Peroneal Nerve Injury and Foot Drop
Definition and Diagnosis
The peroneal nerve is a branch of the sciatic nerve that wraps around the fibular head ("funny bone") near the knee and then innervates muscles that lift the foot and toes. Damage to this nerve from injury (e.g., knee dislocation), or even surgery, may cause a foot drop. Patients have foot extension weakness, as well as numbness or pain on their shin and top of the foot. Diagnosis is made with a history and examination, and confirmed with electrical testing. For patients with severe trauma, or for those with spontaneous, non-traumatic foot drops, it is important to exclude other causes, including sciatic nerve injury, lumbosacral root trauma (SI joint dislocations and fractures), and even a herniated disc compressing the L5 nerve root. A combination of neurological assessment and electrical testing excludes these other causes. High-resolution 3-T MRI may be useful in evaluating certain lesions.
This patient had a
propeller injury to his
common peroneal nerve
that was repaired
with sural nerve grafts.
Unfortunately, for uncertain reasons, the peroneal nerve has a poor chance of recovery, with or without surgery. The mainstay of early treatment is physical therapy and a properly fitting, custom-made orthotic (foot splint). This orthotic is unobtrusive, and usually allows a return to normal daily activity.
Depending on the type of injury, surgery may be recommended immediately, or after waiting a few months. Surgical repair includes possible decompression, nerve suture, or nerve grafting. Other surgical options include nerve transfer and tendon transfer (see technology and techniques available section). A nerve transfer involves taking a branch from a less important lower leg muscle and connecting it to the muscle that lifts the foot. A tendon transfer involves taking a tendon that moves the foot inward, and connecting it to the top of the foot so that it now lifts the foot upward, thereby resolving the drop foot.
Because peroneal nerve injuries recover very poorly if too much time elapses before treatment, these patients should consider all their options before opting for a more conservative "wait and see" approach.