INDUSTRIAL WRIST MOTIONS AND INCIDENCE OF HAND WRIST CUMULATIVE TRAUMA DISORDERS

One of the major research voids in the study of occupational hand/wris t cumulative trauma disorders (CTDs) is the lack of quantification of the relationship between the known kinematic risk factors, such as wri st angle and repetition, and CTD risk. A previously published article in this journal (Marras and Schoenmarklin 1993) reported the descripti ve results from a quantitative surveillance study performed in industr y in which worker's wrist motions were monitored on the factory floor. The wrist motion components that were monitored on each subject were position, velocity, and acceleration measures in each plane of movemen t (radial/ulnar, flexion/extension, and pronation/supination). The obj ective of this article was to form a metric that associates the degree of incidence of hand/wrist CTDs with those types of wrist motions tha t were significant in the earlier paper. Of all the kinematic paramete rs measured, multivariate analysis of the motion data revealed that ac celeration in the flexion/extension plane discriminated the best betwe en groups of low and high incidence rates of CTDs. The epidemiological association between flexion/extension acceleration and CTD incidence rate is compatible with results from empirical studies and theoretical models in the physiologic and biomechanical literature. The flexion/e xtension acceleration values from this study can serve as preliminary motion benchmarks that establish relative risk levels of CTDs for hand -intensive, highly repetitive jobs that do not require hand tools. Ind ustrial practitioners can use this methodology, along with other accep ted tools, to enhance ergonomic assessments of jobs.