Question

13. A meat processing plant worker is gripping the handle of a common straight handled knife. Using the assumptions and dimensions provided in Figure 1 and Table 1, quantitatively prove that 1) wrist extension is more hazardous than wrist flexion; and 2) people with small wrists may be at higher risk of wrist injury.(10 pts) .Angle of wrist deviation-35 Required grip force of the handle 16N Coefficient friction between the tendon and its supporting synovia can be ignored SMALL 0BJECT GRASP IL LANG AN PRESSING DOWN OR LARGE 0ECT GRAS ALL NAN 43, LARGE HAND Figure 1 Radius of Curvature (mm) Table 1 Wrist Thickness Extension Flexion 5%ile Female 95%ile Male mrm 31.8 44.8 8.9 12.0 15.0 18.1 FN - Fr/R From T able 1 Lange nt

Answer 1

There are some studies indicate with discomfort felt in hand moment with different positions..peak flexion moment greater than the peak extension moment because of the larger summed physiological cross- sectional area of the flexors...poor design hand tool occur when increased incidence of acute trauma and subacute disorders of the wrist,flexion had less effect on MVC grip,compared to extention of the wrist..

Angle of wrist deviation 35°

Required grip force of the handle 16N

Approximately 29.43N for 10° flexion/ extension and 49.05 for 20° in flexion/ extension difference between effect on MVC grip compared to 10° and 20° ulnar deviation at p= 0.038 and 0.002 respectively..if 35° deviation range of motion to wrist extension less than maximum range of flexion of the wrist..reduction on the grip MCV greater for extension in terms of the angular deviation of the wrist..