The disparate diameter. A sign of rotational deformity in fractures

Although clinical assessment is usually better than radiographic evaluation in detecting rotational deformity at a fracture site, the forearm is an exception to this rule. A simple radiologic sign is here described which may uncover rotational fracture deformity: in the absence of comminution, whenever the diameter of a long bone changes abruptly across a fracture line, a significant rotational deformity must be considered. The basis for and applications of this sign are described.