Keys To Prescribing AFOs For Senior Patients
Given the escalating number of people who will become senior citizens in the years ahead, this author examines the potential of ankle foot orthoses (AFOs) to treat common conditions in this patient population. He also offers several AFO prescribing pearls and key insights on helpful modifications.
In 2011, the oldest baby boomers started turning 65. Every day for the next 19 years, more than 10,000 more will cross that threshold.1 Most changes in gait that occur in older adults are related to underlying medical conditions — particularly as conditions increase in severity — and should not be viewed as merely an inevitable consequence of aging.2-4 Early identification of gait and balance disorders, and appropriate intervention can prevent disability and loss of independence.
Performing activities of daily living while maintaining postural stability and balance requires the interaction of multiple sensory motor systems that include vision, vestibular function and muscle strength. All of these functions decline with age. The bottom line is that ankle flexibility, sensory function and muscle strength are significant independent predictors of balance, functional ability and mortality.5,6
As foot and ankle specialists, we are in the unique position to initiate treatment that can improve strength and flexibility for our senior patients. Moreover, as prescribers and suppliers of footwear, orthotics and ankle foot orthoses (AFOs), we have the opportunity to mitigate further risk in this patient population by correcting gait and balance deficits. These two risk factors are among the top risk factors for falling.
Ankle foot orthoses, functional foot orthotics, diabetic footwear and other durable medical equipment (DME) items all offer our senior patients with foot and ankle deficits efficacious, conservative and noninvasive treatment options that often obviate the need for surgery. Yet in spite of these obvious advantages, there are large numbers of podiatric physicians who still choose not to provide these valuable services.
According to a 2010 CMS report, podiatrists billed the most common HCPS code used for custom gauntlet type AFOs (L1940) an average of 0.7 times per year.7 Yes, that is less than one AFO on average per year.
Medicare policy is clear that patients are covered for custom AFOs if they have documented orthopedic risk factors that often contribute to gait deficits, falls or instability.
Obviously, AFOs are not the only tools we have at our disposal to reduce the incidence of falling, gait deficits and disability among our senior populations. The medical literature is replete with articles highlighting the benefits of physical therapy, exercise, proper footwear, education, orthoses and other assistive devices like canes and walkers.
However, ankle foot orthoses can be of great benefit in treating the following conditions in our senior patient population.
• Foot and ankle osteoarthritis
• Foot and ankle postural instability/imbalance
• Flaccid foot drop
• Posterior tibial tendon dysfunction with a collapsed talonavicular joint/ accessory navicular
Seniors face common challenges that are intrinsically related to aging. The combination of extrinsic factors along with these intrinsic issues can significantly reduce quality of life and can even impact mortality. Osteoarthritis contributes significantly to abnormal gait and postural control.
In a landmark study by Verghese and colleagues, abnormal gait (neurological, non-neurological and a combination of both) predicted a statistically significant increase in institutionalization and death.8
According to Menz and co-workers, foot and ankle problems affect up to 80 percent of “older people” and are associated with impaired mobility and ability to perform common household tasks.9
However, despite the high prevalence of foot problems and the significant impact these impairments have on older people, they often go unreported because many older people consider foot and ankle pain an inevitable consequence of aging rather than a medical condition.10,11
Pertinent AFO Considerations For Foot and Ankle Osteoarthritis
Clinicians have utilized AFOs for many years to stabilize osteoarthritic joints with the goals of reducing motion and minimizing ground reactive forces to the involved joint. Without question, a gauntlet style AFO is the best fit for these purposes.
Although articulated devices have been proposed and can offer some benefit, custom gauntlet style solid ankle AFOs perform better for pain reduction and biomechanical control.12 In a 2006 article, Huang and colleagues reported that a solid gauntlet style AFO is the best option (over an articulated style) for those with ankle osteoarthritis arising from ankle motion.13
However, clinicians must take care to choose accommodations that will benefit the senior patient’s needs. Although some have deemed gauntlet style AFOs as less advantageous because of the absence of a functional foot orthosis (FFO), most quality labs can incorporate a good FFO into a gauntlet style AFO. For those with isolated subtalar joint osteoarthritis, an articulated style of gauntlet AFO may be of benefit so as not to lock normal ankle joint range of motion.
Additionally, one must assess the trim lines of the AFO you are prescribing. Most quality AFO manufacturers such as Arizona AFO, Langer Biomechanics and others can offer at least one style of AFO (the Arizona Standard AFO) with specific trim lines designed to control both the ankle and subtalar joint. These companies also offer an AFO style with trim lines that will lock the ankle while leaving the subtalar joint free. An example of this would be the AZ Sporty. Choosing the right trim line for your gauntlet style AFO can be critical for patient adherence and success.
