Seating and positioning for disabled children and adults

Chapter 44 Seating and positioning for disabled children and adults

People with disabilities are living longer, and their number is growing. In 2003, 34.3 million people (12.1% of the population) in the United States (noninstitutionalized) had physical limitations in activities due to a chronic condition. An estimated 1.6 million are wheelchair users. Baby boomers are coming of age and are acquiring disabling conditions. By the year 2030, the number of elderly will double to 71.5 million. Medical technology has improved the rate of survival for children and adults with disabilities and their long-term management. Long-term debility is a major risk factor for pressure ulcers. Improvement in the survival rate has increased the number of persons at risk for pressure sores. An estimated five million people in the United States have chronic wounds. From 1.1 to 1.8 million people develop new ulcers each year, and the financial cost and emotional burden are heavy.4,49 The two groups at highest risk are the elderly and persons with spinal cord injury (SCI).3,19 Advances in seating and mobility have made a difference in controlling deformities, preventing pressure sores, and expanding the individual’s potential in life, ensuring participation socially, educationally, and vocationally. Proper seating is like an external orthosis, important for support, comfort, and pressure relief in sitting.18 Better anatomical alignment of the pelvis and trunk enhances physiological functions, such as swallowing and cardiopulmonary function, and affects upper extremity function. Postural supports enhance functional movement by decreasing the influence of abnormal tone and reflexes, thereby improving postural alignment and potential access to technologies, such as powered mobility, communication devices, and computers (Fig. 44-1). The seating system should be as dynamic as possible to allow for growth changes in a child or if a decline in function is anticipated. The seating system must be user friendly for the person in the wheelchair and for the caregiver. The user, family, and caregivers play a key role and must be interviewed extensively regarding the user’s medical and functional needs, environmental considerations, and lifestyle issues.

The best prescription involves an evaluation process by a team of professionals knowledgeable in the medical issues. The evaluation should identify physical abilities and limitations, predict functional capabilities, identify problems with existing seating, and set goals to match the user’s needs with the seating technology. The end result will be the recommendation of a useful and functional system.

Evaluation process for seating and mobility systems

A seating and mobility system evaluation should address all aspects of a person’s medical and personal lifestyle issues. The following categories should be assessed thoroughly.

Medical History: All medical diagnoses (primary and secondary) are important to identify and document as well as whether the disability is stable, progressive, or fluctuates. Pertinent history that will have an impact on mobility and positioning needs includes history of pressure sores, spasticity management, medications, orthotic use, and sitting tolerance. A detailed interview regarding pressure sore development, management, and successful treatment is important in preventing recurrence. Prior and future surgical interventions, such as spinal fusion, muscle releases, and amputations will affect seating decisions. Prior equipment use and identification of previous problems is helpful in justifying future seating intervention.

Physical Assessment: Physical assessment includes the person’s range of motion, skeletal alignment or posture, motor strength or motor control of the head, trunk and extremities, sitting balance, sensation, interfering tone, or reflexes. Is the muscle tone low or hypotonic? Does the client have hypertonicity, which may require more aggressive seating components to control tonic movement?

Range of Motion: Range of motion of the joints and spine assesses whether postural supports can correct or must accommodate perceived deformities. Flexibility and asymmetries of the hip and pelvis and hamstring tightness are critical areas of assessment. Evaluating asymmetries in hip flexion, scoliosis, and pelvic obliquities and determining whether the deformities are fixed or flexible is important to determining successful solutions. Seating starts from the pelvis and hips, so assessment of pelvic obliquity, scoliosis, tight hamstrings, and hip muscles is critical for ensuring proper positioning.

Reflex-Influenced Posturing: Is reflex-influenced posturing interfering with the patient’s functional potential for maintaining the sitting position? For example, two influential primitive reflexes active in seated posture are the tonic labyrinthine reflex, which causes extension of the head, trunk, and extremities as the body tilts backward or reclines, and asymmetrical tonic neck reflexes, which cause rotation of head, trunk and pelvis and potentially a windswept deformity. At times, this reflex posturing is functionally used to extend the upper extremity in order to drive a power wheelchair or point to a communication device. Persons with athetosis or dyskinetic-type movement disorders may use reflex posturing for stability in order to use their extremities purposefully. The seating device may help inhibit unwanted movements and permit functional movements.6

Muscle Strength: Evaluation of muscle strength assesses functional potential with, and the need for, appropriate postural supports. The need for adequate support for sitting balance and pressure distribution versus adequate freedom of movement must be balanced. Overseating can discourage functional potential. For example, a high back on a person with functional low-level tetraplegia would eliminate his or her ability to balance the upper body or to hook the arm over the push handle of a lower back in order to increase forward reach with the opposite arm. Evaluating muscle strength helps determine whether posturing is compensatory for muscle paralysis, weakness, or imbalance. Clients with Duchenne muscular dystrophy have proximal muscle weakness and are able to increase their upper extremity reach by leaning forward and to the side. Restricting trunk motion limits their ability to compensate for proximal weakness in order to reach with and use the distal strength in their hands.

