Current Insights On The Benefits Of Custom Orthoses And AFOs

Author(s): 
Guest Clinical Editor: Bijan Najafi, PhD

These expert panelists discuss the pros and cons of custom foot orthoses and their biomechanical benefits, whether ankle foot orthoses (AFOs) can prevent falls in older patients, and how to prescribe orthotics for older patients.

Q:

How we can explain the controversy regarding the benefit of custom foot orthoses for the management of foot pain?

A:

Although custom foot orthoses seem to be a patient-centric intervention for foot pain in comparison to prefabricated foot orthoses, Bijan Najafi, PhD, says the research does not show significant benefits of custom devices in comparison to prefab devices from a biomechanics standpoint. He asserts that this controversy is mainly due to the fact that those studies often consider change in peak pressure as a primary outcome and notes this may not be relevant to describe the biomechanical benefits of custom orthoses.

   Dr. Najafi notes custom foot orthoses reduce peak pressure via redistribution of plantar pressure while prefab orthotics often reduce peak pressure due to shock absorption. Biomechanically, he says there is a significant difference between these two phenomena since the first custom devices help to enhance dynamic plantar loading while the prefabricated devices reduce local peak pressure without changing the shape of pressure profile.

   Dr. Najafi cites a recent study revealing that with normal and healthy arches, the statistical distribution of plantar loading is similar to a Gaussian shape whereas in patients with a painful abnormal arch like pes cavus, this shape has far from a normal distribution.1 The authors proposed an index named dynamic plantar loading, which represents the self-similarity between plantar pressure probability distribution with a Gaussian shape.2 They demonstrated that custom orthotics can enhance the dynamic plantar loading index while prefab orthotics are unable to change this index.

   Karl Landorf, PhD, GradDipEd, DipAppSc(Pod), does not consider there to be much controversy about custom versus prefab devices. He notes randomized trials have found that both custom and prefab orthoses are beneficial for patients, and systematic reviews have found custom and prefab devices are beneficial for foot pain and can prevent injury in highly active people.3-5 However, Dr. Landorf warns that practitioners need to be aware of the evidence so they prescribe orthoses for appropriate conditions.

   Dr. Landorf says there is more controversy with trials that have compared customized orthoses to prefabricated orthoses. He notes many studies have found that appropriate prefab devices, appropriately contoured foot orthoses for example, are just as effective as custom orthoses for many conditions (e.g. plantar heel pain).6

   Those who understand pathomechanics have the option of incorporating orthotics into the treatment regimen for many maladies, according to Gene Mirkin, DPM. An orthotic can lessen or resolve pain, and he says success makes it easy to espouse the virtues of orthotics.

   On the other hand, Dr. Mirkin notes that when people do not buy into or understand biomechanical contributions to pain and injury, they have “a closed mind” and are not necessarily willing to try this approach, and therefore are naysayers about the benefit of orthotic therapy. He argues the cost of custom orthotics also comes into play for some of the non-believers of orthotic therapy, who may think of the devices as an expensive therapy that patients do not always need. Dr. Mirkin also says the reimbursement may motivate some providers to dispense them because the coverage is available.

Q:

Can ankle foot orthoses (AFO) prevent falls in older adults?

A:

Dr. Mirkin believes AFOs can prevent falls in older adults. Although AFOs should not be standard wear once a person reaches a certain age, he believes the devices are indicated for certain conditions. In cases of neuropathy (diabetic, unknown origin), arthritis, nerve damage (post-cerebrovascular accident, spinal nerve injury from osteoporosis with collapsing vertebrae against a nerve) or general muscle weakness, he feels AFOs can provide a stronger base that people need to reduce the risk of falling.

   When tendons are unable to support joints and patients have an inability to feel where limbs are located without looking, these factors can lead to a greater risk of falling in Dr. Mirkin’s experience. He says a brace that limits motion when there is too much or helps compensate for a weakness can only help.

   In those 65 years of age and over and particularly in those over 75 years of age, Dr. Najafi says plantar sensation will be diminished. When this is combined with lower extremity muscle weakness, it can cause a higher risk for falling, according to Dr. Najafi. He cites recent studies suggesting that custom ankle foot orthoses may enhance proprioception via interfacing with sensate skin around the shank segment.7,8 He says the studies also note that custom AFOs provide stability in the ankle joint, particularly in medial-lateral direction, without limiting the motion in anterior-posterior direction (which is required for a healthy gait).9 This in turn may help older adults to have better balance with stable walking, says Dr. Najafi, who notes that further research is required to validate this hypothesis in older adults.

