Optimizing the Management and Outcomes of Failed Back Surgery Syndrome: A Consensus Statement on Definition and Outlines for Patient Assessment

Failed back surgery syndrome (FBSS) is a controversial term for identifying patients affected by new, recurrent, or persistent pain in the low back and/or legs following spinal surgery. e lack of a comprehensive standardized care pathway compromises the appropriate management of FBSS patients, which is associated with a heavy financial burden. An international panel of spine surgeons, neurosurgeons, and pain specialists with a particular interest in FBSS established the chronic back and leg pain (CBLP) network with the aim of addressing the challenges and barriers in the clinical management of FBSS patients by building a common transdisciplinary vision. Based on literature reviews, additional input from clinical expertise of multiple professional disciplines, and consensus among its members, the network attempted to provide recommendations on the management of patients with FBSS utilizing a multidisciplinary team (MDT) approach. e presentation of this work has been divided in two separate parts to enhance its clarity. is first paper, in favour of selecting appropriate validated tools to improve the FBSS patient assessment, focuses on FBSS taxonomy and its clinical implications for evaluation. Concise recommendations for assessment, treatment, and outcome evaluation using a MDT approach would be an important resource for specialists and nonspecialist clinicians who manage patients with FBSS, to improve decision-making, reduce variation in practice, and optimize treatment outcomes in this difficult-to-treat population.

# Introduction
Failed back surgery syndrome (FBSS) is a subcategory of a broader group of pain conditions referred to as chronic back and leg pain (CBLP) [bib_ref] From "mechanical" to "neuropathic" back pain concept in FBSS patients. A systematic..., Blond [/bib_ref]. e majority of published definitions for FBSS include new, recurrent, or persistent pain in the back and/or legs following spinal surgery [bib_ref] Failed back surgery syndrome, Long [/bib_ref] [bib_ref] e failed back surgery syndrome": definition and therapeutic algorithms-an update, Buyten [/bib_ref] [bib_ref] Failed back surgery syndrome-definition, epidemiology and demographics, Omson [/bib_ref] [bib_ref] Failed back surgery syndrome: what's in a name? A proposal to replace..., Rigoard [/bib_ref] [bib_ref] Prevalence, characteristics, and burden of failed back surgery syndrome: the influence of..., Inoue [/bib_ref] [bib_ref] Failed back surgery syndrome, Chan [/bib_ref] , with an incidence estimated to be around 20% in the most recent publications on this topic [bib_ref] Incidence of low back pain after lumbar discectomy for herniated disc and..., Parker [/bib_ref] [bib_ref] e incidence and healthcare costs of persistent postoperative pain following lumbar spine..., Weir [/bib_ref]. is is a complex condition with a complicated pathophysiology comprising various aetiologies and pain characteristics that negatively impact function, behaviour, and mental and social well-being [bib_ref] From "mechanical" to "neuropathic" back pain concept in FBSS patients. A systematic..., Blond [/bib_ref] [bib_ref] Failed back surgery syndrome: what's in a name? A proposal to replace..., Rigoard [/bib_ref] [bib_ref] Pathophysiological characterisation of back pain generators in failed back surgery syndrome (part..., Rigoard [/bib_ref] [bib_ref] Failed back surgery syndrome: who has failed?, Kaisy [/bib_ref].
Use of the term FBSS has provoked decades of controversy because of a lack of consensus for a single definition and the inherently restrictive and confusing meaning of this acronym, implying unsuccessful treatment with connotations of blame aimed towards the surgery [bib_ref] Failed back surgery syndrome: who has failed?, Kaisy [/bib_ref]. A diverse nomenclature has consequently been developed over the last three decades. "Postlaminectomy syndrome" [bib_ref] Failed back surgery syndrome, Long [/bib_ref] [bib_ref] Low back pain and the post-laminectomy pain syndrome, Shipton [/bib_ref] , "rebound radicular syndrome" [bib_ref] Hyaluronidase in the management of pain due to post-laminectomy scar tissue, Borg [/bib_ref] , "postoperative persistent pain syndrome" [bib_ref] Failed back surgery syndrome: what's in a name? A proposal to replace..., Rigoard [/bib_ref] , and "chronic postsurgical pain"have been proposed as replacements for FBSS. e complexity of FBSS suggests that a multidisciplinary strategy to patient assessment, treatment, and therapy evaluation is important for optimization of outcomes [bib_ref] Interventional pain management for failed back surgery syndrome, Hussain [/bib_ref] [bib_ref] Medical management of failed back surgery syndrome in Europe: evaluation modalities and..., Durand [/bib_ref] [bib_ref] Failed back surgery syndrome: current perspectives, Baber [/bib_ref] [bib_ref] Multimodale therapiekonzepte beim postnukleotomiesyndrom, Casser [/bib_ref] , but no consensus has been clearly defined yet. An international panel of clinicians with a special interest in FBSS established the chronic back and leg pain (CBLP) network and set a list of precise objectives to bridge this gap. e purpose of this paper is to (i) delineate a clear definition of FBSS and specify the criteria for appropriate diagnosis and (ii) suggest recommended treatment evaluation tools to validate and standardize a care pathway for this patient group.

