Proper Plantar Digital Nerve to Great Toe: Anatomy, Course, Function, MRI & CT Imaging

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Proper plantar digital nerve to great toe

The proper plantar digital nerve to the great toe is the terminal sensory branch of the medial plantar nerve, itself a division of the tibial nerve. It provides cutaneous innervation to the medial side of the great toe (hallux) and plays a key role in tactile sensation, proprioception, and balance during gait.

This nerve courses along the plantar aspect of the foot, traveling distal to the metatarsophalangeal joint to reach the medial border of the hallux. Because of its superficial position, it is vulnerable to entrapment, trauma, and surgical injury—especially during hallux valgus (bunion) correction, toe deformity surgeries, or repetitive mechanical stress.

Synonyms

Medial proper plantar digital nerve to the hallux
Medial digital branch of the medial plantar nerve
Proper digital nerve to the medial side of the great toe

Origin, Course, and Distribution

Origin: Terminal branch of the medial plantar nerve, which arises from the tibial nerve beneath the flexor retinaculum.
Course:
- Runs forward along the medial side of the foot, beneath the abductor hallucis muscle.
- Passes distally between the abductor hallucis and flexor hallucis brevis tendons.
- Emerges superficial to the flexor hallucis brevis near the first metatarsophalangeal joint.
- Continues along the medial margin of the great toe, dividing into fine digital twigs.
Termination: Ends as multiple fine sensory branches supplying the skin of the medial side of the hallux, including the nail bed and tip.

Relations

Superiorly: Tendon of flexor hallucis longus
Inferiorly: Plantar fascia and subcutaneous tissue of the sole
Medially: Abductor hallucis muscle and medial plantar vessels
Laterally: First common plantar digital nerve (to adjacent sides of the first and second toes)
Anteriorly: Distal phalanx and skin of great toe tip

Function

Sensory innervation: Supplies the medial plantar surface, nail bed, and distal pulp of the great toe.
Proprioception: Provides feedback for fine position sense during gait and toe-off.
Balance assistance: Plays a role in fine tactile adjustments during stance and propulsion phases of walking.

Clinical Significance

Trauma/entrapment: May occur after foot surgery, hallux valgus correction, or repetitive forefoot pressure.
Neuropathy: Compression from footwear, ganglion cysts, or neuromas can cause numbness or tingling along the medial border of the great toe.
Post-surgical pain: Neuroma formation following digital nerve injury can produce localized plantar pain or dysesthesia.
Sensory testing: Loss of sensation on the medial great toe is an early indicator of medial plantar nerve injury.
Imaging relevance: MRI is the best modality for evaluating focal nerve lesions, entrapment, and post-surgical neuromas.

MRI Appearance

T1-weighted images:
- Normal nerve: low-to-intermediate signal intensity, surrounded by bright subcutaneous fat.
- Course visible as a fine, continuous low-signal line extending along the medial aspect of the hallux.
- Neuromas appear as focal fusiform enlargement with slightly higher signal than normal nerve.
T2-weighted images:
- Normal nerve: intermediate-to-low signal, slightly darker than surrounding fat.
- Pathology (neuroma, neuritis, entrapment): hyperintense or heterogeneous signal due to edema or fibrosis.
- Inflammation or trauma may show increased perineural T2 signal and mild adjacent fat stranding.
STIR (Short Tau Inversion Recovery):
- Normal nerve: intermediate-to-low signal
- Neuromas and neuritis: bright hyperintense lesions along nerve course, often oval or fusiform.
- Highlights edema and soft tissue inflammation in the plantar subcutaneous plane.
Proton Density Fat-Saturated (PD FS):
- Normal: slender, dark linear structure in plantar soft tissue.
- Pathology: bright signal corresponding to neuritis, entrapment, or post-surgical change.
- Excellent for detecting subtle perineural edema or focal thickening near the first metatarsal head.
T1 Fat-Sat Post-Contrast:
- Normal nerve: minimal enhancement.
- Neuromas: focal, homogeneous or peripheral enhancement.
- Neuritis: shows diffuse enhancement along the nerve course.
- Scar tissue around prior surgical sites enhances heterogeneously.

CT Appearance

Non-Contrast CT:

Nerve itself poorly visualized due to small caliber and low contrast relative to adjacent tissues.
May show indirect signs such as soft tissue thickening or scarring along the medial plantar surface.
Chronic injury may present with fat stranding, fibrosis, or calcific neuroma.

Post-Contrast CT (standard):

Subtle enhancement of fibrotic or inflamed tissue may be seen.
Useful for evaluating postoperative scarring or soft tissue density lesions near the hallux.

MRI images

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