   Dr. Landorf notes that the question of fall prevention in regard to AFOs remains unanswered as no randomized controlled trials of AFOs have been conducted with documented falls as the main outcome measure. Although there is a possibility that AFOs could enhance balance by providing additional sensory feedback, he says one needs to balance this against the possibility of restricting motion in the ankle/rearfoot complex, which could be detrimental to balance and potentially increase the risk of falling.

   “We are in the early days of research in this area so it may still be some time before we know the answer with certainty,” says Dr. Landorf.

Q:

Biomechanically, what are the benefits of custom foot orthoses?

A:

Dr. Najafi cites the major benefits of custom devices.

   Reduction of plantar pressure and enhancement of dynamic plantar loading. As Dr. Najafi notes, custom devices can reduce plantar pressure via redistribution of plantar pressure. They also help to enhance normal probability distribution of plantar loading, which he says is of key importance to reduce lower extremity pain during walking.

   Dr. Landorf says custom orthoses have a substantial effect on plantar pressures as orthoses redistribute plantar pressure from the forefoot and heel to the midfoot or arch area. He notes orthoses do so by increasing the surface area over which the weightbearing surface is distributed.

   “From our research, the effect on plantar pressure is by far the clearest to evaluate and is the most outstanding out of all the biomechanical measures we have at our disposal,” says Dr. Landorf.

   Stabilization of the foot during walking. Dr. Najafi says an appropriate design of custom foot orthoses helps maintain the center of pressure line of progression in neutral position (middle of base of support). He notes this helps stabilize the foot, which in turn reduces the risk of injury and enhances gait stability and balance.

   Enhancing proprioception feedback. Dr. Najafi notes a custom orthosis can also enhance proprioception feedback by forcing the ankle joint to navigate the foot to stabilize the center of pressure. As he notes, this in turn helps stabilization of gait and enhancement of balance during walking.

   As Dr. Mirkin notes, excessive movement, impact, tension or pressure are bound to cause trouble. Orthotics change all of those factors depending on the degree of support (varus/valgus), the type of materials used (rigid, semi-rigid or flexible) and what kind of accommodative padding one places on top, according to Dr. Mirkin. He says one can choose those materials to limit painful joint motion, lessen the pull on damaged or strained tendons and ligaments, and direct force/pressure and shear away from areas or skin that are painful or break down.

   Dr. Landorf emphasizes that the biomechanical effects of foot orthoses are of interest but patient outcomes are the most important issue when evaluating foot orthoses. That said, Dr. Landorf notes it is clear that foot orthoses offer small changes in kinematics and muscle activity although the changes are quite variable in patients so it is somewhat difficult to explain.

Q:

What are the most important outcomes that one should consider when designing foot orthoses for older adults?

A:

Getting rid of pain or a pressure sore and preventing injury are the ultimate successes when it comes to orthoses, says Dr. Mirkin. Since we heal slower as we age, he suggests fostering an understanding that orthotics are part of a healing process that takes time and that patients should expect longer break-in periods. He says although rigid orthotics may seem biomechanically necessary, older adults may not tolerate them well.

   As Dr. Najafi points out, among older adults, falls and a fear of falling could cause a dramatic reduction in mobility, which he says impacts one’s quality of life, independence, frailty, and leads to a further increase in the risk of falling. Dr. Najafi feels the main focuses of foot orthosis design should be reducing the fear of falling as well as the risk of falling. He says many recent studies addressing the benefit of foot orthoses in older adults often neglect the importance of fear of falling, which he says is even more important than the risk of falling.

   For instance, Dr. Najafi says if an appropriately designed AFO may enhance the self-confidence of an elderly patient to be more active, it could also reduce the risk of falling in the long term via the enhancement of lower extremity muscles and vascularity, both of which are key to enhance balance during walking. Accordingly, he says along with assessing the benefits of foot orthoses on gait and balance in older adults, one should also consider fear of falling and changes in spontaneous daily physical activities as primary or at least secondary outcomes.

