Barrey Cédric, Mosnier Thomas, Jund Jérôme, Perrin Gilles, Skalli Wafa
Department of Neurosurgery, Hôpital Neurologique P Wertheimer, Lyon, France.
J Neurosurg Spine. 2009 Nov;11(5):538-46. doi: 10.3171/2009.6.SPINE0949.
Few biomechanical in vitro studies have reported the effects of disc replacement on motion and kinematics of the cervical spine. The purpose of this study was to analyze motion through 3D load-displacement curves before and after implantation of a ball-and-socket cervical disc prosthesis with cranial geometric center; special focus was placed on coupled motion, which is a well-known aspect of normal cervical spine kinematics.
Six human cervical spines were studied. There were 3 male and 3 female cadaveric specimens (mean age at death 68.5 +/- 5 years [range 54-74 years]). The specimens were evaluated sequentially in 2 different conditions: first they were tested intact; then the spinal specimens were tested after implantation of a ball-and-socket cervical disc prosthesis, the Discocerv, at the C5-6 level. Pure moment loading was applied in flexion/extension, left and right axial rotation, and left and right lateral bending. All tests were performed under load control with a 3D measurement system.
No differences were found to be statistically significant after comparison of range of motion between intact and instrumented spines for all loading conditions. The mean range of motion for intact spines was 10.3 degrees in flexion/extension, 5.6 degrees in lateral bending, and 5.4 degrees in axial rotation; that for instrumented spines was 10.4, 5.2, and 4.8 degrees , respectively. No statistical difference was observed for the neutral zone nor stiffness between intact and instrumented spines. Finally, the coupled motions were also preserved during axial rotation and lateral bending, with no significant difference before and after implantation.
This study demonstrated that, under specific testing conditions, a ball-and-socket joint with cranial geometrical center can restore motion in the 3 planes after discectomy in the cervical spine while maintaining physiological coupled motions during axial rotation and lateral bending.
很少有体外生物力学研究报道椎间盘置换对颈椎运动和运动学的影响。本研究的目的是通过植入具有颅骨几何中心的球窝式颈椎间盘假体前后的三维载荷 - 位移曲线来分析运动；特别关注耦合运动，这是正常颈椎运动学中一个众所周知的方面。
研究了6个人类颈椎。有3个男性和3个女性尸体标本（平均死亡年龄68.5±5岁[范围54 - 74岁]）。标本在2种不同条件下依次进行评估：首先对其完整状态进行测试；然后在C5 - 6水平植入球窝式颈椎间盘假体Discocerv后对脊柱标本进行测试。在屈伸、左右轴向旋转和左右侧方弯曲时施加纯力矩载荷。所有测试均在负载控制下使用三维测量系统进行。
在所有加载条件下，完整脊柱和植入假体脊柱的运动范围比较后，未发现差异具有统计学意义。完整脊柱屈伸的平均运动范围为10.3度，侧方弯曲为5.6度，轴向旋转为5.4度；植入假体脊柱的相应值分别为10.4度、5.2度和4.8度。完整脊柱和植入假体脊柱在中性区和刚度方面未观察到统计学差异。最后，在轴向旋转和侧方弯曲过程中耦合运动也得以保留，植入前后无显著差异。
本研究表明，在特定测试条件下，具有颅骨几何中心的球窝关节在颈椎间盘切除术后可恢复三个平面的运动，同时在轴向旋转和侧方弯曲过程中保持生理耦合运动。
