Associations Between Back Pain History and Lumbar MRI Findings

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1 Associations Between Back Pain History and Lumbar MRI Findings SPINE Volume 28, Number 6, pp , Lippincott Williams & Wilkins, Inc. Tapio Videman, MD, PhD,* Michele C. Battié, PhD,* Laura E. Gibbons, PhD, Kenneth Maravilla, MD, Hannu Manninen, MD, PhD, and Jaakko Kaprio, MD, PhD Study Design. Retrospective monozygotic twin cohort study. Objectives. Our goal was to investigate the associations between different spinal MRI findings and current, past year, and lifetime low back pain after adjusting for occupational physical loading, smoking, genetics, and early family influences. Summary of Background Data. The role of spinal pathology in back symptoms continues to be controversial. Methods. The study participants consisted of 115 monozygotic male twin pairs 35 to 69 years of age. The qualitatively assessed MRI parameters were as follows: disc height, bulging, herniations, anular tears, osteophytes, spinal stenosis, and endplate changes. Signal intensity was measured quantitatively. Results. After controlling for age, disc height was associated with all back pain variables studied and anular tears with LBP frequency and intensity during the 12 months before imaging. Both were associated with lifetime frequency of low back pain interfering with daily activities, disability, and intensity of the worst lifetime pain episode. Other MRI findings did not explain the various symptom histories. Adjusting for physical loading in the past 12 months increased the associations of anular tears and low back pain today and 12-month low back pain parameters. After controlling for genotype and other familial influences, the within-pair differences in disc height and anular tears accounted for 6% to 12% of the total variance in the within-pair differences of low back pain variables. Conclusion. These findings raise new questions about the underlying mechanisms of LBP. The sensitivities of the only significant MRI parameters, disc height narrowing and anular tears, are poor, and these findings alone are of limited clinical importance. [Key words: anular tears, back pain, disc degeneration, genetics, heredity, spinal disorders, twins] Spine 2003;28: From the *University of Alberta, Edmonton, Alberta, Canada, Finnish Twin Cohort Study, Department of Public Health, University of Helsinki, Helsinki, Finland, University of Washington, Seattle, Washington, Kuopio University Hospital and Kuopio University, Kuopio, Finland, and the Department of Mental Health, National Public Health Institute, Helsinki, Finland. Supported by National Institutes of Health (U.S. grant no. AR 40857), the Ministry of Education, the Finnish Work Environment Fund, the Academy of Finland (grant no ), and the Alberta Heritage Foundation for Medical Research, Canada. Acknowledgment date: June 5, First revision date: August 21, Acceptance date: August 22, The legal regulatory status of the device(s)/drug(s) that is/are the subject of this manuscript is not applicable in my country. Federal and foundation funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence to Tapio Videman, MD, PhD, University of Alberta, Faculty of Rehabilitation Medicine, 3-48 Corbett Hall, Edmonton, Alberta T6G 2G4, Canada; tapio.videman@ualberta.ca It is quite a striking fact, however, that [in] the great majority of those seeking treatment for pains in the back,... in spite of the most careful clinical examination, no pathologic changes can be found This statement by Hirsch and Schajowicz in 1952 also describes today s situation well. Disc pathology has been thought to be the primary culprit in low back pain (LBP) symptoms. 29 Yet, specific pathologic findings in the disc that might underlie these symptoms remain uncertain. Despite this, the disc has continued to be a primary target of diagnostic procedures and therapeutic interventions of the spine. Doubts about disc pathology as a cause of LBP have been fueled by findings of high prevalence of abnormal MRI findings among study participants without LBP. 5,17,34,43 Similar results were reported earlier, based on myelographic and CT scan studies. 15,44 However, there are studies documenting an association between disc pathology and LBP. 3,6,22 Jensen et al compared study participants without and with a history of LBP; 27% versus 54% had a disc protrusion and 1% versus 26% had an extrusion in magnetic resonance imaging (MRI). 