Related Experiment Video
Updated: Aug 16, 2026
A Tissue Displacement-based Contusive Spinal Cord Injury Model in Mice
Published on: June 18, 2017
Effect of displacement rate on the tensile mechanics of pediatric cervical functional spinal units
David J Nuckley1, Suzanne M Hertsted, Michael P Eck
1Applied Biomechanics Laboratory, Department of Mechanical Engineering, University of Washington, 501 Eastlake Avenue East, Suite 102, Seattle, Washington, USA. dnuckley@u.washington.edu
Insights
The tensile strength and stiffness of the cervical spine increase with faster loading rates. This study reveals a power-law relationship, crucial for understanding spinal viscoelasticity and preventing injuries.
Area of Science:
- Biomechanics
- Spinal Mechanics
- Material Science
Background:
- The mechanical behavior of the cervical spine is critical for understanding injury mechanisms.
- Loading rate significantly influences tissue response, but its effect on functional spinal units is not fully elucidated.
Purpose of the Study:
- To investigate the impact of varying displacement rates on the tensile properties of cervical spine functional spinal units.
- To characterize the rate-dependent mechanical response and failure mechanics of the cervical spine.
Main Methods:
- Tensile loading was applied to 40 isolated baboon cervical functional spinal units across a wide range of displacement rates (0.5–5000 mm/s).
- Measurements included stiffness, ultimate failure load, and displacement at failure, with normalization by spinal geometry for material and structural properties.
Main Results:
- Tensile stiffness and failure load (both absolute and normalized) significantly increased with higher displacement rates (p<0.001).
- A two-fold increase in stiffness and a four-fold increase in failure load were observed from the slowest to fastest rates.
- Failure strain showed no significant correlation with loading rate (p=0.146).
- A power-law relationship was identified between displacement rate and both functional and failure mechanics.
Conclusions:
- Cervical spine functional spinal units exhibit significant rate-dependent tensile mechanics.
- Understanding these viscoelastic properties is essential for developing accurate biomechanical models and effective injury prevention strategies for dynamic spine injuries.
Abstract:
This study examined the effect of loading (displacement) rate on the tensile mechanics of cervical spine functional spinal units. A total of 40 isolated functional spinal units (two vertebrae and the adjoining soft tissues) from juvenile male baboons (10+/-0.6-human equivalent years old) were subjected to tensile loading spanning four orders of magnitude from 0.5 to 5000 mm/s. The stiffness, ultimate failure load, and corresponding displacement at failure were measured for each specimen and normalized by spinal geometry to examine the material properties as well as the structural properties. The tensile stiffness, failure load, normalized stiffness, and normalized failure load significantly increased (ANOVA, p<0.001) with increasing displacement rate. From the slowest to fastest loading rate, a two-fold increase in stiffness and four-fold increase in failure load were observed. The tensile failure strains (1.07+/-0.31 mm/mm strain) were not significantly correlated with loading rate (ANOVA, p=0.146). Both the functional (non-destructive stiffness and normalized stiffness) and failure mechanics of isolated functional spinal units exhibited a power-law relationship with displacement rate. Modeling efforts utilizing these rate-dependent characteristics will enhance our understanding of the tensile viscoelastic response of the spine and enable improved dynamic injury prevention schemes.
Related Concept Videos
01:15Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
01:21Plastic Behavior