Daily spinal mechanical loading as a risk factor for acute non-specific low back pain: a case-control study using the 24-Hour Schedule

Do patients with acute low back pain in emergency departments have more severe symptoms than those in general practice? A systematic review with meta-analysis

INTRODUCTION

There is a common belief that patients presenting to emergency departments have more severe pain levels and functional limitations than those in general practice. The aim of this systematic review was to compare pain and disability levels of patients with acute low back pain presenting to general practice versus those presenting to emergency departments.

METHODS

Electronic searches were conducted in MEDLINE, EMBASE and CINAHL from inception to February 2019. Observational studies including patients with acute non-specific low back pain presenting to emergency departments and/or general practice were eligible. Pain and/or disability scores expressed on a 0-100 scale were the primary outcomes. Risk of bias was evaluated using a validated tool for observational studies and the overall quality of evidence was assessed using GRADE. Meta-analysis using random effects and meta-regression were used to test for differences between the two settings.

RESULTS

We included 12 records reporting results for 10 unique studies with a total of 6,999 participants from general practice (n = 6) and emergency departments (n = 4). There was low quality evidence (downgraded for indirectness and inconsistency) that patients presenting to emergency departments had higher pain scores than those in general practice with a mean difference of 17.3 points (95%CI: 8.8 to 25.9 on a 0-100 scale). Similarly, there was low quality evidence (downgraded for indirectness and inconsistency) that patients presenting to emergency departments had higher disability scores than those in general practice (mean difference: 21.7, 95%CI: 4.6 to 38.7 on a 0-100 scale).

CONCLUSION

Patients with acute non-specific low back pain presenting to emergency departments may report higher levels of pain and disability than those seen in general practice.

PROSPERO REGISTRATION NUMBER

CRD42017076806.

Direct and Intervertebral Disc-Mediated Sensitization of Dorsal Root Ganglion Neurons by Hypoxia and Low pH

Objective

Ischemia-related risk factors are consistently correlated with discogenic pain, but it remains unclear how the ischemia-associated hypoxia and acidosis influence the peripheral sensory nervous system, namely the dorsal root ganglion (DRG), either directly or indirectly via intervertebral disc (IVD) mediation.

Methods

Bovine tail IVD organ cultures were preconditioned in different hypoxic and/or acidic conditions for 3 days to collect the conditioned medium (CM). The DRG-derived ND7/23 cells were either treated by the IVD CM or directly stimulated by hypoxic and/or acidic conditions. Neuronal sensitization was evaluated using calcium imaging (Fluo-4) after 3 days.

Results

We found that direct exposure of DRG cell line to hypoxia and acidosis increased both spontaneous and bradykinin-stimulated calcium response compared to normoxia-neutral pH cultures. Hypoxia and low pH in combination showed stronger effect than either parameter on its own. Indirect exposure of DRG to hypoxia-acidosis-stressed IVD CM also increased spontaneous and bradykinin-stimulated response, but to a lower extent than direct exposure. The impact of direct hypoxia and acidosis on DRG was validated in a primary sheep DRG cell culture, showing the same trend.

Conclusion

Our data suggest that targeting hypoxia and acidosis stresses both in IVD and DRG could be a relevant objective in discogenic pain treatment.

Lumbar interspinous pressure pain threshold values for healthy young men and women and the effect of prolonged fully flexed lumbar sitting posture: An observational study

BACKGROUND

Low back pain (LBP) is a common condition with large burden worldwide. Exposure to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-reported LBP. No study has previously investigated whether exposure to prolonged flexed sitting posture provokes discomfort/pain and decreased interspinous pressure pain thresholds for healthy young men and women without back pain, despite this being a suggested risk factor for LBP.

AIM

To investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort and lowers interspinous pressure pain thresholds in the lumbar spine for healthy young men and women without previous LBP.

