Occupational Low Back Injuries Research Articles

Racism in Pain Medicine: We Can and Should Do More

Racism in Pain Medicine: We Can and Should Do More

The effect of axial twist angle on in vitro cumulative injury load tolerance: a magnitude-weighting approach for axial twist exposures

Axial twisting exposures have been repeatedly identified as a risk factor for occupational low back pain and injury, but there is a need for an improved understanding of the role of axial twist magnitude and associated joint moment as modifiers of the cumulative load tolerance of intervertebral joints. The purpose of this study was to mathematically characterise the relationship between axial twist motion magnitudes and the cumulative load tolerance of porcine cervical functional spinal units. Twenty-four porcine functional spinal units were fixed in a mechanical testing system under compressive load (15% of compressive tolerance) and in a neutral flexion-extension posture. Specimens were axially twisted to 5, 7.5, 10, 12.5, 15 or 17.5 degrees at 1 Hz until failure or 21,600 total cycles. Cumulative applied axial twist moment was recorded, and exponential functions were fit to the twist magnitude-cumulative twist moment measures. Weighting-factor functions for cumulative axial twist moment injury risk were developed based on absolute axial twist magnitude and twist normalised to maximum range of motion. While caution should be used in extrapolating these findings to human evaluation, a developed non-linear weighting-factor model has potential for use in assessment of cumulative axial twist injury risk in occupational tasks.

Effects of the New York State Workers Compensation Board Medical Treatment Guidelines on Return to Work.

Examine the association between New York State Workers' Compensation Medical Treatment Guidelines (Guidelines) adherence and return-to-work after occupational low back injuries. Assess adherence to Guidelines by examining diagnostic and treatment utilization. Retrospective chart review of cases. Outcomes of interest were lost time duration and diagnostic/treatment utilization rates. Time to event analyses performed using Kaplan-Meier plots and Cox proportional hazard model. Care received after implementation of Guidelines resulted in decreased lost time. Treatment rates were consistent, while diagnostic imaging use was inconsistent with Guidelines recommendations. Guidelines use positively influenced return-to-work after acute occupational low back injuries. Inconsistencies in following Guidelines were observed for diagnostic tests, having a potential paradoxical effect on lost time. Further studies are necessary to test for additional hypotheses.

ANAMT Technical Guideline (DT 05): prevention of occupational low back pain through back belts, lumbar support or braces.

Low back pain is a considerable global public health problem. Use of back belts in occupational settings arises from the expectation of countless biomechanical benefits, which together would contribute to the prevention of this problem. To orient students, physicians and health institutions on the use of back belts, lumbar support or braces for prevention of low back pain or injury among asymptomatic workers. The present guideline was developed based on a systematic literature review; 809 studies were located in database MEDLINE and 571 in EMBASE and Cochrane CENTRAL. Evaluating back-belt use as preventive intervention against low back pain demands quantifying benefits, harms and difficulties to implementation, as well as the methodological quality of primary studies. Despite the weak benefits reflected in the individual, partial and isolated results of a few studies, there is no consistent evidence for the use of back belts, lumbar supports or braces for primary prevention of low back pain or occupational low back injury among workers. According to the available evidence, back-belt use is not associated with reduction of absenteeism.

Flight Bags as a Cause of Back Injuries Among Commercial Pilots.

Pilots of fixed wing commercial aircraft face numerous occupational hazards. Low back pain is among the most common and costly workplace injury, though relatively little is known about causes of back injuries among pilots. The awkward lifting and twisting maneuvers in the flight deck to position flight bags has not been described as a cause of occupational back injury among pilots. A case series of low back injuries among pilots was identified and described by a retrospective review of charts at an airport-based clinic. Circumstances of occupational back injury, initial direct medical costs, treatment, and work status following evaluation were described. Over a 6-yr period, 37 occupational low back injuries among 35 pilots were evaluated and treated. Of these, 24 (65%) involved flight bags. Only 27% of pilots with flight bag-associated injuries were returned to work after initial evaluation; medications with sedating properties were frequently required for treatment. Injuries due to slips, trips, and falls, typically in jet bridges or associated with hotel shuttles, were common among pilots with back injuries not related to flight bags. The majority of occupational low back injuries seen among pilots in an airport based clinic were attributable to use of flight bags. Substituting electronic flight bags for traditional flight bags could contribute to back injury prevention among pilots.

