lower Back pain syndrome
SPINE
FICURE 12. Static spine considered erect posture (relationship of physiologic curves to
plumb line of gravity). Left: Lateral view of the upright spine with its static physiologic
curves depicting posture. Right: The change in all superincumbent CUNes as influenced
by change in the sacral base angle. All curves must be transected by the plumb line to
remain gravity baJanced. A is physiologic; B, increased angle; and C, decreased sacral
angle with flattened lumbar lordosis
FICURE 13. Physiologic lumbosacral angle. The lumbosacral angle (LSA) is computed
as the angle from a base paraJlel to horizontal and the hypotenuse drawn parallel to
superior level of the sacral bone. The optimum physiologic lumbosacral is in the vicinity
of 30 degrees
sacral base, permits a more erect lumbar spine with a smaller arc, L.
lordosis. This movement of the pelvis is called tilting" and the effect on
the I umbar lordosis termed flattening.
As the pelvic angle determines the angle of lumbar take-off and
influences the degree oflumbar curvature so must the degree oflumbar
lordosis influence the degree of the superincumbent thoracic curve.
The return to midline to prevent eccentric loading will always force a
flexible vertical balanced rod to curve back toward the midline. As
there is inSignificant anterior-posterior flexion-extension mobility of
the thoracic spine, balance occurs as a rigid total segment moving at the
thoracolumbar joint to maintain its equilibrium (T,,-L,). At the summit,
the balance of the remaining spine is achieved in the cervical region
which balances the head and keeps it at the center of gravity.
The lumbar spine is balanced upon the oblique screen (lumbosacral
angle) (Fig. 13), forming the lordotic curve to regain its balance over the
center of gravity. The curve is so destined because of the shape of the
lordosis. This movement of the pelvis is called tilting" and the effect on
the I umbar lordosis termed flattening.
As the pelvic angle determines the angle of lumbar take-off and
influences the degree oflumbar curvature so must the degree oflumbar
lordosis influence the degree of the superincumbent thoracic curve.
The return to midline to prevent eccentric loading will always force a
flexible vertical balanced rod to curve back toward the midline. As
there is inSignificant anterior-posterior flexion-extension mobility of
the thoracic spine, balance occurs as a rigid total segment moving at the
thoracolumbar joint to maintain its equilibrium (T,,-L,). At the summit,
the balance of the remaining spine is achieved in the cervical region
which balances the head and keeps it at the center of gravity.
The lumbar spine is balanced upon the oblique screen (lumbosacral
angle) (Fig. 13), forming the lordotic curve to regain its balance over the
center of gravity. The curve is so destined because of the shape of the
vertebral discs (insert
disc (Fig. 14), but there is a shearing stress upon the lower lumbar
vertebrae
Because of the short spinous processes of the functional units, the
supraspinous ligament essentially passes behind the tips of the
posterior-superior spine process. The ligamentous attachments of L,
and L, minimize the forward shearing of these vertebrae (Fig. 15
As the ligaments remain relatively relaxed in the full erect posture
FICURE 15. Shear stress. The lordosis
of the lumbar spine causes the vertebrae
to have an incline plane shear
force (lorge orrows). The ligaments
(smoll arrows) attach to the posterior
spinous ligaments which minimize
shearing
the facets must assume a relationship that assists in minimizing shearing
Although the facets are not considered to "bear weight," this
implies direct vertical weight-bearing, but tangential shear is borne by
(the facets (Fig. 16
The three physiologic curves that comprise the static spine and
designate posture are unequivocally influenced by the sacral angle. In
other words, pelvic rotation is the mainstay of erect posture. Lateral
viewing of the three curves of the nonmoving erect spine gives a true
picture of the posture of the erect adult.
While one quarter of the adult spine is composed of disc material, the
remaining three quarters consists of bony vertebrae. As the upper and
lower vertebral cartilaginous plates are essentially parallel, the degree
of curving is largely determined by the shape of the discs. If all the
vertebrae were superimposed on each other without the interposition
FICURE 16. Shear stress on facets. Forward and downward shear of the fifth lumbar
vertebra upon the sacrum is borne by the facet (arrow,) when the longitudinal ligaments
are lax
of the intervertebral discs, the physiologic postural curves would not
exist. The discless spine would fonn a very slight curve with its convexity
posterior. The curve formed by the discless spine would resemble
that of the newborn child. Development of the upright adult posture
evolves in a chronological pattern from the first posture of the
newborn
The spine of the newborn has none of the adult physiologic curves
but instead has a total flexion curve of the curled-up infant in utero. The
total curve is slightly more arched than is the ultimate adult thoracic
kyphotic curve, and the curve is of similar convexity. There are no
lordotic curves in the lumbar or cervical spinal areas of the newborn
child.
During the first 6 to 8 weeks of life, the child raises his head and by
this antigravity maneuver initiates the muscular action of the erector
muscles that form the cervical lordosis. As crawling and sitting ultimately
evolve, the lower lumbar spinal curve develops in an antigravity
FICURE 17. Chronologie development of posture.A. The total curve of the fetal spine in
utero. B. Fonnation of the cerivcaJ lordosis when the head overcomes gravity.C. Fonnation
of the second lordotic (lumbar) curve due to the antigravity force of the lumbar
erector spinae (ES) muscles and the restriction of the iliopsoas muscles (IP). D. Erect
adult posture showing the strong antigravity erector muscles (ES and HE hip extensors)
and the weak nexor (F) muscles of the neck and abdomen
action. The dorsal kyphosis has no antigravity influence even when an
erect posture is reached, so that the change that evolves is merely a
slight increase in its initial in utero convexity
The addition of the two lordotic curves gives primarily the antigravity
effect of the erector muscles which develop in the child as it
attempts and finally achieves the upright-erect position. The lordotic
curves originate partly from the original strength of the antigravity
muscle and in some measure from the weakness of the opposite musculature
such as that which exists in the abdominal muscle and in the
anterior neck-flexor muscles
The lumbar lordosis is caused largely by the failure of the hip flexors
to stretch and elongate. In the fetal position the hips and knees are
,,flexed against the abdomen of the child in its "curled up in a ball
position. As the legs extend, the iliopsoas muscle elongates slowly but
incompletely. The iliacus because of its influence upon the inner
aspect of the ilium to the anterior-upper thigh acts to keep the hips
flexed. The psoas originates from the anterior aspect of the lumbar
