Recurrent posterior dislocation following primary posterior-stabilized total knee arthroplasty

In our series of 136 patients with primary total knee arthroplasty using posterior-stabilized prosthesis, a female patient with Parkinson disease developed posterior dislocation of the knee 9 months after surgery. Eventually, the dislocation became recurrent, occurring several times a day. The patient made the reposition always by herself. Two months after the first dislocation, we performed the revision of the polyethylene tibial insert and found wearing of the tibial insert's cam as an hitherto unreported cause of the mechanical instability of the total knee prosthesis.