The term "foot drop" refers to a condition in which full active dorsiflexion of the foot is not possible due to paresis or paralysis of the anterior shin muscles. Visible foot drop while walking leads to movement compensations that negatively affect your gait pattern and quality of life. The cause of the foot drop is damage to the peripheral nerve fibers that supply the group of muscles that bend the foot dorsally. The most common trauma to the peroneal nerve or compression of the spinal root occurs in the course of sciatica. Dropping foot can also be a complication of pathologies located in the central nervous system. Treatment depends on the level and degree of damage to the nerve fibers. If there is no hope for the nerve function to return, a surgical procedure involving the transfer of specific muscle tendons is considered.
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Gait disturbance in people with a drop foot
The gait of a person with a drop foot problem is characterized by a high knee lift when moving the leg forward to avoid catching the toes on the ground. The opposite limb is put on tiptoes to functionally increase its length.
At the beginning of the support phase, when the foot is placed with the heel on the floor, the forefoot unconsciously falls down, which may be accompanied by an audible 'slap'. In order to avoid this situation, some patients do not place the foot off the heel, but place the sole of the sole on the floor. The foot is rolled inappropriately over the outer edge of the foot or swaying from the side to the medial edge of the foot.
A dropping foot makes it difficult to walk uphill and up stairs. In addition, it may disqualify you from driving due to the loss of smooth pedal control.
The causes of the foot drop
Anatomy
The sciatic nerve innervating the lower limb is formed from the junction of nerve fibers belonging to the L5-S2 roots departing from the spinal cord in the lumbar spine. The nerve roots pass into the sacral plexus located close to the pelvic surface of the sacrum and then into the sciatic nerve, which leaves the pelvis through the greater sciatic foramen. The sciatic nerve continues to the back of the thigh and, above the knee fossa, splits into a posterior tibial nerve and a common peroneal nerve. The common sagittal nerve passes to the anterolateral part of the lower leg, wrapping around the head of the dart, and then divides into the deep sagittal nerve and the superficial sagittal nerve. The deep sagittal nerve motor innervates the tibial anterior muscle, the long extensor muscle of the fingers and the long extensor muscle of the toe, which are responsible for the dorsal flexion of the foot.
The drop foot may result from damage to the nerve fibers of the above-described peripheral route. It may also result from pathological changes located in the central nervous system - the brain or the spinal cord.
Descending foot - levels of nerve damage:
- Peroneal nerve palsy
Nerve damage most often occurs in the area of the upper part of the arrowhead around which the common peroneal nerve wraps. The causes are usually fractures of the fibula, direct trauma, or torsion of the knee. Deep peroneal nerve dysfunction may be associated with fascial tightness syndrome. In the course of crampedness, increased pressure in the anterior compartment of the shin causes pressure and ischemia of the nerve. If the fasciotomy is not made early, the nerve leading to the foot drop may die. - Damage to the sciatic nerve
The sciatic nerve is often injured as a result of hip dislocation or massive displaced pelvic fractures - Damage to the cross plexus
Pelvic fractures with displacement and dislocation in the sacroiliac joint and neoplastic tumors can damage the fibers of the sacral plexus, resulting in a complication of a drop foot. - L5 spinal root compression in the course of "discopathy" of the spine
Degenerative changes in the lumbar spine lead, among others, to to damage the structure of the intervertebral discs that connect the vertebral bodies to each other. As a result of the so-called In this "discopathy", the nucleus pulposus extends beyond the intervertebral disc ("disc") and may compress the nerve root that extends from the spinal cord. Discopathy on the disc between the fourth and fifth lumbar vertebrae can compress the L5 spinal root. It leads to disturbances of nerve conduction towards the peroneal nerve and secondary weakness or the falling foot often occurs in the course of pathologies such as: injuries of the muscles that straighten the foot dorsally. - Diseases and pathologies of the central nervous system (CNS)
Dropping foot often occurs in the course of pathologies such as:
- ischemic stroke,
- spinal cord diseases,
- multiple sclerosis,
- CNS tumors.
Diagnostics
Diagnostics is carried out by an orthopedist, neurologist or neurosurgeon. First, a thorough interview is made of the circumstances that led to the foot drop. The patient's gait is then observed. If the function of the dorsal extension of the foot is turned off, it is not possible to walk on the heels. The scope and quality of both feet dorsiflexion in the supine position are also assessed. The loss of function is determined on a five-point scale, where 0 is no muscle activity and 5 is the full active range of motion. The doctor also tests the sensation in the lower limb and determines the variability of symptoms depending on the position of the body.
Imaging examinations (ultrasound of the foot, magnetic resonance imaging of the foot) enable the exact location of the nerve compression structure, which facilitates the planning of a possible decompression procedure.
