Dislodgment of polyethylene liners in first and second-generation Harris-Galante acetabular components - A report of eighteen cases

Background: Dislodgment of the polyethylene liner is an increasingly common complication following total hip arthroplasty. The purposes of this study are to present the results in a series of patients with this complication a nd to analyze the mode of failure. Methods: Between November 1995 and January 2001, eighteen patients who had had a total hip arthroplasty presented with dislodgment of the polyethylene liner from a Harris-Galante metal acetabular shell. The medical records, r adiographs, operative notes, and retrieved components were reviewed. In add ition, scanning electron microscopy was used to study the fractured surface s in a shell that had four broken tines. Results: The components had been in situ for an average of seven years (ran ge, three to eleven years). Seventeen components were second generation, an d one was first generation. Symptoms developed spontaneously in sixteen pat ients, during sexual intercourse in one, and following a fall on the hip in one. Radiographs showed eccentric positioning of the head in all of the hi ps and broken tines in six. All of the shells were well fixed. Treatment co nsisted of revision of the shell in four patients, exchange of the liner in four, cementation of a new liner into the shell in seven, and cementation of an all-polyethylene cup in three. The liners had severe damage of the ri m. Scanning-electron microscopy of the fractured surfaces of four tines rev ealed a fatigue pattern. Conclusions: We believe that, as the liner wears and becomes loose because of an inadequate locking mechanism, progressive micromotion occurs and the load increases on the polyethylene rim until it deforms and/or fractures. S ubsequently, nothing prevents the liner from rotating out of the shell. As this mechanism of failure appears to include fatigue failure of the locking tines and wear of the liner, this complication is likely to increase as th e components age in situ.