Best Practice & Research Clinical Rheumatology 27 (2013) 673–684

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9

Evidence for surgery in degenerative lumbar spine disorders Wilco C.H. Jacobs a,1, Sidney M. Rubinstein b, 2, Bart Koes c, 3, Maurits W. van Tulder b, d, 4, Wilco C. Peul a, e, * a

Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands Department of Health Sciences, Faculty of Earth and Life Science, VU University, Amsterdam, The Netherlands c Department of General Practice, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands d Department of Epidemiology and Biostatistics, EMGO-Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands e Department of Neurosurgery, Medical Center Haaglanden, The Hague, The Netherlands b

a b s t r a c t Keywords: Low back pain Lumbar disc herniation Spondylolisthesis Spinal stenosis Surgery Sciatica

We aimed to evaluate the available evidence on the effectiveness of surgical interventions for a number of conditions resulting in low back pain (LBP) or spine-related irradiating leg pain. We searched the Cochrane databases and PubMed up to June 2013. We included systematic reviews and randomised controlled trials (RCTs) on degenerative disc disease (DDD), herniated disc, spondylolisthesis and spinal stenosis due to degenerative osteoarthritis. We included comparisons between surgery and conservative care and between different techniques. The quality of the systematic reviews was evaluated using assessment of multiple systematic reviews (AMSTAR). Twenty systematic reviews were included which covered the following diagnoses: disc herniation (n ¼ 9), spondylolisthesis (n ¼ 2), spinal stenosis (n ¼ 3), DDD (n ¼ 4) and combinations (n ¼ 2). For most of the comparisons, no significant and/or clinically relevant differences between interventions were

* Corresponding author. Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands. Tel.: þ31 71 526 2109. E-mail addresses: [email protected] (W.C.H. Jacobs), [email protected] (S.M. Rubinstein), [email protected] (B. Koes), [email protected] (M.W. van Tulder), [email protected] (W.C. Peul). 1 Tel.: þ31 71 526 1490. 2 Tel.: þ31 20 598 2520. 3 Tel.: þ31 10 704 3620. 4 Tel.: þ31 20 598 6587. 1521-6942/$ – see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.berh.2013.09.009

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identified. In general, surgery is only indicated for relief of leg pain in clear indications such as disc herniation, spondylolisthesis or spinal stenosis. Ó 2013 Published by Elsevier Ltd.

Introduction The burden of low back pain (LBP) on patients and society is substantial and it ranks first as the disease with most years lived with disability [2] (see also chapter 1 in this edition). LBP has an estimated point prevalence of 10.2% [3] and a lifetime prevalence of up to 84% [4]. More than 80% of those who suffer from LBP seek medical attention [3]. Most episodes are temporary and resolve without treatment in about 25–58% of patients, even when specific causes, such as herniated discs, are present [6]. LBP is associated with high direct costs of health-care utilisation and indirect costs due to lost productivity [7]. While conservative therapy, including a wait-and-see policy, is the first step in the management of LBP, in the case of persistent pain and a clearly identified pain source, targeted injections or surgical intervention may be indicated. The objective of this overview was to evaluate the available evidence from systematic reviews on the effectiveness of surgical interventions for a number of conditions, including degenerative disc disease (DDD), disc herniation, spondylolisthesis and spinal stenosis resulting in LBP or low backrelated irradiating leg pain and/or paraesthesias. A secondary objective was to determine if the evidence was up to date. Existing evidence for surgical interventions We searched Cochrane databases and PubMed up to June 2013 to identify the available evidence on the effectiveness of surgical interventions for degenerative low back disorders. Systematic reviews and randomised controlled trials (RCTs) were included. We included studies on DDD, herniated disc, spondylolisthesis and spinal stenosis due to degenerative osteoarthritis. We included comparisons of surgery versus conservative care and of different surgical techniques compared to each other (see Methods box).