Electrodiagnostic tests - electroneurography (ENG) are used to assess the degree of nerve damage. The nerve is stimulated by a small electrical impulse, which allows the nerve conduction to be examined. The obtained data provide the doctor with information as to the degree of nerve damage, thanks to which it is possible to establish a further prognosis:
Neuropraxia - a disorder of nerve conduction associated with the demyelination process (damage to the sheath surrounding the axon). The state of neuropraxia usually passes quickly and the nerve returns to normal function.
Axonothesis - partial damage to the nerve, it is possible to restore nerve function, provided that the time of muscle denervation does not exceed 1 year,
Neurotmesis - complete disruption of the nerve, its spontaneous regeneration is not possible.
Treatment of the foot drop
The choice of treatment method depends on the level and extent of damage to the nerve tracts. Partial damage to the peroneal nerve offers some hope for nerve regeneration and restoration of the dorsiflexion of the foot required to improve gait pattern. Paresis (weakness in the dorsiflexion) is a promising condition because it indicates the presence of nerve impulses reaching the muscles. Paralysis related to the lack of reaching any stimuli to the muscles is often an irreversible condition that leads to their secondary atrophy.
In any case, the cause of compression of the spinal cord, nerve root, lumbosacral plexus, sciatic nerve or common peroneal nerve should be eliminated as soon as possible.
Further proceedings include, inter alia, rehabilitations. In the case of paresis, exercises for the foot drop are active and assisted. In addition, there are exercises to stretch the calf triceps muscle and exercises to improve deep feeling and stability of the ankle joint. During the period of return to function, the physiotherapist uses techniques of priming individual phases of gait. In the case of paralysis of the muscles of the anterior shin group (no muscle activity), passive exercises are performed to maintain the mobility of the ankle joint until possible surgery.
To avoid negative compensation while walking, the patient should wear a special orthosis that keeps the ankle in a neutral position and prevents the foot from falling. A foot drop orthosis most often has the form of a shell covering the lower leg and the sole of the foot. The orthosis is inserted into the shoe together with the foot. The orthosis can be made of plastic or carbon fiber. The second type of orthosis is a foot drop pull-up, which consists of a band placed over the ankle joint and a hook attached to the shoe. A strap that connects both elements prevents the foot from dropping off while walking.
Functional electrostimulation (FES) is the method most often used in people after stroke and in diseases of the central nervous system. A special device stimulates the peroneal nerve when the heel contacts the ground, protecting the foot against uncontrolled descent. The mechanism of operation of the apparatus is based on the activation of the sensor placed under the heel when loaded with body weight.
Surgical correction of the drop foot - tendon transfers
If there is no chance of nerve function recovery and the patient does not want to be dependent on an orthosis, a procedure involving the transfer of the tendons of the lower leg muscles may be considered. The condition for the success of the procedure is a short time from nerve damage, which determines the maintenance of the passive range of dorsiflexion of the foot. The procedure makes sense only in the case of an isolated damage to the peroneal nerve and when the correct function of the posterior tibial plantar-flexing muscle is maintained. Due to the fact that the role of the posterior tibialis muscle is also to stabilize the longitudinal arch of the foot, the procedure can be performed only in selected patients after a detailed qualification. The operation consists in changing the course of the posterior tibial tendon so that, instead of plantar flexion of the foot, its activity results in dorsiflexion of the foot.
After the surgery, the ankle joint is immobilized with a plaster cast for a period of 6 weeks. After this time, the patient can start putting weight on the limb while wearing a special removable Walker orthosis. Physiotherapy is also carried out, the main goal of which is to re-educate the function of the posterior tibia muscle and learn the correct gait. The patient should strictly follow the instructions of the orthopedist and physiotherapist. Up to 3 months after the procedure, excessive plantar flexion of the foot should be avoided in order not to stretch the displaced tendon. It should be taken into account that the procedure improves the function of the foot only to a limited extent. Using another muscle for the tendon transfer may also lead to disturbances in the stabilization of the longitudinal arch of the foot and the associated complications in the form of flat feet.
When the result of the procedure is uncertain or there is a permanent contracture in the ankle joint, sometimes arthrodesis (stiffening) of the ankle joint is performed in a position that allows free walking without dropping the foot.
Frequently asked questions about peroneal nerve damage and foot drop problem:
The length of treatment depends on the location and degree of damage to the peroneal nerve. Electrodiagnostic tests - electroneurography (ENG) are used to assess the degree of nerve damage. The nerve regenerates 1-1.5 mm a day. The precise determination of the time of the foot dorsiflexion recovery is very individual. Sometimes the foot function returns only partially and it is necessary to continue using the foot drop brace. In some cases, the foot never regains active dorsiflexion movement again.
Surgery may be considered when there is evidence of nerve damage that prevents the dorsiflexus of the foot from resuming activity. The time that has elapsed since the loss of the ability to perform active movement is of great importance - it is important that the ankle joint retains the required passive range of dorsiflexion until the operation.
