Spinal-Fusion Surgery — The Case for Restraint
http://www.100md.com
《新英格兰医药杂志》
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 2001.1 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.1
Figure 1. Annual Number of Knee-Arthroplasty, Hip-Replacement, and Spinal-Fusion Operations in the United States, on the Basis of the National Inpatient Sample.
Data are from the Agency for Healthcare Research and Quality.1
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.1 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.2
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.4 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.5 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.6,7 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 for Degenerative Conditions
Spinal stenosis associated with lumbar spondylolisthesis (anterior displacement of a vertebra on the one beneath it) is one degenerative condition for which the data suggest some beneficial effects of spinal fusion. A randomized trial and a study with alternating treatment assignments indicated better outcomes for laminectomy plus fusion than for laminectomy alone.8,9 A randomized trial involving patients with isthmic spondylolisthesis and disabling pain for at least a year suggested better results from fusion surgery than from nonsurgical care,10 although the differences in outcome narrowed over a five-year follow-up period.11 For patients with spinal stenosis but no spondylolisthesis, a randomized trial suggested that laminectomy alone is as effective as laminectomy plus fusion,12 although a cohort study suggested an advantage for noninstrumented fusion (fusion without surgical implants).13
In contrast to the results of trials involving patients with spondylolisthesis, there is little evidence to support spinal fusion in association with diskectomy for patients with herniated disks and radiculopathy. Although there have been no randomized trials of lumbar diskectomy plus fusion versus diskectomy alone, comparative cohort studies generally suggest that there is no advantage to adding fusion.14 Randomized trials of cervical diskectomy indicate equally good clinical outcomes with diskectomy alone and with diskectomy plus fusion.15,16 Nonetheless, a growing proportion of cervical disk operations include a fusion procedure.17
Diskogenic pain is perhaps the most controversial indication for performing spinal fusion. Advocates are supported by the results of a recent Swedish randomized trial comparing spinal fusion with nonsurgical care for patients with one- or two-level disk degeneration.18 The nonsurgical group received a broad range of treatments, including physical therapy, electrical nerve stimulation, acupuncture, injections, and cognitive training, according to the individual physician's preference. The surgical group had greater improvement than the nonsurgical group in pain relief, function, depressive symptoms, and return to work. Nonetheless, only 63 percent of the patients in the surgical group considered themselves "much better" or "better."
Critics of the Swedish study note that the magnitude of the benefit from fusion was small: pain and functioning improved by about 30 percent on average, and only one in six patients became free of pain. The trial was not blinded, and the improvements in the surgical group diminished between one and two years of follow-up, suggesting that any benefit may have been temporary. The nonsurgical group was treated with heterogeneous therapies that may not have represented optimal nonsurgical care.
A more recent randomized trial compared spinal fusion with a more standardized rehabilitation approach for patients with diskogenic pain. The rehabilitation approach focused on returning patients to their normal activities, reducing their anxiety about back pain, and promoting exercise. In this trial, surgery offered no advantage in pain relief or functional improvement.19 Thus, there are conflicting results from clinical trials and small benefits at best from spinal fusion among patients with diskogenic pain. A systematic review in 1999 concluded that "there is no acceptable evidence of the efficacy of any form of fusion for degenerative lumbar spondylosis, back pain, or `instability.'"20 Similar doubts have emerged regarding fusion for neck pain presumed to result from degenerative cervical spondylosis.21
Fundamental problems plague the study of spinal fusion, including the lack of definitive methods to confirm a solid fusion, a weak association between solid fusion and pain relief, and the placebo effect of surgery for pain relief.22 Although a solid fusion is somewhat more likely to result in pain relief than fusions that are not solid (pseudarthrosis), many patients with the latter have excellent pain relief, while many who have a solid fusion have poor results.8,23 Furthermore, psychosocial factors are important predictors of the clinical outcome. Factors associated with the outcome in a statewide survey, for example, included income, age, the presence or absence of involvement in litigation, and the presence or absence of depression.24
The Value of Surgical Implants for Spinal Fusion
Surgical implants are used in a growing proportion of fusion operations. In published clinical studies of lumbar fusion, reported rates of internal fixation nearly doubled from the 1980s to the 1990s.25 Perhaps the most popular implants are pedicle screws. Since 1996, intervertebral fusion cages have also gained popularity. Both were introduced without randomized trials or prospective cohort comparisons.
