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often involves the management of failed surgical procedures, the utilization of pain clinics, functional restoration programs, and controversial drug regimens and surgical procedures. The panel examined the broader systems approach, dealing with primary and secondary prevention, and thought these more applicable to the interface between job demands and the population of workers.

This chapter is organized as follows: First, we revisit the conceptual model ( Figure 1.2) that forms the framework for workplace interventions and discuss the related principles of ergonomics. We then summarize the intervention literature specific to the back and upper extremities. Practical considerations, including assessment of cost-outcome effectiveness, are included, particularly as a framework for future research. Finally, we draw conclusions based on the weight of current evidence and suggest efforts to coordinate the gathering and sharing of further information to assess and prevent musculoskeletal disorders in the workplace.

CONTEXT

The conceptual model described in Figure 1.2 illustrates how the complex relationship among external loads, organizational factors, individual factors, and the social environment of work can lead to adverse outcomes that include pain, impairment, and disability. This conceptual model is also useful to understand how workplace interventions are used to control potentially adverse conditions.

Primary and secondary interventions may prevent adverse outcomes by reducing or eliminating external loads, changing organizational factors, altering the social environment, improving individual stress-coping skills, or matching the physical demands of the job with the employee's physical capacities. The literature suggests that some of these approaches are more successful than others. Some interventions have not yet been adequately assessed.

External loads in the work environment act on the body to create internal loads on tissues and other anatomical structures. Interventions that focus on the reduction or elimination of exposure to external loads must first identify and quantify the motions and forces acting on the individual, including vibration and thermal exposures. Often a systematic study of the work is required to evaluate these physical exposures and their characteristic properties. When specific physical stress factors are identified, the sources of these loads are ascertained. Workplace redesign may include alterations in tools, equipment, workstations, materials handled, tasks, work methods, work processes, and work environment, based on their contributions to the identified stresses. The majority of the intervention literature is based on this approach to injury reduction.



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