How Lumbar Spine Degenerative Changes Affect BMD and Osteoporosis Diagnosis
For many elderly patients, degenerative changes in the lumbar spine can result in a falsely elevated bone mineral density (BMD). This often results in missing a large number of patients who have osteoporosis.
To investigate this more deeply, Swedish researchers examined the impact of degenerative changes in the lumbar spine in elderly women over time. They used dual-energy x-ray absorptiometry (DXA) to measure these changes.
The researchers’ goal was to determine the implications for diagnosing these patients with osteoporosis.
Their results appeared in the paper “Degenerative changes at the lumbar spine - implications for bone mineral density measurement in elderly women.” It was presented at the 2011 Annual Meeting of the American Society of Bone and Mineral Research.
A total of 1,044 Swedish women participated in this study; they were 75 years old at the start of the study. These women were selected from the population-based Osteoporosis Prospective Risk Assessment study.
Researchers followed up with them after 5 years (n=698) and then again at 10 years (n=380).
Participants’ BMD levels were assessed using Lunar DPX-L DXA.
Degenerative changes were evaluated using DXA for lumbar vertebra (from L1-L4), including:
- asymmetric subchondral sclerosis
- disc space narrowing
- facet joint sclerosis
Intra-observer precision kappa values were 0.66 to 0.7, and evaluation of x-rays in the spine was also made for comparison.
In this study, at baseline, degenerative changes were more frequently observed in the distal part of the lumbar spine: 5% (L1), 15% (L2), 26% (L3), and 36% (L4).
The research team noted that these changes increased over time. At the 10-year follow-up for these study participants, incidence was 20% (L1), 39% (L2), 59% (L3), and 72% (L4)—changes that were noted as a significant increase in patients’ overall BMD.
Researchers then re-analyzed the study results following exclusion of all patients with degenerative changes. The re-analysis showed that BMD levels remained stable between 75 and 85 years old rather than the expected bone loss that researchers anticipated.
At baseline and using the study’s original criteria (BMD for L2-L4; standard deviation: <2.5), researchers determined that 33% of women had osteoporosis.
When the research team excluded the study participants who showed degenerative changes in the lumbar spine, the percentage of patients with osteoporosis jumped to 42%.
When L1-L2 (vertebrae that are much less prone to degenerative changes) were used as the diagnostic site for osteoporosis, researchers found that 46% of women had osteoporosis.
The following medications and supplements did not significantly alter the results:
- vitamin D
- hormone replacement therapy
This study confirmed that degenerative changes are commonly seen in elderly women, accelerate disproportionately over time, are more frequent in vertebrae that are more distal (with a gradient from L1-L4), and have a significant impact on DXA.
In elderly women—even in the absence of degenerative changes—BMD is maintained (rather than lost) over time.
The research team concluded that DXA is an accurate way to detect degenerative changes in the lumbar spine, and when used with BMD, DXA improves interpretation of osteoporosis status. According to the researchers, routine assessment of L1-L2 would improve the diagnosis of osteoporosis as well as evaluation of osteoporosis treatments.