Ma Yuan, Mizu-Uchi Hideki, Okazaki Ken, Ushio Tetsuro, Murakami Koji, Hamai Satoshi, Akasaki Yukio, Nakashima Yasuharu
Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Tokyo Women's Medical University, 8-1, Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
Arch Orthop Trauma Surg. 2018 Jan;138(1):105-114. doi: 10.1007/s00402-017-2828-2. Epub 2017 Oct 26.
Placement of tibial component is expected to fulfill both maximum surface coverage and recommended anterior-posterior (AP) alignment in total knee arthroplasty (TKA). The purpose of this study is to evaluate the effect of the tibial baseplate shape on AP axis.
Virtual surgery of TKA was performed with three-dimensional bone models reconstructed from 77 osteoarthritis varus knees. Two differently designed tibial baseplates, symmetrically and anatomically, were set to the cut surface under posterior slopes of 0°, 3°, and 7°. The AP axes were defined by connecting the geometrical center of the cut surface with the medial edge (axis MED) and medial 1/3 (axis 1/3MED) of patella tendon attachment. We evaluated the overhang rates as well as the most fitting AP axis which passes through the geometric center.
Overhang rates when aligned to axis MED were 12-25% for the symmetrical-type group and 13-22% for the anatomical-type group. Overhang rates when aligned to axis 1/3MED were 42-48% for the symmetrical-type group and 3-7% for the anatomical-type group. The most fitting AP axis of tibial baseplate was located 2.5° external to axis MED for the symmetrical-type group and around 3.3° internal to axis 1/3MED for the anatomical-type group.
Symmetrically or anatomically designed tibial baseplates have their own favored AP axis and specific performance on coverage. When aligned to axis 1/3MED, anatomically designed tibial baseplates will effectively lower the mismatch rates compared to a symmetrically designed tibial baseplate. Orthopaedic surgeons are expected to place the tibial components to the cut surface during TKA with full understanding of the features between different baseplate designs, AP axes, and posterior slopes for an ideal tibial rotational position.
在全膝关节置换术（TKA）中，胫骨假体的放置应实现最大表面覆盖和推荐的前后（AP）对线。本研究的目的是评估胫骨基板形状对AP轴的影响。
使用从77例骨关节炎内翻膝关节重建的三维骨模型进行TKA虚拟手术。将两种不同设计的胫骨基板，即对称型和解剖型，设置在0°、3°和7°后倾的截骨面上。AP轴通过连接截骨面的几何中心与髌腱附着点的内侧边缘（MED轴）和内侧1/3（1/3MED轴）来定义。我们评估了悬垂率以及通过几何中心的最合适的AP轴。
对称型组与MED轴对齐时的悬垂率为12%-25%，解剖型组为13%-22%。对称型组与1/3MED轴对齐时的悬垂率为42%-48%，解剖型组为3%-7%。对称型组胫骨基板最合适的AP轴位于MED轴外侧2.5°，解剖型组位于1/3MED轴内侧约3.3°。
对称或解剖设计的胫骨基板有各自偏好的AP轴和特定的覆盖性能。与对称设计的胫骨基板相比，解剖设计的胫骨基板与1/3MED轴对齐时将有效降低不匹配率。预计骨科医生在TKA期间将胫骨假体放置在截骨面上时，要充分了解不同基板设计、AP轴和后倾之间的特征，以实现理想的胫骨旋转位置。
