Could AFOs have an impact for elderly patients? Can AFOs reduce fall risk for frail senior citizens? How do AFOs affect mobility in patients with diabetic neuropathy? With these questions in mind, this author offers a closer look at the evidence on AFO use in elderly populations.
Podiatric physicians are challenged daily in clinical practice with implementing offloading devices that parents will tolerate well and wear consistently until achieving the treatment outcome. Often, the clinician overlooks another critical concern when applying casts or dispensing walking boots, splints and ankle-foot orthotic (AFO) braces: the safety of the patient.
Consider a scenario in which a frail elderly female patient presents to your practice reporting a traumatic fall at home. X-rays reveal a non-displaced fracture of the fibula. The patient is experiencing significant pain with extreme difficulty upon ambulation. You are aware there are studies showing that casts and walking boots can compromise balance. What protective offloading device should you implement for this frail patient who has already demonstrated a fall risk?
Consider another scenario in which you attend a practice management seminar and hear a lecture about performing a “fall risk assessment” in the office to identify patients who are at risk for suffering a traumatic fall. The speaker provides a list of findings that identify patients at risk for falling:
1. Visual problems
3. Gait impairments
4. Muscle weakness
5. Decreased ankle range of motion
6. Previous history of traumatic falling
8. Use of psychotropic medications
9. Seizures, hypertension, diabetes or arthritis
After the clinician has identified a patient at risk for falls, he or she may consider fitting the patient with a pair of custom AFO “balance braces,” according to the lecturer. This intervention has been “clinically proven” according to the speaker, implying that the braces actually have been tested and proven to prevent falls in the elderly.
The first scenario is hypothetical. The second scenario is a reality as it has occurred many times over the past few years at podiatric seminars and has been promoted in advertising in trade publications. In both situations, it behooves the practitioner to look at the scientific literature regarding the effects of AFO braces on frail senior citizens.
Patients who meet the above criteria for “balance bracing” would be considered frail. According to the American Geriatrics Society, “frailty is a state of increased vulnerability to poor resolution of homeostasis following a stress, which increases the risk of adverse outcomes including falls, delirium and disability.”1 Elderly individuals who meet the criteria for frailty are at significant risk for catastrophic decline when they confront any physiologic challenge.2 Therefore, frail elderly patients would be at greater risk for negative response to an intervention that altered their current state of lower extremity function.
What The Research Says About AFOs And Balance
Since there are no published peer-reviewed studies showing that any AFO brace can actually prevent falls in non-neurologic impaired elderly patients, it becomes more relevant to look at other situations in which bracing is an appropriate intervention for treatment. However, concern exists regarding the potential for doing harm to these people who are already compromised and are at risk for catastrophic falls. Frail elderly patients can suffer lower extremity trauma such as a sprain, fracture or tendon rupture. Alternately, these patients may be challenged by hemiplegia, resulting from stroke or neurologic conditions. In these cases, bracing is almost mandatory to restore mobility for these patients and allow recovery.
There is a large volume of studies of AFO bracing and the effects on balance and gait. When examining the scientific literature, it becomes apparent that there are several important distinctions between the types of braces tested, the patient population in the study and the methods of determining balance.
Researchers have shown that solid plastic non-articulating AFO devices have negative effects on balance in many studies of various patient populations.3-9 While some companies promote so-called “balance braces” as being “dynamic AFOs,” scrutiny of the true design of these devices reveals that they are actually “static AFOs.”
An article from Cattaneo and colleagues defines “static” versus “dynamic” AFO devices.10 Under the definition from the authors, the original balance brace design and all copies of this AFO design on the market would be considered “static” AFO devices. They do not meet the criteria for “dynamic” devices, which have ankle joints and allow free plantarflexion. No matter how thin or flexible the plastic shell, static AFOs will limit ankle joint motion more than the non-brace condition. Walking boots, a.k.a. controlled ankle motion (CAM) walkers, are solid ankle-foot orthoses that also contain a rocker sole, which can further exacerbate the gait disturbances that this type of brace can impose on the frail elderly patient.
