Degenerative Disc Disease:To Fuse or Not To Fuse?

Guest Discussants: 

Case Presentation
A 60-year-old healthy man presents with an L4 on L5 Grade I degenerative spondylolisthesis that does not move on flexion/ extension radiographs. Disc degeneration with central stensosis is evident at that level. He describes minimal back pain but neurogenic claudication refractory to conservative management.

 How would you treat this patient?


Figure 1. AP radiograph of lumbar spine.


Figure 2A. Lateral flexion view of lumbar spine.



Figure 2B. Lateral extension view of lumbar spine.

Figure 3. Sagittal MRI of the lumbar spine.

Figure 4. Axial MRI of the lumbar spine at the L4-5 level.

 

Alpesh A. Patel, MD, Responds
The patient history and symptoms are consistent with a diagnosis of spinal stenosis. Additionally, plain radiographs and MRI demonstrate spondylolisthesis of L4 on L5 with central and lateral recess stenosis with the potential for foraminal stenosis. Given the prevalence of asymptomatic radiographic and MRI abnormalities, the correlation of symptoms with imaging findings is critical to medical decision-making. Additionally, other sources of leg pain, such as peripheral vascular disease, should be addressed. For the purpose of this discussion, we assume that this patient has no other sources of pain and has failed conservative treatment including physical therapy, oral  medications and epidural or selective nerve root injections, and is a medically healthy surgical candidate.

Surgical management of patients with spinal stenosis is based on the principal of neurological decompression. Surgical decompression has most commonly been reported through lumbar laminectomy as well as partial medial facetectomy and lateral recess decompression. Surgical decompression for spinal stenosis has been shown, in level I studies, to provide pain relief and functional improvement.1 Additional surgical treatment for spinal stenosis has been reported including arthrodesis, dynamic stabilization or interspinous devices. Little to no convincing data exist on the latter two choices. Spinal fusion for degenerative lumbar spondylolisthesis is well described and, clearly, is a better option for treatment than decompression alone.

Before determining the optimal surgical technique, however, we must clearly understand the patient’s diagnosis. Radiographic imaging classifies this, by morphology, as an acquired, degenerative spondylolisthesis and, by Meyerding grade, a Grade I (0-25%) anterolisthesis. Flexion and extension radiographs are commonly used to quantify segmental movement, either in millimeters of motion or degrees of angulation, and thereby identify spinal instability. Proponents for decompression-only surgery typically use terms of “stable” and “unstable” spondylolisthesis. Unfortunately, there are no validated standards for motion or angulation and no correlation with symptoms or outcomes has been reported. At best, further classification of spondylolisthesis is anecdotal. Therefore, motion on flexion and extension radiographs should not greatly influence surgical decision-making; instead, the patient’s symptoms and diagnosis—in this case Grade I degenerative spondylolisthesis—should be guiding factors.

Surgical decompression in the setting of degenerative spondylolisthesis has shown equivalent results to decompression and fusion in some short-term follow-up studies. Lombardi et al 2 reported results for surgical decompression only in patients with degenerative spondylolisthesis. The authors demonstrated 33% good-to-excellent outcomes in patients with wide decompression (total facetectomy), 80% of patients with facet preservation, and 90% of patients with concomitant posterolateral arthrodesis, suggesting that a limited decompression may be a good option in the treatment of degenerative spondylolisthesis.More widely quoted, Fischgrund et al,3 in a prospective randomized study of 68 patients, demonstrated no statistical differences in outcomes or patient satisfaction at two-year follow-up of patients with a successful union compared to those with a pseudarthrosis. Herkowitz and Kurz3 also reported no differences in outcomes between patients with successful arthrodesis and pseudarthrosis in a prospective randomized study of 50 patients. These papers have been used to suggest that the addition of spinal arthrodesis to surgical decompression will not influence outcomes.

