Sonographic assessment of the tarsal tunnel compared to cadaveric findings: a pictorial study.

Aim of the study: To present the anatomy of the tarsal tunnel and demonstrate the utility of high-resolution ultrasound for tarsal tunnel examination. Materials and methods: Anatomical dissection was performed on a defrosted cadaveric model to demonstrate relevant anatomical structures of the tarsal tunnel, namely tendons, vessels and nerves. The tibial nerve division was demonstrated; the bifurcation of the tibial nerve into the medial and lateral plantar nerve, two medial calcaneal nerve branches were identified originating from the tibial nerve and the Baxter's nerve was identified as the first branch of the lateral plantar nerve. An ultrasound examination of the tarsal tunnel region was performed on a healthy volunteer. A linear probe was used and sonographic images were obtained at different levels of the tarsal tunnel: the proximal tarsal tunnel, the tibial nerve division into the medial and lateral plantar nerves, the distal tarsal tunnel, the Baxter's nerve branching point and the Baxter's nerve crossing between the abductor hallucis and quadratus plantae muscle. Results: Sonographic images were correlated with anatomical structures exposed during cadaveric dissection. Conclusions: We presented the anatomic-sonographic correlation of the tarsal tunnel and showed that high-resolution ultrasound is a useful imaging modality for tarsal tunnel assessment.