METHODS

This is a an observational before and after study of 26 participants (13 men, 13 women) between 20-35 years old. Algometry was used to examine the pain threshold for pressure applied between spinous processes of the lumbar spine L1-L5. Pressure algometer measures were performed in prone before and after participants were instructed to sit in a fully flexed posture for a maximum of 15 min or until discomfort was experienced in the low back (Borg CR10 = 7/10). Wilcoxon signed-rank test was used for analyze values from the before and after test conditions. Mann-Whitney U test was used to investigate potential gender difference.

RESULTS

Fully flexed lumbar spine sitting posture up to 15 min provoked temporary discomfort but the proportion of participants experiencing discomfort 7/10 in the low back was 62%. For all pain pressure threshold locations tested, there was a significant difference for the study population with moderate-large decreased (r = -0.56) pressure pain threshold after exposure to prolonged flexed sitting posture (P < 0.01). Comparisons between gender did not show any significant difference.

CONCLUSION

The result showed that exposure to fully flexed lumbar sitting posture for up to 15 min produced temporary discomfort in the low back in young healthy adults with no previous history of LBP and significantly reduced lumbar interspinous pressure pain thresholds. No gender-based differences were observed.

Effects of the weight configuration of hand load on trunk musculature during static weight holding

The performance of manual material handling tasks is one major cause of lower back injuries. In the current study, we investigated the influence of the weight configuration of hand loads on trunk muscle activities and the associated spinal stability. Thirteen volunteers each performed static weight-holding tasks using two different 9 kg weight bars (with medial and lateral weight configurations) at two levels of height (low and high) and one fixed horizontal distance (which resulted in constant spinal joint moment across conditions). Results of the current study demonstrated that holding the laterally distributed load significantly reduced activation levels of lumbar and abdominal muscles by 9-13% as compared with holding the medially distributed load. We believe such an effect is due to an elevated rotational moment of inertia when the weight of the load is laterally distributed. These findings suggest that during the design and assessment of manual material handling tasks, such as lifting and carrying, the weight configuration of the hand load should be considered. Practitioner summary: Elevated trunk muscle activities were found when holding a medially distributed load vs. a laterally distributed load (with an equivalent external moment to the spine), indicating a reduced spinal stability due to the reduced rotational moment of inertia. The configuration of the hand load should be considered when evaluating manual material handling tasks.

An EMG-assisted modeling approach to assess passive lumbar tissue loading in vivo during trunk bending

Lower back pain (LBP) is a condition with high prevalence and high cost both in the United States and around the world. The magnitude of mechanical loading on spine is strongly associated with the occurrence of LBP. Previously, to assess spinal loading, biologically assisted biomechanical models were developed to estimate trunk muscle contraction forces. Loadings on lumbar passive tissues are estimated using anatomical models. However, despite the substantial individual variability in lumbar ligament geometry and viscoelastic properties, the existing anatomical models do not account for these differences. As such, the accuracy of model prediction is compromised especially when mid to full range of trunk motions are involved. This paper describes a new modeling approach to assess lumbar passive tissue loading with the consideration of individual differences in lumbar passive tissue properties. A data set that has trunk bending data from 13 human participants was analyzed; on average, lumbar passive tissue contributes to ∼89% of the total spinal compression force at fully flexed trunk postures; the estimated spinal tissue loadings were in feasible ranges as reported from previous cadaver studies; the estimated spinal loadings were also mostly in agreement with results from previous in vivo studies.

Tissue loading created during spinal manipulation in comparison to loading created by passive spinal movements

Spinal manipulative therapy (SMT) creates health benefits for some while for others, no benefit or even adverse events. Understanding these differential responses is important to optimize patient care and safety. Toward this, characterizing how loads created by SMT relate to those created by typical motions is fundamental. Using robotic testing, it is now possible to make these comparisons to determine if SMT generates unique loading scenarios. In 12 porcine cadavers, SMT and passive motions were applied to the L3/L4 segment and the resulting kinematics tracked. The L3/L4 segment was removed, mounted in a parallel robot and kinematics of SMT and passive movements replayed robotically. The resulting forces experienced by L3/L4 were collected. Overall, SMT created both significantly greater and smaller loads compared to passive motions, with SMT generating greater anterioposterior peak force (the direction of force application) compared to all passive motions. In some comparisons, SMT did not create significantly different loads in the intact specimen, but did so in specific spinal tissues. Despite methodological differences between studies, SMT forces and loading rates fell below published injury values. Future studies are warranted to understand if loading scenarios unique to SMT confer its differential therapeutic effects.

