The Origin of Lower Back Pain (Part I)
From Pinnacol's Medical Director
April 2011
We frequently encounter patients with low back pain (LBP). Deyo, in his review of physician visits for LBP, found in 2002 that LBP constituted 2.3 percent of the physician visits with little change since the early 1990s.1
This incidence, however, results in the most costly condition for working age adults, and there is no evidence that the cost is decreasing despite technological advances. Already, total direct and indirect costs for the treatment of LBP are estimated to be $100 billion annually.2
We ask our patients “Where does it hurt?” Though a logical question, can we rely on the information?
Panel discussions and differing opinions
The North American Spine Society (NASS) dealt with this issue at the national meeting in October of 2010. NASS recognized the problem of understanding the vagaries of back pain. Christopher Standaert, M.D., Physical Medicine, University of Washington, moderated a panel comprised of a surgeon, neuroscientist, psychologist, geneticist and himself.3
They debated the concept of the “pain generator” for the lumbar spine. Is the “pain generator” a valid concept or simplistic and misleading? The “pain generator” has been the focus of medical care and leads to many interventions.3
The individuals debated using the language of their respective disciplines that limited the understanding of fellow panel members. Each came from a different perspective.The panel generally agreed that, for most chronic LPB, the causes and mechanisms are inadequately researched and defined.
Dr. Vanna Apkarian, Ph.D., Northwestern University, noted, “We don’t understand chronic pain and don’t understand chronic back pain. We have very few scientifically validated treatment options for these conditions.”3
Geneticist, Michael Costigan, Ph.D., Harvard, commented, “My view, from my experience, is that we have been incredibly bad at our jobs, both at identifying pathological pain mechanisms and at developing new analgesics.”3
The concept of the “pain generator” dates to the early 20th century and has become progressively refined with improved imaging and interventional techniques. The fundamental understanding of chronic low back pain and appropriate treatment has remained elusive.
Dr. Standaert noted that our “hope is that you can find something that induces pain and then confirm what is an ongoing source of usual symptoms by provoking it. Then the hope is that you can then block it, take it out, fry it or kill it in some way.”3
Standaert expanded the conversation noting, “The idea of a local pain generator is a very simple model and ignores all sorts of other things happening in a person’s life. What if there are money troubles, a mean boss, a toxic work situation, hovering lawyers, or pain problems elsewhere in the family? What if the patient suffered abuse, trauma or neglect? What if depression of substance abuse overlies the situation? You can take out the ‘pain generator’ but often the person’s life doesn’t look much better. We don’t really understand the degree of complexity we are dealing with. The treatment rates and expenditures are rising steeply, but so is the number of people reporting functionally disabling low back pain.” 3,4
An issue for further study
In an epidemiologic, cross-sectional study on the origin of LBP, Sembrano, et.al. noted that, in a spine surgeon’s office, patients presenting for LBP, up to 25 percent of patients may have significant pain contribution from the hip or SI joints, and an additional 10 percent will still have an undefined pain source even after diagnostic workup. This underscores the need for clinicians to be aware of nonspinal pain generators and to appropriately pursue alternative diagnoses.6
The assessment of pain origins can prove illusive. Factually, Sembrano notes the variation in patients already in a surgeon’s office. When a patient presents with LBP, the assessment becomes individualized based on the physician’s skill, patient age, general condition, smoking, weight, motivation and the intersection of a wide range of psychological factors. The homunculus gives non-specific innervation to the low back with cross-over of neural pathways from the toes to the pelvis.
Confounding these factors is the patient’s interpretation of the pain. Most tests have poor interobserver reproducibility or validity.2
Also, patients in severe or chronic pain may report pain aggravation with almost any maneuver, thus decreasing the specificity of these tests.6Dr. Alf Nachemson observed that to term disc aging (degeneration) a disease and to rely on an uncertain pain provocation test to do a large surgical intervention with unproven results is not what spine surgeons should do, at least not until we have better diagnostic tests and have performed our prospective randomized studies to demonstrate for some minor subgroups of our patients with LBP that surgery is of long-term benefit.6
The next “Comments from Pinnacol’s Medical Director” column will discuss intervention therapies related to LBP.
1 Back pain prevalence and visit rates: estimates from U.S. national surveys, 2002. Deyo RA, et. al. Spine, 2006. Nov 1; 31(23):2724-7
2 Mechanical Low Back Pain. Hillis E. e-Medicine, 2010 http://emedicine.medscape.com/article/310353-overview
3 The Back Letter. Vol 26, No. 2, February 2011
4 Expenditures and Health Status Among Adults with Back and Neck Problems. Brook M., Deyo R., et. al. JAMA: 2008; 299(6):656-664 http://jama.ama-assn.org/content/299/6/656.full
5 Clinical Case Series How Often Is Low Back Pain Not Coming From the Back? Sembrano, J., et. al. Spine: 1 January 2009 - Volume 34 - Issue 1 - pp E27-E32
6 Waddell G et. al. Nonorganic physical signs in low-back pain. Spine 1980;5:117–25
7 Lumbar Disc Disease With Discogenic Pain: What Surgical Treatment Is Most Effective? Nachemson, Alf, MD, PhD. Spine: 1 August 1996 - Volume 21 - Issue 15 - pp 1835,1836
Impact of Spine Patient Outcomes Research Trial Results