Evaluation of Protective Sensation: Evaluation of protective sensation and assessing for red areas or potential pressure areas helps to determine the appropriate seating surface. History of scar tissue or previous pressure sore intervention can predict areas of high risk. Aging affects the elasticity of the skin and increases risk of damage from shearing, pressure, heat, and moisture.

Functional assessment

Everything the person presently can accomplish from the seating system should be addressed in the functional component of the evaluation. This includes all areas of mobility-related activities of daily living: self-mobility, ability to stand and ambulate, transfer, manage the bladder, and drive a vehicle. New seating and mobility systems should not interfere with any previously independent abilities. For example, some persons with tetraplegia need to open the seat to back angle by reclining the back of the wheelchair in order to empty their bladder. Replacing the power back recline with a tilt-in-space system may affect bladder function by not allowing the person to empty the bladder as previously accomplished. Swingaway trunk supports allow trunk movement but lock in for stability when needed. Environmental accessibility, including school or work sites, and the person’s recreational activities must be explored.

Transportation: Issues related to safe transportation of the person as a driver or passenger include tiedown (securing the wheelchair in a vehicle while the person is seated in it), wheelchair seat height, breakdown of the wheelchair for loading into a car, or overall length of the mobility base on van lifts.

Cognitive Status/Behavioral Assessment: Cognitive status/behavioral assessment includes memory skills, problem-solving abilities, ability to comprehend, concrete versus abstract reasoning, destructive behavior, motivation, and safety judgment. For example, clients who are agitated or have destructive tendencies require seating that is protective and durable so that body parts are not accidentally injured against hardware.

Visual/Perceptual Ability: Individuals who cannot separate head movement from eye movement can compensate for visual field cuts by head posturing or trunk movement. Compromises in seating supports are necessary to compensate for visual impairments. The position of the head and upper body in space affects visual field.

Other considerations include cosmesis, financial constraints, caregiver management, and changes that may occur due to physical, cognitive, or medical reasons.

The outcome of evaluation of a person’s seating needs focuses on one of three areas in a framework for seating and positioning decision making categorized by Cook and Hussey9: technologies for postural control (typically for the child or client with cerebral palsy), technologies for pressure control, for those at high risk (e.g., population with SCI), or technologies for comfort (for the elderly or patient with amyotrophic lateral sclerosis).

Seating alignment

Ideal sitting alignment is different for an able-bodied person than for a disabled person, and depends on the individual’s abilities. Sitting is dynamic; it is a continuous process of postural changes whether the position is task oriented or one of rest. For the able-bodied person, a sitting posture with an anterior pelvic tilt and decreased lumbar flexion is the most favorable posture.17,18,40 Generally three postures of sitting alignment are assumed (Fig. 44-2). Ideally, an upright, symmetrically balanced trunk over a stable pelvis allows better upper extremity reach, head control, and visual field. However, in the sitting position, the pelvis tends to roll back into a posterior tilt because the hips are flexed and the hamstrings pull the pelvis back; the tilt is accentuated when the knees are extended.50 The line of gravity is posterior to the ischial tuberosities. This posture is adopted as a position of rest by an able-bodied person and as a position of stability by a wheelchair user with tetraplegia. The second sitting position is achieved by activating the back extensors to tilt the pelvis anteriorly into lumbar lordosis. As the pelvis rolls anteriorly, the line of gravity falls directly through the ischial tuberosities.15 This posture usually is assumed by a person with muscular disease as it is functionally advantageous because of weakness that is greater proximally than distally.16 The third seated posture is a forward sitting posture that has been described by Kangas25 and Adrian and Cooper1 as a functional task position or position of readiness. In this position, the trunk is forward and the line of gravity shifts toward the direction of activity. The trunk flexes forward in a position of anticipation. The arms and trunk are naturally brought forward into the visual field, and the feet are shifted backward behind the knees and bear more weight.

