Definition
· Rare compression neuropathy affecting deep peroneal nerve
· Mostly at the fibroosseous tunnel formed by inferior extensor retinaculum
· Also called “Anterior Tarsal Tunnel Syndrome”
Pathoanatomy
· DPN travels with anterior tibial artery in the interval between EDL and EHL
· Just proximal to the ankle, it bifurcates into lateral and medial branches
o Lateral branch innervates extensor digitorum brevis
o Medial branch supplies sensation from first dorsal web space
· Entrapment under superior and inferior extensor retinacula can cause symptoms
· Compression under inferior extensor retinaculum is known as “Anterior TTS”
· Intrinsic Impingement
o Dorsal osteophytes over tibiotalar and talonavicular joints
o Ganglion cysts
o Tumor
o Peripheral edema
o Enlarged muscle belly of EHL, EDL, EDB
· Extrinsic Impingement
o Tight shoes
o High heels
o Trauma (ankle inversion and plantar flexion)
· Associated conditions: pes cavus, navicular nonunion, talonavicular arthritis
Evaluation
· Burning pain on the dorsum of the foot with first dorsal web space paresthesia
· Usually exacerbated by activities and relieved by rest
· Nocturnal pain is common due to plantar flexion cause the nerve stretch
· High heel shoes also reproduce these symptoms by the same reason
· Weakness/atrophy of EDB, first dorsal web space paresthesia and positive Tinel sign
· Symptoms relieve with the injection of lidocaine (DPN nerve block)
Imaging
· X-Rays show dorsal osteophytes and previous fracture sequalea
· CT can detect bony anatomy of the canal
· MRI is the best way to see masses
· Electrodiagnostic studies are usually normal, but may show a delay in latency or denervation of EDB
Treatment
· Non-surgical
o Reducing the pressure by avoiding tight fitting shoes and high heels
o Diuretics can be used in chronic edema, NSAIDs
o Corticosteroid and local anesthetic injection helps confirming the diagnosis
· Surgical
o Neurolysis is indicated if conservative treatment fails
o Decompression of the nerve is begun just proximal to the superior extensor retinaculum and extends to the base of the first and second TMT joints
o Osteophytes can be resected and hypertrophic muscles can be debulked
Approximately 80% of patients have a satisfactory result