Changes in tibialis anterior muscle activity following tibial nerve block in adults with spastic equinovarus foot: an observational pilot study

Objective: To investigate changes in tibialis anterior and gastrocnemius medialis activity during walking following a diagnostic nerve block of the tibial nerve in patients with spastic equinovarus foot. Design: Observational pilot study. Patients: Thirteen adult patients (10 males, 3 females) with spastic equinovarus foot due to stroke or traumatic brain injury. Methods: All patients underwent a diagnostic nerve block of the tibial nerve main trunk. Clinical assessments included passive and active ankle range of motion, spasticity grading using the Modified Ashworth Scale and the Tardieu Scale, and muscle strength evaluation. Surface electromyography was recorded during gait to analyse muscle activation and coactivation patterns before and after the procedure. Results: Passive ankle dorsiflexion significantly improved after the nerve block. Spasticity scores decreased, while active range of motion and Tardieu angle (passive range of motion during slow stretch - angle at which resistance is first felt during fastest stretch) showed trends toward improvement. Electromyographic analysis revealed reduced activation of both tibialis anterior and gastrocnemius medialis, along with a significant decrease in coactivation. Conclusion: Diagnostic nerve block of the tibial nerve effectively reduces spasticity and alters antagonist muscle activity, supporting its role in personalized assessment and treatment planning for spastic equinovarus foot.