Do Occupational Risks for Low Back Pain Differ From Risks for Specific Lumbar Disc Diseases?: Results of the German Lumbar Spine Study (EPILIFT)

The effect of back muscle fatigue on EMG and kinematics based estimation of low-back loads and active moments during manual lifting tasks

This study investigated the effects of back muscle fatigue on the estimation of low-back loads and active low-back moments during lifting, using an EMG and kinematics based model calibrated with data from an unfatigued state. Fourteen participants performed lifting tasks in unfatigued and fatigued states. Fatigue was induced through semi-static forward bending. EMG, kinematics, and ground reaction forces were measured, and low-back loads were estimated using inverse dynamics and EMG-driven muscle model. A regression model was developed using data from a set of calibration lifts, and its accuracy was evaluated for unfatigued and fatigued lifts. During the fatigue-inducing task, the EMG amplitude increased by 2.8 %MVC, representing a 38% increase relative to the initial value. However, during the fatigued lifts, the peak EMG amplitude was found to be 1.6 %MVC higher than that observed during the unfatigued lifts, representing a mere 4% increase relative to the baseline unfatigued peak EMG amplitude. Kinematics and low-back load estimates remained unaffected. Regression model estimation errors remained unaffected for 5 kg lifts, but increased by no more than 5% of the peak active low-back moment for 15 kg lifts. We conclude that the regression-based estimation quality of active low-back moments can be maintained during periods of muscle fatigue, although errors may slightly increase for heavier loads.

The effect of head movement restriction on the kinematics of the spine during lifting and lowering tasks

This study aimed to examine the effects of head movement restriction on relative angles and their derivatives using the stepwise segmentation approach during lifting and lowering tasks. Ten healthy men lifted and lowered a box using two styles (stoop and squat), with two loads (i.e. 10% and 20% of body weight); they performed these tasks with two instructed head postures [(1) Flexing the neck to keep contact between chin and chest over the task cycle; (2) No instruction, free head posture]. The neck flexion significantly affected the flexion angle of all segments of the spine and specifically the lumbar part. Additionally, this posture significantly affected the derivatives of the relative angles and manifested latency in spine segments movement, that is, cephalad-to-caudad or caudad-to-cephalad patterns. Conclusively, neck flexion as an awkward posture could increase the risk of low back pain during lifting and lowering tasks in occupational environments. Practitioner summary: Little information is available about the effects of neck flexion on other spine segments' kinematics and movement patterns, specifically about the lumbar spine. The result of this experimental study shows that neck flexion can increase the risk of low back pain by increasing lumbar flexion angle and spine awkward posture.

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

Objectives

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

Methods

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

Results

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

Conclusions

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

Predictors of the conservative management outcomes in patients with lumbar herniated nucleus pulposus: A prospective study in Indonesia

BACKGROUND

The objective of this study was to identify the predictors of the conservative management outcomes in patients with lumbar herniated nucleus pulposus (HNP).

METHODS

A prospective study was conducted between June 2010 and April 2012 in Banda Aceh, Indonesia. Clinical and baseline neurologic examinations such as passive straight leg raising test (SLRT), cross SLRT, and patellar and Achilles reflexes were assessed prior to the conservative management. The patients were evaluated at 2nd, 4th, 8th, 12th and 24th week following commencement of the conservative management.

RESULTS

We recruited and followed 171 HNP patients of which 35.7% of them had good outcome. At univariate analysis, patients with more than 12 months duration of complaint, those with dominant radicular pain, severe pain intensity (visual analogue scale 7-10), positive SLRT, positive cross SLRT, and reduced motor power of knee extensors (muscle strength grade 1-4), were associated with poor outcome. Multivariate analysis suggested that patients with dominant radicular type of pain were likely to had poor outcome compared to those with dominant back pain (odd ratio (OR) 10.57 with 95% confidence interval (CI) 1.15-96.93). Patients with reduced motor power of knee extensors also had a higher chance to have poor outcome compared to those who were normal (OR: 10.57; 95% CI: 1.15-96.93).

CONCLUSION

Type of pain and the strength of lower extremities could be able to predict the failure of conservative management in patients with lumbar disc herniation. However, further studies with the bigger sample size are warrant to validate our results.

