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In vivo rabbit model of finger musculoskeletal disorders.

King-KB; Rempel-D
Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R01-OH-007786, 2008 Nov; :1-17
The goal of this project was to develop and validate a method for testing the biomechanical risk factors for occupational hand injury due to overuse. This project focused on the risk factors of force and frequency in order to determine how hard and fast a worker can perform a repeating hand task without injury. This is an important problem for the United States workforce because manual handling and similar tasks are on the rise along with upper musculoskeletal disorders. Even some jobs considered white collar such as dental hygiene are seeing increasing hand injuries which may be due to forceful and repetitive hand tasks like periodontal scaling. The design approach of this project was to measure the biological changes in finger joint tissues following repeated grip-like motions with groups of experiments testing different force levels and different frequency levels. Because measuring biological effects of joint tissues requires destructive methods (biochemistry, histology, etc.), it was necessary to first create an animal model for cyclical finger joint loading. Thus, the first aim of the project was to create an in vivo model that would simulate hand tasks using occupationally relevant loads and speeds. The second and third aims of the project were to measure the structural and biochemical changes resulting from the loading and to determine if these changes are co-localized. The fourth aim of the project was to test different force levels and different frequency levels to determine if thresholds of loading exist. The key accomplishment of this project is the development of the in vivo rabbit model for testing force and frequency of finger joint loading. The rabbit has similar joint, muscle, tendon and ligament anatomy with only a few exception (e.g., the 1st digit is not opposable like the human thumb), but these do not affect the use and value of the model. This new animal model applies precise loads to the digit tip at precise frequencies. At the end of each experiment, the loaded joint and the control non-loaded joint of the opposite limb are measured for structural and biochemical changes such as the amount of specific proteins required for joint function. Previous experimental animal models of loading have been developed by others; however, most of those models either rely on behavioral modification and/or training of the animal which do not provide consistent force or frequency levels or the model includes surgical alteration of the joint at the beginning of the experiment which doesn't address typical workplace issues. Prior to this project [5 R01 OH007786], no methodology existed for in vivo testing of force and frequency at levels of cyclical joint loading that were reasonable for understanding the biological effects of occupational hand tasks. Thus, the successful development of this experimental model is an important accomplishment in occupational safety research. Other major accomplishments of this project are 1) identifying a low frequency threshold i.e., the speed at which no changes (good or bad) occur, 2) identifying some proteins that are increased with loading, 3) identifying some proteins that are decreased with loading, and 4) identifying the effect of different force levels on these key proteins. These findings and future findings regarding the changes in proteins due to repetitive hand tasks are critical to identifying and understanding the biological mechanisms that connect specific levels of force and frequency of repetitive hand tasks to occupational injury. By understanding these mechanisms and their force and frequency threshold levels, logical interventions can be developed to prevent injury while maintaining productivity at work.
Laboratory-animals; Animal-studies; Muscles; Repetitive-work; Cumulative-trauma-disorders; Musculoskeletal-system-disorders; Biomechanics; Hand-injuries; In-vivo-studies; Risk-analysis; Injury-prevention; Exposure-levels; Exposure-assessment
Karen B. King, Ph.D., Mail Stop 8343, RC1 North, 12800 E. 19th Ave, Room 2103, Aurora, CO 80045
Publication Date
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Final Grant Report
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NIOSH Division
Source Name
National Institute for Occupational Safety and Health
Performing Organization
University of California - San Francisco