Failure mechanisms of polyester fiber anterior cruciate ligament implants: A human retrieval and laboratory study

It has been hypothesized that ACL implant failure is often caused by bone impingement in knee extension following malplacement of the tibial tunnel. This study examined polyethylene terephtalate fiber ACL implants retrieved from a clinical study, and, to confirm the hypothesis, also set up a laboratory study intended to duplicate the failure mechanism. SEM and TEM examination of 25 ruptured implants gave details of fiber failure morphology, with shearing into longitudinal fibrils, followed by rupture, when the fibrils burst apart. Cadaver joints were run in a knee simulator, with deliberately impinging ACL implants. SEM examination of implants abraded in the knee in vitro showed identical fiber damage patterns, thus confirming the impingement hypothesis.