Science News: Management Of Spastic Equinovarus Foot in Children With Cerebral Palsy: An Evaluation of Anatomical Landmarks for Selective Nerve Blocks of the Tibial Nerve Motor Branches

Submitted by: Rebecca O’Bryan, MD

Citation: Picelli A, Di Censo R, Zadra A, Faccioli S, Smania N, Filippetti M. Management of spastic equinovarus foot in children with cerebral palsy: An evaluation of anatomical landmarks for selective nerve blocks of the tibial nerve motor branches. J Rehabil Med. 2023;55:jrm00370. Published 2023 Feb 20. doi:10.2340/jrm.v55.4538

Summary: This is a small observational study of 24 children aged 6-16 with cerebral palsy (CP) to define landmarks of tibial motor nerve branches for selective motor nerve blocks of the gastrocnemii, soleus, and tibialis posterior muscles to manage spastic equinovarus foot. Muscle spasticity was graded using the Modifed Ashworth Scale, as well as spastic calf via the Tardieu scale. Patients had never received botulinum toxin previously. The authors performed selective diagnostic nerve block of tibial motor nerve branches. Landmarks were targeted using ultrasound (US) and the location of motor branches was defined a as percentage of the affected leg length. Mean coordinates were: for the gastrocnemius medialis 2.5 ± 1.2% vertical (proximal), 1.0 ± 0.7% horizontal (medial), 1.5 ± 0.4% deep; for the gastrocnemius lateralis 2.3 ± 1.4% vertical (proximal), 1.1 ± 0.9% horizontal (lateral), 1.6 ± 0.4% deep; for the soleus 2.1 ± 0.9% vertical (distal), 0.9 ± 0.7% horizontal (lateral), 2.2 ± 0.6% deep; and for the tibialis posterior 2.6 ± 1.2% vertical (distal), 1.3 ± 1.1% horizontal (lateral), 3.0 ± 0.7% deep.  A significant correlation was found between the association of ankle dorsiflexion passive range of motion and the vertical coordinate for the gastrocnemius lateralis motor nerve branch. 

Comments: This is a very small, limited study, but the use of diagnostic nerve block (DNB) to determine spasticity vs contracture is a useful tool in evaluating candidacy for botulinum toxin. Use of landmarks with US in addition to EMG guidance may enhance targeting the motor branches of the tibial nerve in children with CP, in the context of less experience ultrasonographers. This study would be most relevant in providing some useful landmarks for those who are new to utilizing US in identifying the tibial motor nerve for DNB. This may be a helpful supplement for those currently using only EMG guidance, who would like to supplement their localization with US.