Medial gastrocnemius fascicle function during walking in children with cerebral palsy following gastrocnemius lengthening surgery

Abstract

Introduction: The medial gastrocnemius (MG) muscle contracts eccentrically during walking in children with cerebral palsy (CP) and equinus gait. Gastrocnemius lengthening surgery is used to improve equinus gait however lower limb muscle function during walking following this surgical intervention remains unknown. This study investigated the function of the MG muscle prior to and following recovery from gastrocnemius lengthening surgery for an equinus gait pattern in children with CP. Patients and method: Seven children with CP (age 11, SD 1y, 5 males, hemiplegia=5, diplegia=2, GMFCS levels I=4, II=3) undertook full body 3D gait analysis and simultaneous Bmode ultrasound images of the MG fascicles during level walking prior to gastrocnemius lengthening surgery, and following surgery and the recovery period. Fascicle lengths were analysed using a semi-automated tracking algorithm. Pairedsample t-tests were used to compare differences pre- and post-surgery, (p<0.05). Results: Post-surgery MG fascicles lengthened less during midstance, 1.2 (1.1) mm versus 2.5 (1.0) mm, p=0.04. Although fascicle shortening during late stance was greater post-surgery, 2.3 (1.2) mm versus 0.1 (0.4) mm, normalised ankle power during push-off was significantly less, 0.5 (0.1) W/kg versus 0.8 (0.1) W/kg, p=0.01. Conclusion: A decrease in magnitude of MG muscle fascicle lengthening during mid-stance gait following gastrocnemius lengthening surgery is consistent with reduced ankle passive stiffness and may reduce muscle damage and soreness associated with repeated eccentric contractions. The greater contribution to force generation from increased muscle contraction during late-stance may be lost during force transfer through altered muscle and tendon tissue following surgery, and impede ankle push-off power.L6162709072017-05-23 <br />