ORTHOTIC PRESCRIPTION AND DESIGN
Orthotic prescription, evaluation, and fitting for this population have always been challenging. There exists a wide array of beliefs and protocols for fitting orthoses to children with myelomeningocele. 13 Some clinicians provide orthoses for children by casting them in the natural anatomical position for that child, attempting to prevent further plasticity of the ankle and foot ligaments. This approach may provide greater comfort or ease of positioning so long as the natural anatomical position is appropriate for gait but does not help to correct for joint deviations or deformities that occur within that anatomical position. 2
On the contrary, attempting biomechanically to alter musculoskeletal deformities with aggressive casting and bracing to “correct” gait deviations is also seen as a prescription option. 2 This approach can create excessive loads, which often leads to skin breakdown, particularly on areas of bony prominence. Padding of the orthoses may reduce pressure somewhat, but with extended wear, the reduced pressures do not necessarily alleviate skin ulceration.
Orthotic intervention for myelomeningocele children can begin a few years after birth. Most orthoses prescribed are custom-made ankle-foot orthoses (AFOs), either floor-reaction or posterior solid in design AFOs. 2 Floor-reaction AFOs are particularly beneficial in providing a knee-extension force at the knee, due to the plastic being formed anteriorly at the proximal tibia region and the toe lever footplate, restricting dorsiflexion. 2 Knee-ankle-foot orthoses (KAFOs) and hip-knee-ankle-foot orthoses (HKAFOs) are used proportionally less, but the challenges of orthotic control, and user-compliance associated with orthosis weight and profile, are greatest with children using these orthoses. The numbers of AFOs may be inappropriately high due to the conservative approach of prescribing KAFOs and the challenges of compliant KAFO fitting as mentioned above. 2,6
One factor that affects orthosis design, orthosis compliance, and self-esteem is shoewear. The child with myelomeningocele often presents with clubfoot, which often requires shoes with wider lasts. The use of an orthosis compounds this issue. If a child uses a 3/16-inch AFO, for example, the total width added into the shoe is twice that amount, or 3/8 inches. This limits the type of shoe worn to orthopedic or sport-type shoes.
ORTHOTIC MATERIALS AND FABRICATION PROCESSES
Although the industry-standard material for lower-extremity custom-made AFO bracing is thermoplastics, its process can be somewhat labor-intensive, depending on the design selected. 18,19 For some children, the thermoplastic AFOs are not strong and stiff enough to adequately constrain range of motion at the ankle and knee. Metal bracing is a stronger option but is sometimes too heavy and cumbersome. Alternatively, composites appear promising, but the present state-of-the-art technique for using carbon fiber or fiberglass is a wet-wrap or resin-impregnated laminated procedure. Such a procedure is time consuming and noxious, and the resulting orthoses can be bulky, sometimes heavy, and cannot be post-modified. Existing laminated orthoses are not prevalently used in the United States, but they are used when strength and stiffness requirements are high. 18 These orthoses can be fabricated on site or via central fabrication.
ADVANCED COMPOSITE MATERIALS FOR ORTHOTICS
Over the past several years, investigators at Rancho Los Amigos National Rehabilitation Center have explored means of bringing advanced composites to the forefront of orthotics technology for children with myelomeningocele, in much the same way that it has brought benefits to the aerospace and sports industries. The project goals were to explore the utilization of room-temperature storable pre-impregnated (prepreg) composites in 1) providing stronger, variable stiffness and flexibility, and lighter AFOs for children with myelomeningocele; and 2) demonstrate feasible, safe, and cost-effective methods of AFO fabrication, fitting, and delivery. Advanced composites, which are highly engineered materials developed in the aerospace industry, hold considerable promise for challenging orthotic applications as seen with children with myelomeningocele. These materials differ significantly from the traditional laminated composite systems used both in orthotics and prosthetics at present. Room-temperature prepreg composite materials being explored at Rancho are stronger, lighter, and lower in profile compared with polypropylene or traditional laminated systems, due to the ability to control fiber direction and ply thickness and to optimize fiber to resin ratio levels. For a more detailed description of the Rancho advanced composite AFO development, the reader is referred to other literature. 20–22
The purpose of this research was to:
- 1) determine the types of orthoses and materials used for children with myelomeningocele,
- 2) determine which aspects of current orthotic technology most critically needs improvement, and
- 3) identify whether some of these needs can be met by advanced composite materials.