Mesenchymal stem cells in regenerative medicine: Focus on articular cartilage and intervertebral disc regeneration

Musculoskeletal disorders represent a major cause of disability and morbidity globally and result in enormous costs for health and social care systems. Development of cell-based therapies is rapidly proliferating in a number of disease areas, including musculoskeletal disorders. Novel biological therapies that can effectively treat joint and spine degeneration are high priorities in regenerative medicine. Mesenchymal stem cells (MSCs) isolated from bone marrow (BM-MSCs), adipose tissue (AD-MSCs) and umbilical cord (UC-MSCs) show considerable promise for use in cartilage and intervertebral disc (IVD) repair. This review article focuses on stem cell-based therapeutics for cartilage and IVD repair in the context of the rising global burden of musculoskeletal disorders. We discuss the biology MSCs and chondroprogenitor cells and specifically focus on umbilical cord/Wharton's jelly derived MSCs and examine their potential for regenerative applications. We also summarize key components of the molecular machinery and signaling pathways responsible for the control of chondrogenesis and explore biomimetic scaffolds and biomaterials for articular cartilage and IVD regeneration. This review explores the exciting opportunities afforded by MSCs and discusses the challenges associated with cartilage and IVD repair and regeneration. There are still many technical challenges associated with isolating, expanding, differentiating, and pre-conditioning MSCs for subsequent implantation into degenerate joints and the spine. However, the prospect of combining biomaterials and cell-based therapies that incorporate chondrocytes, chondroprogenitors and MSCs leads to the optimistic view that interdisciplinary approaches will lead to significant breakthroughs in regenerating musculoskeletal tissues, such as the joint and the spine in the near future.

Passive lumbar tissue loading during trunk bending at three speeds: An in vivo study

BACKGROUND

Low back disorders are closely related with the magnitude of mechanical loading on human spine. However, spinal loading contributed by the lumbar passive tissues is still not well understood. In this study, the effect of motion speed on lumbar passive moment output was investigated. In addition, the increase of lumbar passive moment during trunk bending was modeled.

METHODS

Twelve volunteers performed trunk-bending motions at three different speeds. Trunk kinematics and muscle activities were collected and used to estimate instantaneous spinal loading and the corresponding lumbar passive moment. The lumbar passive moments at different ranges of trunk motion were compared at different speed levels and the relationship between lumbar passive moment lumbar flexion was modeled.

FINDINGS

A non-linear, two-stage pattern of increase in lumbar passive moment was evident during trunk flexion. However, the effect of motion speed was not significant on lumbar passive moments or any of the model parameters.

INTERPRETATION

As reported previously, distinct lumbar ligaments may begin to generate tension at differing extents of trunk flexion, and this could be the cause of the observed two-stage increasing pattern of lumbar passive moment. The current results also suggest that changes in tissue strain rate may not have a significant impact on the total passive moment output at the relatively slow trunk motions examined here.

Low back pain prevalence in Brazil: a systematic review

The article describes the methodological quality of published studies on prevalence of low back pain in Brazil. Eighteen studies were considered eligible after searches in the following electronic databases: LILACS, PubMed, Embase, CINAHL, SPORTDiscus and SciELO. A high source of bias was observed in the criteria for external validity related to sampling, in addition to non-response bias. Considering the criteria for internal validity, the main sources of bias were the lack of an acceptable definition of low back pain and the use of instruments that lacked proven reliability and validity. No representative study was found that provides a generalizable prevalence of low back pain in Brazil. The published studies included in this review showed a high risk of bias that affects the prevalence data. Future studies with appropriate methodological design are necessary to verify the real impact of low back pain in Brazil and allow comparisons.

The influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination during weightlifting

Lumbar muscle fatigue is a potential risk factor for the development of low back pain. In this study, we investigated the influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination patterns during weightlifting. Each of the 15 male subjects performed five repetitions of weightlifting tasks both before and after a lumbar extensor muscle fatiguing protocol. Lumbar muscle electromyography was collected to assess fatigue. Trunk kinematics was recorded to calculate lumbar-pelvic continuous relative phase (CRP) and CRP variability. Results showed that fatigue significantly reduced the average lumbar-pelvic CRP value (from 0.33 to 0.29 rad) during weightlifting. The average CRP variability reduced from 0.17 to 0.15 rad, yet this change ws statistically not significant. Further analyses also discovered elevated spinal loading during weightlifting after the development of lumbar extensor muscle fatigue. Our results suggest that frequently experienced lumbar extensor muscle fatigue should be avoided in an occupational environment.

PRACTITIONER SUMMARY

Lumbar extensor muscle fatigue generates more in-phase lumbar-pelvic coordination patterns and elevated spinal loading during lifting. Such increase in spinal loading may indicate higher risk of back injury. Our results suggest that frequently experienced lumbar muscle fatigue should be avoided to reduce the risk of LBP.

The assessment of material handling strategies in dealing with sudden loading: the effects of load handling position on trunk biomechanics

Back injury caused by sudden loading is a significant risk among workers that perform manual handling tasks. The present study investigated the effects of load handling position on trunk biomechanics (flexion angle, L5/S1 joint moment and compression force) during sudden loading. Eleven subjects were exposed to a 6.8 kg sudden loading while standing upright, facing forward and holding load at three different vertical heights in the sagittal plane or 45° left to the sagittal plane (created by arm rotation). Results showed that the increase of load holding height significantly elevated the peak L5/S1 joint compression force and reduced the magnitude of trunk flexion. Further, experiencing sudden loading from an asymmetric direction resulted in significantly smaller peak L5/S1 joint compression force, trunk flexion angle and L5/S1 joint moment than a symmetric posture. These findings suggest that handling loads in a lower position could work as a protective strategy during sudden loading.

The assessment of material-handling strategies in dealing with sudden loading: the effect of uneven ground surface on trunk biomechanical responses

As a major risk factor of low back injury, sudden loading often occurs when performing manual material-handling tasks on uneven ground surfaces. Therefore, the purpose of the current study was to investigate the effects of a laterally slanted ground on trunk biomechanical responses during sudden loading events. Thirteen male subjects were subjected to suddenly released loads of 3.4 and 6.8 kg, while standing on a laterally slanted ground of 0°, 15° and 30°. The results showed that 8.3% and 5.6% larger peak L5/S1 joint compression forces were generated in the 30° condition compared with the 0° and 15° conditions, respectively. The increase of L5/S1 joint moment in the 30° condition was 8.5% and 5.0% greater than the 0° and 15° conditions, respectively. Findings of this study suggest that standing on a laterally slanted ground could increase mechanical loading on the spine when experiencing sudden loading. Practitioner Summary: Sudden loading is closely related to occupational low back injuries. The results of this study showed that the increase of slanted ground angle and magnitude of load significantly increase the mechanical loading on the spine during sudden loading. Therefore, both of these two components should be controlled in task design.

Identification of novel nucleus pulposus markers: Interspecies variations and implications for cell-based therapiesfor intervertebral disc degeneration

Mesenchymal stem-cell based therapies have been proposed as novel treatments for intervertebral disc degeneration, a prevalent and disabling condition associated with back pain. The development of these treatment strategies, however, has been hindered by the incomplete understanding of the human nucleus pulposus phenotype and by an inaccurate interpretation and translation of animal to human research. This review summarises recent work characterising the nucleus pulposus phenotype in different animal models and in humans and integrates their findings with the anatomical and physiological differences between these species. Understanding this phenotype is paramount to guarantee that implanted cells restore the native functions of the intervertebral disc. Cite this article: Bone Joint Res 2013;2:169-78.

