UW Radiology

Cohort Study

The Cohort Study for
The Treatment of Discogenic Back Pain (DISCO)


Discogenic back pain is a controversial diagnosis that often leads to aggressive surgical treatment. This study uses a prospective cohort design to better define the outcomes of spinal fusion for presumed discogenic pain and to compare them with outcomes of patients who have degenerated discs but no surgery.

Principal Investigator:

Sohail Mirza, MD
Associate Professor, Orthopaedics and Sprots Medicine
Harborview Medical Center Orthopaedics
University of Washington, Department of Neurological Surgery

Research Questions

    1. For patients undergoing lumbar fusion for discogenic back pain, how do pre-operative physical and psychological function compare with patients who have degenerative discs but receive only non-surgical care?

      We hypothesize that patients undergoing fusion for discogenic pain may have greater preoperative psychological distress than patients not undergoing fusion.

    1. For patients undergoing fusions for discogenic pain, how do clinical and functional outcomes compare with patients undergoing non-surgical care?

      The outcomes of interest include symptoms, function, return to work, and subsequent surgery. We hypothesize that symptoms will improve more after fusion than after non-surgical care.

    1. What is the frequency of common complications of spinal fusion and what are their consequences?

      We hypothesize that a prospective study with uniform follow-up will disclose a higher complication rate than is typically reported in the literature (due to incomplete follow-up and potential conflicts of interest).

    1. What are the major predictors of favorable functional outcomes of both surgical and non-surgical care for discogenic pain?

      Are there characteristics that predict a good response to surgical therapy but not to others, that would aid in optimal patient selection? Predictor variables to be assessed include age and sex, work and disability compensation status, baseline pain severity and duration, imaging results, functional status, and psychological distress.

  1. How do patients undergoing repeat surgery compare with patients undergoing first time surgery?

    We hypothesize that patients undergoing repeat surgery will have worse preoperative physical and psychological function than those having first-time surgery, and that benefits of surgery will be smaller.

Research Highlights
Current and previous work by our group on this topic:

1. A prospective cohort study of surgical treatment for back pain with degenerated discs; study protocol.
Deyo RA, Mirza SK, Heagerty PJ, Turner JA, Martin BI.
BMC Musculoskelet Disord. 2005 May 24;6(1):24. Abstract. PMID: 15913458 [PubMed – indexed for MEDLINE]

Background: The diagnosis of discogenic back pain often leads to spinal fusion surgery and may partly explain the recent rapid increase in lumbar fusion operations in the United States. Little is known about how patients undergoing lumbar fusion compare in preoperative physical and psychological function to patients who have degenerative discs, but receive only non-surgical care.

Methods: Our group is implementing a multi-center prospective cohort study to compare patients with presumed discogenic pain who undergo lumbar fusion with those who have non-surgical care. We identify patients with predominant low back pain lasting at least six months, one or two-level disc degeneration confirmed by imaging, and a normal neurological exam. Patients are classified as surgical or non-surgical based on the treatment they receive during the six months following study enrollment. Inclusion and exclusion criteria are listed in Table 1. These eligibility criteria mimic those of the European randomized trials of surgery for disc for discogenic pain.

Results: Three hundred patients discogenic low back pain will be followed in a prospective cohort study for two years. The primary outcome measure is the Modified Roland-Morris Disability Questionnaire at 24-months. We also evaluate several other dimensions of outcome, including pain, functional status, psychological distress, general well-being, and role disability.

Conclusion: The primary aim of this prospective cohort study is to better define the outcomes of lumbar fusion for discogenic back pain as it is practiced in the United States. We additionally aim to identify characteristics that result in better patient selection for surgery. Potential predictors include demographics, work and disability compensation status, initial symptom severity and duration, imaging results, functional status, and psychological distress.

2. Spinal-fusion surgery – the case for restraint.
Deyo RA, Nachemson A, Mirza SK.
N Engl J Med. 2004 Feb 12;350(7):643-4. NEJM Sounding Board. PMID: 14960750 [PubMed – indexed for MEDLINE]

The use of spinal-fusion surgery in the United States is rapidly increasing. National survey data indicate that the annual number of spinal-fusion operations rose by 77 percent between 1996 and 2001. In contrast, hip replacement and knee arthroplasty increased by 13 to 14 percent during the same interval (Figure 1). Spinal-fusion surgery is expensive, with the average hospital bill more than $34,000, excluding professional fees.

The rationale for spinal fusion is based on successful use of arthrodesis to prevent movement at painful joints or to correct joint deformities. In an arthrodesis procedure, opposing bone surfaces of a joint are roughened and packed with bone graft material. This induces new bone formation, which bridges the gap and fuses the bones into a single unit. Spinal arthrodesis was initially used for the treatment of severe scoliosis, spinal tuberculosis, and fractures. These indications now account for only a small fraction of spinal-fusion procedures, since indications have expanded to include pain from degenerative disorders. Now, approximately 75 percent of spinal fusions are performed for spondylosis (spinal degenerative changes), disk disorders, and spinal stenosis exclusive of deformities. The procedure may be performed alone or in conjunction with diskectomy or laminectomy. Wide geographic variations in use suggest a poor level of professional consensus on the indications.