18 In a study of back surgery candidates, anular ruptures were highly associated with patients back pain reproduction. 28 In an autopsy study, the study participants with a history of at least 1 month of disabling back pain had more pathology of symmetric disc degeneration, anular ruptures, endplate defects, osteophytes, and facet joint degeneration. However, the only statistically significant difference was for anular ruptures: 60% of those with anular leak in discography had such a history of back pain versus 21% of those without a leak. 42 There are several challenges in studying the associations between spine pathology and LBP. The use of summary variables for disc degeneration can be a problem. If, for example, two or more disc findings reflecting both atrophic and proliferative changes were combined, possible associations between structural findings and pain could be obscured. Therefore, we should use clearly defined structural parameters, when available, in studying the associations of pathology and pain, rather than summary variables. 41 In addition, there are several modifiers for LBP. Physical loading of pathologic structures through materials handling or postures has been shown to exacerbate symptoms. 12,36 This was supported by a linear association between the severity of LBP and heaviness of work, after adjusting for spine pathology in an autopsy study. 42 However, results from functional restoration rehabilitation programs demonstrated no changes in pain experi- 582

2 Back Pain and Lumbar MRI Findings Videman et al 583 ence with increased physical performance. 35 Psychological factors have as much effect on the reporting of different back-related outcomes as physical stress does. 19 The experience and reporting of LBP are dependent on the perceptions and behavior of the individual, but the validity of LBP reporting in relation to LBP experienced needs to be addressed. 20,25 In addition, animal studies have shown that individual differences in both nociceptive and analgesic sensitivity exist. 27 Among humans, variation in pain sensitivity has been attributed to shared environment and familial modeling. 23 Determinants of pressure pain threshold in adult twins provided evidence that shared environmental influences predominate. 24,26 In twin studies, the proportion of variance accounted for by genetic factors has been estimated as 50% for LBP and 21% for sciatica. 4,13 These associations could be explained through physiologic variations of disc degeneration, neurologic mechanisms, and behavioral characteristics. 1,2,27,38 Our goal was to investigate the associations between different spinal MRI findings and current, previous year, and lifetime back pain measures, while controlling for physical loading and some other available factors. Because our study participants were monozygotic twin pairs, we were also able to control for the confounding effects of the combined role of genetics and early family influences. We hypothesized that inconsistencies between current symptoms and current measures of pathology could be expected because the occurrence of back pain varies unpredictably during a lifetime, whereas MRI findings in the spine are cumulative and usually irreversible. Therefore, the strongest association between pathology and LBP could be expected for lifetime pain history, and the weakest for current pain status. In addition, those MRI findings, which are associated with the pathology of innervated disc structures, such as anular tears, ruptures, and herniations, could have a direct association with pain. However, findings in structures without innervation or nonspecific changes, such as nuclear signal intensity and disc height narrowing, would have, if anything, a weak indirect association with previous year and lifetime pain histories. We also hypothesized that disc height narrowing at one or two disc levels, clearly worse than that of neighboring discs, may represent a real trauma leading to disc failure through which innervated scar tissue would be more likely a source of pain than discs with pure ageing changes. Methods Study Participants. The study participants were selected from the Finnish Twin Cohort, which has been described earlier in more detail. 