Sunday, July 5, 2009

Spine fracture in Ankylosing Spondylitis

38 year old male patient with ankylosing spondylitis met with mild trauma following which he presented with para paresis, Sagittal T2 weighted MR image showing anterior displacement of C6 over C7 (Arrow head) and multiple syndesmophytes in all the cervical levels (short arrow). There is cord hyperintensity at the levels of C6, C7 and D1 suggestive of cord contusion due to fracture.

The diffuse paraspinal ossification and inflammatory osteitis of advanced ankylosing spondylitis creates a fused, brittle spine that is susceptible to fracture. Even minor trauma can produce an unstable injury as a result of disruption of the ossified supporting ligaments.

Thoracolumbar fractures are reported less frequently than cervical injuries in patients with ankylosing spondylitis.Three recognized patterns are simple vertebral compression fractures, transversely oriented shear fractures, and stress fractures associated with pseudoarthrosis. Transversely oriented shear fractures are acute fractures of the ankylosed spine that invariably disrupt the ossified supporting ligaments and usually traverse the disk space. Disruption of all three columns of the spine predisposes the fracture to displacement and neurologic injury. Stress fractures associated with pseudoarthrosis are subacute injuries that constitute part of the spectrum of spondylodiscitis, a destructive discovertebral (“Andersson”) lesion, that tends to occur in the thoracolumbar region. End-plate erosions and disk height changes, with vertebral sclerosis or osteolysis, can be seen radiographically.

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