Self reported health status and magnetic resonance imaging findings in patients with low back pain Risk factors for a recurrence of low back pain. Are there indications (other than scoliosis) for rigid orthopaedic brace treatment in chronic, mechanical low back pain? Are first-time episodes of serious LBP associated with new MRI findings? Discographic, MRI and psychosocial determinants of low back pain disability and remission: a prospective study in subjects with benign persistent back pain. Spinal mechanical load: a predictor of persistent low back pain? A prospective cohort study Preliminary Investigation of the Mechanisms Underlying the Effects of Manipulation: Exploration of a Multivariate Model Including Spinal Stiffness, Multifidus Recruitment, and Clinical Findings Potential Risk Factors of Persistent Low Back Pain Developing from Mild Low Back Pain in Urban Japanese Workers Exploring Factors Influencing Low Back Pain in People With Nondysvascular Lower Limb Amputation: A National Survey. Prediction model for unsuccessful return to work after hospital-based intervention in low back pain patients Clinical Study of Low Back Pain and Radicular Pain Pathways by Using L2 Spinal Nerve Root Infiltration: A Randomized, Controlled, Clinical Trial Which Prognostic Factors for Low Back Pain Are Generic Predictors of Outcome Across a Range of Recovery Domains?
Abstract The authors present a prospect i ve study of quality of life ( SF-36 ) and MRI findings in patients with low back pain ( LBP ) . Disc herniation and nerve root compression contribute to LBP and poor quality of life . However , significant proportions of asymptomatic subjects have disc herniation and neural compromise . Little is known about the influence of disc abnormalities and neural compression on quality of life in symptomatic patients . The purpose of this study was to assess the relationship between the extent of disc abnormality , neural impingement and quality of life . A total of 317 consecutive patients with LBP referred for MRI completed an SF-36 health status question naire immediately before imaging and again 6 months later . Patients were grouped according to the most extensive disc abnormality and any neural compromise reported at MRI . The relationship between symptoms , radiological signs and SF-36 scores was assessed . Eighty percent ( 255/317 ) and 65 % ( 205/317 ) of patients completed the initial and 6-month SF-36 , respectively . Thirty-six percent of patients ( 115/317 ) had one or more herniated discs and 44 % ( 140/317 ) had neural impingement . There was little relationship between the extent of disc abnormality and quality of life . Patients with radiological evidence of neural impingement reported better general health ( P < 0.01 ) . SF-36 scores improved at 6 months in four dimensions , but general health deteriorated ( P < 0.01 ) . Patients with neural impingement had improved pain scores at 6 months ( P < 0.05 ) . The study results showed that the pain and dysfunction caused by disc herniation and neural compromise are not sufficiently distinct from other causes of back pain to be distinguished by the SF-36 . Whilst neural compromise may be the best radiological feature distinguishing patients who may benefit from intervention , it can not predict quality of life deficits in the diffuse group of patients with LBP BACKGROUND CONTEXT The clinical importance of lumbar pathology identified on magnetic resonance imaging ( MRI ) remains unclear . It is plausible that pathology seen on MRI is a risk factor for a recurrence of low back pain ( LBP ) ;  however , to our knowledge , this has not been investigated by previous studies . PURPOSE The aim was to investigate whether lumbar pathology , identifiable on MRI , increases the risk of a recurrence of LBP . STUDY DESIGN This was a prospect i ve inception cohort study with 1-year follow-up . PATIENT SAMPLE Seventy-six people who had recovered from an episode of LBP within the previous 3 months were included . OUTCOME MEASURES The primary outcome was time to recurrence of LBP , which was determined by contacting participants at 2-month intervals for 12 months . METHODS All participants underwent a baseline assessment including MRI scan and completion of a question naire , which assessed a range of potential risk factors for recurrence . Magnetic resonance imaging scans were reported for the presence of a range of MRI findings . The primary analysis investigated the predictive value of two clinical features ( age and number of previous episodes ) and six MRI findings ( disc degeneration , high intensity zone , Modic changes , disc herniation , facet joint arthrosis , and spondylolisthesis ) in a multivariate Cox regression model . We decided a priori that dichotomous predictors with hazard ratios ( HRs ) of greater than 1.5 or less than 0.67 would be considered potentially clinical ly important and justify further investigation . RESULTS Of the eight predictors