Real-time feedback to reduce low-back load in lifting and lowering

Low-back pain (LBP) is a common health problem. Literature indicates an exposure-response relation between work-related lifting and LBP. Therefore, this study investigated effects of three kinds of real-time feedback on low-back load, quantified as lumbar moments, during lifting. We recruited 97 healthy male and female participants without a recent history of LBP and without prior biomechanical knowledge on lifting. Participants were assigned to groups based on the time of enrollment, filling the four groups in the following order: moment feedback, trunk inclination angle feedback, lumbar flexion feedback, and a control group not receiving feedback. Feedback was given by a sound when a threshold level of the input variable was exceeded. Participants were unaware of the input variable for the feedback, but were instructed to try to avoid the audio feedback by changing their lifting strategy. The groups with feedback were able to reduce the audio feedback and thus changed the input variable towards a more desired level. Lumbar moments significantly decreased over trials in the inclination and moment feedback groups, remained similar in the lumbar flexion group and increased in the control group. Between group comparisons revealed that low-back load was significantly lower in the moment and inclination groups compared to the control group. Additionally, moments were lower in the inclination group than in the lumbar flexion group. Real-time feedback on moments or trunk inclination is a promising tool to reduce low-back load during lifting and lowering.

Understanding outcome metrics of the revised NIOSH lifting equation

The interpretation of the calculated result of the revised NIOSH Lifting Equation (RNLE) has been problematic because the relationship of the calculated result to back injury risk has not always been either well understood nor consistently interpreted. During the revision of the ISO standard 11228-1 (Manual lifting, lowering and carrying), an extensive literature review was conducted on validation studies of the RNLE. A systematic review of exposure-risk associations between the LI metrics and various low-back health outcomes from peer-reviewed epidemiological studies was conducted. Risk interpretations for different levels of calculated result of the RNLE are added to the ISO standard. Rationale for the risk interpretations is presented in this paper.

Lumbar disc herniation: long-term outcomes after mini-open discectomy

PURPOSE

The outcomes of mini open discectomy in lumbar disc herniation are usually satisfying. Our study aims at finding if its results are still good at long-term follow-up.

METHODS

We reviewed 552 patients operated between 1993 and 2013 by mini open discectomy procedure. Our main evaluation criterion is a modified Stauffer and Coventry classification applied during follow-up visits at three months, one year, five years, and every five years. The secondary criterion was the Oswestry Disability Index.

RESULTS

The outcomes are considered good to very good in 87.3% of the cases at one year follow-up. These results deteriorate after an average follow-up of 14.7 years but remain satisfactory with 63.7%. The global decrease is 23.6%. The Oswestry Score decreases by 35 points at the same follow-up. In addition, 6.52% of patients required fusion at first revision and 1.08% at second revision. We also noticed 51 (9.2%) post-operative recurrences at the same level. In 23 (4.16%) of them, we proceeded to a new discectomy in an average interval of 41.4 months. At an adjacent level, 29 patients (5.2%) presented a new symptomatic disc herniation; among them, eight cases (1.44%) needed discectomy. The re-operative rate (including recurrent disc herniation and fusion for degenerative indications) is 10.68% at the last follow-up.

CONCLUSIONS

Nearly 2/3 of our patient series keep satisfactory outcomes after about 15-year follow-up. The mini open discectomy remains a reliable surgical technique provided we respect the indications and surgical requirements. This procedure also avoids excessive instrumentation and its possible iatrogenic complications. Powerful randomized and controlled trials are needed to strengthen these deductions.

Effects of supplemental heat therapy in multimodal treated chronic low back pain patients on strength and flexibility

BACKGROUND

The beneficial effects of thermotherapy on analgesia and relaxation are widely known for various diseases. To date, however, thermotherapy in chronic low back pain is not explicitly recommended in international guidelines. The effects of thermotherapy on biomechanical parameters within a multimodal back pain treatment concept are also unknown.

METHODS

Within a multimodal treatment concept, 176 patients with chronic low back pain were treated either with or without supplemental heat wrap therapy. The range of movement and strength parameters of the trunk in flexion, extension, lateral flexion and rotation were measured before and after 12 weeks of treatment.

FINDINGS

The range of movement as well as strength parameters of the trunk improved on average within the multimodal treatment. Patients receiving additional thermotherapy supplemental to basic multimodal treatment showed a further improvement of strength parameters regarding extension (P = 0.09, 1 - β = 0.41), rotation to the right (P = 0.09, 1 - β = 0.41) and rotation to the left (P = 0.08, 1 - β = 0.42) in comparison to those conducting only the multimodal treatment. No group differences were detected in flexibility.

