Effective modulus of the human intervertebral disc and its effect on vertebral bone stress

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• 作者：Haisheng Yang^a ; ^{yhs267@foxmail.com" class="auth_mail" title="E-mail the corresponding author} ; ^{yanghaisheng267@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Michael G. Jekir^a ; Maxwell W. Davis^a ; Tony M. Keaveny^a ; ^b ; ¹ ; ^{tonykeaveny@berkeley.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Wedge fracture ; Osteoporosis ; Intervertebral disc ; Finite element analysis ; Bone strength
• 刊名：Journal of Biomechanics
• 出版年：2016
• 出版时间：3 May 2016
• 年：2016
• 卷：49
• 期：7
• 页码：1134-1140
• 全文大小：2104 K

文摘

The mechanism of vertebral wedge fractures remains unclear and may relate to typical variations in the mechanical behavior of the intervertebral disc. To gain insight, we tested 16 individual whole discs (between levels T8 and L5) from nine cadavers (mean±SD: 66±16 years), loaded in compression at different rates (0.05–20.0% strain/s), to measure a homogenized “effective” linear elastic modulus of the entire disc. The measured effective modulus, and average disc height, were then input and varied parametrically in micro-CT-based finite element models (60-μm element size, up to 80 million elements each) of six T9 human vertebrae that were virtually loaded to 3° of moderate forward-flexion via a homogenized disc. Across all specimens and loading rates, the measured effective modulus of the disc ranged from 5.8 to 42.7 MPa and was significantly higher for higher rates of loading (p<0.002); average disc height ranged from 2.9 to 9.3 mm. The parametric finite element analysis indicated that, as disc modulus increased and disc height decreased across these ranges, the vertebral bone stresses increased but their spatial distribution was largely unchanged: most of the highest stresses occurred in the central trabecular bone and endplates, and not anteriorly. Taken together with the literature, our findings suggest that the effective modulus of the human intervertebral disc should rarely exceed 100 MPa and that typical variations in disc effective modulus (and less so, height) minimally influence the spatial distribution but can appreciably influence the magnitude of stress within the vertebral body.