PURPOSE The current literature suggests that kinematic total knee arthroplasty (kTKA) may be associated with better outcome scores in patients with constitutional varus alignment. The underlying patellofemoral kinematic changes (patella tilting and patella tracking) and patellofemoral pressure distribution have not yet been described. The present study compared the effects of different tibial cuts, as used in kTKA, on patellofemoral knee kinematics and the pressure distribution, in addition to comparisons with the natural constitutional varus knee. METHODS Seven cadaveric knee joints with constitutional varus alignment were examined in the native state and after 0°, 3°, or 6° tibial cut cruciate-retaining (CR)-TKA using an established knee joint simulator. The effects on patella rotation/patella tilting, patellofemoral pressure, and patellofemoral length ratios (= patella tracking) were determined. In addition, the natural knee joint and different tibial cuts in CR-TKA were compared (Student's t test). RESULTS In the patellofemoral joint, 6° CR-TKA was associated with the greatest similarity with the natural constitutional varus knee. By contrast, knees subjected to 0° CR-TKA exhibited the largest deviations of patellar kinematics. The smallest difference compared with the natural knee joint concerning patella tilting was found for 6° CR-TKA (mean 0.4°, p < 0.001), and the largest difference was noted for 0° CR-TKA (mean 1.7°, p < 0.001). Concerning patellofemoral pressure, 6° CR-TKA resulted in outcomes most similar to the natural knee joint, featuring a mean difference of 3 MPa. The largest difference from the natural knee joint was identified for 0° CR-TKA, with an average difference of 8.1 MPa (p < 0.001; total mean 17.7 MPa). Meanwhile, 3° and 6° CR-TKA induced medialization of the patella, with the latter inducing the largest medialization value of 4.5 mm at 90° flexion. CONCLUSIONS The improved outcome parameters in kTKA described in the literature could be attributable to the similar kinematics of the patellofemoral joint relative to the normal state. The current study confirmed the similar kinematics between the native constitutional varus knee joint and knee joints subjected to 3° or 6° CR-TKA (patellofemoral rotation/patella tilting and patella pressure). Conversely, there was pronounced medialization of the patella following 6° CR-TKA. Patella pressure and patella tilting are described in the literature as possible causes of anterior knee pain after TKA, whereas medialization of the patella, which is also influenced by other causes, might play a subordinate role. LEVEL OF EVIDENCE V, Biomechanical study.

中文翻译：

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胫骨切开会影响全膝关节置换术中pa股股骨的运动学和压力分布，并符合内翻性。

目的目前的文献表明，运动性全膝关节置换术（kTKA）可能与体质性内翻对准患者的预后评分更高有关。潜在的pa股运动学改变（pat骨倾斜和骨跟踪）和pa股压力分布尚未描述。本研究比较了kTKA中使用的不同胫骨切口对pa股股骨运动学和压力分布的影响，并与自然体质内翻膝盖进行了比较。方法在7头胫骨切成十字形保留（CR）-TKA的自然状态下，使用已建立的膝关节模拟器，检查7个具有内翻结构的尸体膝关节。对on骨旋转/ pat骨倾斜，pa股压力，确定pa股长度比（= tracking骨追踪）。此外，比较了CR-TKA的自然膝关节和不同的胫骨切口（Student's t检验）。结果在the股关节中，6°CR-TKA与自然内翻膝关节的最大相似性相关。相比之下，经受0°CR-TKA的膝盖表现出pa骨运动学的最大偏差。6°CR-TKA与自然膝关节在6骨倾斜方面的差异最小（平均0.4°，p <0.001），而0°CR-TKA具有最大的差异（平均1.7°，p <0.001） ）。关于pa股压力，6°CR-TKA导致的结局与自然膝关节最相似，平均差为3 MPa。与自然膝关节的最大差异被确定为0°CR-TKA，平均差为8.1 MPa（p <0.001；总平均数为17.7 MPa）。同时，3°和6°CR-TKA诱导media骨的中度，后者在90°屈曲时产生4.5 mm的最大中度值。结论文献中描述的kTKA改善的预后参数可归因于relative股关节相对于正常状态的相似运动学。当前的研究证实了天然体质内翻膝关节和经受3°或6°CR-TKA（pat股旋转/ pat骨倾斜和骨压力）的膝关节之间的运动学相似。相反，在6°CR-TKA后media骨明显中化。literature骨压力和骨倾斜在文献中被描述为TKA后膝前疼痛的可能原因，而media骨的中转也受其他原因的影响，可能起次要作用。证据级别V，生物力学研究。