Key Insights On Orthotics, AFOs And Casting For Kids

Author(s): 
Guest Clinical Editor: Robert Eckles, DPM

In a continuing discussion of pediatric orthotics, these expert panelists delve into casting children for orthoses, the use of ankle foot orthotics (AFOs) and when to replace or discontinue orthotic devices.

Q:

What fundamental differences are there between your orthotic prescriptions for children and for adults?

A:  

Joseph D’Amico, DPM, notes the fundamental difference between an orthotic prescription for a child versus an adult is the profound developmental potential available in the child that is not present in the adult. As a result, he says the earlier treatment begins in the child, the more favorable the outcome. Due to the plastic nature of the osseous segments, Dr. D’Amico says bone growth and alignment may be influenced in a positive manner to affect structural as well as positional changes achievable in the adult.

Russell Volpe, DPM, generally uses bigger and more aggressive devices in children, particularly younger children. He says kids usually wear sneakers and shoes that can easily accommodate more substantial devices, making this less of a challenge. Dr. Volpe notes deeper and more controlling devices work more effectively to control the foot in the face of the laxity and low tone that are often present in young children. Dr. Volpe tends to post/skive the rearfoot higher in children than in some adults and will avoid extrinsic forefoot posting in the still developing pediatric foot (under age 6 to 7) unless he feels such posting is required to stabilize the deformity.

Additionally, given that most alignment values in the foot continue to improve until 6 years of age, Dr. D’Amico says it may not be prudent to completely neutralize existing deformities in order to allow normal developmental unwinding to occur.

“That is not to say that visible excessive pronation should not be addressed but only that room for improvement should be allowed,” acknowledges Dr. D’Amico. “Frequent monitoring of the child’s progress will encourage the appropriate prescription at different stages in the management program.”

Furthermore, Dr. D’Amico says due to the “fleshy” nature of most young children’s feet, along with the presence of ligamentous laxity, the orthotic degree of correction may of necessity have to be increased to provide satisfactory control. He notes this is especially true in the rearfoot due to increased adipose tissue and the golf ball surface architecture of the region. Deepening the heel seat, increasing the rearfoot post, decreasing undercuts and utilizing optional medial and lateral flanges can be helpful, according to Dr. D’Amico.

Q:

Under what conditions will you prescribe supramalleolar or ankle foot orthotic (AFO) devices for children?

A:

Apart from those who have a primary neurologic diagnosis, Robert Eckles, DPM, says children who express extreme hypermobility—as one may see in those who have Ehlers–Danlos syndrome or Down syndrome—may benefit from supramalleolar or AFO devices. He cites other children who could benefit, such as those with hindfoot coalition, residual clubfoot deformity or in-toe/toe walking gait, which one may see in children with cerebral palsy. Dr. Eckles cautions that the use of such orthoses requires more stringent monitoring for fit, adherence and wear as well as correct and complementary footwear.

Paul Jordan, DPM, says supramalleolar orthoses typically refer to a group of orthoses having medial and lateral uprights or extensions with trim lines just above the malleoli. As he notes, the basic foundation of the supramalleolar orthosis and AFO must be a well thought-out and designed foot orthosis first and foremost.  

Dr. Jordan says extending the medial and lateral trim lines of the appropriately contoured foot orthosis proximally as uprights in contact with the malleoli will permit some additional control of the foot beneath the lower limb at the terminal swing phase of gait.

At times Dr. Jordan has employed medial and lateral uprights in young children to guide, prompt and redirect the frontal plane tibial shift or translation over the weighted foot during play or through transitions of movement from sitting to standing. He suggests one should not design the medial upright of the supramalleolar orthotic in an attempt to directly “push” upon the malleolus in order to try to “hold or resist” the tibia from its medial shift as permitted by the subtarsal-midtarsal joint complex as is often the case with supple pediatric equinovalgus.  

“The supramalleolar orthotic design has little, if any, additional benefit for closed chain control of leg control over the foot in comparison to a below malleolar orthosis,” says Dr. Jordan. “An AFO would be a better solution.”    

Dr. Volpe uses supramalleolar orthoses primarily in children in whom sub-malleolar control will not be adequate because of the overall severity of deformity (often in the place of marked laxity or low tone) or in the presence of neuromuscular deformities for which higher control is beneficial. He says AFOs also have primarily neuromuscular indications though there are a variety of foot and lower leg deformities that benefit from AFO level control (usually as local components of a systemic or neuromuscular disorder).

