Biomechanics and Pathomechanics of carpal bone instability.

Biomechanics and Pathomechanics

Please click on the image below to enlarge images

The radial deviation wrist position; position of the scaphoid in closer proximity to the radius

Conversely, the ulnar deviated position pulls the scaphoid away from the radius. 

Angle is measured between a line drawn along long axis of scaphoid and the short axis of lunate perpendicular to the lunate capitate space.

Scapholunate angle

• Normal: 30 - 60°
• Questionably abnormal: 60 - 80°
• Abnormal: > 80° This indicates instability of the wrist.

quoted from

Louis A. Gilula and Ileana Chesaru

Wrist - Carpal instability
The Radiology Assistant

The numbers are soft, but this is a guide

• VISI < 30 degrees
• Normal 30 - 60 degrees
• DISI > 60 degrees

Normal angle

VISI

Normal angle

DISI

Carpal bone instability types.

The Mayo classification (Table 1) divides carpal instability into four major categories:

Imaging of Wrist joint (jordan Aug 2014) - Dr Mamdouh Mahfouz (In Arabic)