Department of Orthopaedic Surgery, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
BMC Musculoskelet Disord. 2022 Apr 9;23(1):341. doi: 10.1186/s12891-022-05203-1.
The choice of mobile bearing (MB) thickness is essential for obtaining successful results after mobile-bearing Oxford unicompartmental knee arthroplasty (UKA). This study aimed to investigate the effects of a 1-mm difference in bearing thickness on intraoperative MB movement and intraoperative knee kinematics in Oxford UKAs.
We prospectively investigated the effects of a 1-mm difference in bearing thickness on intraoperative MB movement and knee kinematics in 25 patients who underwent Oxford UKAs when surgeons didn't know which bearing thickness to choose with 1-mm difference. A trial tibial component that was scaled every 2 mm was used to measure the intraoperative MB movement, and the tibial internal rotation relative to the femur and the knee varus angle was simultaneously evaluated using the navigation system as the knee kinematics. We separately evaluated sets of two MB thicknesses with 1-mm differences, and we compared the intraoperative parameters at maximum extension; 30º, 45º, 60º, and 90º flexion; and maximum flexion between the thicker MB (thick group) and the thinner MB (thin group).
The MB in the thin group was located significantly posteriorly at 90º flexion compared with that in the thick group; however, there were no differences at the other flexion angles. There was significantly less tibial internal rotation in the thin group at 90º flexion than that in the thick group; however, there were no differences at the other flexion angles. The knee varus angles in the thick group were significantly smaller than those in the thin group by approximately one degree at all angles other than at 30º and 45º flexion.
The thicker MB could bring the less posterior MB movement and the more tibial internal rotation at 90º flexion, additionally the valgus correction angle in the thicker MB should be paid attention. These results could help surgeons to decide the thickness of MBs when they wonder the thickness of MB.
对于获得移动轴承（MB）厚度的成功结果，移动轴承牛津单间膝关节置换术（UKA）后选择是至关重要的。本研究旨在探讨MB厚度相差 1 毫米对牛津 UKA 术中 MB 运动和术中膝关节运动学的影响。
我们前瞻性地研究了在不知道选择哪种 MB 厚度相差 1 毫米时，25 例接受牛津 UKA 的患者中，1 毫米的 MB 厚度差异对术中 MB 运动和膝关节运动学的影响。使用经过缩放的每 2 毫米的试验胫骨组件来测量术中 MB 运动，同时使用导航系统评估胫骨相对于股骨的内旋转和膝关节内翻角，作为膝关节运动学。我们分别评估了两套相差 1 毫米的 MB 厚度，比较了最大伸展时的术中参数；30°、45°、60°和 90°屈曲；以及较厚 MB（厚组）和较薄 MB（薄组）之间的最大屈曲。
在 90°屈曲时，薄组的 MB 明显位于后侧，而厚组则没有；然而，在其他屈曲角度上没有差异。在 90°屈曲时，薄组的胫骨内旋明显小于厚组；然而，在其他屈曲角度上没有差异。在除 30°和 45°屈曲外的所有角度，厚组的膝关节内翻角均明显小于薄组，约为 1 度。
较厚的 MB 在 90°屈曲时可以带来较少的 MB 向后运动和更多的胫骨内旋转，此外，较厚的 MB 的外翻矫正角度也应注意。这些结果可以帮助外科医生在考虑 MB 厚度时决定 MB 的厚度。