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.

Unilateral ankle immobilization alters the kinematics and kinetics of lifting

Theoretical and empirical data support the notion that distal lower extremity joint dysfunction could influence the low-back injury potential of workers, but the impact of unilateral ankle immobilization on low-back loading during lifting has yet to be examined. To examine the influence of unilateral ankle immobilization on the kinematics and kinetics of lifting. With and without their right ankle immobilized, 10 men performed laboratory-simulated occupational lifting tasks. Together with force platform data, three-dimensional kinematics of the lumbar spine, pelvis, and lower extremities were collected, and a dynamic biomechanical model was used to calculate peak compressive and shear loads imposed on the L4/L5 intervertebral joint. In comparison to the unaffected conditions, ankle immobilization generally resulted in less knee (0.001 ≤ p ≤ 0.07) and greater lumbar spine (0.001 ≤ p ≤ 0.35) sagittal motion when lifting. Associated with this compensatory movement strategy were greater L4/L5 anterior/posterior reaction shear forces (0.001 ≤ p ≤ 0.25). However, there were cases when individual compensatory movement strategies differed from the "group" response (i.e., subjects increased their sagittal knee motion on the affected side about 8% of the time); this resulted in increased peak L4/L5 joint compression forces without changing the peak L4/L5 anterior-posterior shear forces. Ankle dysfunction can alter the way in which individuals move and load their low-backs when lifting. The different ways in which individuals compensate for personal movement constraints could alter the potential site and mechanism of occupational low-back injury.

The effects of transfer distance on spine kinematics when placing boxes at different heights

Twisting and lateral bending motions in repetitive lifting tasks are associated with occupational low back injuries and can be challenging to reduce with engineering controls. This study tested the hypothesis that twisting and lateral bending can be reduced by changing the transfer distance. Eighteen males, with no material handling experience lifted 10.9 kg boxes from 0.9 m above the floor and placed the boxes at a destination located 0.50, 0.75, 1.00, 1.25, 1.50, or 1.75 m away and at heights of 0.5 m, 0.9 m, and 1.3 m above the floor. Overall, twisting and forward bending decreased with increased transfer distance when placing the box. Conversely, the lateral bending when lifting and placing the box increased with increasing transfer distance. In short, having a transfer distance between 1 and 1.25 m when performing palletizing tasks to different heights may optimally balance spine kinematics, back injury risk, and productivity measures.

PROLONGED TRUNK FLEXION CAN INCREASE SPINE LOADS DURING A SUBSEQUENT LIFTING TASK: AN INVESTIGATION OF THE EFFECTS OF TRUNK FLEXION DURATION AND ANGLE USING A SAGITTALLY SYMMETRIC, VISCOELASTIC SPINE MODEL

Load-relaxation of the human trunk following prolonged flexion has been observed earlier, yet the adverse effects of such viscoelastic behaviors on performing demanding tasks (e.g. lifting) remain poorly understood. Theoretically, trunk stiffness reduces following flexion exposures and requires a compensatory increase in paraspinal muscle activation and spine loads. Here, a multi-segment model with nonlinear viscoelastic properties was developed. After evaluating the model, it was used to predict changes, due to a range of trunk flexion exposures, in several outcome measures (i.e. peak spine load, peak axial stiffness and absorbed energy) at L5/S1 during simulated lifting. All three measures increased during lifting following flexion exposures, including a ~ 9% (~ 284 N) increase in spine loads, and these changes were magnified by increasing flexion duration and angle. These results support prior epidemiological evidence that occupational low back injury risk is elevated when prolonged trunk flexion along with lifting are required. Further, the dependency of spine loads on loading conditions was determined in response to several flexion angles and loading durations. The current modeling approach is considered as an initial step toward implementing Kelvin-solid models in future viscoelastic spine models.

