Vertebral endplate abnormalities are highly associated with thoracic disc herniations in symptomatic patients

Abstract

Background: Lumbar disc herniations are common. Endplate abnormalities (e.g. Schmorl's node) have been noted to occur throughout the lumbar spine, with or without disc herniation. However, disc herniations of the thoracic spine and are often associated with neurological sequelae, frequently necessitating surgery which has a high incidence of complications. Unlike the lumbar spine, the mechanism of thoracic disc herniations is not well understood. Recently, a much thorough understanding of the endplate phenotype has been proposed that provides insight into the etiology and risk of disc changes. The following largescale study was performed in a cohort of symptomatic thoracic disc herniation patients to determine the relationship between such lesions and the role of endplate abnormalities as well as other MRI phenotypes. Methods: A retrospective review of a prospectively collected cohort of 161 adult patients who were diagnosed with symptomatic thoracic disc herniation and myelopathy requiring surgery from 2008 to 2012 at a single institute were assessed. Preoperative T2-weighted MRIs were assessed of the thoracic spine. Imaging phenotypes of black disc, disc space narrowing, disc herniations, Modic changes, endplate abnormalities, osteophytes and ossified longitudinal ligament were assessed from T1-L1. Results: There were 49% males and 51% females. Black disc was noted in 75% of patients, most prevalent at T8/9 (32%), T7/8 (29%) and T6/7 (27.3%). Disc space narrowing was noted in 31% of the patients, mainly occurring at T11/12 (6.8%), T8/9 (8.1%) and T6/7 (7%). Disc herniation was more prevalent at T11/12 (60%), T12/L1 (55%), T10/11 (50%), T8/9 (42.9%) and T9/10 (37%). Endplate abnormalities were noted in 84% of the patients, occurring primarily at T11/12 (48%), T9/10 (33%), T12/L1 (32%) and T10/11 (44%), and strongly associated with levels of disc herniation. Modic changes were noted in 32% of patients, primarily occurring at T6/7 (11%), T7/8 (11%), and T8/9 (10%). Osteophytes occurred in 4% of the patients and were more common at the lower thoracic spine at T10-L1. Ossified longitudinal ligament was noted in 20% of the patients, mainly noted at T6-T9. Discussion: This study represents one of the largest cohort of patients with symptomatic thoracic disc herniation and the imaging assessment of additional spinal phenotype patterns. Findings from this study have noted that endplate abnormalities are highly associated in patients with symptomatic thoracic pathology, mainly occurring at levels of disc herniations. Secondary degenerative phenotypes were also noted, mainly occurring in the lower thoracic spine but presenting with unique topographical and morphological patterns. Having a better understanding of the endplate phenotype and the occurrence of thoracic disc herniation may shed light into the etiology and mechanism of endplate and disc pathology, which may also shed light upon the prediction of future spinal conditions of the thoracic spine.