OVERVIEW

What is the common peroneal nerve in common peroneal nerve injury?

The common peroneal nerve, also known as the fibular nerve, is one of the two major branches of the sciatic nerve. It is composed of fibers from the anterior branches of the L4-L5 and S1-S2 spinal nerves. After branching from the sciatic nerve above the popliteal fossa, it runs downward and laterally along the medial border of the biceps femoris muscle, wraps around the fibular neck, pierces the proximal end of the peroneus longus muscle, and reaches the anterior aspect of the fibular neck, where it divides into the superficial and deep peroneal nerves.

Its muscular branches innervate the lateral and anterior muscle groups of the lower leg and the dorsal foot muscles, while its cutaneous branches supply the skin of the lateral lower leg, dorsum of the foot, and dorsal toes.

What is common peroneal nerve injury?

Common peroneal nerve injury refers to a category of disorders characterized by temporary or permanent dysfunction of the common peroneal nerve due to various physical or chemical factors, with the lesion site located within the anatomical range of the common peroneal nerve.

It is often caused by external compression on the common peroneal nerve, with the most common injury site occurring where the nerve wraps around the lateral aspect of the fibula.

SYMPTOMS

What are the manifestations of common peroneal nerve injury?

• Severe common peroneal nerve injury may present with complete paralysis symptoms: such as inability to dorsiflex the foot, inability to extend the toes, foot inversion and drooping, forming a "talipes equinovarus" deformity, and exhibiting a "steppage gait" when walking; accompanied by sensory disturbances in the anterolateral leg and dorsum of the foot.

• Mild injuries may only show sensory disturbances in the anterolateral leg and dorsum of the foot. A few patients may experience transient pain or tenderness in the leg when flexing or extending the knee, without motor deficits such as weakness in toe dorsiflexion, and a positive Tinel's sign at the fibular level of the common peroneal nerve.

• A study showed that among 103 patients with common peroneal nerve injury, 79% exhibited sensory loss, while only 17% experienced pain.

CAUSES

What are the causes of common peroneal nerve injury?

• Since the common peroneal nerve is most superficial near the knee, where it wraps around the lateral side of the fibula, compression in this area is the most common cause of injury.

• Additionally, sharp trauma to the lateral lower leg, fibular head fractures, compartment syndrome of the lower leg, prolonged squatting, crossing the legs, knee replacement surgery, improper surgical positioning, and leg cast immobilization can also lead to common peroneal nerve injury.

• In rare cases, common peroneal nerve injury may occur in the popliteal fossa, where the sciatic nerve has already divided into the tibial and common peroneal nerves. Popliteal cysts are the most frequent cause of injury in this region.

• Lastly, neurofibromas within the common peroneal nerve can also manifest symptoms of nerve injury.

Who is more prone to common peroneal nerve injury?

• Common peroneal nerve injury often occurs in individuals who work in prolonged squatting positions or are bedridden for extended periods, particularly diabetic patients. Due to microvascular complications, diabetics experience peripheral nerve malnutrition, making their nerves more susceptible to injury and recovery more difficult.

• Trauma causing impact to the lateral knee near the fibular neck can also result in common peroneal nerve injury.

• Furthermore, patients undergoing knee replacement surgery, those requiring lithotomy positioning during surgery, individuals with intraoperative tourniquet use, and those with lower limb cast immobilization have a higher risk of iatrogenic common peroneal nerve injury.

DIAGNOSIS

What tests are needed before diagnosing common peroneal nerve injury?

Generally, if symptoms such as numbness in the lateral calf area, foot drop, or limping while walking persist for an extended period without improvement, or if these symptoms occur after knee replacement surgery, lithotomy position surgery, or in patients with lower limb cast immobilization, common peroneal nerve injury should be considered.

After a thorough physical examination by a doctor, the diagnosis can be confirmed. Additional tests may include electromyography (EMG), nerve ultrasound, and magnetic resonance imaging (MRI) of the affected limb.

Why are these tests necessary for common peroneal nerve injury? What precautions should be taken?

• Electromyography (EMG): For patients with closed common peroneal nerve injury, EMG can pinpoint the exact location of nerve damage and provide insight into the severity of the injury. It also helps differentiate whether symptoms are caused by sacral plexus or sciatic nerve injury.

• Nerve ultrasound: High-frequency ultrasound can clearly visualize the course, internal structure, and surrounding tissues of most peripheral nerves, revealing the extent and specific cause of nerve injury. This provides imaging evidence for clinical treatment. While nerve ultrasound is relatively convenient, it requires a highly skilled ultrasonographer. It is suitable for patients with mobility difficulties or those with metal implants.

