Relationship between spastic catch measurements and ankle joint movement in walking and hopping in children with cerebral palsy

Spasticity assessment is part of the management of children with cerebral palsy (CP), and often-recommended methods like the Modified Tardieu Scale (MTS) have been utilized in clinical practice [1]. MTS aligns with the traditional definition of spasticity: a velocity-dependent increase in the tonic stretch reflex [2]. However, the spastic catch angle of relaxed muscle might not be related to joint movement in dynamic tasks [3,4], such as walking or hopping. This study investigates the relevance of passively measured spastic catch angle to ankle movement in walking and hopping. Does the spastic catch stop the ankle movement similarly in hopping compared to the passive condition? Sixteen children (13.1 ± 2.5 years, GMFCS level 1) with unilateral spastic CP underwent 3D gait and hopping analysis in a motion analysis laboratory. 3D movement analysis measures included sagittal ankle angles, ankle angular velocities, and estimated calf muscle lengthening velocities during gait and a two-legged hopping task. Unilateral assessments of the ankle spastic catch angle (MTS) and maximum passive and active dorsiflexion angles (knee at 0° and 90°) were performed as clinical tests. Compared to walking (affected 15.5%/s and unaffected 25.2%/s), estimated gastrocnemius lengthening velocities were significantly higher in hopping (67.9%/s and 71.7%/s respectively, Fig. 1.A), indicating fast muscle stretch. However, this does not constrain the affected side ankle motion since the maximum ankle dorsiflexion was significantly greater in hopping than in clinical tests (p<0.001, Fig. 1.B). Peak ankle angular velocities during hopping were higher on both affected (513.6 °/s) and unaffected (537.5 °/s) sides compared to walking (124 °/s and 108 °/s, respectively). The hopping maximum dorsiflexion angle on the affected side correlated strongly with the spastic catch angle (r=0.739, p<0.001) and the passive dorsiflexion (r=0.687, p=0.005) but not significantly with the active dorsiflexion clinical test (r=0.428, p=0.098, Fig. 1.C). Fig. 1. A. Estimated gastrocnemius muscle lengthening velocity during hopping and gait. B. Ankle angle during hopping and gait compared with mean passive, active dorsiflexion, and spastic catch values. C. Associations between maximum dorsiflexion in hopping and dorsiflexion angles in clinical tests on the affected side gastrocnemius.Download : Download high-res image (79KB)Download : Download full-size image This study suggests that the spastic catch does not restrict joint movement in high-velocity dynamic tasks such as hopping, which challenges the relevance of the spastic catch angle measurement made at rest. On the other hand, there was an association between spastic catch, passive dorsiflexion angle, and maximum ankle dorsiflexion in hopping, suggesting that these two clinical measures may both be associated with ankle stiffness. Due to the complexity of spasticity, an assessment may need to produce multiple 'values' of spasticity to accurately reflect its effect on muscle function and joint biomechanics during functional movements.