Methodology and cohort profile for the Hangzhou Lumbar Spine Study: a study focusing on back health in a Chinese population

Back pain is a worldwide health problem, adding a tremendous burden to modern societies. However, little information on back health is available in China, even though a quarter of the world's population is Chinese. To enhance knowledge in this area, we designed and initiated the Hangzhou Lumbar Spine Study, which is a cross-sectional study of a general sample of mainland Chinese with focusing on disc degeneration, Modic changes, endplate lesions, and back pain. The study consists of a structured questionnaire to measure back pain history and lifetime exposure to suspected risk factors, magnetic resonance imaging of the lumbar spine, bone mineral density study of the spine and hip, and DNA sample analysis. Here we briefly introduce the study methodology, report the test-retest reliability of the questionnaire, and describe the cohort profile to date. Since May 2014, 301 randomly selected subjects (male/female, 122/179; mean age, 51.0 years; range, 20-87 years) have been recruited. Tests-retests of the questionnaire, completed by 40 participants, revealed good reliability. To our knowledge, the Hangzhou Lumbar Spine Study is the first population-based epidemiological study conducted to characterize lumbar spinal phenotypes and back pain, their interaction, and their associations with lifetime environmental exposure, in mainland Chinese. Epidemiological information obtained from a reliable questionnaire, magnetic resonance (MR) imaging data, dual energy X-ray absorptiometry (DXA) measurements, and DNA analysis may serve as a valuable reference for future studies on back health, particularly for mainland Chinese.

MRI evaluation of the effects of extension exercises on the disc fluid content and location of the centroid of the fluid distribution

BACKGROUND

McKenzie prone press-up exercises have been hypothesised to reduce intradiscal pressure, allowing fluid to be reabsorbed into the disc, which could improve the internal stability and local chemical milieu of the disc, potentially reducing symptoms.

OBJECTIVE

To investigate the immediate effects of prone press-up exercises on lumbar disc fluid content and movement.

DESIGN

Quantification of MRI changes before and after a single exercise session.

METHODS

The mid-sagittal T₂-weighted MR images of 22 volunteers with low back pain were obtained before and immediately after performing press-up exercises. The whole disc and nucleus regions of the L4-5 and L5-S1 discs were then segmented, and their mean signal intensity (MSI) and signal intensity weighted centroid (SIWC) were computed to estimate disc fluid content and displacement.

RESULTS

There were no significant differences between the MSI and the vertical position of the SIWC of the whole disc before and after extension at either disc level (effect size [ES]: -0.23 to 0.09). There was a significant anterior displacement (0.1 ± 5.4 mm) of the location of the SIWC of the disc after extension exercise at L4-5 (ES: 0.22), but not at L5-S1 (ES: 0.00) or at either level for the nucleus region (ES: -0.06; 0.16).

CONCLUSION

Little evidence was found supporting the hypothesis that press-up exercises affect disc fluid content and distribution. Novel parameters reflecting fluid distribution detected similar or larger effects of the extension than MSI. If such exercises are effective in reducing symptoms, it is likely through other mechanisms than by changing fluid content or distribution.

MRI-based hip cartilage measures in osteoarthritic and non-osteoarthritic individuals: a systematic review

Osteoarthritis is a common hip joint disease, involving loss of articular cartilage. The prevalence and prognosis of hip osteoarthritis have been difficult to determine, with various clinical and radiological methods used to derive epidemiological estimates exhibiting significant heterogeneity. MRI-based methods directly visualise hip joint cartilage, and offer potential to more reliably define presence and severity of osteoarthritis, but have been underused. We performed a systematic review of MRI-based estimates of hip articular cartilage in the general population and in patients with established osteoarthritis, using MEDLINE, EMBASE and SCOPUS current to June 2016, with search terms such as ‘hip’, ‘femoral head’, ‘cartilage’, ‘volume’, ‘thickness’, ‘MRI’, etc. Ultimately, 11 studies were found appropriate for inclusion, but they were heterogeneous in osteoarthritis assessment methodology and composition. Overall, the studies consistently demonstrate the reliability and potential clinical utility of MRI-based estimates. However, no longitudinal data or reference values for hip cartilage thickness or volume have been published, limiting the ability of MRI to define or risk-stratify hip osteoarthritis. MRI-based techniques are available to quantify articular cartilage signal, volume, thickness and defects, which could establish the sequence and rate of articular cartilage changes at the hip that yield symptomatic osteoarthritis. However, prevalence and rates of progression of hip osteoarthritis have not been established in any MRI studies in the general population. Future investigations could fill this important knowledge gap using robust MRI methods in population-based cross-sectional and longitudinal studies.

