1.中南大学湘雅二医院 脊柱外科;2.首都医科大学附属北京安贞医院 心内科;3.中南大学湘雅医学院 人体解剖与生物;4.中南大学湘雅三医院 放射科
,国家自然科学基金项目（面上项目，重点项目，重大项目）NSFC 81571939, NSFC 81772134,17-163-12-ZT-001-041-01
1.Department of Spine,the Second Xiangya Hospital,Central South University;2.Department of Cardiology,Beijing Anzhen Hospital,Capital Medical University;3.Department of Human Anatomy and Neurobiology,Xiangya Medical School,Central South University;4.Department of Radiology,the Third Xiangya Hospital,Central South University
目的 在中国的５５岁到６５岁之间的老年妇女,约66.47%充当带孙儿孙女的角色,而频繁的负重(抱孩子)的动作增加了腰椎慢性疲劳的风险。本文利用有限元方法模拟中国女性抱小孩的行为,分析验证脊柱松质骨的应力集中效应,并对应力集中位置进行疲劳仿真和预测,对中国老年女性在隔代抚养时的腰椎保护具有很大的指导意义。方法 根据无退行性临床症状的中国老年女性腰椎CT,进行图像分割和三维重建,建立具有中国老年女性腰椎特点的腰椎三维几何模型,在三种载荷条件下计算分析脊柱松质骨局部应力和应变分布情况,选取关键位置进行疲劳仿真,预测不同疲劳载荷强度下脊柱松质骨的疲劳耐受极限。结果 腰椎椎间盘内压受力最大部位在弯腰不抱小孩状态下,弯腰抱小孩和直立之后,都在L5-S1之间,分别为3.56 Mpa,5.38 Mpa和1.47 Mpa ；腰椎椎体上下的终板软骨受力最大部位,在弯腰不抱小孩状态下,弯腰抱小孩和直立之后,都在L5的上下终板软骨的边缘,分别为16.55 Mpa ,23.58 Mpa和26.55 Mpa；腰椎椎体在弯腰无负重,弯腰抱小孩和抱起孩子直立三种状态下,受力最大的位置均在L5的侧后方,对应的疲劳极限次数分别为1?000?000次以上,1?300次,18次。结论 中国老年女性如果连续抱三岁孩子直立的动作次数超过18次,L4-L5的椎体后部以及椎弓根松质骨将面临疲劳性损伤的风险,研究结果对于保护老年女性的腰椎健康具有很大的意义。
Objective: The finite element method was developed in Chinese women holding children. Up to 66.47% of the 55-65 years old Chinese women stayed home and acted as grandchildren sitter (e.g. lifting kid in daily life). In consequence of these frequently loading-bear, the chronic lumbar fatigue probably caused higher risk of lumbar degeneration and fatigue. In this study, A lumbar finite element model (FEM) with specific bone mineral density(BMD) and geometry of Chinese 55-65 years old women were developed and validated to predict the bio-mechanical response. Method The material properties of elder women lumbar vertebra was modified according to degenerated bone mineral density, and geometry was adjusted based on 55-65 years old women’s intervertebral disc height. The motion of lifting kid in 3 different loading condition were simulated by the elder women FEM, and the stress and strain distribution were calculated and predicted, then the limitations of fatigue tolerances of the lumbar spine were also predicted. Result The calculated maximum intradiscal pressure were located in L5-S, which were 3.56 Mpa, 5.38 Mpa and 1.47 Mpa, while the maximum effective stress contribution of endplate cartilage were located in posterior edge of L5 up and down endplate cartilage, which were 16.55 Mpa, 23.58 Mpa and 26.55 Mpa in the bending without lifting weight, the bending with lifting 3-year-old child and upright with 3-year-old child posture respectively. More importantly, the fatigue risk limitation frequency(18 times) of upright with 3-year-old dummy was predicted with the functional equation of fatigue and stress which deduced by genetic algorithm, which combined with the effective stress of lumbar vertebrae spongy bone calculated from FEM. Conclusion These results imply that the lifting child motion could increase the risk of lumbar fatigue and degeneration in elder women, and the elder women should keep below the limitation frequency of the motion of lifting kids in the daily life. With the deterioration of aging problem in China and the increasing of newborns, this study could put forward a scientific guidance to 55-65 years old women who lifting kid in daily life frequently.