Fracture of the Anterior Locking Flange of a Total Knee Arthroplasty Polyethylene Liner Presenting with Pain following Knee Replacement

INTRODUCTION Fracture of the modern polyethylene insert of a total knee arthroplasty is rare. We describe the first case of a fractured anterior locking flange of the commonly used Depuy Press-fit Condylar (PFC) Sigma prosthesis. CASE REPORT The 80 year old Caucasian gentleman presented 8 years following previously uncomplicated and successful primary total knee replacement with pain, swelling and symptoms of instability of the knee. He was able to sublux his knee posteriorly using his hamstrings. Dissociation of the liner was evident on radiographs. He underwent revision of the polyethylene liner. It was evident during the revision that the anterior locking flange of the polyethylene liner had fractured allowing it to dissociate from the tibial tray. At 12 months following this revision he continues to do well and has similar range of movement and function to prior to the episode. This cause of the failure is not clear. CONCLUSION Surgeons should be aware of this rare complication when assessing a painful or unstable total knee replacement.