St.-Vinzenz Hospital, Department of Trauma, Orthopaedics, Hand- and Reconstructive Surgery, Teaching Hospital, University of Cologne, Merheimer Strasse 221-223, D-50733 Cologne, Germany.
Injury. 2010 Feb;41(2):156-60. doi: 10.1016/j.injury.2009.07.007. Epub 2009 Aug 8.
The aim of the present study was to compare the primary fixation stability and initial fixation stiffness of two established fixation techniques, the tension band wiring technique and interfragmentary screw fixation, with a mini-screw fragment fixation system in a model of transverse patella fracture. It was hypothesised that the biomechanical loading performance of the fragment fixation system would not significantly differ from the loading characteristics of the two established methods currently investigated.
Ninety-six calf patellae were used in this biomechanical model. A standardized transverse patella fracture was induced and three different fixation methods, including the modified tension band wiring technique, interfragmentary screw fixation, and the mini-screw fragment fixation system, were used for fragment fixation. Specimens were mounted to a loading rig which was secured within a material testing machine. In each fixation group, eight specimens were loaded to failure at a simulated knee angle of either 0 degrees or 45 degrees . Another eight specimens were submitted to a polycyclic loading protocol consisting of 30 cycles between 20N and 300N at a simulated knee angle of 0 degrees or 45 degrees . The residual displacement between the first and the last cycle was recorded. Differences in the biomechanical performance between the three fixation groups were evaluated.
No significant differences between the three fixation groups were observed in the parameters maximum load to failure and linear fixation stiffness with monocyclic loading. Specimens being loaded at 45 degrees showed significantly lower maximum failure loads and linear stiffness when compared with 0 degrees . During polycyclic loading, no significant differences in the residual displacement were observed between the groups at 0 degrees loading angle, while at 45 degrees , residual displacement was significantly higher with tension band fixation when compared with interfragmentary screw fixation or the fragment fixation system.
The biomechanical performance of the fragment fixation system was comparable to interfragmentary screw fixation and superior to the tension band wiring technique. Given the advantages of a system which provides interfragmentary compression and which simplifies fracture fixation after open or closed reduction, we believe the fragment fixation system to be an adequate alternative in the osteosynthesis of transverse patella fractures.
本研究旨在比较两种已建立的固定技术，即张力带钢丝技术和断端螺钉固定，与微型螺钉碎片固定系统在横断髌骨骨折模型中的主要固定稳定性和初始固定刚度。假设碎片固定系统的生物力学加载性能不会与目前研究的两种已建立方法的加载特性有显著差异。
本生物力学模型使用了 96 个小牛髌骨。在标准化的横断髌骨骨折模型中，使用了三种不同的固定方法，包括改良张力带钢丝技术、断端螺钉固定和微型螺钉碎片固定系统。标本安装在加载装置中，该装置固定在材料试验机上。在每个固定组中，有 8 个标本在模拟膝关节角度为 0 度或 45 度的情况下进行失效加载。另外 8 个标本在模拟膝关节角度为 0 度或 45 度的情况下进行 30 个循环的多循环加载，循环范围为 20N 至 300N。记录第一循环和最后循环之间的残余位移。评估三种固定组之间的生物力学性能差异。
在单循环加载时，三种固定组之间的最大失效载荷和线性固定刚度参数没有显著差异。在 45 度加载时，与 0 度相比，标本的最大失效载荷和线性刚度显著降低。在多循环加载时，在 0 度加载角度下，各组之间的残余位移没有显著差异，而在 45 度时，与断端螺钉固定或碎片固定系统相比，张力带固定的残余位移明显更高。
碎片固定系统的生物力学性能与断端螺钉固定相当，优于张力带钢丝技术。鉴于该系统提供断端间加压和简化经开放或闭合复位后骨折固定的优势，我们认为该碎片固定系统是横断髌骨骨折内固定的一种合适选择。
