Intervertebral disc (IVD) height is largely influential on spinal segment biomechanics of the cervical and lumbar spine. The IVDs in the cervical and lumbar spine have degeneration by the age of 30, with increasing probabilities from aging. Cervical and lumbar disc degeneration positively correlates with chronic back pain. Spinal facet angle (FA) has been documented for the cervical and lumbar spine. However, no studies have investigated the relationship between FA and range of motion (ROM) in flexion/extension, axial rotation, and lateral bending.

I investigated the isolated effect of the IVD height on cervical and lumbar spine biomechanics. I also investigated the relationship between FA and range of motion (ROM) across several different motions within these sections.

First, cervical and lumbar functional spinal units (FSUs) were imported into ANSA, a preprocessing software. The IVDs were modified to be 25% thicker and thinner. This was done to simulate how an individual’s IVD may have performed earlier and later in life. Next, the FSUs were imported into FEBio Studio, an open-source finite element analyzer. Material properties were assigned, contact was established, and boundary and loading conditions that simulate flexion were applied. Finally, flexion tests were conducted and ROMs were analyzed. Rotations were recorded as Euler angles in relation to the base of the FSUs. FAs of the lumbar and cervical spines were measured with respect to the sagittal plane, with the transverse plane angle also recorded for the cervical spine. These angles were compared to previous results.

Flexion ROMs increased in the cervical and lumbar spine with thicker IVDs. IVD thickness influenced ROM in flexion in the lumbar spine to a greater degree. Cervical spine FAs have a larger effect on ROM than the lumbar FAs. These findings pertained to extension and lateral bending. No relation was found between FA and ROM in axial rotation for the cervical and lumbar spine.

The results confirmed my hypothesis that the IVD influences lumbar spine mechanics compared to the cervical spine. In addition, the cervical spine FA has a greater effect on ROM than the lumbar spine, mostly relating to extension and lateral bending.