Nerve laceration of the leg, ankle and foot

What a nerve laceration is

A nerve laceration is a partial or complete cut through a nerve. In the leg, ankle and foot, most of the nerves near the skin are sensory nerves, which carry feeling. Cutting one leaves a patch of numb skin, and sometimes burning or shooting pain along the nerve’s path. Cutting a nerve that supplies a muscle, such as the peroneal nerve near the knee or the tibial nerve near the ankle, can also cause weakness.

Nerve and tendon lacerations of the foot and ankle are relatively common.^[1] A cut nerve may not be obvious at first, because the wound itself draws the attention. Numbness or a sharp, electric feeling beyond the cut is an important clue.

Causes: common ways a nerve is cut or injured

• Deep cuts and puncture wounds, such as from glass, a kitchen knife, a lawn mower, or a saw.
• Fractures and dislocations, where bone ends stretch or cut a nerve. The common peroneal nerve is the most commonly injured peripheral nerve of the lower limb in trauma.^[3]
• Surgery. A nerve near a planned incision can be cut or stretched. For example, after ankle fracture surgery in one study, 21% of patients treated with surgery had painful symptoms from a superficial peroneal nerve injury, compared with 9% of those treated in a cast.^[4]
• Operations away from the foot. In one series of 28 people with foot drop after an operation, most had earlier lumbar spine, hip or knee surgery.^[5]

Levels of nerve injury

Nerve injuries range from mild to severe:^[2]

• A bruised or stretched nerve often recovers over weeks to months.
• A nerve with internal damage but an intact outer sheath can regrow along its old path, usually over many months.
• A completely cut nerve cannot reconnect on its own and generally needs surgery.

Your history, an examination and sometimes nerve studies or imaging arranged with another specialist help decide which kind of injury is present.^[6]

How it is evaluated

A careful history and examination are the basis for diagnosis and guide treatment. Your clinician will map where feeling is lost or altered, test muscle strength, and tap along the nerve to look for a tender spot.^[6] If a deep wound is fresh, it is often explored so that a cut nerve can be seen directly.^[1] Tell your clinician if numbness began right after the injury or operation, because that timing matters.

Treatment options

• Observation. For a bruised or stretched nerve, watching for recovery over several weeks is reasonable.
• Primary repair. A freshly cut nerve is generally repaired at the time of wound exploration, with the ends sewn together under magnification.^[1]
• Nerve graft or conduit. If the ends cannot be joined without tension, a gap can be bridged. See nerve grafting and nerve repair and reconstruction.
• Nerve transfer. For a cut motor nerve where the muscle needs power back, a working nerve branch can be redirected. See nerve transfer.
• Treating a painful neuroma. If the cut end forms a painful neuroma, the neuroma can be removed and the nerve relocated to a protected place. Most chronic injuries to sensory nerves in the foot and ankle are managed this way.^[1,6] Read more in painful neuroma of the foot, ankle and leg.

Timing and what affects recovery

In a systematic review of traumatic peroneal nerve injuries, better outcomes were linked to a shorter time before surgery, shorter graft length when a graft was needed, a nerve still in continuity, and younger age.^[3] A separate review looked at the timing of nerve surgery separately for sensory injuries, motor injuries, nerve compression and nerve pain.^[7] In general, an early evaluation gives you the most choices. A delayed evaluation can still help, but the plan may change.

What to expect afterward

Nerve fibres regrow slowly, commonly estimated at about a millimetre a day, so recovery is measured in months.^[8] Protect numb skin from heat, pressure and cuts while feeling returns. Tingling that slowly moves down the foot can be a sign of regrowth. Some numbness may be permanent, and sensitivity or pain can persist. Desensitization therapy can help an over-sensitive scar.

When to seek care

Consider an evaluation if you have a cut on the leg, ankle or foot and numbness, burning or weakness beyond the wound, or if a nerve area has stayed numb or painful after an injury or operation.