Dynamic spinal stability and kinematic variability across automotive manufacturing work shifts and days

Workplace activities performed repetitively over prolonged periods of time may affect spinal stability and the neuromuscular response to a perturbation. The primary goal of this study was to assess changes in local dynamic spinal stability and kinematic variability resulting from 1.5 h of repetitive automotive manufacturing work. Ten male operators performed a repetitive dynamic trunk flexion/extension task, used to assess spinal stability and kinematic variability, directly before and after completing one of two similar assembly line shifts involving static trunk flexion and reaching. The main effect of time (pre/post-shift) did not significantly affect any of the outcome variables (p > 0.05), except visual analogue scale low back pain scores (p < 0.001). Thus, despite increases in pain, operators were able to maintain their spinal stability post-shift. A secondary goal was to assess the between-day reproducibility of each dependent measure, by testing the operators at the same time on the following work day. Mean difference scores, precision of measurement values, and intraclass correlation coefficients are reported for future reference. Relevance to industryOne mechanism by which long-term repetitive work may contribute to occupational low back pain and injury is spinal instability. This study addressed this issue by testing automotive manufacturing operators directly before and after 1.5 h of repetitive assembly work.

Response to Dr. Sinnot's “Administrative Delays and Chronic Disability in Patients With Acute Occupational Low Back Injury”

Response to Dr. Sinnot's “Administrative Delays and Chronic Disability in Patients With Acute Occupational Low Back Injury”

Adjusting Rehabilitation Costs and Benefits for Health Capital: The Case of Low Back Occupational Injuries

Case-mix adjustments for treatment/rehabilitation costs and benefits of non-traumatic injuries, such as occupational back pain, are much more difficult than adjustments for traumatic injuries. We present a new method for adjusting for severity differences in the costs and benefits of treating occupational low back injuries. Using initial post-injury differences in the health capital of prospective sample of 1,831 occupational related back pain patients, we combine survey data with workers' compensation claim files and medical billing information to adjust the costs and benefits of treatment using multivariate techniques. We find that large differences in the net benefits of treatment between the three lowest cost provider groups virtually disappear once adjustments are made for worker's health capital (injury severity) at entry into treatment. Once adjustments are made for initial health capital immediately after injury, the net benefits of treating occupational low back pain are virtually identical for physician only care, physician plus physical therapy care, and chiropractic care. Net benefits of care are lower for combined physician/chiropractic care, and lowest for all other forms of care (principally, treatment by orthopedic surgeons). Our method is readily adapted for comparisons among individual health care/occupational rehabilitation professionals or among group practices and other health care organizations.

Administrative Delays and Chronic Disability in Patients With Acute Occupational Low Back Injury

This study assessed whether an organizational factor, delays to claim acceptance or administrative delays, had an influence on outcomes for individuals with acute back injuries in the workers' compensation system. Multivariate logistic regression was used to test whether individuals who experienced administrative delays were more likely to develop chronic disability than those who did not experience delays. Beyond the first 2 weeks, each interval of administrative delay was associated with increased odds of developing chronic disability. Injury severity, physician experience and weeks to medical treatment were additionally very strong predictors for the development of chronic disability. Insurers, employers, and policy makers can significantly reduce chronic disability if controls are adopted to reduce administrative and treatment delays and to direct workers to experienced clinicians.

Is a history of work-related low back injury associated with prevalent low back pain and depression in the general population?

