Versailles-Saint-Quentin University, André-Mignot Hospital, Versailles Hospital Center, Department of Orthopaedics and Trauma, 177, rue de Versailles, 78157 Le-Chesnay, France.
Orthop Traumatol Surg Res. 2011 Nov;97(7):699-704. doi: 10.1016/j.otsr.2011.05.006. Epub 2011 Oct 10.
Various surgical techniques have been described to set the rotational alignment of the tibial baseplate during total knee arthroplasty. The self-positioning method ("self-adjustment") aligns the tibial implant according to the rotational alignment of the femoral component which is used as a reference after performing repeated knee flexion/extension cycles. Postoperative computed tomography scanning produces accurate measurements of the tibial baseplate rotational alignment with respect to the femoral component.
The rotational positioning of the tibial baseplate matches the rotation of the femoral component with parallel alignment to the prosthetic posterior bicondylar axis.
A 3-month follow-up CT scan was carried out after primary total knee arthroplasty implanted in osteoarthritic patients with a mean 7.8° varus deformity of the knee in 50 cases and a mean 8.7° valgus deformity of the knee in 44 cases. The NexGen LPS Flex (Zimmer) fixed-bearing knee prosthesis was used in all cases. An independant examiner (not part of the operating team) measured different variables: the angle between the anatomic transepicondylar axis and the posterior bicondylar axis of the femoral prosthesis (prosthetic posterior condylar angle), the angle between the posterior bicondylar axis and the posterior marginal axis of the tibial prosthesis, the angle between the posterior marginal axis of the tibial prosthesis and the posterior marginal axis of the tibial bone and finally the angle between the anatomic transepicondylar axis and the posterior marginal axis of the tibial prosthesis.
For the genu varum and genu valgum subgroups, the mean posterior condylar axis of the femoral prosthesis was 3.1° (SD: 1.91; extremes 0° to 17.5°) and 4.7° (SD: 2.7; extremes 0° to 11°) respectively. The tibial baseplate was placed in external rotation with respect to the femoral component: 0.7° (SD : 4.45; extremes -9.5° to 9.8°) and 0.9° (SD: 4.53; extremes -10.8° to 9.5°), but also to the native tibia: 6.1° (SD: 5.85; extremes -4.6° to 22.5°) and 12.5° (SD: 8.6; extremes -10° to 28.9°). The tibial component was placed in internal rotation relative to the anatomic transepicondylar axis: 1.9° (SD : 4.93; extremes -13.6° to 7°) and 3° (SD : 4.38; extremes -16.2° to 4.8°).
The tibial component is aligned parallel to the femoral component whatever the initial frontal deformity (P≅0.7). However, a difference was observed between the rotational alignment of the tibial baseplate and the native tibia depending on the initial deformity and could be attributed to the morphological variations of the bony tibial plateau in case of genu valgum.
The self-positioning method is a reproducible option when using this type of implant since it allows the tibial component to be positioned parallel to the posterior border of the femur.
在全膝关节置换术中，已经描述了各种手术技术来设置胫骨基板的旋转对线。自定位方法（“自调整”）根据股骨组件的旋转对线来对齐胫骨植入物，在进行多次膝关节屈伸循环后，股骨组件用作参考。术后计算机断层扫描（CT）扫描可准确测量胫骨基板相对于股骨组件的旋转对线。
胫骨基板的旋转定位与股骨组件的旋转定位相匹配，与假体后髁间轴平行。
对 50 例膝关节平均有 7.8°内翻畸形和 44 例膝关节平均有 8.7°外翻畸形的骨关节炎患者进行初次全膝关节置换后，进行了 3 个月的 CT 随访检查。所有病例均使用 NexGen LPS Flex（Zimmer）固定轴承膝关节假体。一位独立的检查者（非手术团队成员）测量了以下变量：解剖后上髁间轴与股骨假体后髁间轴之间的角度（假体后髁间角）、后髁间轴与胫骨假体后缘轴之间的角度、胫骨假体后缘轴与胫骨后缘轴之间的角度以及解剖后上髁间轴与胫骨假体后缘轴之间的角度。
对于膝内翻和膝外翻亚组，股骨假体的平均后髁间轴分别为 3.1°（SD：1.91；极端值 0°至 17.5°）和 4.7°（SD：2.7；极端值 0°至 11°）。胫骨基板相对于股骨组件呈外旋：0.7°（SD：4.45；极端值-9.5°至 9.8°）和 0.9°（SD：4.53；极端值-10.8°至 9.5°），但也相对于胫骨固有：6.1°（SD：5.85；极端值-4.6°至 22.5°）和 12.5°（SD：8.6；极端值-10°至 28.9°）。胫骨组件相对于解剖后上髁间轴呈内旋：1.9°（SD：4.93；极端值-13.6°至 7°）和 3°（SD：4.38；极端值-16.2°至 4.8°）。
无论初始额状面畸形如何（P≅0.7），胫骨组件均与股骨组件平行对齐。然而，根据初始畸形，观察到胫骨基板的旋转对线与胫骨固有之间存在差异，这可能归因于膝外翻时胫骨平台的形态变异。
当使用这种类型的植入物时，自定位方法是一种可重复的选择，因为它允许胫骨组件与股骨的后缘平行定位。
