Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo, São Paulo, Brazil.
Res Vet Sci. 2024 Oct;178:105378. doi: 10.1016/j.rvsc.2024.105378. Epub 2024 Aug 8.
The implantation of unicortical cortex screws in the proximal hole of locking compression plates (LCP) has been recommended for proximal interphalangeal (PIP) arthrodesis in horses to prevent fractures resulting from stress risers in the proximal phalanx (P1). However, this cortex screw fixation technique may limit efficient dorsal compression of the PIP joint by the plate, potentially affecting the stability of the construct. In this study, we aimed to measure stress and strain in P1 and the plate using an ex vivo model of PIP arthrodesis in horses. We employed various implantation methods and proximal screw types in conjunction with two 5.5 mm transarticular cortex screws. Ten pairs of equine forelimbs were divided into four groups based on proximal screw placement: GUC (unicortically placed cortex screw), GBC (bicortically placed cortex screw), GUL (unicortically placed locking screw), and GBL (bicortically placed locking screw). We calculated the magnitude and direction of strain, strain ratio, and stress using strain gauges during an axial compression mechanical testing. The palmar surface of P1 exhibited higher stress and strains than the dorsal surface, with the plate part located at the articular level suffered more stress than the proximal part. Both the implantation method and proximal screw type significantly influenced the analyzed parameters. The GUC promoted greater changes in strain direction in the proximal portion of the P1. Bicortical placement of a cortex screw appears to be the most suitable option for filling the proximal hole of the LCP, because it allows effective dynamic compression via the plate and prevents abrupt shifts in the direction of the forces acting on the proximal part of P1 during loading.
在马的近指间（PIP）关节融合术中，建议将皮质骨螺钉植入锁定加压板（LCP）的近端孔中，以防止在近节指骨（P1）中出现应力集中导致的骨折。然而，这种皮质骨螺钉固定技术可能会限制钢板对 PIP 关节的有效背侧加压，从而影响结构的稳定性。在这项研究中，我们旨在使用马的 PIP 关节融合的离体模型来测量 P1 和钢板的应力和应变。我们结合使用了两种 5.5mm 经关节皮质骨螺钉，采用了各种植入方法和近端螺钉类型。根据近端螺钉的位置，将 10 对马前肢分为四组：GUC（皮质骨螺钉单皮质植入）、GBC（皮质骨螺钉双皮质植入）、GUL（锁定螺钉单皮质植入）和 GBL（锁定螺钉双皮质植入）。我们在轴向压缩机械测试中使用应变计计算了应变、应变比和应力的大小和方向。P1 的掌侧表面比背侧表面表现出更高的应力和应变，关节水平的钢板部分比近端部分承受更大的应力。植入方法和近端螺钉类型都显著影响了分析参数。GUC 促进了 P1 近端应变方向的更大变化。皮质骨螺钉的双皮质植入似乎是填充 LCP 近端孔的最佳选择，因为它允许通过钢板进行有效的动态压缩，并防止在加载过程中 P1 近端部分上的力的方向发生突然变化。
