BACKGROUND:The postoperative varus/valgus stability assessment in stress X-rays has been established as an evaluation index. However, it is performed by the two-dimensional (2D) method rather than the three-dimensional (3D) method. OBJECTIVE:This study aimed to identify the precision and reproducibility of measuring varus/valgus stress X-rays three-dimensionally and to examine varus/valgus stability under anesthesia in imageless robotic assisted total knee arthroplasty (rTKA). METHODS:This prospective study analyzed 52 consecutive rTKAs (five males, 67 ± 5.3 years; 47 females, 74 ± 5.9 years). Postoperative varus/valgus stress X-rays in knee extension under anesthesia at manual maximum stress were three-dimensionally assessed by 2D–3D image matching technique using the 3D bone and component models. Varus/valgus angle between components (VV angle) in no stress, valgus stress, varus stress, medial joint opening (MJO), and lateral joint opening (LJO) were evaluated, clarifying this method’s precision and reproducibility and valgus/varus stability. RESULTS:All parameters’ precision and reproducibility had <1° mean differences and high intra- and inter-class correlation coefficients. Bland–Altman plots showed no fixed and proportional bias. Non-stress VV angle, valgus VV angle, varus VV angle, MJO, and LJO were 3.6 ± 1.2°, 1.0 ± 1.4°, 7.1 ± 1.9°, 1.5 ± 1.0 mm, and 2.8 ± 2.7 mm, respectively. CONCLUSION:This prospective study demonstrated that (1) the three-dimensional measurement method provided sufficient precision and reproducibility, and (2) the rTKAs could achieve good postoperative varus/valgus stability with a small standard deviation.

中文翻译：

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应用内翻/外翻应力 X 射线三维评估的无图像机器人辅助全膝关节置换术中的内翻/外翻稳定性

背景：应力X线评估术后内翻/外翻稳定性作为评价指标。然而，它是通过二维（2D）方法而不是三维（3D）方法来执行的。目的：本研究旨在确定三维测量内翻/外翻应力 X 射线的精度和再现性，并检查无图像机器人辅助全膝关节置换术 (rTKA) 麻醉下的内翻/外翻稳定性。方法：这项前瞻性研究分析了 52 例连续 rTKA（5 名男性，67 ± 5.3 岁；47 名女性，74 ± 5.9 岁）。术后内翻/外翻应力通过使用 3D 骨和组件模型的 2D-3D 图像匹配技术对麻醉下膝关节伸展最大应力下的 ​​X 射线进行三维评估。评估了无应力、外翻应力、内翻应力、内侧关节张度（MJO）和外侧关节张度（LJO）下的内翻/外翻角（VV角），阐明了该方法的精确度和再现性以及外翻/内翻稳定性。结果：所有参数的精密度和再现性均值差异<1°，且组内和组间相关系数较高。布兰德-奥特曼图显示没有固定和比例偏差。无应力VV角、外翻VV角、内翻VV角、MJO和LJO分别为3.6±1.2°、1.0±1.4°、7.1±1.9°、1.5±1.0mm和2.8±2.7mm。结论：这项前瞻性研究表明（1）三维测量方法提供了足够的精度和重复性，（2）rTKAs 可以实现良好的术后内翻/外翻稳定性，且标准差较小。