Cranio-caudal asymmetries in trabecular architecture reflect vertebral fracture patterns

Clinically, vertebral fractures often occur in the upper lumbar spine and involve the superior endplate of a vertebra (which is immediately caudal to a disc). Knowledge that the cranial endplate of a disc is thicker and has greater bone mineral density (BMD) than the corresponding caudal endplate helps to explain this phenomenon. In this study, we investigated structural differences in vertebral trabeculae on either side of a lumbar disc to provide further insight into vertebral fracture risk. As the focus is trabecular difference within a spinal motion segment, we define cranial and caudal vertebral trabeculae relative to the disc. Ninety-two spinal motion segments from 46 cadaveric lumbar spines (males, mean age 50years, range 21-63years) were studied. Disc narrowing on radiography and spread of barium sulfate (BaSO₄) on discography were measured to indicate disc degeneration. Micro-computed tomography (μCT) images were obtained at a resolution of 82μm for each vertebra and processed to include only vertebral trabeculae. Using image processing, the vertebral trabeculae were divided into superior and inferior halves, and then into central and peripheral regions which were approximately opposite to the disc pulposus and annulus, and further into anterior and posterior sub-regions. Microarchitecture measurements for each vertebral region were obtained to determine the differences between the cranial and caudal trabeculae (relative to disc) and their associations with age and disc degeneration within each spinal motion segment. Data from the upper (L1/2-L3/4) and lower (L4/5) lumbar segments were analyzed separately. In the upper lumbar region, the trabeculae cranial to a disc on average had 5.3% greater BMD and trabecular bone volume, 3.6% greater trabecular number, 9.7% greater connectivity density, and 3.7% less trabecular separation than the corresponding caudal trabeculae (P<0.05 for all). Similar trends were observed in peripheral, anterior and posterior regions, but not in central region. No structural difference was observed in the trabeculae of L4/5 segment. Structural asymmetries of vertebral trabeculae were not associated with age, disc degeneration, or disc narrowing. Vertebral trabecular parameters cranial to the disc were greater than caudally in the upper but not in the lower lumbar region. Findings further explain why vertebral fractures are more common in the upper lumbar region and more frequently involve the endplate caudal to a disc.

ISSLS Prize Winner: Consensus on the Clinical Diagnosis of Lumbar Spinal Stenosis: Results of an International Delphi Study

STUDY DESIGN

Delphi.

OBJECTIVE

The aim of this study was to obtain an expert consensus on which history factors are most important in the clinical diagnosis of lumbar spinal stenosis (LSS).

SUMMARY OF BACKGROUND DATA

LSS is a poorly defined clinical syndrome. Criteria for defining LSS are needed and should be informed by the experience of expert clinicians.

METHODS

Phase 1 (Delphi Items): 20 members of the International Taskforce on the Diagnosis and Management of LSS confirmed a list of 14 history items. An online survey was developed that permits specialists to express the logical order in which they consider the items, and the level of certainty ascertained from the questions. Phase 2 (Delphi Study) Round 1: Survey distributed to members of the International Society for the Study of the Lumbar Spine. Round 2: Meeting of 9 members of Taskforce where consensus was reached on a final list of 10 items. Round 3: Final survey was distributed internationally. Phase 3: Final Taskforce consensus meeting.

RESULTS

A total of 279 clinicians from 29 different countries, with a mean of 19 (±SD: 12) years in practice participated. The six top items were "leg or buttock pain while walking," "flex forward to relieve symptoms," "feel relief when using a shopping cart or bicycle," "motor or sensory disturbance while walking," "normal and symmetric foot pulses," "lower extremity weakness," and "low back pain." Significant change in certainty ceased after six questions at 80% (P < .05).

CONCLUSION

This is the first study to reach an international consensus on the clinical diagnosis of LSS, and suggests that within six questions clinicians are 80% certain of diagnosis. We propose a consensus-based set of "seven history items" that can act as a pragmatic criterion for defining LSS in both clinical and research settings, which in the long term may lead to more cost-effective treatment, improved health care utilization, and enhanced patient outcomes.

LEVEL OF EVIDENCE

2.

The relation of social support and depression in patients with chronic low back pain

PURPOSE

Depression is a common condition in adults with low back pain (LBP), and is associated with poorer patient outcomes. Social support is a modifiable factor that may influence depressive symptoms in people with LBP and, if so, could be a consideration in LBP management when depression is an issue. The aim of this study was to examine social support as a prognostic factor for depressive symptoms and recovery from depression in patients with LBP.

METHOD

Patients with LBP (n = 483), recruited from four imaging centers in Canada, completed an initial survey following imaging and a follow-up survey one year later, including the Medical Outcomes Study (MOS) Social Support Survey and the Center for Epidemiologic Studies Depression Scale. Multivariable regression analyses were used to examine the relationship between social support and depression.

RESULTS

More social support (overall functional social support) at baseline was associated with recovery from depression (OR = 0.24; 95% CI 0.10, 0.55) and less depressive symptoms (β = 1.68; 95% CI = 0.36, 3.00) at one-year follow-up. In addition, associations were found between specific aspects (subscales) of social support and the two depression outcomes.

CONCLUSIONS

Functional social support as a prognostic factor for depression and possible target of LBP management warrants further investigation. Implications for Rehabilitation Depression is a common condition in adults with low back pain (LBP), and is associated with poorer patient outcomes. This study provides evidence for social support as a prognostic factor for depressive symptoms and recovery from depression in patients with LBP problems. Management of pain conditions may be enhanced by a better understanding of modifiable risk factors for depression, such as social support.

