A 77-year-old woman underwent primary lateral unicompartmental knee arthroplasty with cemented components for severe osteoarthritis of the lateral compartment of the right knee with a valgus approximately 5°. She had diabetes mellitus and hypothyroidism, but she had not undergone a previous surgical procedure on the right knee. The lateral unicompartmental knee replacement implanted was a SCORE implant (Amplitude) cemented with a size 1 femoral component, a size 4 tibial component, and a 12-mm fixed polyethylene bearing. A lateral approach and navigation were used. The postoperative radiographs are shown in Figure 1. The patient had no postoperative complications, but she still experienced pain after the surgical procedure.
At 11 years after the arthroplasty, the patient experienced a locking event of the right knee. The knee was locked at approximately 40° of flexion for a half-day. The patient heard a great clicking noise when she tried to walk on the right leg. After that, she could walk again but with lateral knee pain. She reported that she had not had trauma or an inciting event. She presented to our clinic 45 days after this episode. On physical examination, the knee was dry, the extension was complete, and the flexion was at 140°. The main symptom was lateral knee pain. Radiographs (Fig. 2) showed that the femoral component was pushed on the lateral condyle. This impaction was responsible for great valgus.
What is the diagnosis?
Dislocation of the tibial polyethylene
Extrusion of the tibial component into anterior soft tissue
Extrusion of the tibial component into posterior soft tissue
Aseptic loosening related to polyethylene debris
180° rotation of the femoral component
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