Box 1

Methods

Search Databases: CDSR, DARE, Pubmed (reviews); CENTRAL, Pubmed (RCTs) Search strategy: sensitive (variations on search strings), specific on study type (Shojania [1] and Pubmed search filters), available on request. Search date: June 2013. Citation tracking of older reviews. Study types: Systematic reviews (comprehensive search, RoB assessment) and RCTs (valid randomisation, English, available). Disorders: lumbar disc herniation with radiculopathy, lumbar spondylolisthesis, lumbar spinal stenosis or degenerative lumbar disc disease. Interventions: Conservative interventions versus surgery or Surgery versus surgery Publication dates: from 2001 (reviews), from 2010 or since last included review (RCTs). Analysis Risk of bias: Amstar (Quality appraisal of Reviews) [5]. Outcomes: Subjective outcome data (pain, functional status, recovery, physiological/objective data (e.g., success of fusion according to clinician)). Analysis: Not pooled, descriptive from presented meta-analyses, complemented with descriptive results from RCTs. Clinical relevance: Ostelo: [8] 15 for 100mm Visual Analogue Scale, 5 for the Roland Disability Questionnaire and 10 for the ODI.

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Table 1 AMSTAR [5] is a measurement tool for assessing the methodological quality of systematic reviews. 1 2 3 4 5 6 7 8 9 10 11

Was an ‘a priori’ design provided? Was there duplicate study selection and data extraction? Was a comprehensive literature search performed? Was the status of publication (i.e. grey literature) used as an inclusion criterion? Was a list of studies (included and excluded) provided? Were the characteristics of the included studies provided? Was the scientific quality of the included studies assessed and documented? Was the scientific quality of the included studies used appropriately in formulating conclusions?. Were the methods used to combine the findings of studies appropriate? Was the likelihood of publication bias assessed? Was the conflict of interest included?

The quality of the systematic reviews was evaluated using AMSTAR by two reviewers independently (Table 1). Twenty systematic reviews on surgical interventions for LBP and/or spine-related leg pain with at least a comprehensive search strategy and a risk of bias assessment were included in this overview (Table 2). The additional search for RCTs yielded 18 studies. About 45% of reviews included observational studies [9–17] and 55% RCTs [18–28]. Two reviews [19,21] included a broad spectrum of low back disorders. The second decade of this century sees more focussed reviews on disc herniation (nine reviews [9,10,14–16,18–20,25,26]), spondylolisthesis (two reviews [11,12]), stenosis (five reviews [13,19,21,24,28]) and DDD (six reviews [17,19,21–23,27]). Table 2 Risk of bias of included systematic reviews. Main Indication

Degenerative disc disease Total disc replacement versus fusion

Thermal Annular Procedures Herniated disc Conservative versus surgical interventions Open discectomy versus MED; MIS techniques Open versus MED with tubular distractors Transforaminal endoscopic surgery Mechanical lumbar disc decompression with nucleoplasty Automated Percutaneous Mechanical Lumbar Discectomy Percutaneous Lumbar Laser Disc Decompression Various Various Spondylolisthesis Fusion versus decompression, conservative Fusion versus decompression Stenosis Surgery versus conservative IPD versus conservative Combinations Various (HD, DDD, stenosis) Various (Spl, DDD, stenosis)

Study

Amstar Item

Author

1

2

3

4

5

6

7

8

9

10

11

High Quality

Eerenbeemt [23] Yajun [22] Jacobs [27] Helm [17]

N N Y N

Y Y Y Y

Y Y Y N

? N N N

Y N Y Y

Y Y Y Y

Y Y Y Y

Y Y Y Y

n/a N Y n/a

N Y Y N

N N Y Y

Y

Jacobs [20] Jacobs [25] Dasenbrock [26] Nellensteijn [10] Manchikanti [15]

N N N N N

Y N N Y Y

Y Y Y Y Y

N N N ? N

N Y Y N Y

Y Y Y Y Y

Y Y Y Y Y

Y Y N Y Y

? Y Y Y n/a

Y Y Y N N

N Y Y N Y

Y Y

Manchikanti [14]

N

Y

Y

N

Y

Y

Y

Y

n/a

N

Y

Y

Singh [16]

N

Y

Y

N

Y

Y

Y

Y

n/a

N

Y

Y

Gibson (HNP) [18] Lewis [9]

Y Y

N Y

Y Y

Y Y

Y N

Y Y

Y Y

Y Y

Y Y

N Y

N N

Y Y

Jacobs [11] Martin [12]

N N

Y N

Y Y

N Y

Y N

Y Y

Y Y

N Y

n/a Y

N N

N N

Y

Kovacs [24] May [28] Moojen [13]

N N N

Y Y Y

Y Y Y

N N ?

