A computer simulation study for preserving the tibial posterior slope in open-wedge high tibial osteotomy.

To measure the medial opening gap and examine a technique for preserving the tibial posterior slope (TPS) in open-wedge high tibial osteotomy (OWHTO) using computer-simulated three-dimensional (3D) surgery. This study included 24 symptomatic knees from 20 patients (7 men and 13 women; mean age, 67.9 years; range 54-89 years). Digital imaging and communications from computed tomography examination were applied to a 3D picture software program, and several anatomical landmarks were registered. Then, computer simulation of OWHTO as a virtual surgery was performed: the correction angle was decided to make the femorotibial angle 170°, and the TPS did not differ between pre- and postplanification. The distance between the proximal and distal cortices of the medial tibia was measured at three points, which were the anterior (AD), posterior (PD), and longest (LD) distance sites in the sagittal plane, using the 3D view, and the ratios of AD/PD and AD/LD were measured. The anteromedial opening gap was compared to the posteromedial gap and the longest distance gap at the osteotomy site. Spearman's rank correlation coefficient test was used in statistical analysis. Mean AD/PD was 0.740 ± 0.051 (range 0.651-0.850), and mean AD/LD was 0.652 ± 0.040 (range 0.571-0.768). The correction angle was not associated with the values of both AD/PD and AD/LD. Difference in AD/PD and AD/LD between each patient was regarded as a significant variation. Therefore, preoperative planification with 3D computer simulation to measure AD/PD and AD/LD may be helpful to avoid a significant increase in TPS.