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Norwalk, Iowa—In July 2004, a doctor of chiropractic voiced concern to the Foundation for Chiropractic Education and Research (FCER) over wording appearing in the oft-consulted The Merck Manual. The bothersome wording was: "Manipulation may help pain caused by muscle spasm alone but may aggravate an arthritic joint or further rupture a disk and should thus be used with caution."

On behalf of the doctor brining it to attention, FCER drafted a letter to The Merck Manual editor-in-chief. Among the points raised were these:

Two lines of thought in this passage are problematic:

The passage as it reads implies that spinal manipulation may relieve pain by acting as a muscle relaxant alone. . . . Even in the case of muscle involvement, spasm is not the only mechanism responsible.

The statement concerning disk rupturing may have had its origins with the assertion made by Farfan over 34 years ago to the effect that rotational stress causes disk failure. . . . The safety of side posture manipulation in the treatment of lumbar intervertebral disk herniations is described in detail in the literature review by Cassidy et al.

In a letter dated July 27, 2004, Merck responded:

We have completely rewritten the chapter on back pain, and the statement you objected to is no longer present. While we do not go into great depth on the etiology of back pain, our new text emphasizes that the etiology is usually multifactorial, with muscle spasm being just one factor. We do comment on the helpfulness of spinal manipulation but retained a statement of caution in those with the possibility of nerve damage from disk disease. This statement does not single out chiropractic interventions: we include them
with almost every intervention, including the use of medications. In addition and for the first time, we will have a separate entry on chiropractic.

FCER is always pleased to use the knowledge and expertise of its staff in defense of the chiropractic profession. We are particularly pleased to have seen such a quick response from the editor of The Merck Manual and we look forward to checking the updated version for improvements!

In addition to supporting increased chiropractic research and increased public awareness opportunities, membership in and donations to FCER allow us to continue to defend the profession against inaccurate reporting.

For more information on FCER—and to see FCER’s full letter to Merck, the full response, as well as FCER responses to other injurious and/or erroneous articles—please visit FCER’s website at www.fcer.org.

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When a Doctor of Chiropractic voiced concern over phrasing in the popular Merck Manual to the Foundation for Chiropractic Education and Research (FCER), the following letter was drafted to the editor. The letter was composed by FCER’s Director of Research, Anthony L. Rosner, Ph.D.

Mark Beers, M.D.
Editor
The Merck Manual
Mailcode UD-100
Blue Bell, Pennsylvania 19422

Dear Dr. Beers:

I am writing to you as the Director of Research and Education of the Foundation for Chiropractic Education and Research, a nonprofit entity which for over 60 years has supported peer-reviewed research and postgraduate study in areas pertaining to the theory and practice of chiropractic healthcare. In this communication I am expressing my concern over a passage in Chapter 59, Section 5 of The Merck Manual which presents treatment scenarios for low back pain:

"Manipulation may help pain caused by muscle spasm alone but may aggravate an arthritic joint or further rupture a disk and should thus be used with caution."

Two lines of thought in this passage are problematic:

1. Cause of Pain:

The passage as it reads implies that spinal manipulation may relieve pain by acting as a muscle relaxant alone. It completely overlooks the role of inflammation, provoked in the case of disc pathology by the release of tumor necrosis factor alpha¹ which triggers an immune-mediated inflammation which in turn produces additional local noxious chemicals. Once healing begins and inflammation subsides, less pain is experienced.²

Even in the case of muscle involvement, spasm is not the only mechanism responsible. Excessive stretch or overload must also be considered, the former producing nerve damage. A number of mechanisms in the central nervous system could suppress pain transmission, the best studies having been done at the level of the spinal cord.² Whereas at least 42 randomized clinical trials have supported the effectiveness of spinal manipulation in relieving symptoms of back pain and improving functionality,³ I am aware of no references which address muscle spasm alone as suggested by your entry in the Manual.