2,21 Questionnaire data from 1975 and 1981 were used to select the monozygotic twin pairs discordant in occupational, leisure time physical activities, driving, or smoking histories. The pairs who appeared to meet these criteria were contacted, and of those solicited, 82% participated. The study participants consisted of the 230 males from 35 to 69 years of age (mean 49.4 years). Table 1. Means and Standard Deviations for Occupational and Other Physical Exposures Variable Mean (SD) Mean-weighted lifetime occupational loading 2.5 (0.9) score (1 4) Years with physically-demanding leisure-time 1.7 (6.3) activities at least twice a week Smoking (yrs packs/day) 14.9 (17.7) Mean-weighted frequency/wk of endurance 1.2 (2.0) sports and activities, age 20 yrs Mean-weighted occupational loading score (1 4), 2.0 (1.0) previous 12 mos Mean-weighted hrs sitting/day, previous 12 mos 2.1 (2.7) Total hrs occupational driving, previous 12 mos 170 (426) Mean-weighted lifting at work (kg frequency/ 268 (729) day), previous 12 mos Able to move positions at work (1 5 score), 1.8 (1.0) current job Enjoy work (1 5 score), current job 1.6 (0.8) Neuroticism (0 10 score), 1981 assessment 3.9 (2.4) Extroversion (0 10 score), 1981 assessment 4.4 (2.7) Interview. A detailed, structured interview was conducted with each volunteer. Current back pain and the frequency and intensity of episodes in the previous 12 months and over the lifetime of the study participants were assessed separately for the lower back. The frequency of pain interfering with daily activities and a disability scale based on the degree of interference with commonly performed daily tasks, such as lifting groceries, getting dressed, putting on socks, and being able to sleep at night (because of back pain, and not other causes) also were obtained for both recent and lifetime pain. Pain frequency, intensity, and disability in the previous 12 months were highly correlated (r ), as were the lifetime measures (r ) (Appendix; Table A). For each job, they were asked to discuss the tasks performed and to estimate their exposure to specific types of loading conditions. A consolidated 4-point scale was used to categorize study participants jobs further: 1 sedentary work and 4 heavy materials handling and positional loading. Similarly to occupational history, detailed data on smoking, driving history, and sport and other leisure time activities were gathered (Table 1). Details of these items have been reported earlier. 2 All study participants received written information about the study procedures before participation, and all study protocols were reviewed and approved by the Ethical Committee of the Department of Public Health at the University of Helsinki and the Human Subjects Committee at the University of Washington. Magnetic Resonance Imaging. The study participants spent at least 45 minutes lying supine immediately before MRI. T1, T2, and proton density-weighted images of the lumbar spines of the study participants were obtained using a 1.5-Tesla scanner (Magnetom, Siemens AG, Germany) with surface coil. Field of view was 260 mm and the slice thickness and interslice gap were 4 mm and 0.4 mm, respectively, for sagittal images and 3 mm and 0.3 mm, respectively, for axial slices. Qualitative evaluations of MRIs were performed independently by two radiologists. Each spinal level was evaluated separately, blinded to pain histories and exposures. Each MRI finding was rated using a scale from 0 to 3, with 0 being normal

3 584 Spine Volume 28 Number Table 2. Qualitative MRI Ratings, Categorized as Used in the Analyses MRI Finding Ratings %* Disc height 0 normal typically disc higher than 71.6 the upper disc 1 slight disc as high as the normal 13.7 upper disc 2 moderate disc narrower than the 11.9 normal upper disc 3 severe endplates almost in contact 2.8 Anular tear (axial 0 none present 85.0 view) 1 any tear 15.0 Disc bulging 0 none normal contour of disc slight (approximately 2.5 mm) moderate or severe ( 2.5 mm bulge) 1.0 Disc herniation 0 none slight (approximately 0 5 mm) moderate or large ( 5 mm) 1.6 Upper vertebral 0 normal 73.4 endplate 1 slight defect (1 5 mm) 21.1 irregularities 2 moderate defect ( 5 10 mm) severe defect ( 10 mm) 1.3 Vertebral osteophytes 0 none or slight (approx mm) moderate (approx mm) severe (approx. 