An association between the flat back and postpolio syndromes: a report of three cases.

The cases of three patients with a history of paralytic poliomyelitis in childhood who developed the flat back syndrome before or after spinal fusion for degenerative disease as adults were reviewed. The flat back syndrome, a combination of an inability to stand erect because of forward flexion of the trunk and pain in the low back and/or legs, typically occurs in the setting of decreased lumbar lordosis as a result of distraction instrumentation of the spine for scoliosis, vertebral fracture, or degenerative disease. Focus was placed on determining the factors responsible for the development and/or persistence of the flat back syndrome in these patients despite maintenance of, or partial operative restoration of, lumbar lordosis. Considering the essential role that the trunk extensor musculature plays in maintaining upright posture, it may be that a new onset of weakness (postpolio syndrome) in this musculature represents a major contributing factor to the flat back syndrome in these patients. Spine surgeons considering operative procedures in patients with a remote history of paralytic poliomyelitis should be aware of the possible increased risk of the flat back syndrome in this population of patients.