EP118 A cadaveric study to decode innervation of calcaneal and identify facial planes for injection

<h3>Background and Aims</h3> Ankle blocks are often given for calcaneal fractures. They involve blocking five nerves using multiple injections. The objective of this cadaveric study is to identify the interfacial planes traversed by the nerves innervating the calcaneum. <h3>Methods</h3> Six fresh human cadavers (12 specimens) were used in the study. To investigate the innervation of calcaneum, foot dissection was done in three cadavers (6 specimens) to delineate the nerves of the foot, in specific inter-fascial planes. In other 3 cadavers (6 specimens), ultrasound-guided dye injections were performed in specific inter-fascial planes and diffusion of dye was evaluated. Open dissection was performed in 3/6 specimens and cross-section in 3/6 specimens. <h3>Results</h3> The nerves on the medial side were situated between the proximal attachment of abductor hallucis and quadratus plantae. On the lateral aspect, the skin and subcutaneous tissue over the calcaneum were innervated by the sural nerve and its branches in the subcutaneous tissue immediately lateral to the tendo-Achillis. (Figure 1) After reflecting the abductor hallucis, lateral, medial, and posterior tibial nerves were unstained (4/6). In contrast, the inferior calcaneal nerve and sural nerve were stained in all specimens. (6/6) In the coronal cross-section, the epimysium of the abductor hallucis was well preserved. The epimysium and medial plantar nerve were not stained. <h3>Conclusions</h3> Our cadaveric study suggests the possibility of a two-point injection technique to instil administer a site-specific local anaesthetic to block nerves supplying calcaneum. However, future clinical research based on our cadaveric study should be done to validate our findings further and make it a clinically proper technique.