Alkalay Ron N, Harrigan Timothy P
Center for Advanced Orthopedic Studies, Department of Orthopedic Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, Massachusetts, 02215.
Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road Laurel, Maryland, 20723.
J Orthop Res. 2016 Oct;34(10):1808-1819. doi: 10.1002/jor.23154. Epub 2016 Aug 1.
To investigate the effects of a clinical lytic defect on the structural response of human thoracolumbar functional spinal unit. A novel CT-compatible mechanical test system was used to image the deformation of a T12-L1 motion segment and measure the change in strain response under compressive loads ranging from 50 to 750 N. A lytic lesion (LM) with cortex involvement (33% by volume) was introduced to the upper vertebral body and the CT experiments were repeated. Finite element models, established from the CT volumes, were used to investigate the defect's effects on the structural response and the state of principal and shear stresses within the affected and adjacent vertebrae. The lytic lesion resulted in severe loss of the vertebral structural competence, resulting in significant, non-linear, and asymmetric increase in the experimentally measured strains and computed stresses within both vertebrae (p < 0.01). At the cortex, the tensile strains were significantly increased, while compressive strains significantly decreased, (p < 0.05). Both the vertebral bone and cortex regions adjacent to the defect showed significant increase in computed compressive, tensile, and shear stresses (p < 0.01). Changes in stress and strain distribution within the affected and adjacent vertebral bone and the experimentally observed bulging and buckling of the vertebral cortices suggested that initiation of catastrophic vertebral failure may occur under load magnitudes encountered in daily living. Although the effect of LM on the global deformation of the spine was well-predicted, our results show that FE predictions of local strain changes must be carefully assessed for clinical relevance. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1808-1819, 2016.
为研究临床溶解性缺损对人体胸腰段功能性脊柱单元结构响应的影响。使用一种新型的与CT兼容的力学测试系统对T12-L1运动节段的变形进行成像，并测量在50至750 N压缩载荷下应变响应的变化。将累及皮质（体积占33%）的溶骨性病变（LM）引入上位椎体，并重复进行CT实验。根据CT容积建立有限元模型，以研究缺损对受累椎体及相邻椎体结构响应以及主应力和剪应力状态的影响。溶骨性病变导致椎体结构强度严重丧失，致使两个椎体在实验测量应变和计算应力方面均出现显著、非线性且不对称的增加（p < 0.01）。在皮质处，拉伸应变显著增加，而压缩应变显著降低（p < 0.05）。缺损相邻的椎体骨和皮质区域在计算的压缩、拉伸和剪应力方面均显著增加（p < 0.01）。受累椎体及相邻椎体骨内应力和应变分布的变化以及实验观察到的椎体皮质鼓起和屈曲表明，在日常生活中遇到的载荷大小下可能会引发灾难性的椎体失效。尽管LM对脊柱整体变形的影响得到了很好的预测，但我们的结果表明，对于临床相关性，必须仔细评估有限元对局部应变变化的预测。© 2016骨科研究协会。由威利期刊公司出版。《矫形外科学研究》34:1808 - 1819，2016年。
