Experimental intervertebral-disc lesions produced by injection of various chmeical solutions
For centuries, the problem of low-back pain and sciatica has often been an enigma
to the medical profession. although much excellent work has been done on the
subject of backache, there is much left to be answered. An imposing list of
possible causes for this syndrome has been compiled which implicates various
structures and tissues in the pelvic and abdominal regions, however, convincing
pathological and anatomical evidence to incriminate these various structures is
frequently not to be found in patients who complain of low-back and sciatic pain.
Since the demonstration of Mixter and Barr, rupture of an intervertebral disc or
posterior protrusion of an intervertebral disc has been recognized as a clinical as
well as pathological entity and there has been a growing tendency among clinicians
to attribute low-back pain to derangements of the lumbar intervertebral discs in
the absence of other demonstrable causes. Furthermore, there are many who believe
that the lesions of an intervertebral disc are the only cause of idiopathic
low-back pain with or without sciatica. However, in many instances, we are not only
at a loss for an explanation of mechanism by which pain is produced but also
difficult to demonstrate the exact pathogenesis how the derangements of an
intervertebral disc is brought about.
This particular problem received a great deal of attention by many workers who
put forth many theories and arguments concerning degeneration of an intervertebral
disc and its relation to backache. Among the evidences, a trauma or physical
factors impinging upon an intervertebral disc has been considered to be playing a
major role in producing such lesions.
Quite frequently a practice of modern medicine requires a lumbar puncture for
diagnostic, anesthetic or therapeutic purposes. Particularly the use of lumbar
puncture in the investigation of lesions of the central nervous system has become
so standarized that it is almost as much of a routine procedure as the systematic
study of the reflexes.
The possibilities of serious damage to an intervertebral disc by needle puncture
are evident from the reports of many observers. Furthermore, over-enthusiasm is
leading some surgeons to deliberate insertion of a needle through the disc for the
purpose of injecting radio-opaque material for diagnostic purpose. Much concern has
been expressed by some who warned the possible deleterious effects of such
While this particular problem has been a concern to many clinicians and
8investigators in this field, we know of no work previously done dealing with this
specific problem. Therefore a following experiment is planned to investigate the
effects of injecting various chemical solutions directly into the intervertebral
discs and clarify some aspects of disc degeneration.
Materials and Methods:
Fourty healthy mongrel dogs of various breeds were utilized. Each animals was
subjected to simple X-ray visualization of spinal column and myelography to check
the abnormalities of spine before experimental procedures. The chemical solutions
selected were Pantopaque, Diodrast, Procaine hydrochloride and Normal Saline which
are commonly used in the practice for the purposes of myelography, discography,
subarachnoidal block or other diagnostic procedures.
The animals were divided into five groups, namely pantopaque group, diodrast
group, procaine group, saline group and multiple puncture group.
Under pentothal sodim anesthesia, pararectal incision was made to visualize the
lumbar intervertebral discs trans-peritoneally. Under direct observation of an
individual disc, 0.2 to 0.4 c.c. of designated solutions were injected through 21
gauge needle. Each animal received injections into 4 intervertebral discs. The
multiple punctures were made with 21 gauge needle for 10 to 15 times into the disc.
Following injection of pantopaque and diodrast each animal was X-rayed to confirm
the correct insertion of dyes into the disc.
After operative procedures, the animals were sacrificed in the intervals of 24
hours, 72 hours, 1 week, 2 weeks, 3 weeks and 4 weeks respectively. Individual disc
was separated from the vertebral column, the gross features carefully recorded and
photographed and fixed into 10% neutral formalin. Paraffin section were stained
with Hematoxylin and Eosin, Periodic Acid Schiff reaction, Toluidine blue and
Mallory's Azan Stains.
As compared with the control discs, the experimental discs all showed one or more
of pathological changes as shown in the tables and figures. The most devastating
damage had occurred in the annulus fibrosus and nucleus pulposus.
