Chapter 1 Introduction to the Issues Chapter 2 Scientific Approach Unique to This Book Chapter 3 Epidemiological Studies on Low Back Disorders (LBDs) Chapter 4 Functional Anatomy of the Lumbar Spine Chapter 5 Normal and Injury Mechanics of the Lumbar Spine Chapter 6 Lumbar Spine Stability: Myths and Realities Chapter 7 LBD Risk Assessment Chapter 8 Reducing the Risk of Low Back Injury Chapter 9 The Question of Back Belts Chapter 10 Building Better Rehabilitation Programs for Low Back Injuries Chapter 11 Evaluating the Patient Chapter 12 Developing the Exercise Program Chapter 13 Advanced Exercises.

Low Back Disorders : Evidence-Based Prevention and Rehabilitation

A continuing challenge for ergonomists has been to determine quantitatively the types of trunk motion and how much trunk motion contributes to the risk of occupationally-related low back disorder (LBD). It has been difficult to include this motion information in workplace assessments since the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of LBD during occupational lifting in industry. Over 400 industrial lifting jobs were studied in 48 varied industries. The medical records in these industries were examined so that specific jobs historically categorized as either low, medium, or high risk for occupationally-related LBD could be identified. A tri-axial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers worked at these low, medium, or high risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model indicated that a combination of five trunk motion and workplace factors predicted well both medium risk and high risk occupational-related LBD. These factors included lifting frequency, load moment, trunk lateral velocity, trunk twisting velocity, and trunk sagittal angle. Increases in the magnitude of these factors significantly increased the risk of LBD. The analyses have enabled us to determine the LBD risk associated with combined changes in the magnitudes of the five factors. The results indicate that by suitably varying these five factors observed during the lift collectively, the odds of high risk group membership may decrease by over ten times. These results were related to the biomechanical, ergonomic, and epidemiologic literature. The five trunk motion and workplace factors could be used as quantitative, objective measures to redesign the workplace so that the risk of occupationally-related LBD is minimized.

Biomechanical risk factors for occupationally related low back disorders

A prospective analysis of the sagittal profile of 100 healthy young adult volunteers was carried out in order to evaluate the relationship between the shape of the pelvis and lumbar lordosis and to create a databank of the morphologic and positional parameters of the pelvis and spine in a normal healthy population. Inclusion criteria were as follows: no previous spinal surgery, no low back pain, no lower limb length inequality, no scoliotic deviation. For each subject, a 30×90-cm sagittal radiograph including spine, pelvis and proximal femurs in standing position on a force plate was performed. The global axis of gravity was determined with the force plate. Each radiograph was digitized using dedicated software. The spinal parameters registered were values for thoracic kyphosis and lumbar lordosis. The pelvic angles measured were: pelvic incidence, sacral slope and pelvic tilt. The global axis of gravity was on average 9 mm anterior of the center of the femoral heads. The anatomic parameter of pelvic incidence angle varied from 33° to 85° (mean: 51.7°, SD: 11°). The average lumbar lordosis was 46.5°. The average thoracic kyphosis was 47°. We found a statistical correlation between incidence angle and lumbar lordosis (r=0.69, P<0.001) and between sacral slope angle and lumbar lordosis (r=0.75, P<0.001). Spine and pelvis balance around the hip axis in order to position the gravity line over the femoral heads. We propose a scheme of sagittal balance of the standing human body.

Sagittal morphology and equilibrium of pelvis and spine.

