Introduction

The peroneal nerve is a branch of the sciatic nerve that runs down your leg and curves around the outside of your knee. It controls your muscles that lift your foot and toes and that hels with turning the foot outwards.¹  The peroneal nerve also provides touch sensation to the outer lower leg and the top of the foot.¹ Because of it runs near the surface of your leg, just under the skin, it is easily injured by trauma, fractures, or long periods of sustained pressure. Severe injuries can lead to foot drop, difficulty walking, and numbness, affecting a patient’s mobility and quality of life.²  While some mild injuries may improve with rest, physiotherapy and orthotics, more severe injuries, especially when the nerve is fully torn through, often require surgical intervention to restore function.³ Early surgical management is crucial, as delays increase the risks of permanent muscle loss and poor functional recovery.³ This article explores the use of nerve grafts and transfers as key surgical techniques for managing severe peroneal nerve injuries, with a focus on restoring motor function, and improving long-term outcomes.³

Peroneal nerve: anatomy and injury mechanism

The peroneal nerve is one of the two main branches of your sciatic nerve, andruns down the back of the thigh before wrapping around the outer part of your knee, where it lies close to the skin.¹ Its proximity to the skin surface makes it quite easily injured during trauma. After passing the knee, it splits into two branches: the deep peroneal nerve and the superficial peroneal nerve.¹

The deep branch controls the muscles that lift the foot and toes (this movement is called dorsiflexion), while the superficial branch helps turn the foot outward (this movement is called eversion). It also provides sensation to the outer lower leg and the top of the foot.¹

Injuries can happen from direct trauma, leg fractures, tight casts, or long periods of sustained pressure. Surgery around the knee or hip may also cause damage tothe peroneal nerve. These injuries can interrupt the nerve’s ability to function normally and send signals to the muscles that it supplies, causing weakness, numbness, and foot drop.²

Clinical features and diagnosis

Peroneal nerve injury often causes foot drop, which is when a patient can’t lift the front of their foot while walking. This leads to a high-stepping gait to avoid dragging the toes on the ground.⁴ Other signs include weakness when turning the foot outward and numbness over the outer lower leg and the top of the foot.⁴

On examination, there may be reduced muscle strength, especially in dorsiflexion and eversion, along with decreased sensation in the nerve’s sensory areas.² Reflexes are usually not affected.⁴

Nerve conduction studies (NCS) and electromyography (EMG) are used to assess nerve and muscle activity to confirm the diagnosis. MRI or ultrasound can help identify structural causes like compression or scarring.⁵

Severity is often graded using the Seddon or Sunderland classification, which ranges from mild (temporary signal blockage) to severe (complete nerve interruption). Understanding the extent of the damage is key in deciding between conservative or surgical treatment.⁵

When to operate

Surgery is considered after conservative treatments like physiotherapy, bracing, and observation fail to improve function, usually after several months. The optimal time for surgery is within six months of injury, as delayed treatment can lead to permanent muscle damage.⁶

Surgical repair is more likely to be needed in severe cases, such as when the nerve is completely torn (neurotmesis) or when there’s a large gap between the nerve ends that hinders them from reconnecting.⁷ Injuries higher up the nerve or near the sciatic origin also have a lower chance of natural recovery and may require early intervention.

Nerve grafting techniques

Nerve grafting is used when a section of the peroneal nerve is missing or too damaged for the ends to be stitched back together.⁸ A nerve graft acts as a bridge to help nerve signals travel around the injury or disruption and reach the target muscles.⁸ 

There are two main types of grafts: Autografts (when the patient's own nerves are used as a graft) remain the gold standard, while allografts (using a donor’s nerves) offer an alternative.⁸

•  Autografts, where a nerve is taken from the patient’s own body, usually the sural nerve, which runs along the back of the leg and doesn’t cause major functional loss when removed.⁸ This is the most common method and has the best results because there is no risk of the body rejecting the graft. However, it involves two surgical sites instead of one, which can cause added pain, scarring, or numbness⁹
•  Allografts are donor nerves processed from human tissue banks. These avoid donor site complications and reduce surgery time, but they are expensive and carry a small risk of immune reaction or reduced success in larger gaps⁹

