Challenging the cumulative injury model: positive effects of greater body mass on disc degeneration

Causal relationship between basal metabolic rate and intervertebral disc degeneration: a Mendelian randomization study

BACKGROUND

The role of basal metabolic rate (BMR) in intervertebral disc degeneration (IVDD) is still uncertain. To address this gap, we conducted a Mendelian randomization (MR) study to comprehensively explore the causal relationship between BMR and IVDD.

METHODS

BMR data were obtained from a large genome-wide association study (GWAS) database, while IVDD data were derived from the FinnGen project. The causal relationship between IVDD and BMR was investigated using MR, with inverse-variance weighting (IVW) as the primary estimate. MR-Egger weighed median and weighed mode were employed for robustness. Sensitivity analyses, including the Cochran Q test, leave-one-out analysis, and MR-Egger intercept analysis, were conducted. Furthermore, the study also identified causal relationships between IVDD and factors associated with BMR (hyperthyroidism, type 2 diabetes, standing height, weight, and body mass index). Multivariable MR was applied to further assess the direct effect of BMR on IVDD.

RESULTS

Genetic predisposition to BMR (after removing outliers OR: 1.49; 95% CI: 1.37-1.63; P = 5.073e-21) were associated with an increased risk of IVDD. Additionally, IVDD risk increased with greater height, weight, and BMI. No causal relationship was observed between hy/thy and T2D and intervertebral disc degeneration (IVDD) (P > 0.05). In multivariable MR, a significant causal association between BMR and IVDD persisted, even after adjusting for BMI, height, and weight.

CONCLUSION

In this study, we successfully identified that a higher BMR is independently and causally linked to IVDD, indicating an increased risk of developing IVDD. These findings suggest that managing BMR could potentially mitigate the risk of IVDD.

Patient-related risk factors and lifestyle factors for lumbar degenerative disc disease: a systematic review

OBJECTIVE

Back pain is a very widespread disease pattern and is one of the most frequent causes for consultation of a physician in general. In most cases, discogenic changes are the pathomorphological correlate of back pain. Numerous risk factors have been identified for these degenerative changes, but the influence and significance of the risk factors remain unclear, which was the aim of this systematic review.

METHODS

A systematic literature search of the commonly used Pubmed database was performed using specific MESH terms. Further selection of the included studies was performed according to the PRISMA scheme, taking into account scientific merit as well as the relation to the research question.

RESULTS

A total of 111 studies out of 1035 found were finally included in the literature search. 134 risk factors for disc degeneration and disc herniation were identified. These were divided into (1) patient-specific risk factors (n░=░34), (2) radiological risk factors (n░=░31), (3) lifestyle risk factors (n░=░6), (4) workplace-related risk factors (n░=░12), (5) genetic risk factors (n░=░50), and (6) other risk factors (n░=░1). Non-adjustable risk factors were age >50 years (OR 1.7/year), female gender (OR 1.41), family disposition (OR 4.0), comorbidities like atherosclerosis (OR 2.24), arthritic changes in other joints (OR 3.1) and history of injuries of the back (OR 3.1). Adjustable factors were elevated BMI (OR 2.77), comorbidities like hypertension (OR 1.25), dyslipidemia (OR 1.26) and diabetes mellitus (OR 6.8), as well as lifestyle habits like smoking (OR 3.8).

DISCUSSION

In summary, intervertebral disc degenerations and herniations represent multifactorial events whose risk factors can be partly influenced and partly not influenced. This systematic review highlights the current state of knowledge as a basis for creating patient-specific algorithms to calculate risk for the development or progression of degenerative disc changes and disc herniations.

Relationship between lumbar disc degeneration on MRI and low back pain: A cross-sectional community study

Purpose:

Although an association has been suggested between disc degeneration (DD) and low back pain (LBP), some DD is thought to be an age-related change unrelated to symptoms. Age-inappropriate DD, however, may be associated with LBP. The purpose of this study was to investigate whether there is a difference in LBP and LBP-related quality of life between age-appropriate and age-inappropriate DD, as assessed by magnetic resonance imaging (MRI).

Participants and methods:

In this cross-sectional study, degenerative change in the lumbar intervertebral discs of 382 subjects (age range, 27-82 years) was evaluated by MRI. Degenerative Disc Disease (DDD) scores were assigned using the Schneiderman classification, as the sum of grades for all intervertebral levels (0-15). We classified subjects into three groups according to age and DDD score: Low DD (mild DD relative to age), Appropriate (age-appropriate DD), and High DD (severe DD relative to age). We compared the three groups in terms of LBP prevalence, LBP intensity, LBP-specific quality of life (QOL) according to the Roland-Morris Disability Questionnaire (RDQ), and the Short Form-36 Item Health Survey (SF-36).

Results:

Of 382 subjects, there were 35% in the Low DD group, 54% in the Appropriate group, and 11% in the High DD group. There were no significant differences among the groups in terms of prevalence of LBP, LBP intensity, RDQ score, or SF-36 score.

Conclusion:

No association was found between age-inappropriate DD (Low or High DD group) and age-appropriate DD (Appropriate group) in terms of prevalence of LBP, LBP intensity, RDQ, or SF-36.

Anemia was associated with multilevel lumbar disc degeneration in patients with low back pain: a single-center retrospective study

PURPOSE

It has not been determined which factors were related to multilevel lumbar disc degeneration (MLDD). The objective of this study was to determine the prevalence of MLDD among symptomatic patients using the magnetic resonance imaging method. The study also aimed to clarify the associations between MLDD and suspected risk factors through a multivariate model.

METHODS

A total of 530 young and middle-aged patients, suffered from low back pain were retrospectively assessed by 2 independent observers, who used sagittal T2-weighted MR imaging. Subjects were divided into two groups, MLDD group and non-MLDD group, according to the number of degenerated discs. Demographic and radiological data included age, gender, weight, height, body mass index, smoking status, alcohol drinking, lumbar lordosis, presence of hypertension (HT), diabetes mellitus and anemia.

RESULTS

There were 309 men and 221 women with an average age of 37.5  ±  8.5 years. In general, 37.7% of patients were diagnosed with disc degeneration (DD) at more than two levels. Triple level DD was the most common pattern and was more prevalent in women (p <0.05). Using multivariate analyses, age (odds ratio [OR]: 1.14; 95% confidence interval [CI] 1.11-1.18; p <0.001), hypertension (OR: 2.67; 95% CI 1.38-5.16; p = 0.03) and anemia (OR: 3.84; 95% CI 2.03-7.28; p <0.001) were significantly associated with MLDD.

CONCLUSION

Despite the young age of this cohort, MLDD is common among patients with low back pain. A significant independent association exists between age, HT, anemia and multilevel disc degeneration in the lumbar region.

ISSLS Prize in Bioengineering Science 2022: low rate cyclic loading as a therapeutic strategy for intervertebral disc regeneration

BACKGROUND

The intervertebral disc degenerates with age and has a poor propensity for regeneration. Small molecule transport plays a key role in long-term degradation and repair. Convection (bulk flow), induced by low rate cyclic loading of the intervertebral disc, has been shown to increase transport of small molecules. However, the potential therapeutic benefit of low rate cyclic loading on degenerated discs has not been described. The purpose of this study was to determine if a sustained (daily) low rate cyclic loading regimen could slow, arrest, or reverse intervertebral disc degeneration in the rabbit lumbar spine.

METHODS

Fifty-six New Zealand white rabbits (>12 months old) were designated as either Control (no disc puncture), 8D (disc puncture followed by 8 weeks of degeneration), 16D (disc puncture followed by 16 weeks of degeneration), or Therapy (disc puncture followed by 8 weeks of degeneration and then 8 weeks of daily low rate cyclic loading). Specimens were evaluated by T2 mapping, Pfirrmann scale grading, nucleus volume, disc height index, disc morphology and structure, and proteoglycan content.

