Nontraumatic fracture of the thoracic spine in ankylosing spondylitis.

SSEOUS BRIDGING beneath the anterior 0 spinal ligament is a feature of ankylosing spondylitis ( A S ) . When extensive this is usually associated with ankylosis of the apophyseal joints, resulting in a poker spine, or virtually complete fusion of the bony structures In 2 such cases, rupture or fracture of a calcified anterior thoracic ligament occurred following automobile accidents.l In each instance the involved interspace opened anteriorly without anterior-posterior displacement of the vertebrae. The present report of a thoracic interspace fracture in a rigid spine involved by AS is singular in that displacement of adjacent vertebral bodies occurred. More remarkable, no history of external trauma was obtained.