Preoperative and postoperative limb alignment after Oxford unicompartmental knee arthroplasty

From a series of 64 sequential Oxford (Biomet Orthopedics, Inc, Warsaw, Ind) phase 3 implants, two study groups were selected: 23 knees with unilateral surgery and a normal opposite side, and 21 knees with bilateral simultaneous surgery. Standing 3-foot radiographs were taken pre- and postoperatively to assess the femorotibial angle and the location of the mechanical axis of the limb in relation to the knee. Results in the unilateral group showed an average postoperative femorotibial angle of 4.5 degrees was compared to a 3.4 degrees angle for the normal side, (not significantly different; P = .09). Results for the bilateral group were an average postoperative femorotibial angle of 3.4 degrees for the right and 3.5 degrees for the left, (not significantly different; P = .7). The location of the mechanical axis was similar between the knees in both groups. The study concludes that the Oxford soft-tissue balancing technique restores alignment, which is on average similar to the opposite side, and therefore presumably normal for that knee. Restoration of normal alignment should not put excess stress onto the lateral compartment.