Evaluating the Adult with Cerebral Palsy for ... - Physical Therapy

PRACTICE
limited number of clients, who often have low muscle tone
rather than high muscle tone.
Therapists should assess the foot-support system in the
fitting chair. Because many clients for adaptive seating have
hamstring spasticity or knee flexion contractures beyond 75
degrees, footrests extended in front of the casters in the usual
position are not appropriate. To prevent the hamstrings from
functioning as hip extensors, a foot box or lengthened foot
support may be used to allow 90 degrees or more of flexion
at the knees (Fig. 2). The foot box should extend forward
beyond the reach of the heels and back under the seat as
needed. Calf panels or pads should not be used with this type
of foot box to avoid hamstring facilitation.
When the client is seated fully upright, a tray may be
suitable for support much the way we use a table or desk top.
Plans for the tray should usually be determined during the
assessment process. The fit, height, and tilt of the tray are
important in achieving the best posture and muscle tone. A
tilted tray may help to maintain hands in midline and in
contact with each other. A tray may also be essential for
clients whose muscle tone decreases excessively when the hips
and trunk are at a 90-degree angle. The tray may be provided
with a high inner rim for trunk support, or it may provide
support only through the arms as the elbows rest on the tray.
Fig. 1. Optimal angle of the seating unit can be determined by
placing a wedge beneath front casters to observe varying angles of
tilt.
DISCUSSION
Bergen and Colangelo noted that "a majority of clients with
disorders of tone show a posterior pelvic tilt when sitting"
because of "overactivity of hip extensors. " 2(p5) They also noted
that the posterior tilt leads to the full extension pattern. The
pelvis must, therefore, approximate as nearly as possible the
normal anterior tilt position in sitting. Wedging the seat
invariably increases the posterior tilt in clients who lack full
hip mobility. This loss of the anterior tilt is the reason that
wedging of the seat has often been unsuccessful in correcting
the problem of extensor spasticity in sitting.
Underlying the practice of wedging is the firm belief that
reducing the angle of the hips to 90 degrees or less inhibits
extensor spasticity. That premise is not in question here. If
the pelvis is tilted posteriorly, however, the hip angle may
only appear to be 90 degrees. The true angle of the hip will
often be significantly greater than 90 degrees. The true angle
determines whether spasticity will be inhibited.
The reclining position, often used with a wedged seat for
severely spastic clients, is successful only in a passive sense.
As spasticity subsides and the client relaxes, he may sink back
into the seat rather than extending out of the wheelchair.
Moreover, extensor activity is not reduced by reclining and
may actually increase. In the aforementioned EMG study by
Nwaobi et al, reclining the back as little as 15 degrees with
the hips maintained at 90 degrees flexion produced more low
back extensor myoelectric activity than when the back was
straight upright. 7 At 30 degrees of a reclined position, with
the hips maintained at 90 degrees, extensor tone was still
higher. The results of this study suggest that reclining a client
either elicits the supine tonic labyrinthine reflex, or contact
of the back or the head with a headrest initiates the extensor
response. Nwaobi et al do not speculate on either of these
reactions as possible contributing factors. 7 In either event, we
must be aware of the results of this study and carefully assess
Fig. 2. A foot box extended back behind the uprights and under
the seat prevents the hamstrings from extending the hips.
the effects of reclining the backrest or tilting the insert when
positioning our severely involved cerebral palsied clients.
CONCLUSION
Not all clients can be positioned or assessed as I have
described, and so these procedures have exceptions. Some
clients may require surgical correction before they can be
brought to an upright position. Those with severe hydrocephalus
or very low tone may be unable to bear the full weight
of the head and trunk vertically. The fitting chair will reveal
instances where clients have used postural reflexes or hypertonicity
for function. Unfortunately, it may not be possible
to provide a substitute that will allow the client as much
Volume 65 / Number 2, February 1985 211
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