REVIEW ARTICLE The clinical course of pain and disability following surgery for spinal stenosis: a systematic review and meta-analysis of cohort studies Carolina G. Fritsch1,2 • Manuela L. Ferreira3,4 • Christopher G. Maher3 • Robert D. Herbert5 • Rafael Z. Pinto6 • Bart Koes7 • Paulo H. Ferreira1 Received: 18 February 2016 / Revised: 12 June 2016 / Accepted: 16 June 2016 / Published online: 21 July 2016 � Springer-Verlag Berlin Heidelberg 2016 Abstract Purpose The aim of this study was to assess the clinical course of pain and disability in patients with lumbar spinal stenosis following surgery. Methods Electronic databases were searched to July 2014 and only prospective cohort studies assessing pain or dis- ability following surgery for lumbar spinal stenosis were included. Two independent reviewers extracted data and assessed study quality. Estimates of pain and disability (expressed as 0–100 point scales) as well as 95 % confidence intervals were obtained using meta-regression. The effect of time was clearly non-linear, so it was mod- elled using fractional polynomial regression. Results From a total of 10,741 titles, 69 publications (64 cohort studies) were included in the review. Pooled esti- mate for pain pre-operatively was 63.4 (95 % CI 56.5; 70.3), reducing to 33.1 (95 % CI 24.2; 41.9) at 3 months and 19.2 points (95 % CI 9.2; 29.3) at 60 months. Pre- operative estimates of disability were 36.9 (95 % CI 32.6; 41.3), reducing to 16.3 (95 % CI 11.8; 20.9) at 3 months and 12.4 (95 % CI 7.7; 17.2) at 60 months. Conclusion Patients with lumbar spinal stenosis experi- ence rapid symptom reduction after surgery, but should still expect to experience mild-to-moderate pain and disability 60 months later. Keywords Lumbar spinal stenosis � Meta-analysis � Prognosis � Surgery Background Lumbar spinal stenosis is a well recognised and severely debilitating spinal condition. It is generally attributed to a narrowing of the spinal canal, nerve root canals, or inter- vertebral foramina, usually as a consequence of age-related degenerative changes to the spine anatomy, including bone, ligaments, facet joints, and intervertebral disc. Clinical symptoms are believed to result from compression and/or ischaemia of vascular and neurological tissues in the spine. Neurogenic claudication is the most typical symptom, and may be accompanied by lower limb pain, numbness, paraesthesia, or weakness, usually exacerbated by standing or walking [1, 2]. The available literature on the subject highlights that symptoms are exacerbated by extended Systematic review registration: PROSPERO 2013: CRD42013005988. Electronic supplementary material The online version of this article (doi:10.1007/s00586-016-4668-0) contains supplementary material, which is available to authorized users. & Carolina G. Fritsch carolinafritsch@gmail.com 1 Discipline of Physiotherapy, Faculty Health Sciences, The University of Sydney, Sydney, Australia 2 Departamento de Fisioterapia, Universidade Federal de Ciências da Saúde de Porto Alegre, R. Sarmento Leite 245, Porto Alegre, Brazil 3 The George Institute for Global Health, Sydney Medical School, University of Sydney, Sydney, Australia 4 The Institute of Bone and Joint Research, Sydney Medical School, University of Sydney, Sydney, Australia 5 Neuroscience Research Australia, University of New South Wales, Sydney, Australia 6 Departamento de Fisioterapia, Faculdade de Ciências e Tecnologia, UNESP, Univ Estadual Paulista, Presidente Prudente, Brazil 7 Department of General Practice, Erasmus MC, Rotterdam, The Netherlands 123 Eur Spine J (2017) 26:324–335 DOI 10.1007/s00586-016-4668-0 http://orcid.org/0000-0001-8052-1495 http://dx.doi.org/10.1007/s00586-016-4668-0 http://crossmark.crossref.org/dialog/?doi=10.1007/s00586-016-4668-0&domain=pdf http://crossmark.crossref.org/dialog/?doi=10.1007/s00586-016-4668-0&domain=pdf positions or walking and relieved by flexed positions or sitting on patients with radiologically confirmed lumbar spinal stenosis [2]. Patients with