Static, non-articulating AFO braces have the potential to significantly decrease proprioception and balance in the lower extremity via several mechanisms. Crabtree and Higginson point out that patients must generate significantly greater ankle plantarflexion strength to deform the plastic shell of a non-articulated AFO to achieve normal toe-off during gait.11
In their study of healthy patients wearing a solid plastic shell AFO, Vistamehr and coworkers found that ankle plantarflexor power and forward propulsion were significantly less with the solid AFO due to the device limiting the ankle range of motion.5 In this same study, whole body angular momentum was higher with the AFO during both steady state and non-steady state walking conditions, indicating a loss of dynamic balance. The researchers concluded: “Solid ankle-foot orthoses limit the successful execution of important mobility subtasks in healthy adults and that the prescription of ankle-foot-orthosis should be carefully considered.”5
An overlooked mechanism by which solid, non-articulating AFO devices can inhibit lower extremity proprioception is their effects on sensory receptors located in muscles, tendons and ligaments. These receptors are part of the Golgi tendon organs as well as the muscle spindles. Ankle joint motion provides a critical stimulus to these proprioceptors located in the ankle ligaments as well as the muscles and tendons of the lower leg.12,13 Movements of the ankle joint create tension in the mechanoreceptors located in these structures, which transmit essential information to the central nervous system regarding postural sway.
In terms of hierarchy, proprioceptive input from ligaments, tendons and muscle stretch-reflex is far more important for balance than proprioceptive input from cutaneous receptors.14-16 Thus, it is not surprising to see researchers have demonstrated that restricting ankle joint motion with bracing significantly diminishes proprioception and neuromuscular control over the ankle.17-19
Another negative effect of restrictive non-articulated static bracing of the ankle is the effect on muscular stabilization for balance control. Authors have described an “ankle strategy” in which upright balance is maintained by muscular stabilization of the body over the foot at the ankle joint.17,18 In this mechanism, the patient will move the ankle and subtalar joint to correct alignment of the body, and keep the center of mass properly positioned over the supportive foot. By restricting ankle joint movement with solid bracing, Bennell and colleagues point out that patients will have to adapt with more proximal muscle activation using the “hip strategy,” which is less efficient at maintaining upright balance.16
What About AFOs In Patients With Diabetic Neuropathy?
Many frail, elderly patients have signs and symptoms of peripheral neuropathy. Some have diabetes and some do not. Studies of immobilizing devices worn by patients with diabetic neuropathy show alarming negative effects. Walking boots significantly reduce postural control in patients with diabetic neuropathy, who already have a 20 times greater risk for falling than age-matched controls.15,19
In evaluating patients with neuropathy, Hijmans and coworkers conducted a systematic review and concluded “Ankle immobilization has a negative effect on balance performance immediately after application because another motor control mechanism (hip strategy instead of ankle strategy) is needed for control of balance.”20
Finally, when looking at immobilizing devices used to treat plantar ulceration in patients with diabetes, Van Deursen concluded that casts and braces that limit ankle joint motion can exacerbate postural instability and risk of falling in patients with diabetes.21
A Closer Look At A Recent Balance Brace Study
Recent claims have been made in podiatric trade publications that a certain “balance brace” has been “clinically proven to reduce postural sway and improve postural stability.”22 I evaluated this published study in a previous DPM Blog.23 What this study actually showed was:
1. The balance brace reduced postural sway in quiet bipedal standing.
2.The balance brace failed to improved dynamic balance in two other tests.
3.The study evaluated the effects of the balance brace on healthy seniors, not frail seniors, who are the target of marketing campaigns to receive bilateral static balance braces.
4. This was not a clinical trial.
5. Over 23 studies have been published showing improvements of postural control in people wearing many different types of ankle braces and foot orthoses. This single study was certainly not the first or only such investigation that showed improvements in static balance with an ankle brace.
Research has never shown that improving postural control during quiet standing reduces fall risk in elderly patients. In fact, many researchers have focused on studies of dynamic balance to predict fall risk. Several have pointed out the shortcomings of simply evaluating postural control in quiet bipedal stance.24,25
The Timed Up and Go and the Limits of Stability are both tests of dynamic balance, and are considered far more predictive of fall risk than quiet standing tests.26,27 The balance brace failed to show balance improvements in both of these tests.
A study of patients with neuropathy wearing bilateral static restrictive AFO devices revealed similar findings as the sponsored balance brace study.9 It appears that solid AFO devices may improve static postural control in some impaired patients but will not improve dynamic balance during gait.3
Conversely, the authors of the balance brace study point out that dynamic tasks were not affected adversely by the braces.22 While it would have been desirable to see dynamic balance improved with these braces, the study does not show anticipated negative effects of static AFOs on dynamic balance. However, it is critical to point out that the patients in this study were healthy older adults. They did not suffer from muscle weakness or other sensorimotor deficits, which are selection criteria for implementing balance bracing in podiatric practice.
Paton and coworkers recently published a systematic review of studies using footwear and AFO interventions to improve balance in patients with sensory neuropathy.28 In those few studies showing benefit of AFO bracing in neuropathic patients, the only brace that demonstrated improvement in balance during dynamic gait was a brace that had articulation with full range of motion at the ankle joints.28,29
Recently, one of the world’s leading authorities on fall risk and prevention spoke out against the trend in the United States in which podiatrists are dispensing bilateral static AFO braces to patients at risk of falling.30 Menz noted there are currently no published randomized trials involving the aforementioned balance brace that have “incident falls as the primary outcome measure.”
