lower Back pain syndrome
SPINE
FICURE 10. Angulation of planes of
vertebral facets. The angulation that
detennines the direction of movement
at various vertebral levels is depicted
significant movement is barred to these segments. In this generalization
of total spinal movement the cervical spine segment is intentionally
excluded
TOTAL SPINE
The total vertebral column can now be visualized as the sum total of all
the functional units, superimposed one upon the other, in an erect
jointed column balanced against gravity and capable of movement.
Having studied the functional anatomy of the individual functional
unit, we can now study the total vertebral column from a static and a
kinetic viewpoint.
The static spine as observed from the side has three basic
physiologic curves. A fourth curve, that of the coccyx below the sacral
base, is a non mobile inflexible curve with no pertinent effect upon
man's attempt to maintain his balance in the erect position, and, therefore,
its consideration is omitted in the study of the physiologic curves.
The entire spine is balanced on the sacrum, at its base, as a flexible
segmented rod is balanced by a juggler. Immediately above the sacrum,
the lowermost curve is the lumbar lordosis. This lordosis is convex
anteriorly and forms its curve within a five vertebral body segment. The
next curve, cephalad to the lumbar lordosis, is the thoracic curve which
is termed the "dorsal kyphosis." The thoracic curve has its convexity
posteriorly and being composed of 12 vertebrae has a curve of lesser
curvature than is present in the lumbar curve. The bones of the thoracic
vertebrae are smaller, and the discs are thinner, each disc being less
pie-shaped than its comparative disc in the lumbar region. The cervical
lordosis is the uppermost physiologic curve with an anterior convexity
similar to the lumbar lordosis, and because of smaller vertebrae, thinner
discs, and different bony configurations forms a smaller arc.
All three curves--the lumbar, the thoracic, and the cervical-in their
ascent, must meet in a midline center of gravity to balance the weight
distribution of the curve and to counter the eccentric loading of each
curve. The side view of the three physiologic curves in the erect
position may be considered as posture (Fig. 11).
The sacrum is the foundation platform upon which is balanced the
superincumbent spinal column (Fig. 12). As the sacrum is firmly attached
to both ilia, these bones move en masse as one unit, constituting
the pelvis. The pelvis is centrally balanced on a transverse axis between
two ball-bearing joints formed by the rounded femoral heads of
the femors fitted into the cuplike acetabular sockets, which permit a
rotatory motion in an anterior-posterior plane. By pivoting in a rotatory
manner between these two lateral points, the pelvis may rotate back
and forth, simultaneously rocking and changing the angle of the sacrum
(Fig. 13).
Movement of the pelvis on its transverse axis constitutes "rotation" of
the pelvis. Upward movement of the anterior pubic portion of the
pelvis, termed "upward rotation," has the effect of lowering the sacrum
with a decrease in the sacral angle. Downward movement of the front
portion of the pelvis, called "tilting" of the pelvis, elevates the rear
portion of the pelvis, changes the angle of the sacrum, and increases the
sacral angle. The sacral angle is determined as the line drawn parallel
to the superior border of the sacrum measured in relationship to a
horizontal line. The plane upon which the lumbar curve is balanced
and ascends is thus variable and can change in its inclination according
to the relationship of the pelvis.
As the lumbar spine ascends upward at an angle perpendicular to the
level of the sacral surface, the acute angle of the sacrum causes the
FICURE 11. Posture. The physiologic curves
of the erect vertebral column transect the
center of gravity (eG) at the regions shown
lumbar spine to arise at a slight vertical angle. Thus the lumbar spine
needs only a slight degree of arching to return to midline. With an
increase in the sacral angle, due to tilting of the pelvis, the plane of the
sacrum becomes more obtuse, the lumbar spine takes off at a sharper
angle to the horizontal and must, therefore, arc through a sharper curve
to return to midline. The greater the sacral angle, the more angled the
lumbar take-off demands that the curve which will bring the spine back
into center of gravity balance must be even sharper. Those few words,
"the greater must be the curve," specify essentially a greater lordosis of
the lumbar spine.
In contrast a smaller angle brought about by elevating the pubic
bone which depresses the sacrum, thereby decreasing the angle of the
