Per Kjaer

Magnetic resonance imaging and low back pain in adults: a diagnostic imaging study of 40-year-old men and women.

Study Design. Cross-sectional cohort study of a general population. Objective. To investigate “abnormal” lumbar spine magnetic resonance imaging (MRI) findings, and their prevalence and associations with low back pain (LBP). Summary of Background Data. The clinical relevance of various “abnormal” findings in the lumbar spine is unclear. Distinguishing between inevitable age-related findings and degenerative findings with deleterious consequences is a challenge. Methods. Lumbar spine MRI was obtained in 412, 40-year-old individuals. Predefined “abnormal” MRI findings were interpreted without any knowledge of patient symptoms. Associations between MRI abnormalities and LBP were calculated using odds ratios. The “overall picture” of each MRI finding was established on the basis of the frequencies, diagnostic values, and the strength and consistency of associations. Results. Most “abnormal” MRI findings were found at the lowest lumbar levels. Irregular nucleus shape and reduced disc height were common (>50% of individuals). Relatively common (25% to 50%) were hypointense disc signal, anular tears, high intensity zones, disc protrusions, endplate changes, zygapophyseal joint degeneration, asymmetry, and foraminal stenosis. Nerve root compromise, Modic changes, central spinal stenosis, and anterolisthesis/retrolisthesis were rare (<25%). Most strongly associated with LBP were Modic changes and anterolisthesis (odds ratios >4). Significantly positive associations with all LBP variables were seen for hypointense disc signals, reduced disc height, and Modic changes. All disc “abnormalities” except protrusion were moderately associated with LBP during the past year. Conclusion. Most degenerative disc “abnormalities” were moderately associated with LBP. The strongest associations were noted for Modic changes and anterolisthesis. Further studies are needed to define clinical relevance.

Modic changes and their associations with clinical findings

It is believed that disc degeneration (DD) is, in general, only mildly associated with low back pain (LBP). MRI-identified Modic changes (MC), probably a late stage of DD, are relatively strongly associated with LBP but it is not known if people with MC also have a specific clinical profile. The purpose of this study was to investigate if the clinical findings differ in people with Modic changes (MC) as compared to those with only degenerative disc findings or none at all. In a population-based sample of 412 40-year-old Danes, information was collected independently with MRI, questionnaires and clinical examination. Three subgroups of people were created: those with both DD and MC, those with only DD, and those with neither DD nor MC. The clinical pattern was investigated for each subgroup in order to test the assumption that the clinical picture differs in the three groups. It was expected that people with both DD and MC would have a more pronounced clinical profile than those with only DD who, in turn, would differ from those with neither of these two MRI findings. Our findings were generally in concordance with our expectations. MC constitutes the crucial element in the degenerative process around the disc in relation to LBP, history, and clinical findings. People with DD and no MC only vaguely differ from those without. People with LBP and MC may deserve to be diagnosed as having specific LBP.

Are MRI-defined fat infiltrations in the multifidus muscles associated with low back pain?

BackgroundBecause training of the lumbar muscles is a commonly recommended intervention in low back pain (LBP), it is important to clarify whether lumbar muscle atrophy is related to LBP. Fat infiltration seems to be a late stage of muscular degeneration, and can be measured in a non-invasive manner using magnetic resonance imaging. The purpose of this study was to investigate if fat infiltration in the lumbar multifidus muscles (LMM) is associated with LBP in adults and adolescents.MethodsIn total, 412 adults (40-year-olds) and 442 adolescents (13-year-olds) from the general Danish population participated in this cross-sectional cohort study. People with LBP were identified through questionnaires. Using MRI, fat infiltration of the LMM was visually graded as none, slight or severe. Odds ratios were calculated for both age groups, taking into account sex, body composition and leisure time physical activity for both groups, and physical workload (in adults only) or daily bicycling (in adolescents only).ResultsFat infiltration was noted in 81% of the adults but only 14% of the adolescents. In the adults, severe fat infiltration was strongly associated with ever having had LBP (OR 9.2; 95% CI 2.0–43.2), and with having LBP in the past year (OR 4.1; 1.5–11.2), but there was no such association in adolescents. None of the investigated moderating factors had an obvious effect on the OR in the adults.ConclusionFat infiltration in the LMM is strongly associated with LBP in adults only. However, it will be necessary to quantify these measurements objectively and to investigate the direction of this link longitudinally in order to determine if the abnormal muscle is the cause of LBP or vice versa.