RESULTS

In every metric, mean values for the Therapy group fell between Controls and 8D animals. These results suggest that sustained low rate cyclic loading had a therapeutic effect on the already degenerated disc and the regimen promoted signs of regeneration. If these results translate clinically, this approach could fulfil a significant clinical need by providing a means of non-invasively treating intervertebral disc degeneration.

Association between severe lumbar disc degeneration and self-reported occupational physical loading

Objectives

Occupational physical loading has been reported to be associated with intervertebral disc degeneration. However, previous literature reports inconsistent results for different vertebral levels. The aim of our study was to investigate the association between lumbar disc degeneration (LDD) at different vertebral levels and the self‐reported physical loading of occupation.

Methods

The study population consisted of 1,022 postmenopausal women and was based on the prospective Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study cohort. The severity of LDD was graded from T2‐weighted MRI images using the five‐grade Pfirrmann classification. Five intervertebral levels (L1–L2 to L5–S1) were studied (total 5110 discs). The self‐rated occupational physical loading contained four groups: sedentary, light, moderate, and heavy.

Results

The heavy occupational physical loading group had higher odds for severe LDD at the L5–S1 vertebral level (OR 1.86, 95% CI: 1.19–2.92, p = .006) in comparison with the sedentary work group. A clear trend of increasing disc degeneration with heavier occupational loading was also observed at the L5–S1 level. Age, smoking, and higher body mass index (BMI) were associated with more severe LDD. Leisure‐time physical activity at the age of 11–17 years was associated with less severe LDD. Controlling for confounding factors did not alter the results.

Conclusions

There appears to be an association between occupational physical loading and severe disc degeneration at the lower lumbar spine in postmenopausal women. Individuals in occupations with heavy physical loading may have an increased risk for work‐related disability due to more severe disc degeneration.

Mechanical loading influences the lumbar intervertebral disc. A cross-sectional study in 308 athletes and 71 controls

There is evidence in animal populations that loading and exercise can positively impact the intervertebral disc (IVD). However, there is a paucity of information in humans. We examined the lumbar IVDs in 308 young athletes across six sporting groups (baseball, swimming, basketball, kendo, soccer, and running; mean age 19 years) and 71 nonathletic controls. IVD status was quantified via the ratio of IVD to vertebral body height (IVD hypertrophy) and ratio of signal intensity in the nucleus to that in the annulus signal (IVD nucleus hydration) on sagittal T2-weighted magnetic resonance imaging. P values were adjusted via the false discovery rate method to mitigate false positives. In examining the whole collective, compared to referents, there was evidence of IVD hypertrophy in basketball (P ≤ .029), swimming (P ≤ .010), soccer (P = .036), and baseball (P = .011) with greater IVD nucleus hydration in soccer (P = .007). After matching participants based on back-pain status and body height, basketball players showed evidence of IVD hypertrophy (P ≤ .043) and soccer players greater IVD nucleus hydration (P = .001) than referents. Greater career duration and training volume correlated with less (ie, worse) IVD nucleus hydration, but explained less than 1% of the variance in this parameter. In this young collective, increasing age was associated with increased IVD height. The findings suggest that basketball and soccer may be associated with beneficial adaptations in the IVDs in young athletes. In line with evidence on other tissues, such as muscle and bone, the current study adds to evidence that specific loading types may beneficially modulate lumbar IVD properties.

Increasing BMI increases lumbar intervertebral disc deformation following a treadmill walking stress test

High body mass index (BMI) and obesity have been implicated as risk factors for lumbar degenerative disc disease and low back pain. Despite this, there is limited in vivo data to quantify how obesity influences the mechanical function of intervertebral discs (IVD) in response to activities of daily living. Recently, our lab has developed methodologies to non-invasively measure in vivo IVD deformation resulting from activities of daily living using magnetic resonance (MR) imaging and solid modeling techniques. This pilot study expands on these methodologies to assess how BMI influences IVD deformation following treadmill walking in eight asymptomatic individuals. Ordinary least squares regression analyses revealed a statistically significant relationship between BMI and compressive deformation (strain (%)) in the L5-S1 IVD (R² = 0.61, p < 0.05). This relationship was weaker in the L3-L4 (R² = 0.28, p > 0.05) and L4-L5 IVDs (R² = 0.28, p > 0.05). Importantly, no relationship between pre-exercise disc height and BMI was identified (p > 0.05). Therefore, the results of this study suggest that BMI may alter the mechanical response of lumbar spine IVDs, particularly at the L5-S1 level. Furthermore, the observed relationship between increased BMI and IVD compressive deformation, in the absence of a detected relationship between pre-exercise disc height and BMI, suggests that changes in IVD mechanical function may be more sensitive to alterations in disc health than static clinical imaging alone. This finding highlights the importance of quantifying disc mechanical function when examining the relationship between BMI and IVD degeneration.

Causal Associations of Obesity With the Intervertebral Degeneration, Low Back Pain, and Sciatica: A Two-Sample Mendelian Randomization Study

The role of obesity in the development of dorsopathies is still unclear. In this study, we assessed the associations between body mass index (BMI) and several dorsopathies including intervertebral disc degeneration (IVDD), low back pain (LBP), and sciatica by using the Mendelian randomization method. We also assessed the effect of several obesity-related traits on the same outcomes. Single-nucleotide polymorphisms associated with the exposures are extracted from summary-level datasets of previously published genome-wide association studies. Summary-level results of IVDD, LBP, and sciatica were from FinnGen. In our univariable Mendelian randomization analysis, BMI is significantly associated with increased risks of all dorsopathies including sciatica (OR = 1.33, 95% CI, 1.21-1.47, p = 5.19 × 10^-9), LBP (OR = 1.28, 95% CI, 1.18-1.39, p = 6.60 × 10^-9), and IVDD (OR = 1.23, 95% CI, 1.14-1.32, p = 2.48 × 10^-8). Waist circumference, hip circumference, whole-body fat mass, fat-free mass, and fat percentage, but not waist-hip ratio, were causally associated with increased risks of IVDD and sciatica. Higher hip circumference, whole-body fat mass, fat-free mass, and fat percentage increased the risk of LBP. However, only whole-body fat-free mass remained to have a significant association with the risk of IVDD after adjusting for BMI with an odds ratio of 1.57 (95% CI, 1.32-1.86, p = 2.47 × 10^-7). Proportions of BMI's effect on IVDD, sciatica, and LBP mediated by leisure sedentary behavior were 41.4% (95% CI, 21.8%, 64.8%), 33.8% (95% CI, 17.5%, 53.4%), and 49.7% (95% CI, 29.4%, 73.5%), respectively. This study provides evidence that high BMI has causal associations with risks of various dorsopathies. Weight control is a good measure to prevent the development of dorsopathies, especially in the obese population.

