Preliminary validation of a self-reported screening questionnaire for inflammatory back pain

OBJECTIVE

Inflammatory back pain (IBP) is an important feature of axial spondyloarthritis (SpA) that is poorly recognized in primary care, perhaps delaying diagnosis of SpA. We aimed to develop and validate a self-report questionnaire using important domains reported by patients with IBP.

METHODS

We developed a 6-item questionnaire assessing spinal/hip stiffness, nocturnal pain, diurnal variation, effects of exercise/rest, and peripheral joint pain/swelling. This was compared with the Calin questionnaire and the domains comprising the Assessment of Spondyloarthritis International Society (ASAS) criteria for IBP in 220 patients with established axial SpA and 66 patients with mechanical back pain followed in tertiary care rheumatology clinics. The classification utility of each item was evaluated using sensitivity, specificity, and likelihood ratio (LR). Multivariable logistic regression was used to analyze different combinations of items to develop candidate scoring systems.

RESULTS

The single item "diurnal variation" had the highest combination of sensitivity (49%) and specificity (92%) for IBP (positive LR 5.95, 95% CI 2.54-13.94), outperforming the Calin and ASAS IBP criteria, which had sensitivities of 83% and 59%, specificities 42% and 66%, positive LR 1.42 and 1.72, negative LR 0.41 and 0.62, respectively. Classification utility of this item was even higher in SpA patients with disease duration < 6 years (sensitivity 48%, specificity 96%, positive LR 12, negative LR 0.54). The other 5 items did not improve classification utility in any combination.

CONCLUSION

Assessment of a single self-reported item, "diurnal variation," had substantial classification utility for IBP. This domain is not addressed in existing criteria for IBP, indicating a potentially important omission.

Visual and quantitative assessment of lateral lumbar spinal canal stenosis with magnetic resonance imaging

BACKGROUND

Lateral lumbar spinal canal stenosis is a common etiology of lumbar radicular symptoms. Quantitative measurements have commonly demonstrated better repeatability than visual assessments. We are not aware of any studies examining the repeatability of quantitative assessment of the lateral canal.

PURPOSE

To evaluate the repeatability of visual assessments and newly developed quantitative measurements of lateral lumbar spinal canal stenosis using magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Twenty-eight patients with lateral lumbar spinal canal stenosis or prior spinal surgery with recurrent symptoms were imaged with MRI. A radiologist, a neurosurgeon and a spine research trainee graded visually and quantitatively subarticular (n = 188) and foraminal zones (n = 260) of the lateral spinal canal. Quantitative measurements included the minimal subarticular width and the cross-sectional area of the foramen.

RESULTS

The repeatability of visual assessment at the subarticular zone and foraminal zones between raters varied from 0.45-0.59 and 0.42-0.53, respectively. Similarly, the intraclass correlation coefficients for the quantitative measurements varied from 0.67-0.71 and 0.66-0.76, respectively. The intra-rater repeatability for the visual assessments of the subarticular and foraminal zones was 0.70 and 0.62, respectively, while the corresponding intraclass correlation coefficients for quantitative measurements were 0.83 and 0.81, respectively.

CONCLUSION

Inter-rater repeatability of visual assessments of lateral stenosis is moderate, whereas quantitative measurements of both subarticular width and the cross-sectional area of the foramen have substantial reproducibility and may be particularly useful for longitudinal studies and research purposes. The clinical value of these parameters requires further study.

Is greater lumbar vertebral BMD associated with more disk degeneration? A study using µCT and discography

It is well documented that osteoarthritis is associated with greater BMD in peripheral extremities. Yet the relationship between vertebral BMD and disk degeneration (DD) remains controversial in the lumbar spine, which may be due largely to the inadequacies of BMD and DD measures. Aiming to clarify the association between vertebral BMD and adjacent DD, we studied 137 cadaveric lumbar vertebrae and 209 corresponding intervertebral disks from the spines of 48 white men aged 21 to 64 years. DD was evaluated using discography. The vertebrae were scanned using a micro-computed tomography (µCT) system to obtain volumetric BMD for the whole vertebra, the vertebral body, the vertebral body excluding osteophytes, and the vertebral body excluding osteophytes and endplates. A random effects model was used to examine the association between the different definitions of vertebral BMD and adjacent DD. No significant association was found between the BMD of the whole vertebra and adjacent DD. However, when the posterior elements were excluded, there was a significant association between greater vertebral body BMD and more severe degeneration in the disk cranial to the vertebra. This association remained after further excluding osteophytes and endplates from the vertebral body BMD measurements. Also, a trend of greater BMD of the vertebral body associated with more adjacent DD was evident. These results clarify the association between vertebral BMD and DD and specifically indicate that it is higher BMD of the vertebral body, not the entire vertebra, that is associated with more severe adjacent DD. This association may be obscured by the posterior elements and is not confounded by osteophytes and endplate sclerosis.

