Adam L. Wollowick and Vishal Sarwahi (eds.)Spondylolisthesis10.1007/978-1-4899-7575-1_28

28. Value Considerations in the Surgical Management of Spondylolisthesis

Melissa Esparza¹ and Sigurd H. Berven¹

(1)

Department of Orthopaedic Surgery, UC San Francisco, 500 Parnassus Ave, San Francisco, CA 94143, USA

Melissa Esparza

Email: melissa.esparza@gmail.com

Sigurd H. Berven (Corresponding author)

Email: bervens@orthosurg.ucsf.edu

Keywords

ValueEconomic evaluationCost-utility analysisHealth care spendingTreatment outcomesHealth-related quality of lifeSpine surgeryDegenerative spondylolisthesisIsthmic spondylolisthesisEvidence-based medicine

Introduction

Value-based health care has become an important priority in the health care system in the USA. Value includes a consideration of both quality and cost—the value of a health care intervention is assessed by whether it provides an incremental benefit in outcome to justify an incremental increase in cost. Value considerations are particularly relevant to the management of spine-related conditions as the use of health care resources for the diagnosis and treatment of these conditions is increasing more rapidly than other areas of health care expenditures without a clear improvement of the health of the treated population. High and rising health care expenditures without a corresponding improvement in the health status of the population is an important challenge to sustainability in our health economy. The purpose of this chapter is to describe the role of value considerations in spine-related conditions and to provide a summary of the evidence on value-based care in the management of spondylolisthesis.

Spinal disorders account for a significant proportion of the health care budget in the USA [1–3], contributing an estimated annual direct medical cost of $193.9 billion and an additional $14.0 billion in indirect costs through lost wages in the years 2002–2004 [2]. Martin et al. reported a 65 % increase in health care expenditures for patients with self-reported back and neck problems between 1997 and 2005 with no evidence of a corresponding improvement in self-assessed health status [3].

In addition to high spending, there is also a high degree of variability in the management of common spinal disorders, including spondylolisthesis. Variability is an important factor in value considerations as it affects both quality of care and cost of care. Variability in care pathways is a clear indication of the absence of an evidence-based approach among practitioners. Variability in costs indicates potential for decreasing costs in areas of high spending. Weinstein et al. found a 20-fold variation in the rates of lumbar spinal fusion between geographic regions of the USA between 1992 and 2003 [4]. Highly variable rates of spinal fusion have also been found between hospitals within the same geographic area and between surgeons within the same hospital [5, 6].

The combination of high spending, high variability, and an inconsistent demonstration of benefit in terms of patients’ self-assessed health status raises important questions regarding the value of common interventions in spine surgery and the appropriate rate of spinal surgery [7]. Value-enhancing procedures improve health-related quality of life and reduce cost over time by leading to improved long-term outcomes, a reduction in the need for further medical management, and lower rates of revision surgeries. Two recent systematic reviews of cost-utility analyses in spine care demonstrated the value added by numerous operative interventions in spine care as well as identified some interventions with less favorable cost-effectiveness [8, 9]. Establishing the value of operative and nonoperative interventions in spine care is an important priority in our current health care economy. An evidence-based approach to care is key in the effort to reduce variability and maximize value in health care [10].

An Evidence-Based Approach to the Management of Spondylolisthesis

Spondylolisthesis is a common spinal disorder that significantly impacts patients’ health-related quality of life. Spondylolisthesis encompasses a spectrum of etiologies sharing the common pathology of forward displacement of one vertebra on the subjacent vertebra. Various classification systems have classified spondylolisthesis based on morphology, etiology, and severity [11–14]. This chapter will focus on two of the most common types of spondylolisthesis among adults, degenerative spondylolisthesis and isthmic spondylolisthesis.

The management of spondylolisthesis is characterized by significant variability in both operative and nonoperative treatment. Developing an evidence-based approach to care for spondylolisthesis involves addressing questions of the role of operative and nonoperative care as well as determining the surgical strategies that are most effective. Within the realm of surgery, questions include the role of decompression with or without fusion, the role of instrumentation in spinal fusion, and the role of circumferential arthrodesis compared with posterolateral arthrodesis. The first part of this chapter will review the literature to provide an evidence-based approach for addressing these questions and controversies. An evidence-based approach to care will provide a guide for reducing variability and improving quality of care in the management of spondylolisthesis.