The small number of patients, as well as short-term followup, limit the conclusions available from the these two papers. In fact, in a longer-term follow-up of a group of the same patients described by Herkowitz and Kurz, and Fischgrund et al, Kornblum et al4 demonstrated that a successful arthrodesis resulted in better pain relief and improved functional status. This suggests that the optimal effects of spinal arthrodesis might not be seen for many years after treatment. Other groups have also reported improved outcomes in patients undergoing decompression with spinal arthrodesis. Bridwell et al,5 in a prospective study of 49 patients, documented improved functional status (walking ability) in patients undergoing decompression and instrumented fusion. In a meta-analysis, Mardjetko et al6 reported greater patient satisfaction after decompression and arthrodesis (86% to 90%) compared to decompression only (69%).

Perhaps most convincing, the SPORT trial has recently reported outcomes after surgical treatment of degenerative
spondylolisthesis in a prospective study.7 Surgical treatment was dominated by decompression and arthrodesis (352/372 patients) with only20 patients undergoing decompression only. Surgical results were statistically better than conservative treatment at two-year follow-up. This SPORT study demonstrated safety and efficacy of surgical management of degenerative spondylolisthesis. So few patients were treated with decompression only that insufficient numbers exist to compare the two treatment options. The preponderance of decompression and  arthrodesis at all 13 surgical centers confirms its success and safety, and confirms its widespread acceptance as a preferred treatment option for lumbar degenerative spondylolisthesis.

While the results of surgical decompression and fusion are well established and reported to be better than decompression alone, the complication profile of each surgical option must also be considered. Certainly, intraoperative blood loss, operative time and hospital stay may be greater when including an arthrodesis. Lumbar arthrodesis may result in a pseudarthrosis, though the use of instrumentation has been shown to decrease this risk.4,5 Complications from instrumentation misplacement have also been reported in lumbar arthrodeses. To the contrary, however, the SPORT study reported only a small number of fusion-related complications, pseudarthrosis in 3/352 patients, and no instrumentation–related adverse events.7

The unique complication of decompression-only surgery is the potential for postoperative spinal instability with slip
progression and/or recurrent stenosis.5 The SPORT study reported 10 cases of either recurrent stenosis or slip progression, presumably in the nonfusion patients.7 Although the prevalence of postoperative slip progression and recurrent stenosis remains unknown, these complications may account for the poor reported outcomes of decompression–only surgery.5 The comparatively poorer results and greater complication profile of revision lumbar surgery may further worsen the situation for patients treated with decompression only.

Cost-effectiveness is a commonly voiced concern. Advocates of decompression only would argue that the costs associated with arthrodesis have yet to yield improved outcomes.8,9 Little data exist to support or refute this and arguments are frequently based on the expense of spinal instrumentation. What has been reported is based only on short-term follow-up.9 Longer followup would detect cases of recurrent stenosis, slip progression and
revision surgery; the additional costs associated with treating these conditions can be staggering. In addition, implant costs have become negotiable through surgeon and hospital cooperation. This may alter cost-benefit analyses that have been based on traditional pricing models.

Given the good to excellent outcomes and low complication profile, the evidence better supports a posterior decompression and arthrodesis rather than decompression alone. Certainly controversy exists as to the extent of decompression (eg, laminectomy compared to laminotomy) and its effect on recurrence or slip progression. Until convincing comparative data are available, however, we cannot assume a difference. This patient, if treated
with decompression only, is at risk for recurrent stenosis, slip progression, pain, disability and the need for revision surgery with its concomitant risks and poor outcomes. He is much better off with a posterior decompression and arthrodesis.


References
1. Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med. 2008;358(8): 794-810.

2. Lombardi JS, Wiltse LL, Reynolds J, Widell EH, Spencer C III. Treatment of degenerative spondylolisthesis. Spine. 1985;10(9):821-827.

3. 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 and without spinal instrumentation. Spine. 1997;22(24):2807-2812.

4. 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(6): 802-808.

