Botulinum toxin injection site localization for the tibialis posterior muscle.

Thirty-one cadaveric lower limbs were dissected to identify the innervation of the tibialis posterior muscle to aid localization of the injection site for botulinum toxin for the treatment of an equinovarus deformity. A posterior midline surface-anatomy axis was defined from the level of the head of the fibula proximally to the intermalleolar axis distally. The nerve to tibialis posterior branched from the tibial trunk 13.4% down this axis and entered the muscle 22.1% along the same axis, within 1 cm of the midline. We also report the use of ultrasound for muscle localization at the level of the anatomically defined motor point.