The osseous endplates in lumbar vertebrae: thickness, bone mineral density and their associations with age and disk degeneration

INTRODUCTION

As the gateway of nutrient supply, the vertebral endplate is essential to maintain the integrity and function of the avascular intervertebral disk. While a link between calcium deposition in the endplate and disk degeneration is well established from histological studies, findings on the association between endplate thickness and age and disk degeneration are conflicting. Moreover, the association between endplate bone mineral density (BMD) and disk degeneration remains unexplored in humans.

OBJECTIVES

To determine the thickness and BMD of lumbar spine osseous endplates in men and explore their associations with age and disk degeneration.

METHODS

From a spine archive, 150 cadaveric lumbar vertebrae (L1-L5) from 48 male human spines (mean age 50 years, range 21-64) were scanned using micro-CT (μCT). The osseous endplates were extracted from the vertebral body to measure the mean thickness and volumetric BMD. The difference between cranial and caudal endplates, associations of endplate thickness and BMD with age and discographic degeneration pathology were examined.

RESULTS

Overall, the mean thickness was 1.03±0.24 mm for cranial (to disk) endplates and 0.78±0.16 mm for caudal endplates. For lumbar intervertebral disks, the cranial endplate was significantly thicker and denser than the caudal endplate (p<0.001-0.05). Thickness and BMD of endplates were independent of age. Based on discography, a trend of more severe disk degeneration associated with greater thickness in both the cranial and caudal endplates was observed, and was most marked in severely degenerated disks (p<0.05). However, no evidence was detected for a link between more severe disk degeneration and elevated endplate BMD (p>0.05).

CONCLUSIONS

In the lumbar spine, both the thickness and BMD of endplates were independent of age, which ranged from 21 to 64 years. The endplates cranial to intervertebral disks were thicker and had higher BMD than the corresponding caudal endplates. Judged from discography, more degeneration in the adjacent intervertebral disk was associated with greater endplate thickness, but not higher endplate BMD. Thus, endplate sclerosis, reflecting elevated endplate BMD, may not be a risk factor for disk pathology in men.

Candidate gene association study of magnetic resonance imaging-based hip osteoarthritis (OA): evidence for COL9A2 gene as a common predisposing factor for hip OA and lumbar disc degeneration

OBJECTIVE

To study whether gene variants associated with lumbar disc degeneration (LDD) phenotypes are also associated with hip osteoarthritis (OA).

METHODS

Magnetic resonance imaging (MRI)-based hip OA changes for 345 twins were assessed and 99 single-nucleotide polymorphisms (SNP) were analyzed.

RESULTS

Variants in the COL9A2 (rs7533552, p = 0.0025) and COL10A1 (rs568725, p = 0.002) genes showed association with hip OA.

CONCLUSION

The associating G allele in COL9A2 changes a glutamine to arginine or to tryptophan and may predispose to both hip OA and LDD, making it a candidate for degenerative connective tissue diseases.

A short-form functional capacity evaluation predicts time to recovery but not sustained return-to-work

OBJECTIVES

To evaluate the ability of a short-form FCE to predict future timely and sustained return-to-work.

METHODS

A prospective cohort study was conducted using data collected during a cluster RCT. Subject performance on the items in the short-form FCE was compared to administrative recovery outcomes from a workers' compensation database. Outcomes included days to claim closure, days to time loss benefit suspension and future recurrence (defined as re-opening a closed claim, restarting benefits, or filing a new claim for injury to the same body region). Analysis included multivariable Cox and logistic regression using a risk factor modeling strategy. Potential confounders included age, sex, injury duration, and job attachment status, among others.

RESULTS

The sample included 147 compensation claimants with a variety of musculoskeletal injuries. Subjects who demonstrated job demand levels on all FCE items were more likely to have their claims closed (adjusted Hazard Ratio 5.52 (95% Confidence Interval 3.42-8.89), and benefits suspended (adjusted Hazard Ratio 5.45 (95% Confidence Interval 2.73-10.85) over the follow-up year. The proportion of variance explained by the FCE ranged from 18 to 27%. FCE performance was not significantly associated with future recurrence.

CONCLUSION

A short-form FCE appears to provide useful information for predicting time to recovery as measured through administrative outcomes, but not injury recurrence. The short-form FCE may be an efficient option for clinicians using FCE in the management of injured workers.

Do clinicians working within the same context make consistent return-to-work recommendations?

INTRODUCTION

Healthcare providers play important roles in the process of making return-to-work (RTW) recommendations, which have important consequences for injured workers and their employers. We studied the inter-rater reliability of RTW determinations between clinicians in a specific workers' compensation setting.