This article began with a scenario in which the podiatric physician is compelled to implement a brace or immobilizing device for a frail patient who has suffered trauma. In this case, a non-displaced fibular fracture would require a cast or a walking boot to ensure healing. When it comes to patient safety, clinicians must consider the balance compromise imposed by an immobilizing boot or cast. One could consider a less restrictive device such as an air-stirrup ankle brace, which could be adequate to offload the fracture if the patient was confined to a wheelchair during the healing process.
One significant safety improvement can be the use of a cane by frail patients who must be immobile in a cast, walking boot or rigid ankle brace. A cane improves balance and steadiness in gait for several reasons. Studies have shown that the upper extremity can provide proprioceptive input to improve postural control when the lower extremities are impaired by peripheral neuropathy.31,32 When patients use a cane, stability in gait improves.33 This improvement might also be a simple mechanical effect as patients can bear up to 25 percent of their body weight on a cane during unipedal stance and when they are undergoing perturbation.34
The second scenario presented at the beginning of this article describes an intervention with bilateral static AFO devices intended to actually reduce the risk of falling in frail senior citizens. Given the neurophysiologic effects of a non-articulated brace, implementation of those devices could not expect to improve dynamic balance during gait, according to significant research exploring this topic. Certainly, without any evidence that this type of bracing actually reduces fall risk, recommending or implementing this treatment has no justification.
Finally, there are frail patients who lie somewhere in between the trauma patient and the non-neurologic impaired patient. These are frail patients who have suffered stroke or may have significant peripheral neuropathy, or both. For the stroke patient, there are many studies showing the benefits of AFO bracing to improve stability and reduce the risk of falling.35 In the vast majority of those studies, patients used the brace unilaterally. For the patient with significant sensory neuropathy, there are several studies showing improvements in balance and steadiness during gait when wearing bilateral AFO devices.29,36–38 However, those devices were articulated at the ankle joint, allowing free ankle motion.
In the end, practitioners should follow the “do no harm” principle when implementing brace therapy for frail senior citizens. Other than in patients with hemiplegia or severe peripheral neuropathy, AFO devices have not demonstrated improvement in balance during dynamic gait. Frail elderly patients still require bracing in special circumstances and sound research has shown that unilateral bracing with AFO devices that allow free ankle motion would be less likely to impair balance and stability in gait.
Dr. Richie is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is a Fellow and Past President of the American Academy of Podiatric Sports Medicine. Dr. Richie is a Fellow of the American College of Foot and Ankle Surgeons. He is in private practice in Seal Beach, Calif.
Dr. Richie is the owner of Richie Technologies Inc., which distributes various types of ankle-foot orthoses.
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30. Menz HB. Ankle braces and falls prevention. Available at http://www.hyltonbmenz.com/2018/02/ankle-braces-and-falls-prevention.html?t=1&cn=ZmxleGlibGVfcmVjcw%3D%3D&refsrc=email&iid=6fb640f4a14c419c96d34f52d06d889f&uid=1859304672&nid=244+281088008&m=1 .
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35. Tyson SF, Kent RM. Effects of an ankle-foot orthosis on balance and walking after stroke: a systematic review and pooled meta-analysis. Arch Phys Med Rehabil. 2013;94(7):1377-85.
36. Richardson JK, Thies S, Ashton-Miller JA. An exploration of step time variability on smooth and irregular surfaces in older persons with neuropathy. Clin Biomech. 2008;23(3):349–56.
37. Rao N, Aruin AS. Automatic postural responses in individuals with peripheral neuropathy and ankle-foot orthoses. Diabetes Res Clin Pract. 2006;74(1):48–56.
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39. Lavery LA, Fleishli JG, Laughlin JT, Vela SA, Lavery DC, Armstrong DG. Is postural instability exacerbated by off-loading devices in high risk diabetics with foot ulcers? Ostomy Wound Manage. 1998;44(1):26–3.
40. Hijmans JM, Geertzen JHB, Dijkstra PU, Postema K. A systematic review of the effects of shoes and other ankle or foot appliances on balance in older people and people with peripheral nervous system disorders. Gait Posture. 2007;25(2):316-23.
41. Van Deursen R. Footwear for the neuropathic patient: offloading and stability. Diabetes Metab Res Rev. 2008;24(Suppl 1):S96-S100.
Editor’s note: For further reading, see Dr. Richie’s DPM Blog, “The Truth About AFOs And Fall Prevention,” at https://tinyurl.com/ya8xav35.