A simple planning tool for tibial slope osteotomy-Osteotomy depth is a precise parameter to determine wedge height

To compare the planning precision of three wedge height planning methods relative to angular-based reference planning for infratubercle anterior closing wedge high tibial osteotomy (ACW-HTO).

Lateral knee radiographs of patients with posterior tibial slope (PTS) ≥ 13° were retrospectively reviewed. Infratubercle ACW-HTO was planned targeting a PTS of 5°. Angle-based planning served as the reference. Three methods were evaluated: wedge height calculated from osteotomy depth and correction angle (osteotomy depth method), a fixed ratio of 1.2 mm per degree of correction (ratio 1), and 1.67 mm per degree (ratio 2). Correction error was defined as the difference in wedge heights between each method. Planning precision was assessed using a ±1° correction error threshold. Intraclass correlation coefficient (ICC) was assessed.

Forty-six lateral knee radiographs of 46 patients (mean age 30 ± 11 years; 44% female) were included. Mean PTS was 15° ± 2° (range: 13-19°), requiring a mean correction of 10° ± 2° (range: 8-14°). Wedge heights differed significantly across planning methods (p < 0.001). Compared to the reference, ratio 1 underestimated wedge height by -1 ± 2 mm (range: -4 to 3 mm; p = 0.024) and ratio 2 overestimated by 4 ± 2 mm (range: 1-8 mm; p = 0.005). The osteotomy depth method achieved a correction error within ±1° in 83% of cases (38/46), ratio 1 (50%, 23/46; p = 0.048) and ratio 2 (9%, 6/46; p < 0.001). Interrater ICC was 0.85 (95% confidence interval [CI]: 0.73-0.92) for PTS, 0.91 (95% CI: 0.83-0.95) for osteotomy depth and 0.89 (95% CI: 0.80-0.94) for wedge height.

Fixed wedge height ratios resulted in a correction error greater than ±1° relative to the angular-based method in up to 91% of infratubercle ACW-HTOs. Wedge height calculated from osteotomy depth and correction angle provides superior planning precision.

Level IV.