An abnormal neuromuscular (nerve and muscle) disorder that affects the patient's ability to raise their foot at the ankle. Drop foot is further characterized by an inability to point the toes toward the body (dorsiflexion) or move the foot at the ankle inward or outward. Pain, weakness, and numbness may accompany loss of function.
Walking becomes a challenge due to the patient's inability to control the foot at the ankle. The foot may appear floppy and the patient may drag the foot and toes while walking. Patients with foot drop usually exhibit an exaggerated or high-stepping walk called Steppage Gait or Footdrop Gait.
Etiology:
1- May follow direct injury to the dorsiflexors. A few cases of rupture of the tibialis anterior tendon leading to foot drop and suspicion of peroneal nerve palsy have been reported. This subcutaneous tendon rupture usually occurs after a minor trauma with the foot in plantar flexion.
2- Compartment syndromes also may lead to foot drop. These are surgical emergencies and are not associated only with fracture or acute trauma. March gangrene, a form of anterior compartment syndrome, is thought to be due to edema and small hemorrhages in the muscles of the anterior compartment occurring after strenuous activity in individuals not accustomed to it. Deep posterior compartment syndrome also may result in foot drop as a late sequela due to resultant contracture formation.
3-Neurologic causes of foot drop include mononeuropathies of the deep peroneal, common peroneal, or sciatic nerves. Lumbosacral plexopathy, lumbar radiculopathy, motor neuron disease, or parasagittal cortical or subcortical cerebral lesions also can manifest as foot drop. These lesions can be differentiated through clinical and electrodiagnostic examinations.
Foot drop also may be seen as a combination of neurologic, muscular, and anatomic dysfunction. Charcot foot is one example.
Common and superficial peroneal nerve, branches, and cutaneous innervation.(the left photo)
Deep peroneal nerve, branches, and cutaneous innervation.(the right photo)
Treatments:
Treatment of foot drop is directed to its etiology.
Specific treatment for foot drop may include:
* Medical Therapy:Foot drop is very distressing,If painful paresthesias develop, they can sometimes be effectively managed with sympathetic blocks or laparoscopic synovectomy. Alternative treatments are amitriptyline, nortriptyline, pregabalin, and gabapentin. Local treatment with transdermal capsaicin or diclofenac can also reduce symptoms. Even if there is significant pain, narcotic medications should be kept to a minimum. Optimizing glucose control in diabetic patients and managing vitamin deficiencies with supplements of B-1, B-6, or B-12 can also be useful.
* Braces or splints. A brace on ankle and foot or splint that fits into the shoe can help hold the foot in a normal position.
* Physical therapy. Exercises that strengthen leg muscles and help maintaining the range of motion in knee and ankle may improve gait problems associated with drop foot.
* Nerve stimulation. Sometimes stimulating the nerve that lifts the foot when you step (peroneal nerve) improves foot drop, especially in the case of foot drop caused by a stroke. In some cases, a small, battery-operated electrical stimulator is strapped to the leg just below the knee. In other cases, the stimulator is implanted in the leg.
* Surgery. In cases where foot drop is permanent, surgery that fuses ankle or foot bones or that transfers tendons to stronger leg muscles may be helpful to improve walking difficulties.Foot drop due to direct trauma to the dorsiflexors generally requires surgical repair. When nerve insult is the cause of foot drop, treatment is directed at restoring nerve continuity, either by direct repair or by removal of the insult.Also if drop foot is caused by nerve compression from a lumbar herniated disc, then a spinal surgical procedure called discectomy (disc removal) may be required to relieve or 'decompress' the nerve.