X-Ray Twisting Your Arm? Here's WhyYou just had an X-ray taken of a very painful wrist. The X-ray technician comes back and tells you that one more view is required. This time you have to turn your hand and forearm in the very position that hurts the most. Is this really necessary?
Actually, doctors who read X-rays (radiologists) are asking the same question. Radiologists have studied cadavers (human bodies preserved for study) to determine correct positions for X-rays. From these studies, doctors decided that one X-ray of the wrist had to be done with the hand in a neutral position. The shoulder and elbow had to be in specific positions as well.
X-rays of the wrist are often taken with the forearm slightly rotated. This places the hand in a palm down position. When this happens by mistake, a second X-ray is needed. In the next X-ray, the wrist and forearm must be in a neutral position--or so say cadaver studies.
These researchers decided to conduct X-ray studies on human volunteers to see whether the cadaver findings hold true in live arms. The researchers thought there would be a difference in the position of bones in a live arm because of muscle forces. A study of 15 healthy adults was done to find out how important slight differences in hand placement might be. X-rays were taken of the wrist in three different positions. The space difference between the ends of two forearm bones in the wrist was measured.
The results were a bit tricky to interpret. The difference in the position of the bones was considered significant in research terms. However, the researchers pointed out that a statistical difference isn't necessarily an important difference in the clinical setting. Getting another X-ray with the forearm and wrist in a neutral position may not be necessary after all.
Results for "normal" subjects might not be the same as those for patients with wrist problems. Maybe the bones would move differently if the person was in pain or unable to move easily. Age or sex may also make a difference.
It's important for radiologists to know if the standard arm positions used in X-rays are giving them the information they need. Since these positions were decided on cadavers, it's time to study them on live human subjects. More studies will be done to explore this issue.
George L. Yeh, MD, et al. Effects of Forearm Rotation on the Clinical Evaluation of Ulnar Variance. In The Journal of Hand Surgery. November 2001. Vol. 26A. No. 6. Pp. 1042-1046.
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