Differential diagnosis of back pain in patients with ankylosing spondylitis: instable cervical spine fracture

History and admission findings: A 65-year-old patient with long-standing ankylosing spondylitis (AS) complained of persistent pain in the right shoulder and the neck; elevation of the shoulder was impaired. The symptoms had started a week before admission after a fall. Physical examination revealed generally decreased mobility of an already hyperkyphotic cervical spine (CS) and decreased thoracic excursion. The paravertebral muscles were stiff. Clinical investigations: Because of the trauma extensive imaging procedures with conventional radiographs, magnetic resonance imaging (MRI) and computed tomography (CT) of the CS were performed. These showed a compression fracture of C5, detachment of the dorsal and ventral ligaments and a ventral dislocation of C4 with dislocation (Type C fracture). Treatment and course: After immediate consultation of the cooperating center for spinal surgery corpectomy of C5 and ventral fusion of C3-7 were performed on the same day, together with a dorsal transpedicular fusion. During the imaging procedures symptoms of a beginning paraplegia occurred. After successful surgery and early postoperative rehabilitation, the patient was discharged to an in-patient rehabiltation unit. At discharge, there was but a slight paresis of the right arm. Conclusion: Patients with AS and advanced spinal ankylosis are at increased risk of vertebral fracture after minor accidents. Regardless of the initial report of clinical symptoms it is mandatory to perform appropriate imaging procedures usually including MRI.