全膝关节置换术中的胫骨后倾和内外侧韧带平衡会显著影响膝关节屈曲
译者：张轶超
目的：检测术中胫股关节间隙和韧带平衡及影响它们的因素对于全膝置换术（TKA）后膝关节屈曲活动的影响。通过影像学方法对采用后交叉韧带保留型假体TKA（CR-TKA）术后的这些因素进行评估。股骨后髁的偏心距和胫骨后倾角都曾被作为影响CR-TKA术后功能的术中重要因素而被报道过。而在评估股骨后髁偏心距和胫骨后倾角时对于关节间隙和软组织平衡还不曾研究。
方法：使用一个偏离式张力测量器来测量胫股间隙和内外侧韧带平衡。对98个因内翻膝行CR-TKA的膝关节进行测量，测量屈曲0°、45°、90°和135°时的胫股关节间隙，测量从0-90°和0-135°过程中膝关节间隙的变化。
结果：在0-90°屈曲过程中，对胫股关节间隙变化影响最大的是股骨后髁偏心距差值（术前股骨后髁偏心距减去术后偏心距的值）。0-135°时的胫股关节间隙的变化明显与胫骨后倾角和135°时内外侧韧带平衡有关。术后膝关节屈曲度与术前膝关节屈曲度、γ角和术后胫骨后倾角有关。多元回归分析表明对于术后的膝关节屈曲度，术前膝关节屈曲度、γ角、术后胫骨后倾角和90°时内外侧软组织平衡情况是显著影响因素。屈曲角度的变化与术前屈曲角度、术后胫骨后倾角和90°时内外侧软组织平衡情况存在明显的相关性。
结论：术后膝关节屈曲度受多种因素的影响，尤其是对于CR-TKA。术中我们不光要重视胫骨后倾角还要关注屈曲位时内外侧软组织平衡。通过CR-TKA手术应该达到术后关节稳定，具有良好的关节活动度及改善患者的日常生活能力。
图1：图示为用于测量CR-TKA手术的张力器。由三部分组成：上部的跷跷板样平板（A），下面的带龙骨的平台基板（B)和位于关节外的主件（C）。上下板通过穿过髌内侧切口进入关节腔的一个偏心的臂（D）连接到主件上，从而不受髌股关节的影响。注意股骨组件在测量时一定要顶住股骨髁。
图2：图示为股骨假体和胫股假体成角：α：正侧位x片上显示的股骨假体和股骨干远端轴线间的夹角；β：正侧位x片上显示的胫骨假体和胫骨干近端轴线间的夹角；在一张准确的侧位片上测量的股骨假体前缘线与股骨远端轴线间的夹角减4°（由于NRG假体股骨前缘线与假体轴间存在4°夹角，所以减去4°所得角度才是假体轴线和股骨轴线间的真正夹角）；PTS：在一张准确的侧位片上测量的胫骨假体与腓骨干间的夹角加上3°（由于胫骨干和非骨干间存在3°夹角，所以加上3°后就是胫骨假体轴线和胫骨干间的真正夹角）。
Significant effect of the posterior tibial slope and medial/lateral ligament balance on knee flexion in total knee arthroplasty
Purpose: The intra-operative femorotibial joint gap and ligament balance, the predictors affecting these gaps and their balances, as well as the postoperative knee flexion, were examined. These factors were assessed radiographically after a posterior cruciate-retaining total knee arthroplasty (TKA). The posterior condylar offset and posterior tibial slope have been reported as the most important intra-operative factors affecting cruciate-retaining-type TKAs. The joint gap and balance have not been investigated in assessments of the posterior condylar offset and the posterior tibial slope.
Methods: The femorotibial gap and medial/lateral ligament balance were measured with an offset-type tensor. The femorotibial gaps were measured at 0°, 45°, 90° and 135° of knee flexion, and various gap changes were calculated at 0°-90° and 0°-135°. Cruciate-retaining-type arthroplasties were performed in 98 knees with varus osteoarthritis.
Results: The 0°-90° femorotibial gapchange was strongly affected by the posterior condylar offset value (postoperative posterior condylar offset subtracted by the preoperative posterior condylar offset). The 0°-135° femorotibial gap change was significantly correlated with the posterior tibial slope and the 135° medial/lateral ligament balance. The postoperative flexion angle was positively correlated with the preoperative flexion angle, γ angle and the posterior tibial slope. Multiple-regression analysis demonstrated that the preoperative flexion angle, γ angle, posterior tibial slope and 90° medial/lateral ligament balance were significant independent factors for the postoperative knee flexion angle. The flexion angle change (postoperative flexion angle subtracted by the preoperative flexion angle) was also strongly correlated with the preoperative flexion angle, posterior tibial slope and 90° medial/lateral ligament balance.
Conclusion: The postoperative flexion angle is affected by multiple factors, especially in cruciate-retaining-type TKAs. However, it is important to pay attention not only to the posterior tibial slope, but also to the flexion medial/lateral ligament balance during surgery. A cruciate-retaining-type TKA has the potential to achieve both stability and a wide range of motion and to improve the patients' activities of daily living.
文献出处：Fujimoto E, Sasashige Y, Masuda Y, Hisatome T, Eguchi A, Masuda T, Sawa M, Nagata Y. Significant effect of the posterior tibial slope and medial/lateral ligament balance on knee flexion in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2013 Dec;21(12):2704-12. doi: 10.1007/s00167-012-2059-6. Epub 2012 May 30. PMID: 22644073.