Stirma Guilherme Augusto, Ribeiro Leandro Massini, Gaio Evandro Dias, Belangero Paulo Santoro, Antonio de Figueiredo Eduardo, de Castro Pochini Alberto, Andreoli Carlos Vicente, Ejnisman Benno
Federal University of São Paulo, Paulista School of Medicine - UNIFESP, São Paulo (SP), Brazil.
Federal University of Juiz de Fora, Minas Gerais, Brazil.
JSES Int. 2022 Jun 11;6(5):748-754. doi: 10.1016/j.jseint.2022.05.008. eCollection 2022 Sep.
Multiple problems and complications associated with Latarjet fixation have been described; thus, this is the first study in the literature to identify the maximum allowed screw clamping force and best fixation screw position for Latarjet surgery.
A variation of distal and proximal coracoid screw positions with and without a flat washer was evaluated through finite element analysis, at a minimum distance of 3 mm from the edge. A loading progression test was performed until the maximum stress reached a limit imposed by the bone yield. We identified the maximum allowed screw clamping force based on a von Mises and maximum principal stresses failure theory.
When using the flat washer, the cortical bone generally has only space for 1 piece. For this reason, as a primary study, it was observed that when the distal screw was more than 7 mm from the edge, the clamping force supported will be higher than that during the proximal fixation regardless of the proximal location screw. We have found that the best position is 7 mm from the distal edge, with the highest compression of 445 N (7 mm proximal distance, 5 mm distal distance) in due respect to the von Mises failure theory. To get around this lack of space situation, in this study, we have proposed a fixation plate to replace the flat washer. This plate has shown very interesting values when compared to the previously flat washer study, but now, for both screw holes. With those results, we can assure that using a fixation plate like this will ensure surgery safety and higher allowed compression force when clamping the bolts.
The distal screw provided higher tensile strength values when located more than 7 mm from the coracoid edge. The geometry of the coracoid in its distal position supports higher stress loads than in the proximal position. When the flat washer was in the proximal position, the coracoid was submitted with a more distributed and uniform load, preventing localized bone damage as a crush.
已描述了与Latarjet固定相关的多种问题和并发症；因此，本研究是文献中首次确定Latarjet手术允许的最大螺钉夹紧力和最佳固定螺钉位置的研究。
通过有限元分析评估了有无平垫圈时喙突远端和近端螺钉位置的变化，距边缘的最小距离为3mm。进行加载进程测试，直至最大应力达到骨屈服所施加的极限。我们基于冯·米塞斯和最大主应力失效理论确定了允许的最大螺钉夹紧力。
使用平垫圈时，皮质骨通常仅能容纳1枚螺钉。因此，作为初步研究观察到，当远端螺钉距边缘超过7mm时，无论近端螺钉位置如何，其支撑的夹紧力均高于近端固定时的夹紧力。我们发现最佳位置是距远端边缘7mm，根据冯·米塞斯失效理论，此时最大压缩力为445N（近端距离7mm，远端距离5mm）。为解决这种空间不足的情况，在本研究中，我们提出了一种固定板来替代平垫圈。与之前的平垫圈研究相比，该固定板在两个螺钉孔处均显示出非常有趣的值。基于这些结果，我们可以确保使用这样的固定板将确保手术安全，并在夹紧螺栓时允许更高的压缩力。
当远端螺钉距喙突边缘超过7mm时，其提供更高的拉伸强度值。喙突远端位置的几何形状比近端位置能承受更高的应力负荷。当平垫圈位于近端位置时，喙突承受的载荷分布更均匀，可防止局部骨损伤如挤压伤。
