Predicting Response to Interventional Pain Management Techniques in Chronic Low Back Pain in a Prospective Cohort.

Study Overview
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Brief Summary
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The main aim of this study is to identify factors that may be associated with a better or worse response to interventional pain management therapies for the treatment of chronic lumbar pain in adult patients. If several predictive factors are to be identified, a predictive model will be developed.

Detailed Description
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Chronic lumbar pain is a common affection in the adult population, and an important source of chronic incapacity and impaired quality of life. There is a wide range of therapeutic options for the treatment of chronic lumbar pain. This study will analyze the response to several interventional pain management techniques and will search for factors that may be associated to a better or worse response to the techniques.

Official Title
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Observational Prospective Single Centre Study of the Response to Interventional Pain Management Techniques in Chronic Low Back Pain in Adults. 1 and 6 Months Follow-up. Multivariate Analysis of Predictors of Response. Predictive Model.

Conditions
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Low Back Pain, Pain Measurement, Chronic Pain, Analgesia, Epidural, Clinic, Pain

Intervention / Treatment
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* Procedure: Fluoroscopically guided lumbar medial branch nerve radiofrequency denervation.
* Procedure: Fluoroscopically guided lumbar facet joint injection.
* Procedure: Fluoroscopically guided lumbar epidural corticosteroid injection.
* Procedure: Fluoroscopically guided caudal epidural corticosteroid injection.
* Procedure: Fluoroscopically guided pulsed radiofrequency of the lumbar dorsal root ganglion.
* Procedure: Fluoroscopically guided transforaminal epidural corticosteroid injection or lumbar selective root block.


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients older than 18 years old with chronic lumbar pain to whom one of the following interventional pain management techniques has been indicated: Radiofrequency lumbar facet joint injection Radiofrequency lumbar facet joint denervation Lumbar epidural corticosteroid injection Caudal epidural corticosteroid injection Pulsed radiofrequency of the lumbar dorsal root ganglion Dorsal root ganglion injection Exclusion Criteria: Patients that have not undergone the interventional pain management technique. The interventional pain management technique is considered not performed if it is not done after a twelve month period after recruitment. Patients who are not willing to participate. Patients of whom it is impossible to obtain data of response. Patients who undergo low back surgery while they are in the study. Patients who suffer from an intercurrent disease that may interfere with the evaluation of chronic lumbar pain. Patients who suffer from myofascial pain syndromes. Patients who undergo pulsed radiofrequency denervation for the treatment of sacroiliac joint syndrome.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Procedure: Fluoroscopically guided lumbar medial branch nerve radiofrequency denervation.|While in prone position, lumbar facet joints are identified by fluoroscopy. 18 gauge needles are then advanced aiming to the medial branch of lumbar facet joints. Correct positioning is confirmed by anteroposterior and lateral fluoroscopy. Then, the needles are attached to the radiofrequency device. Correct positioning of the needles is confirmed also by sensitive stimulation (paresthesia evocation) with the following settings: 50 Hz (hertz), 1ms, 0,6V (volts). In order to avoid motor lesion, it is confirmed that no motor response is produced with 2Hz, 2ms (millisecond) and twice the voltage that produced sensitive response. After correct positioning and repositioning the needles if needed, conventional radiofrequency ablation of medial branch nerves is performed using the following settings: 90 seconds, 80º Celsius degrees. The selection of target facet joints is made based on clinical findings. Some patients receive bilateral while other unilateral facet joint denervation.|