• MRI: MRI can display the entire course of the common peroneal nerve, clarify its relationship with surrounding tissues, and assess the extent of nerve damage. It can also detect the presence of nerve sheath tumors. However, patients must remove all metal objects before the scan, and those with metal implants cannot undergo MRI.

What conditions can common peroneal nerve injury be confused with? How to differentiate them?

Common peroneal nerve injury can be easily confused with lumbar nerve root injury caused by herniated discs, sciatic nerve injury, lumbosacral plexopathy, diabetic amyotrophy, and idiopathic lumbosacral radiculoplexus neuropathy:

• Lumbar nerve root injury due to herniated discs often presents with lower limb pain, which may radiate from the buttocks down the back of the thigh, accompanied by numbness.

• Symptoms of sciatic nerve injury are not limited to the area innervated by the common peroneal nerve and may also include signs of posterior tibial nerve injury.

• Lumbosacral plexopathy symptoms are not confined to the common peroneal nerve distribution. If the lumbar plexus is involved, it may manifest as weakness in hip flexion, adduction, or knee extension, though weakness can sometimes be patchy.

• Diabetic amyotrophy and idiopathic lumbosacral radiculoplexus neuropathy often present with asymmetric, focal-onset pain, followed by weakness in the legs, with symptoms progressing over months.

TREATMENT

How to provide first aid for suspected common peroneal nerve injury?

In cases of traumatic common peroneal nerve injury, first apply pressure above the injured area to reduce blood loss and seek immediate medical attention.

Which department should I visit for common peroneal nerve injury?

Common peroneal nerve injury falls under the scope of orthopedic diagnosis and treatment.

When is physical therapy needed for common peroneal nerve injury?

Physical therapy is often the first choice for common peroneal nerve injury. An ankle-foot orthotic splint can be used to maintain dorsiflexion until active movement recovers. Under the guidance of a physical therapist, gradual rehabilitation should progress from passive to assisted passive, active, and active resistance exercises.

While undergoing physical therapy and functional exercises, dehydration therapy and neurotrophic drugs can be used to reduce nerve edema and aid nerve repair.

When is surgery required for common peroneal nerve injury?

Surgery is necessary for patients who cannot recover naturally, when symptoms and signs are progressing without other identifiable causes, or when there is confirmed common peroneal nerve entrapment, external mass compression, or a confirmed schwannoma in the common peroneal nerve region.

If the nerve is severed due to trauma, surgery is required to restore the anatomical structure of the common peroneal nerve, providing a foundation for later recovery.

What treatments are needed after surgery for common peroneal nerve injury?

Nerve injury repair is a lengthy process. Surgery only provides certain conditions and a foundation for nerve recovery, so post-operative treatments such as neurotrophic therapy and reducing nerve edema are still necessary.

Can common peroneal nerve injury fully recover?

Nerve cells are stable cells in the human body with poor regenerative capacity. The recovery of nerve function depends on the specific circumstances of the injury.

• If the injury is caused by entrapment by surrounding tissues, the recovery time of nerve function is closely related to the duration of compression. Shorter compression periods increase the likelihood of recovery, while prolonged compression leading to irreversible nerve damage makes recovery extremely difficult.

• If the common peroneal nerve is severed due to trauma, the recovery of nerve function depends on the distance of the nerve defect. Studies show that peripheral nerve regeneration is extremely slow, often taking years. If no recovery occurs within two years, the injury is considered irreversible, and functional reconstruction therapy may be required.

DIET & LIFESTYLE

What should be noted in diet after discharge for common peroneal nerve injury?

• Patients with common peroneal nerve injury should protect the affected limb after discharge to avoid re-injury. The affected limb should avoid excessive stretching and actions that may increase compression on the common peroneal nerve, such as crossing legs or squatting.

• Due to sensory impairment caused by common peroneal nerve damage, care should be taken to prevent burns or frostbite in areas with sensory loss.

• In daily life, it is necessary to strengthen nutrition, rest properly, maintain a good mental state, and actively cooperate with physiotherapists for functional recovery exercises.

PREVENTION

Can common peroneal nerve injury be prevented? How to prevent it?

The most common cause of common peroneal nerve injury is compression of the nerve. Therefore, in daily life, it is important to avoid situations that may compress the nerve, such as prolonged squatting, sitting cross-legged, or lying on one side.

Preventing lumbar disc herniation also helps avoid peripheral nerve injuries, including those affecting the common peroneal nerve. Additionally, avoiding trauma in daily life is one of the most effective ways to prevent common peroneal nerve injury.