The assessment of value is an important component in establishing an evidence-based approach to the management of spondylolisthesis. Defining the place of surgery for spondylolisthesis in a value-based healthcare economy includes an analysis of whether surgical care is cost-effective compared with alternative treatments and compared with other health care interventions that may compete for limited health care resources. The second part of this chapter will describe methods for value assessment in health care and review the literature for cost-effectiveness and cost-utility analyses of management approaches to spondylolisthesis.

Evidence for the Role of Operative versus Nonoperative Care: Degenerative Spondylolisthesis

Degenerative spondylolisthesis is characterized by the forward slippage of one vertebra on the subadjacent vertebra with the preservation of an intact neural arch [15]. Degeneration of the intervertebral disc and the facet joints permits displacement of the vertebrae with characteristic forward slippage and instability [16]. The natural history of the condition is not completely characterized, and often follows a stable course with slow progression over time, with significant variability between patients [17]. Surgical indications include progressive neural dysfunction related to neural compression. Surgery may also be indicated for patients with the persistence of leg pain, back pain, or neural symptoms despite nonoperative care [18]. Surgery is a discretionary procedure in such cases, and patients may choose to continue with nonoperative care or pursue operative treatment. In making an informed choice about their care, it is important for patients to have access to information on the outcomes of alternative interventions [19].

The Spine Patient Outcomes Research Trial (SPORT) [20] is an important study in assessing the outcomes and cost-effectiveness of different management approaches for three common spinal pathologies—intervertebral disc herniation, spinal stenosis, and degenerative spondylolisthesis. The study is a multicenter, prospective design including patients from 13 institutions in 11 states who were randomized to operative or nonoperative treatment, and a separate cohort of patients who were observed after choosing their care. Primary outcome measures included patient-reported health-related quality of life as measured by the SF-36 Health Status Questionnaire and the oswestry disability index (ODI). Secondary outcomes included preference-based measures of health status to estimate quality-adjusted life years (QALYs) and measures of resource utilization and cost. The SPORT was a pivotal trial in evaluating operative versus nonoperative treatment of three common spinal pathologies, and data from this trial has been used in many subsequent publications.

Using a subset of data from the SPORT, Weinstein et al. reported outcomes of surgical versus nonsurgical treatment for degenerative spondylolisthesis at 2-year follow-up [21] and 4-year follow-up [22]. Prior studies comparing operative and nonoperative care were limited by the inclusion of patients with mixed spinal pathologies, the lack of randomization, and the absence of standardized outcome instruments to assess results of care [23, 24].

The cohort studied by Weinstein et al. included patients diagnosed with degenerative spondylolisthesis who had at least 12 weeks of symptomatic neurogenic claudication or radicular pain with neural symptoms and were candidates for surgical care. Treatment options included lumbar laminectomy with or without fusion or nonoperative treatment, which did not follow a standardized protocol and could include education, physical therapy, injections, and pain medications. Surgeons chose between surgical strategies including laminectomy alone, noninstrumented posterolateral fusion, instrumented posterolateral fusion, and circumferential fusion. The primary outcome measures were patient self-assessments of health-related quality of life, including the SF-36 physical function and bodily pain domains and the ODI.

No significant difference was found in the outcomes of the operative group compared with the nonoperative group in the intent to treat analysis. However, there was a high rate of cross-over in the randomized cohort, with only 66 % of patients assigned to surgery undergoing operative care, and 54 % of patients assigned to nonoperative care undergoing surgery at 4-year follow-up. The as-treated analysis with careful control for confounding variables provides a more accurate assessment of the outcomes of care. An analysis of the randomized and observational cohorts combined demonstrated significant differences in favor of surgery for all the primary and secondary outcomes. The effect size favoring surgery was clinically significant with a difference of 15.3 points for bodily pain, 18.9 points for physical function, and 14.3 points for ODI.

Weinstein et al. provide the highest quality analysis of operative versus nonoperative care for degenerative spondylolisthesis; however, the study also has significant limitations. The high cross-over rate between study groups compromises the validity of the intent to treat analysis. Despite controlling for potential confounders in the as-treated analysis, the surgically treated group demonstrated a higher degree of disease severity with measurably more body pain, functional limitations, and disability at baseline than the patients treated nonoperatively. Another limitation of conclusions drawn from the as-treated analysis is that the demonstrated benefit of surgery may be related to patient preference for surgical intervention. Further studies that control for patient preference or include a placebo-controlled group may be useful in isolating the effect of surgery on clinical outcomes. Nonoperative management was consistent with the standard of care based on published guidelines, however lacked a standardized protocol of care. Further research on more clearly defined nonoperative protocols may be useful in demonstrating the value of specific nonoperative treatment modalities.

