Purpose-Submental anatomical variation is of clinical importance with regard to head and neck surgeries. One such anatomical variation is that of additional musculature joining the intermediate tendon of the digastric muscle to the midline of the mylohyoid musculature-a variation which this report refers to, accordingly, as an arrowhead variation. Though the arrowhead variation has been described in several case reports, it has not been subject to cross-sectional study. The purpose of this study is to determine the prevalence of the arrowhead variation. Methods-Prevalence of the arrowhead variation was assessed in 19 cadavers via gross dissection. Results-Two of the 19 cadavers (10.5%) were found to have arrowhead variations. The arrowhead variation was found in one male (1:11; 9.1%) and one female (1:8; 12.5%), respectively. Conclusions-This report demonstrates that the submental arrowhead variation of the anterior digastric and mylohyoid musculature has been reported in isolated case reports since the nineteenth century. This report is the first cross-sectional study of the arrowhead variant, identifying it in approximately one in ten individuals and in both sexes. Therefore, the presence of an arrowhead variation should be regularly considered with regard to diagnosis of submental masses. Likewise, the arrowhead variation should be considered in the preoperative planning of the myriad operations performed in the submental region.

Terminal branches of the superficial fibular nerve are at risk of iatrogenic damage during foot surgery, including hallux valgus rigidus correction, bunionectomy, cheilectomy, and extensor hallucis longus tendon transfer. One terminal branch, the dorsomedial cutaneous nerve of the hallux, is particularly at risk of injury at its intersection with the extensor hallucis longus tendon. Iatrogenic injuries of the dorsomedial cutaneous nerve of the hallux can result in sensory loss, neuroma formation, and/or debilitating causalgia. Therefore, preoperative identification of the nerve is of great clinical importance. The present study used ultrasonography to identify the intersection between the dorsomedial cutaneous nerve of the hallux and the extensor hallucis longus tendon in cadavers. On ultrasound identification of the intersection, dissection was performed to assess the accuracy of the ultrasound screening. The method successfully pinpointed the nerve in 21 of 28 feet (75%). The sensitivity, positive likelihood ratio, and positive and negative predictive values of ultrasound identification of the junction of the dorsomedial cutaneous nerve and the extensor hallucis longus tendon were 75%, 75%, 100%, and 0%, respectively. We have described an ultrasound protocol that allows for the preoperative identification of the dorsomedial cutaneous nerve of the hallux as it crosses the extensor hallucis longus tendon. The technique could potentially be used to prevent the debilitating iatrogenic injuries known to occur in association with many common foot surgeries.

The anterior belly of the digastric muscle (ABDM) is important in numerous esthetic surgeries including rhytidectomy, alteration of the cervicomental angle via partial resection of the ABDM muscle belly, and suprahyoid muscular medialization and suspension. Recently, the connection between the ABDM and the mylohyoid muscle (MH) has been proposed as important for the mechanism of the digastric corset procedure. This report refers to the connection between the ABDM and the MH as a type of retaining ligament of the anterior digastric muscle (RLAD). This report is the first to directly demonstrate the existence of the RLAD, via photograph and video, and document variation in its attachment sites, its composition, and its behavior when traction forces are applied. In addition to the importance of the RLAD in plastic surgery, the RLAD may affect neurovascular structures between the ABDM and MH and serve as a physical barrier separating the submental fascial space from the submandibular fascial space and, therefore, influence the spread of infection.

The flexor digitorum accessorius longus (FDAL) muscle is a variant muscle located in the posterior compartment of the distal leg. It typically originates in the distal third of the leg and can have a variable proximal attachment to the tibia, fibula, tibia and fibula, the posterior intermuscular septum, or any of the musculature in the deep posterior compartment of the leg. The FDAL then courses posterior to the medial malleolus, enters the the tarsal tunnel (deep to the flexor retinaculum), and ends by inserting onto either the flexor digitorum longus tendon and/or the quadratus plantae muscle, which are located in the second muscular layer of the sole of the foot. The prevalence of the FDAL has been reported in 6% of asymptomatic individuals based on MRI studies or 2–12% of cadaveric studies.The presence of the FDAL has been identified as a cause of tarsal tunnel syndrome, a compression neuropathy of the tibial nerve and/or its branches that become compressed as they course deep to the flexor retinaculum. As the FDAL traverses the tarsal tunnel, it lies immediately superficial to the neurovascular bundle and can act as a space‐occupying lesion, entrapping the tibial nerve and causing numbness, pain, and paresthesias in the foot, ankle, and toes. This variant muscle is best visualized through the use of magnetic resonance imaging (MRI). While there are conservative treatments for tarsal tunnel syndrome, most often surgical intervention is needed to remove the FDAL, and the success of this operative procedure is often based on the extent of damage to the tibial nerve prior to surgery. This presentation will include a patient case and show examples of the FDAL muscle following cadaveric dissection and within MRI studies. Radiologists and surgeons should be aware of presence of the FDAL muscle when considering the etiology of tarsal tunnel syndrome.Support or Funding InformationThe research of Jordan V. Swearingen and Kyle D. Miller was supported by the West Virginia University Initiation to Research Opportunities (INTRO) Program.