Intramuscular neural distribution of the soleus for botulinum neurotoxin injection: application to spasticity

Understanding the nerve distribution within the soleus muscle concerning anatomical landmarks is crucial for botulinum neurotoxin injections in managing spasticity. This study advocates an anatomically informed approach for administering botulinum neurotoxin injections in the soleus muscle. Utilizing a modified Sihler's method, investigation encompassed both soleus muscles (20 specimens), revealing the distribution of nerves within concerning a transverse line crossing the fibular head and superior margin of the calcaneal tuberosity. Intramuscular nerve distribution within the soleus muscle displayed prominent patterns in zone 5 for the lateral portion, zone 3 for the middle portion, and zone 5 for the medial portion. Our suggestion is to target botulinum neurotoxin injections towards the areas with the most prominent nerve distribution, specifically zone 5 in the lateral part, zone 3 in the middle, and zone 5 in the medial part of the soleus muscle. Following these guidelines, clinicians can ensure minimal doses and avoid adverse effects like gait issues, antibody production, and bruising due to multiple injections. These findings can also be adapted and utilized in electromyography.