Pedicle screws have now been subjected to several randomized trials, comparing fusion with bone grafting alone to fusion with pedicle screws. These trials consistently showed no clinical advantage for fixation with pedicle screws, although some showed somewhat higher rates of solid fusion.8,23,26,27,28,29,30 A randomized trial suggesting better clinical outcomes with instrumentation removed patients with the worst prognosis (because of severe osteopenia) from the internal-fixation group at the time of surgery, and added them to the bone-graft group.31 The results of some randomized trials and cohort studies suggest superior clinical outcomes without pedicle screws.13,27 In studies comparing fusion with and without pedicle screws, patients in whom pedicle screws were used had a higher likelihood of reoperation,27,28,32,33 a higher rate of nerve injury,28,29,34 greater blood loss,28,29 a longer operative time,28,29 and a higher rate of complications.33
Implants are expensive, adding thousands or tens of thousands of dollars to the cost of each operation. Even if a marginal advantage of fusion with implants is hypothesized, a cost-effectiveness analysis has suggested that laminectomy with an instrumented fusion, as compared with a noninstrumented fusion, would result in an incremental cost-effectiveness ratio of more than $3 million per quality-adjusted year of life.35
Complications and Reoperations
Unlike simple diskectomy or laminectomy, spinal fusion requires decortication of bone and, often, placement of implants; spinal fusion also requires more extensive dissection and longer operative time. Thus, it is not surprising that fusion is associated with more complications than are other types of spinal surgery. Among Medicare patients, in comparison with any operation without fusion, surgery that included fusion was associated with a doubling of the risk of complications, an increase in the rate of blood transfusion by a factor of six, and a doubling of postoperative mortality assessed at six weeks.36 This was true even though patients who had fusions were slightly younger and were less likely to have coexisting conditions than were those who had surgery without fusion.
Common complications include instrument failure, occurring in about 7 percent of cases, and complications at the bone-donor site (usually the iliac crest), including infection and chronic pain.14 Complications at the donor site are reported in about 11 percent of cases. Neural injuries are reported in almost 3 percent of cases, pulmonary embolus in 2 percent, and infections in about 3 percent. Vascular complications are rare but potentially catastrophic.37 Failure to achieve a solid fusion mass, or pseudarthrosis, occurs in about 15 percent of cases in most series.14 Though rare, blindness as a consequence of fusion surgery has been reported, probably due to ischemic injury with intravascular volume shifts and the position of the patient during surgery.38
Reoperation is often considered a poor outcome of spinal surgery, because it suggests ongoing or recurrent back problems. Spinal fusions are sometimes performed after previous back surgery has failed, on the assumption that fusion will be a definitive procedure, obviating the need for further intervention. Ironically, though, the rates of reoperation after spinal fusion surgery may be slightly higher than the rates of reoperation after laminectomy or diskectomy without fusion.39,40 Paradoxically, rates of reoperation are even higher for fusion with the use of internal-fixation devices than for bony fusion alone.27,28,29,32,33
Recommendations
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.
Evidence-based practice for degenerative spine disorders might reserve the use of spinal fusions for spondylolisthesis and only rare cases of disk herniation or spinal stenosis without spondylolisthesis. 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. Patients should be informed that pedicle screws are approved only for spondylolisthesis, fractures, dislocation, deformity, spinal tumors, and pseudarthrosis. Financial incentives should be better aligned with the data on the safety and efficacy of spinal procedures.
Emerging spinal implants such as artificial disks should be approached with caution. The data on the efficacy and safety of these devices have been disappointing to date.41 If ongoing trials suggest results equivalent to those of spinal fusion, it may be faint praise, given the paucity of evidence that spinal fusion is safe and effective for common indications. Similar concerns apply to other new techniques for treating back pain, including electrothermal therapy, analgesic pumps, and implanted spinal stimulators.
The FDA should provide closer scrutiny of spinal implants and their use for unapproved indications. For all new spinal implants and new indications, randomized trials should be required before approval is issued by the FDA. Rigorous postmarketing surveillance for adverse events should become mandatory.
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.18,19 Although the use of sham surgery remains controversial for ethical reasons,42 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.
All opinions and conclusions expressed in this article are those of the authors and do not necessarily reflect the views of the sponsoring organizations.
Supported in part by grants (P60 AR48093 and 5K23 AR48979) from the National Institute of Arthritis and Musculoskeletal and Skin Diseases and by an Investigator Award in Health Policy Research from the Robert Wood Johnson Foundation. The University of Washington has received a gift to support research on spinal disorders from Synthes, a manufacturer of orthopedic devices used in spinal surgery; Drs. Deyo and Mirza report that they are likely to receive support for their research from this gift.
