Foot Drop

This seems to be a case of intervertebral disk prolapse at L4 – L5 level involving L5 root. Here since there is muscular weakness, surgical intervention is indicated.

Ref: Schwartz Pretest Surgery, Q. 720

Common peroneal nerve is commonly injured during fracture neck of fibula. Other modes of injury of the common peroneal nerve may be compression caused by a tight plaster on leg and sometimes due to lathi injury on lateral side of the knee. Common peroneal nerve is divided into deep peroneal nerve and superficial peroneal nerve.

Deep peroneal nerve supply muscles of anterior compartment of leg which include tibialis anterior, extensor digitorum longus, peroneus tertius and extensor hallucis longus whereas superficial peroneal nerve supply muscles of lateral compartment of the leg i.e peroneus longus and peroneus brevis.

• In the common peroneal nerve injury the muscles of the anterior and lateral compartment of the leg get paralysed results in weakness of dorsiflexion and eversion of the foot. As there is weakness of the dorsiflexion and eversion of the foot, the opposite muscles, the plantar flexion of the ankle joint and inversion of subtalar and transverse tarsal joint, cause the foot to be plantar flexed. So the planter flexion and inversion are normal.
• The patient has a high stepping gait.
• All the reflexes are intact (ankle jerk is lost in sciatic nerve lesions)
• Sensory loss is present over anterior and lateral side of the leg, dorsum of the foot and toes including medial side of the big toe.
• Sole of the foot derives its sensory innervation from medial calcaneal branch of tibial nerve and branches from medial and lateral plantar nerves so there is no loss of sensations in the foot.

The findings are typical for involvement at the L-5 level. Most ruptured disks involve either the lumbar area L5 and S-1 most common) or the cervical area (C-6 and C-7 most commonly). Compression by a disk of the cervical cord can produce a spastic paresis of the lower limbs; compression of the cauda equina can cause urine retention or incontinence.

The findings are typical for involvement at the L5 level. Most ruptured disks involve either the lumbar area (L5 and S1 most common) or the cervical area (C-6 and C-7 most commonly). Compression by a disk of the cervical cord can produce a spastic paresis of the lower limbs; compression of the cauda equina can cause urine retention or incontinence.

• C-7 supplies the back of the shoulders, down the back of the arm, past the elbow, to the back of the second and third fingers.
• S-3 supplies a small area on the buttocks.
• T-9 supplies a band on the abdomen and back that passes above the umbilicus.
• T-12 supplies a similar band that passes below the umbilicus.

Also Know:

• The dermatomes for C5, C6, C7, C8, and T1 are confined to the arm, and the C4 and T2 dermatomes are contiguous over the anterior trunk.
• The thumb, middle finger, and fifth digit are within the C6, C7, and C8 dermatomes, respectively.
• The nipple is at the level of T4.
• The umbilicus is at the level of T10.

C i.e. Foot drop

–   Common peroneal nerve injury (usually d/t fracture of head/neck fibula)Q results in foot & toe drop, loss of dorsiflexion of ankle, extension of finger and eversion of foot and loss of sensation in 1^st web space, and anterolateral lower leg & dorsum of foot and toes.

– In common peroneal nerve injury sensation of sole, lateral border & medial border & inversion & plantar flexion rmain normal.

B i.e. The appearance of the foot drop indicate early surgical intervention

Ans. D: All of the above

Foot drop may follow direct injury to the dorsiflexors.

A few cases of rupture of the tibialis anterior tendon leading to foot drop and suspicion of peroneal nerve palsy have occurred. This subcutaneous tendon rupture usually occurs after a minor trauma with the foot in plantar flexion.

• Compartment syndromes also may lead to foot drop.

March gangrene, a form of anterior compartment syndrome, is thought to be due to edema and small hemorrhages in the muscles of the anterior compartment occurring after strenuous activity in individuals not accustomed to it. Deep posterior compartment syndrome also may result in foot drop as a late sequela due to resultant contracture formation.

• Neurologic causes of foot drop include mononeuropathies of the deep peroneal, common peroneal, or sciatic nerves. Lumbosacral plexopathy, lumbar radiculopathy, motor neuron disease, or parasagittal cortical or subcortical cerebral lesions also can manifest as foot drop. These lesions can be differentiated through clinical and electrodiagnostic examinations.
• A common behavioral cause of foot drop is habitual crossing of the legs. These cases typically resolve with discontinuation of the habit.
• Foot drop also may be seen as a combination of neurologic, muscular, and anatomic dysfunction. Charcot foot is one example.

B; Common peroneal nerve