Implant Overhang after Unicompartmental Knee Arthroplasty: Oxford Prosthesis versus Miller-Galante II Prosthesis

PURPOSE: The purpose of the present study is to compare the prevalence of implant overhang between the Oxford and the Miller-Galante II (M-G II) unicompartmental knee arthroplasty (UKA) prostheses and determine whether overhang is associated with postoperative clinical results. MATERIALS AND METHODS: We retrospectively reviewed one hundred and seven UKAs which consisted of 37 Oxford UKAs and 70 M-G II. Overhang was considered present if ≥3 mm overhang was observed in any zone. The range of motion, the Knee Society scores and the Western Ontario and McMaster scores were compared after a mean follow-up duration of 48 months. RESULTS: Thirty three of 107 knees (30.8%) had overhang in at least one zone of the femoral or tibial component. In the tibial side, there were no significant differences between the groups in component overhang in each zone. In the femoral side, the Oxford UKA group showed a significantly higher prevalence of the posterior overhang of the femoral component (19/37, 51.4%) than did the M-G II UKA group (3/70, 4.3%; p<0.001). However, no significant differences in clinical results were observed between the two groups. There were also no significant differences in clinical results between the overhang and the non-overhang groups. CONCLUSIONS: Posterior overhang of the femoral component was highly prevalent in Oxford UKA patients. However, posterior overhang of the femoral component had no significant relationship with postoperative clinical results in both Oxford and M-G II UKAs at a mean of 48 months follow-up.