Where Exactly Does Back Pain Come From?

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.”

In Support Of Dr. Mooney’s Perspective, Four Such Studies Are Reviewed Here:

In 1985, Dr. Kirkaldy-Willis, a Professor Emeritus of Orthopedics and director of the Low-Back Pain Clinic at the University Hospital, Saskatoon, Canada, published an article in the journal Canadian Family Physician (9).

In this study, the authors present the results of a prospective observational study of spinal manipulation in 283 patients with chronic low back and leg pain.

All 283 patients in this study had failed prior conservative and/or operative treatment, and they were all totally disabled. These patients were given a “two or three week regimen of daily spinal manipulations by an experienced chiropractor.”

These authors determined a good result from manipulation to be:

“Symptom-free with no restrictions for work or other activities.”

OR

“Mild intermittent pain with no restrictions for work or other activities.”

81% of the patients with referred pain syndromes subsequent to joint dysfunctions achieved the “good” result.

48% of the patients with nerve compression syndromes, primarily subsequent to disc lesions and/or central canal spinal stenosis, achieved the “good” result.

Dr. Kirkaldy-Willis attributed this clinical outcome to Melzack and Wall’s 1965 “Gate Theory of Pain.” He noted that the manipulation improved motion, which improved proprioceptive neurological input into the central nervous system, which in turn blocked pain.

Dr. Kirkaldy-Willis’ conclusion from the study was:

“The physician who makes use of this [manipulation] resource will provide relief for many back pain patients.”

In 1990, Dr. TW Meade published the results of a randomized comparison of chiropractic and hospital outpatient treatment in the treatment of low back pain. This trial involved 741 patients and was published in the prestigious British Medical Journal (10). It was titled:

Low back pain of mechanical origin:
Randomized comparison of chiropractic and hospital outpatient treatment

The patients in this studied were followed for a period between 1 – 3 years. Nearly all of the chiropractic management involved traditional joint manipulation. Key points presented in this article include:

“Chiropractic treatment was more effective than hospital outpatient management, mainly for patients with chronic or severe back pain.”

“There is, therefore, economic support for use of chiropractic in low back pain, though the obvious clinical improvement in pain and disability attributable to chiropractic treatment is in itself an adequate reason for considering the use of chiropractic.”

“Chiropractic was particularly effective in those with fairly intractable pain-that is, those with a history of severe pain.”

“Patients treated by chiropractors were not only no worse off than those treated in hospital but almost certainly fared considerably better and that they maintained their improvement for at least two years.”

“The results leave little doubt that chiropractic is more effective than conventional hospital outpatient treatment.”

Most importantly, the above studies indicate that the primary tissue origin of chronic back pain is the intervertebral disc.

This study by Meade notes that the benefit of chiropractic is seen primarily in patients that are suffering from severe chronic pain.

This would suggest that chiropractic manipulation is affecting the pain afferents arising from the disc. A plausible theory to support this is found below… at the end of this presentation.

Also, the Meade study authors definitively note that if all back pain patients without manipulation contraindications were referred for chiropractic instead of hospital treatment, there would be significant annual treatment cost reductions, a significant reduction in sickness days during the following two years, and a significant savings in social security payments.

In 2003, the highly regarded orthopedic journal SPINE published a randomized clinical trial involving the nonsteroidal anti-inflammatory cox-2 inhibiting drugs Vioxx or Celebrex v. needle acupuncture v. chiropractic manipulation in the treatment of chronic neck and back pain (11). The title of the article is: Chronic Spinal Pain: A Randomized Clinical Trial Comparing Medication, Acupuncture, and Spinal Manipulation

In this study chiropractic was over 5 times more effective than the medications and better than twice as effective as needle acupuncture in the treatment of chronic spine pain.

Chiropractic was able to accomplish these clinical outcomes without any reported adverse effects.

One year after the completion of this 9-week clinical trial, 90% of the original trial participants were re-evaluated to assess their clinical status.

The authors discovered that only those who received chiropractic during the initial randomization benefited from a long-term stable clinical outcome. The results of this second assessment were published in 2005 (12).

An important question to consider…

How does joint manipulation reduce chronic back pain arising from the intervertebral disc?

I find that the most plausible explanation is offered by Canadian orthopedic surgeon WH Kirkaldy-Willis in the first edition (1983) of his book titled Managing Low Back Pain.

Dr. Kirkaldy-Willis describes the biomechanics of how the two facet joints form a three-joint complex with the intervertebral disc.

He notes that “motion at one site must reflect motion at the other two.” It is probable that spinal manipulation primarily mechanically affects the facet articulations.

According to Dr. Kirkaldy-Willis, such facet motion would necessarily cause motion in the intervertebral disc. Consistent with the published data noted above, this would improve fluid mechanics of the disc, disperse the accumulation of inflammatory exudates, and initiate a neurological sequence of events that would “close the pain gait.”

In the final conclusion, the outcomes of the clinical trials noted speak for themselves.

References

1) Nachemson, AL, Spine, Volume 1, Number 1, March 1976, pp. 59-71.

2) Smyth MJ, Wright V, Sciatica and the intervertebral disc. An experimental study. Journal of Bone and Joint Surgery [American];40: 1548, pp. 1401-1408.

3) Jayson M, Editor; The Lumbar Spine and back Pain, Third Edition, Churchill Livingstone, 1987, p. 60.

4) Bogduk N, Tynan W, Wilson A. S., The nerve supply to the human lumbar

intervertebral discs, Journal of Anatomy. (1981, 132, 1, pp. 39-56.

5) Bogduk N., The innervation of the lumbar spine. Spine. April 1983;8(3): pp. 286-93.

6) Mooney, V, Where Is the Pain Coming From? Spine, 12(8), 1987, pp. 754-759.

7) Kuslich S, Ulstrom C, Michael C; 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; Orthopedic Clinics of North America, Vol. 22, No. 2, April 1991, pp.181-7

8) Ozawa, Tomoyuki MD; Ohtori, Seiji MD; Inoue, Gen MD; Aoki, Yasuchika MD; Moriya, Hideshige MD; Takahashi, Kazuhisa MD; The Degenerated Lumbar Intervertebral Disc is Innervated Primarily by Peptide-Containing Sensory Nerve Fibers in Humans; Spine, Volume 31(21), October 1, 2006, pp. 2418-2422.

9) Kirkaldy-Willis WH, Cassidy JD; Spinal Manipulation in the Treatment of Low Back Pain; Canadian Family Physician, March 1985, Vol. 31, pp. 535-540

10) Meade TW, Dyer S, Browne W, Townsend J, Frank OA; Low back pain of mechanical origin: Randomized comparison of chiropractic and hospital outpatient treatment; British Medical Journal; Volume 300, June 2, 1990, pp. 1431-7.

11) Giles LGF, Muller R; Chronic Spinal Pain: A Randomized Clinical Trial Comparing Medication, Acupuncture, and Spinal Manipulation; Spine, July 15, 2003; 28(14):1490-1502.

12) Muller R, Lynton G.F. Giles LGF, DC, PhD; Long-Term Follow-up of a Randomized Clinical Trial Assessing the Efficacy of Medication, Acupuncture, and Spinal Manipulation for Chronic Mechanical Spinal Pain Syndromes; Journal of Manipulative and Physiological Therapeutics, January 2005, Volume 28, No. 1.

13) Kirkaldy-Willis WH, Managing Low Back Pain, Churchill Livingstone, 1983, p. 19.

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