Comparison of different lifting analysis tools in estimating lower spinal loads - Evaluation of NIOSH criterion

Excessive loads on the human spine is recognized as a risk factor for back injuries/pain. Various lifting analysis tools such as musculoskeletal models, regression equations and NIOSH (National Institute for Occupational Safety and Health) lifting equation (NLE) have been proposed to evaluate and mitigate associated risks during manual material handling activities. Present study aims to compare predicted spinal loads from 5 different lifting analysis tools as well as to critically evaluate the NIOSH recommended weight limit (RWL). Spinal loads were estimated under different symmetric/asymmetric lifting tasks in which hand-load mass at each task was set based on RWL from NLE. Estimated intradiscal pressures (IDPs) of various tools were also compared with in vivo measurements. We compared RWL by NLE versus our estimations of RWL calculated from our regression equations using biomechanical criteria (compression <3400 N with/without shear <1000, 1250 or 1500 N). Our regression equations followed by OpenSim, AnyBody, simple polynomial and 3DSSPP satisfactorily predicted L4-L5 IDPs. Lifting analysis tools estimated comparable spinal compression forces (mean Pearson's r = 0.80; standard deviation of relative difference = 26%) while in shear, differences were greater (mean Pearson's r = 0.68; standard deviation of relative difference = 56%). NLE estimations of RWL were conservative in comparison with our estimations for lean individuals (BMI < 25 kg/m²) when compression <3400 N and shear <1250 N were considered as the biomechanical criteria. For heavier individuals, however, NLE estimations of RWL generated spinal compression >3400 N (NIOSH biomechanical safety threshold) as well as shear >1000 N. Although RWLs estimated by NLE was body weight independent, body weight substantially altered RWLs estimated from our regression equations. For improved estimation of the risk of injury, more accurate failure criteria for spinal segments are essential.

Characterization of Intervertebral Disc Changes in Asymptomatic Individuals with Distinct Physical Activity Histories Using Three Different Quantitative MRI Techniques

(1) Background: Assessments of intervertebral disc (IVD) changes, and IVD tissue adaptations due to physical activity, for example, remains challenging. Newer magnetic resonance imaging techniques can quantify detailed features of the IVD, where T2-mapping and T2-weighted (T2w) and Dixon imaging are potential candidates. Yet, their relative utility has not been examined. The performances of these techniques were investigated to characterize IVD differences in asymptomatic individuals with distinct physical activity histories. (2) Methods: In total, 101 participants (54 women) aged 25–35 years with distinct physical activity histories but without histories of spinal disease were included. T11/12 to L5/S1 IVDs were examined with sagittal T2-mapping, T2w and Dixon imaging. (3) Results: T2-mapping differentiated Pfirrmann grade-1 from all other grades (p < 0.001). Most importantly, T2-mapping was able to characterize IVD differences in individuals with different training histories (p < 0.005). Dixon displayed weak correlations with the Pfirrmann scale, but presented significantly higher water content in the IVDs of the long-distance runners (p < 0.005). (4) Conclusions: Findings suggested that T2-mapping best reflects IVD differences in asymptomatic individuals with distinct physical activity histories changes. Dixon characterized new aspects of IVD, probably associated with IVD hypertrophy. This complementary information may help us to better understand the biological function of the disc.

Leptin signaling and the intervertebral disc: Sex dependent effects of leptin receptor deficiency and Western diet on the spine in a type 2 diabetes mouse model

Type 2 diabetes and obesity are associated with back pain in juveniles and adults and are implicated in intervertebral disc (IVD) degeneration. Hypercaloric Western diets are associated with both obesity and type 2 diabetes. The objective of this study was to determine if obesity and type 2 diabetes result in spinal pathology in a sex-specific manner using in vivo diabetic and dietary mouse models. Leptin is an appetite-regulating hormone, and its deficiency leads to polyphagia, resulting in obesity and diabetes. Leptin is also associated with IVD degeneration, and increased expression of its receptor was identified in degenerated IVDs. We used young, leptin receptor deficient (Db/Db) mice to mimic the effect of diet and diabetes on adolescents. Db/Db and Control mice were fed either Western or Control diets, and were sacrificed at 3 months of age. Db/Db mice were obese, while only female mice developed diabetes. Female Db/Db mice displayed altered IVD morphology, with increased intradiscal notochordal band area, suggesting delayed IVD cell proliferation and differentiation, rather than IVD degeneration. Motion segments from Db/Db mice exhibited increased failure risk with decreased torsional failure strength. Db/Db mice also had inferior bone quality, which was most prominent in females. We conclude that obesity and diabetes due to impaired leptin signaling contribute to pathological changes in vertebrae, as well as an immature IVD phenotype, particularly of females, suggesting a sex-dependent role of leptin in the spine.

Long-term running in middle-aged men and intervertebral disc health, a cross-sectional pilot study

Purpose

To measure intervertebral disc (IVD) health parameters in middle-aged long-term runners compared to matched non-physically active controls.

Methods

Seventeen males aged 44-62yr were included in the study: 9 runners with a running history of >10yr, averaging >50km/week, and eight matched non-physically active controls, the data from one participant had to be excluded. T2-relaxometry, diffusion weighted imaging, T1- and T2-weighted MR scanning, as well as T2 time mapping were performed. Morphological data relating to IVD were extrapolated.

Results

Compared to controls on average, runners had 20% greater IVD height (p = 0.002) and seven percentage points greater IVD-vertebral body height ratio (p = 0.001). No significant differences were observed between groups for mean(SD) IVD hydration status, as indicated by similar T2-times (runners: 94.4(11.1)ms, controls: 88.6(23.6)ms), or apparent diffusion coefficients (runners: 249.0(175.2)mm²/s, controls: 202.3(149.5)mm²/s). Average Pfirrmann score for the L5-S1 IVD was 2.2(0.7) for runners and 3.3(1.0) for controls (p = 0.026), average scores for all lumbar levels (L2-S1) were 1.9(0.2) and 2.5(0.7), respectively (p = 0.036). Anterior annulus T2-time and overall average lumbar level Pfirrmann grades were strongly correlated (r = 0.787, p = 0.021 and r = -0.704, p = 0.034, respectively) with greater distances run per week. Average lumbar level Pfirrmann grades were also strongly correlated (r = -0.823, p = 0.006) to total years of running.

Conclusion

Middle-aged long-term endurance runners exhibit less age-related decline in their lumbar IVDs. In addition, the measures of IVD morphology appeared to be better in those who had been running for a greater number of years, as well as in those who ran a greater distance per week.

Immuohistochemical score of matrix metalloproteinase-1 may indicate the severity of symptomatic cervical and lumbar disc degeneration

BACKGROUND CONTEXT

Intervertebral disc (IVD) degeneration is related to numerous risk factors, including obesity. Leptin, one of the commonly measured adipokines, is proven to play an important role in the pathogenesis of IVD degeneration. In the context of IVD degeneration, matrix metalloproteinase-1 (MMP-1), which is upregulated and activated by leptin, is the most abundant catabolic enzyme. It remains unclear which of the factors mentioned above is most strongly associated with IVD degeneration.

PURPOSE

To investigate the influence of MMP-1 in IVD degeneration, we determined the strength of different predictors, including age, sex, magnetic resonance imaging (MRI), Modic changes (MCs), body mass index (BMI), leptin, and MMP-1. This was achieved by assessing the correlation among these factors and histologic degeneration score (HDS).

STUDY DESIGN

This study included 89 patients undergoing cervical discectomy for disc herniation, 93 who underwent lumbar discectomy, and 90 control subjects. Herniated disc tissue and plasma were used after the study was approved by the Human Ethics Review Committee at the authors' institution.

METHODS

Hematoxylin and eosin (H&E), Alcian blue-PAS and immunohistochemical (IHC) staining were performed to measure the expression levels of leptin and MMP-1. Circulating plasma levels of leptin and MMP-1 were measured using an enzyme-linked immunosorbent assay. To assess the correlation with HDS, measurements of age, sex, BMI, MRI scale, MCs scale, leptin/MMP-1 plasma concentration, and leptin/MMP-1 IHC expression were analyzed.

