Failure of tibial polyethylene insert locking mechanism in posterior stabilized arthroplasty.

Tibial insert locking mechanisms are intended to limit interface motion and to prevent backside wear in contemporary modular knee designs. The author describes a case of failure of the polyethylene insert locking mechanism in one design of primary total knee arthroplasty. Loosening of the locking clip was observed within 6 weeks of the index operation without any trauma. The possible mechanism of disengagement is discussed. This rare cause for knee failure has to be recognized because it leads to early revision.