‘Does surgical management of the hand in children with unilateral spastic cerebral palsy affect muscle coordination and quality of reaching?’

Abstract

SIR–Our recent review on the effect of surgery of the spastic hand of children with cerebral palsy (CP) indicated that only studies with a low level of evidence were available, i.e. series of cases.1 The existing information indicated that surgery seems to have a positive effect on supination and dorsiflexion of the wrist, may improve grip strategy, and may induce an increase of the repertoire of grips and spontaneous use of the hand. The effect of surgery of the spastic hand on muscle coordination had only been addressed by three studies in a relatively systematic way.2–4 Unfortunately, it remained unclear, whether the putatively better hand function was the result of a better positioning of the hand and fingers and/or changes in muscle coordination induced by tendon transfer. Therefore, we started a pilot study in order to obtain insight into changes in muscle coordination and quality of reaching movements after surgical muscle transfers of the upper extremity in adolescents with unilateral CP. We hypothesised that surgery would result in more coordinated and more efficient muscle recruitment, i.e. in lower muscle activation rates, a reduction in recruitment of all arm muscles in concert, and in a temporal coordination which more closely resembles that of typically developing adolescents.4–7 In addition we evaluated whether surgery would result in qualitative improvement of motor behaviour during reaching. Three adolescents with unilateral CP who had surgery for their spastic hand to improve grip strategy and functional use of the paretic hand were studied. Hand posture, movement quality, and muscle coordination during a simple reaching task were assessed preoperatively and three times during the first postoperative year. Six age-matched typically developing adolescents had a single assessment to attain normative electromyography (EMG) data. Surgical procedures and patient characteristics are summarized in Table I.8–10 Postoperative treatment consisted of 5 weeks plaster immobilization, followed by a period of 6 weeks during which a removable splint was worn and intensive occupational therapy was applied. EMG was recorded continuously with bipolar surface electrodes of the following muscles: biceps brachii, triceps brachii, wrist extensors, and wrist flexors. A computer algorithm was used for the detection of phasic muscle activity.11 The analysis focused on (1) muscle activation rate, i.e. percentage of trials during which a muscle was activated; (2) ‘In concert’ muscle activation rate, i.e. percentage of trials during which all muscles were recruited; (3) percentage of trials during which a specific muscle was the ‘prime mover’; (4) onset latency of muscle activation; and (5) sequence of muscle activation: percentage of trials during which the sequence of activation consisted of (a) wrist Extensors, (b) biceps Brachii, and (c) wrist Flexors (EBF-sequence). The participants and their parents gave written informed consent and the procedures were approved by the ethics committee of the University Medical Center in Groningen. The operated hand showed in all three participants at 3 to 12 months postoperatively improvement in hand position and movement quality of wrist and fingers. This finding is in agreement with literature reports.12–15 The EMG-data indicated that surgery did not affect the rate of isolated or in concert muscle recruitment, the nature of the ‘prime mover’, or onset latencies. It did however affect muscle recruitment order: the atypical EBF-recruitment order decreased from 55% prior to surgery to 30%, 10%, and 10% at 3, 6, and 12 months respectively after the operation (Friedman: p=0.04. Fig. 1). Wrist Extensors, biceps Brachii, and wrist Flexors. (EBF)-sequence of non-dominant extremity of typically developing adolescents and adolescents with cerebral palsy pre -and post-operative. The findings of this pilot study suggest that surgery of the spastic hand does not only result in improved hand position, but also in a better quality of wrist and finger movements and a reduction of an atypical recruitment order of arm muscles. The latter may indicate that improved hand position may improve a person’s capacity to select a more efficient strategy out of the motor repertoire.5 Further investigation into the functional consequences of surgery of the spastic hand is highly recommended.