Dr. D’Amico prescribes supramalleolar or AFO devices for children who are unable to be controlled with conventional orthoses in spite of the incorporation of enhanced control features such as deepened heel seats, medial and lateral flanges, Kirby skive, Blake inverted cast technique and boot type footwear. He says AFOs and, to a lesser extent, supramalleolar orthoses essentially allow extension of the orthotic up the ankle or leg, acting as a lever to further enhance frontal plane stabilization of the otherwise uncontrollable foot.

As with the supramalleolar orthotic, Dr. Jordan says the AFO foundation must be a well thought-out and custom contoured foot base. Without a biomechanically sound foundation, he cautions the AFO is ineffective.   

Dr. Jordan asserts that preformed and prefabricated foot orthoses, as well as prefabricated AFOs, are rarely, if ever, of benefit functionally. If a child is in need of an AFO, he says it is worthwhile to design the foundation and typically the posterior shell of thermoplastic, which extends to approximately an inch below the knee joint.  

Dr. Jordan suspects the most common image of someone in an AFO is to address a flaccid drop foot or steppage gait. However, he notes it is uncommon to see a child with a true flaccid drop foot while the condition is more common in the adult population. In Dr. Jordan’s fairly large pediatric spina bifida population, AFO use to support the foot due to a weak anterior crural muscle is uncommon.

Dr. Jordan notes his patients with cerebral palsy do benefit from the swing phase and stance phase designed AFOs. He says such patients respond well to the tactile cues, sensory input and assisted control of the hip-knee/ankle-foot coupling while learning to walk. Dr. Jordan uses AFOs as learning tools during the differently-abled child’s play and at times says the devices serve as additional “hands” for the physical therapist.  

“To use supramalleolar orthoses or AFOs as augmentative tools for the pediatric patient, both lower limb pathomechanics and the neurological needs must be clearly understood and integrated as part of the design,” says Dr. Jordan.  

Q:

Do you employ a particular casting technique for children? Do you have pearls for casting the very young?

A:

Dr. Volpe uses off-weight plaster in subtalar neutral with cast reduction of frontal plane forefoot position/deformity in the child under 6 or 7. He will sometimes cast in “neutral-plus” position when looking for enhanced control of a lax, high-motion foot. Dr. Volpe has not found casting younger children to be much of an issue. Dr. D’Amico also uses off-weightbearing subtalar neutral Root-type plaster impression casting for all cooperative children.

For the most part, Dr. Jordan says the basic foundation of neutral position while casting applies for all age groups of kids. He says soft tissues are a common consideration in younger children when casting orthotics. Although pressing the child’s foot into a firm foam foundation may be the easiest to perform, Dr. Jordan cautions it almost always results in orthosis failure.

As Dr. Jordan notes, the foot orthosis or AFO can only be as good as the impression cast. As a result, he wraps all of his patients’ feet in plaster to capture the best possible relationship of the osseoarticular uncompensated foot, one way of containing the soft tissues from lateral expansion of weightbearing in the young child. Dr. Jordan notes plaster remains the material of choice for the older pediatric patient as well, noting that the technique one uses will depend on each child’s functional needs, physiological makeup and soft tissue anatomy.  

If the orthosis is to be interactive with the osseoarticular structures in a very young child, Dr. Jordan advises containing the soft tissues. As he notes, a deep heel cup might offer this effect in a young child but not necessarily in the older child or young adult for whom the soft tissue is not as abundant or supple.

Over the past 20 years, Dr. Jordan has found that a slipper cast technique does not offer a benefit as a full “wrap around” plaster impression. If the youngster moves his or her leg, it is more difficult for the slipper cast to move with the child while maintaining the desired subtalar and midtarsal joint position.  

For those not tall enough to allow proper positioning of the foot and ankle in the supine position, Dr. D’Amico will cast in the prone position. He finds it helpful to distract children with games or devices while the plaster sets. For kids under 2, he says it can help to give them a bottle or snack while they are in the parents’ lap. For children who can’t remain still enough for a plaster impression, Dr. D’Amico uses a foam impression with the child seated on a parent’s lap and the knee flexed to 90 degrees. He grips the lower leg and holds the subtalar joint in neutral position with the opposite hand while inserting the foot and leg into the foam. Sometimes Dr. D’Amico will take more than one impression and then see which one most closely represents his clinical findings.

“If the child gets agitated (often from the sensory input of the plaster), I employ the parents to assist me in holding the child’s leg and I take a preplanned and deliberate approach to the cast so I can complete it in as little time as possible,” advises Dr. Volpe.  