Evidence for the Role of Operative versus Nonoperative Care: Isthmic Spondylolisthesis

Isthmic spondylolisthesis is defined by the forward slippage of one vertebrae on the subadjacent vertebrae secondary to a defect in the pars interarticularis, which can arise from a stress fracture, an acute fracture, or elongation of the pars interarticularis [25]. In a long-term prospective study of the natural history of isthmic spondylolisthesis, Fredrickson et al. described a low rate of slip progression and clinical outcomes comparable to the general population of patients with isthmic spondylolisthesis at 45-year follow-up [26, 27]. Indications for surgery in adults with isthmic spondylolisthesis include high-grade slips, neural dysfunction, and the persistence of lower back pain or radicular pain after appropriate nonoperative care [28].

Several studies have compared conservative and operative treatment in the management of adult isthmic spondylolisthesis. Moller and Hedlund randomized 111 patients to posterolateral arthrodesis or an exercise program for the treatment of isthmic spondylolisthesis [29]. They found that patients treated with surgical arthrodesis had significantly improved functional outcomes and reduced pain compared with the nonoperatively treated patients. Limitations of the study include that nonoperative treatment was limited to a single exercise program, and outcomes were measured with a Visual Analogue Scale that does not provide a standardized measure of health-related quality of life that can be compared across studies.

L’Heureux et al. investigated the outcomes of surgical arthrodesis for the management of isthmic spondylolisthesis in a cohort of 31 adult patients [30]. Patients completed SF-36 questionnaires preoperatively and at 2-year follow-up and were asked additional satisfaction questions at follow-up. Patients demonstrated significant functional improvement and decreased pain rates at 2 years compared with preoperative scores. This study was useful in demonstrating that surgical arthrodesis is an appropriate management approach for patients with isthmic spondylolisthesis; however, it has significant limitations. The cohort consisted of only 31 patients and did not include a control group of patients treated nonoperatively that would allow for a comparison of nonoperative and operative treatment approaches. A range of operative techniques were used including circumferential arthrodesis and posterior only fusion, and both instrumented and noninstrumented fusions.

Overall, the literature supports operative management of adult isthmic spondylolisthesis for patients who have continued pain and functional disability after appropriate nonoperative management. Further investigation is necessary to guide specific surgical techniques for isthmic spondylolisthesis.

Evidence for Specific Surgical Strategies in the Management of Spondylolisthesis

The operative management of spondylolisthesis is variable and the effectiveness of different surgical techniques may be different based on etiology of the spondylolisthesis, severity of slippage, and patient factors. Current questions and controversies in the operative management of spondylolisthesis include the role for decompression, fusion, instrumentation, and circumferential fusion. Decision making in the use of these surgical strategies may be guided by an evidence-based approach to care.

Decompression and Fusion

Operative management of degenerative spondylolisthesis may consist of decompression alone or decompression with spinal fusion. Decompressive laminectomy alone has been shown to result in satisfactory outcomes. A meta-analysis by Mardjetko et al. identified eleven papers published between 1970 and 1993 that reported outcomes for 216 patients undergoing decompression without fusion for degenerative spondylolisthesis [31]. Sixty nine percent of patients had a satisfactory outcome and 31 % had unsatisfactory outcomes. Martin et al. performed a systematic review of the literature and identified eight studies between 1966 and 2005 comparing decompression alone to decompression and fusion [32]. The authors concluded that a satisfactory clinical outcome was more likely with fusion than with decompression alone, with a relative risk of 1.4, and a 95 % confidence interval (CI) of 1.04–1.89.

The highest quality evidence from the Martin et al review was a study by Herkowitz and Kurz of 50 consecutive patients with symptomatic degenerative spondylolisthesis randomized to decompression alone or to decompression with noninstrumented fusion [33]. Outcomes were rated as excellent, good, fair, and poor, based upon clinical improvement, patient activity tolerance, and medication usage. Compared to patients undergoing decompression alone, patients who underwent decompression and fusion had significantly less back and lower limb pain and were more likely to have outcomes rated as good or excellent. The degree of forward slippage increased in 24 of the 25 patients without fusion, and in only 7 of the 25 patients with fusion. Pseudarthrosis was present in 36 % of patients in the arthrodesis group, but 23 of the 25 arthrodesis patients had a complete union on at least one side. There were several limitations to this study. The outcomes measured represented surgeons’ assessment of results and did not include any patient-reported outcomes on health-related quality of life. Decompressive technique in this study involved a midline decompression including the interspinous ligament and one half of the cephalad and caudad laminae of the involved vertebrae, together with medial caudad and cephalad facetectomy. More recent papers have included the study of minimally invasive surgery techniques that involve limited foraminotomies and spare midline spinal anatomy [34–36]. In an economic analysis of decompression with or without fusion, Kim et al. report on outcomes in the literature demonstrating that less-invasive decompressive techniques have good efficacy in certain subsets of patients with degenerative spondylolisthesis, although note that many of these studies also include patients with spinal stenosis without spondylolisthesis [36].