entered into the primary multivariate model , three ( disc degeneration , high intensity zone , and number of previous episodes ) met our a priori threshold for potential importance . Participants with disc degeneration score greater than or equal to 3 ( Pfirrmann scale ) had a HR of 1.89 ( 95 % confidence interval [ CI ] 0.42 - 8.53 ) compared with those without . Patients with high intensity zone had an HR of 1.84 ( 95 % CI 0.94 - 3.59 ) compared with those without . For every additional previous episode , participants had an HR of 1.04 ( 95 % CI 1.02 - 1.07 ) . CONCLUSIONS We identified promising risk factors for a recurrence of LBP , which should be further investigated in larger trials . The findings suggest that pathology seen on MRI plays a potentially important role in recurrence of LBP OBJECTIVES Mechanical low back pain ( LBP ) is a major public health problem . Today 's st and ard care strategy involves a combination of drug-based and non-drug therapies . The use of conservative orthopaedic brace treatment is subject to debate . The lack of data and consensus in the literature on the value of this treatment in chronic LBP prompted to us to seek to estimate the modalities and indications for brace use in France . MATERIAL S AND METHOD We performed a question naire-based survey of physician members of the French Society of Physical Medicine and Rehabilitation ( SOFMER ) . RESULTS We received 55 completed question naires . Although the indications for this treatment were very heterogeneous ( in both clinical and para clinical terms ) , the prescribing behaviour was rather uniform . The brace is worn during the day for less than 3 months ( with a progressive reduction in use over 1 to 2 months ) , together with physiotherapy before and after immobilization . The patient keeps the brace at the end of the treatment period . Orthopaedic treatment appears to be prescribed in many chronic LBP situations . Analysis of spinal posture and magnetic resonance imaging results ( and Modic changes in particular ) influence the therapeutic decisions . CONCLUSION Clinical and para clinical indications of this treatment must be precisely defined and evaluated in prospect i ve , multicenter studies with homogeneous cohorts BACKGROUND Magnetic resonance ( MR ) imaging is frequently used to evaluate first-time episodes of serious low back pain ( LBP ) . Common degenerative findings are often interpreted as recent developments and the probable anatomic cause of the new symptoms . To date no prospect i ve study has established a baseline MR status of the lumbar spine in subjects without significant LBP problems and prospect ively surveyed these subjects for acute changes shortly after new and serious LBP episodes . This method can identify new versus old MR findings possibly associated with the acute symptomatic episode . PURPOSE To determine if new and serious episodes of LBP are associated with new and relevant findings on MRI . STUDY DESIGN Prospect i ve observational study with baseline and post-LBP MRI monitoring of 200 subjects over 5 years . OUTCOME MEASURES Clinical outcomes : LBP intensity ( visual analogue scale ) , Oswestry Disability Index , and work loss . MRI outcomes : disc degeneration , herniation , annular fissures , end plate changes , facet arthrosis , canal stenosis , spondylolisthesis , and root impingement . METHODS 200 subjects with a lifetime history of no significant LBP problems , and a high risk for new LBP episodes were studied at baseline with physical examination , plain radiographs , and MR imaging . Subjects were followed every 6 months for 5 years with a detailed telephone interview . Subjects with a new severe  LBP episode ( LBP > or=6/10,>1 week ) were assessed for new diagnostic tests . New MR imaging , taken within 6 to 12 weeks of the start of a new LBP episode , was compared with baseline ( asymptomatic ) images . Two independent and blinded readers evaluated each baseline and follow-up study . RESULTS During the 5-year observation period of 200 subjects , 51 ( 25 % ) subjects were evaluated with a lumbar MRI for clinical ly serious LBP episodes , and 3/51 ( 6 % ) had a primary radicular complaint . These 51 subjects had 67 MR scans . Of 51 subjects , 43 ( 84 % ) had either unchanged MR or showed regression of baseline changes . The most common progressive findings were disc signal loss ( 10 % ) , progressive facet arthrosis ( 10 % ) , or increased end plate changes ( 4 % ) . Only two subjects , both with primary radicular complaints , had new findings of probable clinical significance ( 4 % ) . Subjects having another MR were more likely to have had chronic pain at baseline ( odds ratio [OR]=3.19 ; 95 % confidence interval [ CI ] 1.61 - 6.32 ) , to smoke ( OR=5.81 ; 95 % CI 1.99 - 16.45 ) , have baseline psychological distress ( OR 2.27 ; 95 % CI 1.15 - 4.49 ) , and have previous disputed compensation cl aims ( OR=2.35 ; 95 % CI 0.97 - 5.69 ) . Subjects involved