Carpal tunnel syndrome is the most common entrapment neuropathy in humans and accounts for significant disability, suffering and cost. There is strong evidence that it is related to occupations involving hand intensive work activity. The long-term objective of this line of research is to. use intracarpal pressure to specify hand maneuvers that can be safely performed in the workplace, which, if followed, will prevent carpal tunnel syndrome and wrist tendinitis. The basis for using intracarpal pressure (ICP) is: (1) elevated ICP in humans will cause an acute median neuropathy at the wrist, and (2) from animal studies and human histologic studies there is indirect evidence that elevated ICP will lead to a chronic entrapment neuropathy of the median nerve.
The specific aims are to (1) determine whether the relationships between ICP and hand maneuvers are consistent between subjects, (2) develop a mathematical model that will predict ICP based on hand maneuvers, and (3) determine whether there is a dose-response relationship between two currently accepted risk factors (repetition and wrist angle) and ICP in subjects performing simulated work tasks. The hand maneuvers to be evaluated are: wrist extension/flexion angle and wrist ulnar/radial deviation angle, metacarpophalangeal joint angle, and pinch force. Fifty normal subjects will be recruited from local newspapers to participate in this laboratory study. A blunt tipped 23-gauge catheter connected to a pressure transducer will be inserted at the wrist into the carpal space. Wrist motion will be tracked with a two-axes electronic goniometer. These outputs and the output of an electronic pinch meter will be sampled at 40 Hz and stored on a microcomputer. During the first phase subjects will perform elementary hand maneuvers while data is collected. In the second phase these results will be used to establish a mathematical relationship between hand maneuvers and ICP. During the third phase subjects will perform simulated work activities while varying task rate and wrist angle. The long-term results of this line of research will be of value to hand tool designers, industrial engineers, regulatory agencies and other interested in the design of work tasks to prevent work-related cumulative trauma disorders of the wrist.
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