|Procedure: Fluoroscopically guided lumbar facet joint injection.|With the patient in prone position and guided by fluoroscopy, lumbar facet joints are identified. The 22 french needles are then advanced aiming to the lumbar facet joints. Correct positioning is confirmed with anteroposterior and lateral fluoroscopy. A mixture of 3 ml of ropivacaine 0,2% + 1 ml (40 mg) of triamcinolone (trigon depot) is prepared. 1 ml of the mixture is injected in each lumbar facet joint through the needles. Four facet joints are selected for therapy. Some patients receive bilateral and other unilateral but contiguous facet joint infiltration. The selection of target facet joints is made based on clinical and radiological findings.|
|Procedure: Fluoroscopically guided lumbar epidural corticosteroid injection.|With the patient in prone position and guided by fluoroscopy, an epidural needle attached to a syringe filled with saline serum is advanced through the interlaminar approach using a loss of resistance technique for the identification of the lumbar epidural space. When loss of resistance is encountered, 1 ml of iodinated contrast is injected. After fluoroscopical confirmation of epidural spilling, a mixture of 4 ml of ropivacaine 0,1%, 2 ml (12 mg) of betamethasone and 2 ml of saline serum is injected in the epidural space. The lumbar level to which it infiltrates depends on each patient.|
|Procedure: Fluoroscopically guided caudal epidural corticosteroid injection.|With the patient in prone position and guided by fluoroscopy, an epidural needle attached to a syringe filled with saline serum is advanced through the sacral hiatus using a loss of resistance technique for the identification of the epidural space. When loss of resistance is encountered, 2 ml of iodinated contrast is injected. After fluoroscopical confirmation of epidural spilling, a mixture of 7 ml of ropivacaine 0,2%, 2 ml (12 mg) of betamethasone and 7 ml of saline serum is injected in the epidural space.|
|Procedure: Fluoroscopically guided pulsed radiofrequency of the lumbar dorsal root ganglion.|With the patient in prone position and guided by fluoroscopy, a 18 gauge needle is advanced aiming to the intervertebral foramen. Patient is cautioned about the paresthesia which will be felt. A lateral view was taken occasionally to confirm position. 0.5 ml of iodinated contrast is injected to confirm the position of the needle. Then 1 ml of the combination of 12mg of betamethasone and 1ml of ropivacaine 0.2% is injected over the affected root. Then, the needle is attached to the radiofrequency device. Correct positioning of the needles is confirmed also by sensitive stimulation (paresthesia evocation) with the following settings: 50 Hz, 1ms, 0,6V. In order to avoid motor lesion, it is confirmed that no motor response is produced with 2Hz, 2ms and twice the voltage that produced sensitive response. After correct positioning is confirmed, pulsed radiofrequency ablation of lumbar dorsal root ganglion is performed using the following settings: 4 minutes, 42ºC (degrees Celsius).|
|Procedure: Fluoroscopically guided transforaminal epidural corticosteroid injection or lumbar selective root block.|With the patient in prone position and guided by fluoroscopy, a 22 french needle is then advanced aiming to the intervertebral foramen. Patient is cautioned about the paresthesia which will be felt along the course of the lumbar root when the needle touches the nerve. A lateral view was taken occasionally to confirm position. 0.5 ml of iodinated contrast is injected to confirm the position of the needle. Then 1 ml of the combination of 12mg of betamethasone and 1ml of ropivacaine 0.2% is injected over the affected root.|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Clinical response to IPMT after 4 weeks follow-up after the IPMT is performed (composite outcome) | Clinical response after 4 week follow-up is going to be defined as composite outcomes: Positive strong response (PSR-4W): a positive strong response to the interventional pain management therapy after 4 weeks follow-up is defined as a composite outcome. Patients must meet both the following criteria: A decrease in Numeric Rating Scale of at least 3 points. A decrease in the Oswestry Disability Index of al least 40%. Positive moderate response (PMR-4W): a positive moderate response to the interventional pain management therapy after 4 weeks follow-up is defined as a composite outcome. Patients must meet both the following criteria: A decrease in Numeric Rating Scale of at least 2 points. A decrease in the Oswestry Disability Index of al least 20%. No response (NR-4W): no response to IPMT after 4 weeks follow-up is defined as those patients not included in either of the previous categories. | Baseline (prior to the Interventional Pain Management Therapy); Week 4 after IPMT | 
