Epidemiology of Schmorl's Node in the Thoracic Spine: A Subtype Analysis.

STUDY DESIGN: Retrospective observational study.

OBJECTIVE: To describe the epidemiology of Schmorl's nodes (SN) of primarily developmental cause (SNd) and SN of primarily acquired cause (SNa) separately in the thoracic spine in subjects aged 35-90 years old.

SUMMARY OF BACKGROUND DATA: The epidemiology of SN and its relationship with age and gender remain controversial. Based on a pathophysiological hypothesis and the different morphological characteristics, two subtypes of SN may exist and should be considered separately.

PATIENTS AND METHODS: Chest CT scans of subjects who came to our institution for health check aged 35-90 years old were retrospectively reviewed. Presence or absence of SN was recorded for each thoracic vertebra. The SNs were further classified into SNd and SNa. The prevalence, location and relationship with age, gender and bone mineral density (BMD) were evaluated separately for the two subtypes.

RESULTS: Of the 848 subjects (407 female, mean age, 53±12.2 y) included, 15.7% had SNs. Of the 303 SNs, 49.2% were SNd and 48.5% were SNa. Aging increased the prevalence of SNa while it was not related to the prevalence of SNd. Males had significantly more SNd than females (11.3% vs 4.7%, P<0.001), while the prevalence of SNa was not different between the two genders (10.2% vs 9.1%, P=0.666). A similar distribution of SNd and SNa among thoracic vertebral levels was appreciated, with T9 most frequently involved. Subjects with SNa had lower lumbar BMD than controls (P=0.006), while no significant difference in BMD was found between subjects with SNd and controls (P=0.166).

CONCLUSIONS: The clinical characteristics of SN differ based on the developmental and acquired subtype, including the relationship with age, gender and BMD. The subtypes may be considered as distinct clinical entities as a result.