The Pathomechanism of Isthmic Lumbar Spondylolisthesis: A Biomechanical Study in Immature Calf Spines
The Pathomechanism of Isthmic Lumbar Spondylolisthesis: A Biomechanical Study in Immature Calf Spines
复制标题
峡部腰椎滑脱的病理机制：未成熟小腿脊柱的生物力学研究
作者：
K. Sairyo;V. Goel;L. Grobler;T. Ikata;S. Katoh
研究设计。前切力应用于未成熟的小腿腰椎功能脊柱单位，直到失败。目标。为了了解儿童腰椎滑脱的发生机制，阐明伴有部部缺损的未成熟小牛腰椎的滑脱机制是第一步。背景资料摘要。从溶解到滑脱的过程发生在青春期的生长高峰期。然而，未成熟腰椎滑脱的机制尚不清楚。方法。双侧部缺损发生在吻侧椎体。然后将标本分配到两组中的一组：具有完整椎间盘的功能脊柱单元（n = 5）和椎间盘剥离（n = 5）。在前一组中，椎间盘保持完整，而在椎间盘剥离组中，沿椎间盘中平面切开前纵韧带和椎间盘前后深度的75%。采用单轴MTS机（MTS System, Minneapolis， MN），对每个试件施加前后剪力。破坏荷载和破坏时的位移由荷载-位移曲线计算。失败部位也进行了影像学和组织学评估。结果。在973.8±78.1 N下，椎间盘完整组的5个功能脊柱单元失效，而椎间盘剥离组的5个功能脊柱单元在986.4±124.2 N下失效，两组数据无显著差异。所有标本在x光片上均显示通过生长板的位移。组织学上，观察到在尾椎上生长板和骨性终板之间发生失败，表明该部位是最薄弱的环节。结论。结果提示，小儿未成熟腰椎伴部缺损，生长板与骨性终板之间可能发生滑移。
Study Design. Anterior shearing force was applied to immature calf lumbar functional spinal units until failure. Objectives. To clarify the mechanism of slippage in immature calf lumbar spines with pars defects as a first step to understand the mechanism of spondylolisthesis in pediatric human lumbar spines. Summary of Background Data. Progression from lysis to olisthesis occurs during the adolescent growth spurt. However, the mechanism of slippage in the immature lumbar spine has not yet been understood clearly. Methods. Bilateral pars defects were created at the rostral vertebra. The specimens then were assigned to one of the two groups: functional spinal units with intact disc (n = 5) and with disc dissected (n = 5). In the former group, the disc was left intact, whereas in the disc dissected group, the anterior longitudinal ligament and 75% of the anterior‐to‐posterior depth of the disc were incised along the mid‐disc plane. Using a uniaxial MTS machine (MTS System, Minneapolis, MN), anteroposterior shearing force was applied to each specimen. Failure load and displacement at failure were calculated from the load‐displacement curve. Failure sites also were assessed radiographically and histologically. Results. The five functional spinal units in the intact disc group failed at 973.8 ± 78.1 N, whereas specimens in the disc dissected group failed at 986.4 ± 124.2 N. The data showed no significant differences between the two groups. All the specimens showed displacement through the growth plates on radiographs. Histologically, failure was observed to occur between the superior growth plate and osseous endplate of caudal vertebra, indicating that this site is the weakest link. Conclusions. The results suggest that in the pediatric immature lumbar spine with pars defects, slippage may occur between the growth plate and osseous endplate.