Adapted Seating

PATRICIA E. WONGSAM, MD*Columbus, Ohio


Special seating clinics have appeared in rehabilitation facilities throughout the United States and Canada over the last 10 years. The First International Seating Symposium, held at the University of British Columbia in Vancouver in February 1983, reflects the growing awareness of this special need of the physically handicapped, especially among children and young adults.

The Adapted Seating Clinic at Ohio State University in Columbus, Ohio, was formed in 1977 as part of the weekly Orthotic Clinic. It has grown over the past several years so that almost 200 patients are now seen annually. As the only formal seating clinic of its type in Ohio, it serves children as well as adults from all over the state and from neighboring states. Among the many patients seen, the most common diagnoses are cerebral palsy, muscular dystrophy, myelomeningocele, spinal cord injury, multiple sclerosis and head injury.

A team headed by a physiatrist consists of physical medicine residents, occupational therapists and orthotists representing orthopedic supply companies, as well as a resident orthotist at Ohio State University. After a complete history is taken and a physical examination is performed by one of the physicians, the case is presented to the team for identification of the problems, discussion and recommendations for appropriate seating. A prescription is formulated to be filled by one of the orthotists attending the clinic. Because of the various experiences of the team members, each one's input contributes to a broad view of the problem and therefore a more complete evaluation and recommendation.

Goals of Seating

Special adapted seating systems provide many functions. Because most patients are expected to spend several hours in their chairs each day, comfort and safety must be considered. Mobility and ease of transportation are also important. Pressure relief is critical, as it has been shown that tissue breakdown occurs when pressure exceeding capillary pressure is maintained. Pressures as low as 70 mmHg for two hours have been shown to produce tissue necrosis. Because of the inability to shift their weight, chair confined patients are more likely to develop pressure sores. In order to prevent this, pressure must be distributed over as wide an area as possible and the pressure localized under the ischii must be decreased by using various padded or contoured seat supports1-7.

Positioning the body in order to maintain or provide for function is mandatory. The upper limbs must be freed from the task of supporting the body in order to be functional, whether for operating wheelchair controls, for daily activities or for communication.

Adequate control of the pelvis, trunk and head is necessary to prevent or arrest skeletal deformities early. Scoliosis, hip dislocation and joint contractures develop rapidly, interfere significantly with function and contribute to a deterioration in health. Abnormal reflex patterns which interfere with function and promote deformities should be recognized and, where possible, controlled. Inadequate head control is a difficult and challenging aspect of positioning but is most important to accomplish, as psychosocial development and communication can be profoundly affected.

Very early positioning and seating of the disabled child is highly recommended. Adapted seating should be considered when it is found that the child cannot support himself or sit like other children his age. The parents may complain that the child is getting too heavy to be carried. The simple umbrella-type stroller does not provide adequate support for the floppy or spastic child and, in fact, promotes scoliosis and limb deformities. As the child grows, a wheeled chair is necessary for encouraging mobility, transportation and social interaction. Tiny wheelchairs which can be maneuvered independently are available. Simple modifications can be made with lateral trunk supports, pads and harnesses to maintain proper posture. When fixed deformities exist, contoured8 or molded seating systems may be required to accommodate the deformities and still provide support.

Principles of Seating

A systematic approach is needed to formulate a seating prescription. The pelvis, which is the chief weight-bearing surface in sitting, should be level, with weight evenly distributed under the ischii and along the undersurface of the thighs. With the hips flexed 85 to 90 deg. and in a midline position, dislocation can be prevented. A solid seat provides the support that cannot be obtained in the sling seat of a standard wheelchair. Lateral thigh pads may be necessary to keep the thighs in the midline. A thigh-adductor pummel may discourage adduction and internal rotation, but caution must be taken to avoid perineal trauma if the patient tends to slide forward in the seat. A seat belt across the hips should be secured to the corner formed by the chair seat and back to maintain the correct position of the pelvis.

Once the pelvis is stabilized, the trunk can be supported against the chair back. The backrest should be contoured to maintain the lumbar lordotic curve and thereby "lock" the posterior vertebral facets, inhibiting forward or lateral collapse of the spinal column which can lead to scoliosis. If trunk position still is not maintained adequately, lateral supports may be added to provide a three-point support system. A chest harness helps to secure the trunk against the back of the chair. A lap tray assists in trunk positioning somewhat and, if the hands are free, encourages two-handed activities in the midline position.