High frequency of McKenzie's postural syndrome in young population of non-care seeking individuals

OBJECTIVES

The role of postural loads as a risk factor for back pain and musculoskeletal symptoms is unclear. McKenzie proposed in his classification of mechanical syndromes a postural syndrome, in which people only develop symptoms from sustained loading, which is relieved by a change in position and has no effect on movement or function. Because of the low level disability with postural syndrome, it was suggested that few seek healthcare for this problem.

METHODS

This study used a two-stage process first to give a questionnaire to 100 students and staff from a university to determine who appeared to have postural syndrome, and then applied a physical examination to those who consented.

RESULTS

One hundred and thirty-eight were approached, of who 100 completed questionnaires and 66% appeared to have postural syndrome. Of the 66 who appeared to have postural syndrome, 37 consented to have a physical examination. Of the 37, 31 met the criteria for postural syndrome, with postural syndrome being significantly associated with pain on sustained loading and pain abolition on posture correction. Most postural syndrome was in the lumbar spine and associated with sitting, but other sites and causes were also noted.

DISCUSSION

This study lends credibility to McKenzie's postural syndrome, but also suggests this as a possible precursor for future more disabling or painful problems. Postural syndrome may not feature in those seeking professional healthcare, but is clearly highly prevalent in a young population.

The effects of upper limb loading on spinal shrinkage during treadmill walking

INTRODUCTION

Everyday activities such as walking may elicit spinal shrinkage in an order of magnitude that has been related to lower back pain. The present study aims to compare the effects of unloaded treadmill walking with walking carrying loads representing everyday shopping tasks.

MATERIALS AND METHODS

Walking tasks were performed on seven healthy males and motion analysis was used to track four reflective markers at 100 Hz, dividing the spine into three segments. Static data was collected in 5-min intervals over a 30-min period.

RESULTS

Total spinal length and lumbar segment decreased with respect to time (p < 0.001). Load affected the percentage length change at each spinal segment (p < 0.005), with the lumbar segment showing greatest height loss at the highest load. The upper and lower thoracic segments showed greater anterior lean with the heavier loads (p = 0.000) and the lumbar segment showed the opposite trend (p = 0.000).

CONCLUSION

Results suggest that the body adopts less anterior lean with an immediate load-bearing demand, to decrease the necessary extension moment generated by the spinal extensors for spinal stability. Further postural alteration in the same direction is observed with prolonged loading. In combination with lumbar spinal shrinkage, such postural changes are likely to increase the loading on the facet joints and subsequently unload the discs which may be beneficial for those with low back pain.

Segmental lumbar rotation in patients with discogenic low back pain during functional weight-bearing activities

BACKGROUND

Little information is available on vertebral motion in patients with discogenic low back pain under physiological conditions. We previously validated a combined dual fluoroscopic and magnetic resonance imaging system to investigate in vivo lumbar kinematics. The purpose of the present study was to characterize mechanical dysfunction among patients with confirmed discogenic low back pain, relative to asymptomatic controls without degenerative disc disease, by quantifying abnormal vertebral motion.

METHODS

Ten subjects were recruited for the present study. All patients had discogenic low back pain confirmed clinically and radiographically at L4-L5 and L5-S1. Motions were reproduced with use of the combined imaging technique during flexion-extension, left-to-right bending, and left-to-right twisting movements. From local coordinate systems at the end plates, relative motions of the cephalad vertebrae with respect to caudad vertebrae were calculated at each of the segments from L2 to S1. Range of motion of the primary rotations and coupled translations and rotations were determined.

