UW Radiology

Epidemiology of Spinal Surgery

Epidemiology of Spinal Surgery: Rates and Trends

Description

Recent technical changes in spine surgery, including new spinal implants and a shift towards ambulatory surgery may affect surgical rates and re-operation rates for lumbar spine surgery. This project uses national and state databases to examine whether surgical rates continue to rise, and if the introduction of interbody fusion cages resulted in acceleration of surgery rates. We will also examine surgical rates among the elderly, examine surgery rates for spinal stenosis, and examine whether or not re-operation rates are increasing over time, and finally to determine if certain surgical procedures are associated with unusually high rates of re-operations.

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Principal Investigator

Richard A Deyo, MD, MPH

Research Questions

  1. To examine the extent to which previous increases in the use of spinal fusion surgery may have continued or accelerated. In particular, we will determine if there was a sharp increase in rates following the introduction of interbody fusion cages, new implants which made spinal fusion surgery technically easier.

    Spinal fusion surgery was the most rapidly increasing type of lumbar spine surgery during the 1980s. It has been suggested that advances in technology, including pedicle screw and plate systems, may have contributed to this rise, along with improvements in preoperative care, expanded training of spine surgeons, and reimbursement incentives. Spinal fusion rates appear to vary among geographic areas even more dramatically than rates of other types of back surgery. International rates of spinal fusion vary more than rates of other types of back surgeries, and Keller reported lumbar fusion rates varying ten-fold between communities located within 100 miles of each other in Northern New England. Rates of lumbar discectomy were strikingly less variable.

  2. To determine if previously identified rapid increases in spine surgical rates among elderly patients have continued since the 1980s. This group may represent a high priority for further studies of treatment efficacy and effectiveness. If possible, we will also examine vertebroplasty – a new procedure for osteoporotic compression fractures – which is used primarily in the elderly.

    In a study of Medicare beneficiaries aged 65 and older, we found that rates of spinal stenosis surgery increased 8-fold between 1979 and 1992. Furthermore, surgical rates for spinal stenosis varied almost five-fold among U.S. states. Perhaps not surprisingly, mortality and operative complications increased with age and comorbidity. This rising surgical rate was dramatically greater than among younger populations or for other diagnoses. Dartmouth investigators have shown that the overall rate of lumbar surgery among Medicare beneficiaries continued to rise by 57% from 1988 to 1997, though rates for specific diagnoses were not itemized. If this trend has continued, the older population represents a high priority for further studies of treatment efficacy and long-term outcome. These issues will become increasingly important with aging of the population

  3. To determine if reoperation rates for lumbar spine surgery are increasing over time, as suggested by our previous work. We will also examine whether reoperation rates are highest in geographic areas where primary operation rates are the highest.

    Our previous analysis of Medicare claims revealed a disconcerting trend. The probability of reoperation among patients having surgery in 1989 was slightly greater than the probability of reoperation for a cohort having surgery in 1985, during 3 years of follow-up. Because reoperation is generally regarded as an unfavorable outcome, such a finding may have important implications for patient selection or technical quality of care. To determine if this is a real and significant trend, it will be necessary to examine cohorts separated by longer time intervals, and to examine reoperation rates over longer periods. If reoperation rates are indeed increasing, it may suggest that advances in surgical technique are creating more problems (e.g., the need to remove hardware) or that increasing technical ease of surgery is resulting in less careful patient selection, and worse overall outcomes. Further work is also necessary to determine if any trend observed in the Medicare population is also true among younger adults.

  4. To determine reoperation rates associated with different types of lumbar spine surgery. If there are diagnoses or procedures which have unusually high reoperation rates, it may suggest potential problems with patient selection or technical quality of care.

    Our previous work described higher rates of reoperation among patients receiving certain types of surgery and for certain diagnoses. For example, among patients having surgery for degenerative disc disease, those who had spinal fusion surgery had nearly twice the rate of reoperations compared to those who did not have fusion surgery, even after adjusting for age, gender, prior surgery, comorbidity, and coverage by Workers’ Compensation. In contrast, patients undergoing spinal fusion in association with discectomy for a herniated disc had no differences in reoperation rates.

  5. To determine the extent to which ambulatory disc surgery has begun to replace inpatient disc surgery. This trend began in the mid-1990s, but its extent has not been documented.

