Obesity and calcification of the ligaments of the spine: a comprehensive CT analysis of the entire spine in a random trauma population

Background Context: Obesity, which is currently surging to epidemic levels within the United States, has been linked to hyperostotic conditions like diffuse idiopathic skeletal hyperostosis (DISH) and ossification of the posterior longitudinal ligament (OPLL). Excess adipose tissue and insulin-resistance may cause a systemic increase in serum levels of proinflammatory cytokines and these signals can affect bone metabolism. Spinal ligaments and discs may have receptors for these signaling molecules. Anecdotal observations at this institution suggested that there is a clinically important subset of younger patients with obesity and multilevel stenosis in the presence of unusual calcification of the spinal ligaments that is distinct from DISH. Purpose: To determine if there is an association between truncal obesity and calcifications of the spine in nonelderly adults. Study Design/Setting: This is a retrospective analysis of 214 sequential trauma patients between the ages of 29 and 50. Patients’ age, sex, truncal obesity, history of hypertension, and diabetes were assessed for association with ligamentous calcification of the spine. Patient Sample: Sequential trauma patients were chosen from our institution's trauma database between 2006 and 2007. Methods: Full spine computed tomography (CT) imaging was examined for bone formation in the region of the anterior longitudinal ligament (ALL) and annulus, posterior longitudinal ligament (PLL) and annulus, and the ligamentum flavum (LF). Visceral and subcutaneous abdominal fat were also evaluated. The authors report no study funding sources or conflicts of interest. Outcome Measures: Calcification of the ALL, PLL, and LF were assigned a score at each level and then combined for a total calcification score (TCS) for the entire spine. Obesity was estimated using a truncal body mass index (TBMI) by using a previously validated CT derived truncal total adiposity volume (TAV). Results: ALL calcification was associated with age, male gender, hypertension, and increased adiposity. PLL calcification was significantly associated with age and hypertension. LF calcification was only associated with increased obesity. Conclusions: In our analysis of nonelderly patients, LF calcification was independently associated with truncal obesity. This implies obesity plays a greater role in calcification than could be accounted for by simply age-related degeneration or gender.