Background:Unintended secondary changes in the posterior tibial slope (PTS) and tibial torsion angle (TTA) may occur after medial open-wedge high tibial osteotomy (MOWHTO). In surgical procedures using patient-specific instruments (PSIs), it is essential to reproduce the PTS and TTA that were planned in simulations.Purpose:To analyze the factors causing unintended sagittal and axial alignment changes after MOWHTO.Study Design:Case series; Level of evidence, 4.Methods:Overall, 63 patients (70 knees) who underwent MOWHTO using a PSI between June 2020 and June 2023 were retrospectively reviewed. Preoperative and postoperative computed tomography scans were 3-dimensionally reconstructed. Simulated osteotomy was performed so that the weightbearing line could pass through the target point. A PSI gapper was 3-dimensionally printed to fit the posteromedial corner of the osteotomy gap in the simulated HTO model. After MOWHTO using the PSI gapper, the actual postoperative model was compared with the preoperative or simulation model. This assessment included PTS, TTA, hinge axis, and osteotomy-related parameters. Cortical breakage around the lateral hinge was evaluated to assess stability.Results:The mean PTS and TTA did not change in the simulation. However, significant changes were observed in the actual postoperative PTS and TTA (change, –2.4°± 2.2° and −3.9°± 4.7°, respectively). The PTS was reduced, while the TTA decreased with internal rotation of the distal fragment. The difference in the axial hinge axis angle (AHA) between the simulation and actual surgery was the factor most correlated with the difference in the PTS ( r = 0.625; P < .001). In regression analysis, the difference in the AHA was the only factor associated with the difference in the PTS (β = 0.558; P = .001), and there were no factors that showed any significant associations with the difference in the TTA. In subgroup analyses for the change in the TTA, the correction angle and anterior osteotomy angle were significantly higher in the more internal rotation group ( P = .023 and P = .010, respectively). The TTA change was significantly higher in the unstable group with lateral cortical breakage ( P = .018). The unstable group was more likely to show an internal rotation of ≥5° (odds ratio, 5.0; P = .007).Conclusion:The AHA was associated with a difference in the PTS between the simulation and actual surgery. The change in the TTA was caused by a combination of multiple factors, such as a large correction angle and anterior osteotomy angle, but mainly by instability of the lateral cortical hinge.

中文翻译：

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导致胫骨高位截骨术中意外矢状和轴向对准变化的因素：模拟与实际手术的比较 3 维分析

背景：胫骨内侧开放楔形高位截骨术（MOWHTO）后可能会发生胫骨后坡度（PTS）和胫骨扭转角（TTA）的意外继发变化。在使用患者专用器械 (PSI) 的外科手术中，必须重现模拟中计划的 PTS 和 TTA。目的：分析 MOWHTO 后导致意外矢状和轴向对准变化的因素。研究设计：病例系列；证据级别，4。方法：总体而言，对 2020 年 6 月至 2023 年 6 月期间使用 PSI 接受 MOWHTO 的 63 名患者（70 膝）进行了回顾性审查。术前和术后计算机断层扫描进行了 3 维重建。进行模拟截骨，使负重线穿过目标点。 3 维打印 PSI 间隙器以适合模拟 HTO 模型中截骨间隙的后内侧角。 MOWHTO 使用 PSI 间隙器后，将实际术后模型与术前或模拟模型进行比较。该评估包括 PTS、TTA、铰链轴和截骨相关参数。通过评估侧铰链周围的皮质破损来评估稳定性。结果：模拟中平均 PTS 和 TTA 没有变化。然而，实际术后 PTS 和 TTA 发生了显着变化（变化分别为 –2.4°± 2.2° 和 -3.9°± 4.7°）。随着远端碎片的内旋，PTS 降低，而 TTA 降低。模拟与实际手术之间的轴向铰链轴角度 (AHA) 差异是与 PTS 差异最相关的因素 ( r = 0.625；P < .001)。在回归分析中，AHA 的差异是与 PTS 差异相关的唯一因素（β = 0.558；P = .001），并且没有任何因素显示与 TTA 差异有任何显着关联。在 TTA 变化的亚组分析中，更多内旋组的矫正角度和前截骨角度显着更高（分别为 P = .023 和 P = .010）。具有外侧皮质破损的不稳定组的 TTA 变化显着较高 ( P = .018)。不稳定组更有可能表现出 ≥5​​° 的内旋（比值比，5.0；P = .007）。结论：AHA 与模拟手术和实际手术之间的 PTS 差异相关。 TTA的变化是由大矫正角、前截骨角等多种因素共同引起的，但主要是外侧皮质铰链不稳定所致。