A comparison of two methods to evaluate a narrow spinal canal: routine magnetic resonance imaging versus three-dimensional reconstruction

BACKGROUND CONTEXT

In routine clinical practice, the presence of lumbar spinal stenosis (LSS) is assessed on axial magnetic resonance images (MRI) typically acquired using a preselected spine sagittal angle. Given the natural lordosis of the lumbar spine, not all axial slices will be parallel to the disc and perpendicular to the spinal canal and, thus, are not optimal for the assessment of dural sac cross-sectional area (DCSA).

PURPOSE

The objective of this study was to compare DCSA measurements from routinely acquired clinical images with three-dimensional (3D)-reconstructed images.

STUDY DESIGN

This is a cross-sectional study.

PATIENT SAMPLE

The sample consists of 390 patients referred for lumbar imaging with some aspect of anatomical LSS found, with no prior back surgery, 40 years of age or older, and with available volumetric MR images to allow 3D reconstruction of the spine.

OUTCOME MEASURES

The outcome of interest in this study was dural sac cross sectional area.

METHODS

Spine images were 3D reconstructed at the level of the disc, perpendicular to the spinal canal. Dural sac cross-sectional area was measured for both 3D-reconstructed and routinely acquired clinical images using the slice orientation captured.

RESULTS

Dural sac cross-sectional area for the lower lumbar levels (L4-L5 and L5-S1) was significantly different between routinely acquired clinical images and 3D-reconstructed images, with a standard error of measurement of 12.98 and 19.73 mm(2), respectively.

CONCLUSIONS

When canal size is of interest, particularly when LSS affecting the lower lumbar levels is of concern, 3D reconstruction of clinical images should be considered.

The distribution of bone mass in the lumbar vertebrae: are we measuring the right target?

BACKGROUND CONTEXT

The ideal target of bone mineral density (BMD) measurements of the spine is the trabecula-rich vertebral body. Yet, spine BMD measurements routinely obtained with dual-energy X-ray absorptiometry also include the posterior elements of the vertebra, which are mainly cortical bone and insensitive to bone loss.

PURPOSE

We compared the bone mass of the vertebral body and posterior elements to determine the contributions of vertebral components to vertebral BMD measurements.

STUDY DESIGN

A micro-computed tomography study of lumbar vertebral bone.

METHODS

From a spine archive, 144 cadaveric lumbar vertebrae (L1-L5) from 48 male human spines (mean age, 50 years) were scanned in air using micro-computed tomography to measure bone volume, bone mineral content (BMC) and BMD of the vertebral body, posterior elements, and entire vertebra. The contributions of the vertebral components to the total vertebral BMC and volume were compared, and the correlations between the BMC and BMD of the vertebrae and their components were examined.

RESULTS

Overall, the vertebral body contributed about one-third of the total vertebral BMC and two-thirds of the total vertebral volume, and the posterior elements contributed the remainder. The vertebral body BMC and BMD were poorly correlated to those of the posterior elements (r=0.39 for BMC and r=0.34 for BMD, p<.0001) and moderately correlated to the whole vertebra (r=0.77 and 0.75, respectively, p<.0001). The BMC and BMD of the posterior elements and whole vertebra were more strongly correlated (r=0.89 and 0.84, respectively, p<.0001).

CONCLUSIONS

The posterior elements are the primary contributor to vertebral BMC and BMD measurements. Dual-energy X-ray absorptiometry spine BMD measurements are likely to be more representative of the posterior elements than the targeted vertebral body. The findings elucidate the extent of the limitation of dual-energy X-ray absorptiometry spine BMD measurements.

Lumbar spinal stenosis is a highly genetic condition partly mediated by disc degeneration

Objective. Lumbar spinal stenosis is one of the most commonly diagnosed spinal disorders in older adults. Although the pathophysiology of the clinical syndrome is not well understood, a narrow central canal or intervertebral foramen is an essential or defining feature. The aim of the present study was to estimate the magnitude of genetic versus environmental influences on central lumbar spinal stenosis and to investigate disc degeneration and stature or bone development as possible genetic pathways.Methods. A classic twin study with multivariate analyses considering lumbar level and other covariates was conducted. The study sample comprised 598 male twins (147 monozygotic and 152 dizygotic pairs), 35-70 years of age, from the population-based Finnish Twin Cohort. The primary phenotypes were central lumbar stenosis as assessed qualitatively on magnetic resonance imaging (MRI) and quantitatively measured dural sac cross-sectional area. Additional phenotypes (to examine possible genetic pathways) included disc bulging and standing height, as an indicator of overall skeletal size or development.Results. The heritability estimate (h²) for qualitatively assessed central lumbar spinal stenosis on MRI was 66.9% (95% confidence interval [95% CI] 56.8,74.5). The broad-sense heritability estimate for dural sac cross-sectional area was 81.2% (95% CI 74.5, 86.1),with a similar magnitude of genetic influences across lumbar levels (h²=72.4–75.6). The additive genetic correlation of quantitatively assessed stenosis and disc bulging was extremely high. There was no indication of shared genetic influences between stenosis and stature.Conclusion. Central lumbar spinal stenosis and associated dural sac dimensions are highly genetic, and disc degeneration (bulging) appears to be one pathway through which genes influence spinal stenosis.

