|
| Reducing low back disorders for mine workers |
Background
Extensive evidence exists that work-related low back disorders affect mine workers to a greater degree than workers in other industries. Studies have shown that miners experience more disability from back pain, more disk degeneration, and a higher rate of worker’s compensation claims in comparison to other industrial populations. Low back disorders are consistently the single leading cause of lost-time injuries in the U.S. mining industry. The high incidence of low back disorders in mining is certainly a reflection of the physically demanding nature of mining jobs; however, the mining environment often imposes additional biomechanical demands by forcing workers to adopt restricted postures (such as stooping or kneeling) for prolonged periods when working. In terms of low back stress, the stooping posture (which involves flexion of the torso) is of particular concern and has been associated with increased risk for low back disorders in epidemiologic studies.
Many scientists believe that back pain is the result of a cumulative process of damage to spinal tissues caused by repetitive loading. However, few studies have examined the tolerance of spinal tissues to repetitive loading, and none have examined how increased spinal loads when lifting in torso flexion affect how quickly spinal tissues fail when they are loaded repetitively. Accordingly, a cadaver study involving 54 spine motion segments (two vertebrae and the intervening disc) was performed to simulate compressive and shear forces during simulated lifting of a 9-kg load in three torso flexion postures (neutral, partial flexion, full flexion). The number of cycles to specimen failure was used as the primary dependent measure. Results demonstrated that the number of cycles to fatigue failure were dramatically reduced in simulated flexed lifting compared to lifting in more upright postures. The average number of cycles to failure for upright, partial flexion, and full flexion were 8846, 4549, and 1485, respectively. The more rapid development of spinal tissue failure in flexed lifting may help explain the high incidence of low back disorders in coal mining (where flexed lifting is prevalent), but also have great relevance toward development of effective prevention measures. In particular, these results suggest that exposure to flexed lifting may be a key risk in low back disorders and that minimizing such exposure may be quite effective in reducing low back disorders in mining.
Potential Outcome
Results of this study and other important recent research findings related to low back pain are currently being used in the development of an “evidence-based” low back exposure assessment tool for the mining industry. The specific aims of this project are to develop guidelines and a tool for a paper-and-pencil low back exposure assessment that (1) is applicable to the unique physical stresses encountered in the mining environment, (2) takes advantage of recent research findings on potential injury pathways to the low back, and (3) is easy to use and administer. This tool is currently being pilot tested at a cooperating minesite. If this approach proves ultimately successful in developing a model that can predict risks of low back disorder at mining worksites, by 2009 the proposed exposure assessment tool is likely to have a remarkable impact on the design and evaluation of work tasks in the mining industry.