5. Kornblum MB, Fischgurnd JS, Kerkowitz HN, Abraham DA, Berkower DL, Ditkoff JS. Degenerative lumbar  spondylolisthesis with spinal stenosis: a prospective long-term study comparing fusion and pseudarthrosis. Spine. 2004;29(7):726-33; discussion 733-734.

6. Bridwell KH, Sedgewick TA, O’Brien MF, Lenke LG, Baldus C. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord. 1993;6(6):461-472.

7. Mardjetko SM, Connolly PF, Shott S. Degenerative lumbar spondylolisthesis: a meta-analysis of literature 1970-1993. Spine. 1994;19(20 Suppl):2256S-2265S.

8. Weinstein JN, Lurie JD, Tosteson TD, et al. Surgical versus nonsurgical treatment for lumbar degenerative spondylolisthesis. N Engl J Med. 2007;356(22): 2257-2270.

9. Kuntz KM, Snider RK, Weinstein JN, Pope MH, Katz JN. Costeffectiveness of fusion with and without instrumentation for patients with degenerative spondylolisthesis and spinal stenosis. Spine. 2000;25(9):1132-1139.

10. Tosteson AN, Lurie JD, Tosteson TD, et al. Surgical treatment of spinal stenosis with and without degenerative spondylolisthesis: cost-effectiveness after 2 years. Ann Intern Med. 2008;149(12):845-853.

Peter G. Whang, MD, Responds
This case involves a healthy 60-year-old man who presumably complains of bilateral lower extremity pain and numbness consistent with neurogenic claudication. The patient’s plain X-ray images reveal a mild degenerative scoliosis and moderate disc space narrowing at L4-5 in conjunction with a Grade I spondylolisthesis which appears to be stable on flexion/extension views. The accompanying MR images demonstrate moderate to severe compression of the thecal sac and nerve roots at that level secondary to facet arthropathy, hypertrophy of the ligamentum flavum and a posterior-based disc/osteophyte complex. Although other conditions may give rise to a similar clinical picture (eg, vascular insufficiency), it is assumed that the history and physical examination findings correspond with the diagnosis of spinal stenosis. Despite the existence of several potential pain generators evident on his radiographic studies, this patient is reportedly experiencing minimal discomfort in his lower back. Because he has apparently failed multiple conservative modalities for his neurogenic claudication, he is interested in surgical intervention at this time.

While other operative strategies for addressing lumbar stenosis have been advocated in recent years (ie, interspinous spacers), the gold standard technique for treating this pathology remains a formal decompression of the spinal canal which is typically accomplished by performing a laminectomy. In general, a simple decompression may be reliably expected to relieve claudicatory symptoms and this procedure has consistently been shown to yield excellent clinical and functional outcomes.1 Nevertheless, distinct subsets of patients with lumbar stenosis may also benefit from a concomitant fusion. In particular, an adjunctive arthrodesis may be reasonable to consider for individuals who  have undergone a previous laminectomy at the same levels as well as those with significant preexisting deformity or hypermobility in either the coronal or sagittal planes. In these situations, it has been suggested that stabilizing the spinal column serves to reduce the incidence of postoperative instability which may manifest as recurrent claudication or worsening low back pain. Although this rationale is widely accepted among spine surgeons, it should be noted that no level I data derived from prospective, randomized, controlled clinical trials have validated the utility of a simultaneous decompression and fusion for this specific indication.2,3

