By Raphael Rey Roybal, M.D.

Back pain continues to afflict numerous patients, accounting for billions of dollars spent for treatment, lost work days, and immeasurable human suffering. Accordingly, countless studies have been preformed evaluating the efficacy of numerous treatments of back pain. Much effort has also been dedicated to the equally challenging task of identifying the potential pain generators responsible for back pain.

Whereas radicular pain of the extremities originating from the spine due to a neurocompressive lesion is usually more easily diagnosed and treated with scientifically accepted modalities, axial back pain is far more nebulous because of the large number of potential structural pain generators with an overlapping constellation of symptoms. Although the majority of back pain is muscular in origin and self-limited, various anatomical structures of the human spine have been impugned as the cause of pain by several evidence based studies.

Facet Joints

The Facet Joints are vital to the spinal motion segment as they assist in maintaining stability, protect the discs from excessive stress, and allow for controlled motion reducing shear forces. In 2007, prevalence studies estimate that between 15-30% of chronic low back pain is caused by painful facet joints (1). Typically, symptoms include worse pain with extension and standing with relief when sitting. Often, pain can radiate or lateralize mimicking radicular pain. Although options are limited, treatment including physical therapy as well as interventional injections termed medial branch facet blocks may be successful. Although by definition a medial branch block is an anesthetic block used for the diagnosis of facet pain, a successful block may lead to a neurotomy or ablation rhizotomy which de-innervates the pain fibers responsible for facet pain. Randomly controlled trials demonstrated that a medial branch neurotomy was significantly better than placebo treatment up to 12 months. (2) Furthermore, follow up studies demonstrated maintained efficacy with repeat neurotomies as needed. (3)

Sacroiliac Joint

As the joint articulating the sacrum to the lliac wing of the pelvis, the Sacroiliac (SI) joint forms the base of the spinal axis transmitting loads from the trunk to the lower extremities. Although SI joint pain may originate idiopathically, trauma or even the hyper-mobility of pregnancy may play a role in SI joint dysfunction. Described in 1996, SI joint pain may manifest as groin pain, pain in the buttocks or sacral sulcus, or even as a radicular syndrome without actual neural compression. (4) The Patrick’s test or Flexion-Abduction-External Rotation of the hip (FABER) may also help diagnose a painful SI joint. However, the gold standard diagnosis remains elimination of pain via a fluoroscopically guided corticosteroid injection into the painful joint. Along with physical therapy concentrating on the gluteal muscles, serial corticosteroid injections and NSAIDs are the accepted treatment options. (5)

Intervertebral Disc

The most commonly impugned anatomic structure in back pain is likely the intervertebral disc. Unfortunately, its status as a pain generator as well as the potential appropriate treatment remains a true controversy in the medical world. A summary of the efficacy of virtually all commonly practiced treatment options have been recently published in the official journal of the North American Spine Society (NASS). For true discogenic pain, the only statistically significant successful interventions were core strengthening (physical therapy) and potentially surgery. (6) However, much controversy remains in the correct diagnosing of true discogenic pain. Most commonly, symptoms include pain with sitting, valsalva or coughing, or transition from sitting to standing. (7) Again, pain may radiate into the buttocks or proximal leg resembling radiculopathy, SI joint pain, and even facet pain. Numerous studies have been conducted that examine the pathology of the intervertebral disc and the associated boney endplates as well as proposing the mechanisms of discogenic pain. (8,9,10) Unfortunately, the imaging on both xray and MRI is most often nonspecific and reflective of normal age related changes at best. Some attempts have been made to correlate high intensity signals in the disc annulus (High Intensity Zone or annular tears) to painful discs; however, these correlations have been at times weak. In recent times, Eugene Caragee, an orthopaedic spine surgeon, has examined extensively the utility and validity of provocative discography in identifying the disc as a true pain generator. (11, 12) The accuracy of discography has been challenged in these studies by the fact that many false positives have been reported; however, the specificity of discography significantly rises when used to examine carefully selected patients highly suspicious for having discogenic pain who also have characteristic changes observed on MRI’s. More Recently, Sengupta has demonstrated the successful identification of pathologic discs via discography 90% of the time when associated with annular tears and Modic changes (degenerative changes) to the boney endplates. (13) Furthermore, a follow up study demonstrated 78% successful outcome in terms of increased function and decreased pain when all positive discs were treated surgically by arthrodesis (fusion). (14)

How successful is surgical arthrodesis in the treatment of a positively identified painful, pathologic disc when compared to non-operative treatment? In 2001, Fritzell published the first randomly controlled study comparing spinal fusion to regular non-operative treatment for chronic discogenic low back pain. (15) Although the operative patients had statistically superior results compared to the conservatively treated patients, this study has at times been criticized because of the lack of a regimented, uniform conservative program. In response, three subsequent randomly controlled studies have been published with very regimented conservative controls including long-term inpatient physical therapy. (16) Although the clinical differences were less dramatic between groups, an 18.3 reduction in the Oswestry Disability Index in the surgical patients compared to only an 8.3 reduction in the conservatively treated patients again indicates a positive role for surgical arthrodesis in carefully selected patients. Researchers have published that at least a 12 point reduction in the Oswestry Disability Index is necessary for a clinically significant improvement in the quality of life of patients.

Technological advancement has also produced exciting evidence supporting operative intervention for the treatment of chronic back pain. Two multi-center FDA Investigational Device Exemptions studies for disc arthoplasty compared disc replacement to arthrodesis in the treatment of positively identified painful discs. (17, 18) Both lead authors, hailing from the Texas Back Institute, demonstrated little differences between the disc replacement patients vs. the fusion patients. However, it should be noted that both patients had significantly improved function, pain scores and disability scores at all measured time points. Despite these findings, the treatment of low back pain remains controversial. Rigorous study, however, has indicated a statistically significant benefit for carefully selected patients treated surgically for back pain. At present, the challenges faced in diagnosing and treating patients suffering from chronic low back pain requires the combination of both the science and art of medicine.

References

1. Eubanks, Clinical Orthopaedics 2007
2. Dreyfuss, Spine 2000
3. Schofferman, Spine 2004
4. Dreyfuss, Spine 1996
5. Hawkins, NASS 2005
6. Caragee, Spine Journal, 2008
7. Young, Spine Journal 2003
8. Yoganandan, Spine 1988
9. Ariga, Spine 2001
10. Fagan, Spine 2003
11. Caragee, Spine 1999
12. Caragee, Spine 2006
13. Sengupta, Spine Journal 2008
14. Sengupta, Spine Journal 2008
15. Fritzell, Spine 2001
16. Brox, Spine Journal 2008
17. Blumenthal, Spine 2005
18. Ziglar, Spine 2006

For more information about this article, you can contact Dr. Roybal at Chatham Orthopaedics, 4425 Paulsen Street, Savannah, GA 31405 or call him at (912) 355-6615.