METHODS

Three case scenarios were given to clinicians working at one rehabilitation facility to examine consistency between clinicians in RTW recommendations. Additionally, we examined what information clinicians relied on to make decisions. Analysis included percentage agreement and other descriptive statistics.

RESULTS

Thirty-six clinicians (13 physiotherapists, 10 occupational therapists, 8 exercise therapists, and 5 physicians) responded to the questionnaire. Subjects showed a high percentage agreement regarding RTW readiness on fracture and dislocation scenarios (97.2 and 94.4%, respectively), while agreement on a back pain scenario was modest (55.6%). In all cases, more than 50% of clinicians relied on biomedical information, such as physical examination.

CONCLUSIONS

Clinicians demonstrated a high level of agreement (>94%) when making RTW recommendations for injuries with clear pathology. However, a lower level of agreement (56%) was observed for back pain where the etiology of pain and disability is often more complex. Clinicians most commonly recommended RTW with restrictions, underlining the importance of workplace accommodations and modified duties in facilitating resumption of work.

Physical therapy treatment options for lumbar spinal stenosis

BACKGROUND

Given the dearth of high quality research on conservative treatment for spinal stenosis, an empirical understanding of the scope of physical therapy provided in the community can help focus research and build standards of care.

OBJECTIVES

Provide preliminary insight into current physical therapy practice in the treatment of lumbar spinal stenosis (LSS), from both patient and physical therapist perspectives.

METHODS

Patients greater than 50 years of age with LSS diagnosed by a spine surgeon were recruited to participate in a telephone survey regarding treatment. Physical therapists were recruited to complete a survey regarding treatments offered to patients with LSS.

RESULTS

Of the patients participating in the study (n=75), 44 (59%) reported receiving physical therapy treatment. Treatments most frequently reported by patients were massage (27%), strengthening exercises (23%), flexibility exercises (18%), and heat/ice (14%). The most frequently advocated treatments by the 76 physical therapists included flexibility (87%), stabilization (86%) and strengthening exercises (83%), followed by heat/ice (76%), acupuncture (63%) and joint mobilization (62%).

CONCLUSIONS

These results can guide both clinical research priorities and standards of care for physical therapy treatments of LSS. Based on the results of this study, future research foci should include massage, flexibility and strengthening exercises, stabilization techniques and heat/ice treatments.

Allelic variants of IL1R1 gene associate with severe hand osteoarthritis

Background

In search for genes predisposing to osteoarthritis (OA), several genome wide scans have provided evidence for linkage on 2q. In this study we targeted a 470 kb region on 2q11.2 presenting the locus with most evidence for linkage to severe OA of distal interphalangeal joints (DIP) in our genome wide scan families.

Methods

We genotyped 32 single nucleotide polymorphisms (SNPs) in this 470 kb region comprising six genes belonging to the interleukin 1 superfamily and monitored for association with individual SNPs and SNP haplotypes among severe familial hand OA cases (material extended from our previous linkage study; n = 134), unrelated end-stage bilateral primary knee OA cases (n = 113), and population based controls (n = 436).

Results

Four SNPs in the IL1R1 gene, mapping to a 125 kb LD block, provided evidence for association with hand OA in family-based and case-control analysis, the strongest association being with SNP rs2287047 (p-value = 0.0009).

Conclusions

This study demonstrates an association between severe hand OA and IL1R1 gene. This gene represents a highly relevant biological candidate since it encodes protein that is a known modulator of inflammatory processes associated with joint destruction and resides within a locus providing consistent evidence for linkage to hand OA. As the observed association did not fully explain the linkage obtained in the previous study, it is plausible that also other variants in this genome region predispose to hand OA.

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

BACKGROUND CONTEXT

There are differing views as to the causes of disc degeneration. One view, referred to as a cumulative or repetitive injury model, explains disc degeneration, in great part, as the result of "wear and tear" on the disc from routine daily exposures to physical loading or biomechanical forces. Perhaps paradoxically, such physical loading has been thought to be generally beneficial for other structures of the musculoskeletal system.

PURPOSE

The goal of this study was to investigate the associations of physical loading from body weight using quantitative measures of disc degeneration.

STUDY DESIGN

This is an exposure-discordant twin study.

METHODS

We selected 44 pairs of healthy male monozygotic (MZ) twins with 8 kg or more discordance in body weight (mean 13 kg), with lumbar magnetic resonance imaging and bone density measurements available. The main outcome of disc degeneration was assessed through quantitatively measured disc height, and disc signal intensity and signal variation adjusted by the intrabody reference, adjacent cerebrospinal fluid signal, at L1-L4. Data on suspected constitutional and environmental risk factors were available for control of possible confounding factors.