Several factors may be contributing to the rapid increase in spinal-fusion surgery. Changes in the population, technological advances, and uncertainty regarding indications, as well as the financial incentives for surgeons, hospitals, and the device industry may have synergistic effects. Much of the increase in use has been in older adults, in association with laminectomy for spinal stenosis.3 Improved anesthetic techniques for older patients and the advent of axial spine imaging may have facilitated this rapid increase.

Other technological advances include new spinal-fixation devices, computer-guided and minimally invasive surgical techniques, and bone-graft substitutes and supplements such as bone morphogenetic proteins. The market for spinal implants and devices is estimated to be $2 billion a year, with an annual growth rate of 18 to 20 percent. A rapid rise in fusion rates, beginning in 1996, coincided with approval by the Food and Drug Administration (FDA) of intervertebral “fusion cages,” a new generation of surgical implants. Reimbursement for spinal procedures is more favorable than reimbursement for most other procedures performed by orthopedic surgeons and neurosurgeons.

Widening indications have also contributed to the rise in rates of fusion surgery. A recently added indication is so-called diskogenic pain, or low back pain without sciatica in patients with degenerative disks. This controversial diagnosis is often identified by provocative diskography, itself a controversial procedure. The test involves injecting contrast material into the nucleus pulposus of a possible culprit disk, in an effort to reproduce the patient’s pain. Diskogenic pain is distinct from disk herniation with radiculopathy, for which surgical treatment is usually a simple diskectomy. If surgical treatment is used, presumed diskogenic pain is typically treated with spinal fusion. Because back pain and disk degeneration are both nearly universal with aging, the number of potential candidates for such surgery is enormous.


Spinal-fusion surgery is undoubtedly effective for some conditions in some patients. However, wide variations in the rates of use of the procedure throughout the country, rapidly rising rates of surgery, high rates of reoperation, and high rates of complications generate concern that the procedure may be overused. Its efficacy for the most common indications, such as degenerative disk disease, remains unclear.

More evidence from clinical trials should be required for degenerative disk disease to be an accepted indication. Because of more frequent complications, more reoperations, and higher costs, the current use of surgical implants is difficult to justify in the absence of evidence of improved clinical outcomes.

Finally, the emphasis of research efforts should shift from examining how to perform fusion to examining who should undergo fusion. The indications for this invasive and expensive procedure remain unclear despite its rapidly expanding use. European randomized trials of spinal surgery versus nonsurgical treatments show that controlled trials are feasible. Although the use of sham surgery remains controversial for ethical reasons, we believe randomized trials incorporating a sham operation may be justifiable for this procedure, because it is not performed for a life-threatening condition, the primary clinical outcomes are subjective, and the rate of complications is high. The emergence of minimally invasive techniques for fusion may make sham-controlled trials more feasible and acceptable. Only with more and better clinical trials will the indications and optimal technique for spinal fusion become clear.

3. Trends and variations in the use of spine surgery.
Deyo RA, Mirza SK.
Clin Orthop Relat Res. 2006 Feb;443:139-46. Review. PMID: 16462438 [PubMed – indexed for MEDLINE]


Examining trends and geographic variations in clinical care offers insights into changes in clinical decision making. We summarized data on spine surgical rates, trends, and variations in the United States to highlight areas of professional uncertainty and questions for future research. The United States has the highest rate of spine surgery in the world, but spine surgery shows wider geographic variations than most other procedures (Figure 1). For example, Medicare data for 2001 showed sixfold variations in spine surgery rates among United States cities, and 10-fold variations in spine fusion rates.

United States spine surgery rates rose 55% in the 1980s. In the 1990s, studies of surgical rates became more difficult because 20% of discectomies shifted to an out-patient setting. Extrapolations from states with ambulatory surgery data suggest overall lumbar surgery rates continued to rise throughout the 1990s. The most rapid increase was for spinal fusion, which tripled during the 1990s and accounted for an increasing proportion of all spine procedures (Figure 3).

Some increases coincided with the introduction of new surgical implants. Despite new technologies, rates of repeat surgery after fusion were no lower than the rates after decompression alone. As new technology for spine surgery is introduced at an accelerating pace, we anticipate substantial changes in surgery patterns. Analysis of population-based data may be useful for surveillance of changes and their impacts.

