肱骨近端骨折经皮穿针固定的生物力学研究

Biomechanical study of percutaneous pinning as the treatment of proximal humerus fractures

目的 通过生物力学实验研究探讨应用经皮穿针固定治疗肱骨近端骨折时固定针构型对骨折稳定性的影响 ,探讨临床工作中如何进一步改善骨折固定的生物力学稳定性。方法 将 18对36根新鲜冷冻成人肱骨干标本配对分为 4小组 ,实验前对所有肱骨干标本进行双能骨密度检查以排除骨质情况对实验结果的影响。按统一标准制作肱骨近端 2部分外科颈骨折模型 ,之后使用 4根直径 2 5mm螺纹针对 2个小组进行统一方式的平行构型固定 ,对另外 2小组进行统一方式的扇形交汇构型固定。应用Instron5 5 6 6生物力学试验机对尸体标本进行生物力学测定 ,对比两种构型的抗剪切应力强度与抗扭转应力强度。结果 在抗剪切应力方面两种固定构型没有明显的区别 (P =0 73) ,而在抗扭转应力方面平行构型固定则明显优于扇形交汇构型固定 (P =0 0 4 )。结论 通过生物力学实验的结果 ,我们认为在条件允许的情况下尽可能使用平行构型的方式穿针固定 ,若无法进行平行的固定或不能保证平行固定针之间的距离在 1cm以上时 。

Objective To investigate the influence on fracture stability by different pin construct during percutaneous pinning for the treatment of proximal humerus fractures Methods Eighteen pairs(36) adult fresh frozen humeri were match paired and divided into 4 groups Dual energy bone density scan had been used in order to rule out the influence by different degrees of osteoporosis of the cadaver Two part surgical neck fracture model was carried out unanimously in all 36 humeri Four terminal threaded pins (2 5 mm in diameter) were used in fixation for all specimen Parallel type pinning(box type) were carried out in 2 groups and convergent type pinning(fan shape) in the other 2 groups Instron5566 biomechanical tester was applied in determining both anti shear and anti torsion ultimate load of each specimen Results There was no statistical difference between parallel pin construct and convergent construct in regard of anti shear resistance ( P =0 73) But by mean of anti torsion resistance,the parallel construct had significant advantage over the convergent construct( P =0.04) Conclusion According to our biomechanical data,parallel pin construct seems to have better torsional stability We suggest that parallel pin fixation should be applied whenever possible Convergent pin construct should be considered when parallel construct is not possible or the distance between pins are too small(<1 cm)