In this month’s edition, we’re going to discuss some “intrigue” that has plagued low back treatments—both conservative and aggressive—for many years now.
The intrigue being “WHERE” exactly does the pain generate from? What structure? What neurological mechanism? And with some detective work I think we’ve uncovered some significant findings.
The modern era in the understanding of low back pain that we’re in right now began in 1976 when internationally respected orthopedic surgeon Alf Nachemson published his detailed review (136 references) in the new journal SPINE (1), entitled “The Lumbar Spine: An Orthopaedic Challenge“.
In this article, Dr. Nachemson notes that a staggaring 80% of us will experience low back pain at some time in our life. He further notes that:
“The Intervertebral Disc Is Most Likely The Cause Of The Pain…”
Dr. Nachemson makes a VERY convincing case when he presents 6 lines of reasoning, supported by 17 references, to support his contention that the intervertebral disc is the most likely source of back pain, including the primary research completed by Smyth and Wright in 1958 (2). Regarding the work by Smyth and Wright, Dr. Nachemson notes:
“Investigations have been performed in which thin nylon threads were surgically fastened to various structures and around the nerve root. Three to four weeks after surgery these structures were irritated by pulling on the threads, but pain resembling that which the patient had experienced previously could only be registered only from the outer part of the annulus” of the disc.
It had been established in the 1930s that herniation of the lumbar disc could put pressure on the nerve root or the cauda equina, resulting in sciatica. However, Dr. Nachemson in this context is saying something dramatically different;
He’s Claiming That A Non-Herniated Disc Problem Was Causing Back Pain.
At the time (1976), claiming the intervertebral disc was capable of initiating pain was new and not only that, Nachemson claiming the disc to be the most probable source of back pain was both surprising AND revolutionary.
At the time, most authoritative reference texts stated the intervertebral disc was not even innervated with pain afferents and therefore not capable of initiating pain.
As an example, rheumatology professor Malcolm Jayson, MD (editor) in the 1987 text titled The Lumbar Spine and Back Pain, states
“in the mature human spine no nerve endings of any description remain in the nucleus pulposus or annulus fibrosis of the intervertebral disc in any region of the vertebral column.” (3)
A conclusion we now know to be 100% false.
Support for Dr. Nachemson’s contention of disc pain came in 1981 when anatomist and physician Nikoli Bogduk published an extensive review of the literature on the topic of disc innervation, along with his own primary research, in the prestigious Journal of Anatomy (4). Dr. Bogduk notes:
“In the absence of any comprehensive description of the innervation of the lumbar intervertebral discs and their related longitudinal ligaments, the present study was undertaken to establish in detail the source and pattern of innervation of these structures.”
Dr. Bogduk and his team concluded decisively:
“The Lumbar Intervertebral Discs Are Supplied By A Variety Of Nerves.”
and “Clinically, The Concept Of ‘Disc Pain’ Is Now Well Accepted.”
Dr. Bogduk returned in 1983 updating his research notes in SPINE, stating more specifically :
“THE LUMBAR INTERVERTEBRAL DISCS ARE INNERVATED
posteriorly by the sinuvertebral nerves, but laterally by
branches of the ventral rami and grey rami communicantes…
The posterior longitudinal ligament is innervated by the sinuvertebral nerves and the anterior longitudinal ligament by branches of the grey rami.
Lateral and intermediate branches of the lumbar dorsal rami supply the iliocostalis lumborum and longissimus thoracis, respectively.
Medial branches supply the multifidus, intertransversarii mediales, interspinales, interspinous ligament, and the lumbar zygapophysial joints.”
“The distribution of the intrinsic nerves of the lumbar vertebral column
systematically identifies those structures that are
potential sources of primary low-back pain.”
Adding to the growing momentum of this “disc-pain” concept… In 1987, SPINE published Dr. Vert Mooney’s Presidential Address of the International Society for the Study of the Lumbar Spine. It was delivered at the 13th Annual Meeting of the International Society for the Study of the Lumbar Spine, May 29-June 2, 1986, Dallas, Texas, and titled (6):
Where Is the Pain Coming From?
In this article, Dr. Mooney notes the following:
“Six weeks to 2 months is usually enough to heal any
stretched ligament, muscle tendon, or joint capsule.
Yet we know that 10% of back ‘injuries’ do not resolve
in 2 months and that they do become chronic.”
“Anatomically the motion segment of the back is made up of two synovial joints and a unique relatively avascular tissue found nowhere else in the body – the intervertebral disc. Is it possible for the disc to obey different rules of damage than the rest of the connective tissue of the musculoskeletal system?”
“Persistent pain in the back with referred pain to the leg
is largely on the basis of abnormalities within the disc.”
