Retrieval analysis of failed constrained acetabular liners.

Despite the large loads placed upon constrained acetabular liners, little is known of their mechanical performance. We analyzed retrieved liners to determine wear and other damage modes and assess associations between types and severity of damage and clinical, radiographic, and implant variables. Outer rim impingement frequency and severity were higher than that for the inner rim. The 20 degrees elevation was most frequently affected by impingement. Inner rim impingement was more frequent with small heads. Outer bearing surface wear scores were higher than inner bearing scores. Liners removed for infection or stem failure had similar damage compared with other groups, demonstrating the complex relationship of impingement and wear with clinical performance. No association was found between liner damage and clinical and radiographic variables.