Patient's Body Size Influences Dental Hygienist Shoulder Kinematics

OCCUPATIONAL APPLICATIONS This study found that dental hygienists are exposed to higher shoulder elevation angles when treating a simulated big-girth patient versus a simulated average-girth patient. These differences in motion patterns may increase dental hygienists’ susceptibility to shoulder musculoskeletal disorders. Ergonomic interventions may be needed to facilitate solutions to problems associated with treating patients who are overweight or obese. Ergonomics and human factors practitioners should educate dental hygienists to be more aware of their body posture, specifically shoulder position, while working on patients with big chest girth. TECHNICAL ABSTRACT Background: Dental hygienists suffer from musculoskeletal disorders of the upper extremities, and the prevalence of these disorders increases with years of occupation. Furthermore, the prevalence of overweight and obese individuals in the United States has been rapidly increasing for both adults and children in recent years. This may increase the involvement of dental hygienists with obese patients, which may result in an increased prevalence of shoulder musculoskeletal disorders. The effect of patient's body size on the three-dimensional humeral and scapular kinematics of dental hygienists, however, is currently unknown. Purpose: The aim of the current study was to measure the influence of patient girth on the shoulder kinematics of dental hygienists during teeth instrumentation in a simulated work environment. Method: Sixteen female dental hygienists participated in a lab-based study that simulated a dental hygienist workplace. Three-dimensional kinematic data were collected for the right and left scapula and humerus using the Polhemus Liberty magnetic tracking system (Colchester, VT, USA). To quantify differences in humeral and scapular kinematics and exposure variables, two independent variables with two levels were chosen: handedness and body type size. Separate two-way ANOVAs with repeated measures were conducted. Results: Dental hygienists sustained significant higher mean humeral elevation angles and higher mean scapular upward rotation angles for the dominant and non-dominant hands while instrumenting a simulated patient with big girth chest. Furthermore, dental hygienists spent significantly more time above 30° and 60° of humeral elevation for the dominant and non-dominant hands while instrumenting this simulated patient. Conclusion: This study provided evidence that dental hygienists alter their shoulder kinematics while instrumenting patients having a larger girth. Consequently, working with patients who are obese, or with a larger body size, may increase dental hygienist susceptibility to shoulder musculoskeletal disorders.