Sengupta Dilip K, Fan Haibo
From the Department of Orthopedics, Dartmouth-Hitchcock Medical Center, Lebanon, NH.
Spine (Phila Pa 1976). 2014 Jun 1;39(13):1032-43. doi: 10.1097/BRS.0000000000000292.
A biomechanical study in cadaveric lumbar spine.
To establish the basis of mechanical stability in degenerative disc disease from the relationship between range of motion (ROM), neutral zone motion (NZ), intradiscal pressure profile, and instantaneous axis or rotation (IAR) in advancing grades of disc degeneration.
The basis of mechanical instability in lumbar disc degeneration remains poorly understood. Controversy exists between abnormal motion and abnormal loading theories.
Thirty-nine lumbar motion segments were graded for staging of disc degeneration with magnetic resonance scan. These specimens were tested for ROM and NZ in a 6 df spine simulator, with 7.5 N·m unconstrained, cyclical loading. Continuous tracking of IAR was derived from ROM data. Intradiscal pressure profiles were determined using needle-mounted pressure transducer, drawn across the disc space under constant loading.
The ROM showed insignificant change, but a trend of increase from grade I through III and a decrease with advanced degeneration. NZ increased significantly with advancing disc degeneration. Intradiscal pressure profile showed an even distribution of the load in normal discs but a depressurized nucleus and irregular spikes of excessive loading, with advancing degeneration. The IAR showed a smooth excursion in normal versus irregular jerky excursion in degenerated discs, without significant change in excursion. The center of rotation, derived from IAR, showed significantly increased vertical translation with advancing degeneration, indicating an abnormal quality of motion.
The study established a basis of mechanical instability in the lumbar spine with advancing disc degeneration as an abnormal quality of motion represented by variation in IAR and center of rotation, increased NZ motion without any increase in quantity of motion, and abnormal load distribution across the disc space with spikes of high load amidst depressurized nucleus. The study cannot identify clinical instability but finds an association between the abnormal motions and the abnormal load distribution in mechanical instability.
N/A.
一项关于尸体腰椎的生物力学研究。
通过在椎间盘退变进展过程中，研究活动范围（ROM）、中性区运动（NZ）、椎间盘内压力分布以及瞬时旋转轴（IAR）之间的关系，建立退行性椎间盘疾病机械稳定性的基础。
腰椎间盘退变中机械性不稳定的基础仍知之甚少。异常运动理论和异常负荷理论之间存在争议。
通过磁共振扫描对39个腰椎运动节段进行椎间盘退变分级。这些标本在6自由度脊柱模拟器中进行ROM和NZ测试，施加7.5 N·m无约束循环负荷。通过ROM数据连续追踪IAR。使用针式压力传感器确定椎间盘内压力分布，在恒定负荷下穿过椎间盘间隙绘制。
ROM显示无显著变化，但从I级到III级有增加趋势，而在严重退变时则下降。随着椎间盘退变进展，NZ显著增加。椎间盘内压力分布显示，正常椎间盘负荷分布均匀，但随着退变进展，髓核减压且出现过度负荷的不规则尖峰。IAR在正常椎间盘显示平稳偏移，而在退变椎间盘中显示不规则的急促偏移，偏移量无显著变化。从IAR得出的旋转中心显示，随着退变进展垂直平移显著增加，表明运动质量异常。
本研究建立了腰椎随着椎间盘退变进展而出现机械性不稳定的基础，其表现为IAR和旋转中心变化所代表的异常运动质量、NZ运动增加而运动总量未增加以及椎间盘间隙异常负荷分布，即髓核减压中有高负荷尖峰。本研究无法确定临床不稳定，但发现了异常运动与机械性不稳定中异常负荷分布之间的关联。
无。
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