Management of scoliosis with special seating for the non-ambulant spastic cerebral palsy population--a biomechanical study.

OBJECTIVE To investigate the effects of special seating on lateral spinal curvature in the non-ambulant spastic cerebral palsy population with scoliosis. DESIGN Prospective study with matched pairs (same subject pre- and post-intervention). BACKGROUND It is thought that special seating can improve the sitting posture of individuals with spastic cerebral palsy. However, there is little known about how the seating can affect a scoliosis. METHOD The shape of the spine was measured with subjects sitting in an assessment chair with a clear backrest. The measurement recorded was the "spinous process angle", an approximation to the Cobb angle. The forces exerted on the subject by the chair were measured by electrical resistance strain gauged transducers attached to the lateral support pads and seat base. Measurements were taken with three alternative arrangements of lateral support pads: upper body unsupported in configuration 1; two lateral pads at the same height in configuration 2; body supported by a 3-point force system in configuration 3. RESULTS Configuration 3 gave a mean correction of +35% in the spinous process angle compared to configuration 1 (P=0.000) and the forces applied through the two lateral thoracic pads were, on average, of similar magnitude (mean values of 51 and 47 N). In comparison, for configuration 2 the mean correction was only +18.7% (P=0.004) and on average the pad on the concave side of the scoliosis applied a much larger force to the chest wall than the pad on the convex side (mean values of 36 and 17 N respectively). CONCLUSIONS Significant static correction of the scoliotic spine can be achieved with an arrangement of lateral pads on a seating system that applies a 3-point force system to the sides of the body. RELEVANCE The results suggest that the position of the lateral pads on a special seating system is important and, by the careful configuration of these supports, significant correction of a scoliosis can be obtained for a person with spastic cerebral palsy. Also the methodology and equipment from this study are potentially useful for the assessment and fitting of special seating for individuals with scoliosis.