Y N Y

Y Y Y

Y Y Y

Y Y Y

Y n/a Y

N N N

Y Y Y

Y Y

Chou [19] Gibson [21]

N Y

N N

Y Y

N Y

Y Y

Y Y

Y Y

Y Y

n/a Y

N N

Y N

Y Y

Y

Y Y

a

Y ¼ Yes, meets requirement, N ¼ No, does not meet requirement, n/a ¼ not applicable, DDD ¼ Degenerative disc disease, HD ¼ Herniated disc, SPL ¼ spondylolisthesis. a Quality was decreased because of inconsistencies in the evaluation.

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Discogenic LBP, without disc herniation or spinal stenosis Six reviews (four of high quality) dealt with discogenic LBP without disc herniation or spinal stenosis in the presence of degenerative changes in the disc [17,19,21–23,27]. Although there is controversy on DDD as a disease entity, we included studies that reported on DDD, excluding structural anatomical abnormalities of discs or vertebral elements. Conservative versus surgical interventions Three reviews [17,19,21] (two of high quality) compared surgery with conservative treatment or sham interventions for discogenic LBP. Gibson and Waddell [21] included three RCTs (141 patients) and Helm et al. [17] included two RCTs (121 patients) on intradiscal electrothermal therapy (IDET) versus placebo surgery. Both reviews could not draw any firm conclusions from these small studies. No additional RCTs on IDET were identified in our search. Chou et al. [19] included four high-quality studies (767 patients) on fusion versus conservative interventions, but no meta-analysis was performed. The results were inconsistent and this was ascribed to differences between the trials in rehabilitation intensity in the non-surgical intervention groups. Fusion surgery was no more effective than intensive rehabilitation in terms of disability, LBP and overall improvement/general health at 1and 2-year follow-up in three studies (473 patients), although fusion was associated with small-tomoderate benefits compared to low-intensity, non-surgical therapy for back pain (Visual Analogue Scale (VAS): 21 versus 4.3 mm) and disability (Oswestry Disability Index, ODI) in one study (294 patients). We identified one additional RCT [29]; although this was a small trial (41 patients), fusion surgery proved to be more effective (VAS pain, presumably LBP, mean difference (MD) 2.8 mm) than standard low-intensity, non-surgical care. In conclusion, the current evidence does not support surgery as an effective treatment with clinically irrelevant improvements in pain scores or function over high-intensity conservative interventions for the treatment of LBP. The place for disc replacement Five reviews [19,21–23,27] (four of high quality) compared the effects of disc replacement with those of spinal fusion for discogenic LBP in the absence of spinal stenosis. The Cochrane review of Jacobs et al. [27] can be regarded as the update of the Cochrane review by Gibson and Waddell [21], who at the time could not draw any firm conclusions due to lack of data. The reviews of Chou et al. [19], van den Eerenbeemt et al. [23] and Yajun et al. [22] included two, three and four randomised studies with 596, 616 and 759 patients, respectively. The most recent review [27] included seven studies and found statistically significant but clinically irrelevant differences between disc replacement and fusion for LBP (5.2 mm VAS, 95% confidence interval (CI) 0.2–20.3) and ODI (4.3, 95% CI 1.85–6.68). We found one additional RCT [30], but this study was a comparison between two disc-replacement devices for registration purposes. The consistent and increasingly reliable conclusion from these reviews is that, at best, disc replacement results in equal success rates as fusion does. There is insufficient evidence on long-term clinical outcome, prevention of adjacent segment degeneration and complications such as implant failure or facet joint degeneration to justify its widespread use. Comparison between different fusion techniques No evidence from systematic reviews was found regarding the clinical effectiveness of different surgical techniques to achieve fusion for discogenic LBP. In our search we identified two additional RCTs [31,32], but in these trials spondylolisthesis, as a structural abnormality, was the major diagnosis. In short, it is doubtful whether any surgical, invasive intervention such as disc replacement or fusion surgery should be carried out in patients without a clear diagnosis of the source of their LBP. In addition, bias introduced by sponsoring cannot be ruled out [33].

