AGE-RELATED DEGENERATION IS RELATED TO REDUCED CERVICAL SPINE RANGE OF MOTION IN THE ELDERLY James C. Boak (1,2,3,4), Dina Popovic (2), Eyal Itshayek (2), Lyne Koenig (3), Marcel F. Dvorak (2), Peter A. Cripton (1,2,4)
1. Injury Biomechanics Laboratory, Dept. of Mechanical Engineering, University of British Columbia, Canada. 2. Dept. of Orthopaedic Surgery, University of British Columbia, Canada. 3. Synaptic Analysis Consulting Group, Canada. 4. International Collaboration on Repair Discoveries, Canada.
[Frobin, 2002] A negative change in intervertebral disc height demonstrated a loss of disc height.
Spinal cord injuries (SCIs) can have devastating affects ranging from disability to permanent paralysis. The average age of people suffering SCIs in Canada is increasing. The majority of geriatric SCI injuries involve the cervical spine. Of these, 44% involve segments with spondylotic changes and they exhibit no gross osseous or ligamentous injury. [Pickett, 2006] This implies those injuries took place at a lower energy and displacement. Severe spondylosis results in stenosis and we hypothesize that the spondylosis also reduces the inherent range of motion (ROM) at the affected level. [Tanaka, 2001] In this context, minor trauma can cause the reduced ROM to be exceeded causing spinal cord injury. [Ehara, 2001] The biomechanics of the spondylotic cervical spine are not well understood and the quantitative relationship between spinal segmental ROM and degeneration has not been established. [Ehara, 2001] The objective of this study is to investigate how the ROM of the geriatric cervical spine is related to the radiographic extent of spinal degeneration.
Figure 1: C4/C5 range of motion change vs disc height change. The linear regression R2=0.70 and P-value=2.11E-06.
Sagittal plane radiographs of twenty geriatric patients were taken in full active flexion and extension. Custom image analysis software was developed using Matlab to measure the angular ROM of each vertebral motion segment from C1 to C7. Calculations were based on manually acquired anatomical landmarks in each image selected by spine surgeons (DP, EI). ROM for each vertebral motion segment was then compared to healthy adult normal values. [Frobin, 2002] A negative change in range of motion demonstrated a loss of range of motion. Intervertebral disc height loss was used as a quantifiable measure of degeneration. [Benneker, 2005] Intervertebral disc height was normalized to the anterior-posterior diameter of each segment’s inferior vertebral body. The disc height of each subject was compared to population normal values.
These results contribute to the understanding of the relationship between spine kinematics and disc degeneration. In the future we will attempt to link other bony degenerative features to biomechanical patterns that may predispose an individual to cervical spondylotic myelopathy or spinal cord injury. This in turn could lead to improved clinical screening guidelines for myelopathy and SCI risk in elderly patients.
Journal of Biomechanics 41(S1)
Results Most subjects showed a loss of disc height and angular ROM between C4 and C7. Only the C4/C5 and C5/C6 motion segments showed a statistically significant linear relationship between disc height change and angular ROM change. At C2/C3 there was no discernible pattern. Figure 1 illustrates the results from the C4/C5 motion segment. Range of Motion Difference from Healthy Values (degrees)
10 5 0 -0.3
-5 -10 -15 -20 Disc Height Difference from Healthy Values (normalized to anteriorposterior vertebral body width)
References L. Benneker, et al. Eur Spine J 14(1):27-35, 2005. S. Ehara and T. Shimamura. Skeletal Radiol 30(1):1–7, 2001. W Frobin, et al. Clin Biomech (Bristol, Avon) 17(1):21–31, 2002. W Frobin, et al. Clin Biomech (Bristol, Avon) 17(6):423–431, 2002. G E Pickett, et al. Spine 31(7):799–805, 2006. N. Tanaka, et al. Spine J 1(1):47-56, 2001. 16th ESB Congress, Posters