2. Rupturing of Disk:

The statement concerning disk rupturing may have had its origins with the assertion made by Farfan over 34 years ago to the effect that rotational stress causes disk failure. This study demonstrated that in rotation, normal disks withstand an average of 23^o and degenerated disks an average of 14^o before failure.⁴ However, posterior facet joints limit rotation to a maximum of 2-3^o and would have to fracture to allow any further rotation to occur.⁵ Any disc failures produced experimentally by torsion are caused by peripheral tears in the annulus, rather than prolapse or herniation.⁵ The safety of side posture manipulation in the treatment of lumbar intervertebral disk herniations is described in detail in the literature review by Cassidy et al.⁶

For your reference, I have enclosed reprints of the Cassidy literature review⁶ plus two clinical trials which invoke spinal manipulation in the treatment of disc herniations. With no side-effects having been reported along with positive outcomes, the clear implication from these studies is that manipulation would be expected to improve rather than worsen disc herniations.^7,8 Furthermore, manipulation in marked contrast to the medical intervention to which it is compared, displays superior outcomes, far less cost, and no iatrogenic effects.⁸ A fourth reprint I have included demonstrates that, in patients with lumbar disc herniations, the recurrence of back pain occurs with equal frequencies in patients treated either with surgery or conservatively, the recommendation therefore being that conservative therapy rather than surgery should be the first option of treatment.⁹

All of this is to suggest that the statement in the Merck Manual in its current form, regarding manipulation as a treatment option for herniated disks, is misleading and at odds with the indexed literature. In the interest of patient welfare and safety, I ask that you give this letter your most thoughtful attention and amend the statement in the Manual accordingly.

I shall look forward to hearing from you and will be happy to elaborate upon any of the issues raised in this letter.

REFERENCES:

1. Olmarker K, Larsson K. Tumor necrosis factor-alpha and nucleus-pulposus-induced nerve root injury. Spine 1998; 23(23): 2538-2544.
2. Bove G, Swenson RS. Nociceptors, pain, and chiropractic. In Redwood D, Cleveland C [Eds.], Fundamentals of Chiropractic, St. Louis, MO: Mosby, 2003, pp. 187-207.
3. Meeker WC, Haldeman S. Chiropractic: A profession at the crossroads of mainstream and alternative medicine. Annals of Internal Medicine 2002; 136: 216-227.
4. Farfan HF, Cossette JW, Robertson GH, Wells, RV, Kraus H. The effects of torsion on the lumbar intervertebral joints: The role of torsion in the production of disc degeneration. Journal of Bone and Joint Surgery [Am]; 1970; 52(3): 468-497.
5. Adams MA, Hutton WC. Mechanics of the intervertebral disc. In Ghosh P [Ed.], The Biology of the Intervertebral Disc, volume II. Boca Raton, FL: Raven Press, 1988, pp. 39-71.
6. Cassidy JD, Thiel HW, Kirkaldy-Willis W. Side posture manipulation for lumbar intervertebral disk herniation. Journal of Manipulative and Physiological Therapeutics 1993; 16(2): 96-103.
7. Nwuga VCB. Relative therapeutic efficacy of vertebral manipulation and conventional treatment in back pain management. American Journal of Physical Medicine 1982; 61(6): 273-278.
8. Burton AK, TIllotson KM, Cleary J. Single-blind randomised controlled trial of chemonucleolysis and manipulation in the treatment of symptomatic lumbar disc herniation. European Spine Journal 2000; 9: 202-207.
9. Postacchini F. Spine update: Results of surgery compared with conservative management for lumbar disc herniations. Spine 1996; 21(11): 1383-1387.

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Response from Merck

This is the response that FCER’s Director of Research, Anthony Rosner, Ph.D., received from Mark H. Beers, M.D., Editor-in-Chief, The Merck Manual.

Dear Dr. Rosner:

Thank you for your letter of July 21 regarding a sentence in the 17th edition of The Merck Manual in our discussion of back pain. We are currently revising that edition, with the next printing scheduled for release next year. Subsequently, revised editions of The Merck Manual will occur at a much quicker pace, including on our web site.

We have completely rewritten the chapter on back pain, and the statement you objected to is no longer present. While we do not go into great depth on the etiology of back pain, our new text emphasizes that the etiology is usually multifactorial, with muscle spasm being just one factor. We do comment on the helpfulness of spinal manipulation but retained a statement of caution in those with the possibility of nerve damage from disk disease. This statement does not single out chiropractic interventions: we include them with almost every intervention, including the use of medications. In addition and for the first time, we will have a separate entry on chiropractic.

We thank you for your interest in improving the quality of The Merck Manual and appreciate your taking the time to write to us.

Sincerely,
Mark Beers

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