Analysis of 13 early failures of the mobile bearing Oxford phase III unicompartmental knee prosthesis

Abstract

The use of unicompartmental knee arthroplasty appears to be increasing despite a significant number of early revisions. This study looks at a consecutive series of such procedures. We retrospectively reviewed thirteen patients who had a revision of a unicompartmental knee replacement between January 2003 and March 2008 inclusively. During the study period, a total of 141 UKAs were performed in the reporting unit, of those 9 were revised to TKA. The indication for revision to TKA was determined from clinical records and radiographs. All patients who underwent revision were followed up using Oxford Knee Score. No preoperative Oxford Knee Scores were available. The study group consisted of six men and seven women. The preoperative diagnosis was osteoarthritis in all cases. The mean follow-up time was 16.4 ± 10.7 months (range: 2–36 months). The mean age of the patients at time of revision was 60.8 ± 9.7 years (range: 50–77 years). All patients had undergone medial UKA. The mean time interval between primary surgery and revision surgery was 21.5 ± 13.4 months (range: 5–48 months). The indications for revision included loosening of the tibial and/or femoral component (n = 7), progression of osteoarthritis to lateral compartment (n = 2), unexplained medial knee pain (n = 2) patellofemoral symptoms (n = 1), and insert dislocation (n = 1). The mean postoperative Oxford Knee Score at the latest follow-up evaluation was 14 ± 6.5 (range: 5–26). For the majority of patients, UKA provides reliable and reproducible results. However, UKA is a demanding procedure that needs special experience and includes a risk of early failure.