Classification of gastrocnemius muscle hypertrophy for personalized botulinum toxin type A treatment

Background: Owing to its safety and convenience, botulinum toxin type A (BoNtA) has become a first-choice treatment for contouring calf muscle asymmetries or deformities. Different injection methods and dosages have been discussed in the literature, but a standardized BoNtA treatment remains unclear.

Aims: This study aimed to classify gastrocnemius muscle hypertrophy (GMH) through multiple measurements to provide a personalized BoNtA treatment protocol.

Methods: The measurements combining of gastrocnemius muscle (GM) contour, max leg circumference and GM thickness was applied to classify different type of GMH in a normal population. Based on these findings, a personalized BoNtA treatment protocol was determined and evaluated regarding max leg circumference, GM thickness, the position of max leg circumference, patient and doctor satisfaction rate, and complications.

Results: A total of 100 GMH were classified into two bulging types (bilateral-bulging type and unilateral-bulging type) and two categories (moderate GMH and severe GMH). 40 cases were treated with personalized BoNtA injection methods ("Even" or "Intense"method) and dosages (300 or 400 units). Follow-up examinations at 1, 3, and 6 months after treatment. Max leg circumference and GM thickness decreased significantly and the position of max leg circumference rose prominently during treatment (2.56 $\pm$ 1.93; p $<$ 0.05). The overall patient satisfaction rate was 70%-100%. No serious complications occurred.

Conclusions: We identify four groups of GMH through several measurements and outline a personalized BoNtA treatment for each type. This recommended protocol may improve the therapeutic outcomes and patient satisfaction after treatment.