The long term objectives of this line of research are to 1) characterize dose-response relationships between various physical exposures (force, repetition, etc) and development of carpal tunnel syndrome (CTS) due to chronic overuse; 2) study the injury, recovery, and reinjury cycle; and 3) characterize effects of modification of physical exposures to initial development of CTS and recurrence, for the purposes of establishing a direct link between chronic overuse and development of CTS, identifying threshold levels of physical exposures that can be considered low risk, characterizing the change in those threshold levels when physical exposures occur in combinations, and determining how these thresholds are altered if the interest is in prevention of recurrence of CTS. This application describes the initial steps towards those long term objectives. The primary specific aims of the proposed study are to 1) demonstrate a model for carpal tunnel syndrome associated with chronic overuse in the non-human primate, Macaca fascicularis; (2) Quantify the natural history of the recovery process for CTS; and (3) Determine if animals that have, by our objective measures, recovered are more prone to the recurrence of CTS. Research design and methods: six Macaca fascicularis monkeys will be trained to perform a highly repetitive pinching task for food rewards; task performance (force exerted, quantity and duration of pinches, intervals between pinches, etc) will be continuously monitored; every two weeks electrodiagnostic (EDX) test will be performed to assess sensory and motor latency; when slowing of 15% from baseline is detected two readings in a row, in either measure, subjects will meet the criteria for being positive for CTS. A no-work recovery period will follow, while maintaining biweekly EDX testing. Once EDX tests return to baseline or plateau for 3 successive readings, subjects will return to work, and will be monitored for recurrence. Time to recurrence will be compared with time to first occurrence. Importance of this work: What is missing from the existing body of knowledge is direct evidence of development of CTS in workers as a direct result of exposure to physical work factors (force, posture, etc) at levels that encountered in some work situations. The connection between physical work factors and occurrence of carpal tunnel syndrome in workers remains debate-able due to disparate findings from various epidemiological studies; the connection is obscured by the host of known, non-occupational risk factors for CTS. A novel model based on an animal with anatomy similar to humans, performing tasks voluntarily, at exposure levels that are seen in some more adverse human work environments, and properly scaled for the animal, would allow for characterization of dose-response relationships between CTS and various physical risk factors, while controlling for non-occupational factors. This innovative model has applicability for the study of primary and secondary prevention efforts in that address initial occurrence and recurrence of CTS, thereby providing scientific bases for establishment of exposure thresholds for healthy and previously affected workers and a means for quantifying intervention effectiveness.
| Sommerich, Carolyn M; Lavender, Steven A; Buford, John A et al. (2007) Towards development of a nonhuman primate model of carpal tunnel syndrome: performance of a voluntary, repetitive pinching task induces median mononeuropathy in Macaca fascicularis. J Orthop Res 25:713-24 |
