Muscle atrophy in ankylosing spondylitis: CT demonstration.

The CT demonstration of gross atrophy of the posterior spinal muscles and the left psoas muscle in a patient with chronic ankylosing spondylitis is reported. The muscle atrophy appeared to be related to gross total ankylosis of the thoracic and lumbar spine and severe unilateral involvement of the left hip joint. This observation suggests a relationship between muscle atrophy, spinal fixation, and reduced joint mobility.