Friesenbichler Joerg, Leithner Andreas, Glehr Mathias, Sadoghi Patrick, Maurer-Ertl Werner, Avian Alexander, Windhager Reinhard
Department of Orthopedic Surgery, Medical University of Graz, Auenbruggerplatz 5, 8036 Graz, Austria.
Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Auenbruggerplatz 2, 8036 Graz, Austria.
ISRN Orthop. 2013 Jul 18;2013:701693. doi: 10.1155/2013/701693. eCollection 2013.
Purpose. Rotating hinge knee prostheses should provide a stable situation following reconstruction. We performed a biomechanical analysis to establish the association between design of the central rotational stem (peg) and implant's stability, in a theoretical setting. Methods. Six different rotating hinge designs were tested, and three observers performed two different measurements with a custom made biomechanical apparatus and laterally directed pressure. The aim was to assign the degree of tilting of the peg within the vertical post-in channel by extending the distraction as well as the maximum amount of distraction before the peg's dislocation. An intraclass-correlation coefficient (ICC) was calculated to determine the observer's reliability. Results. Implant designs with cylindrical pegs of different lengths were superior to implant designs with conical or other shaped pegs concerning stability and maximum amount of distraction before dislocation, showing steep rising distraction-angular displacement curves. The ICC at 15 mm and 25 mm of distraction revealed high interobserver reliability (P < 0.001). Conclusion. The biomechanical analysis showed that rotating hinge prostheses with long and cylindrical pegs have the highest stability at any given amount of distraction. Designs with shorter and markedly tapered pegs may become unstable under conditions of mild joint distraction which has to be proven in future in vivo investigations.
目的。旋转铰链膝关节假体在重建后应提供稳定状态。我们在理论环境中进行了生物力学分析，以确定中央旋转柄（栓）的设计与植入物稳定性之间的关联。方法。测试了六种不同的旋转铰链设计，三名观察者使用定制的生物力学装置和侧向压力进行了两种不同的测量。目的是通过延长牵张以及栓脱位前的最大牵张量来确定栓在垂直桩道内的倾斜程度。计算组内相关系数（ICC）以确定观察者的可靠性。结果。在稳定性和脱位前的最大牵张量方面，具有不同长度圆柱形栓的植入物设计优于具有锥形或其他形状栓的植入物设计，显示出陡峭上升的牵张 - 角位移曲线。在牵张15毫米和25毫米时的ICC显示出观察者间的高可靠性（P < 0.001）。结论。生物力学分析表明，在任何给定的牵张量下，具有长圆柱形栓的旋转铰链假体具有最高的稳定性。栓较短且明显渐缩的设计在轻度关节牵张的情况下可能会变得不稳定，这有待未来的体内研究证实。