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Disc herniation with radiculopathy Ten reviews (nine of high quality) dealt with spine-related irradiating leg pain due to herniated discs [9,10,14–16,18–20,25,26]. For patients with disc herniation there are two main questions to be answered. First, does the patient benefit from surgery, measured by improvement in function, relief of back pain or rather leg pain compared to conservative interventions? Second, which surgical technique provides us with the best outcomes? The choice of surgical technique focusses on the minimal invasiveness of available techniques and the associated risks due to decreased vision and perceived benefits due to less tissue damage. Conservative treatment or surgical interventions? Four high-quality reviews [9,18–20] studied conservative versus surgical treatment for sciatica due to a herniated disc and identified five randomised trials. These reviews are rather recent (2011) and our search did not identify new studies. The 2007 Cochrane review on lumbar disc prolapse by Gibson and Waddell [18] has been updated in a series of more focussed reviews using the same Cochrane methodology. One of these compared conservative care with surgery [20]. This review included one low-riskof-bias study [34], which demonstrated that surgery leads to faster relief of leg pain within 6 months but no difference in LBP relief compared to a strategy of prolonged conservative treatment and delayed surgery in 40% of patients, without differences at 1- or 2-year follow-up. However, another low-risk-ofbias study, with a high crossover rate [35], found no differences based on the intention-to-treat analysis. The per-protocol analysis showed the superiority of surgery. Although the per-protocol analysis might appear less valid the conclusion might have more value, as the intention-to-treat analysis was hampered by large proportions of patients not receiving the allocated treatment. No meta-analysis could be performed due to heterogeneity of studies and difference in methodology. Lewis et al. [9] additionally included nine observational studies on disc surgery versus conservative interventions. Global effect- and condition-specific outcome measures favoured surgery, but did not differ significantly at medium term (6 weeks–6 months) (odds ratio (OR) 1.66, 95% CI 0.98–2.18; MD 0.14 95% CI 0.50 to 0.23, respectively). The main conclusion from these reviews was consistent with the observation that surgery appears to lead to short-term benefits for leg pain, to a lesser extent for LBP and no short-term effect on diseasespecific functioning with similar outcomes at long term. However, there is a caveat. The dearth of highquality studies does not support a definite choice for conservative or surgical treatment for disc herniation with sciatica. In addition, no randomised studies were found that compared surgery to conservative care for herniated discs causing predominantly LBP. No conclusions can be drawn about the beneficial or negative effect of discectomy for patients with a herniated disc and LBP only. Open or Micro(endo)scopic discectomy? Although evidence is lacking, the spinal surgical community considers microscopic discectomy as the golden standard. The comparison between open versus minimally invasive discectomy was summarised in the original Cochrane review [18] and three more focussed reviews on open versus microscopic discectomy [25], microscopic discectomy using tubular distracters [26] and transforaminal endoscopic surgery [10]. Jacobs et al. [25] included eight RCTs that compared open discectomy with microscopic discectomy or microendoscopic discectomy (MED). There was moderate quality evidence that minimal invasive discectomy results in a longer duration of surgery, equal length of hospital stay and a statistically significant but clinically irrelevant lower-leg-pain intensity (2.01 mm, 95% CI 0.57–3.44). Dasenbrock et al. [26] compared minimal invasive discectomies with the use of a tubular retractor. Six RCTs were included in this review that found no differences in operation duration but an increased risk of incidental durotomy for the minimal invasive technique. Short-term differences were not included. The authors concluded that there is no difference in long-term improvement in pain. Nellensteijn et al. [10] included one RCT (60 patients) and seven non-randomised controlled studies (1822 patients) to compare transforaminal endoscopic surgery with open approaches with the disc herniation. No meta-

