Medial gastrocnemius morphology after orthopedic surgery in a child with spastic cerebral palsy

To improve gait in children with spastic cerebral palsy (CP), the calf muscle can be surgically elongated, for instance with an incision at the muscle-tendon junction [1,2]. Previous studies showed that this procedure results in a larger ankle range of motion [1,2]. However, it is unclear whether the elongation originates from lengthening of the tendon, the muscle belly, or a combination of both. What is the effect of surgical elongation on the morphology of the medial gastrocnemius (MG) in a child with CP and how does the MG morphology of the child with CP relate to MG morphology of typically developing children (TD) before and after the surgery? Muscle-tendon unit (MTU), muscle belly, tendon, and fascicle lengths, pennation angle of the fascicles as well as muscle volume were determined with 3D ultrasound for a boy with spastic CP (13 years, GMFCS I) one week before and 21 weeks after surgery (including a period of intensive physiotherapy), and compared to reference data of 20 TD children (10±3 years). Morphological variables were collected with the foot positioned at an angle corresponding to a moment of 0 Nm. Lengths were normalized to tibia length and volume to body weight. One-sample t-tests were conducted to compare the CP case with TD reference data. Before surgery, ankle angle at 0 Nm, MTU length, muscle belly length, and muscle volume were significantly lower and tendon length longer in the child with CP compared to TD references (Fig. 1). Fascicle length and pennation angle were similar to TD. After surgery, the ankle angle at 0 Nm increased with 18° achieved by an increase in MTU, muscle belly and tendon length with 11%, 1% and 18% respectively. Fascicle length decreased with 16% and muscle volume and pennation angle increased with 8% and 62% respectively. After surgery, only MTU length was similar in CP compared to TD. In this case, the surgical elongation resulted more ankle dorsiflexion mainly due to tendon elongation. Despite the better overall MTU length, there was overall more atypical MG morphology. The simultaneous increase in muscle volume and reduced fascicle length could be explained by the combined effect of fascicle hypertrophy and increase in pennation angle. The increased ankle dorsiflexion and longer MTU length may have improved the child’s function during daily life and physiotherapy, thereby facilitating fascicle hypertrophy shown by the increase in muscle volume. Our results should be verified in a larger sample size and related to his gait pattern and capacity. Additionally, more insight in the healing process can be obtained with recurring follow-up measurements planned 1 year post-surgery. Fig. 1. Adaptations following surgical elongation of the medial gastrocnemius.Download : Download high-res image (87KB)Download : Download full-size image