| Factors that may be associated with no response to the IPMT at 4 weeks follow-up. | 14 candidate variables will be analyzed for association to no response to the IPMT at 4 weeks (NR-4W). All the variables are qualitative, dichotomic, yes/no: Work sick leave. Depression/Anxiety. Obesity. Existence of another chronic pain. Failed back surgery syndrome. Radicular compression in imaging. Herniated disc in imaging. Radiate pain. Age: older than 65 years old (>65 years old). Chronic therapy with opioid medication. Chronic therapy with gabapentionids. Chronic therapy with opioid medication AND gabapentinoids. Clinical Frailty Scale >3 (≥4). Initial Oswestry Disability Index ≥40. | Response will be measured after 4 weeks follow-up after the IPMT. | 
| Factors that may be associated with a positive response to the IPMT (PSR-4W or PMR-4W). | 14 candidate variables will be analyzed for association to PSR-4W or PMR-4W to the IPMT at 4 weeks. All the variables are qualitative, dichotomic, yes/no: Working. Depression/Anxiety. Obesity. Failed back surgery syndrome. Radicular compression in imaging. Herniated disc in imaging. Radiate pain. Age: younger than 45 years old (<45 years old). Chronic therapy with opioid medication. Chronic therapy with gabapentinoids medication. Chronic therapy with opioid medication AND gabapentinoids. Clinical Frailty Scale <3. Initial Oswestry Disability Index ≥40. Subjective good subjective result in previous performed interventional pain management therapies. | Response will be measured after 4 weeks follow-up. | 
| Clinical response to IPMT after 24 weeks follow-up after the IPMT is performed (composite outcome). | Clinical response after 24 week follow-up is going to be defined as composite outcomes: Positive strong response (PSR-24W): a positive strong response to the interventional pain management therapy after 24 weeks follow-up is defined as a composite outcome. Patients must meet both the following criteria: A decrease in Numeric Rating Scale of at least 3 points. A decrease in the Oswestry Disability Index of al least 40%. Positive moderate response (PMR-24W): a positive moderate response to the interventional pain management therapy after 24 weeks follow-up is defined as a composite outcome. Patients must meet both the following criteria: A decrease in Numeric Rating Scale of at least 2 points. A decrease in the Oswestry Disability Index of al least 20%. No response (NR-24W): no response to IPMT after 24 weeks follow-up is defined as those patients not included in either of the previous categories. | Response will be measured after 24 weeks follow-up after the IPMT. | 
| Factors that may be associated with no response to the IPMT at 24 weeks follow-up. | 14 candidate variables will be analyzed for association to no response to the IPMT at 24 weeks (NR-24W). All the variables are qualitative, dichotomic, yes/no: Work sick leave. Depression/Anxiety. Obesity. Existence of another chronic pain. Failed back surgery syndrome. Radicular compression in imaging. Herniated disc in imaging. Radiate pain. Age: older than 65 years old (>65 years old). Chronic therapy with opioid medication. Chronic therapy with gabapentinoids medication. Chronic therapy with opioid medication AND gabapentinoids. Clinical Frailty Scale >3 (≥4). Initial Oswestry Disability Index ≥40. | The factors will be recorded at baseline; the response will be measured at after 24 weeks follow-up. | 
| Factors that may be associated with a positive response to the IPMT after a 24 weeks follow-up (PSR-24W or PMR-24W). | 14 candidate variables will be analyzed for association to PSR-4W or PMR-4W to the IPMT at 24 weeks. All the variables are qualitative, dichotomic, yes/no: Working. Depression/Anxiety. Obesity. Failed back surgery syndrome. Radicular compression in imaging. Herniated disc in imaging. Radiate pain. Age: younger than 45 years old (<45 years old). Chronic therapy with opioid medication. Chronic therapy with gabapentinoids medication. Chronic therapy with opioid medication AND gabapentinoids. Clinical Frailty Scale <3. Initial Oswestry Disability Index ≥40. Good subjective result in previous performed interventional pain management therapies. | Response will be measured after 24 weeks follow-up after the IPMT. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Validation a predictive model for positive response to the IPMT after 4 weeks | In case that several predictive variables are identified, a predictive model will be developed, either for predicting good and/or bad response. | Response will be measured after 4 weeks follow-up after the IPMT. | 