    In the mid-1990s, ambulatory disc surgery became an increasingly common procedure. This included not only percutaneous techniques, but also increasing use of open spine surgery on an ambulatory basis(19). Furthermore, arthroscopic techniques have recently been validated and are more widely used. The trend towards ambulatory surgery seems to be greater in the United States than in other countries, perhaps because of managed care. The shift from inpatient to ambulatory surgery has been greatest for simple discectomy, although percutaneous techniques are being developed for other types of back surgery, as well. The magnitude of this shift has not been quantified, and the current proportion of lumbar spine operations performed on an ambulatory basis is unknown. This question has methodologic importance, because health services researchers studying surgical patterns and making international comparisons may have erroneous information if they are using only inpatient data. This shift also has implications for resource allocation, and largely unknown implications for long-term outcomes of care.

Research Highlights

1. U.S. NATIONAL TRENDS IN LUMBAR FUSION SURGERY FOR DEGENERATIVE CONDITIONS, 1990 – 2000

Objective: In 2001, approximately 122,000 lumbar fusions were performed in the U.S. On a population basis, this represented a 220% increase from 1990 in fusions per 100,000. The slope of the rising rate increased in 1996, when fusion cages were approved. From 1996 to 2001, the number of lumbar fusions increased over 113%, compared with 13-15% for hip replacement and knee arthroplasty. Rates of lumbar fusion rose most rapidly among patients aged 60 and above. In this group, rates increased 230% over the decade, compared with 180% among adults aged 40-59, and 120% among adults under age 40. The proportion of all lumbar operations involving a fusion increased for all diagnoses.

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Lumbar Spine Fusion Volumes: 122,316 lumbar fusions for degenerative conditions in 2001. This represents an increase in fusions from 1990–2001 of 220%

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Primary Diagnosis associated with lumbar fusion Rate of fusion surgery increased fastest among oldest patients: 230% for age greater than 60, 180% for age 40-59, 120% for age less than 40. For patients with primary diagnosis of degenerative change, instability, or stenosis, the percent of operations involving a fusion increased from 25% in 1988-89 to 51% in 2000 – 2001.

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Lumbar fusion volume by primary diagnosisProportion of operations involving fusion by diagnosis in 2001: Degenerative Changes: 70% Possible instability: 93% Spinal Stenosis: 26%.

2. VOLUMES, RATES, AND CHARGES FOR AMBULATORY AND INPATIENT LUMBAR SPINE SURGERY

Objective: To track trends nation-wide and state-specific trends from 1994-2000 in: 1. Population-based distributions of inpatient and outpatient procedures 2. Overall rates of inpatient and outpatient procedures (excluding cancer, infection, trauma cases) 3. Distributions of inpatient vs. outpatient procedure types Estimate nationwide rates of inpatient and outpatient lumbar spine surgery.

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% of Lumbar Spine Surgery Cases Done on Outpatient Basis in 1997-2000: SID and SASD (4 states combined) Combined inpatient and outpatient rates rose from 1994 – 2000.

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Rates of All Inpatient Lumbar Spinal Surgical Procedures

Co-Investigators

•  Darryl T.Gray
•  Sohail Mirza
•  William Kreuter
•  Brook Martin
•  Bryan Comstock

Selected Bibliography

  1. Cherkin DC, Deyo RA, Loeser JD, Bush T, Waddell G. An International Comparison of Back Surgery Rates. Spine 1994;19:1201-06.

  2. Taylor VM, Deyo RA, Cherkin DC, Kreuter W. Low Back Pain Hospitalization; Recent United States trends and regional variations. Spine 1994; 19:1207-13.

  3. 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 Disorders 1995;8:1-7.

  4. Katz JN. Lumbar Spinal Fusion: Surgical rates, costs, and complications. Spine 1995;20:78S-83S.

  5. Weinstein JN, et al. The Dartmouth Atlas of Musculoskeletal Health Care. AHA Press, 2000.

  6. 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;18:1463-70.

  7. Malter AD, McNeney B, Loeser JD, Deyo RA. 5-Year Reoperation Rates After Different Types of Lumbar Spine Surgery. Spine 1998;23:814-20.

  8. Ciol MA, Deyo RA, Howell E, Kreif S. An Assessment of surgery for spinal stenosis: time trends, geographic variations, complications, and reoperations. J Am Geriatr Soc 1996; 44:285-90.

  9. Osterweis M, Kleinman A, Mechanic D. Pain and disability: clinical, behavioral, and public policy perspectives. Washington, D.C.: National Academy Press, 1987.

