Addressing the causes and treatment options of drop foot.

As the director of spine rehabilitation and the director of education for Delaware-based PRO Physical Therapy, my clinical load consists primarily of spine and lower-extremity neuro-orthopedics patients, particularly foot and ankle. Currently, most of my patients with drop foot have the condition related to peripheral nerve injuries at the spine (nerve root) level, as well as peripheral nerve injury.

Basic Footnotes
The condition of drop foot involves the partial or complete loss of function of the ankle dorsiflexor muscles, which include the tibialis anterior, the extensor digitorum longus, and the extensor hallucis longus. These are the muscles that concentrically pull the foot up, allowing the foot to clear the ground during gait and eccentrically control the descent of the foot from heel strike to midstance during the stance phase of gait.

Predominately, active ankle and toe dorsiflexion are deficient in drop foot situations. Certainly, patients with drop foot often have symptomatology or deficits in other regions or systems of the body. For example, a patient with multiple sclerosis can have a plethora of neurological sequelae of which drop foot is only one small component. A patient with a disk herniation may have leg and/or back pain in addition to the drop foot.

Causes for drop foot involve interruption of the nerve impulse traveling toward the muscles as a result of insult to some part of this conduction system at the brain, spinal cord, or peripheral nerve levels. Causes at the brain level could be a cerebral vascular accident, a traumatic brain injury, or a brain tumor. Causes at the spinal cord level could include a spinal cord injury or a spinal tumor, for example. A lesion at the nerve root is common with lumbar disk herniations with compression on the L4 and/or L5 nerve roots. Compressive peripheral nerve injuries can occur with fibular head fracture, resulting in injury to the common and/or deep peroneal nerves. Peroneal nerve injury can also occur intraoperatively or with compartment syndrome. Finally, diabetic or idiopathic neuropathy can result in drop foot.

Treatment Options
The majority of products to treat drop foot involve bracing options. The most common brace used is an ankle foot orthosis (AFO). AFOs include double upright braces with or without dorsiflexion assist, as well as off-the-shelf and custom-molded AFOs such as the molded ankle foot orthosis (MAFO). Another product on the market is related to functional electrical stimulation (FES). The product is a heel switch that activates a motor-stimulation unit with electrodes on the common peroneal nerve as the patient strikes his or her heel in the gait cycle. The stimulation has a duration long enough only for the patient to clear his or her toes during swing limb advancement.

Perhaps the most important role for the PT treating a patient with drop foot is to advise the medical and rehab teams regarding the appropriateness of and timing for bracing. Safety is the biggest concern, and bracing should be advised immediately if the patient is at a fall risk. Less black and white are situations where the patient has partial paralysis and safety is not at risk. In these cases, the patient may be getting neurological return and it is possible to compromise rather than facilitate this return if you rush to put the patient in a passive device. The other concern is maintaining adequate and optimal muscle length and joint and skin integrity while the patient is compromised from motor and sensory standpoints.

The major sign that indicates a severe drop foot is a gait pattern called “steppage gait,” in which the patient excessively flexes his hip and knee during the swing phase to clear the foot and toes from the ground. More subtle clues may be uncovered with a functional neurological screen, during which the patient has difficulty or is unable to walk on his heels on one side. Finally, sensory and motor testing may pick up more subtle deficits.

Other treatments include passive stretching of the musculotendinous structures, which are not going through functional lengthening due to the motor deficit; patient education regarding the prognosis and the time frame for neurological return; patient education regarding sensory deficits and maintenance of skin integrity in situations with sensory compromise, especially when bracing is used with sensory compromise; and sensory-motor facilitory training to optimize return, as well as compensation.

Finally, in rare instances, there can be surgical treatment for drop foot. The technique I am aware of involves rerouting the posterior tibialis tendon to make it insert anterior to the ankle-joint axis and substitute function for the anterior tibialis.

The most interesting drop foot cases are the ones in which a practitioner has told a patient that he or she will never get full return, and then the patient gets nearly full or full return. That’s why the best advice as a practitioner is to never say “never”—just educate the patient that the longer the duration of time that passes without signs of return, the less the likelihood of return. I’ve seen plenty of outrageous recoveries, including a patient with unchanging motor deficits for more than 10 years who got neurological return in both her upper and lower extremities during her first pregnancy.

I would anticipate the greatest advancements of the future would involve medical or electrical intervention that would facilitate axonal repair. Also, certainly surgical technique is always evolving, and postoperative rehab considerations are quick to follow.

Craig Weaver, MS, PT, OCS, Cert MDT, is the director of spine rehabilitation and the director of education for Delaware-based PRO Physical Therapy.