# Materials and methods

## E chronic back and leg pain network constitution and
Goals. To address the challenges and barriers in the management of patients diagnosed with FBSS, an international panel of clinical specialists with a specific interest in FBSS established the CBLP network in 2012. e main goals of the network were to provide consensus on (1) a definition of FBSS, (2) recommendations for validated tools to improve FBSS patient assessment and evaluation of treatment outcomes, and (3) a proposal for a standardized care pathway to support clinicians in their decision-making on how to manage patients with FBSS based on a MDT approach.
Since FBSS remains a standardized subjective term assigned by indexers for both MeSH (MEDLINE/PubMed) and EMTREE (Embase) and since the proposition of a replacement term was not an objective of this paper, the CBLP network focused specifically on the definition of FBSS and patient evaluation and treatment.

# Methodology.
In order to achieve the set goals, the following methodology was used:
(a) Participants in the CBLP panel were included based on their extensive clinical experience in managing FBSS patients with a focus on representation from the three specialties that are most involved in the treatment of this patient population: spine surgeons, neurosurgeons, and pain specialists, including anesthesiologists. Invitations were sent to potential participants and accepted prior to formal engagement. Formal face-to-face meetings were held annually between 2012 and 2016 with subsequent teleconferences for an additional feedback prior to drafting the manuscript. e meetings were chaired by a trained facilitator to help the consensus process. (b) Literature searches in PubMed, MEDLINE, LILACS, Embase, and the National Guideline Clearing House were conducted by two separate reviewers: one independent reviewer (GB) and one reviewer on the behalf of the clinical group (NN), on a regular basis up to September 2018, without any restrictions regarding language or year of publication. e search strategy was developed in order to maximise sensitivity of article identification, using controlled vocabulary and title/ abstract words combining variations of "Failed back surgery syndrome," "Back pain," "Chronic leg pain" with "Multidisciplinary" OR "Team," "Clinical pathway" OR "Practice guideline" OR "Algorithm" OR "Guideline" OR "Protocol," detailed here after. e independent reviewer (GB) performed a comprehensive electronic search of peer-reviewed full-text papers published between February 2, 2005, and February 21, 2018, in PubMed, MedLine, Embase, and the National Guideline Clearing House. Key words and terms pertaining to the condition (i.e., "failed back surgery syndrome," "low back pain," and "leg pain") were cross referenced with terms pertaining to reports presenting recommendations for MDT involvement in management (i.e., "interdisciplinary communication," "multidisciplinary" OR "multidisciplinary team" OR "multidisciplinary care" OR "patient referral") in relevant combinations. Handsearching of reference lists of identified reports and relevant review articles were also carried out. For the group reviewer (NN), the search strategy varied according to the database as follows:
(i) Medline ("Failed back surgery syndrome" OR "Chronic Back pain" OR "Chronic leg pain") AND ("Definition" OR "Characterisation" OR "Characterization" OR "Evaluation") (ii) LILACS ("Failed back surgery syndrome" OR "Back pain") AND ("Definition")
All references retrieved from databases were exported to Zotero where duplicates were discarded using the "find duplicates" tool. In addition, book chapters dealing with "FBSS," "postoperative low back pain," and the same controlled vocabulary used previously were initially identified from a systematic review of the electronic literature and of all pathophysiology, anatomy, and physiology textbooks available in the following medical libraries: e methodology is summarized in [fig_ref] Figure 1: Schematic diagram of steps in the literatures searches [/fig_ref]. (c) Additional input was provided by relevant clinical specialists (psychologist, psychiatrist, physiotherapist, and rehabilitation physician) involved in the multidisciplinary evaluation and treatment of patients with FBSS. (d) Consensus was defined as full agreement among the members of the CBLP network on the set goals which was achieved by face-to-face meetings with facilitated round table discussions focusing on the outcome of the literature overview, each member's personal experience, and input from additional clinical specialists. e consensus process did not include any ranking questionnaires based on the Delphi method since the number of participants was considered to be too small and the purpose of the discussions was not to measure consensus based on specific statements but to develop full consensus (resolve disagreement) on the set tasks [bib_ref] Qualitative Research: consensus methods for medical and health services research, Jones [/bib_ref].
[formula] (i) [/formula]

# Results

## Definition of fbss.
e CBLP network's proposed definition of FBSS is based on the prediction that no further spine surgery is indicated after an appropriate somatic, radiological, and psychosocial assessment [bib_ref] Failed back surgery syndrome: diagnostic evaluation, Guyer [/bib_ref].
e key elements for definition of FBSS can be summarized in 4 aspects:
(1) Back and/or leg pain that persists for at least six months following the most recent spinal surgery (2) e patient has undergone a thorough clinical and radiological assessment (3) ere is no clear surgical target on clinical examination and imaging that is concordant with presenting symptoms (4) ere is interdisciplinary agreement that additional surgical intervention (decompression and/or fusion) is not appropriate
It is important to ensure that the temporal relationship between the most recent surgery and the presentation of pain is explored adequately so that complications that are known to occur within the first six months of surgery (e.g., hardware failure, recurrent herniation, and infection, including discitis and abscess) can be identified and taken care of promptly [bib_ref] Failed back surgery syndrome: what's in a name? A proposal to replace..., Rigoard [/bib_ref]. As a consequence, our definition of FBSS is found on the generally accepted definition of chronic pain in the context of surgery as "pain that persists 6 months after an injury and beyond the usual course of an acute disease or a reasonable time for a comparable injury to heal" [bib_ref] Comprehensive review of epidemiology, scope, and impact of spinal pain, Manchikanti [/bib_ref].

