Variant leg muscles involved with tarsal tunnel syndrome: cadaveric case studies (915.11)

Abstract

Tarsal tunnel syndrome, or posterior tibial neuralgia, is diagnosed when the tibial nerve is compressed as it travels within the tarsal tunnel. Two variant leg muscles, flexor digitorum accessorius longus (FDAL) and peroneocalcaneus internus (PCI), have gained recent attention in the clinical literature for their involvement in this compressive entrapment neuropathy. Both of these muscles course within the tarsal tunnel and, when present, may act as space‐occupying lesions, leading to numbness, paresthesia, and pain in the foot. However, low prevalence of these two muscles and discrepancies within the literature have led to confusion distinguishing between these variants muscles. During 317 leg dissections, examples of the FDAL and PCI muscles were identified and ways to differentiate between the two muscles were determined based upon origin, course, location within the tarsal tunnel, and insertion of the muscle. The results of this study also led to the first gross anatomical photograph of the rare peroneocalcaneus internus muscle. Radiologists and clinicians should be aware of these muscles when embarking in diagnosis and imaging interpretation, especially when tarsal tunnel syndrome is within the differential diagnoses.