A study of ergonomic risk factors and interventions among aerospace engineers

This dissertation describes an ergonomic study of engineers at an aerospace firm. The first paper is a cross-sectional study intended to investigate the risk factors associated with entrapment neuropathies at the wrist. The second and third papers describe a randomized controlled trial designed to determine whether a forearm support board and/or a neutral forearm posture mouse, when used by engineers with heavy computer usage, would (1) reduce the incidence of upper body musculoskeletal disorders, (2) reduce discomfort severity, and (3) alter the distal motor latency of the median or ulnar nerve at the right wrist.;Methods. The cross-sectional study of 202 engineers utilized questionnaires and electrophysiological nerve testing at the wrist. The definition for median or ulnar mononeuropathy required the combination of distal upper extremity discomfort and abnormal distal motor latency. The randomized controlled intervention trial followed 206 engineers for one year. Participants were randomized to receive a conventional mouse or an alternative mouse, and a forearm support board or no board. Outcome measures included weekly upper body discomfort scores and incident musculoskeletal disorders.;Findings. The prevalence of neuropathy at the wrist was 10.3% (right median), 3.4% (left median), 1.8% (right ulnar) and 2.9% (left ulnar). Three variables demonstrated positive associations with median neuropathy (body mass index, hours of computer use, and antihypertensive medication) and three variables with negative associations (typing speed, driving hours, total break time). With the intervention study, 42 participants were diagnosed with an incident musculoskeletal disorder. The group that received the forearm support board experienced a reduction of their right upper extremity discomfort (beta-coefficient = -0.35, 95% C.I. = -0.67 to -0.03) in comparison to those who did not receive this board. The group that received the alternative mouse had a protective, but non-significant (p=0.20), effect on incident cases of right upper extremity musculoskeletal disorders (HR=0.57, 95% C.I.= 0.24 to 1.34) and a non-significant reduction in neck-shoulder discomfort (beta-coefficient = -0.23, 95% C.I.=-.056 to 0.10) in comparison to the conventional mouse.