Effects of Inclined Axial Compressive Force and Flexion Moment on Lumbosacral Shear Stiffness:An in vitro Biomechanical Study
10.16156/j.1004-7220.2025.05.009
- VernacularTitle:轴向压缩载荷倾斜和前屈力矩对腰骶椎剪切刚度影响的离体生物力学研究
- Author:
Zhiping HUANG
1
;
Jianying ZHENG
;
Jiachen YANG
;
Junhao LIU
;
Junyu LIN
;
Xiuhua WU
;
Linghong ZHOU
;
Qingan ZHU
Author Information
1. 南方医科大学生物医学工程学院,广州 510515;南方医科大学南方医院脊柱骨科,广州 510515
- Publication Type:Journal Article
- Keywords:
lumbosacral vertebrae;
shear stiffness;
axial compressive force;
flexion moment;
spinal degeneration
- From:
Journal of Medical Biomechanics
2025;40(5):1150-1156
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the effects of inclined axial compressive force and flexion moment on the anterior and posterior shear stiffness of the lumbosacral segment.Methods Six fresh-frozen human cadaveric L5-S1 segments were tested under intact and two progressively impaired structural conditions:intact,a 4-mm bilateral facet joint gap,and anterior discectomy with nucleus pulposus removal plus circumferential release of the inner annular fibers(disc injury).A 300 N axial compressive force was applied either vertically downward or with a 10° or 20° anterior inclination through the disc's shear center.Anterior(0 N to 250 N)and posterior(-50 N to 0 N)shear tests were conducted using a material testing machine.These tests were repeated under a 5 N-m flexion moment.The relative motion between L5 and Si was measured using a three-dimensional motion capture system.Results In the intact state,the inclination of the axial compressive force did not significantly alter anterior or posterior shear stiffness.However,the application of a flexion moment increased anterior shear stiffness by 49.3％.Progressive structural damage resulted in incremental increases in anteroposterior shear translation and corresponding reductions in stiffness.Notably,under combined loading with axial compression and flexion moment,anterior stiffness decreased from 939 N/mm(intact)to 224 N/mm(disc injury),while posterior stiffness decreased from 572 N/mm to 217 N/mm.Within the low-load range,no significant differences in shear stiffness were observed across any structural conditions,regardless of axial force inclination or combined with a flexion moment.Conclusions This study supports the clinical view that retro-inclination of the pelvis serves as a compensatory mechanism to enhance segmental shear stability.However,this compensatory capacity gradually diminishes and ultimately fails as spinal degeneration progresses.