BackgroundLittle is known about the role of prior occupational low back injury in future episodes of low back pain and disability in the general population. We conducted a study to determine if a lifetime history of work-related low back injury is associated with prevalent severity-graded low back pain, depressive symptoms, or both, in the general population.MethodsWe used data from the Saskatchewan Health and Back Pain Survey – a population-based cross-sectional survey mailed to a random, stratified sample of 2,184 Saskatchewan adults 20 to 69 years of age in 1995. Information on the main independent variable was gathered by asking respondents whether they had ever injured their low back at work. Our outcomes, the 6-month period prevalence of severity-graded low back pain and depressive symptoms during the past week, were measured with valid and reliable questionnaires. The associations between prior work-related low back injury and our outcomes were estimated through multinomial and binary multivariable logistic regression with adjustment for age, gender, and other important covariates.ResultsFifty-five percent of the eligible population participated. Of the 1,086 participants who responded to the question about the main independent variable, 38.0% reported a history of work-related low back injury. A history of work-related low back injury was positively associated with low intensity/low disability low back pain (OR, 3.66; 95%CI, 2.48–5.42), with high intensity/low disability low back pain (OR, 4.03; 95%CI, 2.41–6.76), and with high disability low back pain (OR, 6.76; 95%CI, 3.80–12.01). No association was found between a history of work-related low back injury and depression (OR, 0.85; 95%CI, 0.55–1.30).ConclusionOur analysis shows an association between past occupational low back injury and increasing severity of prevalent low back pain, but not depression. These results suggest that past work-related low back injury may be an important risk factor for future episodes of low back pain and disability in the general population.

Race Differences in Diagnosis and Surgery for Occupational Low Back Injuries

Population-based telephone survey in Missouri. To examine the unique contribution of race to diagnosis and surgery rates in workers' compensation claimants. Race differences in diagnostic specificity and rates of surgery may mediate documented differences in workers' compensation case management outcomes (treatment expenditures, disability ratings, and settlement awards) between African Americans and whites with low back injuries. African American (n = 580) and white (n = 892) workers' compensation claimants with single-incident low back injuries were interviewed regarding diagnoses and treatments received for their injury. Participants were, on average, 21 months after settlement. Analyses examined the association of race (controlling for clinical findings, legal representation, age, gender, and socioeconomic status) with diagnosis (herniated disc vs. regional backache) and surgery. Risk ratios for race were calculated. Whites were 40% more likely than African Americans to receive a herniated disc diagnosis. Of claimants with the latter diagnosis, whites were 110% more likely than African Americans to undergo surgery. Race differences in diagnosis and surgery may help to explain why African Americans, relative to whites, receive lower workers' compensation medical expenditures, disability ratings, and settlement awards.

Work Disability and Costs Caused by Recurrence of Low Back Pain: Longer and More Costly Than in First Episodes

Retrospective analysis of workers' compensation (WC) claims data for nonspecific low back injuries (LBI) in a single jurisdiction. To examine whether recurrences, defined as post-initial episodes of work disability or medical care, substantially contribute to total medical and indemnity costs, and total duration of work disability. Previous studies have not measured the proportion of care seeking and work disability that are associated with recurrences in claims for work-related LBI. All persons with new lost-time claims for nonspecific LBI reported in New Hampshire to a large WC provider from 1996 to 1999 were selected (N = 1867). Three years of follow-up data, starting at the beginning of the first episode, were collected. Previously validated definitions of recurrence were used identify new episodes of care and new episodes of lost work time (work disability). Total duration of work disability, total medical costs, and total indemnity costs were investigated. For individuals with recurrences, these variables were separated into first-episode and recurrent period duration and costs. The rate of recurrent work disability was 17.2%, and the rate of recurrent care seeking was 33.9%. Individuals with recurrence had significantly higher total length of work disability, and higher medical and indemnity costs. For those with recurrent work disability, 69% of total lost time from work, 71% of associated indemnity costs, and 84% of total medical costs occurred during the recurrent period. For those with recurrence of care, the respective values were 48%, 47%, and 42%. Recurrences contributed disproportionately to the total burden of work-related nonspecific LBI, through both additional care seeking and work disability. Results imply that those who have recurrences may be an especially important target for secondary prevention efforts.