RESULTS

Higher body weight was associated with 6.2% higher bone density in the lumbar spine, confirming an effective discordance (p<.0001). Disc signal variation was 5.4% higher ("better") among the heavier MZ co-twins (p=.005), but the 2.6% higher disc heights and 2.9% higher adjusted disc signals were not statistically significant.

CONCLUSIONS

Contrary to common beliefs, our findings suggest that cumulative or repetitive loading because of higher body mass (nearly 30 pounds on average) was not harmful to the discs. In fact, a slight delay in L1-L4 disc desiccation was observed in the heavier men, as compared with their lighter twin brothers.

Material handling performance of patients with chronic low back pain during Functional Capacity Evaluation: A comparison between three countries

PURPOSE

Functional Capacity Evaluations (FCEs) are batteries of tests designed to measure patients' ability to perform work-related activities. Although FCEs are used worldwide, it is unknown how patients' performances compare between countries or settings. This study was performed to explore similarities and differences in FCE performance of patients with chronic low back pain (CLBP) between three international settings that utilize the same FCE protocol.

METHODS

Standardized FCEs were performed on three cohorts of patients with CLBP: A sample from an outpatient rehabilitation context in The Netherlands (n = 121), a Canadian sample in a Worker's Compensation context (n = 273), and a Swiss sample in an inpatient rehabilitation context (n = 170). Patients were undergoing FCE as part of their usual clinical care. Means and standard deviations of maximum performance on the FCE material handling items were calculated and differences compared using ANOVA. Multivariable linear regression was used to determine the relationship between country of origin and FCE performance while controlling for potential confounders including, age, sex, duration of back pain problems, and self-reported pain and disability ratings.

RESULTS

Compared to the Dutch sample, the mean performance of patients in the Canadian and Swiss samples was consistently lower on all FCE items. This association remained statistically significant after controlling for potential confounders.

CONCLUSIONS

Considerable differences were observed between settings in maximum weight handled on the various FCE items. Future FCE research should examine the effects of a number of potentially influential factors, including variability in evaluator judgements across settings, the evaluator-patient interaction and patients' expectations of the influence of FCE results on disability compensation.

Associations of 25 structural, degradative, and inflammatory candidate genes with lumbar disc desiccation, bulging, and height narrowing

OBJECTIVE

To examine the allelic diversity of structural, inflammatory, and matrix-modifying gene candidates and their association with disc degeneration.

METHODS

Subjects were 588 men ages 35-70 years. We investigated associations of single-nucleotide polymorphisms in AGC1 and in 12 collagen, 8 interleukin, and 4 matrix metalloproteinase genes with quantitative magnetic resonance imaging measurements of disc desiccation and disc bulging and height narrowing scores, after controlling for age and suspected risk factors. Analyses were performed using QTDT software. P values were derived from 1,000 permutations, and empirical P values for global significance also were applied.

RESULTS

Twelve of the 99 variants in 25 selected candidate genes provided evidence of association (P < 0.05) with disc signal intensity in the upper and/or lower lumbar regions. Allelic variants of AGC1 (rs1042631; P = 0.001), COL1A1 (rs2075555; P = 0.005), COL9A1 (rs696990; P = 0.00008), and COL11A2 (rs2076311; P = 0.018) genes provided the most significant evidence of association with disc signal intensity. The same variants of AGC1 (P = 0.010) and COL9A1 (P = 0.014), as well as variants in the COL11A1 gene (rs1463035 [P = 0.004]; rs1337185 [P = 0.015]) were also associated with disc bulging, as was AGC1 with disc height narrowing (rs1516797; P = 0.005). In addition, 4 allelic variants in the immunologic candidate genes (rs2071375 in IL1A [P = 0.027]; rs1420100 in IL18RAP [P = 0.005]) were associated with disc signal intensity.

CONCLUSION

Genetic variants account for interindividual differences in disc matrix synthesis and degradation. The accuracy of the quantitative disc signal intensity measurements we used likely enhanced our ability to observe these associations. Our findings shed light on possible mechanisms of degeneration and support the view that disc degeneration is a polygenetic condition.

The Twin Spine Study: contributions to a changing view of disc degeneration

BACKGROUND CONTEXT

Disc degeneration was commonly viewed over much of the last century as a result of aging and "wear and tear" from mechanical insults and injuries. Thus, prevention strategies and research in lumbar degenerative changes and associated clinical conditions focused largely on mechanical factors as primary causes using an "injury model." The Twin Spine Study, a research program on the etiology and pathogenesis of disc degeneration, has contributed to a substantial revision of this view of determinants of lumbar disc degeneration.

PURPOSE

To provide a review of the methods and findings of the Twin Spine Study project.

STUDY DESIGN/SETTING

Narrative review of the Twin Spine Study.