Source Information
From the Departments of Medicine (R.A.D.) and Orthopedic Surgery (S.K.M.) and the Center for Cost and Outcomes Research (R.A.D., S.K.M.), University of Washington, Seattle; and the Department of Orthopedic Surgery, University of Gothenburg, Gothenburg, Sweden (A.N.).
Address reprint requests to Dr. Deyo at 146 N. Canal Street, Suite 300, Seattle, WA 98103.
References
Agency for Healthcare Research and Quality. Healthcare Cost and Utilization Project, HCUPnet. (Accessed January 22, 2004, at http://www.ahrq.gov/data/hcup/.)
Katz JN. Lumbar spinal fusion: surgical rates, costs, and complications. Spine 1995;20:Suppl:78S-83S.
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;44:285-290.
Boden SD, Kang J, Sandhu H, Heller JG. Use of recombinant human bone morphogenetic protein-2 to achieve posterolateral lumbar spine fusion in humans: a prospective, randomized clinical pilot trial. Spine 2002;27:2662-2673.
Mendenhall Associates, Inc. 2002 Spinal industry update. Orthopedic Network News 2002;13(4):7-8.
Nachemson A. Lumbar discography -- where are we today? Spine 1989;14:555-557.
Carragee EJ. Is lumbar discography a determinate of discogenic low back pain: provocative discography reconsidered. Curr Rev Pain 2000;4:301-308.
Fischgrund JS, Mackay M, Herkowitz HN, Brower R, Montgomery DM, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective randomized study comparing decompressive laminectomy and arthrodesis with and without spinal instrumentation. Spine 1997;22:2807-2812.
Herkowitz HN, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective study comparing decompression with decompression and intertransverse process arthrodesis. J Bone Joint Surg Am 1991;73:802-808.
Moller H, Hedlund R. Surgery versus conservative management in adult isthmic spondylolisthesis -- a prospective randomized study: part 1. Spine 2000;25:1711-1715.
Ekman P, Hedlund R, Moller H. Fusion in adult isthmic spondylolisthesis: a long term follow-up of a prospective randomised study. Presented at the annual meeting of the Nordic Spine Deformity Society, Malmo, Sweden, August 23, 2003.
Grob D, Humke T, Dvorak J. Degenerative lumbar spinal stenosis: decompression with and without arthrodesis. J Bone Joint Surg Am 1995;77:1036-1041.
Katz JN, Lipson SJ, Lew RA, et al. Lumbar laminectomy alone or with instrumented or noninstrumented arthrodesis in degenerative lumbar spinal stenosis: patient selection, costs, and surgical outcomes. Spine 1997;22:1123-1131.
Turner JA, Ersek M, Herron L, et al. Patient outcomes after lumbar spinal fusions. JAMA 1992;268:907-911.
Savolainen S, Rinne J, Hernesniemi J. A prospective randomized study of anterior single-level cervical disc operations with long-term follow-up: surgical fusion is unnecessary. Neurosurgery 1998;43:51-55.
Dowd GC, Wirth FP. Anterior cervical discectomy: is fusion necessary? J Neurosurg 1999;90:Suppl:8-12.
Angevine PD, Arons RR, McCormick PC. National and regional rates and variation of cervical discectomy with and without anterior fusion, 1990-1999. Spine 2003;28:931-940.
Fritzell P, Hagg O, Wessberg P, Nordwall A. Lumbar fusion versus nonsurgical treatment for chronic low back pain: a multicenter randomized controlled trial from the Swedish Lumbar Spine Study Group. Spine 2001;26:2521-2532.
Ivar Brox J, Sorenson R, Friis A, et al. Randomized clinical trial of lumbar instrumented fusion and cognitive intervention and exercises in patients with chronic low back pain and disc degeneration. Spine 2003;28:1913-1921.
Gibson JNA, Grant IC, Waddell G. The Cochrane review of surgery for lumbar disc prolapse and degenerative lumbar spondylosis. Spine 1999;24:1820-1832.
Fouyas IP, Statham PFX, Sandercock PAG. Cochrane review on the role of surgery in cervical spondylotic radiculomyelopathy. Spine 2002;27:736-747.
Moseley JB, O'Malley K, Petersen NJ, et al. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med 2002;347:81-88.
