Quantitative Biomechanical Analysis of Wrist Motion in Bone-Trimming Jobs in the Red-Meat Packing Industry

Abstract

This study was motivated by the serious impact that cumulative trauma disorders (CTDs) of the upper extremities have on industrial workers and on industry itself. To date, no quantitative data has been gathered on the kinematics of hand and wrist motion required in bone-trimming jobs in the red-meat packing industry. No information is known about what type and how much wrist motion is currently being used in bone-trimming jobs in the red-meat packing industry, or how much these motions increase the risk of occupational CTDs. The research conducted addressed this current research void and established a preliminary database of wrist and hand kinematics for a bone-trimming job in the red-meat packing industry. This kinematic database could augment the red-meat industry's efforts to reduce the severity and cost of CTDs. Ergonomics practitioners in the red-meat industry could use the kinematic methods employed in this research to assess the CTD risk of current and redesigned jobs that require repetitious, hand-intensive work.

The study examined the wrist motions used by nine red-meat packing workers who performed bone-trimming jobs. These jobs are highly repetitive and hand-intensive. Quantitative measures of the kinematic parameters of wrist motions performed on the bone-trimming line were measured using goniometry. The wrist motion measures consisted of the following statistics in the radial/ulnar, flexion/extension, and pronation/supination planes: 1). mean, minimum, and maximum of wrist angle position, 2). mean, minimum, and maximum of angular velocity, and 3). mean, minimum, and maximum of angular acceleration.

The kinematic data were compared to manufacturing industry's preliminary wrist motion benchmarks. These benchmarks were the means and variances of nine dependent variables of position, velocity, and acceleration from industrial workers who performed hand-intensive, repetitive work in jobs that were of low and high risk of hand/wrist CTDS (Marras and Schoenmarklin, 1993). Results of this comparison show that numerous wrist motion variables in both the left and right hands of bone-trimming workers are in the high-risk category. This quantitative analysis provides biomechanical support for the high incidence of CTDs in the bone-trimming line of the plant that was investigated.