RESULTS

Patients with cervical or lumbar discectomy had significantly higher BMI than controls. Significantly more men than women were involved in the lumbar patients as compared with the cervical patients and the control subjects. After adjustment for age and sex, plasma leptin and leptin IHC score correlated significantly with BMI in patients with cervical or lumbar discectomy. Age, sex, MRI scale, MCs scale, and leptin/MMP-1 plasma concentration were not positively correlated with HDS. HDS was significantly associated with BMI, leptin IHC score, and MMP-1 IHC score. After a stepwise-multiple linear regression analysis to evaluate the strength of the correlations between HDS and various factors, only the MMP-1 IHC score demonstrated an independent association with HDS in patients with degeneration of the cervical or lumbar disc.

CONCLUSIONS

MMP-1 IHC score is an independent predictor of the severity of cervical or lumbar IVD degeneration.

CLINICAL SIGNIFICANCE

MMP-1 IHC score may be used as an indicator of IVD degeneration.

Intervertebral disc degeneration: A focus on obesity and type 2 diabetes

Obesity (OB) and type 2 diabetes (T2D) are among the most prevalent metabolic diseases. They currently affect a substantial part of the world population and are characterized by several systemic co-morbidities, including cardiovascular diseases, stroke, cancer, liver steatosis, and musculoskeletal disorders, by increasing the risk of developing osteoarthritis and intervertebral disc degeneration (IVDD). IVDD is a chronic, progressive process whose main features are disc dehydration, loss of disc height, and changes of load distribution across the spine, resulting in disc structure disruption and leading to low back pain onset. Given the high prevalence of these metabolic disorders and their association with IVDD, several studies have been conducted in order to investigate the causative role of biological and biomechanical characteristics proper to these conditions in the development of IVDD. This review aims to analyse the role of OB and T2D on IVDD, in order to clarify the pathophysiological drivers of the degenerative process and to delineate possible targets to which appropriate treatments may be addressed in the near future.

The association between occupational loading and spine degeneration on imaging - a systematic review and meta-analysis

Background

There are inconsistencies in findings regarding the relationship of occupational loading with spinal degeneration or structural damage. Thus, a systematic review was conducted to determine the current state of knowledge on the association of occupational loading and spine degeneration on imaging.

Methods

We performed electronic searches on MEDLINE, CINAHL and EMBASE. We included cross-sectional, case control and cohort studies evaluating occupational loading as the exposure and lumbar spine structural findings on imaging as the outcomes. When possible, results were pooled.

Results

Seventeen studies were included in the review. Ten studies evaluated the association of occupational loading with disc degeneration (signal intensity), four of which were pooled into a meta-analysis. Of the 10 studies, only two did not identify a relationship between occupation loading and disc degeneration. A meta-analysis including four of the studies demonstrated an association between higher loading and degeneration for all spinal levels, with odds ratios between 1.6 and 3.3. Seven studies evaluated disc height narrowing and seven evaluate disc bulge, with six and five identifying an association of loading and with imaging findings respectively. Three studies evaluated modic changes and one identified and association with occupational load.

Conclusions

There was moderate evidence suggesting a modest association between occupational loading and disc degeneration (signal intensity), and low-quality evidence of an association between occupational loading and disc narrowing and bulging.

Molecular Relationships among Obesity, Inflammation and Intervertebral Disc Degeneration: Are Adipokines the Common Link?

Intervertebral disc degeneration (IVDD) is a chronic, expensive, and high-incidence musculoskeletal disorder largely responsible for back/neck and radicular-related pain. It is characterized by progressive degenerative damage of intervertebral tissues along with metabolic alterations of all other vertebral tissues. Despite the high socio-economic impact of IVDD, little is known about its etiology and pathogenesis, and currently, no cure or specific treatments are available. Recent evidence indicates that besides abnormal and excessive mechanical loading, inflammation may be a crucial player in IVDD. Furthermore, obese adipose tissue is characterized by a persistent and low-grade production of systemic pro-inflammatory factors. In this context, chronic low-grade inflammation associated with obesity has been hypothesized as an important contributor to IVDD through different, but still unknown, mechanisms. Adipokines, such as leptin, produced prevalently by white adipose tissues, but also by other cells of mesenchymal origin, particularly cartilage and bone, are cytokine-like hormones involved in important physiologic and pathophysiological processes. Although initially restricted to metabolic functions, adipokines are now viewed as key players of the innate and adaptative immune system and active modulators of the acute and chronic inflammatory response. The goal of this review is to summarize the most recent findings regarding the interrelationships among inflammation, obesity and the pathogenic mechanisms involved in the IVDD, with particular emphasis on the contribution of adipokines and their potential as future therapeutic targets.

Inciting Events Associated With Cervical Radiculopathy

BACKGROUND

Cervical radiculopathy (CR) is a clinical diagnosis defined as a combination of neck, shoulder, and arm pain, often accompanied by sensory and motor symptoms. CR is often caused by degenerative spine pathology associated with impingement of a cervical nerve root, and this pathology can be visualized using magnetic resonance imaging (MRI) or computed tomography (CT). [Correction added September 4, 2019, after online publication: 'computer tomography' corrected to 'computed tomography'] Factors that are associated with the onset of CR have not been explored.

OBJECTIVE

To investigate the types and frequencies of patient-reported inciting events associated with CR in patients with imaged-confirmed pathologies that correlate with symptoms.

DESIGN

Prospective observational case series.

SETTING

Two spine physiatry and three orthopedic spine surgery practices.

PATIENTS

One hundred twenty-two patients with symptoms suggestive of CR were recruited. Of these, 107 patients had MRI or CT evidence of cervical disk herniation or foraminal stenosis that correlated with symptoms and matched our inclusion criteria.

METHODS

We categorized patient-reported inciting events associated with onset of CR into six categories reflecting increasing severity of inciting event, and recorded the clinical characteristics, physical examination findings, pain intensity, and disability. We analyzed the characteristics of patients based on subgroups of inciting events.

RESULTS

Two-thirds of patients reported that they either awoke with symptoms or symptoms began without a memorable event, and one-third of patients reported inciting physical activity or trauma associated with the onset of CR. Clinical characteristics of CR were not influenced by categories of inciting events.

CONCLUSION

Most CR with correlating spine pathology was found to have onset without a specific inciting events. Furthermore, physical inciting events did not influence the severity of clinical manifestation of CR.

LEVEL OF EVIDENCE

IV.

The Role of Adipokines in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) is an important cause of low back pain. Recent evidence suggests that in addition to abnormal and excessive mechanical loading, inflammation may be a key driver for both IDD and low back pain. Obesity, a known mechanical risk factor of IDD, is now increasingly being recognized as a systemic inflammatory state with adipokines being postulated as likely inflammatory mediators. The aim of this review was to summarize the current literature regarding the inflammatory role of adipokines in the pathophysiology of IDD. A systematic literature search was performed using the OVID Medline, EMBASE and PubMed databases to identify all studies assessing IDD and adipokines. Fifteen studies were included in the present review. Leptin was the most commonly assessed adipokine. Ten of 15 studies were conducted in humans; three in rats and two in both humans and rats. Studies focused on a variety of topics ranging from receptor identification, pathway analysis, genetic associations, and proteonomics. Currently, data from both human and animal experiments demonstrate significant effects of leptin and adiponectin on the internal milieu of intervertebral discs. However, future studies are needed to determine the molecular pathway relationships between adipokines in the pathophysiology of IDD as avenues for future therapeutic targets.

[Impact of obesity in the pathophysiology of degenerative disk disease and in the morbidity and outcome of lumbar spine surgery]

Obesity (BMI>30Kg/m²) is a pandemic with severe medical and financial implications. There is growing evidence that relates certain metabolic processes within the adipose tissue, preferentially abdominal fat, with a low-intensity chronic inflammatory state mediated by adipokines and other substances that favor disk disease and chronic low back pain. Obesity greatly conditions both the preoperative evaluation and the spinal surgical technique itself. Some meta-analyses have confirmed an increase of complications following lumbar spine surgery (mainly infections and venous thrombosis) in obese subjects. However, functional outcomes after lumbar spine surgery are favorable although inferior to the non-obese population, acknowledging that obese patients present with worse baseline function levels and the prognosis of conservatively treated obese cohorts is much worse. The impact of preoperative weight loss in spine surgery has not been prospectively studied in these patients.

