metasul metal-on-metal liner.

This case report is of a patient with disassociation of the acetabular cup liner caused by impingement. The cup inclination (39 degrees) and anteversion (24 degrees) were good as measured by computer navigation. Impingement occurred because the head-neck ratio was 2.0, and the hip length and offset were short by one head length. Successful revision without intraoperative impingement was accomplished with one size head larger (32 mm; head-neck ratio, 2.3) and one size longer to correct hip length and offset.