No abstract

The fibulocalcaneus (peroneocalcaneus) internus (PCI) muscle is a rare variant leg muscle with a low prevalence of <1%‐3% in cadaveric dissection and imaging studies. The PCI arises from the medial aspect of the distal third of the fibula, descends posterior and lateral to the flexor hallucis longus (FHL) muscle, traverses the tarsal tunnel inferior to the sustentaculum tali of the calcaneus, and inserts into the plantar surface of the calcaneus. However, controversy exists concerning the exact location of the insertion site of the PCI muscle. The insertion of the PCI muscle was recently described as being located distal to the coronoid fossa, a small depression between the anterior tuberosity and the anterior apex of the sustentaculum tali of the calcaneus. However, historical descriptions described the PCI as inserting into either the sustentaculum tali itself or a small tubercle on the medical surface of the calcaneus distal to the sustentaculum tali. During routine dissection of a 53‐year‐old Caucasian male, a PCI muscle was identified, and it inserted into distal to the coronoid fossa on the plantar surface of the calcaneus. More specifically, it inserted into the plantar surface of the calcaneus in the space between the origin of the plantar talonavicular (spring) ligament and the plantar calcaneocuboid ligament. Knowledge of the PCI muscle is important due its involvement with various ankle pathologies, including predisposing individuals to tarsal tunnel syndrome, FHL tenosynovitis, and posterior ankle impingement and pain.

The dorsomedial cutaneous nerve of the hallux (DMCN) is a sensory nerve that crosses the extensor hallucis longus (EHL) tendon to innervate the great toe and the first metatarsophalangeal joint. The DMCN is vulnerable to injury during operative procedures including hallux valgus or hallux rigidus correction, bunionectomy, and cheilectomy, as well as EHL tendon transfer surgeries. Intraoperative injury to the DMCN may cause pain that is intractable without subsequent surgical intervention. Accordingly, understanding anatomical variation of the DMCN is of the utmost importance. Therefore, this study assessed 23 cadaveric legs and feet to identify morphological variations of the DMCN. Observed variations included supernumerary branches crossing the EHL tendon and atypical superficial fibular nerve branching that affected the anatomical relationship between the DMCN and the EHL tendon. This study provides details of atypical variations of the DMCN and the resulting data, when used in conjunction with current imaging techniques (ultrasonography), may help to prevent unwarranted iatrogenic nerve injury.

The dorsomedial cutaneous nerve of the hallux (DMCN) provides sensation to the skin of the dorsomedial hallux (big toe) and the first metatarsophalangeal joint. This cutaneous nerve, a terminal branch of the superficial fibular (peroneal) nerve, is located in the dorsum of the foot and crosses the extensor hallucis longus (EHL) tendon during its course. At this intersection point, the DMCN is at risk for injury during operations of the hallux and metatarsophalangeal joint including EHL tendon transfer, hallux valgus or hallux rigidus corrections, bunionectomy, cheilectomy, or injection procedures. Iatrogenic injuries often result in sensory loss, debilitating causalgia, or neuroma formation. The aim of this study was to identify anatomical variations at the intersection of the DMCN and the EHL tendon. Twenty‐three feet (12 left‐sided, 11 right‐sided) from 12 cadavers were dissected to follow the course of the DMCN and look at its intersection with the EHL tendon. Dissection resulted in damage to three DMCNs; however, 20 feet (11 left‐sided and 9 right‐sided feet) dissections resulted in excellent visualization of both the DMCN and the EHL tendon. Supernumerary branches of the DMCN were identified crossing the EHL tendon in multiple locations in fourteen of twenty feet (70.0%), including nine left feet (9/11, 81.8%) and five right feet (5:9, 55.6%). Of the fourteen feet with supernumerary branches, seven feet (50.0%) had two branches, four feet (28.6%) had three branches, and three feet (21.4%) had four‐to‐six branches of the DMCN crossing over the EHL tendon in multiple locations. The results of this study identify the complex branching patterns of the DMCN. Surgeons should be aware of that supernumerary branches of the DMCN exist, crossing the EHL tendon in multiple locations, and use ultrasonography to lower the risk of iatrogenic injury to the DMCN during surgical procedures.