Running exercise strengthens the intervertebral disc

There is currently no evidence that the intervertebral discs (IVDs) can respond positively to exercise in humans. Some authors have argued that IVD metabolism in humans is too slow to respond anabolically to exercise within the human lifespan. Here we show that chronic running exercise in men and women is associated with better IVD composition (hydration and proteoglycan content) and with IVD hypertrophy. Via quantitative assessment of physical activity we further find that accelerations at fast walking and slow running (2 m/s), but not high-impact tasks, lower intensity walking or static positions, correlated to positive IVD characteristics. These findings represent the first evidence in humans that exercise can be beneficial for the IVD and provide support for the notion that specific exercise protocols may improve IVD material properties in the spine. We anticipate that our findings will be a starting point to better define exercise protocols and physical activity profiles for IVD anabolism in humans.

Preoperative estimation of disc herniation recurrence after microdiscectomy: predictive value of a multivariate model based on radiographic parameters

BACKGROUND CONTEXT

Recurrence of lumbar disc herniation (rLDH) is one of the unfavorable outcomes after microdiscectomy. Prediction of the patient population with increased risk of rLDH is important because patients may benefit from preventive measures or other surgical options.

PURPOSE

The study assessed preoperative factors associated with rLDH after microdiscectomy and created a mathematical model for estimation of chances for rLDH.

STUDY DESIGN/SETTING

This is a retrospective case-control study.

PATIENT SAMPLE

The study includes patients who underwent microdiscectomy for LDH.

OUTCOME MEASURES

Lumbar disc herniation recurrence was determined using magnetic resonance imaging.

METHODS

The study included 350 patients with LDH and a minimum of 3 years of follow-up. Patients underwent microdiscectomy for LDH at the L4-L5 and L5-S1 levels from 2008 to 2012. Patients were divided into two groups to identify predictors of recurrence: those who developed rLDH (n=50) within 3 years and those who did not develop rLDH (n=300) within the same follow-up period. Multivariate analysis was performed using patient baseline clinical and radiography data. Non-linear, multivariate, logistic regression analysis was used to build a predictive model.

RESULTS

Recurrence of LDH occurred within 1 to 48 months after microdiscectomy. Preoperatively, patients who developed rLDH were smokers (70% vs. 27%, p<.01; odds ratio [OR]=6.31, 95% confidence interval [CI]: 3.27-12.16) and had higher body mass index (29.0±6.1 vs. 27.0±4.3, p=.03; OR=1.09 per 0.01 unit change). Radiological parameters that were associated with rLDH were higher disc height index (0.35±0.007 vs. 0.26±0.002, p<.001), higher segmental range of motion (9.8±0.28° vs. 7.6±0.11°, p<.001; OR=0.53 per 0.01 unit change), and lower central angle of lumbar lordosis (33.4±0.81° vs. 47.1±0.47°, p<.001; OR=0.53 per 0.01 unit change). Additionally, Pfirrmann grade 3 (OR=16.62, 95% CI: 8.10-34.11), protrusion type of LDH (OR=5.90, 95% CI: 3.06-11.36), and Grogan sclerosis grades 3 and 4 (OR=4.81, 95% CI: 2.50-9.22) were also associated with rLDH. Multivariate non-linear modeling allowed for more accurate prediction of rLDH (90% correct prediction of rLDH; 99% correct prediction of no rLDH) than other univariate logit models.

CONCLUSIONS

Preoperative radiographic parameters in patients with LDH can be used to assess the risk of recurrence after microdiscectomy. The multifactorial non-linear model provided more accurate rLDH probability estimation than the univariate analyses. The software developed from this model may be implemented during patient counseling or decision making when choosing the type of primary surgery for LDH.

Porosity and Thickness of the Vertebral Endplate Depend on Local Mechanical Loading

STUDY DESIGN

Mechanical and microcomputed tomography (micro-CT) study of cadaver spines.

OBJECTIVE

To compare porosity and thickness of vertebral endplates with (1) compressive stresses measured in adjacent intervertebral discs and (2) grade of disc degeneration.

SUMMARY OF BACKGROUND DATA

Endplate porosity is important for disc metabolite transport, and yet porosity increases with age and disc degeneration. We hypothesize that porosity is largely determined by mechanical loading from adjacent discs.

METHODS

Forty motion segments (T8-9 to L4-5) were dissected from 23 cadavers aged 48 to 98 years. Each was subjected to 1 kN compression during which time intradiscal stresses were measured by pulling a pressure transducer along the disc's midsagittal diameter. "Stress profiles" revealed the average pressure in the nucleus, and the maximum stress in the anterior and posterior annulus. Specimens were further dissected to obtain discs with endplates (and 5 mm of bone) on either side. Microcomputed tomography scans (resolution 35 μm) were analyzed to calculate thickness and porosity in the midsagittal regions of all 80 endplates. Average values for the anterior, central, and posterior regions of each endplate were obtained. Disc degeneration was assessed macroscopically and microscopically.

RESULTS

Endplate porosity was inversely related to its thickness, being greatest in the central region opposite the nucleus, and least near the periphery. Superior endplates (relative to the disc) were 14% thicker (P < 0.001) and 4% less porous (P = 0.008) than inferior. In each of the 3 endplate regions (anterior, central, and posterior), porosity was inversely and significantly related to mechanical loading (pressure or maximum stress) in the adjacent disc region (P < 0.01 in all cases). Disc degeneration was best predicted by (reduced) nucleus pressure (R = 0.46, P < 0.001) and (reduced) maximum stress in the anterior annulus (R = 0.31, P < 0.001).

CONCLUSION

Mechanical loading is a major determinant of endplate thickness and porosity. Disc degeneration is more closely related to reduced disc stresses than to endplate thickness or porosity.

LEVEL OF EVIDENCE

N/A.

The relationship between obesity, low back pain, and lumbar disc degeneration when genetics and the environment are considered: a systematic review of twin studies

BACKGROUND CONTEXT

The relationships between obesity and low back pain (LBP) and lumbar disc degeneration (LDD) remain unclear. It is possible that familial factors, including genetics and early environment, affect these relationships.

PURPOSE

To investigate the relationship between obesity-related measures (eg, weight, body mass index [BMI]) and LBP and LDD using twin studies, where the effect of genetics and early environment can be controlled.

STUDY DESIGN

A systematic review with meta-analysis.

METHODS

MEDLINE, CINAHL, Scopus, Web of Science, and EMBASE databases were searched from the earliest records to August 2014. All cross-sectional and longitudinal observational twin studies identified by the search strategy were considered for inclusion. Two investigators independently assessed the eligibility, conducted the quality assessment, and extracted the data. Metaanalyses (fixed or random effects, as appropriate) were used to pool studies' estimates of association.

RESULTS

In total, 11 articles met the inclusion criteria. Five studies were included in the LBP analysis and seven in the LDD analysis. For the LBP analysis, pooling of the five studies showed that the risk of having LBP for individuals with the highest levels of BMI or weight was almost twice that of people with a lower BMI (odds ratio [OR] 1.8; 95% confidence interval [CI] 1.6-2.0; I(2)=0%). A dose-response relationship was also identified. When genetics and the effects of a shared early environment were adjusted for using a within-pair twin case-control analysis, pooling of three studies showed a reduced but statistically positive association between obesity and prevalence of LBP (OR 1.5; 95% CI 1.1-2.1; I(2)=0%). However, the association was further diminished and not significant (OR 1.4; 95% CI 0.8-2.3; I(2)=0%) when pooling included two studies on monozygotic twin pairs only. Seven studies met the inclusion criteria for LDD. When familial factors were not controlled for, body weight was positively associated with LDD in all five cross-sectional studies. Only two cross-sectional studies investigated the relationship between obesity-related measures and LDD accounting for familial factors, and the results were conflicting. One longitudinal study in LBP and three longitudinal studies in LDD found no increase in risk in obese individuals, whether or not familial factors were controlled for.

