后路板-棒内固定系统治疗不稳定性寰椎骨折的生物力学研究

Biomechanical study of posterior plate-rod system for instable atlas fractures

中文关键词:  寰椎骨折  后路内固定系统  三维运动范围  生物力学

英文关键词:Atlas fracture  Posterior fixation system  Range of motion  Biomechanics

中文摘要:

  【摘要】 目的：测试后路板-棒内固定系统治疗不稳定寰椎骨折的稳定性，为临床使用提供理论基础。方法：采集新鲜成年人尸体颈椎骨（C0~C3）标本6具，用聚甲基丙烯酸甲酯（PMMA）上下包埋，在生物力学实验机上，以150N为最大生理载荷，最大力矩为1.50N·m，依次测量完整模型组（A组）、骨折模型组（B组，包括寰椎后弓两处骨折与典型Jefferson骨折，分别作为B1组和B2组，骨折模型制作时保持横韧带完整）、内固定模型组（C组，包括B1组+内固定系统、B2组+内固定系统，分别作为C1组、C2组）C0-C1、C1-C2节段前屈/后伸、左/右侧屈和左/右旋转等6个方向的三维运动范围（ROM），通过比较，评价后路板-棒内固定系统治疗寰椎骨折的生物力学稳定性。根据测量所得ROM值，设A组各方向三维运动稳定性指数（Sf）为100%，计算B组、C组模型各运动方向Sf，进一步直观比较各模型的稳定性变化。结果：C0-C1节段，A组前屈/后伸、左右侧屈、左右轴向旋转方向的ROM分别为11.06°±1.00°，7.08°±0.62°，13.24°±1.24°；B1、B2组前屈/后伸、左右侧屈、左右轴向旋转方向ROM均较A组明显增大（P<0.05）；C1组前屈/后伸、左右侧屈、左右旋转方向的ROM均较B1组明显减小（P<0.05）；C2组各方向ROM均较B2组明显减小（P<0.05）；C1、C2组前屈/后伸、左右侧屈、左右轴向旋转方向ROM与A组比较均无统计学差异（P>0.05）。C1-C2节段，A组前屈/后伸、左右侧屈、左右轴向旋转方向的ROM分别为10.07°±1.12°，5.56°±0.54°，20.83°±2.12°；B1、B2组各方向ROM均较A组明显增大（P<0.05）；C1组各方向的ROM较B1组明显减小（P<0.05）；C2组各方向ROM较B2组明显减小（P<0.05）；C1、C2组各方向ROM与A组比较均无统计学差异（P>0.05）。C0-C1节段，B1组前屈/后伸、左/右侧屈、左/右轴向旋转方向Sf 分别为71%、70%、64%，B2组各方向Sf 分别为61%、55%、58%，C1组各方向Sf 分别为102%、108%、108%，C2组各方向Sf 分别为91%、91%、92%。C1-C2节段，B1组前屈/后伸、左/右侧屈、左/右轴向旋转方向Sf 分别为70%、61%、35%，B2组各方向Sf 分别为59%、54%、37%，C1组各方向Sf 分别为105%、111%、106%，C2组各方向Sf分别为91%、90%、92%。结论：寰椎后路板-棒内固定系统既能恢复上颈椎稳定性，又可保留其生理运动功能。使用该系统治疗寰椎后弓两处骨折，在稳定性方面效果稍优于典型Jefferson骨折。

英文摘要:

  【Abstract】 Objectives: To test the stability of atlas fracture fixed with posterior plate-rod system, and to provide the rationale for its clinical use. Methods: Six fresh human cadaveric upper cervical spine specimens(C0-C3) were harvested and embedded in polymethyl methacrylate(PMMA). Three dimentional movements including extension, flexion, left and right lateral bending, left and right axial rotation were tested on the mechanical testing machine. The movements were measured by range of motions(ROM). The C0-C1 and C1-C2 segments of specimens were distributed and tested in these status: the intact specimens(group A), the specimens with atlas fractures(group B, including the posterior arch fracture as subgroup B1 and Jefferson fracture as subgroup B2) and the specimens of group B with the posterior plate-rod system placement(group C). Then the three dimensional motion stability index(Sf) of group A was defined as 100% in the six types of motions. The Sf of group B and group C was calculated, also in six motions to compare the stability among different specimens. Results: Level of C0-C1: the ROM of group A of six movements was 11.06°±1.00°(extension, flexion), 7.08°±0.62°(left and right lateral bending), 13.24°±1.24°(left and right axial rotation) respectively. ROM of group B(including B1 and B2) increased significantly compared with that of group A(P<0.05). ROM of group C1 decreased significantly compared with that of group B1 in all movements(P<0.05). And the meaningful decrease could be seen between group C2 and B2(P<0.05). ROM of group C1 decreased compared with that of group A, but it was not significant(P>0.05). ROM of C2 increased insignificantly compared with that of group A(P>0.05). Level of C1-C2: the ROM of group A of six movements was 10.07°±1.12°(extension, /flexion), 5.56°±0.54°(left and right lateral bending), 20.8°±32.12°(left and right axial rotation) respectively. ROM of group B1 and B2 increased significantly compared with that of group A(P<0.05). ROM of group C1 decreased compared with that of group B1(P<0.05). When compared with group B2 in all the movements, ROM of group C2 decreased significantly(P<0.05). ROM of C1 decreased insignificantly compared with that of group A(P>0.05). ROM of C2 increased compared with that of group A, but the increase was not significant(P>0.05). In level of C0-C1, the Sf of group B1 was 71%(extension, /flexion), 70%(left and right lateral bending), 64%(left and right axial rotation) respectively. The Sf of group B2 was 61%(extension, /flexion), 55%(left and right lateral bending), 58%(left and right axial rotation). The Sf of group C1 of the movements was respectively 102%, 108%, 108%. The Sf of group C2 was respective 91%, 90%, 92%. Conclusions: After placing posterior plate-rod system, the stability of fractured atlas recovers. Moreover, the flexibility of the atlas is maintained, which has better outcome for Levine Ⅰ atlas fracture than Jefferson fracture.