Park W M, Wang S, Kim Y H, Wood K B, Sim J A, Li G
Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital/Harvard Medical School, Boston, MA 02114, USA.
J Biomech Eng. 2012 Jan;134(1):011009. doi: 10.1115/1.4005541.
Determination of physiological loads in human lumbar spine is critical for understanding the mechanisms of lumbar diseases and for designing surgical treatments. Computational models have been used widely to estimate the physiological loads of the spine during simulated functional activities. However, various assumptions on physiological factors such as the intra-abdominal pressure (IAP), centers of mass (COMs) of the upper body and lumbar segments, and vertebral centers of rotation (CORs) have been made in modeling techniques. Systematic knowledge of how these assumptions will affect the predicted spinal biomechanics is important for improving the simulation accuracy. In this paper, we developed a 3D subject-specific numerical model of the lumbosacral spine including T12 and 90 muscles. The effects of the IAP magnitude and COMs locations on the COR of each motion segment and on the joint/muscle forces were investigated using a global convergence optimization procedure when the subject was in a weight bearing standing position. The data indicated that the line connecting the CORs showed a smaller curvature than the lordosis of the lumbar spine in standing posture when the IAP was 0 kPa and the COMs were 10 mm anterior to the geometric center of the T12 vertebra. Increasing the IAP from 0 kPa to 10 kPa shifted the location of CORs toward the posterior direction (from 1.4 ± 8.9 mm anterior to intervertebral disc (IVD) centers to 40.5 ± 3.1 mm posterior to the IVD centers) and reduced the average joint force (from 0.78 ± 0.11 Body weight (BW) to 0.31 ± 0.07 BW) and overall muscle force (from 349.3 ± 57.7 N to 221.5 ± 84.2 N). Anterior movement of the COMs from -30 mm to 70 mm relative to the geometric center of T12 vertebra caused an anterior shift of the CORs (from 25.1 ± 8.3 mm posterior to IVD centers to 7.8 ± 6.2 mm anterior to IVD centers) and increases of average joint forces (from 0.78 ± 0.1 BW to 0.93 ± 0.1 BW) and muscle force (from 348.9 ± 47.7 N to 452.9 ± 58.6 N). Therefore, it is important to consider the IAP and correct COMs in order to accurately simulate human spine biomechanics. The method and results of this study could be useful for designing prevention strategies of spinal injuries and recurrences, and for enhancing rehabilitation efficiency.
确定人体腰椎的生理负荷对于理解腰椎疾病的发病机制以及设计手术治疗方案至关重要。计算模型已被广泛用于估计模拟功能活动期间脊柱的生理负荷。然而，在建模技术中，对诸如腹内压（IAP）、上半身和腰椎节段的质心（COM）以及椎体旋转中心（COR）等生理因素做出了各种假设。系统了解这些假设如何影响预测的脊柱生物力学对于提高模拟精度很重要。在本文中，我们开发了一个包含T12和90块肌肉的腰骶椎三维个体化数值模型。当受试者处于负重站立姿势时，使用全局收敛优化程序研究了IAP大小和COM位置对每个运动节段的COR以及关节/肌肉力的影响。数据表明，当IAP为0 kPa且COM位于T12椎体几何中心前方10 mm时，连接COR的线在站立姿势下的曲率小于腰椎前凸。将IAP从0 kPa增加到10 kPa会使COR的位置向后移动（从椎间盘（IVD）中心前方1.4±8.9 mm到IVD中心后方40.5±3.1 mm），并降低平均关节力（从0.78±0.11体重（BW）降至0.31±0.07 BW）和总肌肉力（从349.3±57.7 N降至221.5±84.2 N）。COM相对于T12椎体几何中心从前30 mm移动到后70 mm会导致COR向前移动（从IVD中心后方25.1±8.3 mm到IVD中心前方7.8±6.2 mm），并增加平均关节力（从0.78±0.1 BW增加到0.93±0.1 BW）和肌肉力（从348.9±47.7 N增加到452.9±58.6 N）。因此，为了准确模拟人体脊柱生物力学，考虑IAP和正确的COM很重要。本研究的方法和结果可能有助于设计脊柱损伤和复发的预防策略，并提高康复效率。