While the “standard” style gauntlet AFO is very familiar to the podiatric physician, this trim line style may not always be necessary if the patient does not have osteoarthritis in the subtalar joint. The photo above at left and the next two photos below demonstrate three common types of trim lines available for the osteoathritic patient in order to maximize normal motion while offloading the affected joint effectively.
The most common issue in prescribing a gauntlet style AFO for senior patients is getting them to fit into an acceptable shoe.
Any gauntlet style AFO will naturally take up space in the shoe, often resulting in the need for a different style or size shoe. Choosing footwear that can accommodate the AFO and the patient’s foot without being too bulky, heavy or aesthetically unpleasing can be challenging. Lycra (stretch) styles with extra depth are usually the best options but the length of the AFO footplate and the style of the AFO will determine the best shoe style. Having a stock of shoe styles that fit well with AFOs can be extremely valuable when dispensing and assessing the AFO on the patient.
First, consider the options available for AFO topcover material. Although the classic leather gauntlet AFO offers greater stability and remains the gold standard for maximum stability and support, one may consider materials that are less bulky and lighter in weight. The Arizona AFO utilizes a more lightweight, breathable synthetic material (AZ Breeze) than leather and can often be a better alternative for seniors or patients with diabetes.
Nine Prescribing Pearls On AFOs For Osteoarthritis In Senior Patients
• Consider a plastic thickness appropriate for the patient’s body size. You can specify this with the central fabrication facility from which you obtain your AFO. Make sure the patient’s body size and weight match the chosen thickness of plastic for the inner shell of the gauntlet.
• Educate your senior patients about the need for proper footwear to use with their AFO in order to achieve the best outcome. We often set ourselves up for failure by not taking the time to set the right expectations for our patients with regard to what they are getting and what will be required of them to achieve the best outcome.
• Keep in mind that anything that limits too much motion in a senior patient can reduce balance and increase the risk for falling. Studies have suggested that a solid style AFO can reduce balance and postural stability in compromised senior patients, and one should avoid this unless other pathologies exist that necessitate a solid style.14
• Adding extrinsic posting to the AFO can be valuable in some cases in which frontal plane deformity exists. However, these accommodations will often require more space in the shoe.
• Increased heel/foot height in a senior patient can reduce postural stability and thus increase the risk of falling. One should ensure careful selection of the proper style of AFO and footwear in order to keep the patient as close to the ground as possible.
• Full-length foot plates are valuable under some circumstances (i.e. a significant forefoot deformity that needs accommodation). However, these modifications can reduce balance and often require a bigger shoe.
• Don’t sacrifice comfort and padding for your senior patients. A thin layer of Plastazote or a pocketed accommodation over at-risk areas around the ankle or foot can add comfort and improve adherence.
• Velcro is always optimal with senior patients.
• For severe osteoarthritis of the ankle, subtalar joint or both, an extended style of AFO can be extremely effective.
Can AFOs Help Address Postural Imbalance And Fall Risk?
According to the most recent studies, the top risk factors for falling among seniors include weakness, balance deficits and gait deficits.15,16 Several articles have clearly demonstrated the link between the benefits of a flexible style AFO for those with postural imbalance/instability.
Cakar and colleagues stated that a flexible style AFO can reduce fall risk while several studies have highlighted the fact that an AFO can not only improve postural stability but also proprioception around the foot and ankle through enhancement of somatosensory feedback.17,18
Researchers used bilateral AFOs to assess balance in a patient with severe neuropathy and a history of frequent falling. The study showed the use of AFOs significantly improved overall balance test performance. Without the AFOs, the patient had falls performing most of the tests.19
Clinicians have used AFOs for decades for those at the highest risk for falling but only in the last few years have we seen an AFO style designed for the senior patient in mind. The Moore Balance Brace, which I developed in 2010, has become another useful tool for the podiatric physician, physical therapist and the orthotics and prosthetics specialist in an effort to impact the risk factors for falling among our senior patients. The brace’s lightweight design and flexible trim lines along with its unique posting have made this thermoplastic posterior leaf style AFO (hinged and standard) a significant and impactful tool for those treating the at-risk senior patient.
The following additional considerations are vital in order to select the right style of AFO for those seniors at risk for falling.
