66 - The Presence of Variant Muscles in the Deep Posterior Leg Compartment Can Result in Tarsal Tunnel Syndrome

Poster Board Number: 66
There are separate poster presentation times for odd and even posters.
Odd poster #s – first hour
Even poster #s – second hour

Co-authors:

Mia Carpenter - Undergraduate Student, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; Zachary Pellis, M.D. - Medical Resident, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; M. Catherine Bandak, M.D. - Medical Resident, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; Chloe Kellum, B.Sc. - Medical Student, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; Ryan Cook, M.D. - Medical Resident, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; Christina Scarr, M.D. - Medical Resident, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; Matthew Zdilla, D.C. - Associate Professor, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; H. Wayne Lambert, Ph.D. - Professor and Vice Chair, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine

Abstract Body : Tarsal tunnel syndrome, or posterior tibial neuralgia, is a neuropathy associated with compressive entrapment of the tibial nerve as it travels deep to the flexor retinaculum, or within the tarsal tunnel. A patient with tarsal tunnel syndrome may present with a variety clinical signs and symptoms, including, but not limited to, painful burning, tingling, and/or numbness. This pain or paresthesia is exacerbated with activity or when a physician applies pressure to, or taps upon, the compressed tibial nerve, which is called a positive Tinel sign. Surgical incision of the flexor retinaculum of the foot usually relieves these signs/symptoms because it creates additional space for the impinged tibial nerve in this compressive entrapment neuropathy. However, two variant leg muscles, the flexor digitorum accessorius longus (FDAL) and fibulocalcaneus (peroneocalcaneus) internus muscles, may be present within the tarsal tunnel, serving as space-occupying lesions. It is important for surgeons and radiologists to confirm or deny the presence of these two muscle variants or subsequent surgical incision of the flexor retinaculum may not provide relief for the patient. The FDAL muscle is present in 2-12% in imaging, surgical, and whole-body donor studies while the fibulocalcaneus internus is present in approximately 1% of legs. This study will show examples of these two variant muscles that reside within the tarsal tunnel, demonstrate the variability of the proximal insertion, course, and distal insertion of these muscular variants, and detail how a patient with these accessory muscles may be predisposed to symptoms of tarsal tunnel syndrome. This anatomical knowledge is crucial to surgeons that need to resect these variant muscles to relieve the signs and symptoms of tarsal tunnel syndrome in patients that possess FDAL or fibulocalcaneus internus muscles.