CONCLUSIONS

Findings from this review suggest that genetics and early environment are possible mechanisms underlying the relationship between obesity and LBP; however, a direct causal link between these conditions appears to be weak. Further longitudinal studies using the twin design are needed to better understand the complex mechanisms underlying the associations between obesity, LBP, and LDD.

The dose-response relationship between cumulative lifting load and lumbar disk degeneration based on magnetic resonance imaging findings

BACKGROUND

Lumbar disk degeneration (LDD) has been related to heavy physical loading. However, the quantification of the exposure has been controversial, and the dose-response relationship with the LDD has not been established.

OBJECTIVE

The purpose of this study was to investigate the dose-response relationship between lifetime cumulative lifting load and LDD.

DESIGN

This was a cross-sectional study.

METHODS

Every participant received assessments with a questionnaire, magnetic resonance imaging (MRI) of the lumbar spine, and estimation of lumbar disk compression load. The MRI assessments included assessment of disk dehydration, annulus tear, disk height narrowing, bulging, protrusion, extrusion, sequestration, degenerative and spondylolytic spondylolisthesis, foramina narrowing, and nerve root compression on each lumbar disk level. The compression load was predicted using a biomechanical software system.

RESULTS

A total of 553 participants were recruited in this study and categorized into tertiles by cumulative lifting load (ie, <4.0 × 10(5), 4.0 × 10(5) to 8.9 × 10(6), and ≥8.9 × 10(6) Nh). The risk of LDD increased with cumulative lifting load. The best dose-response relationships were found at the L5-S1 disk level, in which high cumulative lifting load was associated with elevated odds ratios of 2.5 (95% confidence interval [95% CI]=1.5, 4.1) for dehydration and 4.1 (95% CI=1.9, 10.1) for disk height narrowing compared with low lifting load. Participants exposed to intermediate lifting load had an increased odds ratio of 2.1 (95% CI=1.3, 3.3) for bulging compared with low lifting load. The tests for trend were significant.

LIMITATIONS

There is no "gold standard" assessment tool for measuring the lumbar compression load.

CONCLUSIONS

The results suggest a dose-response relationship between cumulative lifting load and LDD.

The interaction between aggrecan gene VNTR polymorphism and obesity in predicting incident symptomatic lumbar disc herniation

An association between aggrecan gene variable number of tandem repeats polymorphism (VNTR) and symptomatic lumbar disc herniation (LDH) has been reported in Chinese Han of Northern China, and obesity had previously been suspected of causing severe LDH. However, the interaction between aggrecan VNTR and obesity in symptomatic LDH has not been well studied. To examine the interaction between aggrecan VNTR and obesity in the susceptibility of symptomatic LDH, 259 participants participated in this study and donated a blood sample. The disease group comprised 61 patients already diagnosed with symptomatic LDH. The control group consisted of 198 healthy blood donors without symptoms of LDH who were not diagnosed with LDH. The aggrecan gene VNTR region was analyzed using polymerase chain reaction. The data indicated that between the two groups, participants carrying one or two alleles ≤25 repeats who were non-obese people showed a 1.057-fold increase in risk for symptomatic LDH (p = 0.895, changing the number of repeat alleles to <25 repeats alone did not demonstrably change the risk of LDH), and participants carrying two alleles >25 repeats who were obese people showed an 1.061-fold higher risk (p = 0.885, adding obesity to the mix alone did not demonstrably increase the risk of LDH), while participants carrying one or two alleles ≤25 repeats who were obese people showed a 4.667-fold increase in risk for symptomatic LDH (p = 0.0003, adding obesity plus changing the repeat allele number significantly increased the risk of LDH by 4.667). Overall, the findings suggest an underlying interaction between aggrecan VNTR and obesity in symptomatic LDH.

Obesity is associated with reduced disc height in the lumbar spine but not at the lumbosacral junction

STUDY DESIGN

Cross-sectional, community-based study.

OBJECTIVE

To investigate the relationships between obesity, disc height, and low back pain in the lumbosacral spine.

SUMMARY OF BACKGROUND DATA

Although obesity is a recognized risk factor for low back pain, our understanding of the mechanisms for this is limited. The evidence for an association between obesity and spinal structural changes is also conflicting.

METHODS

Seventy-two participants from a community-based study of musculoskeletal health underwent magnetic resonance imaging from the T12 vertebral body to the sacrum. Disc height was measured from L1-L2 to L5-S1. Body mass index was measured and low back pain in the previous 2 weeks was assessed.

RESULTS

The mean and total lumbar disc heights were reduced in obese individuals compared with nonobese individuals (mean height (standard error):1.04 (0.03) cm vs. 1.14 (0.02) cm, P = 0.01; total height (standard error):4.16 (0.11) cm vs. 4.57 (0.10) cm, P = 0.01), after adjusting for age, sex, and height. Although obesity was associated with reduced disc heights at the L1-L2 and L3-L4 levels, there were no significant relationship at the lumbosacral junction (mean difference (95% confidence interval [CI]):0.10 (-0.14 to 0.16) cm, P = 0.89). Both mean and total lumbar disc heights were negatively associated with recent pain after adjusting for age, sex, and height (mean height: mean difference (95% CI):0.09 (0.02-0.17) cm, P = 0.02; total height: mean difference (95% CI): 0.37 (0.07-0.66) cm, P = 0.02). However, these relationships were no longer significant when we also adjusted for weight (mean height; mean difference (95% CI):0.07(-0.009 to 0.15) cm, P = 0.08; total height: mean difference (95% CI):0.28 (-0.04 to 0.60) cm, P = 0.08). There were no significant relationships between disc height and recent pain at the lumbosacral junction.

CONCLUSION

Obesity was associated with reduced disc height in the lumbar spine, but not at the lumbosacral junction, suggesting these joints may have different risk factors. There was also evidence for an inter-relationship between obesity, lumbar disc height, and recent pain, suggesting that structural changes have a role in back pain and may in part explain the association between obesity and back pain.

Why do some intervertebral discs degenerate, when others (in the same spine) do not?

This review suggests why some discs degenerate rather than age normally. Intervertebral discs are avascular pads of fibrocartilage that allow movement between vertebral bodies. Human discs have a low cell density and a limited ability to adapt to mechanical demands. With increasing age, the matrix becomes yellowed, fibrous, and brittle, but if disc structure remains intact, there is little impairment in function, and minimal ingrowth of blood vessels or nerves. Approximately half of old lumbar discs degenerate in the sense of becoming physically disrupted. The posterior annulus and lower lumbar discs are most affected, presumably because they are most heavily loaded. Age and genetic inheritance can weaken discs to such an extent that they are physically disrupted during everyday activities. Damage to the endplate or annulus typically decompresses the nucleus, concentrates stress within the annulus, and allows ingrowth of nerves and blood vessels. Matrix disruption progresses by mechanical and biological means. The site of initial damage leads to two disc degeneration "phenotypes": endplate-driven degeneration is common in the upper lumbar and thoracic spine, and annulus-driven degeneration is common at L4-S1. Discogenic back pain can be initiated by tissue disruption, and amplified by inflammation and infection. Healing is possible in the outer annulus only, where cell density is highest. We conclude that some discs degenerate because they are disrupted by excessive mechanical loading. This can occur without trauma if tissues are weakened by age and genetic inheritance. Moderate mechanical loading, in contrast, strengthens all spinal tissues, including discs.

