Is the Outcome of Diagnostic Nerve Block Related to Spastic Muscle Echo Intensity? A Retrospective Observational Study on Patients with Spastic Equinovarus Foot

Abstract

Objective: To investigate the relationship between spastic calf muscles echo intensity and the outcome of tibial nerve motor branches selective block in patients with spastic equinovarus foot.
Design: Retrospective observational study. Patients: Forty-eight patients with spastic equinovarus foot.
Methods: Each patient was given selective diagnostic nerve block (lidocaine 2% perineural injection) of the tibial nerve motor branches. All patients were evaluated before and after block. Outcomes were: spastic calf muscles echo intensity measured with the Heckmatt scale; affected ankle dorsiflexion passive range of motion; calf muscles spasticity measured with the modified Ashworth scale and the Tardieu scale (grade and angle).
Results: Regarding the outcome of tibial nerve selective diagnostic block (difference between pre- and post-block condition), Spearman’s correlation showed a significant inverse association of the spastic calf muscles echo intensity with the affected ankle dorsiflexion passive range of motion (p = 0.045; ρ = 00–0.269), modified Ashworth scale score (p = 0.014; ρ = –0.327), Tardieu grade (p = 0.008; ρ = –0.352) and Tardieu angle (p = 0.043; ρ = –0.306).
Conclusion: These findings support the hypothesis that patients with spastic equinovarus foot with higher spastic calf muscles echo intensity have a poor response to selective nerve block of the tibial nerve motor branches.

LAY ABSTRACT
This study reviewed data from 48 patients with spastic equinovarus foot in order to investigate the relationship between spastic calf muscles echo intensity (which indicates the degree of muscular fibrosis) and the outcome of tibial nerve motor branches diagnostic block (which temporarily relieves focal muscle overactivity). Outcome was the response to nerve block as to passive motility of the affected ankle and overactivity of the calf muscles. All patients were evaluated before and after the nerve block. A significant inverse association was found for the outcome of selective diagnostic nerve block of the tibial nerve motor branches with their respectively supplied spastic calf muscles (i.e. gastrocnemius medialis and lateralis, soleus and tibialis posterior) echo intensity. These results support the hypothesis that the degree of spastic muscle fibrosis may reduce the response to selective diagnostic nerve block in patients with spastic equinovarus foot.