METHODS

The Twin Spine Study, which started in 1991, is a multidisciplinary, multinational research project with collaborators primarily in Canada, Finland, and the United States. The most significant investigations related to determinants of disc degeneration included occupational exposures, driving and whole-body vibration exposure, smoking exposure, anthropomorphic factors, heritability, and the identification of genotypes associated with disc degeneration.

RESULTS

Among the most significant findings were a substantial influence of heredity on lumbar disc degeneration and the identification of the first gene forms associated with disc degeneration. Conversely, despite extraordinary discordance between twin siblings in occupational and leisure-time physical loading conditions throughout adulthood, surprisingly little effect on disc degeneration was observed. Studies on the effects of smoking on twins with large discordance in smoking exposure demonstrated an increase in disc degeneration associated with smoking, but this effect was small. No evidence was found to suggest that exposure to whole-body vibration through motorized vehicles leads to accelerated disc degeneration in these well-controlled studies. More recent results indicate that the effect of anthropometric factors, such as body weight and muscle strength on disc degeneration, although modest, appear in this work to be greater than those of occupational physical demands. In fact, some indications were found that routine loading may actually have some benefits to the disc.

CONCLUSIONS

The once commonly held view that disc degeneration is primarily a result of aging and "wear and tear" from mechanical insults and injuries was not supported by this series of studies. Instead, disc degeneration appears to be determined in great part by genetic influences. Although environmental factors also play a role, it is not primarily through routine physical loading exposures (eg, heavy vs. light physical demands) as once suspected.

Genetic and environmental effects on disc degeneration by phenotype and spinal level: a multivariate twin study

STUDY DESIGN

A classic twin study with multivariate analyses was conducted.

OBJECTIVE

We aimed to further clarify the presence and magnitude of genetic influences on disc degeneration, and to better understand the phenomenon of disc degeneration through comparisons of genetic and environmental influences on specific degenerative signs and different lumbar levels.

SUMMARY OF BACKGROUND DATA

Previous studies suggest a substantial genetic influence on disc degeneration, but raise important questions about which disc phenotypes are or are not largely genetically influenced and differential effects on spinal levels.

METHODS

The study sample consisted of 152 monozygotic and 148 dizygotic male twin pairs, 35 to 70 years of age, from the population-based Finnish Twin Cohort. Lumbar magnetic resonance imaging was conducted with quantitative or qualitative assessments of disc signal, bulging, and height narrowing at each lumbar level. Data on possible confounding factors were obtained from an extensive, structured interview. Quantitative genetic modeling was conducted using MPlus.

RESULTS

Heritability estimates varied from 29% to 54%, depending on the particular disc degeneration phenotype and lumbar level. The same genetic influences affected signal intensity and disc height (genetic correlations of -0.60- -0.66) or bulging (-0.71- -0.72) to a great degree at either the lower or upper lumbar levels and genetic influences on disc height narrowing and bulging were virtually the same. (0.92-0.97). Conversely, genetic correlations (and environmental correlations)were substantially lower for upper and lower lumbar levels, implying largely independent effects.

CONCLUSION

Genetic and environmental influences on disc degeneration seem to be of similar importance. Disc signal, narrowing, and bulging had a primarily common genetic pathway, suggesting a common genetic etiopathogenesis. Conversely, genetic and environmental influences differed substantially for upper versus lower lumbar levels, emphasizing the importance of examining these levels separately in studies of associated genes, other constitutional factors, and environmental influences.

The reliability of paraspinal muscles composition measurements using routine spine MRI and their association with back function

This study examines the reliability of quantitative and qualitative muscle composition measurements of paraspinal muscle cross-sectional areas (CSAs) from routine lumbar spine magnetic resonance images and their association with maximal isokinetic lifting performance. The extent of paraspinal muscle composition reflects back function is currently not known. Measurements were repeated 4-8 weeks apart and different measurements of related constructs were compared. Participants were a population-based sample of 169 males, 35-67 years old, without considering the presence or absence of a history of low back pain or related problems in the selection of subjects. The quantitative and qualitative muscle composition measurements for axial magnetic resonance (MR) images of paraspinal muscles at the L3-L4 lumbar spine level, isokinetic lifting force and work, and body fat percentage were the main outcome measures. Results showed that the reproducibility of different paraspinal muscle composition measurements at the L3-L4 level was excellent for CSAs (ICC=0.95-0.99) and quantitative muscle composition measurements using cerebrospinal fluid adjusted signal intensity (ICC=0.96-0.99), and moderate for qualitative muscle composition ratings (Kappa=0.54-0.76). The correlations of the quantitative and qualitative muscle composition measurements with isokinetic lifting force and work were generally low (r=0.02-0.41), and favoured the qualitative assessments. In conclusion, quantitative and qualitative muscle composition measurements of paraspinal muscles are highly reproducible tissue measures, have low associations with body fat and isokinetic lifting performance, and show that paraspinal muscle morphology using routine spine magnetic resonance imaging (MRI) is poorly related to back function.

