Page 83 - Handbook of Electronic Assistive Technology

70 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY

A person may sit in anterior pelvic tilt for a variety of reasons. They may have tight hip
flexor, quadriceps or spinal muscles, which bring the pelvis into this position. Alternatively,
they may rest in this position due to weak abdominal muscles, being overweight or due to
an increased lumbar lordosis. Technical reasons due to the set-up of the wheelchair may
be the cause of this posture, e.g., if the seat cushion is too sloped anteriorly, the back rest
too vertical or has an excessive lumbar contour.
Sitting in anterior pelvic tilt may cause functional difficulties. It may alter the position
of the head, affecting eating and drinking, communication, vision or social interactions. It
may cause the shoulders to retract impacting on the use of the upper limbs. Balance of the
trunk and upper body may be affected due to limited support from the wheelchair. There
may be consequences on pressure loading.
If the person continues to adopt this posture despite adaptations to the wheelchair,
positioning a primary pelvic belt across the ASIS and attaching it to the back of the seat
may be helpful. A secondary strap could then be positioned between 45 and 90 degrees to
the seat to prevent the pelvic belt from riding up into the abdomen.

Pelvic Obliquity
Pelvic obliquity is when one side of the pelvis is higher than the other (Fig. 3-13). As the pelvis
is not symmetrical, there will be a compensatory C-shaped curve in the lumbar and thoracic
spine. The shoulder on the side of the raised ASIS will be lower than the opposite shoulder.
This may be due to asymmetrical muscle strength or tone, asymmetry of bone struc-
ture, soft tissue or the presence of a scoliosis. Some technical causes of pelvic obliquity
may be that the seat cushion is not solid enough, the wheelchair too wide, arm supports
too high or too low or that the person has just not been correctly positioned in their seat.
If the pelvic obliquity is correctable, a small wedge or pad under the lower side of the
pelvis may help to level the pelvis. However, if the pelvic obliquity is not correctable, build-
ing up the seat under the raised side may help to even out the pressure distribution and
load bearing. Care needs to be taken not to overcorrect the obliquity.

FIGURE 3-13 Pelvic obliquity