Workday Arm Elevation Exposure: A Comparison Between Two Professions

Abstract

OCCUPATIONAL APPLICATIONS Results from this study indicate that dental hygienists spent a mean of 7% of their workday with their arms elevated above 60° of humeral elevation. The majority of their workday (71%) was spent working with their arms in static positions. Compared to a separate working population (office workers), dental hygienists had more than two times greater arm elevation exposure above 60°. Dental hygienists have a high incidence of shoulder injuries, which may be related to arm elevation exposure. Based on the present study, ergonomic interventions should be based on reducing the total arm elevation exposure in dental hygiene. Further, interventions should be designed to reduce the repetitive tasks performed by dental hygienists. TECHNICAL ABSTRACT Background: The prevalence of shoulder-related musculoskeletal disorders among dental hygienists working in the United States has been reported to be between 21% and 60%. Arm elevation exposure levels above 60° have been identified as potentially harmful in other occupations. Purpose: The aim of this study was to measure arm elevation exposure in dental hygienists in a single workday and to compare these data with those from another occupation with a lower risk for shoulder impingement syndrome. Methods: Bilateral, full workday arm elevation exposure was measured for both dental hygienists and computer workers using a tri-axial accelerometer with a built in data logger (Virtual Corset®, Microstrain, Inc., VT, USA). Exposures analyzed were the percent of the workday spent above 30°, 60°, and 90° of humeral elevation. Additionally, exposure to repetitive motion, or jerk, was estimated, specifically the percent time spent moving the arm in pseudo-static (<10°/s) slow humeral motion (between 10°/s and 40°/s) and fast humeral motion (>40°/s). Results: Dental hygienists had bilateral arm elevations above 60° for approximately 7% of their workday, more than two times the exposure of office workers for the same duration of work. Dental hygienists had a mean of 71% of their work time in pseudo-static postures, which is significantly less than computer workers (78%). Dental hygienists had slow and fast arm motion during 23% and 6% of their workday, respectively, significantly higher than those for computer workers (17% and 5%). Conclusions: Arm elevation exposure levels among dental hygienists are relatively high and may contribute to upper extremity injuries within this profession. In dental hygiene work, elevation exposure above 60° and dynamic arm motions above 10°/s may be specific contributors to the risk of upper extremity disorders bilaterally.