Heritability of lumbar flexibility and the role of disc degeneration and body weight

Spinal range of motion is evaluated in assessing patients with back problems and monitoring outcomes, as well as in general fitness assessments. Yet, determinants of the substantial interindividual variation in spinal range of motion are not well understood. Substantial genetic effects on global measures of range of motion and hypermobility have been suggested from earlier studies, but genetic influences specifically on spinal range of motion have not been previously studied. The objectives of the present study were to investigate the relative role of genetic and environmental influences on lumbar range of motion in adult men and the pathways through which genes may influence range of motion. Thus we conducted a classic twin study of 300 monozygotic and dizygotic male twin pairs with consideration of covariates, using standard statistical methods. All subjects underwent a clinical examination, including general anthropometrics, lumbar range of motion, and lumbar MRI to assess disc degeneration, as well as an extensive interview on environmental and behavioral exposures and back pain history. We found the proportion of variance in lumbar range of motion attributable to genetic influences (heritability estimate) to be 47%. The extent of lumbar range of motion in flexion was predominantly determined by genetic influences (64%), while extension was influenced to a somewhat greater degree by environmental and behavioral factors. Statistically significant age-adjusted genetic correlations were found between lumbar extension and disc degeneration variables ( ra= −0.38 to −0.43) and between flexion and body weight ( ra= −0.33), suggesting two pathways through which genes influence lumbar range of motion.

Determinants of changes in bone density: a 5-year follow-up study of adult male monozygotic twins

The relative importance of determinants in bone mineral density (BMD) in adult men is partly unclear. Our goals were to investigate the effects of familial aggregation and behavioral factors on the change in BMD during a 5-yr follow-up. Subjects (n=140) were 70 exposure-discordant monozygotic twin pairs (age 35-69 yr). BMD was measured with the same dual-energy X-ray absorptiometry scanner at baseline and at the 5-yr follow-up. A variety of covariates were used including physical examination and interview data. Multivariate linear regression was used. The mean annual decrease in femoral BMD was 0.2%. The mean lumbar BMD was unchanged, although 8-17% of subjects had a decrease of more than 5%. Familial aggregation explained 14% of the changes in femoral BMD and 19% in lumbar BMD. The stability of BMD in the follow-up was high, both for individuals (intraclass correlation coefficient [ICC]=0.90-0.94) and for co-twins in a pair (ICC=0.77-0.84). In femoral BMD, use of alcohol (p=0.006), coffee (p=0.046), and beta-blockers (p=0.043) led to increases, whereas smoking led to a decrease (p<0.01). We concluded that frequent increases in BMD, influenced by beta-blockers, partly explain the minor mean changes during follow-up; however, about every 10th subject had a significant decrease. Overall, familial effects played a dominant role in BMD changes in adult men.

Heritability of BMD of femoral neck and lumbar spine: a multivariate twin study of Finnish men

Of the 80% variation in BMD among male twins that is caused by genetics, part was explained by genetic influences on lifting strength and lean body mass/height. Lifting strength was significant in both the femoral and spine BMD and body weight only for lumbar BMD.

INTRODUCTION

The dominant role of heritability in BMD has been shown in twin studies among women. However, the mechanisms of genetic influences are poorly understood. BMD is associated with lean body mass and muscle strength, which both have a genetic component, but the relative effects of muscle strength and lean body mass/height on the total genetic and environmental variations influencing BMD of men are unclear.

MATERIALS AND METHODS

Measurements of BMD from a DXA scanner on a representative sample of 147 monozygotic and 153 dizygotic male twin pairs (age, 35-70 yr) were related to a variety of anthropometric and behavioral covariates and interview data. Data were analyzed with univariate modeling of genetic characteristics, bivariate modeling of covariates that were significant in univariate models, and multivariate modeling of the simultaneous effects of significant covariates from the bivariate models.

RESULTS

Heritability influences were estimated to account for 75% of the variance in femoral BMD and 83% in lumbar BMD. Univariate and bivariate modeling showed that, of the factors studied, only lifting force and lean body mass/height had statistically significant influences. Of the total genetic variation in femoral BMD, lifting force explained 9%, and lean body mass/height 18%; the proportions for lumbar BMD were 9% and 11%, respectively. Of the total environmental variation, the correlation with isokinetic lifting force explained 9% for femoral BMD and 10% for lumbar BMD. The genetic correlations between lifting force and femoral and lumbar BMD were approximately 0.3, as were the environmental correlations of isokinetic lifting force and femoral and lumbar BMD and of lean body mass/height and femoral BMD. The environmental correlation of lean body mass/height and femoral BMD was not significant.