Outcome studies of seating and positioning for function

A number of studies reported on how seating affects functional activities, upper extremity function, head control, and visual field.24,33,36 The components of a seating system can provide support to align the body, normalize tone, prevent deformities, and clearly influence upper extremity movement. In one study, the sitting surface was explored to better determine the capacity to maintain balance and posture as a prerequisite for activities of daily living. The center of pressure of reaching was determined to be significantly greater on a generically contoured sitting surface than on a flat foam surface or a 3-inch Roho seat cushion.2 The effect of different backrest heights and types of cushions were investigated in the SCI population to determine the relationship between posture and upper extremity reaching. The posture adopted by the user and the American Spinal Injury Association (ASIA) score were significant, and no evidence indicated that the type of cushion or back height affected reach.48

Improvements in autonomic functioning, including respiratory, oral intake and digestion in children with cerebral palsy was found following adjustments in seating systems with improvement of the trunk, neck and head alignment.7 Hulme23 found positive perceived changes in social interaction, positioning, tracking, grasping, and self-feeding skills. Nwaobi37 found that the vital capacity in children with cerebral palsy improved with positioning in a seating system versus a sling type wheelchair. Improvements in speech intelligibility were documented in children with cerebral palsy using adapted seating versus without.34

Reports on the effects of seating on upper extremity function are conflicting. In a 1986 study of children with cerebral palsy, different amounts of hip flexion were found to affect upper extremity function.36 Another study found that children with cerebral palsy were able to activate and release a switch the fastest when they were in an anterior 15-degree tilt or in the position of readiness versus 0, 15, or 30 degrees of tilt back.35 However, McPherson et al.31 found no significant differences in the quality of upper extremity movement in subjects with cerebral palsy in four different positions. Seeger et al.45 also did not find any improvement (Fig. 44-3).

Seating assessment

Hands-on evaluation should be performed with the person either sitting or supine on the mat. Critical assessment of whether deformities are dynamic or fixed is more accurate when the patient is supine. Depending on the person’s disability, a mat assessment is not always mandatory. The three main determinations of the hands-on evaluation are as follows:

Classifications and description of sitting ability

The ability to sit independently is one factor that determines the type or amount of seating support needed. Hoffer21 classified a person’s ability to sit according to the amount of trunk control present. His classifications were modified by Tredwell and Roxborough in 1991 to include generalizations regarding the type of seating needed (Fig 44-4):

Hands-Free Sitting Ability: Maintains independent sitting for long periods without using hands for support. Demonstrates good trunk balance and the ability to weight shift. In general, a person needs a simple seating system designed primarily for pelvic stability, comfort, and mobility (e.g., person with paraplegia).

Hand-Dependent Sitting Ability: Requires either one or both hands for support. Trunk control and balance are generally poor. Trunk supports are needed to allow use of hands for functional activities. Providing a more stable base of pelvic support may change a hand-dependent sitter to a hand-free sitter.

Propped Sitting Ability: Because of severe physical involvement or structural deformity, the person is unable to sit without total body support. Trunk and head control are very limited. Total support of the trunk, head, and extremities is needed, as for a person who demonstrates total body involvement with cerebral palsy, has a severe muscle disease, or has a high-level tetraplegia.

Patterns of deformity

The position of the pelvis influences the alignment of the trunk and therefore of the shoulders, upper extremities, and head. The three common patterns of postural malalignment are as follows28:

Symmetrically Slouched: This position begins with a posterior pelvic tilt. The trunk collapses into a C curve, and the shoulders are protracted with the head forward. The most common cause of a posterior pelvic tilt in persons with cerebral palsy is hamstring hypertonicity. For persons with tetraplegia, the symmetrically slouched position can be a position of stability in which they are able to raise their arms for balance and functional activities28.

Lordotic Posture: This posture begins with an anterior pelvic tilt. The pelvic tilt locks the lumbar facets into extension, mechanically providing spinal stability. Hyperlordosis typically is observed in patients with Duchenne muscular dystrophy prior to spine fusion because of proximal weakness and an imbalance in strength between the abdominals and back extensors.

Asymmetrical or Windswept Posture: This posture is one of the most difficult deformities to control and to treat. The windswept deformity is described as being windswept to the left if the left thigh is abducted and the right thigh is adducted. It is associated with a triad of deformities: dislocated or subluxed hip usually on the adducted side, pelvic obliquity, and scoliosis. A dislocated hip may be painful, severe scoliosis may compromise cardiopulmonary function, and the increase in pelvic obliquity increases the risk for pressure sores.12,41 The person may try to offload the painful hip, which worsens the position and pressure distribution.