An epidemiologic study of MRI and low back pain in 13-year-old children.

Study Design. Cross-sectional cohort study of a general population. Objective. To describe associations between “abnormal” lumbar magnetic resonance imaging (MRI) findings and low back pain (LBP) in 13-year old children. Summary and Background Data. Very little is known about the distribution of lumbar MRI findings and how they are associated with LBP in youngsters. Methods. Disc abnormalities, as well as nerve root compromise, endplate changes, and anterolisthesis were identified from MRI studies of 439 children. LBP was identified from structured interviews. Associations are presented as odds ratios (OR). Results. Signs of disc degeneration were noted in approximately 1/3 of the subjects. Reduced signal intensity and irregular nucleus shape in the upper 3 lumbar discs were significantly associated with LBP within the last month (OR, 2.5–3.6), whereas reduced signal intensity and disc protrusion at L5–NS1 were associated with seeking care (OR, 2.8 and 7.7, respectively). Endplate changes in relation to the L3 discs were associated with LBP month and seeking care (OR, between 9.7 and 22.2). Anterolisthesis at L5 was associated with seeking care (OR, 4.3). There were obvious differences between genders: degenerative disc changes in the upper lumbar spine were more strongly associated with LBP in boys, while disc abnormalities in the lower lumbar spine were more strongly associated with seeking care in girls. Conclusions. In children, degenerative disc findings are relatively common, and some are associated with LBP. There appears to be a gender difference. Disc protrusions, endplate changes, and anterolisthesis in the lumbar spine were strongly associated with seeking care for LBP.

Intra- and Interobserver Reproducibility of Vertebral Endplate Signal (Modic) Changes in the Lumbar Spine: The Nordic Modic Consensus Group Classification

Background: The lumbar vertebral endplate is considered a potential cause of specific low back pain. However, in relation to future research, there is need for a reliable and detailed magnetic resonance imaging (MRI) protocol to be used in the evaluation of vertebral endplate signal changes. Purpose: To assess the intra- and interobserver reliability of the “Nordic Modic classification” protocol. Material and Methods: MRI scans of 50 individuals representative of the general Danish population aged 40 were evaluated by two observers. Criteria for grading the changes were developed by the Nordic Modic Consensus Group. After consensus was established, all 50 MRI examinations were evaluated independently by each observer. Intraobserver reliability was assessed by re-evaluation of the 50 examinations by one of the observers. Kappa statistics were used to calculate agreement. Results: Intra- and interobserver agreement of the evaluation of variables describing vertebral signal changes, i.e. Modic type, location, volume, maximum height, and endplate area, were all found to have substantial to almost perfect agreement. The evaluation of osteophytes was found to be reliable, whereas the evaluation of localized endplate defects and irregular endplates had only moderate agreement. The evaluation of development over time was found to have substantial intraobserver agreement but only moderate interobserver agreement. As expected, intraobserver agreement was generally better than interobserver agreement. Conclusion: In this study, we found convincing reproducibility of a detailed evaluation protocol of vertebral endplate signal changes, the “Nordic Modic Classification.” The authors recommend that the evaluation protocol should be used in future studies investigating vertebral endplate signal changes.