CONCLUSIONS

Lifting force had effects on both femoral and lumbar BMD. Body weight was important, but only for lumbar BMD. Muscle strength may have the best potential for modification among behavioral factors to increase both femoral and lumbar BMD.

Evaluation of a short-form functional capacity evaluation: less may be best

PURPOSE

Functional Capacity Evaluation (FCE) contributes to clinical decisions regarding fitness-for-work and may improve return-to-work outcomes. However, FCE is a burdensome clinical tool in terms of time and cost. We evaluated the effectiveness of a short-form FCE protocol.

METHODS

A cluster randomized controlled trial was conducted. Data were collected on all claimants undergoing FCE at Alberta's workers' compensation rehabilitation facility. Twenty-three clinicians who were trained and experienced with FCE were randomized to either an intervention or control group. The intervention group was trained to conduct short-form FCE and used this protocol through the trial's duration, while the control group continued standard FCE procedures. Data on subject characteristics, administrative outcomes (days to suspension of time loss benefits, days to claim closure, and future recurrence) and claimant satisfaction were extracted from the WCB-Alberta computer databases. Clinicians logged time taken to complete assessments. Analysis included examining differences between groups using independent samples t tests, Cox and logistic regression.

RESULTS

Subjects included 372 claimants of whom 173 were tested with short-form FCE. Subjects were predominantly employed (64%) males (69%) with chronic musculoskeletal conditions (median duration 252 days). Administrative recovery outcomes were similar between groups as were claimant satisfaction ratings. No statistically significant or clinically relevant differences were observed on these outcomes between groups. A 43% reduction in functional assessment time was seen.

CONCLUSION

A short-form FCE appears to reduce time of assessment while not affecting recovery outcomes when compared to standard FCE administration. Such a protocol may be an efficient option for therapists performing fitness-for-work assessments.

Role of genetic and environmental influences on heart rate variability in middle-aged men

Our aim was to estimate causal relationships of genetic factors and different specific environmental factors in determination of the level of cardiac autonomic modulation, i.e., heart rate variability (HRV), in healthy male twins and male twins with chronic diseases. The subjects were 208 monozygotic (MZ, 104 healthy) and 296 dizygotic (DZ, 173 healthy) male twins. A structured interview was used to obtain data on lifetime exposures of occupational loading, regularly performed leisure-time sport activities, coffee consumption, smoking history, and chronic diseases from 12 yr of age through the present. A 5-min ECG at supine rest was recorded for the HRV analyses. In univariate statistical analyses based on genetic models with additive genetic, dominance genetic, and unique environmental effects, genetic effects accounted for 31–57% of HRV variance. In multivariate statistical analysis, body mass index, percent body fat, coffee consumption, smoking, medication, and chronic diseases were associated with different HRV variables, accounting for 1–11% of their variance. Occupational physical loading and leisure-time sport activities did not account for variation in any HRV variable. However, in the subgroup analysis of healthy and diseased twins, occupational loading explained 4% of the variability in heart periods. Otherwise, the interaction between health status and genetic effects was significant for only two HRV variables. In conclusion, genetic factors accounted for a major portion of the interindividual differences in HRV, with no remarkable effect of health status. No single behavioral determinant appeared to have a major influence on HRV. The effects of medication and diseases may mask the minimal effect of occupational loading on HRV.

Construct validity of the physical function scale of the Swiss Spinal Stenosis Questionnaire for the measurement of walking capacity

STUDY DESIGN

Measurement (validity) study using data from a prospective longitudinal study of lumbar spinal stenosis.

OBJECTIVE

Provide convergent and divergent validity evidence for the use of the Physical Function Scale of the Swiss Spinal Stenosis Questionnaire for the measurement of walking capacity in persons with lumbar spinal stenosis. We were also interested in the association between the Physical Function Scale and the Oswestry Disability Index (ODI).

SUMMARY OF BACKGROUND DATA

The Physical Function Scale has been used to assess walking capacity in persons with lumbar spinal stenosis; however, there have been limited studies investigating its psychometric properties. No validity studies have compared the Physical Function Scale and the ODI head to head.

METHODS

The Physical Function Scale was correlated with the ODI, Health Utilities Index, Centres for Epidemiologic Studies Depression Scale, Medical Outcomes Survey Social Support Scale, and an additional item from the Oxford Claudication Score.

RESULTS

As hypothesized, the Physical Function Scale was correlated highly with those instruments and items intended to measure walking capacity and minimally with those instruments intended to measure different constructs. The correlation between the Physical Function Scale and the ODI was r = 0.719.

