Finding the mechanism behind injury helps shed light on the appropriate interventions and treatment for drop foot.
by Nathan A. Diffenbaugh, MSPT, DPT
Sometimes the seemingly simple activities of daily life can be the most challenging for a patient. They may complain of catching their foot during gait or notice that they trip frequently. Clinically, a therapist may recognize a steppage gait pattern or notice increased circumduction of one lower extremity. Manual muscle testing of the anterior tibialis may reveal a strength deficit. Drop foot is the inability or decreased ability to dorsiflex the toes and foot.1
Drop foot can affect an individual of any age. Children struggle with drop foot due to cerebral palsy, muscular dystrophy, brain injury, or stroke. Individuals who injure their sciatic nerve, the deep peroneal nerve, or the common peroneal nerve may suddenly find clearing the foot becomes a difficult task. Injuries around the L5-S2 nerve root, such as lumbar disc herniation, are a cause of drop foot.2 Other causes of drop foot include ailments such as amyotrophic lateral sclerosis, multiple sclerosis, or Charcot-Marie-Tooth disease.3
To address the patient’s deficit, it is important to determine the exact mechanism of injury for a patient. Although there are numerous causes of foot drop, the first thing that must be identified is the area in which the pathology has occurred. Upper motor neurons (UMNs) or supraspinal nerves are found in the brain stem and spinal cord. Common UMN pathologies include cerebrovascular accident, traumatic brain injury, and multiple sclerosis. Lower motor neurons, also called primary motor neurons, are those that directly innervate muscle fiber.4 Patients may report a “chronic back injury,” experience traumatic injury of the lower extremity, or have suffered a spinal cord injury in the lower lumbar region. Do not forget, disease process impacting muscle fibers also can cause foot drop in instances such as muscular dystrophy or direct trauma.
For individuals with Duchenne’s muscular dystrophy, surgery is used to release Achilles tendon contractures. Unfortunately, research studies show limited long-term benefits. Patients may require future surgical interventions to maintain gains.5
If a person has anterior tibialis weakness due to a lumbar disc herniation, the goal of surgery is to relieve pressure on the nerve root. Successful surgery provides relief from pain and some strength return. While sounding promising, studies often find that the amount of recovery is not always enough to overcome the deficits that developed prior to surgery.2
The lack of a quick fix for foot drop means control of the ankle is often left to the physical therapist. Many patients believe that a few weeks of exercise will cure their problem. Unfortunately, this is not often the case. Many patients find that drop foot affects their level of independence and increases their risk for falling, leading to additional injuries. Another factor is decreased ankle control, which can result in ligamentous injuries or fractures of the foot and ankle. The compensatory gait techniques to clear the affected foot may require increased energy usage, thus limiting the patient’s daily activity. As therapists, we are tasked with helping patients select the most appropriate device to address their drop foot with the least amount of restriction and abnormal energy expenditure.