France JC, Yaszemski MJ, Lauerman WC, et al. A randomized prospective study of posterolateral lumbar fusion: outcomes with and without pedicle screw instrumentation. Spine 1999;24:553-560.
DeBerard MS, Masters KS, Colledge AL, Schleursener RL, Schlegel JD. Outcomes of posterolateral lumbar fusion in Utah patients receiving workers' compensation: a retrospective cohort study. Spine 2001;26:738-747.
Bono C, Lee C. Critical analysis of trends in fusion for degenerative disc disease over the last 20 years: influence of technique on fusion rate and clinical outcome. Presented at the annual meeting of the International Society for the Study of the Lumbar Spine, Vancouver, B.C., Canada, May 13–17, 2003.
Moller H, Hedlund R. Instrumented and noninstrumented posterolateral fusion in adult spondylolisthesis -- a prospective randomized study: part 2. Spine 2000;25:1716-1721.
Bjarke Christensen F, Stender Hansen E, Laursen M, Thomsen K, Bunger CE. Long-term functional outcome of pedicle screw instrumentation as a support for posterolateral spinal fusion: randomized clinical study with a 5-year follow-up. Spine 2002;27:1269-1277.
Thomsen K, Christensen FB, Eiskjaer SP, Hansen ES, Fruensgaard S, Bunger CE. The effect of pedicle screw instrumentation on functional outcome and fusion rates in posterolateral lumbar spinal fusion: a prospective, randomized clinical study. Spine 1997;22:2813-2822.
Fritzell P, Hagg O, Wessberg P, Nordwall A. Chronic low back pain and fusion: a comparison of three surgical techniques: a prospective multicenter randomized study from the Swedish Lumbar Spine Study Group. Spine 2002;27:1131-1141.
McGuire RA, Amundson GM. The use of primary internal fixation in spondylolisthesis. Spine 1993;18:1662-1672.
Zdeblick TA. A prospective randomized study of lumbar fusion: preliminary results. Spine 1993;18:983-991.
Franklin GM, Haug J, Heyer MJ, McKeefrey SP, Picciano JF. Outcome of lumbar fusion in Washington State workers' compensation. Spine 1994;19:1897-1904.
Fritzell P, Hagg O, Nordwall A. Complications in lumbar fusion surgery for chronic low back pain: comparison of three surgical techniques used in a prospective randomized study. Eur Spine J 2003;12:178-189.
Bernhardt M, Swartz DE, Clothiaux PL, Crowell RR, White AA III. Posterolateral lumbar and lumbosacral fusion with and without pedicle screw internal fixation. Clin Orthop 1992;284:109-115.
Kuntz KM, Snyder RK, Weinstein JN, Pope MH, Katz JN. Cost-effectiveness of fusion with and without instrumentation for patients with degenerative spondylolisthesis and spinal stenosis. Spine 2000;25:1132-1139.
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;18:1463-1470.
Richardson WJ. Complications in spinal surgery. Current Opin Orthoped 1993;4:155-9.
Myers MA, Hamilton SR, Bogosian AJ, Smith CH, Wagner TA. Visual loss as a complication of spine surgery: a review of 37 cases. Spine 1997;22:1325-1329.
Malter AD, McNeney B, Loeser JD, Deyo RA. 5-Year reoperation rates after different types of lumbar spine surgery. Spine 1998;23:814-820.
Martin BI, Kreuter W, Gray DT, Heagerty PJ, Deyo RA. Lumbar spine surgery reoperation rates in Washington State derived from the Comprehensive Hospital Abstract Reporting System (CHARS). Presented at the annual meeting of the Western Regional Epidemiology Network, Ashland, Oreg., May 16, 2003.
de Kleuver M, Oner FC, Jacobs WC. Total disc replacement for chronic low back pain: background and a systematic review of the literature. Eur Spine J 2003;12:108-116.
Horng S, Miller FG. Is placebo surgery unethical? N Engl J Med 2002;347:137-139.(Richard A. Deyo, M.D., M.)
Figure 1. Annual Number of Knee-Arthroplasty, Hip-Replacement, and Spinal-Fusion Operations in the United States, on the Basis of the National Inpatient Sample.