4.5 mm) 0.8 * Percent of all L1 S1 discs. and 1 3 representing progressive degrees of abnormality. Some of the more severe categories were combined for analyses (Table 2). Anular tears and stenosis were also analyzed. The intrareader reliabilities of the different MRI findings were determined for both radiologists, and the assessments with highest reliabilities were used for analyses. The ICCs for the intrareader repeatabilities of the MRI parameters used were as follows: 0.84 for disc height narrowing, 0.69 for anular tears (contiguous with the outer disc margin), 0.64 for disc bulging, and 0.71 for disc herniations. The kappa coefficients for the intrareader reliability were 0.68 for the presence of endplate irregularities, 0.45 for osteophytes, and 0.51 for spinal stenosis. Quantitative assessment of disc signal intensity (adjusted cerebrospinal fluid) was performed as previously described (intraclass correlation coefficient 0.97). 2 Analyses involved the mean assessment value for the L1 S1 discs, as well as the rating for the worst level for each MRI outcome of interest (Appendix; Table B). Data Analysis. Because we had sampled twin pairs, data were analyzed by treating each pair as a cluster using STATA s software for survey data to obtain correct P values and confidence intervals. Logistic and ordinal logistic models were constructed, with ordinal outcome variables grouped as described in the Appendix (Table C). Prevalence odds ratios and 95% confidence intervals were calculated. Age was controlled for in all models. All measures significant in univariate analyses were candidates for the multivariate models. In the Appendix (Table A), Kendall s Tau-b correlation coefficients, partialling for age, are reported for all correlations involving a dichotomous covariate; Spearman coefficients, partialling for age, are given for the others. The significance of each association was determined through ordinal and binary logistic modeling, as above. This report is focused primarily on the MRI pain association, independent of the twinship of the study participants. But we also looked at the within-twin pair differences for these monozygotic pairs, which removed any familial aggregation, including genetic differences, in MRI pathology or in LBP reporting. Normality assumptions for the paired differences in the original, continuous versions of the frequency, intensity, and disability measures were tenable; thus, linear regression models were constructed using the paired differences in the MRI readings, so that the pain variable differences were regressed on the imaging variable intrapair differences. The percent of the variability explained was calculated using the adjusted R 2. Results Results for the mean and the worst level were generally consistent with each other. Univariate Results Measures of decreased disc height were associated with all back pain measures and had the only significant associations with the presence of sciatica in the worst lifetime episode (Appendix; Table D). Anular tears, disc bulging, osteophytes, endplate changes, and herniations were each associated with the number of lifetime back pain episodes, the intensity of the worst episode and the resulting disability, and some other pain parameters. Signal intensity and spinal stenosis had no significant associations with any of the pain parameters. Multivariable Results Only disc height narrowing and anular tears remained significant in multivariable modeling of the pain outcomes (Table 3). Disc height narrowing was significant in all models, with odds ratios for 1 point on a 0 3 scale ranging from 1.8 to 2.2 for measures of current and recent LBP. This means that a 1-point higher mean disc height narrowing score is associated with approximately twice the risk of a 1-point higher score on the corresponding pain measure. The strongest associations, fourfold to fivefold risks, were with lifetime frequency, intensity, and disability. Sciatic pain of the worst lifetime back pain episode was associated with a twofold risk. Adjusting for occupational physical demands, static work postures, driving, smoking, and job satisfaction had a small effect on the models. Controlling for physical loading during the past 12 months increased the associations of anular tears and LBP over the past 12 months and made the association with LBP today statistically significant. Anular tears were associated with pain in the previous 12 months and with the number of lifetime episodes, and the intensity of the worst episode, with the presence of tears corresponding to a 50 90% increase in risk. The presence of a tear was more powerfully associated with pain than a variable incorporating the length of the tear. Endplate irregularities, osteophytes, bulging, herniations, spinal stenosis, and the signal intensity of the disc did not enter into the model s explaining any of the pain parameters. Although disc height narrowing and anular tears were associated with many manifestations of LBP, the predictive power of these MRI findings is limited. For example, disc height narrowing is strongly associated with ever