One of the most critical factors that will undoubtedly influence the success of decompression for lumbar stenosis is the presence of any clinical or radiographic evidence of preoperative instability. Unfortunately, the task of deciding whether a fusion should also be included is complicated by the lack of a clear consensus regarding the exact criteria that may be used to determine what constitutes “spinal instability.” Given the continuing ambiguity surrounding this ill-defined concept, depending on one’s perspective, this term is just as likely to encompass a mild scoliotic curvature or a stable spondylolisthesis as it is to describe a severe multiplanar deformity or a high-grade slip. However, most surgeons would agree that all cases of “instability” are not created equal and that iatrogenic disruption of the spinal
column is less frequently observed in patients with more benign structural abnormalities. Thus, every effort should be made to accurately assess the biomechanical integrity of the spine in order to estimate the subsequent risk for postoperative instability. First of all, the individual in this vignette is not experiencing any axial back pain which routinely occurs in association with pathologic motion of the spine. Furthermore, aside from a fixed Grade I spondylolisthesis at L4-L5, there are no apparent signs on the plain radiographs or MR images of frank, or even subtle, segmental instability such as hypermobility with flexion/extension, a relatively tall disc or substantial fluid collections in the
zygapophysial joints at the diseased level.4 Thus, with proper adherence to operative technique, I believe it is certainly feasible to achieve a satisfactory decompression of the spine without compromising its overall stability which would preclude the need to perform a supplementary arthrodesis in this patient.

Because of the myriad variables that contribute to the maintenance of spinal stability, it is difficult to quantify the probability that a progressive deformity will arise following a lumbar decompression with any degree of precision. While in the vast majority of instances, a judicious laminectomy that does not violate the facet joints or the pars interarticularis will rarely bring about postoperative instability, a variety of different surgical approaches has been introduced in an attempt to further minimize the amount of bony resection that is required to decompress the neural elements adequately. Partial laminectomies, interlaminar fenestration, spinous process osteotomies, and  laminoplasty are all interventions that permit a thorough decompression of the central canal, lateral recesses and foramina without disrupting the posterior osteoligamentous arch. The safety and efficacy of limited access decompressive procedures have already been established by several clinical investigations. For instance, favorable
long-term (> five years) outcomes have been reported with the use of expansive lumbar laminoplasty as an alternative
to laminectomy.5 According to one prospective study involving 53 subjects with Grade I degenerative  pondylolisthesis and spinal stenosis, this method was shown to be equivalent to a traditional decompression and instrumented fusion.6 Interlaminar fenestration entails the excision of stenotic lesions through multiple laminotomies. With the application of microendoscopic or minimally invasive technology, this operation may afford a comparable decompression with even less dissection of the paraspinal musculature and other stabilizing structures of the
spine. This technique was successfully employed in a series of patients with degenerative spondylolisthesis, none of whom exhibited increased subluxation on postoperative flexion/extension X-ray images. 7 Another viable option for individuals with mild instability is to combine a spinal decompression with innovative motion-sparing devices such as pedicle screw-based “soft stabilization” implants which, in principle, may prevent the development of iatrogenic deformities while avoiding many of the detrimental consequences of a conventional fusion.

Many surgeons may elect to proceed with a prophylactic arthrodesis rather than contend with the challenges inherent
to a failed decompression—revision exposure, loss of bony landmarks, epidural scarring and more severe deformities. Few would argue that the best treatment for iatrogenic instability is prevention but whether this concern justifies adding an unnecessary fusion is controversial. Regardless, advancements in minimally invasive systems which allow for the insertion of percutaneous pedicle screws and interbody spacers through tubular retractors have now made it possible to overcome many of the difficulties associated with these types of cases. As the prospect of reoperating on these individuals becomes less intimidating, surgeons may be more willing to simply perform a decompression which would effectively raise their threshold for incorporating an arthrodesis.

It is obvious from both the steady rise in fusion cases completed each year, as well as the striking variation in utilization rates among different geographical regions, that the acceptable indications for an arthrodesis remain a matter of considerable debate.8 We are all exceedingly aware of the potentially detrimental sequelae of fusions that have been well-documented in the literature: prolonged operating room times and greater blood loss, impairment of the surrounding soft tissues, bone grafting morbidity, hardware complications, pseudarthrosis and adjacent segment degeneration to name a few. When informed of the hazards inherent to an arthrodesis as well as the relatively low incidence of postoperative instability requiring subsequent stabilization of the spine, it is anticipated that most knowledgeable patients would be comfortable with the idea of undergoing a decompression without an attendant fusion.