lumbar spinal stenosis have greater mobility limitation than patients with knee or hip osteoarthritis, and this results in important reductions in both functional ability and quality-of-life [3]. Lumbar spinal stenosis has become a commonly diag- nosed and treated condition of the spine—it is estimated that approximately one-fifth of adults aged 65 years or older will have symptoms of neurogenic claudication due to severe lumbar spinal stenosis [4, 5]; this condition becoming the most common reason for individuals older than 65 years undergoing spinal surgery [1, 6]. In fact, surgical management has become the standard procedure in the management of symptomatic lumbar spinal stenosis, and as a result, this procedure is currently the fastest growing surgical procedure worldwide [6, 7]. Recent report yielded various degrees of clinical symptoms in relation to radiological findings [5], which highlights the importance of correlation of both clinical and radiological findings when targeting the surgical procedures. A recent systematic review of randomised clinical trials of surgery for lumbar spinal stenosis has shown that although patients will experience decreases in pain and disability following sur- gery, over a quarter will have further spinal surgery 1 year after having spinal surgery, suggesting they may not experience full recovery [8]. Moreover, recent studies have shown that there is no correlation between the severity of clinical symptoms and dural cross-sectional areas [9, 10] or between increased canal diameter following surgery and symptom improvement (i.e., back or leg pain, functional status, and neurological claudication) [11]. It is, therefore, also unclear whether the initial benefits of surgery in terms of pain and disability are sustained over the years, or whether patients will experience increase in symptoms over time. However, randomised clinical trials are not the ideal design to infer long-term course, as they usually provide shorter follow-up data and more stringent inclusion criteria, if compared to cohort studies. We, therefore, aimed to systematically review the lit- erature to identify cohort studies assessing the long-term course of pain and disability in patients with lumbar spinal stenosis who have undergone surgery. To our knowledge, this is the first systematic review to assess the clinical course of lumbar spinal stenosis managed surgically. Methods Data sources and searches This review was prospectively registered on PROSPERO (registration number CRD42013005988). MEDLINE, CINAHL, and Embase databases were searched from inception to July 2014, to identify eligible studies. Search terms are available in Additional File 1. In addition to the electronic searches, citation tracking was conducted and the reference lists of the included studies in relevant sys- tematic reviews were checked. Study selection No language or geographic restrictions were included in the search strategy, but non-English studies were included in the review only when translation was available. Independent reviewers screened titles and abstracts (CF, MF, CGM, and PHF) for inclusion. The full text of potentially eligible studies was then obtained and assessed by three independent reviewers (CF, MF, and RP) for inclusion against our crite- ria. Disagreements were resolved by consensus. To be eligible for inclusion in the review studies needed to explicitly report that participants had a primary diag- nosis of lumbar spinal stenosis of any duration. Diagnosis had to be defined either by imaging techniques or clinically by the presence of signs and symptoms. All prospective surgical cohort studies with at least 3-month follow-up that reported pain or disability out- comes were included. Studies that only reported recovery rates or percentage change in pain or disability were excluded. Data extraction For each study, summary data were obtained on sample source, sample size, patient characteristics, outcomes (pain and disability), duration of follow-up, and inception time, if