锁定钢板和普通钢板置入老年复杂肱骨髁间骨折的生物力学比较

背景:伴有骨质疏松的肱骨髁间骨折采用普通钢板螺钉固定容易松动,而锁定钢板有良好的把持力及角稳定功能.目的:从生物力学角度比较锁定钢板和普通钢板治疗老年复杂肱骨髁间骨折的生物力学变化.方法:采用5具防腐老年尸体肱骨标本分为两组对干骺端进行骨密度测定.用电动摆锯从肱骨内外髁向鹰嘴窝成直角截割,制作C3型复杂肱骨髁间骨折模型,复位后分别用锁定钢板和普通钢板固定.两组在万能生物力学测力器上以600,800,1 000 N负荷进行轴向压力测试,2 N·m力矩进行扭转测试.结果与结论:两组标本干骺端平均骨密度差异无显著性意义(P > 0.05).锁定钢板组在600,800,1 000 N的负荷下出现的纵向压缩位移明显小于普通钢板组(P < 0.05).以3 mm为垂直位移系统失效标准,锁定钢板组的平均载荷显著大于普通钢板组(P < 0.05),锁定钢板组组旋转角度明显小于普通钢板组(P < 0.05).提示对于老年人复杂肱骨髁间骨折,锁定钢板比普通钢板有更强的抗折弯和抗扭转的生物力学性能.

Biomechanical comparison of locking plate and ordinary plate internal fixation for treatment of humeral intercondylar fractures of elderly patients

BACKGROUND: Humeral intercondylar fractures with osteoporosis are often fixed by ordinary plate and bolt which are likely to get loose. Locking plate has a good pullout strength and the function of angle stability. OBJECTIVE: To compare the biomechanical changes of locking plate and ordinary plate fixation for treatment of complex humeral intercondylar fractures of elderly patients. METHODS: The humerus specimens from five elderly formalined cadavers were divided into two groups for bone density measurement of the metaphysis. The humerus was cut by electric pendulum saw from inside and outside the condyle to the olecranon fossa at right angles in order to prepare the C3 type complex intercondylar fracture model of the humerus. The fractures were fixed with locking plate and ordinary plate respectively after reduction. The specimens of the two groups underwent axial pressure test under 600, 800, and 1 000 N load, as well as torsion test under 2 N·m using universal biomechanical ergograph. RESULTS AND CONCLUSION: The average bone mineral densities of the metaphysis in the two groups had not significant difference (P > 0.05). The vertical compressive displacements under 600, 800 and 1 000 N loads in the locking plate group were obviously reduced compared with the ordinary plate group (P > 0.05). The average load of the locking plate group was obviously bigger than the ordinary plate group (P > 0.05), and the rotation angle was obviously smaller (P < 0.05) according to the failure standard of 3 mm for vertical displacement system. It is indicated that the locking plate has stronger biomechanical properties of anti-bend and anti-torsion than the ordinary plate for treatment of complex humeral intercondylar fractures of elderly patients.