Using ultrasound to prevent iatrogenic injury to the dorsomedial cutaneous nerve of the hallux

Abstract

IntroductionThe dorsomedial cutaneous nerve (DMCN) of the hallux is a terminal branch of the superficial fibular (peroneal) nerve which supplies the skin of the medial aspect of the great toe. This cutaneous nerve branch is particularly vulnerable to iatrogenic injury during operative procedures involving the joints of the hallux, including hallux valgus correction, hallux ridigus correction, bunionectomy, and cheilectomy. Moreover, the DMCN of the hallux can be damaged during extensor hallucis longus (EHL) tendon transfer procedures due to the fact this nerve travels superficial to EHL tendon while traveling obliquely in the dorsum of the foot from a proximal lateral location to a distal medial position.MethodsA first‐year medical student, with introductory‐level experience in ultrasonography (USG), performed all USG in the study in an attempt to identify the intersection point of where the DMCN of the hallux crosses the EHL tendon superficially. This study used an ultrasound machine (GE Venue 40 ultrasound machine) in conjunction with an L8‐L18i wide‐band high‐frequency linear array transducer to approximate this intersection. To check the accuracy of the DMCN location, a cruciate incision was made through the skin according to the midpoint markers on the L8‐18i probe.ResultsSuccessful mapping of the DMCN was gauged in binary fashion; if the DMCN was located directly beneath the center of the cruciate incision described, the method was considered successful. Of 28 feet dissected, 21 DMCN nerves (75%) were successfully located.ConclusionsThis study reports that a first‐year medical student with introductory‐level experience successfully identified the intersection of the DMCN with the EHL via USG in 75% of feet examined. Therefore, the success rate would likely improve when USG is performed by surgeons and clinicians with more experience in USG in conjunction with other examination methods, such as the four toe flexion sign. Therefore, USG may provide an inexpensive, accurate, non‐invasive means of pre‐operatively identifying the location of the DMCN of the hallux relative to the EHL tendon to prevent inadvertent nerve damage during foot surgery.Support or Funding InformationThe research of Kyle D. Miller and Jordan V. Swearingen was supported by the West Virginia University Initiation to Research Opportunities (INTRO) Program.