A heavy tool from my work area fell off the wall and hit my wrist. When I went to the hospital, they X-rayed my arm. After three X-rays, the technician came back for one more X-ray. By that time, my arm was in extreme pain from the change in positions. Is it really necessary to make sure my wrist is in one exact position and not rotated?

Actually, doctors who study X-rays (radiologists) are asking this same question. Most positions for X-rays have been determined by studying the bones of cadavers (human bodies preserved for study). With live humans, there may be a significant effect of the muscles acting on the bones.

Perhaps slight differences in position aren't that important. But until this question can be cleared up, it's necessary to follow standard procedures and keep the wrist "just so" during X-rays.