Moreover, the findings would serve to better provide design goals for the advanced composite project exploring the use of room-temperature storable prepreg materials for AFOs for children with myelomeningocele. Therefore, two surveys were constructed and directed to both certified orthotists and children with myelomeningocele.
Development of the survey began with regular clinical observations of children with myelomeningocele in clinic at Shriners Hospital of Los Angeles. These clinical observations allowed for firsthand exposure to the gait deviations and orthotic challenges of these children. It also allowed for contact on a regular basis with the clinic’s orthotists, therapists, and orthopedists involved. Two different surveys appeared to be appropriate and beneficial: 1) for the child with myelomeningocele, or in case of comprehension or language difficulty, via the parent; and 2) for the certified orthotist treating children with myelomeningocele. In this manner, the study could investigate several relevant issues at interest, including:
- 1) From the orthotist survey:
- Assessment of materials and designs selected and the reasons for selection
- Prescription criteria for AFO types
- Location of AFO material failure, where applicable
- Location of skin problems
- Types of foot deformities.
- 2) From the child/parent survey:
- Assessment of materials and designs used
- Shoe needs and limitations
- AFO comfort
- AFO durability
- Issues associated with social acceptance including peers and cosmesis.
The criteria for the surveys were that the questions should be clearly understood but not slanted toward one response or another, sufficiently detailed, and readily quantifiable. Each survey underwent a minimum of three pilot versions, assessed and validated by both myelomeningocele users/parents and certified orthotists, correspondingly. The final two-page surveys were provided in Spanish and English for the user/parent, but the orthotist survey was provided in English only.
The survey and a cover letter were disseminated via various mailing mechanisms. Certified orthotist surveys were post-mailed to all known myelomeningocele orthotic treatment clinics and facilities across the United States and other orthotic facilities where children with myelomeningocele are routinely fitted for orthoses. The survey was also published online at the Rancho Rehabilitation Engineering Program’s website, http://www.ranchorep.org/survey.html, and was accessible either directly or via the orthotic profession’s website, http://www.oandp.com, which provided a hotlink to the survey. The survey was also disseminated via the oandp e-mail listserve, which provided direct link to the survey. Internet survey accessing could be done either via Netscape Navigator or via Microsoft Explorer browsers, two popular browsers at present time. Furthermore, Internet access of the survey allowed on-screen completion and submission, making it a quick and easy process.
The child/parent survey was mailed out via post mail to the chief orthotist of various Shriners Hospitals and other children’s myelomeningocele clinics across the United States, who disseminated the surveys to the children or via their parents accordingly.
Of the 26 responses received, 35% of respondents were male and 65% were female. Most of the respondents (76%) reported that their lesion was at the sacral level, whereas the rest had a spinal lesion at the lumbar region. Although there was an even spread of foot deformities and conditions, most children (73%) had surgery to alleviate these conditions. All children surveyed used AFOs only, and most (62%) currently used bilateral rigid AFOs (Figure 1).
Approximately 80% of those who responded claimed that the primary reason for needing replacement of an existing AFO was due to growth or changes in medical condition (Figure 2). The remaining 20% stated that replacement was required due to AFO fracture or fatigue. Skin irritation tended to be the largest reported problem associated with unsuccessful treatment, with 29% of the respondents rating it as most troubling.