• First and foremost, one must perform a biomechanical fall risk assessment to identify the specific risk factors involved. As I noted earlier, weakness, balance deficits and gait deficits are reportedly among the top causes of falling among seniors.15,16
• Senior patients who already have risk factors for falling (i.e. history of falling, weakness, joint instability) must have symmetrical treatment for the best outcome. Thus, bilateral AFO bracing is critical when addressing a severe ataxic, unstable gait.
• Any AFO used for balance must be lightweight and easy to don. While this is true for all AFOs discussed in this article, it is critical to make sure the patient receives proper training on how to put on and take off the AFO. This can make or break the success of any AFO among seniors.
• In addition to being lightweight, a balance AFO must be flexible so as to stabilize the ankle and improve postural stability, but not so solid as to limit the normal range of motion still available.
• A flexible or hinged gauntlet style AFO, like the Moore Balance Brace, is critical to maximize somatosensory contact, thereby improving proprioception around the foot and ankle. In my experience, most patients have more than ample flexibility with the non-hinged standard Moore Balance Brace, but there are some who will benefit more from the hinged version (i.e. those who need more stability but more sagittal plane flexibility).
• Lightweight, balanced footwear is critical to the success of any AFO used for the improvement of balance. This one point is probably what prevents more success when utilizing a balance AFO.
• Easy donning and doffing is critical for any AFO designed for a senior. However, ordering Velcro attachments for these patients with no loops or strings can be an easy way to improve adherence. Strings, loops and hooks, while very valuable in many styles of AFOs, can create more difficulty for a senior.
Essential Insights On Utilizing AFOs For Drop Foot
While utilizing AFOs for drop foot patients has been widely accepted and understood for decades, clinicians must carefully consider a few important factors when ordering the right style for more senior patients.
While not a disease in and of itself, drop foot is a symptom of an underlying pathology that can include a stroke, a traumatic brain or spinal cord injury, spinal stenosis, multiple sclerosis or a peroneal nerve injury.
The goal of any AFO for this condition is to promote toe clearance while limiting the speed at which the foot plantarflexes. In short, the goal is to prevent the foot from dropping during the swing phase of gait (drop foot).
Typically, the drop foot AFO will extend from distal to the metatarsal heads to just distal to the head of the fibula. In the PDAC definition of an L1960 AFO, the proximal edge cannot be higher than 1½ inches below the head of the fibula. In some cases, the foot plate may extend to the entire length of the foot. Topcover materials for the foot are optional but can be advantageous for those (the majority) who may be at risk for skin breakdown.
While most AFO manufacturers make some version of a posterior leaf style AFO, choosing between a simple posterior leaf design versus a dorsiflex assist device is critical.
Here are some key considerations to bear in mind when prescribing AFOs for drop foot in senior patients.
• Deciding on a solid posterior leaf design versus a dorsiflexion assist AFO for the severe drop foot deformity can be challenging. Proper AFO selection must be preceded by a thorough gait assessment.
• If there is any degree of contracture or spasticity present, a solid style AFO should be of primary consideration. If there is no contracture and the foot and ankle are flaccid, clinicians should consider a dorsiflexion assist device.
• If the trim lines of the AFO fit anterior to the malleoli, one can achieve more rigid immobilization. This style of AFO is beneficial when ankle instability or spasticity is of chief concern.
• AFO trim lines posterior to the malleoli (posterior leaf spring type of AFO) will facilitate plantarflexion at heel strike, and push-off returns the foot to neutral for the swing phase. This provides dorsiflexion assistance in instances of flaccid or mild spastic equinovarus deformity, and furthermore is preferable over a more rigid device.
• Keep in mind that solid style AFOs (depending on the plastic thickness and trim lines) can often be easier to fit into a shoe than a hinged device. However, stretchable shoe styles with some extra depth can easily accommodate the extra space required.
• In some circumstances, one can order an extrinsic post (to be added to the AFO) to better accommodate a varus or valgus contracture. As I noted above, an extrinsic post will most certainly take up shoe space and often will require a larger or Lycra style shoe.
• Consider that a high percentage of patients with drop foot have profound neuropathy on their affected side and can accordingly be at risk for ulceration. It is for this reason that a full-length multi-density insert can be helpful and even necessary in some cases.
• While a simple plastic posterior leaf style AFO with no top covering or posting is the easiest style to don and doff without significant shoe size changes, some patients need padding or top covering (Plastazote) on the orthosis to reduce pressure and friction while increasing comfort.
• While podiatric physicians should make every effort to try to provide the senior patient with the lightest and easiest device to fit into a shoe, do not compromise on what the patient needs to be active and stable. Over-bracing is bad but under-bracing can be worse.