4 Back Pain and Lumbar MRI Findings Videman et al 585 Table 3. Multivariate Models for Nine Measures of LBP, Controlling for Age and Clustering by Twin Pair Back Pain Parameter Modeled Anular Tears (Any) OR (95% CI) Adjusted Disc Height Narrowing* OR (95% CI) Adjusted LBP today NS 2.1 (1.0, 4.4) 2.4 (1.2, 4.7) 2.3 (1.0, 5.0) Ever back pain lasting 1 day NS 4.5 (1.9, 10.6) Frequency LBP past 12 mos (0 3) 1.8 (1.1, 2.9) 2.0 (1.1, 3.5) 2.2 (1.4, 3.7) 2.1 (1.2, 3.7) Intensity of pain past 12 mos (0 3) 1.8 (1.2, 3.0) 2.2 (1.3, 3.9) 1.8 (1.1, 2.9) 1.8 (1.0, 3.1) Disability past 12 mos (0 2) NS 1.9 (1.1, 3.0) 1.8 (1.1, 2.9) 1.9 (1.1, 3.3) Number of episodes (lifetime) (0 2) 1.9 (1.1, 3.2) 4.0 (2.3, 7.0) Pain intensity in worst episode (0 2) 1.5 (1.1, 2.1) 5.0 (2.7, 9.1) Disability from worst episode (0 2) 1.9 (1.1, 3.3) 4.2 (2.4, 7.2) Sciatica in lifetime worst LBP episode NS 2.1 (1.2, 3.8) LBP low back pain; OR odds ratio; CI confidence interval; NS not significant. * OR for 1 point on a 0 3 score. Mean score L1 S1. In addition, 4 pain measures for the past 12 months were adjusted for physical loading in the past 12 months. Did not enter the model. having an LBP episode lasting more than 1 day, with greater than a fourfold risk for each increment in the mean severity score. To have a mean disc height score 1, a study participant would need to have moderate or severe narrowing in at least one disc. Only one of the 43 study participants who never had an episode of LBP had a mean severity score 1, so the specificity of this cut point is good. But only 22 (12%) of the 187 study participants who had an LBP episode had a mean score 1, which is poor sensitivity. Using a different cut point, 72% of the study participants with at least one episode of LBP had some disc height narrowing recorded, but so did 63% of those who never had an episode. The associations between pain in the previous 12 months and MRI findings were small when the effect of familial aggregation was removed. When the within-pair differences in this pain variable were regressed on the within-pair differences in disc height and anular tears, they explained only 7% and 6%, respectively, of the total variance in this LBP parameter. The percentage of the variance in recent and lifetime frequency and intensity of LBP or the resulting disability explained varied from 0% to 7% of disc height and from 4% to 6% of anular tears (Table 4). Table 4. Percent of Variance in Paired Differences in Pain Accounted for by Paired Differences in Mean Disc Height and Presence of Anular Tears Pain Contrast Disc Height Anular Tears Both Combined Frequency LBP past 12 mos Intensity of pain past 12 mos Disability past 12 mos No. of episodes (lifetime) Pain intensity in worst episode Disability from worst episode Percents below 3 are not statistically significant. LBP low back pain. Discussion Anular tears were associated with most of the LBP parameters studied. However, disc height was associated with all LBP parameters, including sciatica. As expected, the associations between MRI parameters and pain were clearer for the lifetime parameters than for those for previous year and current LBP. All the other abnormalities in spinal MRIs, including disc herniations, were not associated with any of the LBP measures studied once anular tears or disc height was accounted for. Of all the potential confounders evaluated, controlling for past 12 months, physical loading increased the association mainly of anular tears and LBP today and 12-month LBP parameters. These changes in the associations could indicate that there exists an interaction between loading and LBP. The intermittent and variable nature of symptoms in the short-term, a high rate of forgotten symptoms in the long-term, and other issues affecting measurement of LBP would be expected to keep the unexplained portion of variability in pain high. The associations between spinal