Nicklin Sean, Ingram Scott, Gianoutsos Mark P, Walsh William R
Hand Unit, Sydney and Sydney Eye Hospital, Sydney, ,NSW, Australia.
J Hand Surg Am. 2008 Dec;33(10):1732-6. doi: 10.1016/j.jhsa.2008.07.010.
Lag screw fixation is reported to provide the most biomechanically stable construct for fixation of oblique or spiral metacarpal fractures. Lag screws are inserted after overdrilling the proximal cortex, resulting in compression at the fracture site. Minor drilling errors can result in poor screw purchase, instability, and ultimately impaired fracture healing. In an in vitro study, we compared construct stability provided by nonlagged and lagged screw fixation.
A cadaveric human metacarpal model was used. After removing the soft tissue, long oblique osteotomies were made in 24 metacarpals, which were then randomized to lagged or nonlagged fixation. Nonlagged fixation was performed through a newly introduced reduction system. Fixed specimens were subjected to biomechanical analysis by way of cantilevered bending to failure, and calculations were made for axial stress and normalized stiffness.
All specimens failed in a typical manner through the proximal screw site. Nonlagged compared with lagged screw fixation resulted in a higher axial stress and normalized stiffness, although the differences did not reach statistical significance.
Nonlagged screw fixation with use of a precompression device provided comparable fracture site stiffness and biomechanical stability without use of lag screws while removing the requirement for overdrilling, thus simplifying the technique.
据报道，拉力螺钉固定为斜形或螺旋形掌骨骨折固定提供了生物力学上最稳定的结构。拉力螺钉在近端皮质进行钻孔后置入，从而在骨折部位产生加压作用。微小的钻孔误差可能导致螺钉把持力不佳、固定不稳定，最终影响骨折愈合。在一项体外研究中，我们比较了非拉力螺钉固定和拉力螺钉固定所提供的结构稳定性。
使用尸体人掌骨模型。去除软组织后，在24根掌骨上制作长斜形截骨，然后随机分为拉力螺钉固定组或非拉力螺钉固定组。非拉力螺钉固定通过一种新引入的复位系统进行。对固定后的标本进行悬臂弯曲至破坏的生物力学分析，并计算轴向应力和标准化刚度。
所有标本均以典型方式在近端螺钉部位发生破坏。与拉力螺钉固定相比，非拉力螺钉固定导致更高的轴向应力和标准化刚度，尽管差异未达到统计学意义。
使用预加压装置的非拉力螺钉固定在不使用拉力螺钉的情况下提供了相当的骨折部位刚度和生物力学稳定性，同时消除了钻孔的要求，从而简化了技术。
