Cervical cord injury in patients with ankylosed spines: Progressive paraplegia in two patients after posterior fusion without decompression

Study Design. Case report and clinical discussion. Objective. To describe technical pitfall to treat 2 cervical cord injuries, including dislocations in patients with ankylosed spine due to diffuse idiopathic skeletal hyperostosis (DISH) or ossification of the posterior longitudinal ligament (OPLL). Summary of Background Data. DISH and OPLL are disease processes similar in pathology, which can lead to unexpected fractures due to low-energy trauma. In reported cases of fracture of the ankylosed spine in patients with DISH or OPLL, increasing lever arm and a grossly unstable fracture occurred. However, the actual surgical intervention for these fractures and spinal cord injuries was not discussed. Methods. We report 2 cervical cord injuries, including dislocations in patients with ankylosed spine due to DISH or OPLL. Results. Two patients underwent posterior fusion without decompression; however, postoperative progressive paraplegia still occurred. There were 3 points in common: these patients had ankylosed spines due to DISH or OPLL; they were elderly and had spinal canal stenosis; and after undergoing posterior fusion without decompression, their bilateral, lower extremity palsies worsened after surgery. Cervical alignment was slightly different after posterior fusion, and this change concentrated in one segment because adjacent vertebral bodies were ankylosed, and thus, immoveable. Additionally, this stress caused infolding of the ligamentum flavum with resultant spinal cord compression. Conclusion. In these cases, we recommend posterior fusion and decompression such as laminoplasty to avoid worsening palsy.