applicable. Measures of central tendency (e.g., mean or median) and dispersion (e.g., standard deviation, standard error or 95 % confidence intervals) were extracted for pain and disability outcomes. Outcome data were re-scaled to a common 0–100 scale to facilitate between-study compar- isons (e.g., means and standard deviations of pain scores given on a 0–10-point scale were multiplied by 10; means and standard deviations of disability scores given on a 24-point scale were multiplied by 4.1666 or 100/24). When insufficient data were reported on outcome measures, authors were contacted by e-mail for further details. If data on dispersion were not provided by the authors, standard deviations were imputed from similar studies. Quality assessment Methodological quality of included studies was assessed using an adaptation of the methodological criteria sug- gested by Altman [12] and include two items on sampling, two on completeness of follow-up, and one item on Eur Spine J (2017) 26:324–335 325 123 description of prognostic outcomes. These criteria have been used in a previous systematic review on prognosis of low back pain [13]. The results of the methodological quality assessment for each study are presented as per- centage (Table 1). Data synthesis To accommodate the different time points for outcome assessment in the included studies, pain and disability were modelled as a continuous function of time. For all analyses, time was treated as time from surgery. If studies reported more than one measure of pain intensity (e.g., back and leg pain), the more severe measure at baseline was included in the analyses. In addition, secondary analyses were per- formed for back pain and leg pain separately. Pooled estimates of outcomes were obtained using generalised estimating equations to account for the dependence of repeated observations (follow-ups) within studies. The observations from each study were assigned a weight equal to the inverse square of the mean SE of all observations from that study. The effect of time was clearly non-linear, so it was modelled using fractional polynomial regression [14]. The regression models were used to gen- erate pooled point and interval estimates of outcomes at baseline and 3, 6, 12, 24, and 60 months. Results From a total of 10,741 titles, 69 publications reporting on 64 cohort studies were included in the review (references [15–17] are multiple publications reporting follow-up assessments of the same cohort, as are [18, 19] and [20, 21]). These studies provided data on 3774 participants (Fig. 1). Table 1 presents the main characteristics of all included studies (complete references of included studies can be found in Additional File 2). In more than 50 % of the included studies, participants had persistent symptoms of lumbar spinal stenosis (n = 38; 57 %). For the remaining 31 studies, symptom duration was not reported. In approximately one-fifth of the included studies, the recruited participants had central canal stenosis (n = 12 studies), whereas most studies (n = 55 studies; 80 %) included a mixed population (i.e., central and lateral stenosis); and 3 % (two studies) included only participants with a diagnosis of lateral canal stenosis. In most studies, the main complaint of included participants was intermit- tent neurological claudication with or without pain (n = 42 studies; 61 %), followed by low back pain with or without leg pain (n = 11 studies; 16 %) and radicular pain only (n = 3 studies; 4 %). In 13 studies (19 %), main com- plaints were not reported or unclear. Methodological quality All included studies presented follow-up data for at least one outcome measure at 3 months or later (n = 69), but only approximately half (n = 40; 58 %) reported enough data on clinical prognosis of lumbar spine stenosis to be included in the meta-analyses. In over three quarters of the studies, the follow-up included at least 80 % of the sample (n = 55 studies or 81 %), however, only one-third of included studies (n = 25 studies or 37 %) clearly included a representative sample of participants with spinal stenosis and in only 61 % of the studies was the sample well defined (i.e., inclusion and exclusion criteria provided). Clinical course of pain and disability Of the 64 included studies (69 publications), 31 provided sufficient data on disability and 39 provided sufficient data on pain to be included in the meta-analysis. Follow-up time ranged from 3 to 72 months post-surgery. In all except one study [22], baseline assessments were performed pre-op- eratively at the time of hospital admission. Surgical admission was, therefore, regarded as the inception time in the mixed-model analyses. The study by Bednar [22] which did not report pain or disability at the time of surgical admission was excluded from the analyses. Ha et al. [23] did not report enough data to be included in the analyses and was also excluded. Pain and disability outcomes are presented in Fig. 2a and b, respectively. At inception (i.e., pre-operatively), the mean weighted pain score across all cohort studies was 63.4 (95 % CI 56.5–70.3). At 3-month post-surgery, pain had decreased to a weighted mean of 33.1 (95 % CI 24.2–41.9). Little further reduction in pain was seen at 6 months (mean 28.2; 95 % CI 19.1–37.4), 12 months (mean 24.5; 95 % CI 15.0–34.0), 24 months (mean 21.8; 95 % CI 12.0–31.5), or 60 months (mean 19.2; 95 % CI 9.2–29.3). The mean weighted disability scores at baseline were 36.9 (95 % CI 32.6–41.3), decreasing to 16.3 (95 % CI 11.8–20.9) at 3 months, 14 (95 % CI 9.3–18.6) at 6 months, 12.9 (95 % CI 8.2–17.6) at 12 months, 12.6 (95 % CI 7.8–17.3) at 24 months, and 12.4 (95 % CI 7.7–17.2) at 60 months. The mean standard deviation at baseline was 16.5 (range 6.0–30.3) for pain and 17.3 (range 4.1–62.0) for disability. This indicates a moderate degree of person-to-person variability in outcomes within studies. At inception, the mean weighted leg pain score was 53 points (95 % CI 43.9–62.2), decreasing to 17.6 (95 % CI 4.6–30.6) 3 months after surgery, and further decreasing at 6 (mean 17.0; 95 % CI 4.0–30.1), 12 (mean 15.9; 95 % CI 2.0–29.8), 24 (mean 13.6; 95 % CI -4.0 to 31.3), and 60 months (mean 6.8; 95 % CI -28.7 to 42.4). For back 326 Eur Spine J (2017) 26:324–335 123 Table 1 Characteristics of included studies References Country Diagnosis of lumbar spinal stenosis Age of participants (years) No. of participants (study entry) Symptom duration at study entry Outcome measures Follow-up Quality analysis score (%) Aleem et al. [33] Canada Mixed \70: n = 68 [70: n = 41 109 Not reported Disability (ODI 0–100) 6 weeks, 6 and 12 months 60 Anjarwalla et al. [34] UK Mixed Mean 53 (SD 14) 72 Not reported Pain (VAS 0–100), disability (ODI 0–100) 6 and 12 months 60 Athiviraham et al. [35] Canada Mixed Mean 66 88 35 % \12 months Disability (RMQ 0–14) 24 months 80 Atlas et al. [15] USA Mixed Mean 65.7 (SD 10.7) 81 61 % [6 months Back and leg pain (bothersomeness scale 0–6), disability (Modified RMQ 0–23) 3, 6, 9, and 12 months 80 Atlas et al. [16] USA Mixed Mean 65.7 (SD 10.7) 81 61 % [6 months Back and leg pain (bothersomeness scale 0–6), disability (Modified RMQ 0–23) 24, 36, and 48 months 80 Atlas et al. [17] USA Mixed Mean 65 (SD 10.7) 81 61 % [6 months Back and leg pain (bothersomeness scale 0–6), disability (Modified RMQ 0–23) 60, 72, 84, 96, 108 and 120 months 80 Bednar [22] Canada Mixed Mean 67 (range 52–85) 56 Not reported Pain (VAS 0–10), disability (ODI 0–100) 24 and 33 months 60 Beyer et al. [36] Germany Mixed Mean 69 (SD 9.7) 32 Not reported Back and leg pain (VAS 0–10), disability (ODI 0–100) 12 and 24 months 60 Bhadra et al. [37] UK Mixed Mean 61 (range 52–94) 45 70 % \24 months Back and leg pain (VAS 0–10), disability (ODI 0–100) unclear 80 Castro- Menendes et al. [38] Spain Mixed Mean 56 (SD 10.2) 50 30 months Back and leg pain (VAS 0–10), disability (ODI 0–100) 6, 12 and 48 months 80 Cavagna et al. [39] France Mixed Mean 73 (range 65–87) 39 Not reported Back and leg pain (VAS 0–100), disability (ODI 0–100) 