Functional Electrical Stimulation
During the past few years, partially due to excellent marketing, wireless functional electrical stimulation (FES) devices for drop foot have become a popular means of treating the condition. These devices utilize a relatively comfortable electrical stimulation pattern. This electrical impulse causes nerve excitement to produce muscle activation. By monitoring the gait cycle, the device determines when toe off occurs in order to activate dorsiflexion during the swing phase of gait. These FES devices are relatively simple to operate with a cuff design that serves to maintain proper electrode alignment. This increases patient compliance with proper placement of the electrodes. The manufacturer limits the amount of adjustments a patient can make to the stimulation level in order to limit the possibility of accidental injury. Clinicians usually have additional tools at their disposal to properly adjust and set up the electrical pulse pattern. Through the use of simple software programs on a laptop or tablet, the clinician can effectively customize the settings. By connecting the device to the software, a clinician also can review the patient’s daily usage.6-8
From a clinician’s standpoint, the main advantage this technology provides is a more normalized gait cycle (compared to standard bracing methods), with the patient achieving both dorsiflexion and plantarflexion. Another clinical benefit is the ability to use their muscles during functional movement patterns. The device manufacturer suggests this leads to improved strength and muscle activation based on the principles of neuroplasticity.6
Studies have reported that patients like how the device assists them to achieve a more normal gait cycle. Some patients remark that they feel the FES devices respond better to changes in gait, which increases their levels of mobility and balance. There is also the psychological benefit of not wearing a brace. For the casual observer, a person using this device may not carry the same stigma of being as “disabled” as a person wearing a brace. Patients also claim they are more comfortable overall when walking.9
Despite the therapeutic benefits these devices may offer, the technology does have drawbacks. FES devices typically can only cause nerve excitement among individuals who have sustained an upper motor neuron injury. As with all electronic devices, they can break. Another problem is the device does not provide medial-lateral support, which can make it unsuitable for patients who have poor ankle control. An individual also needs to have good cognition to safely operate the device. Poor hygiene can result in skin irritation, and there is always the small risk a patient may be allergic to the materials used in the device. Finally, these devices utilize electricity so they must remain dry.
Various studies have supported the use of these FES devices. They have found user satisfaction and functional improvements. The studies show that the functional gains are at least comparable to those of standard bracing.10,11 Some studies even suggest the use of FES is superior to standard bracing in regard to increased functional safety and independence. Patients utilizing FES report feeling they have improved gait stability. This may allow for improved ability to overcome physical obstacles during their daily routines.12,13 Another advantage is that these devices do not have a full foot plate, such as what appears on many braces, thus allowing for improved somatosensory input. There are also small scale studies that focused on the use of FES in children with cerebral palsy and indicated promising results.14,15
Use of Bracing
Sometimes the best approach for a patient is use of lower extremity bracing. In today’s world, the standard ankle foot orthosis (AFO) is also undergoing numerous changes. Most clinicians have utilized Molded Ankle Foot Orthotics (MAFOs) for years. A slightly newer twist is the use of carbon-fiber AFOs. While most carbon-fiber AFOs are not custom made (there are custom options), sizing still needs to be completed to ensure proper fit.
Patients may prefer an AFO due to concerns about an FES device malfunctioning. Others find an AFO is simply more suited to their lifestyle.9 There are numerous design options for MAFOs intended to address the patient’s functional deficits. Carbon fiber has the ability to absorb and release stored energy during gait, making it a popular choice.16
Choosing the correct option is not always a simple matter. Consider the following two examples. A woman, who is in her late fifties, with left hemiplegia due to a stroke at birth, is referred to therapy. She has used a custom MAFO with great success for years. She lives with her family and is on permanent disability. Her only complaint is occasional left hip pain. She had seen marketing materials for an FES device and wanted to see if it would work for her. She had only trace ankle dorsiflexion strength and ambulated with a single point cane. Due to the chronic nature of her injury, I was at first a little skeptical.
During therapy, she was able to trial an FES device with great success and soon obtained a home trial device. A month after using the device, she was walking without a cane and no longer complained of left hip pain. Her stride length had become more equalized, and she also felt more confident in her gait. She eventually chose to purchase the device.
The second individual came to the clinic after moving into the area. He was a middle-aged corporate leader who already had purchased an FES device in a different state. He complained that despite regular use of the device, he was catching his toe. A complete medical history was obtained. The patient had multiple lumbar disc herniations with multiple surgical interventions. His surgical report revealed he had chronic lower motor neuron injuries. While the patient had a slight anterior tibialis contraction with the use of the FES, he also could achieve a similar contraction without it. Unfortunately, the device was not the best option for him. It provided some assistance but it was not helping with his functional independence. He eventually selected a carbon-fiber AFO and no longer had complaints of toe drag.
