Cumulative Trauma Disorders
  • Developing Pain
  • Upper extremities, rarely lower
  • of all those places, hand/wrist most prevalent
Disorders of the muscular-tendon-bone-nervous system that are casual, precipitated or aggrevated by long term repeated exposure
Magnitude and trend
Risk Factors
  • Large Force
  • Awkward posture
  • High Repetition
  • Limited Rest or Recovery Periods

Ink pen example
Higher Risk Factors: 
  • Hand tool vibration
  • Cold Stress (temperatures)

- blood flow is essentially restricted or obstructed
Major types of CD
-Finger (Ex. texting)
-Elbow (ex. tennis elbow)
-Shoulder (ex bricklayers shoulder, frozen shoulder)
  • Most prevalant
  • Wrist can adopt all kinds of postures
  • natural wrist position is flat
  • Unnatural position occurs when the wrist is bent in either direction
Cost of Using a Laptop
  • Too low (not in normal line of sight)
  • Neck pain because of looking down all the time
  • Awkward posture: need wrist support for posture
  • when you do not have to look at the laptop or type, look somewhere else and remove your hands from the keyboard!
Carpel Tunnel
CTS (Carpel Tunnel Syndrome)
  • Opening between bones in wrist
  • When you apply small amounts of pressure with finger, large amounts of pressure fall on the carpel tunnel
  • Lots of nerves and tendons and blood flow
Hand Wrist Anatomy
  • To understand/ appreciate complexity
  • one of the most complicated mechanical devices
  • many degrees of freedom
Know the factors, do the opposite!
Easy to understand. 
Design Solutions
  • Power steering
  • Reduced gripping force
  • Regular posture
Wrist CD Posture
Higher degree of deviation, the more the force is on your wrist
Factors affecting wrist
  • Grasping small objects: 
    Ft = 3 x Fl
  • Pressing down or grasping a large object: 
    Ft = 4 x Fl

Ft = force going through the tunne 
Fl = Force of grasping
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