6,12,24 and 48 months 60 Cavusoglu et al. [40] Turkey Mixed Mean 70 (SD 15.1) 50 Range 9–58 months Pain (VAS 0–10), disability (ODI 0–100) 3 and 22 months 60 Chopko et al. [41] USA Central Mean 70 (range 45–88) 45 Not reported Pain (VAS 0–10), disability (ODI 0–100) 6, 12 and 24 months 40 Colak et al. [42] Turkey Lateral Mean 52 (range 42–71) 16 53 months Pain (VAS 0–10) 3 and 12 months 80 Datta et al. [43] UK Mixed Mean 62 (SD 4) 20 35 months Back pain (VAS 0–10), disability (ODI 0–100) 6 months 60 Deer et al. [44] USA Central Mean 66 (range 46–80) 35 Not reported Pain (VAS 0–10), disability (ODI 0–100) 3, 6 and 12 months 60 Delank et al. [45] Germany Mixed Mean 68 13 Not reported Pain (VAS 0–10), disability (ODI 0–100) 6 and 12 months 80 El-Abed et al. [46] UK Mixed Mean 64 (SD 16.2) 120 C3 months Pain (VAS 0–10), disability (ODI 0–100) 6 and 36 months 80 Eur Spine J (2017) 26:324–335 327 123 Table 1 continued References Country Diagnosis of lumbar spinal stenosis Age of participants (years) No. of participants (study entry) Symptom duration at study entry Outcome measures Follow-up Quality analysis score (%) Endres [47] Germany Mixed Mean 80 (range 73–88) 58 Not reported Pain (VAS 0–10), disability (ODI 0–100) 46 months 60 Frazier et al. [48] USA Mixed Mean 67 (range 52–90) 90 Not reported Back and leg pain (VAS 0–10) 6 months 60 Fu et al. [49] China Mixed Mean 57 (range 45–73) 152 Not reported Back and leg pain (VAS 0–10), disability (ODI 0–100) 40 months 100 Greiner-Perth et al. [50] Germany Central, lateral and mixed Mean 73 17 Not reported Back and leg pain (VAS 0–10) 34 months 80 Ha et al. [23] Korea Mixed Mean 63 (SD 9.0) 31 Not reported Back and leg pain (VAS 0–10), disability (ODI 0–100) 3, 6, 12, 24, 31 months 80 Haro et al. [51] Japan Central Mean 67 (SD 10.9) 42 C6 months Back and leg pain (VAS 0–100), disability (ODI 0–100) 24 months 80 Herno et al. [52] Finland Mixed Mean 51 (range 22–67) 108 115 months Disability (ODI 0–100) 82, 154 months 60 Ikuta et al. [53] Japan Mixed Mean 69 37 40 months Disability (RM 0–24) 38 months 60 Jakola et al. [54] Norway Mixed Mean 75 (SD 4.1) 101 100 weeks Back and leg pain (VAS 0–100), disability (ODI 0–100) 3 and 12 months 60 Kaner et al. [55] Turkey Mixed Mean 67 (range 40–85) 30 C12 months Pain (VAS 0–10), disability (ODI 0–100) 3, 12 and 24 months 80 Kim et al. [56] Korea Mixed Mean 70 23 Not reported Pain (VAS 0–10), disability (ODI 0–100) 17.5 months 60 Kim et al. [57] Korea Mixed Mean 78 (range 75–82) 14 C3 months Pain (VAS 0–10), disability (ODI 0–100) 17.5 months 80 Komp et al. [58] Germany Central Mean 61 (range 43–81) 90 15 months Back and leg pain (VAS 0–100), disability (ODI 0–100) 3, 6, 12 and 24 months 60 Kong et al. [59] Korea Mixed Mean 58 (range 38–78) 42 Not reported Back and leg pain (VAS 0–10), disability (ODI 0–100) 12 months 80 Kuchta et al. [60] Germany Mixed Mean 69 (range 41–91) 175 Not reported Leg pain (VAS 0–100), disability (ODI 0–100) 6, 12 and 24 months 60 Mannion et al. [61] Australia/ UK Central Mean 70 (range 43–88) 50 Not reported Disability (ODI 0–100) 3, 6, 12 and 24 months 40 Mekhail et al. (62) USA Central Mean 72 (range 53–86) 34 60 months Pain (VAS 0–10), disability (RMQ 0–24) 6, 9, 12 and 24 months 80 Mekhail et al. (63) USA Mixed Mean 70 (range 45–88) 58 76 % [6 months Pain (VAS 0–10), disability (ODI 0–100) 12 months 80 328 Eur Spine J (2017) 26:324–335 123 Table 1 continued References Country Diagnosis of lumbar spinal stenosis Age of participants (years) No. of participants (study entry) Symptom duration at study entry Outcome measures Follow-up Quality analysis score (%) Mlyavykh et al. [93] Russia Mixed Mean 61 (range 47–71) 19 C6 months Back and leg pain (VAS 0–10), disability (ODI 0–100) 12 months 80 Ng et al. [64] UK Central Mean 62 (range 55–82) 100 73 months Pain (VAS 0–10), disability (ODI 0–100) 12 and 24 months 100 Ohtori et al. [65] Japan Central Mean 65 (range 55–80) 33 36 months Back pain (VAS 0–10), disability (ODI 0–100) 24 months 80 Paker et al. [66] Turkey