肱骨干骨折髓内外固定的生物力学研究

目的 通过对单一加压钢板螺钉加髓内针、交锁髓内钉和微创技术简单有限内固定加单臂外支架3种不同固定方法治疗肱骨干复杂骨折的生物力学性能进行对比研究,为临床应用提供可靠的生物力学依据.方法 取自愿捐赠的18个新鲜湿润肱骨标本,制备肱骨干复杂骨折模型,根据不同固定方式随机分为3组,每组6个.钢板组:采用单一加压钢板螺钉加髓内针固定;髓内钉组:采用交锁髓内钉固定;外支架组:采用微创技术简单有限内固定加单臂外支架固定.分别进行轴向压缩实验和水平扭转实验.结果 轴向压缩实验:各组载荷-位移曲线呈线性到非线性变化.钢板组及髓内钉组最大载荷值分别为(6162.09±521.06)N和(6738.32±525.89)N,两组比较差异无统计学意义(P>0.05);外支架组最大载荷值为(2753.57±185.59)N,与其余两组比较,差异均有统计学意义(P<0.05).钢板组及外支架组刚度值分别为(171.69±6.49)N/mm和(132.59±2.93)N/mm,两组比较差异无统计学意义(P>0.05);髓内钉组的刚度值为(333.04±36.85)N/mm,与其余两组比较差异有统计学意义(P<0.05).水平扭转实验:各组扭矩-扭角曲线呈线性到非线性变化.髓内钉组和外支架组的最大扭矩分别为(17.12±5.73)Nm和(20.26±6.42)Nm,两组比较差异无统计学意义(P>0.05);钢板组的最大扭矩为(38.24±7.08)Nm,与其余两组比较差异有统计学意义(P<0.05).钢板组及外支架组刚度值分别为(16.36±2.07)Ncm/°和(18.79±2.62)Ncm/°,差异无统计学意义(P>0.05);髓内钉组的刚度值为(11.45±0.22)Ncm/°,与其余两组比较差异有统计学意义(P<0.05).结论 钢板组压缩和扭转强度均较强,旋转刚度较强而压缩刚度较弱;髓内钉组压缩强度和压缩刚度较强,而扭转强度和扭转刚度较弱;外支架组仅在扭转刚度上与钢板组相当,而在其他3项指标上均较弱.

A BIOMECHANICAL STUDY ON INTERNAL AND EXTERNAL FIXATION DEVICES FOR TREATMENT OFHUMERAL SHAFT FRACTURE

OBJECTIVE: To provide the scientific theoretical basis for clinical practice by comparing biomechanical characteristics of single compressed plate with intramedullary pin, locking intramedullary nail and simple arm external fixator with simple internal fixation devices. METHODS: Eighteen wet humeral bone specimens of adult cadaver were made complicated fracture models of humeral shaft and divided into 3 groups according to fixation methods. Fracture was fixed by single compressed plate with intramedullary pin in plate group, by locking intramedullary nail in intramedullary nail group and by external fixator with simple internal fixation devices in external fixator group. The intensity and rigidity of complicated fracture models of humeral shaft was measured in compress test and torsion test. RESULTS: In compress test, the maximum load in plate group (6,162.09 +/- 521.06) N and in intramedullary nail group (6,738.32 +/- 525.89) N was significantly larger than that in external fixator group (2,753.57 +/- 185.59) N (P < 0.05); but there was no significant difference between plate group and intramedullary nail group (P > 0.05). Under 600 N physiological compress load, the rigidity was (171.69 +/- 6.49) N/mm in plate group, (333.04 +/- 36.85) N/mm in intramedullary nail group and (132.59 +/- 2.93) N/mm in external fixator group; showing no significant difference between plate group and external fixator group (P > 0.05), and showing significant difference between intramedullary nail group and plate, external fixator groups (P < 0.05). In torsion test, the maximum torque in plate group (38.24 +/- 7.08) Nm was significantly larger than those in intramedullary nail group (17.12 +/- 5.73) Nm and external fixator group (20.26 +/- 6.42) Nm (P < 0.05), but there was no significant difference between intramedullary nail group and external fixator group (P > 0.05). Under 0.80 Nm physiological torque, the rigidity was (16.36 +/- 2.07) Ncm/degree in plate group and (18.79 +/- 2.62) Ncm/degree in external fixator group, which was significantly larger than that in intramedullary nail group (11.45 +/- 0.22) Ncm/degree (P < 0.05); but there was no significant difference between plate group and external fixator group (P > 0.05). CONCLUSION: Those fracture models fixed by single compressed plate with intramedullary pin have better compress and torsion intensity, they also have better torsion rigidity but less compress rigidity. Those fracture models fixed by locking intramedullary nail have better compress intensity but less torsion intensity, they also have better compress rigidity but less torsion rigidity. Those fracture models fixed by external fixator with simple internal fixation device have less compress and torsion intensity, they also have less compress rigidity but better torsion rigidity.