Pathoanatomical characteristics of clinical lumbar spinal stenosis

BACKGROUND

There is no clear picture of pathoanatomy in clinically diagnosed LSS. Findings in the literature regarding imaging in LSS are heterogeneous.

OBJECTIVE

Characterize the pathoanatomy of LSS, as reported in the radiology reports, for a large community-based sample of patients with the clinical diagnosis of LSS.

METHODS

Retrospective review of clinical radiology reports. The sample comprised patients 40 years of age or older, with clinically diagnosed LSS. Radiology reports for lumbar MRI were obtained and data were extracted pertaining to the type and location of LSS.

RESULTS

173 subjects with a mean age of 66.2 ± 11.7 years were included (61% women). 68.2% had mixed stenosis, 19.1% had central stenosis only, and 12.7% had lateral stenosis only. By level, the most prevalent findings were at L4/5 (93%), L3/4 (66%) and L5/S1 (49%). This pattern was different in those with lateral stenosis only, where the proportion of findings at L5/S1 was higher than at L3/4. 156 subjects (90.2%) had findings of at least moderate severity. Considering moderate-severe findings only, 31% had mixed stenosis and 40.0% had multi-level findings (90.5% at adjacent segments). When mild findings were included for subjects with at least one moderate-severe finding the rate of mixed stenosis increased to 59%, and multi-level stenosis to 68.6%. The most common multi-level combinations were L3/4 and L4/5 for two-level stenosis and L2/3 through L4/5 for three-level.

CONCLUSION

Results of this study confirm a number of pathoanatomical patterns in people diagnosed with LSS, including a high proportion of stenosis at L4/5, followed by L3/4 and L5/S1. Results also suggest a high prevalence of multi-level stenosis at adjacent segments. The prevalence of mixed stenosis varied from 31% to 68.2%; inclusion of mild findings resulted in a higher rate of both mixed and multi-level stenosis, compared to analysis of moderate-severe findings only. These results may guide future studies on LSS pathophysiology, by focusing attention toward the most prevalent radiological findings.

A cluster randomized clinical trial comparing functional capacity evaluation and functional interviewing as components of occupational rehabilitation programs

PURPOSE

Functional capacity evaluations (FCE) are used to identify work abilities and are commonly integrated into rehabilitation programs. We studied whether integrating FCE into rehabilitation leads to better outcomes for injured workers.

METHODS

A cluster randomised controlled trial was conducted at a workers' compensation rehabilitation facility (registration ISRCTN61284905). Clinicians were randomised into 2 groups: 1 group used FCE while another conducted semi-structured functional interviews. Outcomes included recommendations following assessment, rehabilitation program outcomes including functional work levels and pain intensity, as well as compensation outcomes at 1, 3, and 6 months after assessment. Analysis included Mann-Whitney U, Chi square and t tests.

RESULTS

Subjects included 225 claimants of whom 105 were tested with FCE. Subjects were predominantly employed (84 %) males (63 %) with sub-acute musculoskeletal conditions (median duration 67 days). Claimants undergoing FCE had ~15 % higher average functional work levels recommended at time of assessment (Mann-Whitney U = 4,391.0, p < 0.001) but differences at other follow-up times were smaller (0-8 %), in favour of functional interviewing, and not statistically significant. Clinically important improvement during rehabilitation in functional work level (0.9/4, SRM = 0.94), pain intensity (2.0/10, SRM = 0.88) and self-reported disability (21.8/100, SRM = 1.45) were only observed in those undergoing the functional interview.

CONCLUSIONS

Performance-based FCE integrated into occupational rehabilitation appears to lead to higher baseline functional work levels compared to a semi-structured functional interview, but not improved RTW rates or functional work levels at follow-up. Functional interviewing has potential for efficiency gains and higher likelihood of clinically important improvement following rehabilitation, however further research is needed.

Paraspinal muscle morphology and composition: a 15-yr longitudinal magnetic resonance imaging study

PURPOSE

The purposes of this study were to define the natural progression of age-related changes of the lumbar paraspinal muscles during adulthood and to investigate the influence of lifestyle and individual factors (e.g., physical activity levels at work and leisure, body mass index, and low back pain [LBP]).

METHODS

This population-based longitudinal study included a sample of 99 adult male twins. Data were collected through a structured interview, physical examination, and magnetic resonance imaging. Measurements of the lumbar multifidus and erector spinae muscles were obtained from T2-weighted axial images at L3-L4 and L5-S1 at baseline and 15-yr follow-up. Muscle cross-sectional area (CSA), functional CSA (FCSA) (fat-free mass), and FCSA/CSA (composition) as well as CSA and FCSA asymmetry and FCSA/CSA side-to-side differences were measured.

