lumbar pelvic rhythm

lower Back pain  syndrome

lumbar-pelvic rhythm

                    

FIGURE 35. Lumbar pelvic rhythm. With pelvis fixed, flexion-extension of the lumbar

.spine occurs mostly in the lower segments L4-5 and L3-S 1 



LUMBAR-PELVIC RHYTHM

The lumbar-pelvic rhythm (Fig. 35) can be perceived as the ratio

between two movements occurring simultaneously in one plane. Reversal

of the lumbar curve is difficult to grade in a numerical formula

that would be simple, clear, and concise. The lumbar portion of the

rhythm is initially a flattening, then a gradual reversal of an arc that was

not originally a perfect sphere. The lumbar curve does not reverse

equally at all points along its sphere. The difference of movement at the

L3-S1 segment compared to the movement between L2-L3 indicates the

irregularity of the arc as it flattens out and reverses. Nevertheless, there

is significant smoothness of curve change to correlate it in a smooth

kinetic relationship with a simultaneous secondary movement of pelvic

.rotation

,During the change of lumbar curve from concave to flat, to convex

occurs the secondary movement of pelvic rotation. The pelvic phase of

the rhythm is merely the rotation of the pelvis around the transverse

axis of the two hip joints. Pelvic rotation, in total spinal flexion, is

rotation of the pelvis starting with the sacral angle as noted in the static

spine, fol lowed by a smooth gradual increase of the angle as the anterior

portion of the pelvis descends and the posterior aspect ascends. The

sacral angle which increases in flexion decreases in extension as the

body returns to the erect static stance. The grading of this rotation is

easy to calibrate mathematically as the movement consists merely of

.rotation around a central point

                   

Lumbar-pelvic rhythm is a simultaneous movement in a rhythmic

ratio of a lumbar movement to a pelvic rotation, the sum-total-movement

consisting in the person's bending forward and returning to an

erect position. At any phase of total body flexion the extent of lumbar

curve flattening must be accompanied by a proportionate degree of

pelvic rotation. When complete body flexion has been attained, the

lumbar curve must have fully straightened and reversed, thus presenting

a lumbar convexity while the pelvis must have rotated to the full

extent permitted by the hip joints. The rhythm is so smooth and precise

that at every point in the process there will be equality between

lumbar reversal and pelvic rotation.

In forward flexion most of the spinal flexion occurs by the time the

trunk is inclined 45 degrees forward. The remainder of forward flexion

occurs as a rotation of the pelvis. In resuming the erect posture the

.opposite movement occurs

,The lumbar disc, being of equal thickness anteriorly and pos-teriorly

allows as much flexion as extension from the position of rest, except that

in the lower lumbar region the disc is thicker anteriorly than posteriorl

thus allowing less flexion than extension.

In forward flexion the lumbar joints flex as the extensor muscles

lower the body weight above the lowest lumbar joint. By 45 degrees of

flexion, the tension in the ligaments has increased and that in the

muscles decreased7-10  (Fig. 36). Further flexion occurs as a rotation of

the pelvis by relaxation of the posterior leg and hip muscles when the

.pelvis relaxes

,(In lifting a heavy object (or the reverse, in lowering a heavy object

the pelvis at first rotates with the ligaments of the lumbar spine bearing

the brunt of the stress until 45 degrees of flexion is reached, at which

(point the muscles of the back become active (Fig. 37
One of the mechanical advantages of flexing the hips and knees is

that it places the hip extensors at a mechanical advantage. Another

advantage is that the quadriceps femoris group assists in the lifting and

simultaneously tenses the iliotibial band which is the site of attachment

of the glutei. By flexing the hips and knees, the distance between the

weight being lifted and the center of gravity is decreased" (Fig. 38). As

the spine flexes, the shoulder girdle and the pelvis (hip joint) comes

.(closer together, which decreases the lever arm for lifting (Fig. 39

In the discussion of the lumbar-pelvic rhythm the emphasis has been

on fleXion, but the exact converse of the thythm must occur in the

return to erect position after flexion. It is obvious that return from any

point must begin at a concise point in the rhythm at some place during

the descent. Just as every point in the lumbar flexion must be matched

by a concise point in the degree of pelvic rotational tilting so must

return to the erect be synchronously perfect. Full return to uprigbt

FICURE 36. Muscular deceleration and accelemtion of the forward-flexing spine from
the erect ligamentous support to the fully flexed ligamentous restriction. Muscle eccentric
.and concentric contraction pennits forward flexion and re-extension


finds the pelvis derotated to its more acute lumbosacral angle while the
.(lumbar curve resumes its erect static lordosis (Fig. 36 in reverse
Man in his action of bending forward and straightening up must
,conform to accurate smooth lumbar-pelvic rhythm which, being kinetic
is a neuromuscular pattern of action as well as a mechanical
function. This neuromuscular pattern is partly acquired and partly
inherited. Deviation, however, can occur, and faulty habit can be
learned and repeated until the deviation becomes a deep-seated habit
pattern. Proper rhythm similarly can be perfected by learning and
acquired habits












(FICURE 37. Muscle-ligamentous control in lifting. In lifting from full flexed (90 de-grees
to half erect (45 degrees), the lumbar spine is supported by its ligaments (L) with
posterior pelvic muscles (M) bearing the stress effort. From 45 degrees of flexion to full
.erect the spine extensor muscles contract and complete the full extension



The neuromuscular pattern must be precise and work together with
faultless mechanical action of the spine. All the moving parts must be
unimpeded. As any defective part in an otherwise integrated machine
will impair total function so will inadequacy of any of the component
.parts of the lumbar-pelvic mechanism destroy proper rhythm
Reference to component parts again draws attention to the functional
unit. Adequacy of the unit demands competent discs. Anatomically
symmetrical facets are necessary to permit accurate gliding. and the
synovial linings of the articular surfaces must present no impediment to
.smooth motion
The longitudinal ligaments the main function of which is limitation
of motion must in tum permit sufficient and free movement existing

throughout the length of the ligament. Segmental limitation in the







FIGURE 38. Pelvic extensor mechanism. By flexing the knees, the quadriceps tense the
iliotibial band to which is attached the glutei. This combination strengthens the pelvic
rotation which extends the back in lining


elongation of any one ligament would cause excessive movement in the
other less restricted segments. Limited elongation of the entire length
of the longitudinal ligament would totally impair the lumbar phase of
the rhythm. Physiologic spine flexion requires resiliency for the posterior
longitudinal ligament while the paraspinous muscles must have
.equal elasticity
Pelvic rotation is directly dependent on the adequacy of the hipjoints
to rotate fully in a ball-bearing manner. This requires a normal hip-joint
socket working bilaterally. The intactness of the joint socket must be

FICURE 39. Mechanica1 advantage in

lifting an object close to the body from

45 degrees to cred. The erector spinae

muscles extend the spine upon the pel·

vis and " do the lifting." The shorter the

distance of the weight (Dx ) to the

center of gravity (CG), the more efficient

is the lever ann. The pelvis is rotated

by the glutei (C), which arc aided

by the quadriceps and tensor band

                                                                                               
             

accompanied by resilient periarticular tissues and good muscular control

of hip function. The third phase of the lumbar-pelvic rhythm in

which the pelvic joint alters its relationship to the center of gravity also

demands symmetrical integrity of the hip joints