Deformation of palmar hand measurements in a power grip by wrist ulnar/radial deviation.

OBJECTIVES

The present study analyzed changes in palmar hand measurements during power grip by wrist radial/ulnar deviation for an ergonomic grip design.

METHOD: Twelve palmar dimensions (Tip-to-PTC/DTC distances, Tip-to-MMC distances, and Tip-to-MMC surface lengths) of digits 2 to 5 were measured for 30 Koreans with various hand sizes (15 males and 15 females; hand length = 177.9 ± 12.3 mm) at three wrist postures (neutral, 20° of radial deviation, and 30° of ulnar deviation) using 3D scanning and casting methods.

RESULTS

As the hand changed from the straight neutral posture to the power grip posture, the Tip-to-PTC/DTC distances (related to grip widths), Tip-to-MMC distances (related to grip heights), and Tip-to-MMC surface lengths (related to grip circumferences) decreased to 30%-65% compared to corresponding original lengths. Wrist posture also had significant effects on the Tip-to-PTC/DTC and Tip-to-MMC distances by 6.5%-9.0%, while finger position significantly affected all the measurements by 8.2%-22.3%.

PRACTITIONER SUMMARY: The measurement protocol of palmar hand dimensions and the changes in palmar hand measurements by wrist posture are of use to develop an ergonomic handle design for comfort and prevention of musculoskeletal disorders.