Sixty percent of the respondents did not think that wearing AFOs was embarrassing, unattractive, or awkward looking. There was no indication of any specific or significant reasons why the children would be discouraged from wearing the orthoses at all times when needed. Contrary to hearsay, heat and weight were not identified as an issue for this sampled population of AFO user. For example, 64% of respondents gave a rating of “least trouble” when asked if the orthosis ever got too warm, and 75% gave the same rating when asked if the orthosis ever got too heavy after long periods of wear. On the other hand, when asked if the children would wear the orthoses more often if improvements to comfort, weight, profile, and cosmesis were addressed, at least 80% responded positively to all the possible changes, as would be expected.
From the various miscellaneous comments indicated, the one suggestion that appeared on various occasions concerned the Velcro strapping used to secure the orthoses to the calf region. The respondents stated that the Velcro damaged household furniture and quickly became dirty or “unsightly” due to lint collection.
Other common miscellaneous comments included concern about limitations of footwear that could be worn comfortably with the AFOs. Eighty-nine percent indicated they wear sneakers; however, 77% would prefer to have more shoewear options.
Of the 32 certified orthotist responses, more than 50% were from non-clinic or non-institutional facilities, whereas 22% were based at “free” clinics or hospitals. The majority of the orthotists (52%) saw between 5 and 15 children with myelomeningocele per month. Most prescribed or fitted a posterior solid-ankle AFO, followed next by the floor-reaction AFO (Table 3). When asked whether there was a relationship between age and the success of treatment, an overwhelming majority (93%) said that the success of treatment decreased as the age of the child increased.
The most critical steps in the treatment process, as identified by the orthotist responses included, patient evaluation, compliance, casting technique, cast modification, material choice, and physical therapy (Figure 3). There was no statistical significance between these factors. The most prevailing reasons why treatment was found to be unsuccessful were increased weight of the child and the user’s preference of a wheelchair over the orthosis for mobility (Figure 4).
The most common occurrence of material failure was near the medial and lateral malleoli areas of the AFO, as expected (Figure 5). Similarly, it was at the malleoli where skin breakdown mostly occurred. Skin breakdown also occurred commonly at the navicular head (Figure 5).
Fifty percent of the orthotists surveyed stated they prefer to use polypropylene material for fabricating AFOs for children with myelomeningocele. Other common preferences were the use of copolymer materials and carbon-graphite reinforcement inserts for the ankle area with polypropylene AFOs. Double-adjustable metal AFOs did not appear to be a preference by orthotists for children with myelomeningocele (Figure 6).
Finally, the most important material characteristics for orthotists were musculoskeletal support and control, durability, and modifiability. Additionally, as expected, 85% of orthotists felt that there was room for new AFO material options for children with myelomeningocele.
Current orthotic devices are mostly fabricated using polypropylene material, and although this is a dramatic improvement over the metal and leather orthoses that preceded it, this study indicates that there are limitations with polypropylene in providing adequate mechanical support, skin viability, and overall comfort.
Considering that most of the certified orthotists surveyed saw between 5 and 15 children with myelomeningocele per month, the survey responses represent an experienced group of clinicians. This study found that growth and/or weight gain of the child with myelomeningocele was the predominant reason for orthosis replacement (Figure 2), although the survey question did not distinguish between growth and weight gain not associated with physical growth. As supported by Figure 4, the authors believe that an associated increase in weight not due to physical growth would increase energy expenditure during orthosis use, decrease comfort and user compliance, and gradually lead to a rejection of orthosis use. It is possible that this theory might explain why many children with myelomeningocele increasingly use wheelchairs as they become young adults.