Mixed Mean 65 (SD 7.3) 22 Not reported Pain (VAS 0–10) 18 months 60 Palmer et al. [67] USA Mixed Mean 67 (range 43–84) 54 Not reported Back and leg pain (VAS 0–10) 3, 6.5 and 11.5 months 60 Panagiotis et al. [68] Greece Mixed Mean 61 (range 33–79) 41 C6 months Pain (VAS 0–10), disability (ODI 0–100) 12, 24, 36, 48, 60 and 72 months 40 Pao et al. [69] Taiwan Mixed Mean 62 (range 36–86) 60 C3 months Disability (ODI 0–100) 15.7 months 100 Papavero et al. [70] Germany Mixed Median age (range 58.1–80.3) 165 C3 months Pain (VAS 0–10) 3 and 12 months 80 Parker et al. [71] USA Mixed Mean 57 (SD 11) 54 C6 months Leg pain (VAS 0–10), disability (ODI 0–100) 24 months 100 Parlato et al. [72] Italy Mixed Mean 49.6 (SD 13.4) 58 Not reported Pain (VAS 0–10) 3 and 12 months 100 Postacchini et al. [73] Italy Mixed Mean 65 (range 53–81) 66 8 months Disability (ODI 0–100) 3, 6 and 24 months 80 Reyes- Sanchez et al. [74] Mexico Mixed Mean 44 (range 24–60) 20 Not reported Back and leg pain (VAS 0–10), disability (ODI 0–100) 24 months 100 Richter et al. [19] Germany Mixed Mean 68.3 (range 49–79) 60 C3 months Pain (VAS 0–10), disability (ODI 0–100; RMQ 0–24) 3, 6 and 12 months 80 Richter et al. [18] Germany Mixed Mean 68 (range 52–79) 31 C3 months Pain (VAS 0–10), disability (ODI 0–100; RMQ 0–24) 24 months 60 Schaeren et al. [20] Switzerland Mixed Mean 71 (range 47–87) 26 35 months Pain (VAS 0–100) 52 months 60 Schnake et al. [21] Switzerland Mixed Mean 71 (range 47–87) 26 35 months Pain (VAS 0–100) 24 months 80 Schulte et al. [75] Germany Central Mean 69 (SD 7.5) 50 C3 months Back and leg pain (VAS 0–10), disability (ODI 0–100; RMQ 0–24) 3 and 12 months 100 Shabat et al. [76] Israel Mixed Mean 84 (range 80–91) 25 53 months Pain (VAS 0–10) 37 months 40 Shabat et al. [77] US Mixed Mean 70 (SD 11) 53 30 months Back and leg pain (VAS 0–10), disability (ODI 0–100) 12 and 24 months 60 Eur Spine J (2017) 26:324–335 329 123 pain, the mean weighted score pre-surgery was 35 points (95 % CI 23.5–46.4). Three months after surgery, back pain had decreased to 16.4 (95 % CI 0.0–32.8). Small increases in back pain scores were seen at 6 months (mean 16.9; 95 % CI 0.6–33.3) and at 12 (mean 18; 95 % CI 1.8–34.3), 24 (mean 20; 95 % CI 4.3–36.3), and 60 months (mean 26.9; 95 % CI 11.1–42.8). Discussion This systematic review included 64 cohort studies assess- ing post-operative outcomes in 3774 participants with lumbar spinal stenosis. The data show that most partici- pants presented with persistent symptoms of neurological claudication, with or without back or leg pain. Prior to Table 1 continued References Country Diagnosis of lumbar spinal stenosis Age of participants (years) No. of participants (study entry) Symptom duration at study entry Outcome measures Follow-up Quality analysis score (%) Sigmundsson et al. [78] Sweden Central Mean 71 (SD 10) 109 Not reported Back and leg pain (VAS 0–100), disability (ODI 0–100) 12 months 100 Sinikallio [79] Finland Mixed Mean 62 (SD 11.84) 96 Not reported Pain (VAS 0–100), disability (ODI 0–100) 3, 6, 12 and 24 months 80 Sobottke et al. [80] Germany Mixed Mean 68 (SD 9.7) 29 Not reported Back and leg pain (VAS 0–10), disability (ODI 0–100) 6 and 12 months 80 Stromqvist et al. [81] Sweden Central and lateral Mean 69 (range 49–89) 140 41 % [24 months Back and leg pain (VAS 0–100) 12, 24 and 60 months 40 Surace et al. [82] Italy Lateral Mean 64 (range 45–88) 35 Not reported Pain (VAS 0–10) 23 months 40 Tenhula et al. [83] US Mixed Mean 68 (SD 8.7) 32 Not reported Pain (VAS 0–10), disability (ODI 0–100) 6, 12 and 24 months 60 Westergaard et al. [84] Denmark Mixed Median 70 (IQR 19) 146 80 % C12 months Disability (ODI 0–100) 3, 6, 12 and 24 months 60 Wilkinson et al. [85] Canada Mixed Mean 63 (range 42–82) 10 Not reported Pain (VAS 0–10), disability (ODI 0–100) 3 months 100 Willen et al. [86] Sweden Mixed Mean 55 (range 31–76) 21 Not reported Back and leg pain (VAS 0–100), disability (ODI 0–100) 31 months 60 Wong Chung- Ting et al. [87] China Mixed Mean 60.2 (range 