## Multidisciplinary approach in the management of fbss.
Out of 12 pain-related guidelines or health technology assessments that were identified in the literature overview, nine recommended the practice of involving a MDT as the standard-of-care [bib_ref] Failed back surgery syndrome: who has failed?, Kaisy [/bib_ref] [bib_ref] Diagnosis and treatment of low back pain: a joint clinical practice guideline..., Chou [/bib_ref] [bib_ref] Practice guidelines for chronic pain management: an updated report by the American..., Benzon [/bib_ref] [bib_ref] Arbeitsgemeinschaft der Wissenschaftlichen medizinischen fachgesellschaften-association of scientific medical societies (AWMF), National disease..., Bundesarztekammer-German [/bib_ref]. Importantly, a previous metaanalysis of 41 randomized controlled trials (RCTs) (N  6,858) yielded by a systematic literature review up to March 2014 revealed that a MDT approach was significantly more effective than usual care in reducing pain and disability in patients with chronic low back pain [bib_ref] Multidisciplinary biopsychosocial rehabilitation for chronic low back pain, Kamper [/bib_ref].
In a general statement about pain management, the International Association for the Study of Pain (IASP) recommended that, "clinicians who assess and treat patients in a pain center should include physicians, nurses, mental health professionals (e.g., clinical psychologist and psychiatrist), and physical therapists". However, many patients do not have access to a pain center, making access to a MDT challenging. To date, recommendations for the composition of a FBSS-specific MDT provided by governments and experts alike suggest the involvement of a neurologist, a rheumatologist, a pain physician, a spine surgeon, a neurospine surgeon, a functional neurosurgeon, a rehabilitation physician, a radiologist, a physiatrist, a pain nurse, and a psychologist/psychiatrist [bib_ref] Failed back surgery syndrome: who has failed?, Kaisy [/bib_ref] [bib_ref] Medical management of failed back surgery syndrome in Europe: evaluation modalities and..., Durand [/bib_ref].
Based on the literature review [fig_ref] Table 1: Output of the review of publications with recommendations for specialties to be... [/fig_ref] , additional specialist input and consensus among its members, the CBLP network recommends that a FBSS-oriented MDT should include five types of health professionals, reflecting the continuum of the FBSS patient care pathway: (i) One or several "pain physician(s)" (i.e., anaesthetist, rheumatologist, and neurologist) representing the cornerstone of professional interactions for the assessment and treatment of pain, focusing on optimizing medical and interventional management within the FBSS care pathway (ii) One or several rehabilitation physicians, physiotherapist(s), and/or physiatrist(s) to optimize physical examination and review potential rehabilitation strategies (iii) One or several psychologist(s) and/or psychiatrist(s) to focus on psychosocial aspects and supply ongoing psychological evaluation and support [bib_ref] Behavioural treatment for chronic low-back pain, Henschke [/bib_ref] [bib_ref] e effectiveness of cognitive behavioural treatment for non-specific low back pain: a..., Richmond [/bib_ref] (iv) One or several "spine surgeon(s)" (i.e., neurosurgeon and orthopaedic surgeon) supported by a radiologist to provide an ultimate spine expertise, making sure that no further surgery is required helping to characterize the pathophysiology of pain generators (v) One or several member(s) of a "neuromodulation team" (i.e., implanter/anaesthesiologist/neurosurgeon and pain/neuromodulation nurse) to evaluate the eligibility for neurostimulation/intrathecal drug delivery (IDD) therapies in the context of a refractory patient

## Initial mdt evaluation.
e initial stage in the proposed care pathway by the CBLP network is based on MDT evaluation to confirm the FBSS diagnosis. With a specific reference to our definition of FBSS, the clinical work-up of a patient should include the following: (a) history to confirm the occurrence of prior spinal surgeries; (b) precise

