Comparative morphometry of the lower lumbar vertebrae: osteometry in dry bones and computed tomography images of patients with and without low back pain

Measurement of occlusion of the spinal canal and intervertebral foramen by intervertebral disc bulge

Background

Disc protrusion has been proposed to be a possible cause of both pain and stenosis in the lower spine. No previous study has described the amount of disc occlusion of the spinal canal and intervertebral foramen that occurs under different loading conditions. The objective of this study was to quantitatively assess the percent occlusion of the spinal canal and intervertebral foramen by disc bulge under different loading conditions.

Methods

Spinal canal depth and foraminal width were measured on computed tomography–scanned images of 7 human lumbar spine specimens. In vitro disc bulge measurements were completed by use of a previously described method in which single functional spinal units were subjected to 3 separate load protocols in a spine test machine and disc bulge was recorded with an optoelectric motion system that tracked active light-emitting diodes placed on the posterior and posterolateral aspects of the intervertebral disc. Occlusion was defined as percentage of encroachment into area of interest by maximum measured disc bulge at corresponding point of interest (the spinal canal is at the posterior point; the intervertebral foramen is at the posterolateral point).

Results

The mean spinal canal depth and mean foraminal width were 19 4 ± mm and 5 ± 2 mm, respectively. Mean spinal canal occlusion under a 250-N axial load, ± 2.5 Nm of flexion/extension, and ± 2.5 Nm of lateral bend was 2.5% ± 1.9%, 2.5% ± 1.6%, and 1.5% ± 0.8%, respectively. Mean intervertebral foramen occlusion under a 250-N axial load, ± 2.5 Nm of flexion/extension, and ± 2.5 Nm of lateral bend was 7.8% ± 4.7%, 9.5% ± 5.7%, and 11.3% ± 6.2%, respectively.

Conclusion

Percent occlusion of the spinal canal and intervertebral foramen is dependent on magnitude and direction of load. Exiting neural elements at the location of the intervertebral foramen are the most vulnerable to impingement and generation of pain.

Clinical correlation of radiological spinal stenosis after standardization for vertebral body size

AIM

To determine the relationship between the degree of radiographic lumbar spinal stenosis, adjusted with an internal control for vertebral body size, and disability from lumbar stenosis.

MATERIALS AND METHODS

one hundred and twenty-three consecutive patients with clinical and radiological confirmation of neural impingement secondary to lumbar stenosis were enrolled prospectively. Thecal sac anteroposterior (AP) diameter (TSD) and cross-sectional area (CSA), and vertebral body AP dimension (VBD) were determined. These parameters were then correlated with patients' symptoms using the modified Roland-Morris questionnaire (RMQ) disability score.

RESULTS

No statistically significant inverse correlation was found between the TSD and RMQ score (p=0.433), between the CSA and RMQ score (p=0.124), or between the TSD:VBD ratio and RMQ score (p=0.109). There was a significant positive correlation between the CSA:VBD ratio and RMQ score (p=.036), and therefore, there was no statistical support for an inverse relationship between the two. There was a significant difference in mean RMQ scores when the patients were divided into those with CSA greater than or equal to 70 mm(2) and those less than 70 mm(2), with T=-2.104 and p=0.038.

CONCLUSION

The degree of radiographic lumbar spinal stenosis, even with the use of an internal control of vertebral body size and standardized disability questionnaires, does not correlate with clinical symptoms. However, patients with more severe stenosis below a CSA critical threshold of 70 mm(2), have significantly greater functional disability.