An Experimental Model for Occupational Hand Disorders

In many occupations workers perform tasks which require repeated or forceful hand movements. Over time these repetitions may lead to one or more musculoskeletal disorders or diseases of the elbows, hands and fingers. These include epicondylitis (tennis elbow), carpal tunnel syndrome, and degenerative joint disease (e.g. osteoarthritis). At this time, precisely how repeated movements cause these disorders is not clear.

To understand the direct cause of these disorders we must replicate these actions in a controlled laboratory experiment. To do this we have developed a rabbit repetitive finger flexor model. In this model, the finger is flexed for a set number of repetitions at a predetermined frequency and force. After the flexion sessions are completed, the elbow (epicondyle), carpal tunnel, and finger joints are examined by histology and biochemistry for pathology (i.e. changes in nerve and connective tissues such as tendon, cartilage, and bone).

This model allows us to examine and compare the effects of high vs. low load and high vs. low repetition. By varying the combination of load and repetition levels we will determine the relative importance of each factor. We will also determine the risk of injury involved with each factor. Our ultimate goals are to clarify the development of these musculoskeletal diseases and to prepare injury prevention guidelines relating dose (load and repetition) to injury (development of disease).

These research projects have been/are being supported by the following agencies: National Institute of Occupational Safety and Health and the Center for Disease Control & Prevention (Rempel: R03OH03664) and (King: K01OH00183), and University of California at Berkeley Center for Occupational and Environmental Health (COEH) (King: T42/CCT 910427).

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