A 50-year-old man with ankylosing spondylitis presents with acute severe back pain after a minor fall. Radiograph shows diffuse ossification of the spine ('bamboo spine'). The fracture most feared in this setting occurs at:
- A The anterior longitudinal ligament ossification (chalk-stick fracture) ✓
- B The sacroiliac joint posteriorly
- C The discovertebral junction through a hyperextension mechanism (Andersson lesion)
- D The spinous processes due to flexion injury
Explanation
In ankylosing spondylitis with a rigid 'bamboo spine,' the entire ossified spinal column behaves like a long bone. Minor trauma can produce transverse 'chalk-stick' fractures through the ossified disc and adjacent vertebral bodies (or through the vertebral body itself), typically at the cervicothoracic junction. These fractures are highly unstable (three-column injury) despite appearing minor on X-ray, carry high risk of spinal cord injury, and require urgent MRI and surgical stabilization with long-segment instrumentation. CT/MRI are essential as plain X-ray may miss these fractures.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.