Page 363

have shown how lift tables and lifting hoists are effective in mediating the risk of low back pain in industrial studies. The incorporation of such devices in the workplace permits the load to be raised mechanically, minimizing the load moment and thus reducing the biomechanical loading of the spine. Since risk is lowered when the load is changed from a heavy lift to a light lift, this finding would also be consistent with the rigorous epidemiologic findings. As demonstrated in this example, a pattern of evidence emerges that cuts across independent risk assessment approaches—epidemiologic, biomechanical, basic science, and interventions.

A similar pattern can be described for upper extremity disorders. Biomechanical studies have shown that the extraneural pressure in the carpal tunnel is increased with hand loading and nonneutral wrist postures. Basic science studies demonstrate how extraneural pressures lead to intraneural edema and fibrosis, demyelination, and axon degeneration. These changes in nerve structure cause loss of nerve function. Finally, a recent intervention study has demonstrated that alternative keyboards that reduce nonneutral wrist postures can mediate hand pain in patients with carpal tunnel syndrome.

In conclusion, a clear and strong pattern of evidence emerges after considering the epidemiologic, biomechanical, basic science, and intervention literature collectively. We can conclude with confidence that there is a relationship between exposure to many workplace factors and an increased risk of musculoskeletal disorders.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement