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°) and anteversion (24°) 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.