Macroscopically, the cartilage plates showed little or no alterations except for
some fragmentation and hemorrhage in the multiple puncture group. The changes in
the annulus fibrosus were more marked in the multiple puncture group and less
marked in the diodrast and pantopaque groups, these changes were characterized by
irregularity of running fibers of annulus resulting in disorganized pattern at the
boundaries with the nucleus pulposus. The surfaces often showed irregular ups and
downs. The nucleus pulposus of the multiple puncture group showed hemorrhage,
fragmentation and irregular bulging of structures. In some discs, the entire
nuclear material was lost at the time of examination. The nucleus pulposus of
saline injected discs showed irregular shrinkage and fragmentation. The procaine
injected discs showed somewhat transparant appearance of discs and discoloration of
surface appearance. The diodrast injected discs showed cloudy discoloration.
Brownish surface with hemorrhagic spots were often present but these changes
gradually disappeared as the time lapsed. The pantopaque group showed little
changes in the gross appearance of nucleus but considerably the nuclear materials
Microscopically, the majority of the experimental discs showed inflammatory
reactions centered around the sites of needle punctures. The inflammatory reaction
occurred quite early and became fibrotic very soon but the fibroblastic reaction
was mainly localized on the surface and the inner portions of annulus remained
broken for a long time. Oftentimes, small blood vessels invaded into the bundles of
annulus. Fragmentation and radial splitting of the annulus together with mucinous
swelling and degeneration was very common, Vacuolization of annulus was also
Oftentimes, particularly in the multiple puncture group, the nuclear materials
herniated through the openings created by broken annulys. the herniated materials
formed swollen pockets surrounded by fibrosis and healed inflammatory reaction.
The nucleus pulposus of saline injected group showed extreme shrinkage of
cytoplasm of notochordal cells with loss of much of them. The procaine injected
group showed more of ground substance which were stained heavily with P.A.S. and
Toluidine blue stains. The cells in this group showed shrinkage of cytoplasm but
also contained scattered swollen physalipherous cells. The diodrast group showed
more changes in the annulus and cartilage plates and created herniation of nuclear
material. The nucleus pulposus showed loss of cells, and irregular fragmentation of
The pantopaque group showed similar changes with that ween in diodrast group but
the cellular degeneration was quite more apparent. Hemorrhage, inflammation and
fragmentation of nuclear material were the common findings in the multiple puncture
The cartilage plates remained relatively intact in all the experimental discs
however in some, cystic degeneration and calcification was noted.
Comment and Conclusion:
From the data obtained above, it is quite apparent that injection of various
chemical solutions into an intervertebral disc causes a significant pathological
alterations. The fact that simple multiple puncture and injection of normal saline
has also caused serious damage to an intervertebral disc should be seriously taken
as a clear warning toward the abuse of inadequate lumbar punctures.
In many aspects, the morphological changes seen in the present investigation were
quite similar to the changes seen in so-called degenerated discs. Although there
were some minor differences between the chemicals utilized, the changes appeared to
be of similar nature and severity. The multiple puncture of an intervertebral disc
created, however, the most devastating damage among the groups.
Intervertebral disc is not just a static anatomical structure but is a dynamic
structure constantly functioning. From the earliest investigations, it has been
said that the efficient functioning of the disc depends largely on the elasticity
of the nucleus pulposus and that this in turn is closely related to its
water-binding capacity. It is also known that in early life a water content of
80∼88% is usually quoted and in later life figures of 70% may occur.
This change is usually accompanied by an alteration of morphology of the nucleus.
The changes in the water-binding capacity have been thought to be related to the
biochemical alterations occurring in the degenerated disc. The delicate mechanism
of water balance can be upset by eve minute tears in the annulus or the plates if
one assumes that the disc is an osmotic system.
There are others who claim that the imbibition pressure and not the osmotic
pressure is responsible for the hydration of nucleus pulposus. In any event,
however, the derangement of this water-binding mechanism caused by introduction of
chemical solutions might have caused such a degenerative changes observed in this
It appeared that the interaction between the nucleus and the chemical substances
were only related to the physical factors and not to the chemical interaction.
It is convincingly proven that direct trauma to an intervertebral disc by needle
puncture can cause serious damage to the disc and that injection of radio-opaque
materials into the disc may also bring serious consequences.