By Jonathon Z. Schuch, Meng, PE; Alan Donaldson, MS, OTR; and Peggy Baumgartner, PT
Pediatric seating and positioning have come a long way since the early days in the 1970s. Seasoned clinicians may remember when there was only a single style of wheelchair available and pediatric seating equipment had to be built from scratch. Thankfully, those days are but a distant memory. Today, the clinician has a wide array of seating and positioning equipment to choose from for the pediatric population. In addition, the clinician can choose from a variety of manufacturers and suppliers to mix and match planar, generically contoured, and custom-contoured equipment to best meet their clients’ needs. In fact, it is not unusual these days to see hybrid seating systems that are made up of components from three or more manufacturers. At the University of Virginia Health System (UVA), comprehensive seating and positioning services are provided by specialists from the UVA Musculoskeletal Service Center, UVA-HealthSouth Rehabilitation Hospital, and the Kluge Children’s Rehabilitation Center (KCRC). Pediatric seating and positioning are provided at KCRC by a team composed of an occupational therapist, a physical therapist, a rehabilitation engineer, a rehabilitation technology supplier, a pediatrician, and an orthopedic surgeon. In addition to offering the full spectrum of commercially available seating components and systems, UVA has developed a niche for providing highly customized seating systems to meet the complex seating needs of individuals with severe disabilities. This specialization developed in part as a clinical outgrowth of the rehabilitation engineering research and development activities within the UVA Rehabilitation Engineering Research Center on Seating and Wheeled Mobility (UVA RERC), which was federally funded from 1979 to 1993. The clinical knowledge gained from the high-level research conducted at the UVA RERC, coupled with the cutting edge technologies developed and ultimately transferred to the clinical team at UVA, has enhanced UVA’s ability to provide innovative solutions to the seating and positioning problems faced by individuals with severe disabilities. As a result, UVA regularly provides specialized seating services for individuals with chronic, recurrent pressure ulcers; severe amputations, such as hemicorporectomy or hemipelvectomy; substantial musculoskeletal deformities; and postural instability resulting from severe athetosis. To most effectively and efficiently meet the custom-contoured seating needs of children with severe disabilities, the pediatric seating team often utilizes the computer-aided cushion manufacturing (CAD-CAM) system that was developed by the research engineers at the UVA RERC to custom carve cushions.1 The cost-effective system includes a shape sensing chair, computer interface, and carving machine The custom-contoured cushions can be fabricated while the patient waits—in as little as 10 minutes. Perhaps more important, the CAD-CAM system acquires an extremely accurate body contour by minimizing unnatural soft-tissue distortion during the shape acquisition process. In addition, the system is a valuable clinical tool for evaluating postures and, more important, changes in posture; it provides immediate feedback as to the results and consequences of postural changes. Finally, the CAD-CAM system generates custom-contoured cushions that provide postural control comparable to that of many of the commercial cushions and pressure relief that is simply unparalleled. The CAD-CAM system was originally designed to fabricate seat cushions for adults. However, the UVA pediatric seating specialists recognized the benefits of the system and the custom-carved cushions. As a result, the specialists developed strategies to exploit the system, using it in ways not originally intended, to meet the needs of their pediatric patients. For example, the size and spacing of the contour measuring probes on the shape sensing chair and the associated curve-fitting software render cushion contours that, unless modified, are too wide for the child. In the absence of a pediatric shape sensing chair containing more appropriately sized and spaced probes, the pediatric seating specialists manually modify the shape data to shrink it to the child’s size prior to carving the cushion. Furthermore, the probes’ stiffness often prevents the deflection required to obtain an adequate contour when a child sits on the shape sensing chair. To overcome this obstacle, the pediatric seating specialists gently push the child into the shape sensing chair, increasing the deflection of the probes to render a contour of substantial depth. While the CAD-CAM system was not designed to fabricate back cushions, the pediatric seating specialists often obtain back contours and carve back cushions by placing the child in a supine position on the seat of the shape sensing chair, with hips flexed. Today, the CAD-CAM system is used to fabricate seat or back cushions for children as young as 2 years of age. As a result, the UVA pediatric seating team is able to provide custom carved cushions for children in a most efficient and effective manner. RELIEF OF LOCALIZED SITTING PRESSURE AND DISCOMFORT The human body is not designed for prolonged sitting. However, many children with disabilities sit in their wheelchairs for 8 hours or more without the benefit of voluntary postural change or pressure relief. In a number of cases, the UVA pediatric seating specialists have found that a child’s sitting posture and/or tolerance is a direct function of the sitting force and associated pressure borne at a specific bony prominence. For example, one teenager with mixed athetoid and spastic cerebral palsy could tolerate sitting for a maximum of 3 hours due to soreness and redness of his right ischial tuberosity (IT). This young man was able to clearly identify the location and severity of pain associated with sitting. Another individual with cerebral palsy, mental retardation, and scoliosis had difficulty sitting for more than 2 hours at a time. A comprehensive seating evaluation found that the young girl could not tolerate pressure on her left IT. When an external force was applied to the girl’s IT, she would contort her posture in