What Is Peroneal Nerve Injury?
The peroneal nerve controls the muscles in the leg enabling one to lift the ankle and foot upwards (dorsiflexion). It also provides sensation to the top of the feet, the sides, and the front portion of the leg. Whenever there is injury or damage to the peroneal nerve, the individual cannot lift the front part of the foot due to weakness of the corresponding muscle (tibialis anterior). This condition is called a foot drop. It affects the way one walks and also causes pain, weakness, and tingling on the leg and foot.
What Are the Causes of a Peroneal Nerve Injury?
From the lowest part of the spinal cord arises a network of nerves known as the lumbosacral plexus. From this group of nerves, the sciatic nerve branches out. In the back of the thigh above the knee, the sciatic nerve divides into the common peroneal nerve and tibial nerve. The common tibial nerve divides into superficial and deep peroneal nerves. The superficial peroneal nerve innervates the outer side of the leg, helps in twisting the ankle from side to side, and provides sensation in the area. The deep perineal nerves control the activities of the anterior tibialis muscle of the lower leg, which is responsible for flexing the ankle joint upwards and transmitting sensation from that area to the brain.
The peroneal nerve is susceptible to injury at any part on its path to cause a foot drop. It could be at the lower back level or the knee level. The loss of muscular action leading to foot drop is particularly caused by dysfunction of the deep peroneal nerve. The common conditions causing foot drops are:
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Compression of the nerve due to intervertebral disc herniation.
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Pelvic bone fracture leading to lumbosacral plexus injury or tear.
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Hip dislocation, the common peroneal nerve, may cause injury.
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Nerve injury during surgical procedures such as a knee or hip replacement.
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Knee or leg fractures.
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Established compartment syndrome.
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Developing intraneural ganglion.
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Tumors in and around the nerve.
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Due to certain conditions like diabetes mellitus, motor nerve diseases, and inflammation affecting the nerve.
What Are the Symptoms of Peroneal Nerve Injury?
A foot drop is the most striking feature of peroneal nerve injury. It typically features:
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Inability to lift the ankle upwards or arch the foot backward.
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High steppage gait (way of walking) is often characterized by exaggeratedly raising the thigh.
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When an individual with a foot drop walks, the foot slaps down onto the floor, and the toes drag.
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The affected foot tends to show a swinging motion to clear the floor while walking.
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Inability to twist the foot from side to side (foot eversion movement).
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Lack of sensations in the affected foot.
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Pain, weakness, or tingling in the affected leg and foot.
How Is a Peroneal Nerve Injury Diagnosed?
Diagnosis involves a thorough review of medical history. The doctor needs to understand the cause and event that lead to the trauma to determine its impact and severity of nerve damage. This helps in planning the suitable treatment modality. This is followed by a neurological examination to evaluate the functional level of the muscles concerned. The following studies are conducted:
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Foot reflexes are tested by gently tapping along the path of the nerve. If it causes tingling and shooting pain in the foot (Tinel’s sign), it is indicative of nerve irritation or nerve entrapment in a given area.
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X-ray of the knee helps visualize the possibility of fractures and dislocations leading to functional impairment of the nerve.
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A magnetic resonance imaging (MRI) study, computed tomography (CT) scan, or ultrasound scan can identify the presence of lesions that compress the nerve leading to damage.
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Conduct an electromyography (EMG) procedure to measure the strength of nerve signals sent to the muscles and check how they respond to the stimulus.
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Nerve conduction study helps study the speed of electrical conduction from the nerve to the muscle, which is also indicative of the level of activity.
What Is the Treatment for Peroneal Nerve Injury?
If foot drop is not repaired with surgical correction, it results in irreversible muscle and nerve damage. Fasciotomy is the treatment of choice. It is crucial to perform the fasciotomy procedure within four to six hours of injury to prevent nerve death. Recovery from peroneal nerve injury may take up to twelve months. Normally, the big toe is the last part of achieving recovery. Depending on the type, extent, and area of nerve injury, the doctor may suggest nonsurgical or surgical correction as treatment. They include:
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Nonsurgical treatment modalities such as ankle-foot orthotics - Using foot splints inside the shoe and foot braces. Physiotherapy helps improve gait, strength, and level of mobility.
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If there is an open fracture of the hip with an exposed wound, one should explore the nerve and repair it surgically.
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If it is a closed fracture, meaning there are no exposed wounds, but there is injury inside, one may opt to wait for a while for the nerve to recover spontaneously. If recovery is not achieved even after a reasonable amount of time, one should consider exploring the nerve surgically and conduct a repair, nerve graft, and tendon transfer procedure.
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If a knee dislocation has resulted in stretching or injury to the nerve, a nerve transfer or tendon transfer is preferred, where a segment of nerve or tendon is extracted from one part of the body and attached to the site of injury for repair.
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If a disc herniation in the lower back is compressing the nerves to cause foot drop, the herniation should be treated or removed.
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The symptoms can be controlled by pain-relieving medications. The drugs Carbamazepine, Gabapentin, and antidepressants like Amitriptyline also help with the symptoms.
Conclusion:
Doctors recommend people avoid the habit of crossing their legs and putting pressure on the sides or back of the knee for a long time to prevent peroneal nerve injury. The level of recovery is proportional to the severity of nerve damage. If the damage is severe, it may lead to permanent disability. Hence, priority should be given to treating the underlying cause that injures the nerve. If there are any signs of pain or numbness in the foot following trauma, one should not hesitate to get medical help.