in current compensation cl aims were also more likely to have an MR scan to evaluate the LBP episode ( risk ratio=4.75 , p<.001 ) , but were unlikely to have significant new findings . New findings were not more frequent in subjects with LBP episodes developing after minor trauma than when LBP developed spontaneously . CONCLUSION Findings on MR imaging within 12 weeks of serious LBP inception are highly unlikely to represent any new structural change . Most new changes ( loss of disc signal , facet arthrosis , and end plate signal changes ) represent progressive age changes not associated with acute events . Primary radicular syndromes may have new root compression findings associated with root irritation BACKGROUND CONTEXT A range of morphologic and psychosocial variables has been suggested as risk factors for serious low back pain ( LBP ) illness . Although the relative contributions of structural and psychosocial variables are intensely debated , the validity of differing hypotheses has proven difficult to test because the incidence of serious disabling LBP illness is low in healthy subjects . These factors dictate the requirement for large sample sizes , extensive structural imaging and extended longitudinal study . Previous studies included either small cohorts with intensive imaging testing or large population studies that do not establish a detailed morphologic baseline . PURPOSE To establish , using a strict patient sample design , the relative contribution of structural and psychosocial determinants of serious LBP illness among subjects with no previous LBP disability or clinical LBP illness . STUDY DESIGN / SETTING A prospect i ve , longitudinal study of subjects with high risk factors for serious LBP as determined by structural and psychosocial characteristics . PATIENT SAMPLE One hundred subjects with known mild persistent low back pain and a 2:1 ratio of chronic ( non-lumbar ) pain syndrome were recruited from a study population with a predisposition to disc degenerative disease , to undergo baseline examination , testing and 5-year follow-up . OUTCOME MEASURES Observations were made at 6-month intervals over 4 to 6 years ( mean , 5.3 ) for the after primary outcomes measures : episodes of serious back pain ( visual analogue scale [ VAS ] > or = 6 ) , episodes of occupational disability less than 1 week , episodes of occupational disability for 1 week , remission episodes of all back pain symptoms at least 6 months and medical visits primarily for LBP evaluation and treatment . METHODS Lumbar magnetic resonance imaging ( MRI ) , lumbar provocative discography ( in psychometrically normal subjects ) , physical examinations , medical and work histories and psychometric testing were performed at baseline . Imaging and psychometric testing were grade d by blinded examiners . A scripted interview was conducted every 6 months during follow-up by independent research assistants who also were blinded to patient baseline data . The interview covered interval medical , occupational and accident or injury histories . RESULTS Psychosocial variables strongly predicted both long- and short-term disability events , duration and health-care visits for LBP problems ( p<0.0001 - 0.004 ) . The likelihood of a sustained remission from the baseline persistent ( sub clinical ) LBP appeared to be linked to occupation factors ( leaving a heavy labor occupation ; p=0.0001 ) , neurophysiologic variables ( chronic nonlumbar pain ; p=0.0002 ) and psychometric profiles at baseline ( DRAM and FABQ-PA ; p=0.003 - 0.002 ) . Of the structural findings measured only moderate or severe Modic changes of the vertebral end plate were weakly associated with an adverse outcome . A positive provocative discogram at baseline did not predict any future adverse event . CONCLUSION The development of serious LBP disability in a cohort of subjects with both structural and psychosocial risk factors was strongly predicted by baseline psychosocial variables . Structural variables on both MRI and discography testing at baseline had only weak association with back pain episodes and no association with disability or future medical care Prospect i ve inception cohort . To assess the prognostic value of spinal mechanical load , assessed with the 24-hour schedule ( 24HS ) , in subjects with acute non-specific low back pain ( ALBP ) and to examine the influence of spinal mechanical load on the course of ALBP . In view of the characteristics of the natural course of ALBP , this should be viewed as a persistent condition in many patients rather that a benign self-limiting disease . Therefore , secondary prevention could be beneficial . Spinal mechanical load is a risk factor for ALBP and possibly a ( modifiable ) prognostic factor for persistent ( i.e. recurrent and /or chronic ) LBP . One hundred patients from primary care with ALBP were eligible for inclusion . At 6 months , 88 subjects completed the follow-up . For the follow-up