| Validation a predictive model for positive response to the IPMT after 24 weeks | In case that several predictive variables are identified, a predictive model will be developed, either for predicting good and/or bad response. | Response will be measured after 24 weeks follow-up after the IPMT. | 
| Identifying other variables that may be associated with a good or bad response to an interventional pain management therapy (IPMT) at 4 weeks | Other variables recorded in the Data Collection Logbook of our study will be analyzed looking for other associations: Fibromyalgia. Depression, anxiety and/or mixed axiety-depressive disorder. Obesity. Other chronic pain. Failed back surgery syndrome. Osteoporotic fracture. Lumbar canal stenosis syndrome. Irradiated pain to leg. Diabetes Mellitus. Arthrosis. Inflammatory arthritis. Oncologic condition. Osteoporosis. Substance abuse disorder. | Response will be measured after 4 weeks follow-up after the IPMT | 
| Identifying other variables that may be associated with a good or bad response to an interventional pain management therapy (IPMT) at 24 weeks | Other variables recorded in the Data Collection Logbook of our study will be analyzed looking for other associations: Fibromyalgia. Depression, anxiety and/or mixed axiety-depressive disorder. Obesity. Other chronic pain. Failed back surgery syndrome. Osteoporotic fracture. Lumbar canal stenosis syndrome. Irradiated pain to leg. Diabetes Mellitus. Arthrosis. Inflammatory arthritis. Oncologic condition. Osteoporosis. Substance abuse disorder. | Response will be measured after 24 weeks follow-up after the IPMT | 
| Analyzing the response after 4 weeks to therapy of each interventional pain management therapy alone, and which variables may be associated with a better response to therapy. | The therapies that will be analyzed are: Fluoroscopically guided lumbar medial branch nerve radiofrequency denervation. Fluoroscopically guided lumbar facet joint injection. Fluoroscopically guided lumbar epidural corticosteroid injection. Fluoroscopically guided caudal epidural corticosteroid injection. Fluoroscopically guided pulsed radiofrequency of the lumbar dorsal root ganglion. Fluoroscopically guided transforaminal epidural corticosteroid injection or lumbar selective root block. | Response will be measured after 4 weeks follow-up after the IPMT | 
| Analyzing the response after 24 weeks to therapy of each interventional pain management therapy alone, and which variables may be associated with a better response to therapy. | The therapies that will be analyzed are: Fluoroscopically guided lumbar medial branch nerve radiofrequency denervation. Fluoroscopically guided lumbar facet joint injection. Fluoroscopically guided lumbar epidural corticosteroid injection. Fluoroscopically guided caudal epidural corticosteroid injection. Fluoroscopically guided pulsed radiofrequency of the lumbar dorsal root ganglion. Fluoroscopically guided transforaminal epidural corticosteroid injection or lumbar selective root block. | Response will be measured after 24 weeks follow-up after the IPMT | 
| Studying the association between main clinical diagnosis and the response to therapy, globally and stratified by single IPMT, after 4 weeks of the IPMT | Main clinical diagnosis, response to therapy and IPMT performed are described separately as outcomes. | Response will be measured after 4 weeks follow-up after the IPMT | 
| Studying the association between main clinical diagnosis and the response to therapy, globally and stratified by single IPMT, after 24 weeks of the IPMT | Main clinical diagnosis, response to therapy and IPMT performed are described separately as outcomes. | Response will be measured after 24 weeks follow-up after the IPMT | 
