Object/wrist movements during manipulation in children with cerebral palsy

The kinematics of the wrist and a manipulated object were studied in a posting task in 30 control, eight hemiplegic and 10 diplegic children. Statistical analyses using ‘mixed’ models examined the effects of subject group, hand, object shape and repeated trials, together with all possible interaction terms. During transport to the posting hole, the number of significant peaks/troughs in the velocity/time profile of the wrist in the transport (‘z’) direction were increased in subjects with cerebral palsy, as were adjustment error and the distances moved by the object relative to the wrist, reflecting more unpredictable object movement. In the placing phase, relative object/wrist normalized ‘z’ distances and number of wrist ‘z’ velocity peaks increased with increasing object complexity, reflecting the need for more adjustment movements. The number of wrist ‘z’ velocity peaks/troughs and adjustment error were increased in cerebral palsy subjects, reflecting ineffective adjustment. Relative object/wrist distances and number of wrist ‘z’ velocity troughs were reduced in both phases with repeated trials. It is suggested that such variables may provide a quantitative measure of poor movement ‘quality’ in children with Cerebral Palsy and that these findings reflect reduced mechanical stability of the hand and arm during movement.