Ma Jiawen, Wang Tian, Lovric Vedran, Johnson Kenneth A, Walsh William R
Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, 2006, Australia.
Surgical and Orthopaedic Research Laboratories (SORL), Prince of Wales Hospital, University of New South Wales, Sydney, Australia.
BMC Vet Res. 2017 Oct 25;13(1):306. doi: 10.1186/s12917-017-1225-y.
The physis is the weakest component of immature long bones, and physeal fractures constitute about 30% of fractures in growing dogs. Fractures of the proximal humeral physis typically have a Salter Harris type I or II configuration. These fractures require accurate reduction and adequate stabilization to allow for any potential continued longitudinal bone growth, in conjunction with physeal fracture healing. Conventional internal fixation of these fractures involves insertion of two parallel Kirschner wires, although other methods described include tension band wiring, Rush pinning, and lag screws. However these recommendations are based on anecdotal evidence, and information about the biomechanical stability of physeal fracture repair is sparse. The unique anatomical structure of the epiphyseal-metaphyseal complex makes the gripping of the epiphysis for ex vivo biomechanical testing of physeal fracture repair very challenging. The objective of our study was to biomechanically assess the optimal number (three, two or one) of implanted Kirschner wires in a porcine Salter Harris I proximal humeral physeal fracture model, using motion analysis tracking of peri-fragmental retro-reflective markers while constructs were subjected to a constant axial compression and a sinusoidal torque of +/- 2 Nm at 0.5 Hz for 250 cycles.
There were significant differences between the three constructs (three, two or one Kirschner wire repair) for gross angular displacement (p < 0.001). The difference between three pins and two pins on toggle was not significant (p = 0.053), but both three-pin and two-pin fixation significantly reduced rotational toggle compared to one-pin fixation. Construct stiffness was not significantly different between any of the pin groups (p > 0.33).
Motion analysis tracking using peri-fragmental markers in this porcine model of physeal fracture repair found that the stability at the fracture site of one-pin fixation was significantly less than two-pin and three-pin fixation. Whether there was increased stabilization of these fractures with three-pin fixation compared to two-pin fixation was not conclusive in this porcine model.
生长板是未成熟长骨中最薄弱的部分，生长板骨折约占生长犬骨折的30%。肱骨近端生长板骨折通常为Salter Harris I型或II型。这些骨折需要精确复位和充分固定，以允许任何潜在的持续纵向骨生长，并促进生长板骨折愈合。这些骨折的传统内固定方法是插入两根平行的克氏针，不过其他描述的方法包括张力带钢丝固定、Rush针固定和拉力螺钉固定。然而，这些建议是基于轶事证据，关于生长板骨折修复生物力学稳定性的信息很少。骨骺-干骺端复合体独特的解剖结构使得在体外对生长板骨折修复进行生物力学测试时，抓住骨骺非常具有挑战性。我们研究的目的是在猪的Salter Harris I型肱骨近端生长板骨折模型中，使用碎片周围反光标记的运动分析跟踪，对植入的克氏针的最佳数量（三根、两根或一根）进行生物力学评估，同时在结构上施加恒定轴向压缩和0.5Hz下±2 Nm的正弦扭矩，持续250个周期。
三种结构（三根、两根或一根克氏针修复）在总角位移方面存在显著差异（p < 0.001）。三根针和两根针在摆动方面的差异不显著（p = 0.053），但与一根针固定相比，三根针和两根针固定均显著降低了旋转摆动。任何针组之间的结构刚度均无显著差异（p > 0.33）。
在这个猪的生长板骨折修复模型中，使用碎片周围标记进行运动分析跟踪发现，一根针固定的骨折部位稳定性明显低于两根针和三根针固定。在这个猪模型中，与两根针固定相比，三根针固定是否能增加这些骨折的稳定性尚无定论。
