Computer-assisted navigation decreases the change in the tibial posterior slope angle after closed-wedge high tibial osteotomy

The purpose of the present study was to compare the change in tibial posterior slope angle (PSA) between patients treated via computer-assisted and conventional closed-wedge high tibial osteotomy (CWHTO). It was hypothesized that a decrease in the PSA would be less in the computer-assisted group than in the conventional group. Data on a total of 75 computer-assisted CWHTOs (60 patients) and 75 conventional CWHTOs (49 patients) were retrospectively compared using matched pair analysis. The pre- and postoperative mechanical axis (MA) and the PSA were radiographically evaluated. The parallel angle was defined as the angle between the joint line and the osteotomy surface. The data were compared between the two groups. The postoperative radiographic MA averaged 1.3A degrees +/- 2.6A degrees valgus in the computer-assisted group and 0.3A degrees +/- 3.1A degrees varus in the conventional group. The change in PSA averaged -0.8A degrees +/- 0.9A degrees in the computer-assisted group and -4.0A degrees +/- 2.2A degrees in the conventional group. The parallel angle averaged 0.2A degrees +/- 3.0A degrees in the computer-assisted group and 6.2A degrees +/- 5.3A degrees in the conventional group. Computer-assisted CWHTO using four guide pins could avoid inadvertent change in the PSA. The navigation can be used in anticipation of decreasing the risk of change in the PSA in CWHTO, especially in patients whose preoperative PSA is small. The special attention should be paid to locate the hinge axis acutely and to make the parallel proximal and distal osteotomy surfaces during CWHTO. III.