Disk degeneration and low back pain: are they fat-related conditions?

Low back pain (LBP) is the world's most debilitating condition. Disk degeneration has been regarded as a strong determinant associated with LBP. Overweight and obesity are public health concerns that affect every population worldwide and whose prevalence continues to rise. Studies have indicated strong associations between overweight/obesity and disk degeneration as well as with LBP. This broad narrative review article addresses the various mechanisms that may be involved leading to disk degeneration and/or LBP in the setting of overweight/obesity. In particular, our goal is to raise awareness of the role of fat cells and their involvement via altered metabolism or the release of adipokines as well as other pathways that may lead to the development of disk degeneration and LBP. Understanding the role of fat in this process may aid in the development of novel biological therapies and technologies to halt the progression or regenerate the disk. Moreover, with genetic advancements and the appreciation of genetic epidemiology, a more personalized approach to spine care may have to consider the role of fat in any preventative, therapeutic, and/or prognosis modalities toward the disk and LBP.

Association between overweight and low back pain: a population-based prospective cohort study of adolescents

STUDY DESIGN

A prospective cohort study in adolescents aged 7 to 19 years.

OBJECTIVE

To evaluate whether persistent overweight increases the risk of low back pain (LBP) among adolescents.

SUMMARY OF BACKGROUND DATA

Overweight and LBP are common health problems in adolescents. Their relationship is still controversial among adolescents, as well as among adults.

METHODS

The study population, the Oulu Back Study, was drawn from the Northern Finland Birth Cohort 1986. The final study sample included 1660 adolescents (56% females). The subcohort of 786 subjects (57% females) was used in the analysis of waist circumference. The association between the area under the curve of body mass index from 7 to 16 years, and from 16 to 18 years, and area under the curve of waist circumference from 16 to 19 years, and LBP during the past 6 months was evaluated separately for incident (reporting LBP at 18 or 19 yr but not at 16 yr) and persistent LBP (reporting LBP at 16 and 18 yr or 19 yr). Relative risks (RR) and their 95% confidence intervals (95% CI) were adjusted for smoking, leisure time physical activity, and family socioeconomic status at 16 years and stratified by sex.

RESULTS

Body mass index from 16 to 18 years among girls and body mass index from 7 to 16 years among boys predicted incident LBP at 18 years (girls: RR, 1.09; 95% CI, 1.01-1.18; boys: RR, 1.15; 95% CI, 1.00-1.32). Among boys, waist circumference from 16 to 19 years was also associated with incident LBP (RR, 1.16; 95% CI, 1.02-1.32). Overweight was not associated with persistent LBP.

CONCLUSION

In this population-based cohort study, persistent overweight slightly increased the risk of incident LBP, but the time period during which overweight was related to incident LBP differed between sexes.

LEVEL OF EVIDENCE

2.

Body mass index is associated with lumbar disc degeneration in young Finnish males: subsample of Northern Finland birth cohort study 1986

BACKGROUND

The role of environmental factors in lumbar intervertebral disc degeneration (DD) in young adults is largely unknown. Therefore, we investigated whether body mass index (BMI), smoking, and physical activity are associated with lumbar DD among young adults.

METHODS

The Oulu Back Study (OBS) is a subpopulation of the 1986 Northern Finland Birth Cohort (NFBC 1986) and it originally included 2,969 children. The OBS subjects received a postal questionnaire, and those who responded (N = 1,987) were invited to the physical examination. The participants (N = 874) were invited to lumbar MRI study. A total of 558 young adults (325 females and 233 males) underwent MRI that used a 1.5-T scanner at the mean age of 21. Each lumbar intervertebral disc was graded as normal (0), mildly (1), moderately (2), or severely (3) degenerated. We calculated a sum score of the lumbar DD, and analyzed the associations between environmental risk factors (smoking, physical activity and weight-related factors assessed at 16 and 19 years) and DD using ordinal logistic regression, the results being expressed as cumulative odds ratios (COR). All analyses were stratified by gender.

RESULTS

Of the 558 subjects, 256 (46%) had no DD, 117 (21%) had sum score of one, 93 (17%) sum score of two, and 92 (17%) sum score of three or higher. In the multivariate ordinal logistic regression model, BMI at 16 years (highest vs. lowest quartile) was associated with DD sum score among males (COR 2.35; 95% CI 1.19-4.65) but not among females (COR 1.29; 95% CI 0.72-2.32). Smoking of at least four pack-years was associated with DD among males, but not among females (COR 2.41; 95% CI 0.99-5.86 and 1.59; 95% 0.67-3.76, respectively). Self-reported physical activity was not associated with DD.

CONCLUSIONS

High BMI at 16 years was associated with lumbar DD at 21 years among young males but not among females. High pack-years of smoking showed a comparable association in males, while physical activity had no association with DD in either gender. These results suggest that environmental factors are associated with DD among young males.

Duration of fluoroscopic-guided spine interventions and radiation exposure is increased in overweight patients

BACKGROUND

The impact of patient body mass index (BMI) on image-guided spine interventions remains unknown. Higher BMI is known to complicate the acquisition of radiographic images. Therefore it can be hypothesized that the patient's body habitus can influence the delivery of a spinal injection.

OBJECTIVE

To quantify the impact of patient BMI on the length of fluoroscopy and procedure times during spine interventions.

DESIGN

Secondary analysis of 2 prospective observational studies.

SETTING

All injections were performed in an outpatient university setting.

PARTICIPANTS

A total of 209 patients in whom spine injections were performed (99 women), with a mean age of 54.6 years.

METHODS

The fluoroscopy times for 202 participants and total procedure times for 137 participants were recorded. Additional participant characteristics, including age, gender, BMI, and actual procedures performed, also were collected. Analysis of covariance and linear and nonlinear model analysis were performed to assess the effect of BMI on fluoroscopy and procedure times.

MAIN OUTCOME MEASUREMENTS

Fluoroscopy time and procedure duration times.

RESULTS

Participants had a mean age of 54.6 years, 51% were men, and 77% (n = 155) were overweight (BMI ≥25). Participants received the following interventions: 40 zygapophyseal joint injections, 33 medial branch nerve blocks, 113 transforaminal epidural injections, and 16 combined zygapophyseal joint injections and epidural injections. Gender, procedure number, and procedure type did not differ between groups. The overweight group demonstrated a 30% increase in mean fluoroscopy time and a 35% increase in mean procedure time. Controlling for other variables, we found that differences in fluoroscopy time and procedure time were significant (P = .032 and P = .031, respectively) between the 2 groups.

CONCLUSIONS

Significantly prolonged procedure time and fluoroscopy time in overweight patients increase the risks associated with spine interventions, not only to the patients but also to the operating room staff exposed to ionizing radiation.

The association of lumbar intervertebral disc degeneration on magnetic resonance imaging with body mass index in overweight and obese adults: a population-based study

OBJECTIVE

To investigate the association of being overweight or obese with the presence, extent, and severity of lumbar disc degeneration on magnetic resonance imaging (MRI) in adults.