| Studying the satisfaction of the patients to the IPMT performed, after 24 weeks of IPMT | Patient satisfaction will be assessed as two separate YES/NO questions: Are you satisfied with the pain-relief obtained after you underwent the Interventional Pain Management Technique? (YES/NO answer). Based on your experience, would you undergo the same treatment again? (YES/NO answer). | Satisfaction will be measured after 24 weeks follow-up after the IPMT | 
| Studying the satisfaction of the patients to the IPMT performed, after 4 weeks of IPMT | Patient satisfaction will be assessed as two separate YES/NO questions: - Are you satisfied with the pain-relief obtained after you underwent the Interventional Pain Management Technique? (YES/NO answer). Patient satisfaction will be assessed as two separate YES/NO questions: Are you satisfied with the pain-relief obtained after you underwent the Interventional Pain Management Technique? (YES/NO answer). Based on your experience, would you undergo the same treatment again? (YES/NO answer). | Satisfaction will be measured after 4 weeks follow-up after the IPMT | 
| Studying the correlation of both scales (Numeric Rating Scale and Oswestry Disability Index) and patient satisfaction after 4 weeks of the IPMT | Patient satisfaction will be assessed as two separate YES/NO questions: Are you satisfied with the pain-relief obtained after you underwent the Interventional Pain Management Technique? (YES/NO answer). Based on your experience, would you undergo the same treatment again? (YES/NO answer). | Response and satisfaction will be measured after 4 weeks follow-up after the IPMT | 
| Studying the correlation of both scales (Numeric Rating Scale and Oswestry Disability Index) and patient satisfaction after 24 weeks of the IPMT | Patient satisfaction will be assessed as two separate YES/NO questions: Are you satisfied with the pain-relief obtained after you underwent the Interventional Pain Management Technique? (YES/NO answer). Based on your experience, would you undergo the same treatment again? (YES/NO answer). | Response and satisfaction will be measured after 24 weeks follow-up after the IPMT | 
| Studying the epidemiology and evolution of the pharmacological therapy of our population (Part I) | Variable #1. Qualitative; is the patient taking any of the following medications (YES/NO for each treatment) at visit 0?: Acetanomiphen. Metamizole. NSAID #1 (specify which). NSAID #1 (specify which). Gabapentine. Pregabaline. Tramadol. Tapentadol. Oxicodone. Metadone. Transdermic Fentanyl. Transdermic Buprenorphine. Amitriptiline. Desipramine. Nortriptiline. Duloxetine. Desvenlafaxine. Paroxetine. Citalopram. Transdermic lidocaine. Transdermic capsaicine. Benzodiacepine (specify which). Dexametasone. Prednisone. Hidrocodone. Hidromorphone. Oximorphine. Minalcipram. Bupropion. Valproate. Carbamazepine. Lamotrigine. Other (1) (specify which). Other (2) (specify which). Other (3) (specify which). Variable #2. Quantitative. 24 hour dose of each pharmacologic treatment the patient is taking at visit 0. | Drug therapy will be recorded at baseline | 
| Studying the epidemiology and evolution of the pharmacological therapy of our population (Part II) | Variable #3. Qualitative. Is the patient taking any pharmacological treatment belonging to any of the following cathegories?: NSAIDs, acetanomiphen, metamizole. Opioids. Oral opioids. Minor opioids (tramadol, tapendatol, codeine) Strong opioids. Transdermic opioids. Gabapentinoids. Antidepressants. Benzodiazepines. Anticonvulsivants. Variable #4. Qualitative. Has it been any change in pharmacological treatment in the follow-up (baseline vs 4 weeks and vs 24 weeks) ; related to each pharmacological treatment)?: Unchanged. Higher dose. Lower dose. Treatment stopped. Variable #5. Qualitative. Why was the pharmacological treatment changed (baseline vs 4 weeks and vs 24 weeks) ?: Clinical improvement. Secondary effects. Change for another pharmacological treatment. | Drug therapy will be recorded at baseline; change in therapy will be recorded vs 4 weeks and vs 24 weeks. | 
| Studying the safety and potential adverse reactions to IPMT. | Several cathegories: Postdural puncture headache. Infectious complication. Epidural hematoma. Neurologic damage. Other (specify). | Potential adverse reactions will be measured at the end of follow-up (after 24 weeks of the IPMT) | 