RESULTS

Subjects' mean ± SD age was 47.3 ± 7.4 yr at baseline and 62.3 ± 8.0 yr at follow-up. During the 15-yr period, both muscles exhibited a decrease in CSA and FCSA and an increase in fatty infiltration and side-to-side differences in size and composition at both spinal levels. Both muscles displayed greater changes at L5-S1 than L3-L4. Age and BMI were found to be significantly associated with the degree of paraspinal muscle changes over time. However, there was no association between the change in paraspinal muscle size, composition, or asymmetry with the level of physical demands at work or leisure or LBP history.

CONCLUSIONS

The present longitudinal study suggests that over adulthood, the multifidus and erector spinae undergo similar morphological changes. Moreover, our findings suggest that the long-term progression of lumbar paraspinal muscle changes evaluated through magnetic resonance imaging are not associated with the range of physical demand levels as were typical of Finnish men or LBP history.

Longitudinal construct validity and responsiveness of measures of walking capacity in individuals with lumbar spinal stenosis

BACKGROUND CONTEXT

Walking capacity is a primary outcome indicator for individuals with lumbar spinal stenosis (LSS). Therefore, there is a demand for psychometrically sound measures of walking that are responsive to change.

PURPOSE

The primary objective of this study was to examine longitudinal construct validity of the Physical Function Scale of the Swiss Spinal Stenosis Questionnaire (PF Scale), the Oswestry Disability Index (ODI), and the walking capacity items from these scales specifically for the assessment of walking capacity in LSS using the objective Self-Paced Walking Test (SPWT) as the external standard. A secondary objective was to examine responsiveness of measures of walking using a self-reported walking capacity change scale as the external criterion standard.

STUDY DESIGN

Patients were prospectively enrolled.

PATIENT SAMPLE

Twenty-six patients were included in this study (17 women and 9 men), with an average age of 68.5 years (SD, 9.2). All participants had LSS diagnosed by a spine specialist surgeon based on both clinical examination and imaging, as well as self-reported walking limitations (neurogenic claudication).

OUTCOME MEASURES

The self-reported outcome measures included in this study were PF Scale, ODI, and self-reported walking capacity change score.

FUNCTIONAL MEASURES

The functional measure used in the study was SPWT.

METHODS

Longitudinal construct validity was assessed using the correlational method. Internal responsiveness was examined using Guyatt responsiveness index and external responsiveness using receiver operating characteristic analysis. Change in the SPWT and the self-reported walking capacity change score were used as external criteria for the analysis.

RESULTS

The highest correlations with change in the SPWT were 0.78 for the ODI walking item and 0.78 for the walking capacity change score. Changes in the PF Scale and ODI score were correlated with change in the criterion SPWT at r=0.56 and r=0.70, respectively. There were no differences observed between the PF Scale and ODI for any of the responsiveness indices.

CONCLUSIONS

The PF Scale, ODI, and walking capacity change score are able to detect changes in walking capacity in people with LSS. The individual walking capacity item from the ODI appears to be the most valid and responsive to changes in measured walking and may be a reasonable alternative for measuring walking when an objective test such as the SPWT is not feasible.

Do variations in paraspinal muscle morphology and composition predict low back pain in men?

This longitudinal study aimed to clarify the longstanding controversy over whether variations in paraspinal muscle morphology (e.g., size, composition and asymmetry) are predictors of low back pain (LBP). A sample of 99 Finnish men were included in this population-based longitudinal study. Data were collected through a structured interview, physical examination and magnetic resonance imaging (MRI). Baseline measurements of the lumbar multifidus and erector spinae muscles were obtained from T2-weighted axial images at L3-L4 and L5-S1, and interview data were obtained at baseline, 1- and 15-year follow-ups. Few of the paraspinal muscle parameters investigated were predictors of change in LBP frequency, intensity or sciatica at 1- and 15-year follow-ups in the population-based sample, and findings were not consistent across muscles and spinal levels. However, greater multifidus and erector spinae fatty infiltration at L5-S1 was associated with a higher risk of having continued, frequent, persistent LBP at 1-year follow-up. None of the relationships observed was confounded by body mass index or the amount of physical activity at work or leisure. This longitudinal study provided evidence that variations in paraspinal muscle morphology on MRI have a limited, if not uncertain, role in the short- and long-term predictions of LBP in men.

Predictors of objectively measured walking capacity in people with degenerative lumbar spinal stenosis

BACKGROUND

Identifying factors associated with walking capacity in people with lumbar spinal stenosis (LSS) may provide a better understanding of neurogenic claudication and inform future rehabilitation research.

OBJECTIVE

To examine factors associated with objectively measured walking capacity in a sample of people with LSS and self-reported walking limitations.

METHODS

Participants included 49 individuals (65.8 years ± 10) who were at least 45 years of age with clinically diagnosed lumbar spinal stenosis (LSS) confirmed on MRI or CT imaging. All participants completed a Self-Paced Walking Test with visual analog pain scales and body diagrams before and immediately after walking. Questionnaires included the Physical Function and Symptom Severity Scales of the Swiss Spinal Stenosis Questionnaire, the Oswestry Disability Index (ODI) and the Health Utilities Index. Univariate linear relationships were examined, followed by development of a multivariate linear regression model with walking distance (m) as the dependent variable. A post-hoc analysis was also conducted including post-test symptom variables.