Co-Contraction Recruitment and Spinal Load during Isometric Pushing Tasks

Pushing and pulling tasks account for 20% of occupational low-back injury claims but few studies have investigated the neuromuscular control of the spine during these tasks. Primary torso muscle groups recruited during pushing tasks include the rectus abdominis and external obliques. However, theoretical analyses suggest that co-contraction of the paraspinal muscles is necessary to stabilize the spine during flexion exertions. A biomechanical model was implemented to estimate co-contraction and spinal load from measured surface EMG and trunk moment data recorded during trunk flexion and extension exertions. Results demonstrate that co-contraction during flexion exertions was approximately twice the value of co-contraction during extension. Co-contraction accounted for up to 47% of the total spinal load during flexion exertions and spinal load attributed to co-contraction was nearly 50% greater during flexion than during extension exertions despite similar levels of trunk moment. Results underscore the need to consider neuromuscular recruitment when evaluating biomechanical risks. Keywords: Spine; Co-contraction; Push; Manual Materials Handling; Biomechanics

The effect of pallet distance on torso kinematics and low back disorder risk

Intervention research for prevention of occupational low back injuries has focused on the effects of reducing extreme torso flexion and the external moment. Little is known about prevention strategies for torso twisting and lateral bending. The objective of this study was to assess the effect of pallet distance with regard to a constant lift origin on the torso kinematics and a measure of low back disorder risk. Fifteen male participants transferred 11.3 kg boxes from a constant origin to six different regions on a pallet. Two pallet distances with regard to the lift origin were investigated. ANOVA indicated that increasing the pallet distance resulted in increases in torso kinematics (velocities and accelerations) as well as a measure of risk of low back disorder. The increases in torso kinematics (e.g. twisting and lateral awkward postures and bending velocities) occurred mostly at the lower height regions on the pallet. It is concluded that increasing the pallet distance with regard to the lifting origin, with the intention to influence the participant to take a step during a palletizing task does not appear to be an effective intervention strategy to reduce the risk of low back disorder associated with torso kinematics.

Factor Structure of the Pain Disability Index in Workers’ Compensation Claimants With Low Back Injuries

Tait RC, Chibnall JT. Factor structure of the Pain Disability Index in workers’ compensation claimants with low back injuries. Arch Phys Med Rehabil 2005;86:1141–6. Objective To examine the factor structure of a telephone-administered Pain Disability Index (PDI) and the effects of race and sex on the PDI. Design Computer-assisted telephone interviews of a cohort with occupational low back injuries. Setting General community. Participants Missouri workers’ compensation claimants (N=1329) with low back injuries. Interventions Not applicable. Main Outcome Measures PDI, levels of pain severity, Social Security Disability Insurance status, and the Fear-Avoidance Behavior Questionnaire. Results Results for the total sample and by race/sex group indicated support for a 2-factor model of the PDI corresponding to voluntary activities (eg, social, occupational, recreational) and obligatory activities (eg, activities of daily living, eating, sleeping). Additional psychometric analyses of the voluntary and obligatory subscales indicated adequate reliability and construct validity overall and in each of the race/sex groups. African Americans reported more pain-related disability on both subscales than whites. Women reported more disability on the voluntary subscale than men. Conclusions The results support use of the PDI as a bidimensional measure of pain-related disability, with strong psychometric properties. They also support its administration by telephone.

Race differences in diagnosis and surgery for occupational low back injuries

While recent research has documented treatment and outcome differences between African Americans and Caucasians with occupational low back injuries, race differences specific to diagnosis and surgery have not been examined. These relationships are important, in part because diagnostic specificity and surgery are strong predictors of disability ratings and settlement awards for occupational low back injuries. The current study was a population-based telephone survey in Missouri of African American (n = 580) and Caucasian (n = 892) Workers’ Compensation claimants with low back injuries whose claims were settled in 2001–2002.