| Studying the epidemiology of radiological findings in our population, and its association with the IPMT performed and the response to therapy after 4 weeks. | Several cathegories or radiological findings: Discopathy. Herniated disk. Central stenosis. Lateral stenosis. Radicular compression. Spondyloarthrosis. Spondylolisthesis. Epidural fibrosis. Reumatic inflammatory disease. Vertebral compression fracture. Scoliosis. Other (specify). | Response will be measured after 4 weeks follow-up after the IPMT | 
| Studying the epidemiology of radiological findings in our population, and its association with the IPMT performed and the response to therapy after 24 weeks. | Several cathegories or radiological findings: Discopathy. Herniated disk. Central stenosis. Lateral stenosis. Radicular compression. Spondyloarthrosis. Spondylolisthesis. Epidural fibrosis. Reumatic inflammatory disease. Vertebral compression fracture. Scoliosis. Other (specify). | Response will be measured after 24 weeks follow-up after the IPMT | 
| Studying the epidemiology of radiological findings in our population, and its association with clinical findings and clinical diagnosis. | Several cathegories: Discopathy. Herniated disk. Central stenosis. Lateral stenosis. Radicular compression. Spondyloarthrosis. Spondylolisthesis. Epidural fibrosis. Reumatic inflammatory disease. Vertebral compression fracture. Scoliosis. Other (specify). Clinical findings are: Fibromyalgia. Failed back surgery syndrome. Osteoporotic fracture. Lumbar canal stenosis syndrome. Irradiated pain to leg. Arthrosis. Inflammatory arthritis. Oncologic condition. Osteoporosis. Clinical diagnosis are defined as another outcome measure. | Response will be measured after 24 weeks follow-up after the IPMT | 
| Analyzing the epidemiology of comorbidities (pain and not pain related) in our population: | Comorbities that will be analyzed are: Fibromyalgia. Depression, anxiety and/or mixed axiety-depressive disorder. Obesity. Other chronic pain. Failed back surgery syndrome. Osteoporotic fracture. Lumbar canal stenosis syndrome. Irradiated pain to leg. Diabetes Mellitus. Arthrosis. Inflammatory arthritis. Oncologic condition. Osteoporosis. Substance abuse disorder. | Comorbidites will be recorded at baseline | 
| Analyzing the demographical data of the study population. | Age, sex, marital status, working status at ethnic group and Medical Specialty that derivated the patient to our unit will be recorded at base line. Working status: It will classified as: active worker, work sick leave, studying, retired person, incapacitated to work and convict Marital status: It will classified as: single, unmarried partner, married, divorced and widowed. Ethnic group: It will be classified as: caucasic, african; latin, asiatic, romany and other. | Demographical data will be obtained at baseline | 
| Studying the evolution in time of the response to the IPMT. | Positive strong response, both strong (PSR) and moderate (PMR), as defined in Primary outcomes will be measured both at baseline vs 4 weeks follow-up, baseline vs 24 weeks follow-up and baseline vs 8 weeks follow-up. The evolution of the pain response will be studied; response and satisfaction will be measured at 4 different moments: Baseline (prior to the performance of the IPMT). 4 weeks after the IPMT is performed. 8 weeks after the IPMT is performed. 24 weeks after the IPMT is performed. | the response will be measured at +4weeks, +8weeks and +24 weeks | 
| Charlson comorbidity index | Charlson comorbidity index will be calculated at baseline. | Calculated at baseline | 
| Pain syndrome | Variable 1: presence of any of the following diagnosis: Facet joint syndrome. Vertebral crush fracture. Discogenic pain. Lateral lumbar canal stenosis. Sacroiliac pain syndrome. Central lumbar canal stenosis. Failed back surgery syndrome. None of the previous diagnosis. Variable n 2. Main pain syndrome, which is the one that motivates the IPMT. Facet joint syndrome. Vertebral crush fracture. Discogenic pain. Lateral lumbar canal stenosis. Sacroiliac pain syndrome. Central lumbar canal stenosis. Failed back surgery syndrome. None of the previous diagnosis. There is no main pain syndrome: the patient has multiple pain diagnosis, and no single one prevails among the others. The IPMT is under a mixed therapeutic and diagnostic approach. Variable n3: number of pain syndromes present in the patient, of all the above. | Pain syndrome is diagnosed at baseline | 
| Main operator of the IPMT | Two cathegories: Attending Pain Physician. Anestesiology Resident. | Measured 4 weeks after IPMT is performed | 