## Physical
Examination. It remains difficult to transpose a "mechanistic" concept based on pathophysiological evaluation of pain into daily practice. Nevertheless, this approach plays a critical role to better understand FBSS management. Several authors have tried to identify, from all of the findings of spine examination, those clinical signs that are predictive of a particular type of lesion (facet joint and discogenic or muscle pain, for example), taking into account pain typology (mechanical/neuropathic) [bib_ref] Failed back surgery syndrome: what's in a name? A proposal to replace..., Rigoard [/bib_ref]. is type of pathophysiological segmentation might be used to predict the quality and the magnitude of response to the various treatments proposed (classical response to opioids in nociceptive pain and efficacy of antiepileptic drugs or neurostimulation in neuropathic pain, for example). An emphasis on the spatial dimension concerning the topographic distribution of the pain should be incorporated into the concept of pathophysiological pain characterization.
us, chronic leg pain persisting despite a surgical decompression might be frequently associated to a neuropathic pain component, while the pain characterization becomes much more complex when trying to interpret axial pain, where biomechanical and neuropathic components appear to be inseparable or difficult to isolate [bib_ref] From "mechanical" to "neuropathic" back pain concept in FBSS patients. A systematic..., Blond [/bib_ref]. Even though promoting strict dichotomy between the leg pain and the back pain components might be artificial, this clinical strategy can nevertheless guide the physician in the clinical evaluation.
(1) e Leg Pain Component. e first step of leg pain clinical examination aims to confirm a radicular lesion mainly indicative of neuropathic pain and to eliminate pain due to another cause. e presence of sensory dysfunction (hypoesthesia, anesthesia, or allodynia) in the painful territory and/or motor deficit is suggestive of a nerve lesion and thus a neuropathic pain. Several diagnostic tools have been validated for neuropathic pain detection: DN4 (Douleur Neuropathique in 4 questions), LANSS (Leeds assessment of neuropathic symptoms and signs), or S-LANSS (simplified version) [bib_ref] Comparison of pain syndromes associated with nervous or somatic lesions and development..., Bouhassira [/bib_ref] [bib_ref] e S-LANSS score for identifying pain of predominantly neuropathic origin: validation for..., Bennett [/bib_ref]. e DN4 questionnaire, published in 2005, is easy to use in daily practice. It is composed of four questions comprising a total of seven items scored during the clinical interview and three items based on physical examination [bib_ref] Comparison of pain syndromes associated with nervous or somatic lesions and development..., Bouhassira [/bib_ref]. A score greater than or equal to 4/10 is pathognomonic of neuropathic pain with a sensitivity of 82.9% and a specificity of 89.9%. Shamji and Shcharinsky [bib_ref] Use of neuropathic pain questionnaires in predicting persistent postoperative neuropathic pain following..., Shamji [/bib_ref] recently stated that a positive DN4 questionnaire is a powerful predictor of spine (re)surgery failure. e presence of mechanical signs of disc-nerve root conflict (impulse pain, Lasegue's sign) suggests a physical conflict at the level of the disc (disc herniation recurrence and residual conflicting elements) or at the level of the foramen (foraminal stenosis and segmental spine instability) [bib_ref] Medical management of failed back surgery syndrome in Europe: evaluation modalities and..., Durand [/bib_ref] and requires a specific spine expertise. Hip, knee, and sacroiliac joints examination are important to avoid the classical diagnostic traps associated with pain of the anterior surface of the thigh or trunked S1 sciatica. A vascular examination has to be performed in case of intermittent claudication on walking. A careful palpation of the sciatic trunk eliminates a neurinoma and a piriformis syndrome at the gluteal region.
(2) e Back Pain Component. In contrast to leg pain assessment, and before considering any potential neuropathic aspect of the back pain (first described by Attal et al. in 2011) [bib_ref] e neuropathic components of chronic low back pain: a prospective multicenter study..., Attal [/bib_ref] , clinical investigation of the back pain component in FBSS patients should be based on meticulous dissection of all potential mechanical triggers that could be a source of the nociceptive pain characteristics [bib_ref] Pathophysiological characterisation of back pain generators in failed back surgery syndrome (part..., Rigoard [/bib_ref]. Examination of the spine aims to assess the global posture and stability of the spine in the different planes. Meticulous palpation aims to identify a possible vertebral or paravertebral pain trigger point. e main focus of the back assessment is guided by a somatic diagnostic process using validated diagnostic rules [bib_ref] Clinical classification in low back pain: best-evidence diagnostic rules based on systematic..., Petersen [/bib_ref]. e key potential spinal pain generators, which need to (i) Muscle pain: the muscle trophicity may be compromised by chronic degeneration related to the initial spine pathology, by physical hypoactivity, and by repeated surgery, leading to potential and progressive instability of the vertebral column. A vicious circle can occur when biomechanical overloading (created by disease progression and/or hardware failure) causes displacements of the spine and induces new tensions. Results show increased impulse activity of muscle and tendon nociceptors establishing the neurophysiological basis of postoperative muscle pain. (ii) Facet joint pain and spinal instability: spine surgery induces major changes in the biomechanical loads on all surrounding structures: muscles, ligaments, discs, facet joints, fat tissues, and fascia. is mechanical loading redistribution occurs particularly in adjacent spinal segments, around the anterior or posterior instrumentation in case of stabilization [bib_ref] Pathophysiological characterisation of back pain generators in failed back surgery syndrome (part..., Rigoard [/bib_ref]. Foraminal residual stenosis can be responsible for persistent nerve entrapment, as mentioned above: anteriorly from vertebral spurs and posteriorly from facet arthritic changes. As a consequence, patient's symptoms can be linked to facet compensation syndrome [bib_ref] Low back pain of dorselumbar origin: surgical treatment of posterlor articular capsule..., Maigne [/bib_ref] , but isolating facets as the specific source of pain is difficult in FBSS patients. (iii) Discogenic pain: it is predominantly described as a deep midline low back pain with a bilateral metameric irradiation. Mechanical and positional in nature, the pain is generally worse when upright rather than supine. It is thought that this type of pain is generated by the visceral afferents that innervate the intervertebral disc, known as "the sinuvertebral nerve" [bib_ref] e nerve supply to the human lumbar intervertebral discs, Bogduk [/bib_ref].