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analysis was performed because of heterogeneity. The authors concluded that there is still insufficient information to support this technique over open procedures. One additional RCT was identified by our search [36], which included 80 patients and compared microscopic discectomy with MED. The authors found less operative morbidity (surgery duration, blood loss and hospital stay) and a significant difference in ODI at 1 week in favour of MED. In conclusion, none of the studies demonstrated added value of endoscopic approaches over microscopic discectomy for LBP reduction or functional improvement in patients with disc herniation, although one review found a small difference for leg pain. This absence of added value is in contrast to the arguments of less tissue and bone damage, which is used to market and implement these techniques. Minimal invasive alternatives to micro(endo)scopic discectomy The emergence of the concept of a minimal invasive approach has led to the development of several surgical techniques that each in their own way aim to minimise surgical morbidity. These approaches vary in the way the discectomy is performed to decompress the disc, such as percutaneous laser disc decompression (PLDD), automated percutaneous mechanical lumbar discectomy (APLD), sequestrectomy and nucleoplasty or coblation. Jacobs [25] included nine RCTs that compared microscopic discectomy with variations to this approach, such as transmuscular tubular discectomy, percutaneous nucleotomy and sequestrectomy. This review identified only low and very low quality of evidence indicating that there is no difference in most outcomes or even conflicting evidence on pain. The exception was for sequestrectomy, which favoured sensory and motor deficits and overall outcome at 2-year follow-up. No new studies were identified in the search update so that these conclusions remain unchanged. Singh et al. [16] evaluated PLDD and found one retrospective study [37], where PLDD was compared to microscopic discectomy. This study found no differences between microscopic discectomy and PLDD according to the MacNab criteria, but a faster return to work for PLDD. The reviewers concluded that there was no or limited evidence in favour of PLDD, but on the basis of ‘potential medical and economic benefits’ it should not be discarded as experimental or ineffective. However, this means that many patients could be affected if future high-quality studies show serious side effects. Our search for additional trials found one placebo-controlled RCT [38] with 40 LBP patients, which found no differences between intervention and sham surgery. However, this might be an underpowered study. Manchikanti et al. [14] included two comparative studies on APLD, while four randomised studies were excluded because of limited sample size and only a 6-month follow-up. However, as the gain from minimal invasive techniques is believed to occur within the first half-year, these results might have been valuable to use in the evidence. The two comparative retrospective studies showed indeed shortas well as long-term favourable results for APLD. Our search for additional trials did not reveal any new studies, so that the quality of evidence on APLD remains low (which is based upon observational studies with high risk of bias). One review focussed on coblation nucleoplasty [15] and included one RCT and two comparative non-randomised studies. The randomised trial compared nucleoplasty with epidural steroid injections and found nucleoplasty to result in better short-term (6 months) improvement with regard to leg pain (47 versus 21 mm) and ODI (21.0 versus 0.4) with more patients attaining clinically important changes at the long term (2 years). In conclusion, with the exception of one trial which examined the effects of nucleoplasty compared to steroid injections, none of the above techniques showed any benefit by the use of these techniques in comparison with conventional microscopic discectomy. Low-grade isthmic spondylolisthesis (type II) One older review [11] compared surgery with conservative treatment and surgical techniques to one another for low-grade adult isthmic spondylolisthesis with leg pain or LBP, or both. At that time, eight RCTs (376 patients), four observational prospective studies (148 patients) and 17 retrospective case series (648 patients) could be included. Seven randomised studies compared postero-lateral fusion (PLF) techniques to one another. Techniques that were compared included addition of instrumentation such as screws and rods or plates, addition of decompression and addition of anterior

