Accuracy of botulinum toxin type A injection into the gastrocnemius muscle of adults with spastic equinus: manual needle placement and electrical stimulation guidance compared using ultrasonography

Objective: To investigate the accuracy of manual needle placement and electrical stimulation guidance, compared using ultrasonography, for injection of botulinum toxin type A into the gastrocnemius muscle of adults with spastic equinus. Design: Prospective clinical study. Subjects: A total of 81 adults with stroke who were scheduled to receive botulinum toxin type A injection into the gastrocnemius muscle. Methods: After randomization into two groups, each patient was injected into two sites at each head of the gastrocnemius muscle. The manual needle placement group (n = 42) underwent injections using anatomical landmarks and palpation. The electrical stimulation guidance group (n = 39) underwent injections under electrical stimulation guidance. The accuracy of needle placement and muscle thickness at each injection site were compared by means of ultrasonography. Results: The overall accuracy of manual needle placement and electrical stimulation guidance, measured using ultrasonography, was significantly higher for the gastrocnemius medialis than for the lateralis (92.0% vs 79.0%). The gastrocnemius medialis was significantly thicker than the lateralis (mean 13.25 mm (standard deviation (SD) 1.86 mm) vs 10.84 mm (SD 1.52 mm). Conclusion: Electrical stimulation guidance may be useful for injections into the gastrocnemius lateralis of adults with spastic equinus. However, neither manual needle placement nor electrical stimulation guidance showed complete accuracy, when measured using ultrasonography.