Specific trends associated with unsuccessful orthosis use, as reflected by both children with myelomeningocele and orthotists, is seen in Figure 7. Both orthotists and children with myelomeningocele rated skin irritation and discomfort as being “somewhat common” to “common” (Figure 7). This may indicate suboptimal biomechanical control due to material limitations and/or short-term weight and growth changes. Both skin irritation and material failure were noted to occur mostly at the lateral and medial malleoli. These are all bony prominences and are more prone to skin breakdown. It is likely that skin breakdown could contribute to greater discomfort levels, although this could be minimized with loss of sensation. It could be postulated that by improving control of the ankle complex with better orthosis design and materials, a reduction in friction and pressure would exist on the localized soft tissues. In turn, this would reduce skin irritation and discomfort levels.
The most commonly fitted orthoses as identified in survey results from certified orthotists were posterior solid-ankle AFOs and floor-reaction AFOs (Table 3). Although survey results show that the orthotists view evaluation of the patient’s condition as a critical step in the treatment process (Figure 3), the results also illustrate that orthotists, prescribing physicians, or the clinic usually has a preference for a particular orthosis design and material (Figure 6). Orthotic fitting for this population is challenging, and it is likely that a preference for an orthosis design and material is one way to keep clinical management of this population manageable.
The most prevalent of all the miscellaneous comments included in the surveys by children with myelomeningocele were about shoewear limitations. In particular, survey responses from female children indicated that they could not wear formal shoes, canvas tennis shoes, or sandals with their AFOs. The AFOs were either too thick or the shoe last and design too small to allow for a comfortable fit. Although this may seem like a trite complaint, the issue of shoe fit and its direct correlation to comfort are very important. Its effect on orthosis compliance and use needs to be studied further.
EFFECT OF SURVEY RESULTS ON ADVANCED COMPOSITE AFO RESEARCH AT RANCHO
Polypropylene is the most commonly used material for lower extremity orthosis, as reflected in this study (Figure 6). The typical profile around the foot and ankle region for lower extremity polypropylene orthoses is usually 5 mm (3/16 inches). This could be thinner or thicker, depending on the size, deformity, and biomechanical needs of the child. Usually, a 5-mm (3/16-inch) polypropylene orthosis provides good support and control, adequate flexibility where intended, and durability. Polypropylene with carbon-graphite reinforcements provides stronger and stiffer orthoses when required, whereas copolymer is also used by orthotists when less rigidity is needed, for example, on very young children with myelomeningocele.
New composite materials are entering the marketplace at competitive prices and often are a fraction of the weight and thickness of state-of-the-art thermoplastic materials. Over the past decade, advanced composite materials technology from the aerospace and aviation industries have become commercially available. These materials are now being explored for orthosis applications at various research and clinic facilities.
The results of this survey provided valuable information to the authors and other investigators at Rancho Los Amigos National Rehabilitation Center, who have been exploring the application of advanced composites for lower extremity orthoses for children with orthopedic disabilities. The results of this study have helped the investigators better establish existing project goals. In particular, this study helped substantiate the need for:
- 1) low-profile orthoses to allow for more shoewear options and
- 2) improving orthosis control of the mediolateral forces about the ankle, while allowing for flexibility in other regions.
The authors would like to acknowledge the assistance of Mr. Dan Snelson, CPO, Chief of Orthotics, at Shriners Hospital of Los Angeles, for recruiting children for the study; the oandp.com website for creating a hotlink to the survey for on-line completion by certified orthotists; the oandp e-mail listserve for allowing the authors to request assistance from certified orthotists to complete the survey form; the College of William and Mary for providing a summer fellowship to Ms. Elliot; Ms. Laura Baum and Ms. Amelia Murti for their assistance in the preparation of this manuscript; and to the certified orthotists and children with myelomeningocele (and their parents) for completing the surveys. Funding for this research was provided by the National Institute of Disability and Rehabilitation Research (NIDRR), U.S. Department of Education under the RERC grant on Technology for Children with Orthopedic Disabilities (#H13350006) and a Mary Switzer Fellowship (#H133F980013-98).
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Keywords:© 2001 Lippincott Williams & Wilkins, Inc.
Orthosis; ankle-foot orthosis; myelomeningocele; spina bifida; polypropylene; advanced composites