INTERPRETATION

The implementation of thermotherapy for several hours a day (heat wrap therapy) in daily clinical practice additional to an individualized, evidence-based multimodal treatment concept can be recommended to enhance strength parameters. The potential causes of improved strength parameters as well as the meaning for the patients in activity of daily living are discussed.

Extended compilation of autopsy-material measurements on lumbar ultimate compressive strength for deriving reference values in ergonomic work design: The Revised Dortmund Recommendations

Measures of human physical capacity are required in ergonomic work design. To avoid biomechanical low-back overload, criteria are needed to differentiate load and overload. With respect to the evaluation of manual materials handling and similar physical exposures regarding potential overload, the compression component of the forces transferred via lumbar discs or vertebrae are compared with the ultimate compressive strength of lumbar-spine segments in a common biomechanical approach. As mechanical load-bearing capacity cannot be quantified directly in vivo, forces are applied to dissected spinal elements up to failure, which is interpreted as a measure of ultimate strength or tolerance to compression. Corresponding autopsy-material measurements were collected from literature and examined regarding several conditions: At the very minimum, a specimen consists of a complete vertebra or a disc including the adjacent endplates; failure is identified definitely as lumbar; compressive-force application is quasi-static; results are given as single values etc. This study continues previous collations, the latest is dated on 2001 including 25 usable out of 47 investigations totally. Currently, 66 newly discovered seemingly appropriate studies were collected via a systematic literature search, 11 of them were added for subsequent analysis. Nearly 4,000 values were compiled, 1,192 remained for analysis. Human lumbar ultimate compressive strength varies between 0.6 and 15.6 kN, mean and standard deviation are 4.84 ± 2.50 kN. For data originating from donors of specified gender and aged 20 years or more, the distributions are characterised by 6.09 ± 2.69 kN for male adults (n=305) and 3.95 ± 1.79 kN for female adults (n=205). According to a linear regression model for donors aged 20 years or more, strength significantly decreases with age: 10.43 kN minus 0.923 kN per 10 years of age for males and 7.65 kN minus 0.685 kN per decade for females. Based on these gendered age relations, the "Revised Dortmund Recommendations" were derived ranging between 5.4 kN for males aged 20 years and 2.2 kN for males of 60 years or more. The corresponding recommended limits for females amount to 4.1 and 1.8 kN, respectively. A specific safety margin was implemented for young adults up to 25 years of age as skeletal strength may not be fully developed. Due to the compression-related and biomechanical nature of this approach, other influences like shear or torsion as well as psychological or psychosocial risk factors remain unconsidered despite their undoubted importance for initiating complaints, disorders and diseases at the low-back region.

Do Technical Aids for Patient Handling Prevent Musculoskeletal Complaints in Health Care Workers?-A Systematic Review of Intervention Studies

The physical load ensuing from the repositioning and moving of patients puts health care workers at risk of musculoskeletal complaints. Technical equipment developed to aid with patient handling should reduce physical strain and workload; however, the efficacy of these aids in preventing musculoskeletal disorders and complaints is still unclear. A systematic review of controlled intervention studies was conducted to examine if the risk of musculoskeletal complaints and disorders is reduced by technical patient handling equipment. MEDLINE®/PubMed®, EMBASE®, Allied and Complementary Medicine Database (AMED), and Cumulative Index of Nursing and Allied Health Literature (CINAHL®) were searched using terms for nursing, caregiving, technical aids, musculoskeletal injuries, and complaints. Randomized controlled trials and controlled before-after studies of interventions including technical patient handling equipment were included. The titles and abstracts of 9554 publications and 97 full-texts were screened by two reviewers. The qualitative synthesis included one randomized controlled trial (RCT) and ten controlled before-after studies. A meta-analysis of four studies resulted in a pooled risk ratio for musculoskeletal injury claims (post-intervention) of 0.78 (95% confidence interval 0.68-0.90). Overall, the methodological quality of the studies was poor and the results often based on administrative injury claim data, introducing potential selection bias. Interventions with technical patient handling aids appear to prevent musculoskeletal complaints, but the certainty of the evidence according to GRADE approach ranged from low to very low.