File:Negative ulnar variance.png

Summary

Negative ulnar variance. This patient has negative ulnar variance, that is, the ulnar does not reach as far distally as the radius. Here, the entire articulation is given by the red lines. The blue lines represent the articular area not used because the ulna is too proximal. In this anatomic configuration the carpus articulates with the radius alone, thereby creating a smaller contact area for the lunate, with resultant greater pressure on it. (Pressure, is of course, force/area; and a smaller area for a given force leads to increased pressure.) In turn, the bone is more apt to fail mechanically.

From https://orthopaedia.com/page/Kienbocks-disease

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