Post-traumatic spinal hematoma in ankylosing spondylitis.

Purpose The purpose of this study is to examine the incidence, location, and magnetic resonance imaging (MRI) features of spinal epidural hematoma (SEH) and spinal subdural hematoma (SSH) in post-traumatic ankylosing spondylitis (AS) patients. Methods A total of 2256 consecutive referrals for urgent and emergency MRI scans of the spine over a period of eight years and nine months were manually reviewed for any mentions indicating axial ankylosis and post-traumatic spinal hematoma. We found 164 patients with ankylosed spines complicated by spinal fracture, of whom 32 had AS. Of the 132 excluded patients, 80 had diffuse idiopathic skeletal hyperostosis (DISH). The primary outcome was the presence of spinal hematoma, and the secondary outcome was spinal canal narrowing and spinal cord impingement. Two musculoskeletal radiologists and one fellow in musculoskeletal radiology reviewed the images for the presence of spinal hematoma and related signal characteristics, blinded to one another and initial reports. Results Of 28 post-traumatic AS patients, 19 had SEHs and five had spinal SSHs. There was a statistically significant difference between Frankel grades before and after surgery in respect of neurological improvement (p = 0.008). Patients who had radiologically proven spinal cord impingement showed more severe neurological deficits (p = 0.012). Hematomas with T1 heterogeneity showed a significantly increased delay (p = 0.047) between injury and imaging, while other signal characteristics were only approximate. Conclusions Both SEH and SSH are common complications in post-traumatic AS patients. Patients benefit from surgery, but the relevance of spinal hematoma as a separate factor causing neurological deficit remains unclear.