38–81) 70 C6 months Pain (VAS 0–10), disability (ODI 0–100) 35 months 60 Wong [88] US Mixed Mean 73.1 (range 63–86) 17 Not reported Pain (VAS 0–10), disability (ODI 0–100) 12 months 40 Yamashita et al. [89] Japan Mixed Mean 65.9 (range 50–81) 70 Not reported Back and leg pain (VAS 0–100) 3, 6, 12, 24, 36, 48 and 60 months 60 Yasar et al. [90] Turkey Central Mean 58 (SD 11) 125 48 % \24 months Disability (ODI 0–100) 3, 12 and 24 months 80 Yucesoy et al. [91] Turkey Central Mean 52.4 (range 15–64) 15 27 months Disability (ODI 0–100) 6 months 60 Yukawa et al. [92] US Mixed Mean 63.2 (SD 9.4) 62 Not reported Pain (VAS 0–10), disability (ODI 0–100) 46 months 60 330 Eur Spine J (2017) 26:324–335 123 surgery they reported, on average, moderate levels of pain and mild disability. Typically, patients experienced sub- stantial reductions (approximately, 50 %) in pain and dis- ability in the first 3-month post-surgery, but little further improvement over the subsequent 5 years. On average, mild levels of pain and disability persisted at 5 years. This is the first systematic review on the course of spinal stenosis following surgery. A quantitative approach pro- vided precise estimates of mean pain and disability at 3, 6, 12, 24, and 60 months following surgery. The review included a large number of cohort studies of generally moderate-to-low methodological quality. The main methodological flaw was failure to recruit and clearly describe a representative sample of patients (i.e., consec- utive patients presenting for care, or randomly selected patients) observed in more than half of the included stud- ies. About a third of the studies also failed to collect or clearly describe follow-up assessments on at least 80 % of the sample. One-third of the studies (n = 23; 33 %) had to be excluded from the pooled analyses due to incomplete reporting of data. In general, sample sizes were also very small—34 studies reported data on 50 participants or less. One of the main benefits of conducting a systematic review is that it provides pooled analyses of data from many studies—data from a total of 2097 participants were included in the analysis of pain and data from 1773 participants were included in the analysis of disability. Approximately half of the studies included in the pain and disability analyses were of high methodological quality (at least 80 % of total score). This gives us some confidence in the pooled estimates. The surgical techniques varied considerably across studies. Decompression was the most prevalent type of surgery and represented 31 % of the included studies. It was followed by microsurgical decompression, which represented approximately 20 % of the reports. Decom- pression associated with fusion was performed in approx- imately 10 % of the included studies. However, 14 % of the studies reported mixed interventions and performed decompression or decompression with fusion depending on the radiological findings and/or clinical symptoms. Like- wise, most studies performed a combination of single and multiple spinal-level decompression, according to the patient’s diagnosis. It is possible that these variations introduced between-study heterogeneity in the pooled analysis of outcomes. However, the lack of sufficient data provided by individual studies has prevented subgroup analyses based on the types of surgical technique. How- ever, a recent clinical trial comparing decompression sur- gery and decompression with fusion showed no superiority of the addition of fusion on pain, disability, walking ability, and quality-of-life up to 5 years after surgery [24]. In 14498 reports iden�fied through electronic database searching 14499 reports iden�fied 168 poten�ally relevant records iden�fied, and full text assessed for 1 report iden�fied through hand search of bibliographies 3758 duplicates removed 10741 reports screened by two reviewers 10573 reports excluded a�er screening �tles and abstracts because of 99 records excluded: 30 had no spinal stenosis 7 had no surgical interven�on 