Three-dimensional analysis on the biomechanical instability of the human lumbar spine. - Experimental and clinical investigation

[导言]腰椎不稳在实验和临床研究中还没有明确的定义。Panjabi首先将中性区域(NZ)描述为脊柱不稳定的指标。本研究采用循序渐进的方法去除腰椎交界处的各部分，并测量这些不稳定状态下的三维运动，以研究以新西兰为重点的生物力学不稳定指标，并研究各部分的生物力学作用。[方法]选用10具自然腰椎前凸和腰椎倾斜的新鲜身体标本。对试件顶端施加六个纯力矩：前屈、后伸、双侧轴向旋转和侧弯，得到载荷-位移曲线，包括中性区(NZ)、弹性区(EZ)和活动范围(ROM)三个参数。实验在以下条件下重复：(A)完整标本，(B)后韧带和小关节囊切断，(C)椎间盘损伤，(D)双侧小关节切除。本文对数据进行了分析。[结果]在连续的腰椎损伤中，关节盘中新西兰的比例变大。模型越不稳定，新西兰在只读存储器中的比例就越大。在序贯损伤模型中，NZ在ROM中的比率被证明是不稳定程度的指标。在大多数动作中，椎间盘损伤造成了最不稳定的情况。小关节全切除术术中旋转运动最不稳定。

[Introduction] The instability of the lumbar spine has not been defined clearly in experimental and clinical studies. Panjabi firstly described the neutral zone (NZ) as the indicator of the instability of the spine. In this study the sequential injuries were produced by removal of the components of the lumbosacral junction step by step and the 3 D movements of these unstable conditions were measured for the purpose of investigating the index of the biomechanical instability especially focused on the NZ.The biomechanical roles of each component of the lumbosacral junction were also investigated.[Method] Ten fresh frozen cadaveric whole lumbar and lumbosacral specimens with natural lumbar lordosis and lumbosacral inclination were used. Six pure moments were applied to the top of the specimen ; flexion, extension, bilateral axial rotations and lateral bendings, The load-displacement curve was determined including the following three parameters ; neutral zone (NZ), elastic zone (EZ) and range of motion (ROM). The experiment was repeated in the following conditions ; (A) intact specimens, (B) posterior ligaments and facet capsules transected, (C) disc injury, (D) bilateral facetectomies. The data analysis was done in this sutdy. [Results] The ratios of NZ in ROM became bigger in the sequential lumbosacral injuries. The more instable the model became, the bigger the ratio of NZ in ROM became. In the sequential injury models the ratio of NZ in ROM was proven to be the indicator of the severity of the instability. The disc injury produced the most unstable conditions in most of the movements. The total facetectomies produced the most unstable condition in rotational movement.