Computed tomography-evaluated features of spinal degeneration: prevalence, intercorrelation, and association with self-reported low back pain

Background context: Although the role of radiographic abnormalities in the etiology of nonspecific low back pain (LBP) is unclear, the frequent identification of these features on radiologic studies continues to influence medical decision making.

Purpose: The primary purposes of the study were to evaluate the prevalence of lumbar spine degeneration features, evaluated on computed tomography (CT), in a community-based sample and to evaluate the association between lumbar spine degeneration features. The secondary purpose was to evaluate the association between spinal degeneration features and LBP.

Study design: This is a cross-sectional community-based study that was an ancillary project to the Framingham Heart Study.

Sample: A subset of 187 participants were chosen from the 3,529 participants enrolled in the Framingham Heart Study who underwent multidetector CT scan to assess aortic calcification.

Outcome measures: Self-report measures: LBP in the preceding 12 months was evaluated using a Nordic self-report questionnaire. Physiologic measures: Dichotomous variables indicating the presence of intervertebral disc narrowing, facet joint osteoarthritis (OA), spondylolysis, spondylolisthesis, and spinal stenosis and the density (in Hounsfield units) of multifidus and erector spinae muscles were evaluated on CT.

Methods: We calculated the prevalence of spinal degeneration features and mean density of multifidus and erector spinae muscles in groups of individuals with and without LBP. Using the chi(2) test for dichotomous and t test for continuous variables, we estimated the differences in spinal degeneration parameters between the aforementioned groups. To evaluate the association of spinal degeneration features with age, the prevalence of degeneration features was calculated in four age groups (less than 40, 40-50, 50-60, and 60+ years). We used multiple logistic regression models to examine the association between spinal degeneration features (before and after adjustment for age, sex, and body mass index [BMI]) and LBP, and between all degeneration features and LBP.

Results: In total, 104 men and 83 women, with a mean age (+/-standard deviation) of 52.6+/-10.8 years, participated in the study. There was a high prevalence of intervertebral disc narrowing (63.9%), facet joint OA (64.5%), and spondylolysis (11.5%) in the studied sample. When all spinal degeneration features as well as age, sex, and BMI were factored in stepwise fashion into a multiple logistic regression model, only spinal stenosis showed statistically significant association with LBP, odds ratio (OR) (95% confidence interval [CI]): 3.45 [1.12-10.68]. Significant association was found between facet joint OA and low density of multifidus (OR [95% CI]: 3.68 [1.36-9.97]) and erector spinae (OR [95% CI]: 2.80 [1.10-7.16]) muscles.

Conclusions: Degenerative features of the lumbar spine were extremely prevalent in this community-based sample. The only degenerative feature associated with self-reported LBP was spinal stenosis. Other degenerative features appear to be unassociated with LBP.