Data are from the Agency for Healthcare Research and Quality.1
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.1 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.2
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.4 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.5 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.6,7 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 for Degenerative Conditions
Spinal stenosis associated with lumbar spondylolisthesis (anterior displacement of a vertebra on the one beneath it) is one degenerative condition for which the data suggest some beneficial effects of spinal fusion. A randomized trial and a study with alternating treatment assignments indicated better outcomes for laminectomy plus fusion than for laminectomy alone.8,9 A randomized trial involving patients with isthmic spondylolisthesis and disabling pain for at least a year suggested better results from fusion surgery than from nonsurgical care,10 although the differences in outcome narrowed over a five-year follow-up period.11 For patients with spinal stenosis but no spondylolisthesis, a randomized trial suggested that laminectomy alone is as effective as laminectomy plus fusion,12 although a cohort study suggested an advantage for noninstrumented fusion (fusion without surgical implants).13
In contrast to the results of trials involving patients with spondylolisthesis, there is little evidence to support spinal fusion in association with diskectomy for patients with herniated disks and radiculopathy. Although there have been no randomized trials of lumbar diskectomy plus fusion versus diskectomy alone, comparative cohort studies generally suggest that there is no advantage to adding fusion.14 Randomized trials of cervical diskectomy indicate equally good clinical outcomes with diskectomy alone and with diskectomy plus fusion.15,16 Nonetheless, a growing proportion of cervical disk operations include a fusion procedure.17
Diskogenic pain is perhaps the most controversial indication for performing spinal fusion. Advocates are supported by the results of a recent Swedish randomized trial comparing spinal fusion with nonsurgical care for patients with one- or two-level disk degeneration.18 The nonsurgical group received a broad range of treatments, including physical therapy, electrical nerve stimulation, acupuncture, injections, and cognitive training, according to the individual physician's preference. The surgical group had greater improvement than the nonsurgical group in pain relief, function, depressive symptoms, and return to work. Nonetheless, only 63 percent of the patients in the surgical group considered themselves "much better" or "better."
Critics of the Swedish study note that the magnitude of the benefit from fusion was small: pain and functioning improved by about 30 percent on average, and only one in six patients became free of pain. The trial was not blinded, and the improvements in the surgical group diminished between one and two years of follow-up, suggesting that any benefit may have been temporary. The nonsurgical group was treated with heterogeneous therapies that may not have represented optimal nonsurgical care.
A more recent randomized trial compared spinal fusion with a more standardized rehabilitation approach for patients with diskogenic pain. The rehabilitation approach focused on returning patients to their normal activities, reducing their anxiety about back pain, and promoting exercise. In this trial, surgery offered no advantage in pain relief or functional improvement.19 Thus, there are conflicting results from clinical trials and small benefits at best from spinal fusion among patients with diskogenic pain. A systematic review in 1999 concluded that "there is no acceptable evidence of the efficacy of any form of fusion for degenerative lumbar spondylosis, back pain, or `instability.'"20 Similar doubts have emerged regarding fusion for neck pain presumed to result from degenerative cervical spondylosis.21
Fundamental problems plague the study of spinal fusion, including the lack of definitive methods to confirm a solid fusion, a weak association between solid fusion and pain relief, and the placebo effect of surgery for pain relief.22 Although a solid fusion is somewhat more likely to result in pain relief than fusions that are not solid (pseudarthrosis), many patients with the latter have excellent pain relief, while many who have a solid fusion have poor results.8,23 Furthermore, psychosocial factors are important predictors of the clinical outcome. Factors associated with the outcome in a statewide survey, for example, included income, age, the presence or absence of involvement in litigation, and the presence or absence of depression.24
The Value of Surgical Implants for Spinal Fusion
Surgical implants are used in a growing proportion of fusion operations. In published clinical studies of lumbar fusion, reported rates of internal fixation nearly doubled from the 1980s to the 1990s.25 Perhaps the most popular implants are pedicle screws. Since 1996, intervertebral fusion cages have also gained popularity. Both were introduced without randomized trials or prospective cohort comparisons.
