Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Sciatic Nerve Anatomy

• Sciatic nerve is the largest nerve in the body.
• Originates from L4, L5, S1, S2, and S3 nerve roots.
• Contains two major components: tibial nerve and common peroneal (fibular) nerve.
• Travels through gluteal region and posterior thigh.
• Usually divides into tibial and common peroneal nerves in the distal thigh.
• In about 10% of individuals division occurs at the greater sciatic foramen.

Relationship with Piriformis Muscle

• Sciatic nerve normally exits pelvis inferior to piriformis muscle.
• Some anatomical variations may exist.
• Compression of sciatic nerve at piriformis causes piriformis syndrome.

Piriformis Syndrome

• Sciatic nerve compression by piriformis muscle.
• Causes buttock pain and sciatica-like symptoms.
• Must rule out lumbar disc herniation before diagnosis.
• Diagnosis is clinical and by exclusion.

Clinical Tests for Piriformis Syndrome

• Lasègue maneuver: hip flexion to 90° with knee extended reproduces pain.
• FAIR test: Flexion, Adduction, and Internal Rotation of hip stretches piriformis.
• Pressure over buttock may reproduce tenderness.

Course of Sciatic Nerve in Gluteal Region

• Nerve runs anterior to piriformis muscle.
• Posterior to obturator internus, gemelli, and quadratus femoris.
• Lies between greater trochanter and ischial tuberosity.

Sciatic Nerve Injuries

• Commonly injured in posterior hip dislocation.
• Common peroneal division most frequently affected.
• Can be injured during posterior hip surgery or acetabular screw placement.
• Traction during surgery should be applied with knee flexed to reduce nerve tension.
• Injury may cause foot drop.

Muscles Supplied by Sciatic Nerve

• Long head of biceps femoris.
• Ischial portion of adductor magnus.
• Short head of biceps femoris supplied by common peroneal division.

Common Peroneal Nerve

• Branches from sciatic nerve near the knee.
• Wraps around the neck of the fibula.
• Divides into superficial and deep peroneal nerves.
• Vulnerable to injury in knee dislocation and fibular neck fractures.

Superficial Peroneal Nerve

• Supplies lateral compartment muscles: peroneus longus and peroneus brevis.
• Pierces fascia in distal third of leg to become superficial.
• Provides sensation to dorsum of the foot.

Injury to Superficial Peroneal Nerve

• May occur during lateral compartment fasciotomy.
• Risk during anterolateral extensile approach for pilon fractures.
• May be injured during ankle arthroscopy portal placement.

Deep Peroneal Nerve

• Supplies anterior compartment muscles: tibialis anterior, extensor hallucis longus, extensor digitorum longus.
• Provides motor supply to extensor digitorum brevis.
• Provides sensory innervation to the first web space.

Deep Peroneal Nerve Injury

• Causes foot drop due to loss of ankle dorsiflexion.
• Loss of sensation in the first web space.

Anterior Tarsal Tunnel Syndrome

• Compression of deep peroneal nerve beneath inferior extensor retinaculum.
• Symptoms include dorsal foot pain, paresthesia, and numbness in first web space.
• Symptoms worsen with tight shoes and plantar flexion.

Tibial Nerve

• Runs posterior to medial malleolus beneath flexor retinaculum.
• Divides into medial plantar, lateral plantar, and medial calcaneal branches.

Tarsal Tunnel

• Fibro-osseous tunnel behind medial malleolus.
• Covered by flexor retinaculum.
• Contains structures remembered by mnemonic: ‘Tom, Dick, And Very Nervous Harry’.
• Tibialis posterior tendon.
• Flexor digitorum longus tendon.
• Posterior tibial artery.
• Tibial nerve.
• Flexor hallucis longus tendon.

Tarsal Tunnel Syndrome

• Compression neuropathy of posterior tibial nerve within the tarsal tunnel.
• Causes plantar foot pain, numbness, and paresthesia.

Baxter’s Nerve

• First branch of lateral plantar nerve.
• Provides motor supply to abductor digiti minimi.
• Responsible for up to 20% of heel pain cases.
• Entrapment may mimic plantar fasciitis.

Sites of Baxter’s Nerve Entrapment

• Between fascia of abductor hallucis and quadratus plantae muscle.
• Near medial calcaneal tuberosity.

Calcaneal Traction Pin

• Used for traction or external fixation.
• Inserted from medial to lateral side of calcaneus.
• Pin should be placed posteroinferior to avoid neurovascular bundle.

Morton’s Neuroma

• Compression neuropathy of interdigital nerve.
• Most commonly occurs in third interdigital space.
• Associated with perineural fibrosis.