assessment a research assistant , unaware of our interest in the prognostic factors , contacted the subjects by telephone . Question naires were completed focusing on changes in demographic data and on the course and current status of ALBP . Persistent LBP occurred in 60 % subjects . After multivariate regression analysis smoking ( harmful ) and advanced age ( protective ) were associated with persistent LBP . Differences in 24HS scores at baseline and follow-up were univariate-related to persistent LBP . Spinal mechanical load , quantified with the 24HS , is not a prognostic factor for persistent LBP . Modification of spinal mechanical load in terms of 24HS scores could be beneficial for secondary prevention in patients with acute LBP Study Design . Prospect i ve case series . Objective . To examine spinal stiffness in patients with low back pain ( LBP ) receiving spinal manipulative therapy ( SMT )  , evaluate associations between stiffness characteristics and clinical outcome , and explore a multivariate model of SMT mechanisms as related to effects on stiffness , lumbar multifidus ( LM ) recruitment , and status on a  clinical prediction rule  ( CPR ) for SMT outcomes . Summary of Background Data . Mechanisms underlying the clinical effects of SMT are poorly understood . Many explanations have been proposed , but few studies have related potential mechanisms to clinical outcomes or considered multiple mechanisms concurrently . Methods . Patients with LBP were treated with two SMT sessions over 1 week . CPR status was assessed at baseline . Clinical outcome was based on the Oswestry disability index ( ODI ) . Mechanized indentation measures of spinal stiffness and ultrasonic measures of LM recruitment were taken before and after each SMT , and after 1 week . Global and terminal stiffness were calculated . Multivariate regression was used to evaluate the relationship between stiffness variables and percentage ODI improvement . Zero-order correlations among stiffness variables , LM recruitment changes , CPR status , and clinical outcome were examined . A path analysis was used to evaluate a multivariate model of SMT effects . Results . Forty-eight patients ( 54 % women ) had complete stiffness data . Significant immediate decreases in global and terminal stiffness occurred post-SMT regardless of outcome . ODI improvement was related to greater immediate decrease in global stiffness ( P = 0.025 ) , and less initial terminal stiffness ( P = 0.01 ) . Zero-order correlations and path analysis supported a multivariate model suggesting that clinical outcome of SMT is mediated by improvements in LM recruitment and immediate decrease in global stiffness . Initial terminal stiffness and CPR status may relate to outcome though their relationship with LM recruitment . Conclusion . The underlying mechanisms explaining the benefits of SMT appear to be multifactorial . Both spinal stiffness characteristics and LM recruitment changes appear to play a role Study Design Two-year , prospect i ve cohort data from the Japan epidemiological research of occupation-related back pain study in urban setting s were used for this analysis . Objective To examine the association between aggravated low back pain and psychosocial factors among Japanese workers with mild low back pain . Summary of Background Data Although psychosocial factors are strongly indicated as yellow flags of low back pain ( LBP ) leading to disability , the association between aggravated LBP and psychosocial factors has not been well assessed in Japanese workers . Methods At baseline , 5,310 participants responded to a self-administered question naire including questions about individual characteristics , ergonomic work dem and s , and work-related psychosocial factors ( response rate : 86.5 % ) , with 3,811 respondents completing the 1-year follow-up question naire . The target outcome was aggravation of mild LBP into persistent LBP during the follow-up period . Incidence was calculated for the participants with mild LBP during the past year at baseline . Logistic regression was used to explore risk factors associated with persistent LBP . Results Of 1,675 participants who had mild LBP during the preceding year , 43 ( 2.6 % ) developed persistent LBP during the follow-up year . Multivariate analyses adjusted for individual factors and an ergonomic factor found statistically significant or almost significant associations of the following psychosocial factors with persistent LBP : interpersonal stress at work [ adjusted odds ratio ( OR ) : 1.96 and 95 % confidence interval ( 95%CI ) : 1.00–3.82 ] , job satisfaction ( OR : 2.34 , 95%CI : 1.21–4.54 ) , depression ( OR : 1.92 , 95%CI : 1.00–3.69 ) , somatic symptoms ( OR : 2.78 , 95%CI : 1.44–5.40 ) , support from supervisors ( OR : 2.01 , 95%CI : 1.05–3.85 ) , previous sick-leave due to LBP ( OR : 1.94 , 95%CI : 0.98–3.86 ) and family history of LBP with disability ( OR : 1.98 , 95%CI : 1.04–3.78 ) . Conclusions Psychosocial factors are important risk factors for persistent LBP in urban Japanese workers . It may be necessary to take psychosocial factors into account , along with physical work dem and s , to reduce LBP related disability BACKGROUND Chronic low back pain ( LBP ) is a common musculoskeletal impairment in people with lower limb amputation . Given the multifactorial nature of LBP , exploring the factors influencing the presence and intensity of LBP is warranted . OBJECTIVE To investigate which physical , personal , and amputee-specific factors predicted the presence and intensity of LBP in persons with nondysvascular transfemoral amputation ( TFA ) and transtibial amputation ( TTA ) . DESIGN A retrospective cross-sectional survey . SETTING A national r and om sample of people with nondysvascular TFA and TTA . PARTICIPANTS Participants ( N = 526 ) with unilateral TFA and TTA due to nondysvascular etiology ( ie , trauma , tumors , and congenital causes ) and a minimum prosthesis use of 1 year since amputation were invited to participate in the survey . The data from 208 participants ( 43.4 % response rate ) were used for multivariate regression analysis . METHODS ( INDEPENDENT VARIABLES ) Personal ( ie , age , body mass , gender , work status , and presence of comorbid conditions ) , amputee-specific ( ie , level of amputation , years of prosthesis use , presence of phantom-limb pain , residual-limb problems , and nonamputated limb pain ) , and physical factors ( ie , pain-provoking postures including st and ing , bending , lifting , walking , sitting , sit-to-st and , and climbing stairs ) . MAIN OUTCOME MEASURES ( DEPENDENT VARIABLES ) LBP presence and intensity . RESULTS A multivariate logistic regression model showed that the presence of 2 or more comorbid conditions ( prevalence odds ratio [ POR ] = 4.34 , P = .01 ) , residual-limb problems ( POR = 3.76 , P < .01 ) , and phantom-limb pain ( POR = 2.46 , P = .01 ) influenced the presence of LBP . Given the high LBP prevalence ( 63 % ) in the study , there is a tendency for overestimation of POR , and the results must be interpreted with caution . In those with LBP , the presence of residual-limb problems ( β = 0.21 , P = .01 ) and experiencing LBP symptoms during sit-to-st and task ( β = 0.22 , P = .03 ) were positively associated with LBP intensity , whereas being employed demonstrated a negative association ( β = -0.18 , P = .03 ) in the multivariate linear regression model . CONCLUSIONS Rehabilitation professionals should be cognizant of the influence that comorbid conditions , residual-limb problems , and phantom pain have on the presence of LBP in people with nondysvascular lower limb amputation .  Further prospect i ve studies could investigate the underlying causal mechanisms of LBP . LEVEL OF EVIDENCE II Background Many studies on low back pain ( LBP ) have identified prognostic factors , but prediction models for use in secondary health care are not available . The purpose of this cohort study , based on a r and omised clinical study , was to identify risk factors for unsuccessful return to work ( U-RTW ) in sick-listed LBP patients with or without radiculopathy and to vali date a prediction model for U-RTW . Methods 325 sick-listed LBP patients with or without radiculopathy were included in an intervention study and followed for one year . Afterwards , 117 other LBP patients were recruited similarly , included in a validation study and also followed for one year . All patients were subjected to identical procedures and interventions and received a brief intervention by the same rehabilitation doctor and physiotherapist . Half of them received case manager guidance within a multidisciplinary setting . At baseline , they completed a question naire and went through a clinical low-back examination . Sciatica was investigated by magnetic resonance imaging ( MRI ) . U-RTW was registered in a national data base both initially and at 1-year . Results Neither initial U-RTW ( 24.0 % ) nor one-year U-RTW ( 38.2 % ) were statistically significantly different in the two intervention groups nor in patients with and without radiculopathy . Multivariate logistic regression analysis identified two clinical and five psychosocial baseline predictors for one-year U-RTW ( primary outcome ) . The clinical predictors included pain score ( back+leg pain ) and side-flexion . The five psychosocial predictors included ‘ bodily distress ’ ‘ low expectations of RTW ’ , ‘ blaming the work for pain ’ , ‘ no home ownership ’ and ‘ drinking alcohol less than once/month ’ . These predictors were not statistically significantly different in patients with and without radiculopathy , and they also predicted initial U-RTW ( secondary outcome ) . Obesity and older age were only supplementary predictors in patients with radiculopathy . A prediction model was established and tested in the validation study group . The model predicted one-year U-RWT in patients