PURPOSE Different alignment types for a better outcome after TKA were described. However, it is not clear how kinematic alignment influences knee joint kinematic. The purpose of this study was to analyze whether adapted tibial cuts in constitutional varus knees affect knee joint kinematics regarding femoral roll-back, varus/valgus angle, and femorotibial rotation. METHODS Seven cadaveric knees with constitutional varus alignment were examined in the native state and after implantation of a cruciate retaining (CR)-TKA with 0°, 3° and 6° tibia cuts using an established knee joint simulator. The effects of varus alignment on femorotibial rollback and rotation was determined. In addition, the native knee joint and different tibial cuts in CR-TKA were compared with Student's t test. RESULTS Total knee replacement with a 3° and 6° varus tibia cut had the greatest varus deviation to the native knee (mean 1.6° ± 0.09°, respectively); while, knees with a 0° (mean 0.2° ± 0.01°) tibia cut were most similar to the constitutional varus knee joint. The femoral roll-back in the medial compartment was increased in the native knee (5.7-12.5 mm). A 6° varus cut had a restricted translation in the medial compartment (2-3.2 mm). In the lateral compartment, the extensive translation was observed with a 0° varus cut, followed by 3° and 6° and the native knee. All cuts showed significantly different mean values. Only the cuts at 3° and at 6° in the medial compartment and the cuts at 0° and at 3° in the lateral compartment did not differ significantly. In respect to tibiofemoral rotation, 0° and 3° varus cuts across all loads had the least difference to the native knee (3.4°), with a 0° varus cut showing a higher absolute internal rotation of the tibia than the native knee. Changes in knee kinematics of the tibiofemoral rotation showed significantly different mean values. CONCLUSION The potentially improved outcome parameters in TKA with adapted tibia cuts in constitutional varus knees cannot be completely explained by the changes to knee kinematics. Mechanical alignment seems to result in more balanced load distribution and kinematics more closely resembling the native knee. From a kinematic point of view, it is not recommended to place the tibia in more than 3° of varus. LEVEL OF EVIDENCE Biomechanical study.

中文翻译：

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全膝关节置换术中胫骨切口会影响内翻性内翻患者的内翻对准，股骨回滚和胫股旋转。

目的描述了TKA后不同的比对类型以获得更好的结果。但是，尚不清楚运动学对准如何影响膝关节运动学。这项研究的目的是分析适应性内翻膝关节的胫骨切口是否影响股骨回滚，内翻/外翻角度和股骨旋转的膝关节运动学。方法在原始状态下，使用已建立的膝关节模拟器，以0°，3°和6°胫骨切口植入十字形保持（CR）-TKA后，检查七个具有内翻结构的尸体膝盖。确定内翻对准对股骨胫骨回滚和旋转的影响。此外，将CR-TKA的天然膝关节和不同胫骨切口与Student's t检验进行了比较。结果胫骨内翻3°和6°进行全膝关节置换时，与自然膝的内翻偏差最大（分别为1.6°±0.09°）。胫骨切口为0°（平均0.2°±0.01°）的膝盖与内翻膝关节最为相似。天然膝关节（5.7-12.5 mm）增加了内侧隔室的股骨回缩。6°内翻切口在内侧腔室（2-3.2毫米）内平移受限。在外侧室中，观察到广泛的平移，内翻切口为0°，然后是3°和6°，然后是自然膝。所有切割均显示出明显不同的平均值。内侧隔室中只有3°和6°的切口，外侧隔室中0°和3°的切口没有显着差异。关于胫股旋转 在所有负荷下，0°和3°内翻切口与天然膝关节的差异最小（3.4°），0°内翻切口显示胫骨的绝对内旋度高于天然膝关节。胫股旋转的膝关节运动学变化显示出明显不同的平均值。结论膝关节运动学的改变不能完全解释在适应性内翻胫骨中采用适当的胫骨切口在TKA中潜在改善的预后参数。机械对齐似乎导致更均衡的负载分配，并且运动学更类似于本机膝盖。从运动学的角度来看，不建议将胫骨放置于内翻3度以上。证据级别生物力学研究。内翻0°切开显示胫骨的绝对内部旋转度比天然膝关节高。胫股旋转的膝关节运动学变化显示出明显不同的平均值。结论膝关节运动学的改变不能完全解释在适应性内翻胫骨中采用适当的胫骨切口在TKA中潜在改善的预后参数。机械对齐似乎导致更均衡的负载分配，并且运动学更类似于本机膝盖。从运动学的角度来看，不建议将胫骨放置于内翻3度以上。证据级别生物力学研究。内翻为0°时，胫骨的绝对内部旋转度要比天然膝关节高。胫股旋转的膝关节运动学变化显示出明显不同的平均值。结论膝关节运动学的改变不能完全解释在适应性内翻胫骨中采用适当的胫骨切口在TKA中潜在改善的预后参数。机械对齐似乎导致更均衡的负载分配，并且运动学更类似于本机膝盖。从运动学的角度来看，不建议将胫骨放置于内翻3度以上。证据级别生物力学研究。结论膝关节运动学的改变不能完全解释在适应性内翻胫骨中采用适当的胫骨切口在TKA中潜在改善的预后参数。机械对齐似乎导致更均衡的负载分配，并且运动学更类似于本机膝盖。从运动学的角度来看，不建议将胫骨放置于内翻3度以上。证据级别生物力学研究。结论膝关节运动学的改变不能完全解释在适应性内翻胫骨中采用适当的胫骨切口在TKA中潜在改善的预后参数。机械对齐似乎导致更均衡的负载分配，并且运动学更类似于本机膝盖。从运动学的角度来看，不建议将胫骨放置于内翻3度以上。证据级别生物力学研究。