pathology, LBP, and physical loading are complex and further challenged by problems in measuring historical pain and loading parameters. A structured, in-depth interview may be the best option for getting data on lifetime parameters; however, gross estimates rather than precise measurements can be expected. Despite these limitations, clear associations were found between pain and the two signs of disc pathology. Among the strengths of the study are that it is based on detailed spinal MRI findings and comprehensive data on possible confounders of pain. In addition, because the study participants were monozygotic twin siblings, we were able to control for genetics and childhood influences. Our finding of an association of anular tears with LBP is consistent with what is known about the innervation of the disc and is supported by some earlier studies. 28,37,42 The lack of correlation between disc herniation and LBP parameters is unlikely to be the result of

5 586 Spine Volume 28 Number insufficient statistical power because 28% of study participants had at least one herniation. But because herniations decrease in size or can disappear over time, our chances of finding an association may have decreased when comparing worst lifetime sciatica episode with endpoint spine MRI. 8 However, our finding is concordant with some earlier studies, in which disc bulges and herniations were not associated with LBP. 5,18,44 In addition, recent studies have indicated that sciatic pain is not only caused by compression but also by biochemical effects associated with disc ruptures. 16,31,32 Disc height narrowing is commonly regarded as a nonspecific outcome of aging with little clinical importance. The clear association of disc height with all studied LBP parameters, even for LBP today, was therefore, partly, an unexpected result, although not totally new. Frymoyer et al found that there were differences in traction spurs and/or disc space narrowing at L4 L5 between three groups of men with no history, moderate, or with severe back pain. 11 Similarly, in longitudinal study, radiographic disc degeneration was associated with future back pain. 39,40 Nachemson has suggested that premature aging changes render the disc mechanically incompetent, creating abnormal motion that subject spinal structures to undue stress and lead to pain. 30 In a recent study, there was evidence of instability in 11% of motion segments with narrowed disc space using functional radiography. 33 Brown et al found angiogenesis (proliferation of blood vessels and nerve fibers) in the endplate regions and underlying vertebrae in patients with severe back pain and markedly reduced disc height, suggesting that endplates and vertebrae were the source of pain. 9 However, the prevalence of angiogenesis in the endplate regions of narrowed discs is unclear. Nerve ingrowth has been demonstrated also through anular tears and is suspected to be a disc-related causal factor for LBP. 10,14 We had hypothesized that a disc with markedly more degeneration than its neighbor discs (an outlier) could be a true injury and would be a more likely source of pain than narrowed discs throughout the lumbar spine, suggesting generalized ageing. However, the associations with pain of an outlier narrowed disc and mean disc height narrowing were generally the same (data not given). Conclusion After considering the consistent effects of disc height and anular tears, the other spine MRI findings, such as disc herniations, osteophytes, stenosis, and endplate irregularities were not associated with LBP. Adjusting for extrinsic factors thought to worsen LBP had almost no effect on the associations. After taking the combined effects of genetics and shared environment into account, disc height and tears each explained 7% and 6%, respectively, of the total variance in the LBP in the past year. The association of pain and pathologic anulus, an innervated structure, has a physiologic explanation. However, we can only speculate that narrowed discs could be associated with prior pain as a consequence of disc failure and related ingrowth of nerve fibers through endplate or anular lesions or irritation of surrounding tissues. More information on the occurrence rates of angiogenesis in discs could increase our current limited understanding about the phenomenon as a possible source for common back pain. However, our results suggest that the use of MRI assessments of anular tears and disc height alone in clinical practice would be of limited value, concordant with earlier conclusions. 