Characteristics and natural course of vertebral endplate signal (Modic) changes in the Danish general population

BackgroundVertebral endplate signal changes (VESC) are more common among patients with low back pain (LBP) and/or sciatica than in people who are not seeking care for back pain. The distribution and characteristics of VESC have been described in people from clinical and non-clinical populations. However, while the clinical course of VESC has been studied in patients, the natural course in the general population has not been reported. The objectives of this prospective observational study were to describe: 1) the distribution and characteristics of VESC in the lumbar spine, 2) its association with disc degeneration, and 3) its natural course from 40 to 44 years of age.MethodsThree-hundred-and-forty-four individuals (161 men and 183 women) sampled from the Danish general population had MRI at the age of 40 and again at the age of 44. The following MRI findings were evaluated using standardised evaluation protocols: type, location, and size of VESC, disc signal, and disc height. Characteristics and distribution of VESC were analysed by frequency tables. The association between VESC and disc degeneration was analysed by logistic regression analysis. The change in type and size of VESC was analysed by cross-tabulations of variables obtained at age 40 and 44 and tested using McNemars test of symmetry.ResultsTwo-thirds (67%) of VESC found in this study were located in the lower part of the spine (L4-S1). VESC located at disc levels L1-L3 were generally small and located only in the anterior part of the vertebra, whereas those located at disc levels L4-S1 were more likely to extend further into the vertebra and along the endplate. Moreover, the more the VESC extended into the vertebra, the more likely it was that the adjacent disc was degenerated. The prevalence of endplate levels with VESC increased significantly from 6% to 9% from age 40 to 44. Again, VESC that was only observed in the endplate was more likely to come and go over the four-year period compared with those which extended further into the vertebra, where it generally persisted.ConclusionThe prevalence of VESC increased significantly over the four-year period. Furthermore, the results from this study indicate that the distribution of VESC, its association with disc degeneration and its natural course, is dependent on the size of the signal changes.

Low-Field Magnetic Resonance Imaging of the Lumbar Spine: Reliability of Qualitative Evaluation of Disc and Muscle Parameters

Purpose: To determine the intra- and interobserver reliability in grading disc and muscle parameters using low-field magnetic resonance imaging (MRI). Material and Methods: MRI scans of 100 subjects representative of the general population were evaluated blindly by two radiologists. Criteria for grading lumbar discs were based on the spinal nomenclature of the Combined Task Force and the literature. Consensus in rating was achieved by evaluating 50 MRI examinations in tandem. The remaining 50 examinations were evaluated independently by the observers to determine interobserver agreement and re-evaluated by one of the observers to determine intra-observer agreement. Results: Intra- and interobserver agreement was substantial when grading changes in the lumbar discs. Interobserver agreement was fair to moderate in grading the lumbar muscles, whereas intra-observer agreement was almost perfect. Conclusion: Convincing reliability was found in the evaluation of disc- and muscle-related MRI variables.

Genetic Association Studies in Lumbar Disc Degeneration: A Systematic Review

Objective Low back pain is associated with lumbar disc degeneration, which is mainly due to genetic predisposition. The objective of this study was to perform a systematic review to evaluate genetic association studies in lumbar disc degeneration as defined on magnetic resonance imaging (MRI) in humans. Methods A systematic literature search was conducted in MEDLINE, MEDLINE In-Process, SCOPUS, ISI Web of Science, The Genetic Association Database and The Human Genome Epidemiology Network for information published between 1990–2011 addressing genes and lumbar disc degeneration. Two investigators independently identified studies to determine inclusion, after which they performed data extraction and analysis. The level of cumulative genetic association evidence was analyzed according to The HuGENet Working Group guidelines. Results Fifty-two studies were included for review. Forty-eight studies reported at least one positive association between a genetic marker and lumbar disc degeneration. The phenotype definition of lumbar disc degeneration was highly variable between the studies and replications were inconsistent. Most of the associations presented with a weak level of evidence. The level of evidence was moderate for ASPN (D-repeat), COL11A1 (rs1676486), GDF5 (rs143383), SKT (rs16924573), THBS2 (rs9406328) and MMP9 (rs17576). Conclusions Based on this first extensive systematic review on the topic, the credibility of reported genetic associations is mostly weak. Clear definition of lumbar disc degeneration phenotypes and large population-based cohorts are needed. An international consortium is needed to standardize genetic association studies in relation to disc degeneration.