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interbody fusion. Heterogeneity prevented proper meta-analysis. A best evidence synthesis could not reveal a difference in fusion rate at 2 years between instrumented and non-instrumented fusion and its effect on leg pain and LBP. One high-risk-of-bias study [39] showed superior results of overall outcome (74% versus 43% good outcome), and pain index (37 versus 56 mm) at 2 years favouring PLF over exercise. Important methodological considerations, blinding and intention to treat, were rarely used in the studies. The methodological quality of the included RCTs and observational studies was variable and did not allow pooling because of the heterogeneity of the included populations. We found two additional RCTs [40,41] on the comparison between PLF and posterior interbody fusion for isthmic spondylolisthesis that showed conflicting results with regard to LBP at 3–6 months. In addition, one report on the long-term results of an RCT [42] showed that the positive results of PLF were maintained after 11–13 years, but that there were no differences between instrumented and non-instrumented fusion. In conclusion, surgery appears to lead to better improvement in ‘pain index’ (not defined as leg pain or LBP) and clinical outcome compared to conservative treatment, while the different surgical techniques show no differences or conflicting results. The studies were not clear about the percentage of patients with LBP without leg pain and more importantly the effect of surgery for this particular outcome. There is a need for an update of the review on isthmic spondylolisthesis as the existing review is fairly outdated and new evidence exists [40–42]. This is particularly relevant in a time when the economic burden of health care should lead to a critical cost-effectiveness evaluation of implants; therefore, it is important to conduct economic evaluations. Degenerative spondylolisthesis (type III) One high-quality review (Martin et al. [12]), which compared different surgical techniques to one another for degenerative spondylolisthesis, included four RCTs (180 patients) and nine observational studies (405 patients) that compared fusion versus decompression alone and instrumented fusion versus non-instrumented fusion. Spinal fusion was found to lead to a higher probability of improved clinical outcome than decompression with a pooled relative risk (RR) of 1.40 (95% CI 1.04–1.89). Instrumentation led to improved fusion (RR 1.37, 95% CI 1.07–1.75), but this was not related to better clinical outcome (RR 1.19, not significant). No new studies were identified which examined fusion versus decompression or instrumented versus non-instrumented fusion. However, we found three new studies; one study found better recovery of low back- and leg pain with bilateral-instrumented compared to unilateral-instrumented fusion (LBP 1.5 versus 3.4, leg pain 1.3 versus 3.7) [43], one small study found only a difference in fusion rate between two types of cages [44] and one study found no differences between local and iliac crest bone graft [45]. In conclusion, fusion appears to result in better clinical outcomes than decompression, while type of fusion, either instrumented or non-instrumented, cannot be chosen based on current evidence. There is a need for an update of the review on degenerative spondylolisthesis as the existing review is fairly outdated and new evidence [43–45] exists. Degenerative spinal stenosis Five reviews (four of high quality) dealt with degenerative spinal stenosis [13,19,21,24,28]; LBP was excluded in all studies. Conservative versus surgical interventions There are three reviews [19,24,28] (two of high quality) that examined surgery versus conservative treatment for spinal stenosis with symptoms of neurogenic claudication or sciatica. Two reviews [19,24] included the same five randomised studies (918 patients), while May and Somer [28] included two additional studies [46,47]. Kovacs et al. [24] found no difference based on the pooled ODI at 2 years (two studies; MD 1.57, 95% CI 4.65 to 1.51), while all studies individually showed better results for surgery compared to conservative treatment for some of the other outcomes or follow-up moments. Chou et al. [19] did not perform a meta-analysis but concluded that there was good evidence that