CONCLUSION

Results support construct validity of the Physical Function Scale for the measurement of walking in an lumbar spinal stenosis population. However, it cannot be ascertained from the current study that the construct being measured is, indeed, walking capacity. Further research is warranted to investigate criterion validity evidence for the use of the Physical Function Scale in the measurement of walking capacity in lumbar spinal stenosis, by examining the relationships between self-report and observational measures of walking.

The effects of anthropometrics, lifting strength, and physical activities in disc degeneration

STUDY DESIGN

A cross-sectional study design was used.

OBJECTIVE

The objective was to examine the influences of body anthropometrics, axial disc area, and lifting strength on disc degeneration and to compare these with the effects of lifetime physical demands and age.

SUMMARY OF BACKGROUND DATA

Although recent studies have shown that heredity is a dominant factor in disc degeneration, the common notion that occupational physical loading is the major risk factor persists. However, substantial variations in disc degeneration, particularly at the lowest lumbar levels, remain unexplained by heredity or occupational physical demands.

METHODS

Univariate methods and stepwise multiple regression modeling were used to estimate associations of body height, weight, fat content, axial disc area, isokinetic lifting performance, and lifetime routine physical activities at work and leisure with disc height narrowing and disc signal (in T2 images) based on lumbar MRIs. These data were available from a population sample of 600 men, 35 to 70 years of age.

RESULTS

Lower disc signal, representing disc desiccation, was associated with higher age, lower body mass and lifting strength, and larger axial disc area. Of the variance in disc signal, age explained 8.0% (P < 0.001) and body weight/axial disc area, isokinetic lifting strength, and occupational lifting history added 3.9%, 2.3%, and 1.3%, respectively. Greater disc narrowing was associated with higher age, larger axial disc area, and higher occupational physical loading. Of the variance in disc narrowing, age accounted for 3.8% (P < 0.001); axial disc area and occupational loading added 1.9% (P < 0.004) and 1.3% (P < 0.007), respectively.

CONCLUSIONS

Body weight, lifting strength, and axial disc area were more highly associated with disc degeneration than occupational and leisure physical activity histories, although all had modest influences. Furthermore, higher body mass, greater lifting strength, and heavier work were all associated with more disc height narrowing but less disc desiccation contrary to current views. Smaller discs appeared to have beneficial effects.

Heritability of low back pain and the role of disc degeneration

Twin studies suggest that both disc degeneration and back pain have a genetic component. We were interested in estimating the heritability of low back pain in men and examining whether genetic influences on back pain are mediated through genetic influences on disc degeneration. Thus, we conducted a classic twin study with multivariate quantitative genetic models to estimate the degree to which genetic (or environmental) effects on back pain were correlated with genetic (or environmental) effects on disc degeneration. Subjects included 147 monozygotic and 153 dizygotic male twin pairs (N=600 subjects) from the population-based Finnish Twin Cohort. All subjects underwent lumbar magnetic resonance imaging and completed an extensive interview, including back pain history and exposure to suspected risk factors. Disc height narrowing was the degenerative finding most associated with pain history, and was used to index disc degeneration in the models. Statistically significant genetic correlations were found for disc height narrowing and different definitions of back pain, such as duration of the worst back pain episode (r(g)=0.46) and hospitalization for back problems (r(g)=0.49), as well as disability in the previous year from back pain (r(g)=0.33). The heritability estimates for these back pain variables ranged from 30% to 46%. There also were statistically significant, but weaker, environmental correlations for disc height narrowing with back symptoms over the prior year. A substantial minority of the genetic influences on pain was due to the same genetic influences affecting disc degeneration. This suggests that disc degeneration is one pathway through which genes influence back pain.

The influence of magnetic resonance imaging findings of degenerative disease on dual-energy X-ray absorptiometry measurements in middle-aged men

PURPOSE

To examine degenerative features based on magnetic resonance imaging (MRI) measurements at the lumbar spine in relation to dual-energy X-ray absorptiometry (DXA), and to investigate whether bone mineral density (BMD) is reflected in the substitution of bone trabecular structure by fat at the vertebral body level indicated by MRI T1 relaxation time, endplate concavity, and hypertrophic (osteophytes and endplate sclerosis) MRI findings.

MATERIAL AND METHODS

The sample for this cross-sectional study was composed of 102 subjects, 35-70 years old, from a population-based cohort. Data collection included DXA in the anterior-posterior projection at the L1-L4 vertebrae and right femoral neck, and MRI of the lumbar spine in the midsagittal plane.

RESULTS

Age, vertebral signal intensity, osteophytes, and endplate concavity collectively explained 20% of the variance in spine BMD.

CONCLUSION

The study findings suggest that degenerative findings based on MRI measurements at the lumbar spine have an influence on bone assessment using DXA. Therefore, an overall bone assessment such as DXA might not offer an accurate measure of BMD.