Falling poses a major threat to the steadily growing population of the elderly in modern-day society. A major challenge in the prevention of falls is the identification of individuals who are at risk of falling owing to an unstable gait. At present, several methods are available for estimating gait stability, each with its own advantages and disadvantages. In this paper, we review the currently available measures: the maximum Lyapunov exponent (λS and λL), the maximum Floquet multiplier, variability measures, long-range correlations, extrapolated centre of mass, stabilizing and destabilizing forces, foot placement estimator, gait sensitivity norm and maximum allowable perturbation. We explain what these measures represent and how they are calculated, and we assess their validity, divided up into construct validity, predictive validity in simple models, convergent validity in experimental studies, and predictive validity in observational studies. We conclude that (i) the validity of variability measures and λS is best supported across all levels, (ii) the maximum Floquet multiplier and λL have good construct validity, but negative predictive validity in models, negative convergent validity and (for λL) negative predictive validity in observational studies, (iii) long-range correlations lack construct validity and predictive validity in models and have negative convergent validity, and (iv) measures derived from perturbation experiments have good construct validity, but data are lacking on convergent validity in experimental studies and predictive validity in observational studies. In closing, directions for future research on dynamic gait stability are discussed.

/pdf/assessing-the-stability-of-human-locomotion-a-review-of-2k18qbw2kd.pdf

Assessing the stability of human locomotion: a review of current measures

OBJECTIVE--To investigate the risk factors for low back pain in hospital nurses, with particular emphasis on the role of specific nursing activities. METHODS--A cross sectional survey of 2405 nurses employed by a group of teaching hospitals was carried out. Self administered questionnaires were used to collect information about occupational activities, non-occupational risk factors for back symptoms, and history of low back pain. RESULTS--The overall response rate was 69%. Among 1616 women, the lifetime prevalence of back pain was 60% and the one year period prevalence 45%. 10% had been absent from work because of back pain for a cumulative period exceeding four weeks. Rates in men were generally similar to those in women. In women back pain during the previous 12 months was weakly associated with height, and was significantly more common in those who reported frequent non-musculoskeletal symptoms such as headache and low mood. After adjustment for height and non-musculoskeletal symptoms, significant associations were found with frequency of manually moving patients around on the bed, manually transferring patients between bed and chair, and manually lifting patients from the floor. In contrast, no clear increase in risk was found in relation to transfer of patients with canvas and poles, manually lifting patients in and out of the bath, or lifting patients with mechanical aids. Confirmation of these findings is now being sought in a prospective study of the same population. CONCLUSIONS--This study confirms that low back pain is highly prevalent among nurses and is associated with a high level of sickness absence. People who often report non-musculoskeletal symptoms were significantly more likely to report low back pain. Specific manual handling tasks were associated with an increased risk of back pain; however, no such association was found with mechanised patient transfers.

https://oem.bmj.com/content/oemed/52/3/160.full.pdf

Manual handling activities and risk of low back pain in nurses.

The influence of dynamic factors on triaxial net muscular moments at the L5/S1 joint during asymmetrical lifting and lowering.

Manual handling techniques: Comparing novices and experts

Validation of two 3-D segment models to calculate the net reaction forces and moments at the L(5)/S(1) joint in lifting

Muscular mechanical energy expenditure as a process for detecting potential risks in manual materials handling.

Handling patients in bed using a pique (a waterproof padded sheet placed under the patient) is associated with a high incidence of risks for the spine with, in particular, the activity of pulling and turning the patient with the pique representing the highest risk. Fifteen female nursing aides were evaluated for compression and shear forces at the L5/S1 joint and for selected muscular activities in the trunk and shoulders. Films, force platforms and EMG recordings supplied the data; dynamic segmental analyses were performed to calculate reaction forces at L5/S1, and a planar single-muscle equivalent was used to estimate internal loads. Different execution parameters were examined including execution velocity, height of bed, direction of effort, leg position and knee support. A ‘free’ task, and a manual task not involving the pique, were also investigated. Recommendations are made for reducing spinal loading. The results also suggest that a change of direction in the trunk motion may present some risks whe...

Micheline Gagnon

Papers

The influence of dynamic factors on triaxial net muscular moments at the L5/S1 joint during asymmetrical lifting and lowering.

Manual handling techniques: Comparing novices and experts

Validation of two 3-D segment models to calculate the net reaction forces and moments at the L(5)/S(1) joint in lifting

Muscular mechanical energy expenditure as a process for detecting potential risks in manual materials handling.

Lumbo-sacral loads and selected muscle activity while turning patients in bed