• The Tamarack joint system used in many dorsiflexion assist devices is a lightweight joint that one can easily incorporate into most AFO styles, including gauntlet and open ankle (Sporty style) designs. Incorporating the Tamarack system into an AFO with a synthetic covering and a custom Plastazote orthosis can be an excellent combination of accommodations to reduce pressure and provide more foot support.
• Velcro attachments around the ankle and at the upper leg should always be preferred over laces.
• Adding a Plastazote lining to a plastic AFO can be a great tool to reduce the risk of skin irritation.
• Clinicians should take care to address edema in these patients as this can significantly impact AFO fit around the ankle and especially in the upper leg.
• Advocating compression garments with use of the AFO is recommended.
When Patients Have Posterior Tibial Tendon Dysfunction (PTTD) And Talonavicular Joint Collapse
While much has been written and discussed regarding the use of AFOs for the common pathology of posterior tibial tendon dysfunction, less has been written on how to address the painful collapsed talonavicular joint.
While some advocate the traditional double upright hinged AFO with an accommodated functional foot orthosis, it has been my experience that these devices most often fail in the setting of a collapsed talonavicular joint or prominent navicular.
Many common AFO designs often actually worsen the pain at this area because of the trim lines of the AFO. In most gauntlet style AFOs commonly prescribed for PTTD/talonavicular joint collapse, the medial flange wraps around the foot’s medial arch, forcing the prominent navicular into the orthotic plate and causing even more pain. While sweet spots, padding and proper casting have all received discussion in regard to addressing this problem, I have had the best success with a “pocket” style AFO with an extrinsic post to offload the talonavicular joint. This dynamic pocket style AFO will be commercially available in the near future.
While many with PTTD may not need such a modification, this modification can be extremely valuable for those with prominent and chronically painful talonavicular joints, especially on or around the navicular. However, no pocket style AFO can work without some extrinsic posting to “suspend” the painful joint complex off the ground. Accordingly, there is a need for a dynamic pocket style AFO with extrinsic posting to hold the medial column off the ground.
Here are some key pearls for prescribing AFOs for patients who have PTTD and talonavicular collapse.
• It is critical to cast these patients in such a way to capture the dynamic state of the patient’s deformity. Semi-weightbearing casting often does not capture the location of the talonavicular joint in a dynamic natural state of standing or walking. This can lead to accommodations that do not adequately fit the patient’s anatomy.
• The dynamic pocket style AFO not only supports the medial ankle but also suspends and pockets the prominent talonavicular joint or accessory navicular. An additional layer of Plastazote can even further reduce pain and make these devices much more comfortable.
• An extended full foot plate with Plastazote lining can be very comfortable and reduce pain, but will also make this much more difficult to shoe. Keep this in mind when ordering a full foot plate with or without a Plastazote orthosis.
• A gauntlet style AFO is essential to fully control ankle motion in these severely pronated patients but also keep in mind the possibility of a more open ankle trim line that allows more ankle joint range of motion.
• An extrinsic post below the pocket works great in the clinical setting if one ensures proper casting and marking of the cast.
• These patients often need a Lycra style shoe that can stretch or a larger size shoe.
• Velcro is essential and it is often preferable to leave the AFO in the shoe for donning.
In summary, our ever growing senior patient population has unique needs that we as podiatric physicians can meet with the right tools and education.
As with any job, practice makes perfect and there is no better way to learn about AFO styles and casting than visiting a lab or attending an educational seminar.
There is no single “go to” AFO for every condition and you certainly cannot get away with the same style of AFO for every condition. Learning the available trim lines and being familiar with different AFO accommodations and topcover materials can make a big difference.
However, the biggest challenge in enhancing AFO outcomes is learning what shoes work well with specific styles of AFOs. Having the right AFO is only half the battle if you do not prepare the patient for the possible requirement of a different style or type of shoe. Preparing the patient and setting the right expectations are critical to achieve optimal results.
Dr. Moore is board-certified by the American Board of Podiatric Orthopedics and Primary Podiatric Medicine. He is the Fellowship Director of the Central Kentucky Diabetes Management program, serves as adjunct faculty at the Kent State University College of Podiatric Medicine and serves on the Board of Trustees of the American Academy of Podiatric Practice Management. Dr. Moore is a managing partner of Cumberland Foot and Ankle Centers of Kentucky.
Dr. Moore has disclosed that he is the developer of the Moore Balance Brace.
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