## Validated tools for assessment of pain and functional
Parameters. In line with the adoption of a uniform MDT approach to the management of FBSS, it is important to utilize recommended validated tools to evaluate treatment outcomes in patients with pain disorders in compliance with IMMPACT recommendations [bib_ref] Core outcome measures for chronic pain clinical trials: IMMPACT recommendations, Dworkin [/bib_ref] [bib_ref] Developing patient-reported outcome measures for pain clinical trials: IMMPACT recommendations, Turk [/bib_ref]. e aims of a standardized assessment in this context are to facilitate longitudinal patient evaluation, to increase the efficiency, clarity, and quality of patient information during the referral process and to improve dialogue between centers and disciplines in order to optimize treatment decisions. e aims of a common approach to treatment evaluation are therefore relevant to patients, clinicians, payers, and policymakers [bib_ref] e economic impact of failed back surgery syndrome, Taylor [/bib_ref].
e CBLP network recognizes that treatment evaluation should involve previously issued quality standards and guidelines for documentation of outcomes including the patient's subjective assessment of pain severity, function, and health-related quality of life (HRQoL) [bib_ref] Core outcome measures for chronic pain clinical trials: IMMPACT recommendations, Dworkin [/bib_ref] [bib_ref] Evaluating the correlation and responsiveness of patient-reported pain with function and quality-of-life..., Devine [/bib_ref]. Having considered the plethora of existing tools used to evaluate these constructs from the patient's perspective, clinical experience guided the CBLP network to recommend a choice of standardized and validated instruments [fig_ref] Table 2: Validated questionnaires recommended for completion by patients to assess pain severity, function,... [/fig_ref].
For pain severity scales, there is a choice of the visual analogue scale (VAS) or the numeric pain rating scale (NPRS) [bib_ref] Responsiveness of the numeric pain rating scale in patients with low back..., Childs [/bib_ref] [bib_ref] Validation of a verbally administered numerical rating scale of acute pain for..., Bijur [/bib_ref] [bib_ref] Core outcome measurement instruments for clinical trials in nonspecific low back pain, Chiarotto [/bib_ref]. To assess pain-specific disability/function, either the Oswestry Disability Index (ODI) [bib_ref] e Oswestry disability index, Fairbank [/bib_ref] or the Roland Morris Disability Questionnaire (RMDQ) [bib_ref] A study of the natural history of back pain. Part I: development..., Roland [/bib_ref] is recommended. To measure generic HRQoL, either the EuroQol with five dimensions (EQ-5D) [bib_ref] e EuroQol instrument: an index of health related quality of life, Kind [/bib_ref] or the short form 12/36 (SF-12/SF-36) [bib_ref] A 12-item short-form health survey: construction of scales and preliminary tests of..., Ware [/bib_ref] [bib_ref] e MOS 36-item short-form health survey (SF-36): II. Psychometric and clinical tests..., Mchorney [/bib_ref] is recommended. e shorter generic HRQoL instruments, the SF-12 and the EQ-5D, minimize patient burden. It is also recommended that clinicians continuously monitor and evaluate a patient's medication intake.

