Page 82 - Handbook of Electronic Assistive Technology

Chapter 3 • Functional Posture 69

of the trunk and consequent ability to control trunk movements, balance may be affected, as
well as the ability to use the upper limbs for function. With the weight of the upper body on
the sacral area, there may be concerns regarding undue pressure and skin integrity.
There are many reasons why a person may sit in posterior pelvic tilt. Through your
assessment you will need to analyse why this might be. Possible reasons may be tight ham-
string or hip flexor muscles, low truncal muscle tone making it difficult to hold the spine
upright against gravity or abnormal muscle tone contributing to this posture. Alternatively,
you may find that a person may be able to sit with a neutral pelvis out of their wheelchair
but due to technical reasons to do with the wheelchair, the person is ‘forced’ to adopt this
posteriorly tilted position in their wheelchair. For example, the seat may be too deep so
that the person is unable to sit with their pelvis at the back of the seat causing this roll-
ing back posture. Other reasons may be that the hip angle is too acute, the backrest too
upright for the person or the footplate is too low. The upholstery of an in situ sling may
cause the bottom to slip forward. A loose pelvic belt may be a simple cause.
All these clinical and technical reasons need to be considered before a possible solu-
tion can be found. For the person who tends to adopt this posture despite adaptations to
the wheelchair, three points of control are usually required to aid control: posterior to the
pelvis and sacrum to block movement posteriorly, a mechanical block under the thighs or
in front of the knees to prevent anterior movement and a lap strap to stabilize the pelvis.
Sitting With the Pelvis in Anterior Pelvic Tilt
Anterior pelvic tilt is when the ASIS is lower than the PSIS (Fig. 3-12). This causes an
increased lumbar lordosis (inward arching of the lower back) and a tendency to shoulder
retraction (shoulders pulled backward).

FIGURE 3-12 Anterior pelvic tilt