Does the Tibial Nerve Anatomy of Rodents Compare to Human?
Elisabeth Maria Brakkee, MD, MSc, UMC Utrecht, Utrecht, Netherlands, Erick DeVinney, BS, Clinical and Translational Sciences, AxoGen Inc, Alachua, FL and J. Henk Coert, MD, PhD, University Medical Center Utrecht, Utrecht, Netherlands
Introduction
In neuropathic pain models such as the Spared Nerve Injury (SNI), Tibial Neuroma Transposition (TNT) and Distal Nerve Injury (DNI) model, denervation of the tibial nerve results in hypersensitivity of the lateral plantar surface of the hind paw, innervated by the uninjured neighboring sural nerve. When comparing surgical methods, the nomenclature of the nerves cut proximal to the ankle differs. In the DNI model, these nerves are named the medial plantar nerve (MPN) and lateral plantar nerve (LPN), while they are known as the posterior tibial nerve and calcaneal nerve in the TNT model. Clear anatomical references are essential to correctly implement and compare neuropathic pain models. Our aim was to document and compare the nerve anatomy of the medial aspect of the ankle for mice, rats and humans. This study could provide helpful information for researchers when analyzing and interpreting results using models for neuropathic pain.
Materials & Methods
Surplus mice (n=8 paws) and rats (n=8 paws) of other experiments without any surgical history of the hind paws were examined under terminal anesthesia. The course of the distal part of the tibial nerve and its plantar branches was photographed and schematically depicted. The distance between the bifurcation of the tibial nerve (BTN), the calcaneal nerve and the heel are measured in millimeter.
Results
In both mice and rats, the BTN into the MPN and LPN is situated 4,8mm (mice) and 21mm (rats) above the heel (proximal to the tarsal tunnel) and the calcaneal nerve sprouts from the LPN. In mice, the sural nerve joins the LPN. In rats, a communicating branch is found between the LPN and MPN, at the level of the tarsal tunnel. A schematic overview of the course of the tibial nerve compared to human anatomy is shown in figure 1.
Conclusions
In both mice and rats, the BTN is situated proximal to the tarsal tunnel. Therefore, we can conclude from this study that the TNT model actually transposes the MPN, which suggests that hypersensitivity on the lateral part of the plantar surface of the hind paw in rats can be induced by cutting only the MPN. In the SNI model in mice, the intact sural nerve joins a denervated LPN, which might have consequences for the interpretation of results.
Back to 2021 ePosters