OBJECTIVE Spinal cord injury (SCI) is a major complication of spinal fractures in patients with ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH). Due to the uncommon nature of these conditions, existing literature consists of relatively small case series without detailed neurological data. This study aims to investigate the incidence, predictors, and sequelae of SCI in patients with a traumatic fracture of the ankylosed spine. METHODS The study included all patients older than 18 years of age with AS or DISH who presented to two affiliated tertiary care centers between January 1, 1990, and January 1, 2016, and had a traumatic fracture of the spine. Factors associated with SCI after traumatic fracture were compared using Fisher's exact tests. Logistic regression was used for the analysis of predictive factors for SCI. For the comparison of probability of survival between patients with and without SCI, Kaplan-Meier methodology was used. RESULTS One hundred seventy-two patients with a traumatic fracture of an ankylosed spine were included. Fifty-seven patients (34.1%) had an SCI associated with the fracture. The cervical spine was the most fractured region for patients both with (77.2%) and without (51.4%) SCI. A cervical fracture (odds ratio [OR] 2.70, p = 0.024) and a spinal epidural hematoma (SEH) after fracture (OR 2.69, p = 0.013) were predictive of SCI. Eleven patients (19.3%) with SCI had delayed SCI (range 8-230 days). Of 44 patients with SCI and sufficient follow-up, 20 (45.5%) had neurological improvement after treatment. Early and late complication rates were significantly higher (p = 0.001 and p = 0.004) and hospital stay was significantly longer (p = 0.001) in patients with SCI. The probability of survival was significantly lower in the SCI group compared with the non-SCI group (p = 0.006). CONCLUSIONS The incidence of SCI was high after fracture of the spine in patients with AS and DISH. Predictive factors for SCI after fracture were a fracture in the cervical spine and an SEH following fracture. One-fifth of the patients with SCI had delayed SCI. Patients with SCI had more complications, a longer hospital stay, and a lower probability of survival. Less than half of the patients with SCI showed neurological improvement.
Keywords: AIS = ASIA Impairment Scale; AS = ankylosing spondylitis; ASIA = American Spinal Injury Association; BMI = body mass index; CCI = Charlson Comorbidity Index; CI = confidence interval; DISH = diffuse idiopathic skeletal hyperostosis; IQR = interquartile range; OR = odds ratio; SCI = spinal cord injury; SEH = spinal epidural hematoma; ankylosing spondylitis; diffuse idiopathic skeletal hyperostosis; mortality; neurologic improvement; spinal cord injury; spine fracture.