55 had no data, were reviews, case reports or retrospec�ve cohorts 8 had no follow-up or did not assess pain or disability 69 reports (64 cohorts) included in review Fig. 1 Flow chart showing process of selection of studies Eur Spine J (2017) 26:324–335 331 123 addition, a systematic review compared effectiveness in regards to pain and disability among the most common surgical procedures for lumbar spinal stenosis and also reported no significant difference [8]. Therefore, it is unlikely that subgroup analyses based on the type of sur- gery would have yielded significantly different results. Lumbar spinal stenosis is a highly debilitating spinal condition and its prevalence will increase over the next decades as the population ages. The number of spinal surgical procedures for spinal stenosis has also increased steadily over the years, possibly due to a scarcity of evi- dence on the effectiveness of non-operative management of this condition. Past research has shown that there is lack of high-quality evidence on the effectiveness of physiother- apy and non-operative interventions for patients with lumbar spinal stenosis, preventing their inclusion in clinical guideline recommendations [25, 26]. In the US, surgery for spinal stenosis was the fastest growing type of lumbar surgical procedure between 1980 and 2000 [27, 28] and in the last decade alone, Americans have experienced a 15-fold increase in the rate of complex fusions for lumbar spinal stenosis [6]. However, these procedures are known to be associated with important complications, such as need for cardiopulmonary resuscitation or repeat intubation [6], death [6], re-operation, and re-hospitalisation [29]. The need for re-operations following surgical procedures for lumbar spinal stenosis is not rare. In fact, the literature suggests that over one quarter of patients undergoing interspinous process implant will have a re-operation, including a revision of revision of the index procedure or the need to address the problem at a different spinal level [8]. The probability of having a second re-operation may be even greater (hazard ratio 1.58; 95 % CI, 1.41–1.76). Age and presence of comorbidities, however, seem to be associated with a lower chance of having a re-operation [29]. Re-operations and hospital re-admissions are often associated with greater risk of complications and with lower satisfaction with treatment when compared to the first surgical procedure [17, 30]. Our review provides evidence that patients can expect substantial relief of pain and disability in the first 3 months after surgery, but they can also expect long-term recovery to be incomplete. This information needs to be made available to patients when discussing the indication of surgical management for spinal stenosis. Past research also suggests that patients with lumbar spinal stenosis who also report symptoms of depression and present cardiovascular comorbidities or those resulting in impaired mobility have poorer clinical outcomes [30, 31] and greater chances of re-operation [30]. Likewise, there is compelling evidence showing that increased body weight is associated with worse self-rated quality-of-life and func- tion in patients with lumbar spinal stenosis [32]. The role of these putative predictors could not be further evaluated in our review, as individual patient data were not available. Future studies should explore the predictive value of these as well as other patient-level characteristics on the out- comes of patients who have surgery for spinal stenosis. Most importantly, high-quality randomised trials are nee- ded to provide robust estimates of the size of effects of surgery compared to no treatment. Conclusion People with spinal stenosis experience substantial reduc- tions in pain and disability in the first 3 months after sur- gery. Little further improvement is observed in the following 5 years. Fig. 2 Pain (a) and disability (b) outcomes after spinal stenosis surgery. 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