   Dr. Landorf asserts that the number one goal of orthoses is their benefit to the patient and that one should assess these benefits through appropriate patient-reported outcome measures. He notes that some form of empirical evaluation using a valid and reliable outcome measure will ensure proper follow-up of patients receiving foot orthoses. Prior to this, appropriate biomechanical effects (e.g. redistribution of plantar pressure) and comfort of the orthoses are significant factors that he says physicians need to address. While trying to gain maximum biomechanical effects may seem a worthy goal, he emphasizes that comfort of the orthoses is just as important.

   Finally, Dr. Landorf says shoe fit is also a key factor when providing foot orthoses for older adults so a fundamental consideration is having good quality, appropriate shoes to begin the whole process of prescribing orthoses. Dr. Mirkin also advocates considering the shoe in which the patient is going to use the devices. He says the orthosis may be perfect but won’t work if the patient can’t fit it into the shoe.

   Another consideration for older adults is enhancing the form factor for everyday applications, according to Dr. Najafi. For instance, he points out that most walking in older adults is happening indoors while most of the current designs of foot orthoses are for outdoor shoes.

   “A better form factor design is required to enhance gait and balance in indoor walking including house shoes as well as custom socks with a component of foot orthoses,” argues Dr. Najafi.

   Dr. Najafi is an Associate Professor of Surgery, the Director of the Interdisciplinary Consortium on Advanced Motion Performance (iCAMP), and a faculty member of the Southern Arizona Limb Salvage Alliance (SALSA) at the University of Arizona College of Medicine. He is a Scientific Member of the University of Arizona Center on Aging, an Associate Member of the Arizona Cancer Center, and Advisory Board member of the Arizona Arthritis Center.

   Dr. Landorf is a Senior Lecturer and Research Coordinator in the Department of Podiatry and Leader of the Lower Extremity and Gait Studies (LEGS) Program at La Trobe University in Bundoora, Australia.

   Dr. Mirkin is board certified in foot surgery by the American Board of Podiatric Surgery and board certified in foot and ankle orthopedics by the American Board of Podiatric Medicine. He is a Fellow of the American College of Foot and Ankle Orthopedics and Medicine, and a Fellow of the American Society of Podiatric Surgeons. Dr. Mirkin is in private practice in Maryland.

References
1. Najafi B, Wrobel J, Burns J. Mechanism of orthotic therapy for the painful cavus foot deformity. J Foot Ankle Res. 2014, in press.
2. Najafi B, Crews R, Armstrong DG, Rogers LC, Aminian K, Wrobel J. Can we predict outcome of surgical reconstruction of Charcot neuroarthropathy by dynamic plantar pressure assessment? A proof of concept study. Gait Posture. 2010; 31(1):87-92.
3. Hawke F, Burns J, Radford JA, Du Toit V. Custom-made foot orthoses for the treatment of foot pain. Cochrane Database Syst Rev. 2008 Jul 16;(3):CD006801.
4. Collins N, Bisset L, McPoil TG, Vicenzino B. Foot orthoses in lower limb overuse conditions: a systematic review and meta-analysis. Foot Ankle Int. 2007; 28(3):396-412.
5. Landorf KB, Keenan AM. Do foot orthoses prevent injury? In MacAuley D, Best T (eds.) Evidence-Based Sports Medicine, Blackwell Publishing, Massachusetts, 2007, p. 73.
6. Landorf KB, Keenan AM, Herbert RD. Effectiveness of foot orthoses to treat plantar fasciitis: a randomized trial. Arch Intern Med. 2006; 166(12):1305-10.
7. Tyson S, Sadeghi-Demneh E, Nester C. A systematic review and meta-analysis of the effect of an ankle-foot orthosis on gait biomechanics after stroke. Clin Rehabil. 2013; 27(10):879-91.
8. Zissimopoulos A, Fatone S, Gard S. The effect of ankle–foot orthoses on self-reported balance confidence in persons with chronic poststroke hemiplegia. Prosthet Orthot Int. 2013; epub ahead of print.
9. Yalla SV, Ortiz J, Crews RT, Najafi B. Balance improvement in older adults using customised ankle foot orthoses. Footwear Science. 2013; 5 (sup1):S119-S120.

   For further reading, see “Point-Counterpoint: Do AFOs Have A Role In Fall Prevention?” in the October 2013 issue of Podiatry Today or “Secrets To Fabricating Effective Custom Orthotics” in the June 2004 issue.

   For an enhanced online experience, check out Podiatry Today on your iPad or Android tablet.

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