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decompressive laminectomy (with or without fusion) is superior to non-surgical therapy for the first 2 years after surgery but that benefits appear to diminish afterwards. The studies included considerable variation in numbers of patients with spondylolisthesis (0–100% or unknown) making the patient sample heterogeneous. Two publications [48,49] included by Chou et al. [19] were regarded to be one study as they reported on a subsample from the included study. We found one update of an included RCT [50], and one study (62 patients) that showed that transforaminal balloon treatment had better VAS leg pain (42 versus 57 mm), ODI (29 versus 39 points), but no differences in LBP, compared to sham treatment [51]. In conclusion, surgery appears to result in better outcomes (leg pain and disability) with regard to conservative interventions, but the evidence is heterogeneous and the underlying methodology is of low quality. Interspinous process devices Three high-quality reviews [13,19,21] specifically addressed interspinous process distraction (IPD) devices in their comparison to conservative treatment. Gibson and Waddell [21] included one RCT, Chou et al. [19] included two RCTs (142 patients) and Moojen et al. [13] additionally included one controlled observational study (60 patients) and seven non-controlled observational studies (391 patients). All three reviews concluded that IPD, both statistically and clinically, significantly improved the Zurich Claudication Questionnaire (ZCQ) total score more than conservative treatment did, although the quality of the evidence was low. The weighted mean difference calculated by Moojen et al. [13] on the ZCQ (mean improvement of symptom severity compared to baseline) was 23.2% (95% CI 18.5–27.8) compared to the pooled baseline score of 5.2 points. This is larger than the minimally detectable change score of 15% reported by Pratt et al. [52], but minimal clinically important differences (MCIDs) for the mean change score are not known. From observational studies, a complication rate of 7% could be calculated. Moojen et al. [13] also concluded that the cost of these techniques is high and more cost-effectiveness research is necessary before worldwide implementation is justified. It should be noted that these reviews include duplicate publications of primary studies. We found no additional studies comparing IPD with conservative interventions. Three additional RCTs were found; one small study (60 patients) found no difference between IPD and screw fixation [53], one study (100 patients) found no differences between IPD and decompression [54] and one study (166 patients) found no differences comparing different models of IPD [55]. In conclusion, IPD appears to result in a better ZCQ outcome compared to conservative interventions, but there is insufficient evidence for the comparison between other surgical interventions. Different surgical approaches for decompression There is only one fairly dated high-quality Cochrane review [21] that deals with different surgical techniques. One included RCT [56] did not identify any difference between laminectomy and multiple laminotomy, but the trial was small and considerable crossover and co-interventions existed. The authors concluded that there was no clear evidence about the most effective decompressive technique or the extent of the decompression. Our search found six additional RCTs [57–62]. Four of these studies (152, 70, 120 and 41 patients) showed significant and clinically relevant differences for LBP [57,59,60,62], leg pain [57,62] or ODI [57] favouring laminotomy over laminectomy, while one study (71 patients) found no differences on these scores [58] and one study (52 patients) found no differences on ODI [61]. In conclusion, it appears that laminotomy or foraminotomy results in a better clinical outcome than laminectomy, but the evidence needs to be evaluated in a systematic review. The role of fusion The aforementioned Cochrane review [21] also dealt with fusion for spinal stenosis. Three included randomised studies (139 patients) were available for comparing additional fusion to decompression

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alone. No difference was found in the surgeon’s rating of outcomes (OR 0.44, 95% CI 0.13–1.15). Other outcomes (re-operation, spondylolisthesis progression and improvement in walking distance) were not significant. A good result at 18–24 months was significant, but very imprecise (OR 4.41 95% CI 1.09– 17.8). One new RCT (53 patients) compared Dynesys with posterior lumbar interbody fusion [63] and found no differences in LBP, leg pain and ODI. In conclusion, no evidence was found indicating that fusion is a useful addition to decompression for spinal stenosis. As the addition of instrumented fusion heightens the risks of perioperative morbidity and mortality [64], one should question if this approach is still justified in older people. Discussion We identified 20 systematic reviews which examined the effectiveness of various surgical interventions for LBP or spine-related radiculopathy due to DDD, disc herniation, isthmic or degenerative spondylolisthesis and spinal stenosis. Most of the reviews that included low back-related disorders were aimed primarily at the treatment of leg pain. For these indications, surgery appears to result in better outcomes in the short term. The exception is DDD in the absence of disc herniation or spinal stenosis where interventions are performed for LBP. No clinical advantage was found for either LBP or leg pain from surgical interventions for these patients. When comparing surgical techniques, there were no statistically significant and clinically relevant differences. The exception might be a better clinical outcome for fusion compared to decompression alone for degenerative spondylolisthesis. We found a sufficient amount of new evidence from RCTs that warrants updating some of the existing evidence from systematic reviews, especially for isthmic and degenerative spondylolisthesis, as well as for comparing surgical techniques for spinal stenosis. It is equally important for systematic reviews as for primary studies that the included indications be well defined. Spinal pathology that causes concordant symptoms should be the starting point for specific interventions. When using symptoms as a starting point, it is required that one knows the underlying pathology before one can decide on the optimal treatment. For example, taking sciatica or neurogenic claudication as a starting point for presenting evidence on treatment efficacy is only useful if the results are presented separately for causes such as disc herniation, spondylolisthesis or nerve root compression in a narrowed foramen, as these pathologies may each predict a different prognosis and/or require different (surgical) interventions. Furthermore, results that are found in any trial, but also in systematic reviews, need to be evaluated against MCIDs between interventions. As these are not available, as an approximation, the values proposed by Ostelo et al. [8] for VAS pain and ODI can be used. The reflection against MCIDs is important as a systematic review/meta-analysis of many studies, and consequently of many participants, may lead to a precise and statistically significant effect estimate, but this effect may not be clinically relevant. On the other hand, systematic reviews with only a few studies, as is often the case in surgery, tend to produce non-significant effects, while the effect may very well be relevant. This is illustrated in our overview where none of the comparisons had >10 RCTs, while most of the RCTs were small, and rarely clinically relevant or statistically significant differences were found. The conclusion of ‘no difference in effect’ could reflect a lack of precision or power, while the difference might be clinically relevant. This should not be misinterpreted for equivalence of interventions, but regarded as ‘insufficient evidence’. On the other hand, an underpowered estimate should by no means be used to justify invasive procedures with their associated surgical morbidity, especially in older people. In general, there is an abundance of reviews on innovative treatments for LBP and radicular pain (IDET, disc replacement and IPD) with relatively few studies. By now, new devices are being brought to the market after comparison with existing Food and Drug Administration (FDA)-approved models that lack sufficient supporting evidence [30]. Evidence-based medicine requires new treatments to be compared to current optimal techniques. However, from the current systematic literature reviews neither fusion nor decompression surgery could be regarded as optimal interventions. Future research should be directed at establishing evidence or consensus for the best current surgical interventions and their relative effectiveness compared to other treatment options. We realise that there may be less interest in repeating previous studies than in studying innovative interventions, that funding for such studies may be difficult to obtain, and that there is a barrier to their publication due to the perceived lack of ‘novelty’.

