Lower Back pain


tissue sites of pain origin

lower Back pain syndrome

tissue sites of pain origin


The intervertebral disc itself is a non-pain-sensitive tissue. The total
disc is an inert tissue and the nucleus has been found completely free of
any sensory type of nerve endings. Nerve endings have been found in
the annulus, but neurophysiologic studies have failed to discover pain
sensory transmission from these nerves. The discs, therefore, both
annulus and nucleus, must be considered insensitive to pain sensations,
If the absence of sensory nerves emanating from the disc be accepted
it must be assumed that it is not possible to consider the disc a painproducing
unit. The commonplace disc-pain must, therefore, originate
from contiguous tissues, with the disc itself in some manner participating
in the instigation of disc-pain by its action on these surrounding
-If the internal pressure within a normal disc is experimentally in

FIGURE 20. Pain-sensitive tissues of the functional unit. The tissues labeled + are
pain-sensitive in that they contain sensory nerve endings that are capable of causing pain
when irritated. Tissues labeled - are devoid of sensory nerve endings

(IVF= intervertebral foramen containing nerve root (NR
LF = ligamentum navum
PLL = posterior longitudinal ligament
ALL = anterior longitudinal ligament
IVD = annulus fibrosus of intervertebral disc
FA = facet articular cartilage
ISL= interspinous ligamen

creased by injecting saline solution into the disc the mere increase of
such pressure does not cause pain. In a disc, however, that has previously
been degenerated, which degeneration can be considered fragmentation
of the annulus with a dehydrated nucleus, increase in the
interdiscal pressure causes an ache in the region of the low back.'
If the same method of increasing pressure within a disc of known
degeneration is used no pain sensation occurs when the posterior
longitudinal ligament is anesthetized by procaine. It can be assumed
then that the irritation of the posterior longitudinal ligament by increase
in internal pressure within a degenerated disc is the mechanism

of pain production, and the posterior longitudinal ligament is the painsensitive
tissue. The posterior longitudinal ligament therefore must
contain sensory nerve endings
It is apparent that a normal disc has sufficient elasticity and resiliency
to withstand significant increases in internal pressure which will prevent
a bulging irritation of contiguous tissues. Degeneration of a disc
due to annular fragmentation decreases its resiliency and resistance to
increase in internal pressure, permitting encroachment on surrounding
-The ligamentum flavum and the interspinous ligaments are nonsen
sitive .Similarly, stimulation or movement of the dura mater elicits no
sensation of pain. These tissues, therefore, must be classified as insensitive
to pain
The synovial lining of the facets and the articular capsule of these
joints are richly supplied by sensory as well as vasomotor nerves. The
synovial tissues of these joint spaces respond to stimuli and inflammations
as do all other synovial joint tissues elsewhere in the body.
Inflammatory responses of these tissues result in swelling and engorgement
of the synovial linings, increase viscosity of the synovial
fluid, causing periarticular muscle spasm that results in progressive
limitation of movement. The part becomes "frozen" or at least significantly
immobilized. Inflammation of synovial joints produces dull to
severe pain depending on the severity and extent of the inflammation
The concomitant muscle spasm that accompanies spine dysfunction
is in itself capahle of eliciting pain. In animal experiments, painful
irritation of the lumbosacral joints and ligaments causes reflex spasm of
the erector spinae and hamstring muscles. This spasm in a human being
undoubtedly is painful. In addition to pain resulting from the joint and
ligamentous irritation, there can arise irritation from the sustained
muscle spasm, compression of the interposed intervertebral disc by the
spasm of the muscle, which will result in pain if any disc degeneration
exists. In the presence of any disc degeneration the spasm can constitute
a significant compressive force. Multiple factors, such as these, can
be seen to contribute to the production of pain at the functional unit
Another factor is the sciatic nerve root which emerges through the
intervertebral foramen. It is a combined motor-sensory nerve and thus
is a pain-sensitive nerve. irritation of this nerve evokes pain localized
to the dermatome distribution of the specific rootlet irritated.
Pain elicited from irritation of the nerve root, felt either locally or
distally, is considered as resulting from dural irritation. The dura is
(innervated by the recurrent nerve of Luschka (Fig. 21
As the nerve roots descend the spinal canal, they cross the disc

immediately above the foramen. The roots enter the foramina beneath


FICURE 21. Innervation of the recurrent nerve of Luschka

PPD - posterior primary division
APD - anterior primary division
eeL - sympathetic ganglion
INN - internuncial neurons
VSN - ventral sensory nerve sse - sensory sympathetic ganglion
RN - recurrent nerve of Luschka
D - to dura
PLL - posterior longitudinal ligament

,the pedicle. After they leave the foramina, they incline downward
outward, and forward. In the lower disc levels the nerves enter the
origin of the psoas muscle (Fig. 22). By virtue of their vertical entry into
the foramen, they are located in the superior aspect of that foramen
.(Fig. 23)
At their entry into the foramen on their extravertebral course, they
invaginate the dura and the arachnoid and carry a sheath of each into
the foramen. The arachnoid continues along the nerve root as far as the
ganglion (Fig. 24). The dura continues along the combined nerve (sensory
and motor portion) until it fuses with the arachnoid, forming the
,distal end of the sleeve. The dura then continues along the distal nerve
.forming the outer fibrous sheath of the nerve, the perineureum
-The posterior (sensory) nerve root is twice the thickness of the an


FIGURE 22. Relationship of nerve roots t o vertebral levels

FICURE 24. Dural and arachnoid sheaths of the nerve root complex. The arachnoid
follows the sensory and motor nerve roots to the beginning of the intervertebral foramen
and follows the sensory root to the beginning of the ganglion. The dura follows the nerve
roots until they become the combined sensory and motor nerve outside the foramen and
continues as the perineurium and epineurium. Neither the dura nor the arachnoid
attaches to the intervertebral foramen