In this environment where even more emphasis is being placed on the delivery of cost-effective health care, the exorbitant costs incurred by arthrodesis procedures have cast spine surgeons in an extremely unsympathetic light and have garnered significant negative media coverage.9 Until a sufficient amount of Class I data compiled from suitably designed prospective, randomized, controlled clinical trials becomes available, it would seem to be prudent for us to err on the side of caution and refrain from fusing a patient like this with symptomatic spinal stenosis and a stable degenerative spondylolisthesis.

References
1. Resnick DK, Choudhri TF, Dailey AT, et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 10: fusion following decompression in patients with stenosis without spondylolisthesis. J Neurosurg Spine. 2005;2:686-691.

2. Resnick DK, Choudhri TF, Dailey AT, et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 9: fusion following decompression in patients with stenosis and spondylolisthesis. J Neurosurg Spine. 2005;2:679-685.

3. Waters RC 3rd, Baisden J, Gilbert TJ, et al. Degenerative lumbar spinal stenosis: an evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis. Spine J. 2008;8:305-310.

4. Schinnerer KA, Katz LD, Grauer JN. MR findings of exaggerated fluid in facet joints predicts instability. J Spinal Disord Tech. 2008;21:468-472.

5. Kawaguchi Y, Kanamori, M, Ishihara H, et al. Clinical and radiographic results of expansive lumbar laminoplasty in paitents with spinal stenosis. J Bone Joint Surg Am. 2004;86:1698-1703.

6. Matsudaira K, Yamazaki T, Seichi A, et al. Spinal stenosis in grade I degenerative lumbar spondylolisthesis: a comparative study of outcomes following laminoplasty and laminectomy with instrumented spinal fusion. J Orthop Sci. 2005;10:270-276.

7. Palmer S, Turner R, Palmer R. Bilateral decompression of lumbar spinal stenosis involving a unilateral approach with microscope and tubular retractor system. J Neurosurg. 2002;97:213-217.

8. Weinstein JN, Lurie JD, Olson PR, et al. United States’ trends and regional variations in lumbar spine surgery. Spine. 2006;31:2707-2714.

9. Whang PG, Lim MR, Sasso RC, et al. Financial incentives for lumbar surgery: a critical analysis of physician reimbursement for decompression and fusion procedures. J Spinal Disord Tech. 2008;21:381-386.

Author Disclosures

• A Patel. Speaking/Teaching Arrangments: Stryker, Amedica, Level B.
• P Whang. Stock Ownership: DiFusion, 15%. Consulting: Aesculap, Level B; Apatech, Level C. Trips/Travel Reimbursement: Stryker, Level B. Scientific Advisory Board: DiFusion, Nonfinancial. Other Office: Paradigm Spine, Level C.
• J Wang. Royalties: Aesculap, Depuy, Level B; Medtronic, Osprey, Level D; Seaspine, Stryker, Level E; Biomet, Level F. Private Investments: Fund including < 1% each of Promethean Spine, Paradigm Spine, Benevenue, NexGen, K2 Medical, Pioneer, Amedica, Vertiflex. Consulting: Medtronic, Level A; Fziomed (discontinued), MTF,
  Facet Solutions, Depuy Spine, Level B; Lanx, Level F (agreement now expired; future royalties possible); Speaking/Teaching Arrangements: SeaSpine, Vertiflex, Level B; Stryker, Level D. Trips/Travel: Depuy, Stryker, Level B travel reimbursement. Scientific Advisory Board: VG Innovations Financial, Corespine Financial,  Expanding Orthopaedics Financial, Syndicom Financial, Osprey Financial, Flexuspine Financial, Amedica Financial, Bone Biologics Financial.
  
  

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