两种人钉方式固定兔胫骨平台骨折的早期生物力学研究

Biomechanical characteristics of fixations parallel to the plateau and vertical to the fracture line in the early management of fractures of tibial plateau in rabbits

目的观察平行关节面和垂直骨折线两种入钉方式固定对兔斜行劈裂的胫骨平台骨折术后的早期生物力学特性。方法30只13个月龄的新西兰大白兔，制作内侧胫骨平台斜行劈裂的骨折模型，用3枚2．0mm螺钉分平行关节面（平行组）和垂直骨折线（垂直组）两组进行固定，在术后即刻、1周、2周、4周、8周取材，检测两组内侧平台抗压缩的最大载荷、达到最大载荷时的功耗、关节面下陷2mm时的载荷与功耗。结果不同固定方式在相同时间点的生物力学比较显示：在固定即刻、术后1周和8周时两组间无统计学差异，在术后2周和4周时存在显著差异。同种固定方式不同时间点的生物力学比较显示：各检测指标术后早期下降，后逐渐恢复，在术后4周或8周时达到稳定状态。结论兔胫骨平台骨折术后稳定性先下降后逐渐恢复，平行组恢复较快；对于兔胫骨平台单纯斜形劈裂骨折，平行关节面固定能提供更稳定的生物力学特性。

Objective To evaluate the biomechanical characteristics of fixations parallel to the tibial plateau and vertical to the fracture line in the early management of fractures of tibial plateau in rabbits. Methods Models of oblique split fractures of the medial tibial plateau were created in 30 New Zealand rabbits of 13 months. One fibial plateau was fixed with 3 lag screws （2. 0 mm） parallel to the articular surface while the contralateral plateau was stabilized with 3 lag screws （2. 0 mm） vertical to the fracture line. The specimens were harvested at 0, 1, 2, 4, and 8 weeks after operation respectively and tested in a biomechanical testing machine. The maximum load of anti-compression at the medial tibial plateau and the maximum work at the maximum load, as well as the load and work as the articular surface displaced downwards for 2mm, were recorded. Results The biomechanical comparison of the 2 methods at the same time points showed that there were no significant differences at 0, 1 and 8 weeks but significant differences at 2 and 4 weeks. The biomechanical comparison of the same method at different time points showed that the biomechanical measures decreased at the early period after operation, then increased and finally kept steady at 4 or 8 weeks. Con- clusions The stability of tibial plateau fractures in rabbits decreases at the early post-operation and gradually increases to the normal level. It takes less time for the fixation parallel to the tibial plateau to increase the biomechanical stability to the normal level than the fixation vertical to the fracture line. The parallel fixation can provide more biomechanical advantage in stabilization of the fractures than the vertical one.