METHODS

A population-based cross-sectional study of 2,599 southern Chinese volunteers was conducted. Subjects underwent radiographic and clinical assessment, and weight and height were measured. Sagittal T2-weighted MRIs of the lumbar spine were obtained. The presence, extent, and severity of disc degeneration and additional radiographic and clinical parameters were assessed. Asian-modified body mass index (BMI) (kg/m(2) ) categories were used. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

The study included 1,040 men and 1,559 women (mean age 41.9 years). Disc degeneration was noted in 1,890 subjects (72.7%). BMI was significantly higher in subjects with disc degeneration (mean 23.3 kg/m(2) ) than in subjects without degeneration (mean 21.7 kg/m(2) ) (P < 0.001). A significant increase in the number of degenerated levels (P < 0.001), global severity of disc degeneration (P < 0.001), and end-stage disc degeneration with disc space narrowing (P < 0.001) was noted with elevated BMI, in particular in overweight and obese subjects. In the adjusted multivariate logistic regression model, there was a positive linear trend (r(2) = 0.99) between BMI and the overall presence of disc degeneration in overweight (OR 1.30 [95% CI 1.03-1.62]) and obese (OR 1.79 [95% CI 1.17-2.74]) subjects. End-stage disc degeneration with disc space narrowing was significantly more pronounced in obese subjects (adjusted OR 1.72 [95% CI 1.23-2.41] [reference normal weight]).

CONCLUSION

Our findings, in one of the largest studies to systematically assess lumbar disc degeneration on MRI, indicated a significant association between the presence, extent, and global severity of disc degeneration with weight in overweight and obese adults.

Impact of obesity on orthopaedics

The prevalence of obesity among children and adults is increasing worldwide. There are substantial health risks and financial costs associated with the obesity epidemic that impact the practice of orthopaedic surgery. Patients with increased body mass index are more prone to sustaining distal extremity injuries than are those with a normal body mass index. Obese individuals are more likely than nonobese individuals to seek treatment for osteoarthritis of the knee.

Quantitative assessment of abdominal aortic calcification and associations with lumbar intervertebral disc height loss: the Framingham Study

BACKGROUND CONTEXT

Vascular disease has been proposed as a risk factor for disc height loss (DHL).

PURPOSE

To examine the relationship between quantitative measures of abdominal aortic calcifications (AACs) as a marker of vascular disease, and DHL, on computed tomography (CT).

STUDY DESIGN

Cross-sectional study in a community-based population.

PATIENT SAMPLE

Four hundred thirty-five participants from the Framingham Heart Study.

OUTCOME MEASURES

Quantitative AAC scores assessed by CT were grouped as tertiles of "no" (reference), "low," and "high" calcification. Disc height loss was evaluated on CT reformations using a four-grade scale. For analytic purposes, DHL was dichotomized as moderate DHL of at least one level at L2-S1 versus less than moderate or no DHL.

METHODS

We examined the association of AAC and DHL using logistic regression before and after adjusting for cardiovascular risk factors and before and after adjusting for age, sex, and body mass index (BMI).

RESULTS

In crude analyses, low AAC (odds ratio [OR], 2.05 [1.27-3.30]; p=.003) and high AAC (OR, 2.24 [1.38-3.62]; p=.001) were strongly associated with DHL, when compared with the reference group of no AAC. Diabetes, hypercholesterolemia, hypertension, and smoking were not associated with DHL and did not attenuate the observed relationship between AAC and DHL. Adjustment for age, sex, and BMI markedly attenuated the associations between DHL and low AAC (OR, 1.20 [0.69-2.09]; p=.51) and high AAC (OR, 0.74 [0.36-1.53]; p=.42).

CONCLUSIONS

Abdominal aortic calcification was associated with DHL in this community-based population. This relationship was independent of cardiovascular risk factors. However, the association of AAC with DHL was explained by the effects of age, sex, and BMI.

An educational approach based on a non-injury model compared with individual symptom-based physical training in chronic LBP. A pragmatic, randomised trial with a one-year follow-up

Background

In the treatment of chronic back pain, cognitive methods are attracting increased attention due to evidence of effectiveness similar to that of traditional therapies. The purpose of this study was to compare the effectiveness of performing a cognitive intervention based on a non-injury model with that of a symptom-based physical training method on the outcomes of low back pain (LBP), activity limitation, LBP attitudes (fear-avoidance beliefs and back beliefs), physical activity levels, sick leave, and quality of life, in chronic LBP patients.

Methods

The study was a pragmatic, single-blind, randomised, parallel-group trial. Patients with chronic/recurrent LBP were randomised to one of the following treatments: 1. Educational programme : the emphasis was on creating confidence that the back is strong, that loads normally do not cause any damage despite occasional temporary pain, that reducing the focus on the pain might facilitate more natural and less painful movements, and that it is beneficial to stay physically active. 2. Individual symptom-based physical training programme : directional-preference exercises for those centralising their pain with repetitive movements; 'stabilising exercises' for those deemed 'unstable' based on specific tests; or intensive dynamic exercises for the remaining patients. Follow-up questionnaires (examiner-blinded) were completed at 2, 6 and 12 months. The main statistical test was an ANCOVA adjusted for baseline values.

Results

A total of 207 patients participated with the median age of 39 years (IQR 33-47); 52% were female, 105 were randomised to the educational programme and 102 to the physical training programme. The two groups were comparable at baseline. For the primary outcome measures, there was a non-significant trend towards activity limitation being reduced mostly in the educational programme group, although of doubtful clinical relevance. Regarding secondary outcomes, improvement in fear-avoidance beliefs was also better in the educational programme group. All other variables were about equally influenced by the two treatments. The median number of treatment sessions was 3 for the educational programme group and 6 for the physical training programme group.

Conclusions

An educational approach to treatment for chronic LBP resulted in at least as good outcomes as a symptom-based physical training method, despite fewer treatment sessions.

Trial registration

Clinicaltrials.gov: # NCT00410319

Inciting events associated with lumbar disc herniation

BACKGROUND CONTEXT

No prior study has investigated the frequency of patient-identified inciting events in lumbar disc herniation (LDH) or their clinical significance.

PURPOSE

To examine the clinical frequency of patient-identified inciting events in LDH, and to identify associations between the presence of inciting events and the severity of the clinical presentation.

STUDY DESIGN/SETTING

Cross-sectional analysis of data from a cohort study with prospective recruitment, with retrospective data collection on inciting events. The setting was a hospital-based specialty spine clinic.

PATIENT SAMPLE

One hundred fifty-four adults with lumbosacral radicular pain and LDH confirmed by magnetic resonance imaging.

OUTCOME MEASURES

Self-report measures of disability measured by the Oswestry Disability Index (ODI), the visual analog scale (VAS) for leg pain, and the VAS for back pain.

METHODS

Dependent variables included the presence of a patient-identified inciting event, which were categorized as spontaneous onset, nonlifting physical activity, heavy lifting (>35 lbs), light lifting (<35 lbs), nonexertional occurrence, or physical trauma. We examined the association of an inciting event, or a lifting-related event, with each outcome, first using univariate analyses, and second using multivariate modeling, accounting for important adjustment variables.

RESULTS

Sixty-two percent of LDH did not have a specific patient-identified event associated with onset of symptoms. Nonlifting activities were the most common inciting event, comprising 26% of all LDH. Heavy lifting (6.5%), light lifting (2%), nonexertional occurrences (2%), and physical trauma (1.3%) accounted for relatively small proportions of all LDH. Patient-identified inciting events were not significantly associated with a more severe clinical presentation in crude analyses. Spontaneous LDH was significantly associated with higher baseline ODI scores in multivariate analysis, although the magnitude of this effect was small. There were no significant associations (p< or =.05) between the presence of a lifting-associated event and the outcomes of ODI, VAS leg pain, or VAS back pain.

CONCLUSIONS

The majority of LDH occurred without specific inciting events. A history of an inciting event was not significantly associated with a more severe clinical presentation. There was no significant association between the occurrence of a lifting-related event and the severity of the clinical presentation. This information may be useful in the counseling of patients recovering from acute LDH.