Quantitative ultrasound measurements of the calcaneus in the prediction of lumbar spine degeneration

A cross-sectional study was conducted to evaluate the possible use of a low-cost radiation-free technique in the prediction of degenerative changes in the lumbar spine. Although an inverse correlation between osteoporosis and degenerative changes in the lumbar spine has been reported, no previous studies have asked whether there is a correlation between calcaneal quantitative ultrasound results and degenerative findings in the lumbar spine. In 117 patients with low back pain or pain in the lower limb, ultrasonographic parameters (speed of sound, broadband ultrasound attenuation, stiffness) of the calcaneus were correlated with evidence of degenerative changes and stenosis on magnetic resonance scans of the lumbar spine. Linear and logistic regression, as well as receiver operator characteristic curve analyses, were used to evaluate the correlation. Lumbar spine stenosis was associated with elevated calcaneal ultrasonographic parameters, particularly speed of sound. For the identification of a narrowing of the lumbar spinal canal below 100 mm² of dural sac cross-sectional area, speed of sound showed 89% sensitivity and 75% specificity in males older than 60 years. In male patients, we also found a significant positive correlation between ultrasonographic parameters and scores on a degenerative scale that primarily reflects intervertebral disc degeneration (P=0.019 for speed of sound; P=0.039 for stiffness). In conclusion, calcaneal quantitative ultrasound is frequently used in elderly patients with low back pain as a diagnostic test for osteoporosis. The incidental finding of high values on ultrasonographic parameters in these subjects, particularly in males, is highly correlated with lumbar spine degeneration and stenosis, and can help to identify those symptomatic patients needing more extensive diagnostic testing.