an attempt to relieve the pressure. This would even occur when the therapist palpated the girl’s IT while lying supine. For these two individuals, seat contours were obtained and modified to provide site-specific pressure relief. These modified contours were then carved from highly resilient polyurethane foam for maximum pressure relief. In both cases, the teens have been able to significantly increase their sitting tolerance without discomfort or adverse reaction. In the case of the young man who could provide verbal feedback and guidance to the seating intervention, he rated the comfort of the custom-carved cushion as an 8 on a 1 to 10 scale, compared to ratings of 1 and 5.5 for the two previous cushions provided by other facilities. Similarly, in a follow-up conversation with the mother of the young woman, the mother reported that she loved the cushion. Similar results have been obtained for children with chronic recurrent pressure ulcers. By creative modification of the contour, which results in a redistribution of the sitting forces, cushion interface pressures can be significantly reduced at areas of concern. This is one of the principal attributes of the cushions carved by the CAD-CAM system. SUPPORT OF MUSCULOSKELETAL DEFORMITIES The UVA pediatric seating specialists have also used custom-carved seat cushions for children who have significant musculoskeletal deformities that compromise sitting. These deformities may be flexible, fixed, or a combination of both. Generally speaking, the UVA team tries to correct deformities that are flexible, while accommodating deformities that are fixed. If a child has a fixed scoliosis and resultant pelvic obliquity, he or she is at risk of developing a pressure ulcer, due to unequal weight-bearing on the seat cushion; with the child’s upper torso balanced in the sagittal plane, the low hip bears the brunt of the child’s body weight. In cases such as this, the UVA pediatric seating team typically designs a hybrid system that combines the custom-carved seat cushion with another style of contoured back, thereby providing the child with maximum pressure relief in the seat cushion and maximum upper body support via a stiffer, and often deeper, contoured back cushion. POSTURAL STABILIZATION FOR ATHETOSIS One of the more challenging seating cases involves the provision of a supportive system for children with athetoid cerebral palsy. In these cases, the child requires postural stabilization for functional pursuits. In the absence of a supportive seating system, the child will develop compensatory stabilization strategies, such as crossing the legs, placing the arms behind the back in a locked position, or sitting with a posterior pelvic tilt and stable, yet undesirable, kyphotic posture. Over the years, the UVA pediatric seating specialists have learned that it is quite difficult to correct a person’s compensatory stabilization strategies once these strategies have been developed. The specialists find that doing so often compromises the person’s functional capabilities, causing them to reject the seating intervention. In cases such as this, especially cases where the child sits with a posterior pelvic tilt and kyphotic sitting posture, the UVA team occasionally uses custom-carved seat cushions to enhance postural stability while simultaneously providing pressure relief at the coccyx. Whenever possible, the pediatric seating team tries to correct the child’s sitting posture, reducing the posterior pelvic tilt to the degree that the child will be able to sit in the correct posture without compromising functional independence. CUSTOM-CONTOURED SYSTEMS FOR CHILDREN Custom-contoured seating systems can be expensive, especially for children who are growing or undergoing postural changes. In cases such as this, the custom-carved cushion(s) represent a cost-effective alternative to the other custom-contoured systems available on the market today. For example, the UVA pediatric seating team has implemented custom-carved seat and back cushions for very small children undergoing rapid growth. When the child outgrows the cushions, new contour data are obtained and cushions carved. Keeping in mind that the process of gathering contour data, editing the data as needed, and carving a cushion can take as little as 10 minutes, it is easy to see the cost benefit of this approach. To date, custom-carved cushions have been provided to children with cerebral palsy, spina bifida, spinal cord injury, traumatic brain injury, and other less-common disabilities. The UVA pediatric seating team has found that the CAD-CAM system developed by the UVA RERC and the custom-carved cushions generated by the system significantly enhance the team’s ability to meet the complex seating needs of children with severe disabilities. The CAD-CAM system provides a cost-effective method for fabricating custom-contoured cushions, allows for the creation and re-creation of extremely accurate seating contours by minimizing unnatural soft-tissue distortion during the shape acquisition process, and serves as a valuable clinical tool for evaluating postures and postural changes. While the system was not originally designed to fabricate cushions for children, the UVA pediatric seating specialists have devised ways to manipulate it to meet the needs of their pediatric patients. As a result, the CAD-CAM system is used to fabricate seat or back cushions for children with a variety of disabilities and with a variety of seating needs. Jonathon Z. Schuch, MEng, PE, is an assistant professor of medical education and rehabilitation engineer at the University of Virginia Health System, Charlottesville. He is also a licensed professional engineer within the Commonwealth of Virginia. Alan Donaldson, MS, OTR, is an occupational therapist specializing in pediatrics at the Kluge Children’s Rehabilitation Center (KCRC) also in Charlottesville. Peggy Baumgartner, PT, is a physical therapist who has specialized in pediatric rehabilitation in her 25 years at KCRC. Reference 1. Brienza D, Chung K, Inigo R. Design of a computer aided manufacturing system for custom contoured wheelchair cushions. Proceedings of the International Conference of the Association for the Advancement of Rehabilitation Technology; 1988:312-313.