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However, we suggest that, with increasing health-care costs, ineffective and potentially unsafe innovative interventions for the symptom LBP sec will be more quickly eliminated, improving the opportunities for funding of research into interventions which lead to a clinically relevant effect.

Practice points  Surgery leads to short-term sciatic pain relief for herniated discs compared to conservative treatment; however, there is no difference at the 1-year follow-up.  IPDs lead to superior outcome compared to conservative treatment for spinal stenosis, but cost effectiveness compared to simple decompression should be assessed.  Fusion leads to better clinical outcome compared to decompression for degenerative lumbar spondylolisthesis.  Disc replacement does not lead to a clinically relevant improvement of pain and disability compared to fusion surgery for degenerative disc disease.  As fusion surgery does not lead to better outcomes compared to conservative treatment for patients with LBP sec, one might question if surgery is an appropriate intervention.

Research agenda  The definition of low back disorders needs to be re-established for surgical indications, and needs tailoring towards anatomical diagnoses and complaints with diagnostic and treatment algorithms, which can be differentiated from each other.  The results from an overview of surgical interventions for low back disorders need to be interpreted together with those from an overview of conservative interventions.  Comparisons between different interventions should be investigated in a study including multiple treatment arms, or, alternatively, be addressed in a network meta-analysis.  The reviews on isthmic and degenerative lumbar spondylolisthesis, as well as surgical techniques for spinal stenosis, need to be updated.  The results of trials and systematic reviews need to be evaluated against minimal clinically important differences as assessed by outcome measures [8].

Summary For degenerative low back-related disorders that are accompanied by leg pain, surgical interventions appear to have a better short-term effect on the relief of pain than conservative care. There is no convincing evidence for clinically relevant differences that supports the choice for any of the surgical techniques. The evidence on isthmic and degenerative spondylolisthesis as well as surgical techniques for spinal stenosis should be updated. Evidence from 20 reviews demonstrates that for the treatment of degenerative spine syndromes surgery does not provide relief of LBP. This mainly concerns DDD without disc herniation or spinal stenosis. References [1] Shojania KG, Bero LA. Taking advantage of the explosion of systematic reviews: an efficient MEDLINE search strategy. Effective Clinical Practice 2001;4:157–62. [*2] Vos T, Flaxman AD, Naghavi M, Lozano R, Michaud C, Ezzati M, et al. Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012;380: 2163–96. [3] Freburger JK, Holmes GM, Agans RP, Jackman AM, Darter JD, Wallace AS, et al. The rising prevalence of chronic low back pain. Archives of Internal Medicine 2009;169:251–8.

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