A 28-year-old man with chronic low back pain and morning stiffness has a pelvic radiograph showing bilateral symmetric sacroiliitis with subchondral sclerosis and pseudo-widening of the sacroiliac joints. Which additional spinal finding would be most characteristic of advanced disease?

• A Osteophytes projecting horizontally from vertebral endplates
• B Syndesmophytes forming a bamboo spine ✓
• C Anterior longitudinal ligament calcification spanning four or more levels with preserved disc spaces
• D Vertebral body compression fractures at multiple thoracic levels

Explanation

Ankylosing spondylitis produces thin, vertical, marginal syndesmophytes from ossification of the outer annulus fibrosus, giving the bamboo spine appearance in advanced disease. Option C describes diffuse idiopathic skeletal hyperostosis, which typically affects older patients, spares the sacroiliac joints, and shows thick flowing ossification. Horizontal osteophytes indicate degenerative disc disease.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.