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Lateral branch of deep fibular nerve

The lateral branch of the deep fibular (peroneal) nerve is one of the terminal divisions of the deep fibular nerve in the foot. It primarily supplies the extensor digitorum brevis and extensor hallucis brevis muscles and contributes to the anterior ankle joint and tarsal sinus innervation.

This branch plays an essential role in toe extension, proprioception, and ankle stabilization. Due to its superficial location near the dorsum of the foot and proximity to the sinus tarsi and extensor tendons, it is vulnerable to trauma, surgical injury, or entrapment, particularly in anterior ankle procedures.

Synonyms

  • Lateral terminal branch of deep peroneal nerve

  • External branch of deep fibular nerve

  • Muscular branch to extensor digitorum brevis

Origin, Course, and Termination

  • Origin: Arises as the lateral terminal division of the deep fibular nerve beneath the inferior extensor retinaculum on the dorsum of the foot.

  • Course:

    • Passes laterally across the dorsum of the foot, deep to the extensor digitorum brevis (EDB).

    • Gives muscular branches to the EDB and articular twigs to the lateral tarsal joints.

    • Terminates by forming fine filaments communicating with the intermediate dorsal cutaneous nerve and branches of the sural nerve.

  • Termination: Ends near the base of the fifth metatarsal, after supplying motor and articular fibers.

Relations

  • Superiorly: Inferior extensor retinaculum and dorsal foot fascia

  • Inferiorly: Dorsal surface of extensor digitorum brevis muscle

  • Medially: Medial branch of the deep fibular nerve and dorsalis pedis artery

  • Laterally: Sinus tarsi, extensor digitorum longus tendons, and lateral tarsal vessels

  • Anteriorly: Overlying skin and superficial fascia of dorsum of foot

Function

  • Motor: Innervates extensor digitorum brevis and extensor hallucis brevis, controlling toe extension

  • Articular: Supplies branches to the lateral tarsal joints and sinus tarsi

  • Proprioceptive: Provides sensory input contributing to fine control of dorsiflexion and toe movement

Clinical Significance

  • Entrapment neuropathy: Compression beneath the inferior extensor retinaculum or within the sinus tarsi causes dorsal foot pain or weakness in toe extension

  • Trauma: Common during dorsal foot surgeries, lateral ankle sprains, or EDB exposure

  • Iatrogenic injury: May occur in anterior ankle arthroscopy or lateral foot incisions

  • Neuropathy: Causes sensory disturbances and motor weakness of the EDB and EHB

  • Diagnostic value: EMG and MRI useful for identifying nerve entrapment or denervation of EDB

  • Clinical sign: Isolated atrophy of extensor digitorum brevis indicates lateral branch dysfunction

MRI Appearance

  • T1-weighted images:

    • Normal nerve: low-to-intermediate signal coursing beneath the extensor retinaculum

    • Adjacent muscles (EDB, EHB): intermediate signal; normal fat planes appear bright

    • Denervation or injury: EDB shows intermediate-to-high T1 signal from fatty infiltration in chronic cases

  • T2-weighted images:

    • Normal nerve: intermediate signal, appearing slightly darker than on T1

    • Acute neuropathy: nerve may show hyperintense signal due to edema or inflammation

    • Denervated muscle (EDB): increased T2 signal intensity in acute/subacute phase

    • Chronic denervation: muscle replaced by fat, appearing intermediate or hypointense

  • STIR:

    • Normal nerve: low-to-intermediate signal

    • Pathology: bright hyperintense signal in the nerve or adjacent muscle belly indicating edema or neuritis

  • Proton Density Fat-Saturated (PD FS):

    • Normal nerve: low-to-intermediate signal 

    • Entrapment: focal bright hyperintensity and nerve thickening

    • Denervated muscles: bright signal changes in EDB and EHB

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal enhancement

    • Neuropathy or neuritis: patchy or diffuse enhancement of the nerve

    • Postoperative scarring: irregular peripheral enhancement surrounding the nerve

CT Appearance

Non-Contrast CT:

  • Nerve not distinctly visualized due to small caliber

  • Can infer location based on course beneath extensor retinaculum and overlying EDB

  • Chronic changes may show atrophy of EDB muscle or soft-tissue scarring in sinus tarsi region

Post-Contrast CT (standard):

  • Nerve not directly enhanced

  • Perineural fat stranding or enhancing inflammatory tissue may suggest neuritis

  • Useful in evaluating post-traumatic scarring or entrapment around the lateral ankle

MRI images

Lateral branch of deep fibular nerve coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Lateral branch of deep fibular nerve coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001