Image Based Question-65120

Injury/palsy of the nerve (marked with arrow) causes:

A. Dorsiflexion of foot at ankle joint.

B. Planter flexion of the foot at ankle joint.

C. Loss of sensation of dorsum of foot.

D. Paralysis of muscles of anterior compartment of leg.

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Correct Answer » A Explanation

Nerve is Tibial nerve it causes Dorsiflexion of foot at ankle joint

Clinical Relevance: Damage to the Tibial Nerve

Damage to the tibial nerve is rare, and is often a result of direct trauma, entrapment through narrow space or compression for long period of time. Damage results in loss of plantar flexion, loss of flexion of toes and weakened inversion (The tibialis anterior can still invert the foot).

Nerve roots: L4-S3

Sensory: Innervates the skin of the posterolateral side of the leg, lateral side of the foot, and the sole of the foot.

Motor: Innervates the posterior compartment of the leg.

Anatomical Course

The tibial nerve is a branch of the sciatic nerve, and arises at the apex of the popliteal fossa.

Motor Functions

The tibial nerve innervates all the muscles in the posterior compartment of the leg. They are divided into a deep and superficial compartment:

Deep

• Popliteus – Laterally rotates the femur on the tibia to unlock the knee.
• Flexor Hallucis Longus – Flexes the big toe and plantar flexes the ankle.
• Flexor digitorum Longus – Flexes the other digits and plantar flexes the ankle.
• Tibialis Posterior – Inverts the foot and plantar flexes the ankle.

Superficial

• Plantaris – Plantar flexes the ankle.
• Soleus – Plantar flexes the ankle.
• Gastrocnemius – Plantar flexes the ankle and flexes the knee.

Sensory Functions

The tibial nerve also supplies all the sole of the foot via three branches:

• Medial calcaneal branches: These arise within the tarsal tunnel, and innervate the skin over the heel.

• Medial Plantar Nerve: Innervates the plantar surface of the medial three and a half digits, and the associated sole area.

• Lateral Plantar Nerve: Innervates the plantar surface of the lateral one and a half digits, and the associated sole area.

• Tibial nerve (the larger component of sciatic nerve) supplies all muscles of posterior compartment of leg (gastrocnemius, soleus, plantaris, popliteus, tibialis posterior, FHL & FDL) planti flexing the ankle & foot. Therefore, tibial nerve injury results in loss of planter flexion along with calcaneo-valgus attitude of foot (ie dorsiflexion & eversion d/t unopposed anterior compartment muscles).