Peroneal Neuropathy

Definition

Neuropathy is a general term denoting functional disturbances and pathological changes in the peripheral nervous system (the nerves). The peroneal nerve originates in the sciatic nerve and innervates (supplies nervous energy and stimulation) to the calf and foot.

Description

The common peroneal nerve is a branch of the sciatic nerve, one of the largest nerves in the lower half of the body. It lies between the tendon of the biceps femoris muscle and the lateral head of the gastrocnemius muscle in the calf. It passes around the neck of the fibula (the smaller of the lower leg bones). It then passes anteriorly (toward the front) through a foramen (opening) near the attachment of the long peroneal muscle group, where it divides into two branches, the superficial peroneal and the deep peroneal nerve.

The common peroneal nerve is more frequently subjected to trauma than any other nerve in the body. It may be damaged by wounds in the region of the knee or in the trunk of the sciatic nerve in the thigh.

Hip Trauma

The peroneal nerve is frequently injured in high impact trauma to the lower extremity. The most common causes are fracture dislocations of the hip and complications in hip replacement procedures. The two most important prognostic variables are the level and type of injury.

Fracture dislocation of the hip, or simple dislocations, frequently traumatize the peroneal component of the sciatic nerve due to the lateral position of the peroneal nerve fibers. Hip dislocation is a true orthopedic emergency, and immediate reduction (repositioning of bone) is indicated.

Frequently, the palsy (weakness) will resolve spontaneously. However, with posterior wall or posterior column acetabular (the ball of the hip joint) fractures, the nerve may become entrapped in fracture fragments, necessitating careful exploration at the time of surgery.

Complete transection (cutting through) of the peroneal nerve at high levels may cause additional loss of part or all of the biceps femoris function of the hamstrings. The prognosis for functional return of the foot is generally poor with those injuries that require surgical repair or nerve grafting.

Foot Drop

Paralysis (weakness) of the common peroneal nerve results in foot drop and inversion (turning inward) of the foot. The patient cannot dorsiflex (lift up) the ankle, straighten or extend the toes, or evert (turn the foot outward). Walking is characterized by overflexion of the knee and slapping of the foot on the floor (called a steppage gait.) Sensory loss may be present as well.

Treatment

The patient should be informed of the injury to the nerve and a plan should be outlined for treatment and follow-up. The acute management depends on the type of injury, but a dorsiflexion cast or splint may be necessary to hold the foot in a neutral position during the recovery phase.

A very functional type of orthosis (brace) is the inexpensive polypropylene ankle-foot orthosis with removable Velcro straps.

When assessing recovery after an injury, muscle activity can be noted for the first time at the distal aspect of the fibula (the lower part of the smaller leg bone). The peroneal muscles that evert (turn outward) the foot are the first to return, followed by the anterior tibial muscle group.

Questions to Ask Your Doctor

Are there any tests that need to be done to diagnose the condition?

How are these tests performed?

What is the cause of the condition?

Can the condition resolve spontaneously?

What treatment will you recommend?

Will you be prescribing medication? What are the side effects?

How effective is the treatment?