The Effects of Complex Wrist and Forearm Posture on Wrist Range of Motion
Marshall, Matthew M., Mozrall, Jacqueline R., Shealy, Jasper E., Human Factors
In order to minimize the risk of repetitive trauma injuries, postures or motions that place joints near the limits of their range of motion (ROM) should be avoided. The National Institute of Occupational Safety and Health (NIOSH) concluded in a recent survey of epidemiological studies that strong evidence exists to show a positive association between work that requires extreme postures and the prevalence of hand/wrist tendinitis (Bernard, 1997). Postural deviations are particularly important in combination with high-force exertions or highly repetitive motion (Keyserling, Donoghue, Punnett, & Miller, 1982). In an effort to study the role of wrist posture in the etiology of cumulative trauma disorders, much research has been done to determine the typical range of motion of the human wrist (Eastman Kodak Company, 1983; Neese, Konz, & Reams, 1989; Wagner, 1988; Webb Associates, 1978). Most of these studies, however, have looked at the wrist in terms of motion in a single, isolated plane (flexion/extension, radial/ulnar deviation, and forearm pronation/supination) without determining how the combinations and interactions of these individual motions may affect the ROM of the wrist.
The primary objective of this research was to determine if changing the complexity of the wrist/forearm posture would significantly affect the ROM of the wrist. If this is the case, it may be inappropriate to use these earlier ROM data as benchmarks for the capacity of wrist motion, given that most practical applications of such data involve complex deviations in more than one plane of motion. This is especially true of industrial and occupational applications, in which many of the jobs analyzed require simultaneous wrist motion in all three axes.
Secondary to the ROM study, we wanted to assess the accuracy of the Penny & Giles biaxial electrogoniometer (Biometrics Ltd., Gwent, United Kingdom) by comparing its measurements with those obtained manually and considered to be "true." Electrogoniometry offers a quick, objective, and relatively unobtrusive method of acquiring upper-extremity postural data. However, a number of problems with the instrument related specifically to crosstalk between the channels and zero drift of the instrument have been documented (Buchholz & Wellman, 1997).
The two sample groups consisted of 35 men (mean age of 23.0 years, standard deviation of 4.5) and 19 women (mean age of 22.4 years, standard deviation of 4.8). The participants were all volunteers from Rochester Institute of Technology. All participants were free of wrist pain and had no history of wrist disorders. Data for men and women were analyzed separately in this study to avoid the potential effects of anatomical differences and to be consistent with other ROM studies (Garrett, 1971; Neese, Konz, & Reams, 1989; Wagner, 1988). Previous research has shown that women typically exhibit more flexibility in the wrist joint than men (Webb Associates, 1978).
To ensure that the participants used in this study were representative of a normal population, participants' wrist circumference measurements were obtained for both men (mean of 17.3 cm, standard deviation of 0.82) and women (mean of 15.2 cm, standard deviation of 0.80). These values did not differ significantly from population data obtained by Webb Associates (1978), who found men to have a mean wrist circumference of 17.4 cm (standard deviation of 1.02) and women to have a mean of 15.4 cm (standard deviation of 1.03).
A fixture was built to provide accurate and reliable measurements of the angular displacement of complex wrist/forearm postures. Two plates were attached using a steel hinge joint that could move up and down (in the flexion and extension plane) while restricting lateral movement (in the radial and ulnar deviation plane). This fixture allowed flexion and extension to be performed and measured while participants maintained a secondary radial/ulnar deviation posture. …