Measurement of the Internal Shape of Power Grip in Wrist Ulnar/Radial Deviation

Abstract

The present study proposes a method for measurement of the internal shape of power grip using casting and 3D scanning method. Three handle design dimensions and twelve handle design related hand dimensions were defined by referring hand anthropometry studies. Thirty Korean participants with various hand length were recruited. Power grip hand shapes with different wrist postures (radial deviation 20°, ulnar deviation 30°, neutral 0°) were measured using casting material and 3D scanning system. Separately measured inner hand and outward hand shape were combined and edited during post-processing of hand scan data. Power grip inner shape was analyzed in terms of width, height, and circumference. The width of the internal power grip shape was largest at 28.9 mm in the radial deviation posture and smallest at 26.3 mm in the ulnar deviation posture. The height and circumference of the power grip were the largest in the neutral wrist position (36.9 mm, 81.8 mm) and decreased 2% to 7% and 1% to 3%, respectively, in the ulnar/radial deviation posture compared to a neutral posture. The analysis of the internal shape of the hand according to the wrist posture can be applied to the design of the handle used for wrist radial/ulnar deviation posture.