The management of isthmic spondylolisthesis may include decompression with fusion or fusion alone. Agabegi and Fischgrund performed a review of the literature in 2010 to describe current treatment strategies for isthmic spondylolisthesis [28]. The authors cite studies demonstrating lower rates of fusion for patients undergoing decompression and fusion compared with fusion alone for low-grade spondylolisthesis, but another study reporting only 57 % of adult patients with complete pain relief after undergoing fusion without decompression. Based on the literature, they recommend fusion with decompression for adult patients with radicular symptoms or neurologic deficits and evidence of compression of the neural elements.

Instrumentation

The systematic review by Martin et al. identified six studies comparing instrumented fusion to noninstrumented fusion [32]. The authors found no statistically significant difference in the relative risk of achieving a satisfactory clinical outcome for instrumented spinal fusion compared with the noninstrumented group, reporting a relative risk of 1.19 and a 95 % CI that spans one (0.92–1.54). However this study was limited by the inclusion of patients with as little as 1 year follow-up, cohorts as small as five patients per treatment group, and the inclusion of observational study designs. All of the effect sizes were larger in the randomized studies than in the observational studies. The highest quality study from this systematic review that assesses the effect of a solid fusion on long-term outcomes is the paper by Kornblum et al. [37].

Kornblum et al. performed a secondary analysis of patients randomized to noninstrumented posterolateral arthrodesis in two previous prospective, randomized clinical trials [37]. The 58 patients identified had a mean follow-up of 7.7 years (range 5–14 years). Outcomes measured included rating of excellent, good, fair, and poor based on pain relief and activity level. Pseudarthrosis, assessed by plain films at 2–4 year follow-up, developed in 25 of the 47 patients treated with a noninstrumented fusion. Compared to patients with a solid fusion, patients with incomplete union reported significantly worse pain and physical function and were observed to have significantly more segmental dynamic instability. This paper demonstrates improved outcomes for patients with solid fusion compared to those with an incomplete union at a minimum follow-up of 5 years; however, it does not assess the direct effect of instrumentation on fusion rates or clinical outcomes.

Agabegi and Fischgrund note that instrumented posterolateral fusion is the most common surgical technique for adult isthmic spondylolisthesis [28]. However they cite conflicting evidence in the literature for the role of instrumentation in low-grade spondylolisthesis, with four randomized trials showing no added benefit from instrumentation, and other studies demonstrating higher fusion rates and improved outcomes. For high-grade isthmic spondylolisthesis, the authors recommend instrumentation for posterolateral fusion from L4 to S1, and iliac screw fixation for severe slips or unstable cases. The role of instrumentation in adults with isthmic spondylolisthesis has a greater effect size than instrumentation in pediatric populations.

Circumferential Fusion

Definitive evidence for the role of circumferential arthrodesis in the management of both degenerative and isthmic spondylolisthesis is lacking. Videbaek et al. demonstrated significant improvement of clinical outcomes and fusion rates in patients with severe chronic low back pain undergoing circumferential fusion compared with posterolateral only fusion at 5- to 9-year follow-up [38]. In contrast, a study by Fritzell et al demonstrated no statistically significant difference in clinical outcomes between patients treated with circumferential arthrodesis compared with posterolateral fusion but a significantly higher rate of complications in the circumferential fusion group [39]. It must be noted that the cohorts in both the Videbaek et al. and Fritzell et al. consisted of patients with chronic low back pain with diagnoses that could include isthmic spondylolisthesis, degenerative spondylolisthesis, or other degenerative conditions of the spine. Agabegi and Fischgrund reviewed several additional studies of the role of circumferential fusion and concluded that anterior column support in addition to posterolateral fusion may be considered for patients with risk factors for pseudarthrosis and possibly for patients with large or hypermobile discs with low-grade isthmic spondylolisthesis. They advocate for circumferential fusion for high-grade isthmic spondylolisthesis in order to provide greater stability and increase fusion rates [28].

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