  10. Keller RG, Atlas SJ, Soule DN, Singer DE, Deyo RA. Relationship between rates and outcomes of operative treatment for lumbar disc herniation and spinal stenosis. J Bone Joint Surg (Am) 1999;81:752-62.

  11. Abraham DJ, Herkowitz HN, Katz JN. Indications for Thoracic and Lumbar Spine Fusion and Trends in Use. Orthopedic Clinics of North America 1998;29:803-11.

  12. Keller RB. Outcomes research in Orthopaedics: a comprehensive review. J Am Acad Orthop Surg 1993;1:122-129.

  13. Turner JA, Ersek M, Herron L, Deyo R, et al. Patient outcomes after lumbar spinal fusions. JAMA 1992;268:907-11.

  14. Deyo RA, Cherkin DC, Loeser JD, Bigos SJ, Ciol MA. Morbidity and Mortality in Association with Operations on the Lumbar Spine. The Influence of Age, Diagnosis, and Procedure. J Bone Joint Surg. 1992; 74A:536-43.

  15. Oldridge ND, Stoll JE, Juan Z, Rimm AA. Admission and surgical rates for low back pain in 1986 Medicare patients over 65 years of age. Presented at N Am Spine Soc annual meeting. Boston, July 9-11, 1992.

  16. Katz JN, Lipson SJ, Lew RA, Grobler LJ, Weinstein JN, Brick GW, Fossel AH, Liang MH. Lumbar Laminectomy Alone or with Instrumented or Noninstrumented Arthrodesis in Degenerative Lumbar Spinal Stenosis: Patient selection, costs and surgical outcomes. Spine 1997;22:1123-31.

  17. Thomsen K, Christensen FB, Eiskjaer SP, Hansen ES, Fruensgaard S, Bunger CE. 1997 Volvo Award Winner in Clinical Studies. The Effect of Pedicle Screw Instrumentation on Functional Outcome and Fusion Rates in Posterolateral Lumbar Spinal Fusion: A Prospective, Randomized Clinical Study. Spine 1997;22:2313-22.

  18. Fischgrund JS, Mackay M, Herkowitz HN, et al. 1997 Volvo Award Winner in clinical studies. Degenerative lumbar spondylolisthesis with spinal stenosis: A prospective, randomized study comparing decompressive laminectomy and arthrodesis with oandr without instrumentation. Spine 1997;22:2807-2812.

  19. Bookwalter JW, Busch MD, Nicely D. Ambulatory surgery is safe and effective in radicular disc disease. Spine 1994;19:526-30.

  20. Hermantin FU, Peters T, Quartararo L, Kambin P. A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg (Am) 1999;81:958-65.

  21. Cherkin DC, Deyo RA, Volinn E, Loeser JD. Use of the International Classification of Diseases (ICD-9-CM) to identify hospitalizations for mechanical low back problems in administrative data bases. Spine 1992;17:817-824.

  22. Deyo RA, Taylor VM, Diehr P, Conrad D, Cherkin DC, Ciol M, Kreuter W. Analysis of Automated Administrative and Survey Databases to Study Patterns and Outcomes of Care. Spine 1994;19:20835-915.

  23. Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with ICD-9-CM administrative databases. J Clin Epidemiol 1992;45:613-619.

  24. Taylor VM, Anderson GM, McNeeny B, Diehr P, Lavis JN, Deyo RA, et.al. Hospitalization for back and neck problems: a comparison between the province of Ontario and Washington State. Health Serv Res 1998; 33:929-94.

  25. 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. Medical Care 1997;35:417-24.

  26. 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;21:2255-9.

  27. Ciol MA, Deyo RA, Kreuter W, Bigos SJ. Characteristics in Medicare beneficiaries associated with reoperation after lumbar spine surgery. Spine 1994; 19:1329-34.

  28. Gray DT, Hedge DO, Ilstrup DM, et al. Concordance of Medicare data and population-based clinical data on cataract surgery utilization in Olmsted County, Minnesota. Am J Epi 1997;145:1123-1126.

  29. Gray DT, Suman VJ, Su WPD, et al. Trends in the population-based incidence of squamous cell carcinoma of the skin first diagnosed between 1984 and 1992. Arch Dermatol 1997;133:735-40.

  30. Kalbfleisch JD, Prentice RL. The statistical analysis of failure time data. New York: Wiley and Sons, 1980:10-6, 70-117.

  31. Fleming TR, Harrington DP. Counting process and Survival Analysis. New York: John Wiley and Sons, 1991:125-201