## Psychosocial assessment.
It is well established that psychological factors affect pain perception [bib_ref] Psychosocial factors in chronic spinal cord injury pain, Summers [/bib_ref] and clinical outcomes [bib_ref] e nerve supply to the human lumbar intervertebral discs, Bogduk [/bib_ref] [bib_ref] Epidemiology of chronic pain with psychological comorbidity: prevalence, risk, course, and prognosis, Tunks [/bib_ref] [bib_ref] Pretreatment psychosocial variables as predictors of outcomes following lumbar surgery and spinal..., Celestin [/bib_ref] [bib_ref] Psychological predictors of recovery from low back pain: a prospective study, George [/bib_ref] [bib_ref] Evaluating psychosocial contributions to chronic pain outcomes, Meints [/bib_ref] [bib_ref] Psychosocial factors associated with change in pain and disability outcomes in chronic..., Alhowimel [/bib_ref]. ere is no accepted gold standard approach for the psychological screening of FBSS patients. Optional questionnaires can be used to assist the psychological assessment. e most recognized questionnaire in this context is the Minnesota Multiphasic Personality Inventory 2 Restructured (MMPI-2-RF) [bib_ref] MMPI-2 characteristics in a chronic pain population, Slesinger [/bib_ref] [bib_ref] Psychological risk factors for poor outcome of spine surgery and spinal cord..., Block [/bib_ref] [bib_ref] Associations between pre-implant psychosocial factors and spinal cord stimulation outcome: evaluation using..., Block [/bib_ref] [bib_ref] Prospective comparison of the Minnesota multiphasic personality inventory-2 (MMPI-2) and MMPI-2-restructured form..., Tarescavage [/bib_ref].
e Hospital Anxiety and Depression Scale (HADS) allows detection of various states of depression (HADS-D) and anxiety (HADS-A) [bib_ref] e hospital anxiety and depression scale, Zigmond [/bib_ref] [bib_ref] Validity of the hospital anxiety and depression scale in patients with chronic..., Castro [/bib_ref] [bib_ref] Pain-related distress and clinical depression in chronic pain: a comparison between two..., Rusu [/bib_ref] , and the Fear Avoidance Beliefs Questionnaire Work and Activity (FABQ) measures patient's fear of pain [bib_ref] A Fear-Avoidance Beliefs Questionnaire (FABQ) and the role of fear-avoidance beliefs in..., Waddell [/bib_ref].
Coping strategies may play an important role by determining how patients cooperate with chronic symptoms and with pain management [bib_ref] e use of coping strategies in chronic low back pain patients: relationship..., Rosenstiel [/bib_ref] [bib_ref] Coping with rheumatoid arthritis pain: catastrophizing as a maladaptive strategy, Keefe [/bib_ref]. e Coping Strategies Questionnaire (CSQ) is intended to measure six cognitive and two behavioural coping strategies. Active coping strategies are linked to positive effect, better psychological adjustment, and decreased depression, while passive strategies are linked to poorer outcomes such as depression and increased level of pain [bib_ref] Evaluating psychosocial contributions to chronic pain outcomes, Meints [/bib_ref] [bib_ref] e impact of passive coping on rheumatoid arthritis pain, Covic [/bib_ref] [bib_ref] e role of psychosocial processes in the development and maintenance of chronic..., Edwards [/bib_ref]. An important subscale of CSQ is catastrophizing. Based on the CSQ, Sullivan and colleagues [bib_ref] e pain catastrophizing scale: development and validation, Sullivan [/bib_ref] developed the Pain Catastrophizing Scale (PCS). e PCS is widely used, and elevated scores have been associated with poor treatment outcomes. e optimization of chronic pain management requires consideration of the social factors that may contribute to people's physical and mental health [bib_ref] Psychosocial predictors of health-related quality of life and health service utilisation in..., Keeley [/bib_ref] [bib_ref] Inequalities in health: definitions, concepts, and theories, Arcaya [/bib_ref]. Factors such as gender, level of education, and working status play a substantial role in pain perception and affect patient compliance and their pain management [bib_ref] Evaluating psychosocial contributions to chronic pain outcomes, Meints [/bib_ref] [bib_ref] Gender role expectations of pain: relationship to experimental pain perception, Wise [/bib_ref] [bib_ref] Sex differences in pain perception, Wiesenfeld-Hallin [/bib_ref] [bib_ref] e impact of socio-economic status on pain and the perception of disability..., Dorner [/bib_ref] [bib_ref] Factors affecting therapeutic compliance: a review from the patient's perspective, Jin [/bib_ref] [bib_ref] Trajectories and predictors of the long-term course of low back pain: cohort..., Chen [/bib_ref]. Medical professionals trained to solve a physical/somatic problem, where there is a potential biopsychosocial comorbidity may fail to anticipate and manage the vicious circle of social exclusion. ese arguments support the need for including social assessment in a MDT approach, as it affects clinical outcome in chronic pain management [bib_ref] e impact of social deprivation on chronic back pain outcomes, Carr [/bib_ref].
A proposal for a minimal psychosocial assessment toolbox is presented in [fig_ref] Table 3: Instruments to assess psychological and social well-being among patients with failed back... [/fig_ref].

## Radiological assessment.
In addition to orthopaedic, neurologic, functional, and psychosocial evaluation, spine imaging is essential in order to exclude new indications for reoperation: recurrent disc herniation (MRI), spine instability (CT, MRI, and bending X-ray), spine imbalance (fullstanding lateral and anteroposterior X-ray), EOS  images while the patient is standing (bending X-ray), or nonunion of spinal fusion (plain X-ray, CT, scintigraphy, and positron emission tomography (PET) scan), new-onset stenosis (MRI and CT), and abscess (MRI and CT) [bib_ref] Medical management of failed back surgery syndrome in Europe: evaluation modalities and..., Durand [/bib_ref] [bib_ref] Failed back surgery syndrome: to reoperate or not to re-operate? A retrospective..., Assaker [/bib_ref]. Conditions like discitis, low-grade infections, arachnoiditis, or scar tissue which usually do not require reoperation have also to be identified before being managed conservatively [bib_ref] Failed back surgery syndrome: current perspectives, Baber [/bib_ref].
Following a robust MDT clinical evaluation to define and diagnose a patient with FBSS [fig_ref] Figure 2: e initial stage of the proposed standardized multidisciplinary team failed back surgery... [/fig_ref] , a stratification and hierarchization of the various therapeutic options can be constructed through a level approach to optimize management and outcomes. A patient who either does not present with FBSS or presents with FBSS and a significant psychosocial comorbidity, determined by psychological assessment carried out by a clinical psychologist or psychiatrist (ideally with experience in the field of pain), should be excluded from the pathway and referred to the appropriate discipline(s).

