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Risk Factors and Sources of Injury > Ulnar Deviation When Using the Keyboard          
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Animation Showing Ulnar Deviation on a KeyboardUlnar Deviation When Using the Keyboard

What is Ulnar Deviation?

Ulnar Deviation is a position where the hands are bent outward (in the direction of the fifth/little finger) at the wrist joint. 

Comparing the width of the shoulders of an adult and the width of the spacing of the hands when placed on the home row of a standard conventional keyboard, it is clear that the shoulders are wider. To compensate for this typists are forced to bend their wrists outward to comfortably type and create a 90° angle between the home row and their hands.

Ideally the hands should be in alignment with the forearm, so that a straight line can be drawn through the center of the forearm, the wrist, and through the third (middle) finger, with no "bend" or lateral deviation at the wrist. The use of the thumb can also be a cause of ulnar deviation as it is shorter than the other digits, and as such the hands are rotated outwards in order to make it easier for the thumb to reach keys.

Why is Ulnar Deviation a Risk Factor?

The bend in the wrist constricts blood flow in addition to requiring sustained muscle tension that further reduces blood flow to the muscles. In addition the median nerve runs through the carpal tunnel in the wrist, and ulnar deviating the span of this tunnel is compressed and pressure on this nerve can lead to Carpal Tunnel Syndrome

How Much Ulnar Deviation is "OK" and not a Risk Factor?

Every individual has different dexterity, endurance, fatigue rates and degrees of strength in their hand muscles and ligaments. A slight amount of deviation will not normally cause any numbness, pain or discomfort. A large portion of the population now spends most of their working day on their keyboard, and with these prolonged sessions, even a nominal degree of sustained ulnar deviation can pose a risk factor.

What are the Symptoms of Ulnar Deviation?

Symptoms to look for which indicate that ulnar deviation throughout the workday has become a problem include pain, numbness or tingling in the fingers and weakness in the hand and fingers.

How can the Choice of Keyboard Help to Reduce Ulnar Deviation?

Adjustable Keyboards
which can adjust to "split" or "splay" to accommodate varying shoulder widths and eliminate ulnar deviation. The modules on  Separated Keyboards can separate and be directly aligned with the shoulders to eliminate ulnar deviation, allowing the hand to be perpendicular to the orientation of the keyboard. 

Keyboards which minimize range of movement and have a lighter touch can help reduce pressure on the median nerve by reducing repetitive muscle strain which can cause inflammation and pressure on the median nerve.

What Other Strategies can be used to Reduce Ulnar Deviation?

Often individuals will bend their wrist while they are asleep without being conscious of this movement. The wearing of a wrist brace or support while sleeping can prevent unintentionally ulnar deviating for no reason.

To reduce awkward reach associated with combination keystrokes involving multiple keys (i.e. CTRL-ALT-DEL), a potential solution is to use Footswitches for the modifier keys (CTRL, ALT, SHIFT).


Last edited July 17th, 2018

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