Relative bone mineral density measured by metacarpal index (MCI) and chronic spinal syndromes: an epidemiological...

The results of previous studies on the association between bone mineral density (BMD) and chronic spinal syndromes have been contradictory. Therefore, we studied relative BMD measured by the metacarpal index (MCI) and its associations with chronic neck and low-back syndromes and diffuse idiopathic skeletal hyperostosis (DISH).

A population sample of 8000 Finns aged 30 years and over was invited to a comprehensive health examination in 1978-1980; 90% complied. In the clinical phase, a trained physician diagnosed chronic neck and low-back syndromes. Hand and chest radiographs were taken from 3568 participants to determine the MCI and to diagnose DISH. Of these, 340 subjects were re-examined clinically in 2000.

After adjusting for potential confounding factors, a high MCI showed a significant cross-sectional association with chronic neck syndrome and DISH. The odds ratio (OR) per increment of one standard deviation (0.1) of MCI for chronic neck syndrome was 1.33 [95% confidence interval (CI) 1.21-1.47] and for DISH 1.29 (95% CI 1.04-1.60). No association was found between MCI and chronic low-back syndrome. In the follow-up setting, however, baseline MCI did not predict the incidence of chronic neck or low-back syndromes.

Relative BMD is directly proportional to the prevalence of chronic neck syndrome. Further studies are needed to clarify the mechanisms of the association. The close association found between high relative BMD and DISH suggests a joint metabolic factor, which needs to be studied further to determine its effects on bones and intervertebral discs.