7,17 Key Points Disc height and anular tears are associated with LBP history, but their sensitivity is poor, rendering them of limited clinical value. Adjusting for physical loading in past the 12 months increased the associations of anular tears and LBP in the past 12 months. The associations between pain and MRI findings were reduced after controlling the effect of familial aggregation. References 1. Annunen S, Paassilta P, Lohiniva J, et al. An allele of COL9A2 associated with intervertebral disc disease. Science 1999;285: Battié MC, Videman T, Gibbons LE, et al Volvo Award in clinical sciences: determinants of lumbar disc degeneration. A study relating lifetime exposures and magnetic resonance imaging findings in identical twins. Spine 1995;20: Beattie PF, Meyers SP, Stratford P, et al. 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6 Back Pain and Lumbar MRI Findings Videman et al Igarashi T, Kikuchi S, Shubayev V, et al Volvo Award winner in basic science studies: exogenous tumor necrosis factor-alpha mimics nucleus pulposus-induced neuropathology. Molecular, histologic, and behavioral comparisons in rats. Spine 2000;25: Jarvik JJ, Hollingworth W, Heagerty P, et al. The Longitudinal Assessment of Imaging and Disability of the Back (LAIDBack) Study: baseline data. Spine 2001;26: Jensen MC, Brant-Zawadzki MN, Obuchowski N, et al. Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl J Med 1994;331: Johansson JA, Rubenowitz S. Risk indicators in the psychosocial and physical work environment for work-related neck, shoulder and low back symptoms: a study among blue- and white-collar workers in eight companies. Scand J Rehabil Med 1994;26: Kagan AR, Levi L. Health and environment psychosocial stimuli: a review. Soc Sci Med 1974;8: Kaprio J, Koskenvuo M, Artimo M, et al. 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Reported pain during lumbar discography as a function of anular ruptures and disc degeneration: a reanalysis of 833 discograms. Spine 1994;19: Mooney V, Brown M, Modic M. Clinical perspectives. In: Frymoyer J, Gordon S, eds. New Perspectives on Low Back Pain. Chicago, IL: AAOS, Nachemson A. The future of low back pain research. In: Frymoyer JW, Gordon ST, eds. New Perspectives on Low Back Pain. Chicago, IL: AAOS, Olmarker K, Nordborg C, Larsson K, et al. Ultrastructural changes in spinal nerve roots induced by autologous nucleus pulposus. Spine 1996;21: Olmarker K, Rydevik B, Nordborg C. Autologous nucleus pulposus induces neurophysiologic and histologic changes in porcine cauda equina nerve roots. Spine 1993;18: Pitkänen M, Manninen H. Sidebending versus flexion-extension radiographs in lumbar spinal instability. Clin Radiol 1994;49: Powell MC, Wilson M, Szypryt P, et al. Prevalence of lumbar disc degeneration observed by magnetic resonance in symptomless women. 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Ann Rheum Dis 1991;50: Videman T, Gibbons LE, Battié MC, et al. The relative roles of intragenic polymorphisms of the vitamin D receptor gene in lumbar spine degeneration and bone density. Spine 2001;26: Videman T, Nurminen M, Troup JD Volvo Award in clinical sciences. Lumbar spinal pathology in cadaveric material in relation to history of back pain, occupation, and physical loading. Spine 1990;15: Weinreb JC, Wolbarsht LB, Cohen JM, et al. Prevalence of lumbosacral intervertebral disk abnormalities on MR images in pregnant and asymptomatic nonpregnant women. Radiology 1989;170: Wiesel SW, Tsourmas N, Feffer HL, et al. A study of computer-assisted tomography: I. The incidence of positive CAT scans in an asymptomatic group of patients. Spine 1984;9: Appendix Table A. Correlations Between the Pain Measures, Controlling for Age Pain Measure LBP Today Frequency 12 mos Intensity 12 mos Disability 12 mos Back Pain 1 day Lifetime, No. Intensity, Disability, Sciatica, Any LBP today * * Frequency LBP previous 12 mos * Intensity of pain previous 12 mos Disability previous 12 mos Ever had back pain lasting more than a day No. of episodes (lifetime) Pain intensity in worst episode Disability from worst episode Sciatica (present in lifetime worst LBP episode) 1.00 LBP low back pain. * All correlations greater than 0.12 are significant (P 0.05, adjusting for age and clustering by twin pair).

