The medial Oxford unicompartmental knee arthroplasty uses a fully congruent mobile bearing, varying in thickness from 3.5-11.5 mm. Impressive clinical and survival results have been achieved by the designing surgeon, but can they be reproduced by an independent center and does the use of bearings less than 6 mm thick reduce the implant's survival? Between November 1983 and May 2000, 439 medial Oxford prostheses were implanted by three surgeons in Skovde, Sweden. One hundred fourteen knees (89 patients) were reviewed clinically at a minimum of 10 years postoperatively, using the Hospital for Special Surgery knee score. Ninety-one percent of the knees had good or excellent results, with no poor results, and 82% were reported as pain free. The 15-year survival rate for the entire cohort was 93%, and for the 432 knees (344 patients) that met the current indications for using the device, the survival rate was 94%. The 10-year survival rate for bearings less than 6 mm thick was 95%, compared with 94% with bearings greater than 6 mm. The results show that an independent center can achieve excellent long-term clinical and survival results in patients implanted with the Oxford prosthesis. Survival of the implant was not reduced by the use of thin polyethylene bearings.
Level of evidence: Therapeutic study, Level IV (case series--no, or historical, control group). See the Guidelines for Authors for a complete description of levels of evidence.