The procedure is done under a microscope to carefully align the nerve ends and graft with fine stitches.¹⁰ The nerve fibres must grow across the graft to reconnect with the muscles, which usually happens at a rate of about 1 mm per day.¹⁰ Several factors affect the outcome of nerve grafting. Shorter grafts tend to have better results than longer ones. Younger patients tend to recover faster. The timing of surgery also plays a key role; delaying repair for too long can reduce the chance of full recovery because the muscles may undergo irreversible atrophy (permanent shrinkage from lack of use), and the motor endplates, which are needed for nerve-muscle connection, may stop working properly.¹⁰ When performed in appropriate cases and within the ideal timeframe, nerve grafting can significantly improve motor and sensory function, particularly if the target muscles remain responsive and structurally intact.¹⁰

Nerve transfer techniques

Nerve transfers are performed when the damaged section of the peroneal nerve is not suitable for direct repair, often due to a high-level or long-standing injury.⁸ This technique involves connecting a nearby functioning nerve to a damaged branch of the peroneal nerve. The new connection allows nerve signals to reach the affected muscles, restoring movement in areas the original nerve can no longer supply.¹¹

The goal is to reinnervate muscles (reconnect them with a functioning nerve supply) downstream from the injury - the muscles that lift the foot and toes - before they lose their ability to recover. This is especially useful in cases of proximal nerve injuries (that are high up the leg) or long-standing nerve damage, where direct grafting would have a poor outcome.¹²

Common nerve transfer techniques include:

• Tibial to deep peroneal nerve transfer: a branch of the tibial nerve is connected to the deep peroneal nerve to help restore dorsiflexion¹¹
• Superficial peroneal to deep peroneal nerve transfer: is used when there is some preserved peroneal function but loss of the key motor branches¹¹

The surgery is done using microsurgical tools to carefully stitch the donor and recipient nerves together.¹³ Over time, the nerve fibres grow into the new pathway and begin to reinnervate the target muscles.¹²

Functional outcomes vary, but studies show that patients often regain active dorsiflexion and improved gait, especially when surgery is done early. Success depends on factors such as the patient’s age, timing of the procedure, and prior muscular condition.¹²

Choosing between graft and transfer

Choosing between a nerve graft and transfer depends on several clinical factors. One key consideration is the time since the injury. If too much time has passed, the chances of graft success drop and a transfer may be more effective. Beyond 12 months, nerve transfers (e.g., tibial-to-peroneal) are preferred due to their shorter regeneration distance and faster functional recovery.¹⁰ The location and extent of nerve damage also matter in long gaps or high-level injuries, which are less likely to recover with grafting alone.¹⁰ 

Another important factor is the availability of suitable donor nerves, both for grafts and transfers. Muscle viability, often assessed with EMG, helps determine whether the muscles are still capable of responding to reinnervation.¹⁰

In some cases, a combined approach may be used, for example, using a graft to bridge part of the nerve and a transfer to improve key functions like dorsiflexion.¹⁴ Hybrid approaches (e.g., grafting to bridge a defect + transfer for critical motor functions) are increasingly used, particularly in multilevel injuries. Studies report 50–70% functional recovery.¹⁴ The surgical plan is tailored to each patient based on the type of injury, recovery window, and functional goals.

Post-surgical recovery and rehabilitation

Rehabilitation is essential for supporting and enhancing functional recovery following nerve repair surgery. Physical therapy helps strengthen reinnervated muscles, maintain joint mobility, and prevent stiffness.¹⁵ Orthotic devices, such as ankle-foot orthoses (AFOs), are often used to support foot positioning and improve walking while the nerve heals.¹⁶

Neuromuscular re-education is also important; it retrains the brain and muscles to work together as new nerve signals begin to reach their target muscles.¹⁷ Recovery takes time, as nerve fibres grow slowly, around 1 mm per day, depending on the length of the regeneration path.¹⁰ Full functional recovery may take 12–18 months for distal injuries (low down on the leg) and longer for proximal repairs (higher up on the leg).¹⁷

Patient involvement is critical. Adherence to therapy, consistent use of orthotics, and regular follow-ups all contribute to better outcomes.¹⁷ Psychological support may also be needed, as prolonged recovery can affect motivation and quality of life. A tailored, multidisciplinary approach helps ensure the best possible return of strength, function, and independence after surgery.¹⁷

Summary

Severe peroneal nerve injuries can lead to significant loss of movement and sensation, often resulting in foot drop and impaired mobility.¹ When direct repair isn't possible, surgical options like nerve grafts and transfers aim to restore function.⁸  Nerve grafts are used to bridge gaps, while nerve transfers bring in a healthy nerve to take over the lost function.⁸ The choice depends on injury location, timing, and muscle viability. Recovery relies heavily on early intervention, rehabilitation, and patient commitment. With early surgery, proper rehabilitation, and patient commitment, many people can regain movement and improve their quality of life.¹⁰