Head control is addressed next and, as mentioned earlier, can be the most difficult and frustrating aspect of seating. Many reflex patterns are controlled by the position of the head on the neck, and therefore has important implications for function. Once the pelvis and trunk are stabilized, head control is more readily approached. Many commercial headrests are available, but no perfect support exists. Support must be applied behind the occiput and neck (Figs. 1a and 1b ), but it is sometimes difficult to maintain the head in an upright and midline position. An important adjunct to a mechanical headrest is stimulation and education of the patient to learn voluntary control. Communication and learning devices located in such a way as to encourage proper head positioning are useful.

Foot placement is dealt with last and is adjusted so as to give stability and balance to the rest of the body. Maintaining knee flexion at 90 deg. helps to decrease the extensor tone that often exists in cerebral palsy patients.

Seating Options

Many types of seating systems are available today. The individual recommendation is affected by the diagnosis, level of functioning, degree of mental impairment and severity of deformities, among the major factors. Lifetime expectations, potential for future improvement and psychosocial needs must also be addressed. Although funding sources are often available, the cost to the patient and family may still influence the seating recommendation.

Systems include simple modified wheelchairs and complicated custom-made and prefabricated appliances. All are time-consuming to make or adjust, relatively costly and imperfect. Some are so complicated as to be intolerable to the patient and family. A system is needed that will meet the goals already mentioned and yet be simple to fabricate, lightweight and practical and, at the same time be sturdy, easily transported and inexpensive.

The present approach to seating the physically handicapped is far from scientific. Extrapolations are made from medical and bioengineering knowledge, but trial and error is still the basic method. A large gap exists between our understanding of the needs of the wheelchair-dependent patient and the solutions presently available. As yet there is no accurate way of completely evaluating or measuring the applicability of seating systems for a given patient. Among the many seating devices available, none is thoroughly satisfactory when all the problems are taken into consideration. In fact, those who work with specialized seating admit to significant frustration because of the inability to satisfy the needs of the patient completely.

The Future

Better understanding of the importance of adequate seating and positioning needs to be promoted, not only among family members of the disabled patient I also among health care providers. Those working with the handicapped should educated to recognize seating problems and be able to make appropriate referrals; The majority of referrals to our seating clinic come from therapists or teachers and seldom from physicians working with these patients.

The need for research in these areas is great. Some useful information and designs have come from the limited number of studies, but more collaboration needed between medicine and bioengineering in order to develop better system seating. Practical application of pressure-measuring devices is needed, an simple and more accurate model should be developed. The concept of a molder contoured "in place" seating device should be encouraged (Figs. 2a and 2b ). Ingenuity and creativity, hopefully with more scientific collaboration, will lead to breakthroughs in the treatment of a problem which affects so many.

*Director, Adapted Seating Clinic, Clinical Department of Physical Medicine and Rehabilitation The Ohio State University Hospitals, Dodd Hall, 472 West 8th Avenue, Columbus, OH 43210.

References:

  1. Drummond, D. S., R. G. Narechanie, A. N. Rosenthal, et al: A Study of Pressure Distributions Measured During Balanced and Unbalanced Sitting. J Bone Joint Surg 64-A: 10341039, 1982.
  2. Holley, L. K., J. Stewart and R. F. Jones: A New Pressure Measuring System for Cushions and Beds-With a Review of the Literature. Paraplegia 17:461-474, 1979.
  3. Houk, R. J.: Evaluation of Seat Devices Designed to Prevent Ischemic Ulcers in Paraplegic Patients. Arch Phys Med Rehabil 50:587-594, 1969.
  4. Kosiak, M.: Etiology of Decubitus Ulcers. Arch Phys Med Rehabil 42:19-29, 1961.
  5. Kosiak, M: A Mechanical Resting Surface: Its Effect on Pressure Distribution. Arch Phys Med Rehabil 57:481-484, 1976.
  6. Mooney, V., M. J. Einbund, J. E. Rogers, et al: Comparison of Pressure Distribution Qualities in Seat Cushions. Bull Prosthet Res 10-15:129-143, 1971.
  7. Reddy, N. P., V. Palmieri and G. V. P. Cochran: Evaluation of Transducer Performance for Buttock-Cushion Interface Pressure Measurements. J Rehabil Res Dev 21:43-50, 1984. 8. Treffler, E., S. Hanks, P. Huggins, et al: A Modular Seating System for CerebralPalsied Children. Dev Med Child Neurol 20:199-204, 1978