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- Discussion:
    - two fat planes on lateral view & 5 fat planes on PA view are useful for analysis;
    - deep fat pad of pronator quadratus (lateral view), which lies between the pronator quadratus muscle and the flexor tendon sheaths, normally forms a slight ventral concave line and is convexly bowed in a ventral direction or completely absent under pathologic conditions;
    - second fat plane seen on lateral view is dorsal skin subcutaneous fat line overlying dorsal hand, wrist, and forearm;
    - under normal conditions, it is a flat or dorsal concave line (at level of the wrist), and is considered to be abnormal when convex in a dorsal direction