SCHMORL NODES: AN EPIDEMIOLOGICAL PERSPECTIVE.

Abstract

Background: The epidemiology of Schmorl nodes is based on post-mortem investigations. The proposed pathogenesis of the focal nodes is a bulging of the disc into the vertebral body depending of the degree of osteoporosis. Secondar peripheral osteophytes are formed at the annular insertion.

Study design: A cross sectional epidemiological study of 4151 participants of the Copenhagen Osteoarthritis Study in 1993 with a 13 years follow with the Roland-Morris (R-MQ) back pain questionnaire.

In 1993 standardized, lateral radiographs of the lumbar spine were recorded and the bone mineral density (BMD) was estimated by digital x-ray radiogrammetry of standardised hand x-rays.

Methods: Statistical correlations were made between Schmorl nodes and low back pain in 1993, the R-MQ score, BMD and the presence of osteophytes, disc degeneration and endplate sclerosis.

Results: There were 2610 women and 1538 men. At follow up 1190 women and 674 responded. In 196 cases one or more Schmorl nodes in the lumbar spine were found (women 3.7 %, men 6.5 %). A decreasing prevalence of Schmorl nodes by ages was found in both genders (p< 0.000). At the time of the radiographic examination participants with Schmorl nodes clamed of low back pain (p=0.003). The presence of nodes was without relation to osteophytosis, intervertebral disc degeneration or sclerosis of endplates (p> 0.14) in 1993. Neither was the R-MQ score at follow-up related to Schmorls nodes(p> 0.26). The presence of nodes was associated with higher BMD (mean 0.50 (SD 0.079) versus 0.53 (SD 0.081)(p=0.000), however the difference disappeared taking into account age at examination.

Conclusion: This large scaled epidemiological study cannot confirm the hitherto hold opinion of the implication of the Schmorls nodes. The nodes are not associated with radiological degeneration and osteoporosis neither are they a predictor of lower back pain later in life.