# Discussion
Use of the term FBSS has provoked decades of controversy because of a lack of consensus of a definition and the inherently restrictive and confusing meaning of this acronym. e term hides the challenges associated with selecting appropriate treatment for this patient population due to insufficient identification of the underlying mechanism of pain [bib_ref] Failed back surgery syndrome-definition, epidemiology and demographics, Omson [/bib_ref] [bib_ref] Failed back surgery syndrome: what's in a name? A proposal to replace..., Rigoard [/bib_ref]. In addition, cognitive, affective, and behavioural features of pain are often explanations of the disability as much as or more than abnormal sensory-related pain [bib_ref] Failed back surgery syndrome-definition, epidemiology and demographics, Omson [/bib_ref].
In response to the limitations of current practice in managing FBSS patients, an international panel of spine surgeons, neurosurgeons, and pain specialists with a special interest in FBSS established the CBLP network. Based on the broad personal experience of each member of the panel, through literature reviews, additional input from clinical expertise of multiple professional disciplines and consensus among its members, the CBLP network's primary intention is to provide recommendations on how to optimize the management and outcomes of FBSS.
In this paper, we focus on the key elements for defining FBSS and outline how to clinically confirm this diagnosis.
e CBLP network's definition of FBSS is found on the prediction that no further spine surgery is indicated after adequate somatic, psychosocial, and radiological assessment have been executed. Management begins with a systematic evaluation of common FBSS aetiologies. Appropriate understanding and identification of the abnormalities most commonly associated with FBSS after a meticulous clinical evaluation is required for adequate caretaking of this often hard-to-treat condition [bib_ref] From "mechanical" to "neuropathic" back pain concept in FBSS patients. A systematic..., Blond [/bib_ref] [bib_ref] Failed back surgery syndrome-definition, epidemiology and demographics, Omson [/bib_ref]. A growing body of data suggests that the adoption of a multidisciplinary approach is significantly more effective than usual care of patients with chronic low back pain [bib_ref] Multidisciplinary biopsychosocial rehabilitation for chronic low back pain, Kamper [/bib_ref] [bib_ref] Interdisciplinary treatment of failed back surgery syndrome (FBSS): a comparison of FBSS..., Miller [/bib_ref] [bib_ref] Etiology, evaluation, and treatment of failed back surgery syndrome, Sebaaly [/bib_ref]. A MDT-based approach has the potential to improve decision-making, reduce variation in practice, and optimize treatment outcomes. Clinicians should refine pain topographical and topological pain characterization to ensure that clinical evaluation becomes the guiding principle for multidisciplinary assessment. A patient who either does not present with FBSS or presents with FBSS and significant psychosocial comorbidities should be excluded from further inclusion in FBSS care pathways or algorithms and be referred to the appropriate discipline(s).
For many aspects of medical practice, there is a lack of high-quality evidence and a plethora of contradictory information which makes decision-making difficult when trying to optimize treatment outcomes and provide concise recommendations for assessment, treatment, and outcome evaluation. When dealing with a lack of, or conflicting, scientific evidence, consensus statements are seen as a useful tool to establish expert agreement, to define the boundaries of acceptable practice and obtain opinions from different countries and healthcare systems [bib_ref] Qualitative Research: consensus methods for medical and health services research, Jones [/bib_ref] [bib_ref] Democracybased consensus in medicine, Greco [/bib_ref]. Due to the paucity of evidence-based guidelines in the management of FBSS, the CBLP network chose to adhere to a consensus-based approach to achieve the set goals to define FBSS, design outlines for appropriate patient evaluation, and propose a treatment pathway. One limitation of the chosen method to achieve consensus in the present study is that it was based on round table discussions without involvement of ranking procedures that are used in the two most commonly utilized methods to reach consensus: the Delphi process and the nominal group technique [bib_ref] Qualitative Research: consensus methods for medical and health services research, Jones [/bib_ref]. Although not optimal, we consider the method we adopted to be appropriate based on the complexity of the set tasks which do not fit easily within an evidence-based treatment paradigm. Since personal contact with facilitated discussions among the network members was considered desirable, the Delphi method, the reliability of which rests on anonymity and increases with the size of the group, was not used.

