Orthopaedic Department, University Hospital Jena, Campus Eisenberg, Klosterlausnitzer Straße 81, 07607, Eisenberg, Germany.
Center for Orthopaedics, Trauma Surgery and Rehabilitation Medicine, University Medicine Greifswald, 17475, Greifswald, Germany.
Arch Orthop Trauma Surg. 2024 May;144(5):2267-2271. doi: 10.1007/s00402-024-05253-1. Epub 2024 Apr 8.
The symmetry of the flexion and extension gap influences the functional and long-term outcome after total knee arthroplasty (TKA). Most surgeons check it by applying varus and valgus stress using spacers. This technique has limited accuracy and could be easily extended by rotational movement of the spacer. The objective was to determine the detection threshold and interobserver reliability of this technique. In an in vitro setting with a human cadaveric knee, gap asymmetries were simulated by different medially and laterally applied forces. Using an optical measurement system, the pivot point of the spacer was calculated as a function of the gap symmetry in the first part of the experiment. In the second part, the detection threshold and interobserver reliability of 4 surgeons were determined. For this purpose, gap asymmetries were adjusted to between 0 and 120N in a blinded trial. With a symmetrical gap, the centre of rotation of the spacer was located in the centre of the tibia. With increasing gap asymmetry, the centre of rotation of the spacer shifted to the tight side. This shift was approximately linearly dependent on the force difference. A perfectly balanced gap was detected by the examiners in 50% of the cases. From a force difference of 40N, all examiners identified the gap asymmetry in all cases (ICC = 1.0). The method of spacer rotation described is suitable for reliably detecting gap differences at ≥ 40N, independently of the examiner.
膝关节伸直和屈曲间隙的对称性会影响全膝关节置换术（TKA）后的功能和长期结果。大多数外科医生通过使用间隔物施加内翻和外翻应力来检查间隙。这种技术的准确性有限，并且很容易通过间隔物的旋转运动而扩展。目的是确定这种技术的检测阈值和观察者间可靠性。在一个人体尸体膝关节的体外环境中，通过不同的内侧和外侧应用力来模拟间隙不对称。使用光学测量系统，作为实验第一部分的间隙对称性的函数，计算了间隔物的旋转点。在第二部分中，确定了 4 位外科医生的检测阈值和观察者间可靠性。为此，在盲法试验中将间隙不对称性调整至 0 到 120N 之间。在对称间隙中，间隔物的旋转中心位于胫骨的中心。随着间隙不对称性的增加，间隔物的旋转中心向紧张侧移动。这种移位与力差大致呈线性相关。在 50%的情况下，检查者检测到了完全平衡的间隙。从 40N 的力差开始，所有检查者在所有情况下都能识别出间隙不对称（ICC=1.0）。所描述的间隔物旋转方法适用于在≥40N 时可靠地检测间隙差异，而与检查者无关。
