Abstract
Postoperative pain of unknown origin can be a reason for revision of unicompartmental knee arthroplasty (UKA). We report a case of persistent knee pain after mobile UKA that was resolved by revision to fixed UKA. The patient, an 85-year-old woman, had undergone mobile UKA because of medial-type osteoarthritis in her left knee seven years previously. However, even after surgery, anterior knee pain had persisted despite of conservative treatment. Although neither loosening of the implant nor degenerative change in the unresurfaced area had been observed, revision arthroplasty was undertaken at the patientʼs request. During the revision operation, we found severe impingement of the mobile-bearing insert with fibrous tissue that had been produced in the anterior uncovered area of the medial femoral condyle, and carefully removed the mobile UKA implants, followed by successful revision to fixed UKA. Soon after the revision surgery, the patientʼs pain disappeared, and she recovered well without loss of range of knee motion. It should be noted that mobile UKA may cause anterior bearing impingement due to loss of implant coverage of the femoral condyle, especially when a single peg-type femoral component is placed in a flexion position, and that the conversion of mobile to fixed UKA can be a useful and less invasive therapeutic option for the treatment of anterior mobile bearing impingement after mobile UKA.
