中空锥槽椎弓根钉联合PMMA强化治疗胸腰椎压缩骨折的生物力学评价

Biomechanical evaluation of hollow pedicle screw strengthened with PMMA for treatment of thoracolumbar vertebral compression fracture

目的探讨中空锥槽椎弓根钉联合PMMA强化治疗胸腰椎压缩骨折的生物力学性能。方法采集新鲜胸腰椎标本10具(28椎),分成4组,行生物力学分析,分别测定各组的强度和刚度、螺钉最大拔出力、位移、折弯力和抗屈曲、疲劳强度等力学指标。结果中空锥槽椎弓根钉联合PMMA强化组最大拔出力为(1 758.4±184.6)N,高于其他3组,差异有统计学意义(P<0.05)。向中空锥槽椎弓根钉中空部分注入PMMA,未见椎弓根外或椎管内有PMMA溢出。周期抗屈曲实验中,添加PMMA可使中空锥槽椎弓根钉耐受更大的负荷或在同等负荷下仅发生较小的位移。中空锥槽椎弓根钉和一般椎弓根钉最大折弯力及抗疲劳强度比较两者差异无统计学意义(P>0.05)。结论中空锥槽椎弓根钉的力学性能与一般椎弓根钉相似,并能减少PMMA向椎弓根外或椎管内溢出;联合PMMA强化其生物力学性能较其他各种方法更为优越,适用于老年胸腰椎骨质疏松性压缩骨折。

Objective To investigate the biomechanical performance of hollow pedicle screw strengthened with PMMA for treatment of thoracolumbar compression fractures. Methods Ten fresh thoracolumbar specimens（28 vertebrae） were collected.All samples were under the biomechanical tests, such as the axial stiffness, the largest output of screw, displacement, bending strength and buckling, fatigue strength. Results The largest pull strength of hollow pedicle screw strengthened with PMMA group was（1 758.4±184.6）N, higher than the other three groups（P〈 0.05）. PMMA was infused into the hollow, no PMMA overflow was observed. In periodic buckling experiments, PMMA made hollow screw tolerance larger load or smaller displacement under the same load. In the maximum bending force and the fatigue strength of hollow pedicle screw and regular pedicle screw there were no significant difference（P〉 0.05）. Conclusion The mechanical properties are similar between hollow pedicle screw with regular pedicle screw. The hollow pedicle screw can reduce PMMA overflow and increase the stability of pedicle screw. The biomechanical performance of hollow pedicle screw strengthened with PMMA is better than other pedicle screws,and it is suitable for treatment of elderly patient with thoracolumbar vertebral compression fracture.