Does hemiparetic dorsiflexion in swing phase depend on spasticity?

This study quantified dorsiflexor and plantar flexor (PF) spasticity, and agonist and antagonist recruitment (cocontractions) during the swing phase of gait in individuals with hemiparesis with and without prior tibial neurotomy, investigating the role of spastic cocontraction versus spasticity in limiting dorsiflexion (DF).

Eleven hemiparetic subjects and 11 controls walking at comfortable and slow velocities underwent kinematic and electromyographic (EMG) analysis of PF and DF muscles. Five of the hemiparetic subjects had undergone tibial nerve neurotomy, which eliminates PF spasticity. Key metrics included ankle dorsiflexion, tibialis anterior recruitment, and coefficients of antagonist activation of gastrocnemius medialis and soleus during swing. Spasticity was assessed using the Tardieu scale.

Controls walking at slow speed showed similar velocity as hemiparetic subjects. Hemiparetic subjects showed reduced ankle dorsiflexion despite higher tibialis anterior recruitment, increased plantar flexor cocontraction before any dorsiflexion, even in neurotomy patients without spasticity.

Increased PF cocontraction persists even in the absence of spasticity, limiting dorsiflexion during swing. Spastic cocontraction, not spasticity, is a primary factor impairing active DF.

These findings emphasize that targeting spastic cocontraction of plantar flexors may be crucial for improving dorsiflexion and gait rehabilitation in hemiparetic patients, instead of addressing spasticity.