Yamaguchi Katsuki, Sakai Tatsuya, Fujii Masanori, Takashima Satoshi, Eto Shuichi, Matsumura Yosuke, Nagamine Satomi, Tanaka Hirofumi
Department of Orthopaedic Surgery, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan.
Department of Orthopaedic Surgery, National Hospital Organization Saga National Hospital, 1-20-1 Hinode, Saga, 849-0923, Japan.
Knee Surg Relat Res. 2025 May 8;37(1):20. doi: 10.1186/s43019-025-00272-7.
Total knee arthroplasty (TKA) alters the lower extremity alignment, potentially affecting adjacent joints such as the ankle and subtalar joints. However, the relationship between changes in hindfoot alignment and ankle osteoarthritis (OA) after TKA remains incompletely understood. The purpose of this study was to clarify whether ankle and subtalar alignment normalizes after TKA and to identify factors associated with persistent malalignment.
We retrospectively analyzed 331 patients who underwent unilateral mechanical alignment (MA) TKA for knee osteoarthritis. A control group of 40 healthy subjects was used to define normal alignment ranges. Whole-leg anteroposterior weight-bearing radiographs were obtained preoperatively and 2 months postoperatively. Alignment parameters included the hip-knee-ankle angle (HKA), tibiotalar tilt angle (TTA), tibial plafond inclination angle (TPIA), talar inclination angle (TIA), and hindfoot alignment angle (HAA). Pre- and postoperative values were compared using the Wilcoxon signed-rank test, and changes in the proportion of patients within the normal range were determined. Wilcoxon rank-sum tests and chi-squared tests were used for group comparisons, and multivariate logistic regression identified independent predictors of persistent malalignment.
HKA improved after TKA (-12° to -2.0°), with corresponding improvements in TPIA (99° to 94°) and TIA (99° to 95°) (all p < 0.001), indicating a significant correction toward neutral alignment. The proportion of patients within normal range increased postoperatively from 16% to 85% for HKA, 26% to 67% for TPIA, 24% to 64% for TIA, and 65% to 73% for HAA. Multivariate analysis identified ankle OA (odds ratio [OR] = 6.62 for TTA), female sex (OR = 2.32 for TPIA; OR = 3.19 for TIA), and varus knee alignment (OR = 2.81 for TIA) as independent predictors of persistent malalignment.
MA-TKA facilitates partial normalization of coronal hindfoot alignment, particularly at the tibial plafond and talus. However, female sex, varus knee deformity, and pre-existing ankle OA independently limit full correction. These findings highlight the biomechanical interdependence between the knee and hindfoot and may guide surgical decision-making and patient-specific alignment strategies.
全膝关节置换术（TKA）会改变下肢力线，可能影响相邻关节，如踝关节和距下关节。然而，TKA后后足力线变化与踝关节骨关节炎（OA）之间的关系仍未完全明确。本研究的目的是阐明TKA后踝关节和距下关节力线是否恢复正常，并确定与持续畸形相关的因素。
我们回顾性分析了331例行单侧机械对线（MA）TKA治疗膝关节骨关节炎的患者。以40名健康受试者作为对照组来确定正常力线范围。术前和术后2个月获取全下肢负重前后位X线片。力线参数包括髋-膝-踝角（HKA）、胫距倾斜角（TTA）、胫骨平台倾斜角（TPIA）、距骨倾斜角（TIA）和后足力线角（HAA）。使用Wilcoxon符号秩检验比较术前和术后的值，并确定正常范围内患者比例的变化。使用Wilcoxon秩和检验和卡方检验进行组间比较，并通过多因素逻辑回归确定持续畸形的独立预测因素。
TKA后HKA得到改善（从-12°至-2.0°），TPIA（从99°至94°）和TIA（从99°至95°）也相应改善（所有p＜0.001）表明向中立位力线有显著矫正。术后HKA正常范围的患者比例从16%增加到85%，TPIA从26%增加到67%，TIA从24%增加到64%，HAA从65%增加到73%。多因素分析确定踝关节OA（TTA的比值比[OR]=6.62）、女性（TPIA的OR=2.32；TIA的OR=3.19）和膝内翻力线（TIA的OR=2.81）是持续畸形的独立预测因素。
MA-TKA有助于冠状面后足力线部分恢复正常，尤其是在胫骨平台和距骨处。然而，女性、膝内翻畸形和既往存在的踝关节OA独立限制了完全矫正。这些发现突出了膝关节和后足之间的生物力学相互依存关系，并可能指导手术决策和针对患者的力线策略。