Pedicle screws have now been subjected to several randomized trials, comparing fusion with bone grafting alone to fusion with pedicle screws. These trials consistently showed no clinical advantage for fixation with pedicle screws, although some showed somewhat higher rates of solid fusion.8,23,26,27,28,29,30 A randomized trial suggesting better clinical outcomes with instrumentation removed patients with the worst prognosis (because of severe osteopenia) from the internal-fixation group at the time of surgery, and added them to the bone-graft group.31 The results of some randomized trials and cohort studies suggest superior clinical outcomes without pedicle screws.13,27 In studies comparing fusion with and without pedicle screws, patients in whom pedicle screws were used had a higher likelihood of reoperation,27,28,32,33 a higher rate of nerve injury,28,29,34 greater blood loss,28,29 a longer operative time,28,29 and a higher rate of complications.33
Implants are expensive, adding thousands or tens of thousands of dollars to the cost of each operation. Even if a marginal advantage of fusion with implants is hypothesized, a cost-effectiveness analysis has suggested that laminectomy with an instrumented fusion, as compared with a noninstrumented fusion, would result in an incremental cost-effectiveness ratio of more than $3 million per quality-adjusted year of life.35
Complications and Reoperations
Unlike simple diskectomy or laminectomy, spinal fusion requires decortication of bone and, often, placement of implants; spinal fusion also requires more extensive dissection and longer operative time. Thus, it is not surprising that fusion is associated with more complications than are other types of spinal surgery. Among Medicare patients, in comparison with any operation without fusion, surgery that included fusion was associated with a doubling of the risk of complications, an increase in the rate of blood transfusion by a factor of six, and a doubling of postoperative mortality assessed at six weeks.36 This was true even though patients who had fusions were slightly younger and were less likely to have coexisting conditions than were those who had surgery without fusion.
Common complications include instrument failure, occurring in about 7 percent of cases, and complications at the bone-donor site (usually the iliac crest), including infection and chronic pain.14 Complications at the donor site are reported in about 11 percent of cases. Neural injuries are reported in almost 3 percent of cases, pulmonary embolus in 2 percent, and infections in about 3 percent. Vascular complications are rare but potentially catastrophic.37 Failure to achieve a solid fusion mass, or pseudarthrosis, occurs in about 15 percent of cases in most series.14 Though rare, blindness as a consequence of fusion surgery has been reported, probably due to ischemic injury with intravascular volume shifts and the position of the patient during surgery.38
Reoperation is often considered a poor outcome of spinal surgery, because it suggests ongoing or recurrent back problems. Spinal fusions are sometimes performed after previous back surgery has failed, on the assumption that fusion will be a definitive procedure, obviating the need for further intervention. Ironically, though, the rates of reoperation after spinal fusion surgery may be slightly higher than the rates of reoperation after laminectomy or diskectomy without fusion.39,40 Paradoxically, rates of reoperation are even higher for fusion with the use of internal-fixation devices than for bony fusion alone.27,28,29,32,33
Recommendations
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.
Evidence-based practice for degenerative spine disorders might reserve the use of spinal fusions for spondylolisthesis and only rare cases of disk herniation or spinal stenosis without spondylolisthesis. 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. Patients should be informed that pedicle screws are approved only for spondylolisthesis, fractures, dislocation, deformity, spinal tumors, and pseudarthrosis. Financial incentives should be better aligned with the data on the safety and efficacy of spinal procedures.
Emerging spinal implants such as artificial disks should be approached with caution. The data on the efficacy and safety of these devices have been disappointing to date.41 If ongoing trials suggest results equivalent to those of spinal fusion, it may be faint praise, given the paucity of evidence that spinal fusion is safe and effective for common indications. Similar concerns apply to other new techniques for treating back pain, including electrothermal therapy, analgesic pumps, and implanted spinal stimulators.
The FDA should provide closer scrutiny of spinal implants and their use for unapproved indications. For all new spinal implants and new indications, randomized trials should be required before approval is issued by the FDA. Rigorous postmarketing surveillance for adverse events should become mandatory.
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.18,19 Although the use of sham surgery remains controversial for ethical reasons,42 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.
All opinions and conclusions expressed in this article are those of the authors and do not necessarily reflect the views of the sponsoring organizations.
Supported in part by grants (P60 AR48093 and 5K23 AR48979) from the National Institute of Arthritis and Musculoskeletal and Skin Diseases and by an Investigator Award in Health Policy Research from the Robert Wood Johnson Foundation. The University of Washington has received a gift to support research on spinal disorders from Synthes, a manufacturer of orthopedic devices used in spinal surgery; Drs. Deyo and Mirza report that they are likely to receive support for their research from this gift.
Source Information
From the Departments of Medicine (R.A.D.) and Orthopedic Surgery (S.K.M.) and the Center for Cost and Outcomes Research (R.A.D., S.K.M.), University of Washington, Seattle; and the Department of Orthopedic Surgery, University of Gothenburg, Gothenburg, Sweden (A.N.).
Address reprint requests to Dr. Deyo at 146 N. Canal Street, Suite 300, Seattle, WA 98103.
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