一种用于腰椎峡部裂的轴向可控加压脊柱棒的研制及生物力学研究

A biomechanical study of a self-designed axially controlled compression spinal rod for lumbar spondylolysis

目的探讨自主研发的用于腰椎峡部裂(LS)的轴向可控加压脊柱棒(ACCSR)和普通脊柱棒(CSR)的生物力学性能差异。方法选取同一批次生产且直径均为6.0 mm的ACCSR和CSR各36根。实验分为ACCSR组和CSR组,分别进行单棒及钉-棒内固定系统的生物力学测试。单棒测试:四点折弯试验(n=7)计算出两组的刚度和屈服载荷并进行比较;单棒疲劳试验(n=8)通过2500000次循环加载,记录成功时的加载压缩载荷,与正常成人单侧腰椎峡部的受力(198.72 N)进行比较。钉-棒内固定系统测试:轴推试验(n=7)测试两组的轴向夹持能力,轴扭试验(n=7)测试两组的扭转夹持能力,椎弓根螺钉侧压试验(n=7)测试螺钉的刚度及屈服载荷。结果ACCSR组的刚度(1543.37±61.41)N/mm、屈服载荷1338.57(1282.00,1353.80)N显著小于CSR组的(3797.63±156.15)N/mm、4059.95(3813.80,4090.89)N,差异均有统计学意义(P<0.05);单棒疲劳试验中CSR和ACCSR通过2500000次疲劳试验的压缩载荷分别为640.00 N和320.00 N,均大于正常成人单侧腰椎峡部的最大受力(198.72 N)。ACCSR组和CSR组的轴向夹持能力、扭转夹持能力,以及两组螺钉的刚度、屈服载荷比较差异均无统计学意义(P>0.05)。结论在LS的固定中,ACCSR的刚度、屈服载荷及抗疲劳性能不如CSR,但两组钉-棒内固定系统的生物力学性能相当且ACCSR组的抗疲劳性能能达到正常人峡部的应力需求。

ObjectiveTo compare the mechanical properties between our self-designed axially controlled compression spinal rod(ACCSR)and conventional spinal rod(CSR)for lumbar spondylolysis(LS).MethodsThis study selected 36 ACCSRs(the ACCSR group)and 36 CSRs(the CSR group),both of which were in a diameter of 6.0 mm and manufactured in the same batch.They were subjected respectively to biomechanical tests of spinal rod and pedicle screw-rod internal fixation system.In spinal rod tests:the stiffness and yield load of the spinal rods were calculated using four-point bending tests(n=7)and comparisons were made between the 2 groups;spinal rod fatigue tests(n=8)recorded the successful compression loads after 2.5 million cycles of loading and compared them with the maximum force at the isthmus of a normal adult's unilateral lumbar spine(198.72 N).In tests of the pedicle screw-rod internal fixation system,the axial compression tests(n=7)measured the axial gripping capacity,the axial torsion tests(n=7)the torsional gripping capacity,and the lateral compression tests(n=7)the stiffness and yield load of pedicle screws in the 2 groups respectively.ResultsThe stiffness[(1,543.37±61.41)N/mm]and yield load[1,338.57(1,282.00,1,353.80)N]of ACCSR group were significantly smaller than those of CSR group[(3,797.63±156.15)N/mm and 4,059.95(3,813.80,4,090.89)N](P<0.05).The spinal rod fatigue tests showed that the respective loads of CSR and ACCSR passing the 2.5 million fatigue tests were 640.00 N and 320.00 N,both larger than the maximum force at the unilateral lumbar isthmus of a normal adult(198.72 N).There were no significant differences between the ACCSR group and the CSR group in the axial gripping capacity and torsional gripping capacity,as well as in stiffness and yield load of screws between the 2 groups(P>0.05).ConclusionsIn fixation of LS,although the yield load,stiffness and fatigue resistance of ACCSR are inferior to those of CSR,the biomechanical properties of the two sets of pedicle screw-rod internal fixation system are comparable.The fatigue resistance of ACCSR can meet the stress requirements of the normal human isthmus.