Chemistry of the disc is based on the relationship between
mucopolysaccharide production and water content.
“Mechanical events can be translated into chemical events related to pain.”
An important aspect of disc nutrition and health is the
mechanical aspects of the disc related to the fluid mechanics.
“Mechanical activity has a great deal to do with the
exchange of water and oxygen concentration” in the disc.
The pumping action maintains the nutrition and biomechanical function of the intervertebral disc. Thus, “research substantiates the view that unchanging posture, as a result of constant pressure such as standing, sitting or lying, leads to an interruption of pressure-dependent transfer of liquid. Actually the human intervertebral disc lives because of movement.”
“The fluid content of the disc can be changed by mechanical activity, and the fluid content is largely bound to the proteoglycans, especially of the nucleus.”
“In summary, what is the answer to the question of where is the pain coming from in the chronic low-back pain patient? I believe its source, ultimately, is in the disc. Basic studies and clinical experience suggest that mechanical therapy is the most rational approach to relief of this painful condition.”
“Prolonged rest and passive physical therapy modalities no longer have a place in the treatment of the chronic problem.”
This model presented by Dr. Mooney in this paper goes on to discuss:
The intervertebral disc as the primary source of both back pain and referred leg pain. The disc apparently becomes painful because of altered biochemistry, which sensitizes the pain afferents that innervate it.
Disc biochemistry is altered because of mechanical problems, especially mechanical problems that reduce disc movement.
Therefore, the most rational approach to the treatment of chronic low back pain is mechanical therapy that restores the motion to the joints of the spine, especially to the disc.
Prolonged Rest Is Inappropriate Management
Additional support for the disc being the primary source of back pain was presented by Dr. Stephen Kuslich in the prestigious journal Orthopedic Clinics of North America in April 1991 (7). The title of his article is:
The Tissue Origin of Low Back Pain and Sciatica:
A Report of Pain Response to Tissue Stimulation During Operations
on the Lumbar Spine Using Local Anesthesia
These authors performed 700 lumbar spine operations using only local anesthesia to determine the tissue origin of low back and leg pain, and they present the results on 193 consecutive patients studied prospectively. Several of their critically important findings for you include:
“Back pain could be produced by several lumbar tissues, but by far, the most common tissue or origin was the outer layer of the annulus fibrosis.”
The lumbar fascia could be “touched or even cut without anesthesia.”
Any pain derived from muscle pressure was “derived from local vessels and nerves, rather than the muscle bundles themselves.”
“The normal, uncompressed, or unstretched nerve root was completely insensitive to pain.”
“In spite of all that has been written about muscles, fascia, and bone as a source of pain, these tissues are really quite insensitive.”
In summary, these authors found that…
The Outer Annulus Is “THE SITE” Of A Patient’s Back Pain.
Past studies that suggest the disc is not an important source of low back pain because nerve endings “are not present” are clearly and overwhelmingly erroneous when you carefully analyzed the most modern literature.
Documented research at no time has demonstrated irritation of a normal or inflamed nerve root to produce low back pain. Back muscles themselves are proven not to be a source of back pain; in fact, the muscles, fascia, and bone are really quite insensitive for pain. The inflamed, stretched, or compressed nerve root is in fact the cause of buttock, leg pain and sciatica, but not back pain.
Very recently in 2006, physician researchers from Japan published in SPINE the results of an extremely sophisticated immunohistochemistry study of the sensory innervation of the human lumbar intervertebral disc (8). The article is titled:The Degenerated Lumbar Intervertebral Disc is Innervated Primarily by Peptide-Containing Sensory Nerve Fibers in Humans
The Japanese researchers note:
“Many investigators have reported the existence of sensory nerve fibers in the intervertebral discs of animals and humans, suggesting that the intervertebral disc can be a source of low back pain.”
“Both inner and outer layers of the degenerated lumbar intervertebral disc are innervated by pain sensory nerve fibers in humans.”
Pain neuron fibers are found in all human discs that have been removed because they are the source of a patient’s chronic low back pain.
The nerve fibers in the disc, found in this study, “indicates that the disc can be a source of pain sensation.”
The information and data offered by these studies from across 30 years of published research in the most highly respected journals CLEARLY and UNEQUIVOCALLY demonstrates that…
The Annulus Of The Intervertebral Disc Is Primarily Responsible For The Majority Of Chronic Low Back Pain.
Above (6), Dr Vert Mooney notes in his Presidential Address to the International Society for the Study of the Lumbar Spine that, “basic studies and clinical experience suggest that mechanical therapy is the most rational approach to relief of this painful [intervertebral disc] condition.”