# Conclusions
e complexity of FBSS suggests that a multidisciplinary strategy is most appropriate for patient assessment with the goal to optimize outcomes. is paper focuses on redefining FBSS taxonomy and clinical evaluation in order to improve patient assessment before adequate treatment options can be chosen. It is important for physicians and other healthcare professionals involved in the management of patients with FBSS to expand their knowledge of underlying aetiologies and use of appropriate diagnostic tools to adequately evaluate this difficult-to-treat group affected with chronic pain. In a second paper, a stratification and hierarchization of the various therapeutic options is constructed through a 4 level-approach with a proposal for a standardized treatment pathway for FBSS. e utilization of a MDT approach is emphasized to ensure that care is provided in a uniform manner for optimizing management and ultimately patient outcomes. Disclosure e funder did not provide input into the discussions or the consensus. Medtronic manufactures devices indicated for failed back surgery syndrome and may therefore gain from the implementation of the pathway described in this article.

## Conflicts of interest
Philippe Rigoard, Kliment Gatzinsky, Jean-Philippe Deneuville, Wim Duyvendak, Nicolas Naiditch, Jean-Pierre Van Buyten, and Sam Eldabe treat patients with failed back surgery syndrome in the private an/or the public healthcare sectors and therefore may gain from the implementation of the pathway. Philippe Rigoard, Kliment Gatzinsky, Wim Duyvendak, Jean-Pierre Van Buyten, and Sam Eldabe were reimbursed for travel to Chronic Back and Leg Pain Network meetings and received honoraria for Chronic Back and Leg Pain Network meeting participation from Medtronic Inc., and may therefore have a preexisting relationship with Medtronic, the Funder, and may be influenced by beliefs associated with treatments recommended in the pathway. Philippe Rigoard, Kliment Gatzinsky, Sam Eldabe, and Wim Duyvendak have served as consultants to Medtronic Inc., and Boston Scientific and may therefore have a preexisting relationship with them and be influenced by beliefs associated with treatments recommended in the pathway. Kliment Gatzinsky and Sam Eldabe have served as consultants to Abbott and may therefore have a preexisting relationship with them and be influenced by beliefs associated with treatments recommended in the pathway. Sam Eldabe has served as a consultant to Mainstay Medical and may have a preexisting relationship with them and be influenced by beliefs associated with treatments recommended in the pathway. Philippe Rigoard, Wim Duyvendak, and Sam Eldabe have received research funding from Medtronic Inc., and may be influenced by beliefs Patient presents with ongoing back and/or leg pain that has persisted for >6 months following most recent spinal surgery Evaluation by an MDT to include orough somatic evaluation (i) (ii) (iii) (iv) (v) (vi) (vii) Spine and biomechanical assessment (including imaging) Psychosocial evaluation 1 Pain assessment: neuropathic/nociceptive/mixed pain Functional evaluation Confirmation of diagnosis of FBSS Determination of appropriate treatment MDT, multidisciplinary team. [bib_ref] From "mechanical" to "neuropathic" back pain concept in FBSS patients. A systematic..., Blond [/bib_ref] Best practice is for the psychosocial evaluation to be performed by a psychologist or psychiatrist with specific experience in the field of pain. Assessment should include the relevant tests and questionnaires that are able to identify patients with major psychological or psychiatric contraindications [fig_ref] Table 3: Instruments to assess psychological and social well-being among patients with failed back... [/fig_ref]. associated with treatments recommended in the pathway. Philippe Rigoard and Wim Duyvendak have received research funding from Boston Scientific and Abbott and may be influenced by beliefs associated with treatments recommended in the pathway. Sam Eldabe has received research funding from Nevro and may be influenced by beliefs associated with treatments recommended in the pathway. Nicolas Naiditch and Jean-Philippe Deneuville declare that there are no conflicts of interest regarding the publication of this paper.
[fig] Figure 1: Schematic diagram of steps in the literatures searches: FBSS definition and evaluation. e electronic and hand literature searches yielded 1663 titles and 74 textbooks. Following a review of full-text versions of the 363 residual publications, after discarding duplicates and initial exclusion of 1300 titles/abstracts, 108 papers were finally selected, and 12 were retained for FBSS definition and MDT assessment and composition (Supplementary Material 1). [/fig]
[fig] Figure 2: e initial stage of the proposed standardized multidisciplinary team failed back surgery syndrome care pathway, as recommended by the Chronic Back and Leg Pain Network. Clinical evaluation and confirmation of diagnosis. FBSS, failed back surgery syndrome; [/fig]
[table] Table 1: Output of the review of publications with recommendations for specialties to be included in the multidisciplinary team management of failed back surgery syndrome. Pain History.e pain history must be carefully reviewed and pay specific attention to the following items:(i) New pain, persistent pain, and/or recurrent pain? (if yes, free interval needs to be quantified) (ii) Circumstances, positions, and movements that improve or exacerbate the symptoms[17] (iii) Any clinical sign that might be suspicious of underlying infection, neoplasm, and fracture, called "red flag" by the COST B13 group in available European guidelines[37] [/table]
[table] Table 2: Validated questionnaires recommended for completion by patients to assess pain severity, function, and health-related quality of [/table]
[table] Table 3: Instruments to assess psychological and social well-being among patients with failed back surgery syndrome (FBSS). [/table]