The long-term goals of this research are to use an animal model to investigate pathophysiologic mechanisms and exposure-response relationships of aspects of repetitive loading of the finger and chronic musculoskeletal disorders of the upper extremity (e.g., carpal tunnel syndrome, trigger finger, epicondylitis). The goals of this pilot study are to develop the animal model and collect initial data to adequately demonstrate its effectiveness. The model involves implanting a wire near the motor nerve of the flexor digitorum profundus muscle in the rabbit forearm to control repetitive muscle contraction combined with precise control of load at the fingertip. While the rabbit is anesthetized the finger will be repetitively loaded for 2 hours per day, 5 days per week, until median nerve motor conduction latency across the carpal tunnel is prolonged. Completion of five specific aims will demonstrate the effectiveness of the model: (1) demonstrate that the implanted wires do not damage the median nerve, (2) demonstrate that a repetitive, high load condition causes median nerve entrapment at the carpal tunnel, (3) develop histologic techniques and a semi-quantitative scoring scheme for biologically important structural changes of nerve and tendon-related tissues, (4) estimate tendon stress and displacement produced by the model, (5) identify the histologic and electrophysiologic effects of three loading conditions. The results will provide the preliminary data for a full proposal to investigate the long-term goals. Ultimately, this information may be used in the design of work to prevent these disorders.