RESULTS

Variables retained from univariate analyses included years of leg pain, pre-test leg pain severity, the ODI, balance problems, and quality of life. When these variables were considered for a final model, only the ODI and balance problems were retained (R2=0.33). Other than balance, none of the pre-test symptom variables entered into the final model. Post-hoc analysis including post-test symptom variables found the presence and severity of post-test leg pain to be most highly associated with walking distance. In an explanatory model considering the ODI, balance and these two post-walking factors, only presence of post-test leg pain added to the model (R2=0.42).

CONCLUSIONS

Factors found to be most highly associated with walking capacity in LSS were self-reported, pain-related function (ODI), balance problems, and presence of leg pain immediately following walking.

Regional variations in trabecular architecture of the lumbar vertebra: associations with age, disc degeneration and disc space narrowing

Previous studies suggest that age and disc degeneration are associated with variations in vertebral trabecular architecture. In particular, disc space narrowing, a severe form of disc degeneration, may predispose the anterior portion of a vertebra to fracture. We studied 150 lumbar vertebrae and 209 intervertebral discs from 48 cadaveric lumbar spines of middle-aged men to investigate regional trabecular differences in relation to age, disc degeneration and disc narrowing. The degrees of disc degeneration and narrowing were evaluated using radiography and discography. The vertebrae were dried and scanned on a μCT system. The μCT images of each vertebral body were processed to include only vertebral trabeculae, which were first divided into superior and inferior regions, and further into central and peripheral regions, and then anterior and posterior regions. Structural analyses were performed to obtain trabecular microarchitecture measurements for each vertebral region. On average, the peripheral region had 12-15% greater trabecular bone volume fraction and trabecular thickness than the central region (p<0.01). Greater age was associated with better trabecular structure in the peripheral region relative to the central region. Moderate and severe disc degeneration were associated with higher trabecular thickness in the peripheral region of the vertebral trabeculae (p<0.05). The anterior region was of lower bone quality than the posterior region, which was not associated with age. Slight to moderate narrowing was associated with greater trabecular bone volume fraction in the anterior region of the inferior vertebra (p<0.05). Similarly, greater disc narrowing was associated with higher trabecular thickness in the anterior region (p<0.05). Better architecture of peripheral trabeculae relative to central trabeculae was associated with both age and disc degeneration. In contrast to the previous view that disc narrowing stress-shields the anterior vertebra, disc narrowing tended to associate with better trabecular architecture in the anterior region, as opposed to the posterior region.

Disc degeneration-related clinical phenotypes

The phenotype, or observable trait of interest, is at the core of studies identifying associated genetic variants and their functional pathways, as well as diagnostics. Yet, despite remarkable technological developments in genotyping and progress in genetic research, relatively little attention has been paid to the equally important issue of phenotype. This is especially true for disc degeneration-related disorders, and the concept of degenerative disc disease, in particular, where there is little consensus or uniformity of definition. Greater attention and rigour are clearly needed in the development of disc degeneration-related clinical phenotypes if we are to see more rapid advancements in knowledge of this area. When selecting phenotypes, a basic decision is whether to focus directly on the complex clinical phenotype (e.g. the clinical syndrome of spinal stenosis), which is ultimately of interest, or an intermediate phenotype (e.g. dural sac cross-sectional area). While both have advantages, it cannot be assumed that associated gene variants will be similarly relevant to both. Among other considerations are factors influencing phenotype identification, comorbidities that are often present, and measurement issues. Genodisc, the European research consortium project on disc-related clinical pathologies has adopted a strategy that will allow for the careful characterisation and examination of both the complex clinical phenotypes of interest and their components.

Genetics of disc-related disorders: current findings and lessons from other complex diseases

Disc-related disorders are highly genetic conditions with heritability estimates of up to 75 % and yet, few genomic locations have been moderately associated with the disorders. Candidate gene studies have shown possible disease associations on loci and genes of 1p21.1 (COL11A1), 6q27 (THBS2), 9q22.31 (ASPN), 10p12.31 (SKT), 20q11.2 (GDF5) and 20q13.12 (MMP9). More recently, in 2012, the first genome-wide association study revealed variants on loci and genes of 3p26.2, 6p21.32 (HLA region) and 6q26 (PARK2) that associate with disc-related disorders. In many other complex diseases, large meta-analyses of hundreds of thousands of study subjects and loci have revealed remarkable pathways. As methodology is evolving rapidly, we have already stepped into the era of routinely sequencing all bases in all human exons and we are approaching the era of sequencing the entire genome of study subjects with common diseases. The past decade has taught us that the common variants seen throughout populations seem to have low effects in many common diseases, explain relatively little of the overall heritability of the diseases and demand thousands of study subjects to identify associations. It seems that familial rare variants play an important role in many common diseases leading us back to valuing studies with large families and isolated populations. Moreover, careful characterization of environmental conditions are needed to explore and determine gene-environment interactions as genes that increase disease risk in one context may not do so under another context.

