Thoracic spondylotic myelopathy in diffuse idiopathic skeletal hyperostosis: a comparative study

Background To explore the characteristics and clinical management of thoracic spinal stenosis with diffuse idiopathic skeletal hyperostosis (DISH). Methods The patients diagnosed with thoracic spondylotic myelopathy who underwent spinal decompression and fusion surgery in a single center between 2012 and 2020 were retrospectively analyzed. All the patients were followed up for at least 2 years. Patients were classified into DISH and non-DISH groups. Demographic, radiographic and clinical parameters were compared between the two groups. Results A total of 100 thoracic spondylotic myelopathy patients were included in the study. 22 patients were diagnosed with DISH. The proportion of male patients in the DISH group was higher, and the average BMI was larger. The incidence of upper thoracic vertebrae with ossification of posterior longitudinal ligament (OPLL) ( P < 0.05) and lumbar spine with ossification of ligamentum flavum (OLF) was higher ( P < 0.05) in DISH the group. The proportion of patients received staged surgery is higher in the DISH group ( P < 0.1). There were no significant differences between the two groups in the amount of surgical bleeding, the ratio of cerebrospinal fluid leakage, the time duration of drainage tube placement and the JOA scores. Conclusion Thoracic spinal stenosis with DISH occurred more in male patients with larger BMI. The posterior decompression and fusion surgery could achieve comparable satisfying clinical outcomes between DISH and non-DISH patients. More proportion of patients received staged surgery in the DISH group; the underline mechanism may be DISH caused more OPLL in the upper thoracic spine and more OLF in the lumbar spine because of mechanical stress.