Updated: 10/12/2016

Deep Peroneal Nerve Entrapment

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Introduction
  •  An compression neuropathy of DPN within fibro-osseous tunnel formed by inferior extensor retinaculum, most commonly at inferior edge
    • also known as anterior Anterior Tarsal Tunnel Syndrome
  • Epidemiology
    • incidence
      • rare
    • demographics
      • adults of all ages and genders
    • risk factors
      • high heel use
      • compressive show wear
      • previous fracture
  • Pathophysiology
    • site of compression
      • anterior leg/ankle/foot from 1 cm proximal to ankle joint proximally to talonavicular joint distally
    • position of compression
      • ankle inversion and plantar flexion (when traumatic)
    • pathoanatomy
      • intrinsic impingement
        • dorsal osteophytes over tibiotalar or talonavicular joints
        • other bony deformity (pes cavus, post-fracture)
        • ganglion cyst
        • tumor
        • tendinitis or hypertrophic muscle belly of EHL, EDL or TA
        • peripheral edema
      • extrinsic impingement
        • tight laces or ski boots
        • high heels (induces plantar flexion)
        • trauma (including recurrent ankle instability)
  • Associated conditions
    • pes cavus
    • fracture
      • navicular nonunion
    • talonavicular arthritis
    • systemic conditions causing peripheral edema
  • Prognosis
    • recalcitrant cases may require surgery, which may yield 80% good to excellent results
Anatomy
  • Anterior Tarsal Tunnel Anatomy  
    • borders
      • superficial
        • inferior extensor retinaculum
      • deep
        • capsule of talonavicular joint
      • lateral
        • lateral malleolus
      • medial
        • medial malleolus
    • contents of anterior tarsal tunnel    
      • EDL
      • EHL
      • Tibialis anterior
      • peroneus tertius
      • Deep peroneal nerve
        • within tunnel division of nerve between mixed (lateral) and sensory only (medial) occurs
      • dorsalis pedis artery and vein
Presentation
  • Symptoms
    • dysesthesia and paresthesias on dorsal foot
      • lateral hallux, medial second toe and first web space are most common locations
    • vague pain on dorsum of foot
  • Physical exam
    • motor
      • weakness or atrophy of EDB
    • sensory
      • decreased two-point discrimination
    • provocative tests
      • Tinel sign over course of DPN with possible radiation to first web space
      • exacerbation with plantar flexion and inversion (puts nerve on stretch)
      • relief of symptoms with injection of lidocaine (DPN nerve block)
Imaging
  • Radiographs
    • recommended views 
      • lateral view of foot and ankle
    • findings
      • dorsal osteophytes
      • sequelae of prior fracture
  • CT
    • to define bony anatomy of canal
  • MRI
    • best for evaluation of mass lesions
Treatment
  • Nonoperative
    • shoe modifications
      • indications
        • first line of treatment
      • techniques
        • NSAIDs
        • PT (if ankle instability contributing)
        • injection
        • well padded tongue on shoe
        • alternative lacing configurations  
        • full length rocker-sole steel shank
        • night splint (to prevent natural tendency for ankle to assume plantar flexion)
        • diuretic if chronic peripheral edema is implicated
  • Operative
    • surgical release of DPN by releasing inferior extensor retinaculum and osteophyte / ganglion resection
      • indications
        • failure of nonoperative treatment
        • symptoms of RSD are a contraindication to release
      • outcomes
        • 80% satisfactory
Technique
  • Surgical release of DPN by releasing inferior extensor retinaculum and osteophyte / ganglion resection
    • approach
      • S-shaped incision over dorsum of foot from ankle joint proximally to base of first and second metatarsals distally
    • decompression
      • start distal, identify nerve, and release both branches proximally (nerve lies lateral to EHL)
      • resect osteophytes, debulk hypertrophic muscle bellies
    • postoperative
      • no compressive shoe wear
Complications
  • Persistent symptoms following decompression
    • warn patient that recovery is prolonged
 

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