Morphometrics and lesions of vertebral end plates are associated with lumbar disc degeneration: evidence from cadaveric spines

BACKGROUND

Prior studies have suggested that vertebral end plate morphometrics and lesions may play a role in disc degeneration. However, most prior end plate studies have been based on radiographic images, and findings of associations between end plate morphometrics (measurements of size and shape) and disc degeneration remain controversial. The present study investigated the prevalence of vertebral end plate lesions and determined end plate morphometrics through direct measurements of cadaveric spines, and it examined the association of these factors with disc degeneration.

METHODS

We studied 600 vertebral end plates and 313 intervertebral discs from the cadaveric lumbosacral spines of seventy-six men (mean age, fifty-one years). Discography was performed to evaluate disc degeneration as indicated by disruption of the anulus fibrosus. The shape of the vertebral end plate and the presence of any lesions were visually evaluated. Lesions were rated as absent, small to moderate, or large. In addition, each end plate was digitized to quantify its area, circularity, and concavity. The association of end plate morphometrics and lesions with disc degeneration was examined.

RESULTS

Vertebral end plate lesions were found in 72% (fifty-five) of the seventy-six lumbar spines and in 32.8% (197) of the 600 end plates. The presence of end plate lesions was associated with disc degeneration, with larger lesions being associated with more severe disc degeneration (odds ratio, 2.31 for small to moderate lesions [p < 0.01] and 3.54 for large lesions [p < 0.001]). Greater end plate area was also associated with more severe disc degeneration (odds ratio, 1.2 per cm2 [p < 0.05]).

CONCLUSIONS

Vertebral end plate lesions were common and were associated with adjacent disc degeneration, with greater lesion size being associated with more severe disc degeneration. End plate morphometrics, particularly greater end plate size, may also play a role in the pathogenesis of disc degeneration.

Is level- and side-specific multifidus asymmetry a marker for lumbar disc pathology?

BACKGROUND CONTEXT

Several reports suggest that level- and side-specific multifidus atrophy or fat infiltration may be related to localized spinal pathology and symptoms. In particular, a study using a porcine model reported rapid level- and side-specific multifidus atrophy and adipocyte enlargement resulting from anterolateral disc or nerve root lesions.

PURPOSE

To investigate asymmetry in cross-sectional area (CSA) and fat infiltration in multifidus and other paraspinal muscles in patients with acute or subacute unilateral symptoms of radiculopathy and concordant posterolateral disc herniation. If multifidus asymmetry is indeed related to local pathology, this may serve as a marker for helping to target the search for less clearly identifiable pathology responsible for low back-related symptoms, which currently remains elusive in approximately 85% of those seeking care.

STUDY DESIGN

Cross-sectional observational study.

PATIENT SAMPLE

Subjects were patients referred to magnetic resonance imaging (MRI) with unilateral leg symptoms of less than 6 weeks onset suggestive of radiculopathy, with a consistent posterolateral lumbar disc herniation verified on imaging.

METHODS

Using T2-weighted axial MRI, measurements were obtained for total muscle CSA and signal intensity, functional (fat-free) CSA, and the ratio of functional CSA to total CSA.

RESULTS

Forty-three subjects met the inclusion criteria. The ratio of functional CSA to total muscle CSA was smaller on the side of the herniation than on the unaffected side, both below (mean 0.69 vs. 0.72, p=.007) and at the level of herniation (mean 0.78 vs. 0.80, p=.031). Multifidus signal intensity (fat infiltration) was greater on the side of the herniation at the level below the herniation (p=.014). Contrary to expectation, greater total multifidus CSA was found ipsilateral to the pathology at the level of herniation (p=.033). No asymmetries were found at the level above the herniation or in any other paraspinal muscles, with the exception of higher signal in the erector spinae at the level and side of herniation.

CONCLUSIONS

Multifidus may be particularly responsive to, or indicative of, localized lumbar disc or nerve root pathology within the first 6 weeks of symptoms as expressed through fat infiltration, but not through CSA asymmetry on MRI. However, such measurements are not reliable markers of lumbar pathology on an individual basis for use in clinical or research settings.

A morphological study of lumbar vertebral endplates: radiographic, visual and digital measurements

PURPOSE

Clinical observations suggest that endplate shape and size are related to complications of disc arthroplasty surgery. Yet, the morphology of the vertebral endplate has not been well defined. This study was conducted to characterize the morphology of lumbar vertebral endplates and to quantify their morphometrics using radiographic, visual and digital measures.

METHODS

A total of 591 vertebral endplates from 76 lumbosacral spines of men were studied (mean age 51.3 years). The shape of the vertebral endplates was classified as concave, flat and irregular, and was evaluated from both radiographs and cadaveric samples. Each endplate was further digitized using a laser scanner to quantify diameters, surface area and concavity for the whole endplate and its components (central endplate and epiphyseal rim). The morphological characteristics and morphometrics of the vertebral endplates were depicted.

