Sangaletti Rudy, Montagna Alice, Calandra Giulio, Andriollo Luca, Bna Claudio, Benazzo Francesco, Rossi Stefano Marco Paolo
Sezione di Chirurgia Protesica ad Indirizzo Robotico, Unità di Traumatologia dello Sport, U.O.C Ortopedia e Traumatologia Fondazione Poliambulanza, Brescia, Italy.
Università degli Studi di Pavia, Pavia, Italy.
Knee Surg Sports Traumatol Arthrosc. 2025 Jun;33(6):2222-2229. doi: 10.1002/ksa.12615. Epub 2025 Feb 4.
Alignment strategies in knee arthroplasty have a profound influence not only on knee biomechanics but also on the biomechanics of adjacent joints, particularly the ankle. Functional alignment (FA) represents a flexible alignment strategy aimed at achieving patient-specific balance. However, predefined boundaries are often applied to ensure mechanical stability, leading to adjustments in the medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) while still respecting the patient's native alignment as much as possible. FA is a patient-specific strategy that seeks to respect the patient's preoperative phenotype or constitutional alignment while achieving a balanced and stable knee. The hypothesis is that FA strategies can protect the ankle from excessive biomechanical stress.
A retrospective cohort analysis was conducted on 300 consecutive patients who underwent robotic-assisted knee arthroplasty. Preoperative and 6-month post-operative radiographic evaluations measured key ankle parameters, tibial plafond inclination (TPI), talar inclination (TI) and Talar Tilt (TT). Statistical analyses evaluated the influence of alignment strategies on these parameters, with particular focus on whether MPTA and LDFA crossed the 90° threshold, indicating a shift from varus to valgus or vice versa.
FA demonstrated smaller changes in ankle parameters compared to mechanical alignment (MA). In the FA group, mean changes were 1.8° for KTPA (standard deviation [SD] = 1.1°, p = 0.03), 2.4° for TPI (SD = 1.0°, p = 0.04), 2.1° for TI (SD = 1.3°, p = 0.05) and 1.7° for TT (SD = 0.9°, p = 0.04). The MA group showed greater deviations: 3.9° for KTPA (SD = 1.5°, p = 0.01), 5.2° for TPI (SD = 1.2°, p = 0.02), 4.8° for TI (SD = 1.4°, p = 0.03) and 3.6° for TT (SD = 1.1°, p = 0.04). Alterations in LDFA and MPTA exceeding 2° were significantly associated with worsening ankle alignment. Furthermore, FA, with its goal of maintaining Coronal Plane Alignment of the Knee (CPAK) classification, was associated with minimal modifications to ankle angles, suggesting potential biomechanical benefits as reported in the literature.
FA was associated with smaller changes in ankle alignment parameters, indicating its ability to better preserve native joint positioning. Future research should focus on longitudinal studies to confirm these benefits and further establish the FA strategy as a standard in knee arthroplasty, particularly its capacity to maintain CPAK classification alignment.
Level III.
膝关节置换术中的对线策略不仅对膝关节生物力学有深远影响，对相邻关节尤其是踝关节的生物力学也有重大影响。功能对线（FA）是一种灵活的对线策略，旨在实现针对患者个体的平衡。然而，为确保机械稳定性，常应用预定义边界，这会导致胫骨近端内侧角（MPTA）和股骨远端外侧角（LDFA）发生调整，同时仍尽可能尊重患者的自然对线。FA是一种针对患者个体的策略，旨在在实现膝关节平衡和稳定的同时，尊重患者术前的表型或结构对线。假设是FA策略可保护踝关节免受过度生物力学应力。
对300例连续接受机器人辅助膝关节置换术的患者进行回顾性队列分析。术前和术后6个月的影像学评估测量了关键的踝关节参数，包括胫骨平台倾斜度（TPI）、距骨倾斜度（TI）和距骨倾斜角（TT）。统计分析评估了对线策略对这些参数的影响，特别关注MPTA和LDFA是否超过90°阈值，这表明从内翻到外翻或反之的转变。
与机械对线（MA）相比，FA显示踝关节参数变化较小。在FA组中，KTPA的平均变化为1.8°（标准差[SD]=1.1°，p=0.03），TPI为2.4°（SD=1.0°，p=0.04），TI为2.1°（SD=1.3°，p=0.05），TT为1.7°（SD=0.9°，p=0.04）。MA组显示出更大的偏差：KTPA为3.9°（SD=1.5°，p=0.01），TPI为5.2°（SD=1.2°，p=0.02），TI为4.8°（SD=1.4°，p=0.03），TT为3.6°（SD=1.1°，p=0.04）。LDFA和MPTA超过2°的改变与踝关节对线恶化显著相关。此外，以维持膝关节冠状面对线（CPAK）分类为目标的FA与踝关节角度的最小改变相关，这表明文献中报道的潜在生物力学益处。
FA与踝关节对线参数的较小变化相关，表明其能够更好地保留关节的自然位置。未来的研究应侧重于纵向研究，以证实这些益处，并进一步将FA策略确立为膝关节置换术的标准，特别是其维持CPAK分类对线的能力。
三级。