RESULTS

During all three movements, the greatest range of motion was observed at L3-L4. L3-L4 had significantly greater motion than L2-L3 with left-right bending and left-right twisting movements (p < 0.05). The least motion occurred at L5-S1 for all movements; the motion at this level was significantly smaller than that at L3-L4 (p < 0.05). Range of motion during left-right bending and left-right twisting at L3-L4 was significantly larger in the degenerative disc disease group than in the normal group. The range of motion at L4-L5 was significantly larger in the degenerative group than in the normal group during flexion; however, the ranges of motion in both groups were similar during left-to-right bending and left-to-right twisting.

CONCLUSIONS

The greatest range of motion in patients with discogenic back pain was observed at L3-L4; this motion was greater than that in normal subjects, suggesting that superior adjacent levels developed segmental hypermobility prior to undergoing fusion. L5-S1 had the least motion, suggesting that segmental hypomobility ensues at this level in patients with discogenic low back pain.

Spinal mechanical load as a risk factor for low back pain: a systematic review of prospective cohort studies

STUDY DESIGN

Systematic review.

OBJECTIVE

To review and critically evaluate the past literature for spinal mechanical load as risk factor for low back pain (LBP).

SUMMARY OF BACKGROUND DATA

LBP is a costly health problem worldwide, and treatments are often unsuccessful. Therefore, prevention might be more beneficial in the management of LBP. With respect to prevention, the knowledge of risk factors is essential. From the literature, exposures involving spinal mechanical load is frequently discussed as a potential risk factor for LBP. For a better understanding of this risk factor, we performed a systematic review of the literature. Additionally, we evaluated exposures of spinal mechanical load for possible dose-response relations with LBP.

METHODS

We systematically searched Medline, Embase, PsycINFO, and CINAHL databases (without language restriction) for full-report publications of prospective cohort studies, evaluating spinal mechanical load during work and/or leisure time activities as risk factors for nonspecific LBP in patients (>18 years of age) free of LBP at baseline. We assessed the methodology of each article and extracted information on population, response rates, characteristics of LBP, exposures, and estimated association(s), using standardized forms. We performed a best evidence synthesis of the obtained information.

RESULTS

In total, 18 studies were eligible (all rated as high methodologic quality) reporting on 24,315 subjects.

CONCLUSION

We found strong evidence that leisure time sport or exercises, sitting, and prolonged standing/walking are not associated with LBP. Evidence for associations in leisure time activities (e.g., do-it-yourself home repair, gardening), whole-body vibration, nursing tasks, heavy physical work, and working with ones trunk in a bent and/or twisted position and LBP was conflicting. We found no studies, thus no evidence, for an association between sleeping or sporting on a professional level and LBP.

Spinal mechanical load: a predictor of persistent low back pain? A prospective cohort study

Prospective inception cohort. To assess the prognostic value of spinal mechanical load, assessed with the 24-hour schedule (24HS), in subjects with acute non-specific low back pain (ALBP) and to examine the influence of spinal mechanical load on the course of ALBP. In view of the characteristics of the natural course of ALBP, this should be viewed as a persistent condition in many patients rather that a benign self-limiting disease. Therefore, secondary prevention could be beneficial. Spinal mechanical load is a risk factor for ALBP and possibly a (modifiable) prognostic factor for persistent (i.e. recurrent and/or chronic) LBP. One hundred patients from primary care with ALBP were eligible for inclusion. At 6 months, 88 subjects completed the follow-up. For the follow-up assessment a research assistant, unaware of our interest in the prognostic factors, contacted the subjects by telephone. Questionnaires were completed focusing on changes in demographic data and on the course and current status of ALBP. Persistent LBP occurred in 60% subjects. After multivariate regression analysis smoking (harmful) and advanced age (protective) were associated with persistent LBP. Differences in 24HS scores at baseline and follow-up were univariate-related to persistent LBP. Spinal mechanical load, quantified with the 24HS, is not a prognostic factor for persistent LBP. Modification of spinal mechanical load in terms of 24HS scores could be beneficial for secondary prevention in patients with acute LBP.