Three-dimensional biomechanical properties of the human cervical spine in vitro

Abstract

Our aim was to determine the biomechanical properties of the normal human cervical spine under physiological static loads. The three-dimensional displacements under three pure moments: flexion-extension, left-right lateral bending and left-right axial torsion--were measured in 56 intact functional spinal units (FSUs) taken from between C2 and C7 in 29 human cadavers. For each mode of loading, load-displacement curves were plotted. Then we calculated each neutral zone, range of motion, neutral zone ratio, ratio of coupled motion, limit moment and secant stiffness. The effects of intervertebral disc degeneration and the disc level were also taken into account by the analysis of variance. Our results adequately demonstrated both the non-linearity of load-displacement curves and the neutral zone of the cervical spine in three-dimensional space. At the same time, we found statistically that the stiffness in the three planes are significantly different, as are the stiffnesses in lateral bending of successive different FSUs. However, significant differences of stiffness in different states of disc degeneration were only found in right lateral bending. There were significant differences between levels in ratio of coupled motion under both lateral bending and axial torsion. The loading cycle conditions and the biomechanical responses of principal motion of C1-2 are also reported.

Kinematic Motion Patterns of the Cranial and Caudal Canine Cervical Spine

“…A study on the human lumbar spine found that torsional strains rather than compressive loads are likely to be responsible for intervertebral disc degeneration 43 . The difference in both the pattern and the magnitude of loading between large and small breed dogs may in part explain why cervical complaints in large‐breed dogs tend to occur in the caudal cervical spine 44,45 . Whereas our study was not designed to address this question directly, further studies, possibly involving a combination of finite element modeling and direct validation in cadaveric specimens, should be undertaken to more completely explore this potentially intriguing relationship.…”

“…43 The difference in both the pattern and the magnitude of loading between large and small breed dogs may in part explain why cervical complaints in large-breed dogs tend to occur in the caudal cervical spine. 44,45 Whereas our study was not designed to address this question directly, further studies, possibly involving a combination of finite element modeling and direct validation in cadaveric specimens, should be undertaken to more completely explore this potentially intriguing relationship. We found that the ratio of CM/PM increased for the caudal cervical levels for left/right lateral bending and decreased for left/right axial rotation.…”

Biomechanical Analysis of the Three‐Dimensional Motion Pattern of the Canine Cervical Spine Segment C4–C5

“…7 In a previous report in humans, the ratio of the CM to the PM in left/right lateral bending and left/right axial rotation was 0.37 and 0.46, respectively. 14…”

“…To evaluate the extent of the coupling effect, the dimensionless ratio of CM to PM is reported. [14][15][16] For dogs, no such information is available. Recommendations for mechanical testing protocols have been made.…”

In vitro analysis of the segmental flexibility of the thoracic spine

“…Few studies have focused on the biomechanics of the thoracic spine, because prior research mainly focused on the lumbar [1–4] and the cervical spine [5–7]. This is due to the fact that chronic degenerative diseases of the thoracic spine are reported to have a lower incidence and therefore seem to be clinically of lower importance [8].…”