| Previous treatments, and success | Variables n1 and n 2 are qualitative. Measured at visit 0. Variable n 1: the patient has undergone any of these treatments: Back surgery. Previous IPMT. No IPMT. Variable n 2: subjective satisfaction of the patient: Satisfied. Not satisfied. | Measured at baseline | 
| Numeric Rating Scale of pain at baseline | The 11-point numerical pain rating scale (NRS) is a measure of pain in which patients rate their pain ranging from 0 (no pain) to 10 (worst imaginable pain). Validated in Childs JD, Piva SR, Fritz JM. Responsiveness of the numeric pain rating scale in patients with low back pain. Spine 2005;30:1331-4. | baseline | 
| Numeric Rating Scale of pain at 4 weeks after the IPMT is performed | The 11-point numerical pain rating scale (NRS) is a measure of pain in which patients rate their pain ranging from 0 (no pain) to 10 (worst imaginable pain). Validated in Childs JD, Piva SR, Fritz JM. Responsiveness of the numeric pain rating scale in patients with low back pain. Spine 2005;30:1331-4. | 4 weeks after the IPMT is performed | 
| Numeric Rating Scale of pain at 8 weeks after the IPMT is performed | The 11-point numerical pain rating scale (NRS) is a measure of pain in which patients rate their pain ranging from 0 (no pain) to 10 (worst imaginable pain). Validated in Childs JD, Piva SR, Fritz JM. Responsiveness of the numeric pain rating scale in patients with low back pain. Spine 2005;30:1331-4. | 8 weeks after the IPMT is performed | 
| Numeric Rating Scale of pain at 24 weeks after the IPMT is performed | The 11-point numerical pain rating scale (NRS) is a measure of pain in which patients rate their pain ranging from 0 (no pain) to 10 (worst imaginable pain). Validated in Childs JD, Piva SR, Fritz JM. Responsiveness of the numeric pain rating scale in patients with low back pain. Spine 2005;30:1331-4. | 24 weeks after the IPMT is performed | 
| Oswestry Disability Index at baseline | Original version 1 (1980), translated and adapted to Spanish (1995), validated. | baseline | 
| Oswestry Disability Index at 4 weeks after the IPMT is performed | Original version 1 (1980), translated and adapted to Spanish (1995), validated. | 4 weeks after the IPMT is performed | 
| Oswestry Disability Index at 8 weeks after the IPMT is performed | Original version 1 (1980), translated and adapted to Spanish (1995), validated. | 8 weeks after the IPMT is performed | 
| Oswestry Disability Index at 24 weeks after the IPMT is performed | Original version 1 (1980), translated and adapted to Spanish (1995), validated. | 24 weeks after the IPMT is performed | 
| Clinical Frailty Scale at baseline | As described by Rockwood K, Song X, MacKnight C, Bergman H, Hogan DB, McDowell I et al. A global clinical measure of fitness and frailty in elderly people. CMAJ 2005;173:489-95. | Obtained at baseline | 
| Previous treatments, and success | Variables n1 and n 2 are qualitative. Measured at visit 0. Variable n 1: the patient has undergone any of these treatments: Back surgery. Previous IPMT. No IPMT. Variable n 2: subjective satisfaction of the patient: Satisfied. Not satisfied. | Mesured at baseline | 
| Interventional Pain Management Technique indicated at visit 0. | Several cathegories: Fluoroscopically guided lumbar medial branch nerve radiofrequency denervation. Fluoroscopically guided lumbar facet joint injection. Fluoroscopically guided lumbar epidural corticosteroid injection. Fluoroscopically guided caudal epidural corticosteroid injection. Fluoroscopically guided pulsed radiofrequency of the lumbar dorsal root ganglion. Fluoroscopically guided transforaminal epidural corticosteroid injection or lumbar selective root block. | Baseline | 
| Interventional Pain Management Technique performed. | Several cathegories: Fluoroscopically guided lumbar medial branch nerve radiofrequency denervation. Fluoroscopically guided lumbar facet joint injection. Fluoroscopically guided lumbar epidural corticosteroid injection. Fluoroscopically guided caudal epidural corticosteroid injection. Fluoroscopically guided pulsed radiofrequency of the lumbar dorsal root ganglion. Fluoroscopically guided transforaminal epidural corticosteroid injection or lumbar selective root block. | Measured 4 weeks after the IPMT | 
| Imaging modality | Qualitative: MRI. ST scan. Lumbar x-ray. | Baseline |