Nontraumatic Fracture of the Femoral Condylar Prosthesis in a Total Knee Arthroplasty Leading to Mechanical Failure

This paper reports a case of fatigue fracture of the femoral component in a cruciate-retaining cemented total knee arthroplasty (TKA). A 64-year-old man had undergone a primary TKA for osteoarthritis 10 years previously at another institution using the PFC-Sigma prosthesis. The patient recovered fully and was back to his regular activities. He presented with a history of sudden onset pain and locking of the left knee since the preceding three months. There was no history of trauma, and the patient was mobilizing with difficulty using crutches. Radiographs revealed fracture of the posterior condyle of the femoral prosthesis. Revision surgery was performed as an elective procedure revealing the broken prosthesis. The TC3RP-PFC revision prosthesis was used with a medial parapatellar approach. The patient recovered fully without any squeal. Mechanical failure of the knee arthroplasty prosthesis is rare, and nontraumatic fracture of the femoral metallic component has not been reported before. 1. Summary and Background Mechanical failure of prosthesis is a rare but recognised complication in arthroplasty surgery. There are reports of acute breakage of the tibial posts [1–7], tibial polyethylene inserts [8–10] in posterior cruciate substituting total knee arthroplasty, and fracture of metal tibial trays after kinematic total knee replacement [11–13]. We describe a case of nontraumatic fracture of the posterior condyle of the femoral component in a total knee arthroplasty, which to our knowledge is the first report of its kind. 2. Case Report In December 1999, a 64-year-old man underwent a cemented left total knee arthroplasty using a sigma PFC posterior cruciate retaining total knee prosthesis (DePuy Orthopaedics, Warsaw, IN, USA) for degenerative changes in relation to osteoarthritis using a medial parapatellar approach in a different centre. The patient recovered uneventfully and was doing well. In July 2009, the patient presented to us with a history of sudden onset pain and locking of the left knee since the preceding three months. There was no history of trauma and since was mobilising with difficulty using crutches. The patient weighed 89？kgs and had no other medical comorbidities. Clinical examination revealed a severe antalgic gait and a significant amount of rocking with metal on metal noise in 20 degrees flexion. Passive movements ranged from 0 to 90 degrees. At that moment, the knee was quiescent. AP and lateral radiographs (Figures 1, 2, and 3) of the left knee revealed a fracture of the posterior condyle of the femoral prosthesis with rotation and