Sitting balance in spinal deformity.

A computerized pressure plate system was used to analyze the sitting pressure distribution and balance of 100 subjects with both normal and abnormal spines. Normal subjects had a balanced sitting posture with the weight taken evenly on each ischial tuberosity. Patients with idiopathic scoliosis showed significant sitting imbalance especially in the presence of lumbar curves. Bracing improved the sitting balance and stability in most patients. Abnormal sitting patterns were seen with the spinal deformities of myelodysplasia or cerebral palsy. Some patients with severe scoliosis had very asymmetric patterns, which correlated with their loss of sitting stability. The kyphosis of myelodysplasia produced an abnormal tripod sitting pattern due to pelvic flexion and a hyperlordosis of cerebral palsy a pubic sitting pattern due to pelvic extension. The patients studied after spinal fusion also had poor sitting balance and occasionally persisting decubitus ulceration.