Selected Bibliography

Deyo RA, Nachemson A, Mirza SK. Spinal-fusion surgery – the case for restraint. N Engl J Med. 2004 Feb 12;350(7):722-6. PMID: 14960750

Jarvik JG. Imaging of adults with low back pain in the primary care setting. Neuroimaging Clin N Am. 2003 May;13(2):293-305. Review. PMID: 13677808

Jarvik JG, Hollingworth W, Martin B, Emerson SS, Gray DT, Overman S, Robinson D, Staiger T, Wessbecher F, Sullivan SD, Kreuter W, Deyo RA. Rapid magnetic resonance imaging vs radiographs for patients with low back pain: a randomized controlled trial. JAMA. 2003 Jun 4;289(21):2810-8. PMID: 12783911

Gray DT, Hollingworth W, Blackmore CC, Alotis MA, Martin BI, Sullivan SD,Deyo RA, Jarvik JG. Conventional radiography, rapid MR imaging, and conventional MR imaging for low back pain: activity-based costs and reimbursement. Radiology. 2003 Jun;227(3):669-80. PMID: 12773674

Hollingworth W, Gray DT, Martin BI, Sullivan SD, Deyo RA, Jarvik JG. Rapid magnetic resonance imaging for diagnosing cancer-related low back pain. J Gen Intern Med. 2003 Apr;18(4):303-12. PMID: 12709099

Jarvik JG, Deyo RA. Diagnostic evaluation of low back pain with emphasis on imaging. Ann Intern Med. 2002 Oct 1;137(7):586-97. Review. PMID: 12353946

Hollingworth W, Deyo RA, Sullivan SD, Emerson SS, Gray DT, Jarvik JG. The practicality and validity of directly elicited and SF-36 derived health state preferences in patients with low back pain. Health Econ. 2002 Jan;11(1):71-85. PMID: 11788983

Jarvik JG. Don’t duck the evidence. Spine. 2001 Jun 15;26(12):1306-8. No abstract available. PMID: 11426140

Jarvik JJ, Hollingworth W, Heagerty P, Haynor DR, Deyo RA. The Longitudinal Assessment of Imaging and Disability of the Back (LAIDBack) Study: baseline data. Spine. 2001 May 15;26(10):1158-66. PMID: 11413431

Jarvik JG, Robertson WD, Wessbecher F, Reger K, Solomon C, Whitten R, Lumley T, Deyo RA. Variation in the quality of lumbar spine MR images in Washington State. Radiology. 2000 May;215(2):483-90. PMID: 10796929

Staiger TO, Paauw DS, Deyo RA, Jarvik JG. Imaging studies for acute low back pain. When and when not to order them. Postgrad Med. 1999 Apr;105(4): 161-2, 165-6, 171-2. Review. PMID: 10223094

Jarvik JG, Deyo RA, Koepsell TD. Screening magnetic resonance images versus plain films for low back pain: a randomized trial of effects on patient outcomes. Acad Radiol. 1996 Apr;3 Suppl 1:S28-31. No abstract available. PMID: 8796503

Jarvik JG. Back pain study relies on intermediate outcomes. Diagn Imaging (San Franc). 1995 Nov;17(11):55, 59, 62. PMID: 10163592

Taylor VM, Deyo RA, Ciol M, Farrar EL, Lawrence MS, Shonnard NH, Leek KM, McNeney B, Goldberg HI. Patient-oriented outcomes from low back surgery: a community-based study. Spine. 2000 Oct 1;25(19):2445-52. PMID: 11013495

Malter AD, McNeney B, Loeser JD, Deyo RA. 5-year reoperation rates after different types of lumbar spine surgery. Spine. 1998 Apr 1;23(7):814-20. PMID: 9563113

Elam K, Taylor V, Ciol MA, Franklin GM, Deyo RA. Impact of a worker’s compensation practice guideline on lumbar spine fusion in Washington State. Med Care. 1997 May;35(5):417-24. PMID: 9140332

Taylor VM, Deyo RA, Ciol M, Kreuter W. Surgical treatment of patients with back problems covered by workers compensation versus those with other sources of payment. Spine. 1996 Oct 1;21(19):2255-9. PMID: 8902971

Taylor VM, Deyo RA, Goldberg H, Ciol M, Kreuter W, Spunt B. Low back pain hospitalization in Washington State: recent trends and geographic variations. J Spinal Disord. 1995 Feb;8(1):1-7. PMID: 7711364

Ciol MA, Deyo RA, Kreuter W, Bigos SJ. Characteristics in Medicare beneficiaries associated with reoperation after lumbar spine surgery. Spine. 1994 Jun 15;19(12):1329-34. PMID: 8066512

Taylor VM, Deyo RA, Cherkin DC, Kreuter W. Low back pain hospitalization. Recent United States trends and regional variations. Spine. 1994 Jun 1;19(11):1207-12; discussion 13. PMID: 8073311

Deyo RA, Ciol MA, Cherkin DC, Loeser JD, Bigos SJ. Lumbar spinal fusion. A cohort study of complications, reoperations, and resource use in the Medicare population. Spine. 1993 Sep 1;18(11):1463-70. PMID: 8235817

Turner JA, Herron L, Deyo RA. Meta-analysis of the results of lumbar spine fusion. Acta Orthop Scand Suppl. 1993;251:120-2. No abstract available. PMID: 8451967

Turner JA, Ersek M, Herron L, Haselkorn J, Kent D, Ciol MA, Deyo R. Patient outcomes after lumbar spinal fusions. JAMA. 1992 Aug 19;268(7):907-11. Review. PMID: 1640622