Spinal lesions due to hyperextension in ankylosing spondylitis

The authors review the literature and discuss the biomechanical aspects of extension fractures of the spine in ankylosing spondylitis and report 3 cases. They conclude that, although such lesions are rare, patients with ankylosing spondylitis who sustain such trauma must be subjected to thorough radiological examination. The milder lesions have a favourable prognosis, but those involving dislocation are extremely dangerous, both because of the frequent appearance of immediate or delayed medullary complications and because of the high incidence of pseudarthrosis.