Johannessen Wade, Cloyd Jordan M, O'Connell Grace D, Vresilovic Edward J, Elliott Dawn M
Department of Orthopaedic Surgery, McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA 19104-6081, USA.
Ann Biomed Eng. 2006 Apr;34(4):687-96. doi: 10.1007/s10439-005-9070-8. Epub 2006 Feb 16.
Knowledge of the functional role of the nucleus pulposus is critical for the development and evaluation of disc treatment strategies to restore mechanical function. While previous motion segment studies have shown that nucleotomy alters disc mechanics, disruption of the annulus fibrosus may have influenced these experiments. The objective of this study was to determine the mechanical role of the nucleus pulposus in support of axial loads via a trans-endplate nucleotomy procedure. Sheep motion segments were randomly assigned to three groups: control, limited nucleotomy, and radical nucleotomy. Mechanical testing consisted of 20 cycles of compression-tension, a 1-h creep, and a slow constant-rate compressive ramp test. Nucleotomy led to increased axial deformations, in particular an elongated neutral zone, a greater range of motion, and altered creep behavior. In general, the elastic properties exhibited a graded response with respect to the amount of nucleus material removed. This graded effect can be attributed to swelling of the nucleus pulposus in the limited nucleotomy group, whereas little swelling was observed in the radical group. The findings of the present study indicate that functional evaluation of nucleus pulposus replacements and disc implants should include range of motion measures (including neutral zone) and viscoelastic creep experiments in addition to considering compressive stiffness.
了解髓核的功能作用对于恢复机械功能的椎间盘治疗策略的开发和评估至关重要。虽然先前的运动节段研究表明髓核摘除术会改变椎间盘力学，但纤维环破裂可能影响了这些实验。本研究的目的是通过经终板髓核摘除术确定髓核在支持轴向载荷中的力学作用。将绵羊运动节段随机分为三组：对照组、有限髓核摘除组和根治性髓核摘除组。力学测试包括20个压缩-拉伸循环、1小时蠕变和缓慢恒速压缩斜坡试验。髓核摘除导致轴向变形增加，特别是中性区延长、运动范围增大和蠕变行为改变。一般来说，弹性特性随着去除的髓核物质数量呈现分级反应。这种分级效应可归因于有限髓核摘除组中髓核的肿胀，而在根治性组中几乎未观察到肿胀。本研究结果表明，除了考虑压缩刚度外，对髓核置换物和椎间盘植入物的功能评估还应包括运动范围测量（包括中性区）和粘弹性蠕变实验。