7 588 Spine Volume 28 Number Table B. Means and Standard Deviations of the L1 S1 Average and the Score in L1 S1 for the MRI Parameters MRI Parameter Average L1 S1 Level T1 signal intensity 1.05 (0.11) 0.90 (0.15) (cerebral spinal fluid adjusted)* Disc height (0 3 score) 0.5 (0.5) 1.3 (1.0) Any anular tears contiguous with 0.15 (0.17) 0.53 (0.58) the margin Anular tears contiguous with the 0.7 (0.9) 2.6 (2.9) margin (mm) Stenosis (mm) 0.3 (0.8) 1.2 (2.9) Herniations (0 2 score) 0.1 (0.2) 0.4 (0.6) Disc bulging (0 2 score) 0.2 (0.2) 0.5 (0.6) Endplate irregularities (0 3 score) 0.3 (0.3) 1.0 (0.9) Osteophytes (0 2 score) 0.3 (0.4) 1.1 (1.1) * Scores reversed in analyses, so a higher score is worse. 15% of discs had a tear, and 53% of subjects had at least one tear. Table C. Occurrence of Pain Pain Measure % Any LBP today 20.4 Frequency of LPB past 12 mos None to 3 times/yr 30.4 Several times/yr to monthly 17.0 Weekly or more frequent 18.7 Intensity of worst pain in past 12 mos (0 100) None Disability from worst pain in past 12 mos (0 2 score) None Ever had LBP lasting more than a day 81.3 No. of episodes (lifetime) None or Intensity of pain in worst episode None Disability from worst episode (0 3 scale) None to to Sciatica (present in lifetime worst episode) 32.9 LBP low back pain. Table D. Odds Ratios and 95% Confidence Intervals for Significant Univariate (Age-Adjusted) Associations Between Pain and MRI Readings Pain Assessment MRI Reading OR (95% CI) Any LBP today Disc narrowing (0 3), mean 2.4 (1.2, 4.7) Bulging (0 2), worst 2.0 (1.1, 3.5) Ever had back pain Disc narrowing (0 3), mean 4.5 (1.9, 10.6) lasting more than Bulging (0 2), worst 1.8 (1.1, 3.1) a day Osteophytes (0 3), mean 3.3 (1.2, 9.3) Frequency LBP past Disc narrowing (0 3), mean 2.4 (1.4, 4.0) 12 mos (0 3 scale) Anular tears (any) 1.9 (1.2, 3.1) Endplate changes (0 3), worst 1.5 (1.1, 2.1) Intensity of pain past Disc narrowing (0 3), mean 1.9 (1.2, 3.2) 12 mos (0 3 scale) Anular tears (any) 1.9 (1.2, 3.1) Disability past 12 mos Disc narrowing (0 3), mean 1.7 (1.1, 2.9) (0 2 scale) No. of episodes Disc narrowing (0 3), mean 4.3 (2.5, 7.5) (lifetime) Anular tears (any) 2.3 (1.3, 3.7) (0 2 scale) Bulging (0 2), worst 2.4 (1.6, 3.7) Osteophytes (0 3), mean 2.3 (1.2, 4.2) Endplate changes (0 3), worst 1.3 (1.0, 1.7) Herniations (0 2), worst 1.7 (1.3, 2.4) Pain intensity in Disc narrowing (0 3), mean 5.6 (3.0, 10.2) worst episode Anular tears (any) 2.2 (1.3, 3.7) (0 2 scale) Bulging (0 2), worst 2.5 (1.6, 4.1) Osteophytes (0 3), mean 2.4 (1.3, 4.7) Endplate changes (0 3), worst 1.4 (1.1, 1.9) Herniations (0 2), worst 1.7 (1.1, 2.5) Disability from worst Disc narrowing (0 3), mean 4.4 (2.6, 7.6) episode (0 2 scale) Anular tears (any) 2.2 (1.3, 3.6) Bulging (0 2), worst 2.2 (1.4, 3.5) Osteophytes (0 3), mean 2.4 (1.3, 4.5) Endplate changes (0 3), worst 1.6 (1.2, 2.0) Herniations (0 2), worst 1.7 (1.1, 2.5) Sciatica (present in lifetime worst episode) Disc narrowing (0 3), mean 2.1 (1.2, 3.8) LBP low back pain; MRI magnetic resonance imaging; OR odds ratio; CI confidence interval.