Foot drop

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Defined as a significant weakness of ankle and toe dorsiflexion.

A gait abnormality in which the dropping of the forefoot happens due to, damage to the peroneal nerve or paralysis of the muscles in the anterior portion of the lower leg.

Not a disease entity, but a symptom of a existing problem.

Characterized by the inability or difficulty in moving the ankle and toes upward.

Can be a temporary or a permanent condition.

Severity depends on the extent of muscle weakness or paralysis.

Can occur unilaterally or bilaterally.

Can be caused by nerve damage alone, by muscle or spinal nerve trauma, abnormal anatomy, toxins or disease.

Diseases that can cause foot drop include stroke, Amyotrophic lateral sclerosis, muscular dystrophy, Charcot Marie Tooth disease, multiple sclerosis, Cerebral palsy, Friedreich’s ataxia, and hip replacement surgery.

The foot and ankle dorsiflexors include the tibialis anterior, extensor hallucis longus, and extensor digitorum longus.

Dorsiflex muscles help the body clear the foot during swing phase and control plantar flexion of the foot on heel strike, and weakness of these muscles result in exaggerated flexion of the hip and knee to prevent toes from catching the ground during the swing phase of gait.

Causes the foot to slap on the ground.

Foot drop results with injury to the dorsiflexors or to any point along the neural pathways that supply them.

Associated with a variety of conditions such as dorsiflexor injuries, peripheral nerve injuries, stroke, neuropathies, drug toxicities, or diabetes.

Characterized by steppage gait, with dragging of toes along the ground or the bending of the knees to lift the foot higher than usual to avoid the dragging.

This process to raise the foot high enough to prevent the toe from dragging and prevents the slapping of the foot, and the patient may use a characteristic tiptoe walk on the opposite leg, raising the thigh excessively, as if walking upstairs, while letting the toe drop.

Wide outward leg swing, or to turn corners in the opposite direction of the affected limb may be associated with foot drop.

Diagnosis often is made on physical examination.

Patients with foot drop will have difficulty walking on their heels.

Testing the patients ability to dorsiflex may determine diagnosis of the problem, and can be measured on a 0-5 scale that observes mobility.

Additional tests include an MRI, or EMG to assess the areas of damaged nerves.

The peroneal nerve innervates the muscles that lift the foot, which are the anterior muscles of the leg that are used during dorsi flexion.

The muscles that are used in plantar flexion are innervated by the tibial nerve.

Paraesthesia in the lower leg, particularly on the top of the foot and ankle, can accompany foot drop.

The causes of foot drop, as for all causes of neurological lesions, should be approached using a localization-focused approach before etiologies are considered.

Most of the time it is the result of neurological disorder.

Only rarely it is related to muscle or bone disease of the lower leg.

The source for the neurological impairment can be central involving spinal cord or brain or peripheral nerves connecting from the spinal cord to an end-site muscle or sensory receptor.

The anterior tibialis muscle picks up the foot and is innervated by the deep fibular peroneal nerve, a branch from the sciatic nerve which exits the lumbar plexus with its root arising from the fifth lumbar nerve space.

Associated with neurodegenerative disorders of the brain that cause muscular problems, such as multiple sclerosis, stroke, and cerebral palsy, motor neuron disorders such as polio, some forms of spinal muscular atrophy and amyotrophic lateral sclerosis, injury to the nerve roots, such as in spinal stenosis and peripheral nerve disorders such as Charcot-Marie-Tooth disease or acquired peripheral neuropathy with damage to the peroneal nerve as it passes across the fibular bone below the knee, and muscle disorders, such as muscular dystrophy or myositis.

Causes of foot drop may be divided into 3 general categories: neurologic, muscular, and anatomic, and these processes may overlap.

Peroneal neuropathy caused by compression at the fibular head is the most common compressive neuropathy in the lower extremity, and foot drop is its most significant finding.

Peroneal neuropathy more common in males:females 2.8:1 .

All age groups are affected equally in peroneal neuropathy and 90% of cases are unilateral.

Peroneal nerve palsy can be seen after total knee arthroplasty or proximal tibial osteotomy.

Occurs in about 0.3-4% of cases after total knee arthroplasty and 3-13% after proximal tibial osteotomy.

intraoperative injury to the peroneal nerve by trauma, traction, laceration, constrictive dressings, hematoma and ischemia may occur and result in foot drop.

Relative risk of peroneal palsy is 2.8 times greater for patients who receive epidural anesthesia for total knee arthroplasty than for those who received general or spinal anesthesia.

Prior lumbar laminectomy with total knee arthroplasty associated with a relative risk of peroneal palsy of 6.5 times greater than those without previous lumbar surgery.

Patients with pre-existing spinal stenosis are at increased risk for the development of foot drop after hip arthroplasty.

Can be caused by compartment syndromes,

May be secondary to mononeuropathies of the deep peroneal, common peroneal, or sciatic nerves.

Lumbar radiculopathy, motor neuron disease, or parasagittal cortical or subcortical cerebral lesions also can be associated with foot drop.

May be caused by crossing of the legs.

Isolated foot drop is usually a flaccid process.

Possible lesion sites causing foot drop include:
Neuromuscular disease
Peroneal nerve disease
Sciatic nerve abnormality
L5 nerve root abnormality
Spinal cord abnormality
Brain lesion
Genetic abnormality
Cauda Equina Syndrome

Management depends on the underlying disorder.

Ankles can be stabilized by orthoses, to prevent foot drop.

Shoes can be fitted with traditional spring-loaded braces to prevent foot drop.

Functional electrical stimulation (FES). sometimes ref2242ed to as Neuromuscular electrical stimulation (NMES) can stimulate the peroneal nerve, which lifts the foot.

Foot-up ankle support may be sufficient help.

Treatment depends on the specific cause of foot drop.

Support with braces and shoe inserts are indicated.

Physical therapy to increase muscle strength and maintain joint motion may be helpful.

Electronic peroneal stimulation may be helpful.

In the presence of permanent loss of movement, surgery that fuses the foot and ankle joint or that transfers tendons from stronger leg muscles may be indicated.

Prognosis depends on the cause, as cases related to trauma or nerve damage can have partial or even complete recovery.

In the presence of progressive neurological disorders, foot drop will likely be a permanent process.

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