Prevalence and tracking of back pain from childhood to adolescence

BackgroundIt is generally acknowledged that back pain (BP) is a common condition already in childhood. However, the development until early adulthood is not well understood and, in particular, not the individual tracking pattern. The objectives of this paper are to show the prevalence estimates of BP, low back pain (LBP), mid back pain (MBP), neck pain (NP), and care-seeking because of BP at three different ages (9, 13 and15 years) and how the BP reporting tracks over these age groups over three consecutive surveys.MethodsA longitudinal cohort study was carried out from the years of 1997 till 2005, collecting interview data from children who were sampled to be representative of Danish schoolchildren. BP was defined overall and specifically in the three spinal regions as having reported pain within the past month. The prevalence estimates and the various patterns of BP reporting over time are presented as percentages.ResultsOf the 771 children sampled, 62%, 57%, and 58% participated in the three back surveys and 34% participated in all three. The prevalence estimates for children at the ages of 9, 13, and 15, respectively, were for BP 33%, 28%, and 48%; for LBP 4%, 22%, and 36%; for MBP 20%, 13%, and 35%; and for NP 10%, 7%, and 15%. Seeking care for BP increased from 6% and 8% at the two youngest ages to 34% at the oldest. Only 7% of the children who participated in all three surveys reported BP each time and 30% of these always reported no pain. The patterns of development differed for the three spinal regions and between genders. Status at the previous survey predicted status at the next survey, so that those who had pain before were more likely to report pain again and vice versa. This was most pronounced for care-seeking.ConclusionIt was confirmed that BP starts early in life, but the patterns of onset and development over time vary for different parts of the spine and between genders. Because of these differences, it is recommended to report on BP in youngsters separately for the three spinal regions, and to differentiate in the analyses between the genders and age groups. Although only a small minority reported BP at two or all three surveys, tracking of BP (particularly NP) and care seeking was noted from one survey to the other. On the positive side, individuals without BP at a previous survey were likely to remain pain free at the subsequent survey.

The Relationship of Lumbar Multifidus Muscle Morphology to Previous, Current, and Future Low Back Pain: A 9-Year Population-Based Prospective Cohort Study

Study Design. Population based prospective cohort study. Objective. We explored the cross-sectional relationships between lumbar multifidus (LM) intramuscular adipose tissue (IMAT) infiltration and low back pain (LBP) at 3 successive time points and investigated the role of IMAT in predicting the occurrence of LBP after 5 and 9 years. Summary of Background Data. Although LBP is a major source of disease burden, the biological determinants of LBP are poorly understood. Methods. Participants were 40-year-old adults randomly sampled from a Danish population and followed up at 45 and 49 years of age. At each time point, participants underwent magnetic resonance imaging and reported ever having had LBP, LBP in the previous year, nontrivial LBP in the previous year, or a history of pain radiating into the legs. Pixel intensity and frequencies from T1-weighted magnetic resonance images identified the greatest proportion of LM IMAT at the L4 and L5 spinal levels. IMAT infiltration was categorized as normal/mild, moderate, or severe based on tertile divisions. Associations were explored with crude and adjusted odds ratios (aORs) from logistic regression models. Model covariates included sex, body mass index, and occupational and leisure time physical activity. Results. A total of 401 participants were enrolled, with 331 (83%) and 286 (71%) participants followed up at 5 and 9 years, respectively. The cross-sectional analyses demonstrated that at the age of 40 years, participants with severe IMAT infiltration demonstrated increased odds of ever experiencing LBP (aOR [95% confidence interval, 95% CI] = 3.16 [1.45–6.89]), nontrivial LBP (aOR [95% CI] = 2.82 [1.36–5.81]), LBP in the past year (aOR [95% CI] = 1.95 [1.07–3.53]), and leg pain (aOR [95% CI] = 2.08 [1.19–3.62]). There were no consistent cross-sectional associations between LBP/leg pain and LM IMAT at 45 or 49 years of age and LM IMAT did not predict future LBP or leg pain. Conclusion. The relationship between LM IMAT and LBP/leg pain is inconsistent and may be modified by age. Level of Evidence: N/A