Mokhbi Soukane D, Shirazi-Adl A, Urban J P G
Department of Mechanical Engineering, Ecole Polytechnique, P.O. Box 6079, Station 'centre-ville', Montreal, QC H3C 3A7, Canada.
Eur Spine J. 2009 Feb;18(2):254-62. doi: 10.1007/s00586-008-0822-7. Epub 2008 Nov 18.
As the disc is the largest avascular structure in the body, disc cells depend for their normal function on an adequate supply of nutrients (oxygen and glucose) and the removal of metabolic by-products (lactic acid) via blood vessels at the cartilaginous endplates and annulus periphery. Concentration gradients develop depending on the balance between the rates of transport and rates of cellular activity. Since consumption and production rates are coupled via extracellular pH, the gradients are interdependent. This is a novel model study which takes into account the realistic 3D geometry of a L5-S1 lumbar disc in solving the nonlinear coupled diffusion equations. Effects of perturbations (calcification, sclerosis) in endplates, increases in cell metabolic rates following growth factor injection and changes in lumbar posture (kyphotic or lordotic) on extreme values of nutrient and metabolite concentrations and their spatial locations are investigated. Solute concentrations, particularly those of glucose, substantially diminish as a consequence of disturbances in supply at the endplates, increases in cell metabolic rate and more lordotic postures. Results, when compared to those from simplified axisymmetric models, demonstrate the importance of consideration of realistic 3D disc geometry.
由于椎间盘是人体中最大的无血管结构，椎间盘细胞的正常功能依赖于通过软骨终板和纤维环周边的血管充分供应营养物质（氧气和葡萄糖）以及清除代谢副产物（乳酸）。浓度梯度的形成取决于运输速率和细胞活动速率之间的平衡。由于消耗速率和产生速率通过细胞外pH值相互关联，所以这些梯度是相互依存的。这是一项新颖的模型研究，在求解非线性耦合扩散方程时考虑了L5-S1腰椎间盘实际的三维几何形状。研究了终板扰动（钙化、硬化）、生长因子注射后细胞代谢速率增加以及腰椎姿势改变（后凸或前凸）对营养物质和代谢产物浓度极值及其空间位置的影响。由于终板供应紊乱、细胞代谢速率增加以及更前凸的姿势，溶质浓度，尤其是葡萄糖浓度会大幅降低。与简化轴对称模型的结果相比，该结果证明了考虑实际三维椎间盘几何形状的重要性。
