Influence of minimally invasive surgery on implant positioning and the functional outcome for medial unicompartmental knee arthroplasty.

We describe postoperative functional outcome and accuracy of implant position in 38 cases after unicompartmental knee arthroplasty with the Oxford knee prosthesis with a standard open approach compared with 30 cases with a minimally invasive approach. Patients with the minimally invasive approach had significantly better functional results, with an average Hospital for Special Surgery scores of 92 (range, 81-98) compared with 78 (range, 24-99). Range of motion 1 year postoperatively was better in the minimally invasive group (113 degrees vs 107 degrees ), but the results were not statistically significant. The number of patients with extension lag was significantly higher after the open approach. The minimal invasive approach had no negative effect on positioning of the prosthesis. In our opinion, minimally invasive implantation is the method of choice for the treatment of anteromedial osteoarthritis by unicompartmental knee arthroplasty.