In addition, Dr. Volpe makes sure the cast is fully set before removing it in order to prevent deformation. He suggests avoiding foam box casting. Dr. Volpe says it does not, in most cases, provide an adequate negative position for full control.

Q:

What are your policies for replacement and/or discontinuation of treatment?

A:

At the initial visit, Dr. Jordan explains the orthotic process to the parents. He says parents should understand that to discontinue the orthoses by the time most kids are in their mid- to late teens, they must be wearing their orthoses the majority of the time during the week.

“We have a few parents who remove the orthoses once their child has grown and starts to complain about the fit,” says Dr. Jordan. “More often than not, the parents bring the kids back in after hearing more complaints during and after sports activity, night pains return or frequently, the kids realize their running or walking is with greater effort, or they express that they are not as ‘fast.’”

Dr. Volpe will schedule all custom foot orthotic patents for follow-up at a maximum of six months. At that time, he makes decisions about the size and fit of current orthoses, and also reassesses the deformity and the function to determine if treatment will continue with a new prescription.

Dr. D’Amico replaces orthotics when children have outgrown them, are no longer positioning the foot appropriately or their morphology no longer matches the current foot shape. As he notes, children usually outgrow their devices approximately every two years or two shoe sizes with a range of one to three years. He points out that as the child gets older, growth slows so replacement is not necessary as often.
Most children will be able to obtain a two full shoe sizes of growth from their orthoses before replacement, according to Dr. Jordan. He will design devices for adjustability in growth of the width of children’s feet and changes they go through in total stature. Dr. Jordan says length is the only area in which one cannot adjust orthoses. Dr. Jordan does not always have patients return in six months, noting the follow-up period varies, depending on growth in height of the child and changes in midfoot growth. He suggests returning in eight to 10 months, even if the child has not physically grown in foot size or anatomical stature. Dr. Jordan explains the reason is to refurbish or modify the plantar posting that has compressed or distorted over this time.  

Dr. Jordan uses techniques to have the parents assess the hip-knee-ankle-foot changes in comparison to children simply standing in their footwear without and with the orthoses. If there is no change proximally, he suspects that kids are not gaining benefits from the orthoses.

Holding the orthotic against the foot with the child seated is a good method to assess whether the arch has improved with treatment, suggests Dr. D’Amico. If there has been improvement, he says the next step is to have the child stand and assess resting subtalar joint position in the orthotic. Then he says one should place the foot in neutral position and reassess. If the difference is greater than 10 degrees, Dr. D’Amico advocates replacing the device.

Dr. D’Amico says one should discontinue orthotic devices for patients who demonstrate a stance position within 10 degrees of neutral, an essentially vertical calcaneal stance position without orthoses, absence of symptomatology and no observable pronation during stance or ambulation for several encounters over a six-month time period.

Generally, Dr. Jordan reexamines pediatric patients fully to assess changes in history and physical growth. Typically, he will design new orthoses and make new impression casts. Dr. Jordan will discuss the anticipated goals with the parents and child included if he or she is old enough.

“Interestingly enough, almost all of the kids look forward to making a plaster mess that they remember well from the prior visit,” says Dr. Jordan. 

Dr. D’Amico is a Professor and Past Chairman in the Division of Orthopedics at the New York College of Podiatric Medicine. He is a Diplomate of the American Board of Podiatric Medicine, and a Fellow of the American Academy of Foot and Ankle Pediatrics. Dr. D’Amico is in private practice in New York City.

Dr. Eckles is the Dean of Clinical Studies and an Associate Professor in the Department of Orthopedics and Pediatrics at the New York College of Podiatric Medicine. Dr. Eckles is affiliated with the Foot Center of New York in New York City.

Dr. Jordan is a Fellow of the American Academy of Cerebral Palsy and Developmental Medicine, and sits on the Board of Directors for childrens’ medical services at the Tikvah Layeled Center for Cerebral Palsy in New York and Israel. He is also a Diplomate of the American Board of Podiatric Medicine with a private pediatric practice in Smithtown, N.Y.

Dr. Volpe is a Professor in the Department of Orthopedics and Pediatrics at the New York College of Podiatric Medicine in New York City. He is also the Past Chairman of the Division of Pediatrics at the New York College of Podiatric Medicine He is in private practice in New York City and Farmingdale, N.Y. He is also a Diplomate of the American Board of Podiatric Medicine.

To read the first part of this discussion, see “Prescribing Effective Orthotics For Pediatric Patients” in the April 2017 issue of Podiatry Today.

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