with intermediate and high risk , but only partially in patients with low risk . The model predicted all three risk categories in initial U-RTW . Conclusions A prediction model combining baseline clinical and psychosocial risk factors predicted patients with low , intermediate and high risk for unsuccessful return to work , both initially and at 1-year Study Design . R and omized control trial ( RCT ) for L2 spinal nerve infiltration ( L2 block ) in clinical cases . Objectives . To confirm or refute the effect of L2 block using RCT , and to study the pathway of low back pain ( LBP ) and radicular pain in clinical cases . Summary of Background Data . It has been reported in animal experiments that one of the main pathways of pain originating from the lumbar spine is the sympathetic trunk through the L2 spinal nerve rootvia sympathetic afferents . Methods . To evaluate the effectiveness of L2 block , patients who had LBP and were treated with nonsteroidal anti-inflammatory drugs for at least 2 weeks were then r and omized to the L2 block or control block groups . The intensities of LBP and radicular pain were measured using visual analog scale and face scale before and at 5 minutes and 7 days after the injection . These values were compared , and the effects of the injections on the pain pathway were studied . Results . The average visual analog scale scores for LBP before and at 5 minutes and 7 days after the injection were 69 , 14 , and 44 mm in the L2 block group and 68 , 62 , and 59 mm in the control block group , respectively . After L2 block , 28 patients reported adequate therapeutic effect at 10 weeks , and the effect lasted for more than 24 weeks in 10 of these patients . After control block , 9 patients reported adequate therapeutic effect at 10 and 24 weeks . Conclusion . The LBP and radicular pain pathways were likely interrupted by L2 block . An L2 block is useful in reducing LBP due to the disorders of L2 spinal nerve-innervated structures , such as the disc , facet joint , and sacroiliac joint . However , the therapeutic value of an L2 block may be occasionally insufficient to alleviate pain completely because of the short duration of its ' effect Background Recovery from low back pain ( LBP ) is multidimensional and requires the use of multiple-response ( outcome ) measures to fully reflect these many dimensions . Predictive prognostic variables that are present or stable in all or most predictive models that use different outcome measures could be considered “ universal ” prognostic variables . Objective The aim of this study was to explore the potential of universal prognostic variables in predictive models for 4 different outcome measures in patients with mechanical LBP . Design Predictive modeling was performed using data extracted from a r and omized controlled trial . Four prognostic models were created using backward stepwise deletion logistic , Poisson , and linear regression . Methods Data were collected from 16 outpatient physical therapy facilities in 10 states . All 149 patients with LBP were treated with manual therapy and spine strengthening exercises until discharge . Four different measures of response were used : Oswestry Disability Index and Numeric Pain Rating Scale change scores , total visits , and report of rate of recovery . Results The set of statistically significant predictors was dependent on the definition of response . All regression models were significant . Within both forms of the 4 models , meeting the clinical prediction rule for manipulation at baseline was present in all 4 models , whereas no irritability at baseline and diagnosis of sprains and strains were present in 2 of 4 of the predictive models . Limitations The primary limitation is that this study evaluated only 4 of the multiple outcome measures that are pertinent for patients with LBP . Conclusions Meeting the clinical prediction rule was prognostic for all outcome measures and should be considered a universal prognostic predictor . Other predictive variables were dependent on the outcomes measure used in the predictive model
MRI findings of disc protrusion , nerve root displacement or compression , disc degeneration , and high intensity zone are all associated with LBP , but individually , none of these abnormalities provides a strong indication that LBP is attributable to underlying pathology .
This limits their value in refining epidemiological case definitions for LBP
OBJECTIVE to assess how confidently  low back pain ( LBP ) can be attributed to abnormalities on magnetic resonance imaging ( MRI ) , and thereby explore the potential value of MRI abnormalities in refining case definition for mechanical LBP in epidemiological research .
SUMMARY OF BACKGROUND DATA most epidemiological studies of mechanical LBP have defined cases only by reported symptoms , but it is possible that the potency of causes differs depending on whether there is demonstrable underlying spinal pathology .