Hector W. Kay Memorial Address An Orthotic-Surgical Approach to Stable Seating
R. M. LETTS, MD, FRCS(C)
The disabled population requiring special seating is increasing throughout North America, because of improved medical care of patients having diseases or trauma that results in wheelchair use, as well as the greater longevity of North Americans. Many patients who require wheelchair assistance have the same basic orthotic needs as ambulatory patients with similar diagnoses. The orthotist and surgeon frequently have to work together to prevent pressure sores, deformity, and poor seating. Wheelchair users can be classified into three groups, a) hands-free sitters, b) hands-dependent sitters, and c) propped sitters. Through the use of judiciously prescribed orthoses, assisted by appropriate surgery, patients can frequently be elevated to a higher grouping by achievement of the major goals of seating: comfort, function, and mobility. Sitting stability, i.e. balance of head, arms and trunk, is the cornerstone of good functional, comfortable seating. The pelvis must be stable, the spine straight, and no major contractures of the lower limbs should exist.
Exemplifying the interference of muscle contracture on sitting is hamstring tightness. This frequently results in slouching requiring groin straps to maintain a semblance of proper seating. Hamstring tightness is frequently masked by knee flexion and hampers hip flexion, so the patient spends most of the time sitting on the sacrum. A vicious cycle occurs with increasing hamstring tightness, more slouched seating, then head flexion, thoracic kyphosis, pelvic rotation, and hip extension contracture. The cycle can be broken with hamstring lengthening and supplemented, when necessary, by night splints. Even the common heel cord contracture can interfere with proper seating by predisposing to pressure sores, positioning problems, and inability to wear proper footwear. A major impediment to seating is the windswept hip syndrome, consisting of pelvic obliquity, dislocation of the hip usually on the high side of the obliquity, and lumbar scoliosis. Frequently, pelvic obliquity can be anticipated and prevented by the early treatment of hip abduction contracture through soft tissue release of the adductors and iliopsoas, followed by abduction bracing or custom seating. In children over 5 years of age with spastic subluxing hip, varus osteotomy will be necessary to prevent further development of windswept hip syndrome and maintain both hips in the acetabula with pelvic stability. With stable hips and pelvis, any future scoliosis can be treated much more effectively with a thoracolumbosacral orthosis or for progressive scoliosis, standard methods of stabilization, such as Harrington or Luque instrumentation.
Maintenance of stable hips, straight spine, and lower limbs with no major contractures will result in comfortable seating and allow wheelchair users to function to the maximum of their potentials. This can be achieved through a seating clinic with multidisciplinary input from the orthopedic surgeon, rehabilitation engineer, therapist, orthotist, and other rehabilitation consultants. It is imperative that children enter the program early and that the emphasis be on the prevention, rather than the treatment, of deformities.