Fig. 4.

Demonstration of the use of ethyl chloride (EtCl), a topical anesthetic, to “freeze out” a site of ulnar nerve compression that has yielded a positive SCT. In order to very specifically anesthetize the desired anatomic site, it is important to shield the areas where you do not want the ethyl chloride to reach. a Application of ethyl chloride to the volar antebrachial fascia proximal to the wrist crease, while shielding Guyon’s canal distally. b Application of ethyl chloride to Osborne’s band between the two heads of the flexor carpi ulnaris, while shielding the retrocondylar groove and the medial intermuscular septum