High lumbar spinal stenosis rates seen in elderly Framingham Heart study subjects

ORLANDO, Fla. — Orthopedic researchers found rates of acquired lumbar stenosis increased with age in their ancillary project to the Framingham Heart Study, which characterized the prevalence of congenital and acquired lumbar spinal stenosis in 191 offspring and third-generation subjects in the famous heart study.

At the 2010 Annual Meeting of the North American Spine Society, David H. Kim, MD, of New England Baptist Hospital in Boston, presented the findings which shed new light on the role genes may play in lumbar stenosis. He said the investigation was possible due to advanced multi-detector CT scanning performed on some of the Framingham study subjects to assess coronary or aortic calcifications.

“We thought this was a golden opportunity to derive some spine-related information from this cohort,” said Kim, who accepted the Spine Journal Editor’s Choice award at the meeting for the research on behalf of his team.

The study population was fairly representative of the United States, Kim said, noting “19.4% of the subjects reported significant back pain based on our definition and 75.4% of the subjects who reported low back pain also reported some form of distal symptomatology.”

The 191 subjects who underwent multi-detector CT scanning completed the validated Nordic Low Back Pain Questionnaire in which significant low back pain (LBP) is defined as pain occurring on most days of 1 month of the preceding 12 months. Some survey questions addressed symptoms, pain, sensory changes and weakness.

All scans were made on an A-size multi-detector scanner. By viewing 3.5 mm cuts, typically in the axial plane, assessors who were blinded to the age and demographics of the subjects measured canal size on the images to identify stenosis. Kim noted that a rigorous CT-reading protocol was developed.

The researchers then used specialized software to delineate congenital from acquired stenosis, using commonly accepted thresholds for both.

“We were able to calculate kappa statistics for reliability of reader ratings and achieved fair to excellent kappa statistics. These are much higher than previously reported kappa statistics for more qualitative assessment of stenosis in other studies,” he said, noting they also performed a stepwise multiple logistic regression statistical analysis using LBP as the dependent variable and spinal stenosis, age, gender and body mass index (BMI) as the independent variable.

“This is the first cross-sectional study describing the prevalence of spinal stenosis in an unselected community-based population,” Kim said in discussing the study’s significance.

Outcomes indicated a relatively high prevalence of radiographic stenosis in that population with a 4.7% prevalence of relative and 2.6% prevalence of absolute congenital stenosis. The rates for acquired stenosis were higher; 22.5% for relative and 7.3% for absolute stenosis and the prevalence of stenosis of any kind was 23.6% for relative and 8.4% for absolute, he said, noting in the 50- to 69-year-old age group rates of relative and absolute acquired stenosis increased to 47.2% and 19.9%, respectively.

“It’s a high prevalence of stenosis in the elderly population and this warns against attributing symptoms to stenosis solely on the basis of imaging studies,” Kim said.

From the regression analysis, there was no association between LBP and age, gender or BMI, but the researchers found a statistically significant association between the presence of spinal stenosis and the occurrence of reported LBP in the subjects, he said.

The possibility of missing or underestimating stenosis was a study limitation.

Additional analyses performed by the group revealed important findings concerning the relationship between LBP and spondylolysis, facet joint osteoarthritis, facet joint orientation and obesity. – by Susan M. Rapp

Reference:

• Kalichman L, et al. Spinal stenosis prevalence and association with symptoms: The Framingham Study. Editor’s Choice Award. Presented at the 2010 Annual Meeting of the North American Spine Society. Oct. 5-9, 2010. Orlando, Fla.

• David H. Kim, MD, can be reached at 125 Parker Hill Ave., Boston, MA 02120; 617-754-5595; e-mail: dhkim@caregroup.harvard.edu. He has stock in and is a consultant to Axial Biotech. He is a consultant to Pioneer, Medtronic and DePuy, is on the speakers bureau of DePuy, Medtronic and Stryker, and received travel compensation from Medtronic and Stryker. His institution received research support from New England Baptist Hospital.

Kalichman and colleagues conducted a population-based analysis of the prevalence of congenital and acquired lumbar spinal stenosis in a community-based sample. They found that the prevalence of acquired stenosis increased with age, and that stenosis is associated with a threefold higher risk of experiencing low back pain. Although these finding are intuitive, to date no one has accurately documented these facts. These findings have implications for current treatment guidelines and for future funding of treatment. These findings further corroborate the fact that age-related degenerative changes are not benign and will be even more of a societal burden with each year that the population ages.

– Isador H. Lieberman, MD, MBA, FRCSC
Scoliosis & Spine Tumor Center, Texas Back Institute
Plano, Texas

Isador H. Lieberman, MD, MBA, FRCSC is a consultant to, does teaching and speaking on behalf of and is an advisory committee/review panel member for Trans1 Inc.

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