It is important for therapists to remember the value of a thorough evaluation when making the choice between bracing and a FES device. A good working relationship with an orthotist is invaluable when making this choice for the patient. An orthotist who is willing to come into the clinic and take part in a therapy session can greatly impact the design choice. This allows for discussion between the patient, therapist, and orthotist to provide the optimal outcome. It is important to work with someone who holds a similar philosophy in regard to the goals of bracing. Personally, I like to work with orthotists who believe in minimizing the amount of compensatory movement by a patient. Ultimately, the patient is the one wearing the device and it is our job to listen to our patients’ needs when assisting them in their selection. RM
Nathan A. Diffenbaugh, MSPT, DPT, is employed as a staff therapist for Lehigh Valley Health Network in Allentown, Pa. He works in an outpatient setting on the neuro team. Diffenbaugh also runs a monthly bracing clinic to assist patients with selecting the appropriate devices to meet their needs. For more information, contact RehabEditor@nullallied360.com.
The Free Dictionary By Farlex. Foot-Drop. Available at: http://medical-dictionary.thefreedictionary.com/foot-drop
Liu K, Zhu W, Shi J, et al. Foot drop caused by lumbar degenerative disease: Clinical features, prognostic factors of surgical outcome and clinical stage. PLoS One. 2013;8(11):e80375-e80375.
The Mayo Clinic. Diseases and Conditions, Foot Drop. Available at: http://www.mayoclinic.org/diseases-conditions/foot-drop/basics/causes/CON-20032918
Neuroscience 2nd edition Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Sunderland (MA): Sinauer Associates; 2001.
Sackley C, Disler PB, Turner-Stokes L, Wade DT, Brittle N, Hoppitt T. Rehabilitation interventions for foot drop in neuromuscular disease. Cochrane Database Syst Rev. 2009(3):CD003908.
Bioness Inc. L300 for foot drop. Available at: http://www.bioness.com/L300_for_Foot_Drop.php
Walkaide. The Walkaide System. Available at: http://www.walkaide.com/en-US/Pages/default.aspx
OML. ODFS Pace XL Kit. Available at: http://www.odstockmedical.com/products/odfs-pace-xl-kit/
Bulley C, Shiels J, Wilkie K, Salisbury L. User experiences, preferences and choices relating to functional electrical stimulation and ankle foot orthoses for foot-drop after stroke. Physiotherapy. 2011;97(3):226-233.
Everaert DG, Stein RB, Abrams GM, et al. Effect of a foot-drop stimulator and ankle-foot orthosis on walking performance after stroke: A multicenter randomized controlled trial. Neurorehabil Neural Repair. 2013;27(7):579-591
Kluding PM, Dunning K, O’Dell M,W., et al. Foot drop stimulation versus ankle foot orthosis after stroke: 30-week outcomes. Stroke. 2013;44(6):1660-1669.
Hausdorff JM, Ring H. 2008. Effects of a new radio frequency-controlled neuroprosthesis on gait symmetry and rhythmicity in patients with chronic hemiparesis. Am J Phys Med Rehabil. 87(1):4-13.
van Swigchem , Roos, H,J.R., den Boer , Jasper, Geurts A, C., Weerdesteyn V. Effect of peroneal electrical stimulation versus an ankle-foot orthosis on obstacle avoidance ability in people with stroke-related foot drop. Phys Ther. 2012;92(3):398-406.
Prosser LA, Curatalo LA, Alter KE, Damiano DL. Acceptability and potential effectiveness of a foot drop stimulator in children and adolescents with cerebral palsy. Dev Med Child Neurol. 2012;54(11):1044-1049.
Levi. Review of electrical stimulation, botulinum toxin, and their combination for spastic drop foot. J Rehabil Res Dev. 2013;50(3):315-326
Desloovere K, Molenaers G, Van Gestel L, et al. How can push-off be preserved during use of an ankle foot orthosis in children with hemiplegia? A prospective controlled study. Gait Posture. 2006;24(2):142-151.