RESULTS

In both radiographic and visual assessments, more cranial endplates (relative to the disc) were concave and more caudal endplates were flat at all disc levels (p < 0.001). On average, the mean concavity depth was 1.5 mm for the cranial endplate and 0.7 mm for the caudal endplate. From L1/2 down to L5/S1 discs, the vertebral endplate gradually changed into a more oval shape. The central endplate was approximately 70% of the diameter of the whole endplate and the width of the epiphyseal rim varied from 3 to 7 mm.

CONCLUSIONS

There is marked morphological asymmetry between the two adjacent endplates of a lumbar intervertebral disc: the cranial endplate is more concave than the caudal endplate. The size and shape of the vertebral endplate also vary considerably between the upper and lower lumbar regions.

Modic changes: prevalence, distribution patterns, and association with age in white men

BACKGROUND CONTEXT

Suspected as a cause of back pain, Modic changes (MCs) have received increasing attention in spine research and care. Yet, epidemiologic knowledge of MCs based on the general population, which may provide an important clinical reference, is limited.

PURPOSE

To investigate the prevalence and distribution patterns of MCs in the lumbosacral spine and their associations with age in a large population-based sample of men.

STUDY DESIGN

An epidemiologic investigation of lumbar magnetic resonance images (MRIs).

PATIENT SAMPLE

This study was based on the Twin Spine Study database, comprising a sample of male twins shown to be largely representative of the base Finnish population. Lumbar spine MRIs (1.5 Tesla Magnetom; Siemens AG, Erlangen, Germany) of 561 subjects (mean age, 49.8 years; range, 35-70 years) were included in the present study.

METHODS

For each spine, all 11 end plates (L1-S1) in the lumbar region were evaluated using both T1- and T2-weighted images to identify MCs, which were classified into Type 1, 2, 3, and mixed types. Furthermore, the number and location of MCs were recorded, as well as the anteroposterior (AP) and transverse sizes, to explore the prevalence and distribution pattern of MCs in the lumbar region and associations with age.

RESULTS

Modic changes were identified in 55.6% (312) of individuals and 13.5% (830) of end plates studied. Among these MCs, 64.2% (533) were Type 2, 16.0% (133) were Type 1, 18.1% (150) were Mixed Type 1/2, and the remaining 1.6% (13) were noted as Type 3 or Mixed Type 2/3. Modic changes were more common in the lower (74.5%) than in the upper lumbar region (25.5%), and 77.9% (642) of MCs presented in pairs at opposing end plates of a disc. Moreover, the specific type of MCs on opposing end plates was usually concordant. The presence of MCs in the lumbar region was associated with age (odds ratio=1.05-1.08 for each additional year of age, depending on type of MCs, p<.001). In addition, greater age was associated with a greater number of end plates affected and MCs of larger size (p<.001).

CONCLUSIONS

Modic changes are common MRI findings in the lumbar spines of middle-aged white men, with Type 2 MCs predominating. Mainly present in the lower lumbar region, MCs tend to affect both end plates adjacent to a disc simultaneously, and they commonly involve the entire AP diameter of the vertebral end plate. The presence and size of MCs are clearly related to age, suggesting that aging or associated factors may play an essential role in the pathogenesis of MCs.

Health-related quality of life and comorbidities associated with lumbar spinal stenosis

BACKGROUND CONTEXT

Spinal stenosis is one of the most commonly diagnosed pathologies of the lumbar spine and the leading indication for spine surgery in adults aged 65 years and older. Yet, the burden of lumbar spinal stenosis (LSS) alone, and in combination with common comorbidities, on health-related quality of life (HRQL) is unknown as are comorbidities specifically associated with this chronic condition.

PURPOSE

To estimate the illness burden of LSS on HRQL, adjusting for the effects of specific comorbidities, age, and gender, and investigate whether specific comorbidities are associated with the condition.

STUDY DESIGN/SETTING

A community-based cohort of 245 patients diagnosed with LSS was assembled and compared with a representative sample of 7,489 adults from the base population of Albertans responding to the Canadian Community Health Survey on HRQL and comorbidities.

METHODS

Health-related quality-of-life data were acquired through interviews for both groups using the Health Utilities Index Mark 3 (HUI3). Both groups were also queried about the presence of 13 specific chronic conditions. Linear regression was used to model HUI3 scores as a function of group, age, gender, and specific comorbid conditions. Logistic regression was used to compare the odds of having particular comorbid conditions between the LSS and general population groups.

RESULTS

The mean unadjusted overall HUI3 scores were 0.60 for the LSS group and 0.85 for the general population (1=perfect health). After adjustment, HRQL deficits four times that deemed a clinically important difference remained between the groups. Controlling age and gender, the prevalence of arthritis, migraines, hypertension, and incontinence was significantly greater in the LSS group as compared with the general population sample.

CONCLUSIONS

Diagnosed LSS is associated with a very substantial burden of illness that is compounded by associated comorbidities, with implications for clinical care, health-care policy decisions, and research. Attention to comorbidities is particularly important in LSS.