The normal size and shape of the spine is different from
person to person and no-one's spine is completely straight.
When viewed from the side the spine has four normal
curves (see "Your Back"). The
cervical region has a lordotic posture with the mid portion further forward
than the upper and lower regions. The thoracic region has a kyphotic
profile. This is the reverse of a lordosis with the mid portion curved
towards the back. The lumbar region is again lordotic, and the profile
of the spine is completed by the kyphotic profile of the sacrum and coccyx.
Any of these curves may be or become exaggerated for a
variety of reasons. In the thoracic region the kyphosis
is usually less than 40o, but some "normal" individuals
with have a thoracic kyphosis of up to 60o. Where the
kyphosis is excessive (> 90o) there can be limitation of
respiratory function, but this in an uncommon situation.
Patients who suffer from inflammatory conditions such as
Ankylosing Spondylitis have a tendency
to develop a progressive, and in some cases severe kyphotic deformity of all
regions of the spine. This type of deformity can cause quite marked
functional limitations, and for sever cases surgery can be very effective way
of resorting a more normal spinal contour and will literally improve these
patients outlook on life.
The spine is usually straight when viewed from either in
front or from behind. Where there is a deviation from this normal
posture there may be a scoliosis.
True scoliosis is not just a
curve to the side but the vertebrae at the apex of the curve are also twisted
or rotated which affects the ribs and results in the typical clinical features
of unilateral rib or scapular prominence.
Spinal deformities are either postural (flexible and not
fixed) or structural. Postural deformity usually develops as a
result of pain or poor muscular support and corrects with attention to the
underlying problem. A structural deformity on the other hand is one
where secondary structural changes develop in the skeleton that limits the
degree of correction that can be achieved.