Torsional Anatomy of the Lower Limb: The Appearance of Anatomy in Hemispastic Position.

OBJECTIVE: The aim of the study was to determine whether there are relevant anatomical variations to the typical injection sites for antispasticity procedures in the lower limb.

METHODS: Sonographic images were obtained at traditional injection locations for spasticity in the lower limb. Images were recorded in neutral and contracted postures. Doppler imaging was obtained for sites that contained vasculature. The images were analyzed, and schematics were created that highlighted relevant findings.

RESULTS: The adductor longus in commonly used injection sites was close to vasculature making accidental injection of the latter a higher risk. The sciatic nerve was vulnerable to injections at the proximal biceps femoris injection side if injected too deeply. Hamstring injection sites can be adjusted to the midline to improve accuracy. The proximity of the tibial nerve to the flexor hallucis longus and the deep fibular nerve to the extensor hallucis longus puts these nerves at risk for accidental injection.

DISCUSSION: Contracted posture results in altered positions of lower extremity muscles that could lead to inadvertent neurovascular injection or decreased efficacy with injections. Findings in this study may be helpful for planning and executing injections to reduce spasticity in the lower extremity.

CONCLUSIONS: Sonographic imaging allows a better localization of muscles associated with spasticity and can instruct the clinician to alter usual injection pathways. This article documents visual evidence that previous assumptions for injection strategies require updating.