The relationship among windswept hips, pelvic obliquity/hip dislocation, and scoliosis was first described by Letts in 1984 in children with cerebral palsy. “Acquired and preventable Special Seating will NOT prevent a contracted hip from dislocating.” However, Letts did advocate abduction of the lower extremities to 25 degrees and not just neutral to decrease abnormal muscle activity.27 Increased abduction also results in good approximation of the head of the femur into the acetabulum, which promotes bony joint development in children. Therefore, flexion and abduction of the hip are recommended to prevent extensor and adductor posturing in children with cerebral palsy who are at risk for development of the windblown syndrome. Without adequate fixation of the pelvis, however, this position may be difficult to obtain.

High complication rates have been documented in patients with severe neuromuscular scoliosis: 81% by Loinstein30 in 1984 and 48% by Boachi8 in 1989. They believed that the high risk of surgery outweighs the benefits, so comfortable seating is the treatment of choice. Table 44-1 lists possible causes and equipment solutions for postural alignment problems.

Table 44-1 Causes and equipment for patterns of deformities

Problem Cause Equipment Solutions
Slouched posture    
Posterior pelvic tilt Sling upholstery Three-point control: solid seat, firm back, and pelvic/hip seat belt
    Rigid anterior pelvic support: subasis bar, knee blocks
  Inappropriate seat depth Measure from PSIS to popliteal, include fixed kyphosis
Hip/knee extension Extensor tone (hip and knee) Antithrust seat
    Increase hip angle >90 degrees
    Increase knee angle >90 degrees (foot placement behind knee)
  Hip extension contracture Accommodate seat cushion to unilateral contracture
Thoracic kyphosis Trunk weakness/paralysis Unilateral split seat or leg trough, to maintain trunk upright
  Fixed deformity Recline back, tilt back in spine
    Lower back height, accommodate in back cushion
Shoulder protraction Spasticity/weakness Firm back with lumbar/thoracic extension
  Back height too high Appropriate back height
    Accommodate with molded back
    Shoulder straps pulling up and back
Forward head posture Weakness Occipital support with capital extension
  Spasticity Head band (stationary or dynamic) attached to head rest
  Reflex posturing if too reclined Recline back or tilt back to seat angle
Rotational/oblique posture    
Pelvic obliquity/pelvic rotation Sling seat Firm seat
  Scoliosis Lateral hip guides
  Hip dislocation Flexible: build up under low side for even pressure
  Asymmetrical hip ROM Fixed: build up under high side, relieve pressure under low side
    Custom-molded seat
    Off-set cut-out in cushion
    Accommodate seat depth for leg length discrepancy
    Anterior pelvic belt
    Two-piece sub-ASIS bar
Hip problems Sling seat Firm seat with medial thigh support
Hip adducted—internal rotation Adductor tone Medical thigh support
Hip abduction—external rotation Hypotonia Lateral thigh/knee stabilizers
  Fixed deformity Accommodate
Windswept hips Pelvic rotation Three-point control: hip guides, medial, and lateral thigh support
Adducted thigh with abducted thigh Dislocated hip Build up for lack of thigh support
  Scoliosis Custom-molded seat
Thoracic scoliosis Pelvic obliquity and rotation Three-point control: pelvic/trunk supports
Flexible Weakness Deep contoured back or trunk supports
  Spasticity Rotational deformity: curved supports
Fixed Asymmetric tone/muscle strength Custom-molded back or adjustable-tension back upholstery to accommodate to rib hump deformity
Asymmetric head posture Scoliosis Appropriate support of pelvis, trunk, and shoulder girdle
  Fluctuating tone  
  Reflex posturing Head and neck support. Support of occiput to mastoid process or over the ear to the temple for lateral control
  Visual compensation Stationary or dynamic headband
Lordotic posture    
Anterior pelvic tilt Muscle imbalance Placement of belt across ASIS
Hip flexion Abdominal weakness Wedge seat/cushion to accommodate if fixed
Thoracic lordosis Contractures Tilt in space manual or power frame, adjustable seat angle
    Anterior chest support: molded chest plate, wide Velcro strap
Retracted shoulders Spasticity Appropriate pelvic/trunk positioning with chest support
  Posturing for trunk weakness Shoulder wedges
Extended head posture Spasticity Neck ring
  Weakness Occipital support
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Jul 12, 2016 | Posted by in ORTHOPEDIC | Comments Off on Seating and positioning for disabled children and adults

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