X-rays are only two-dimensional views inside a very complex structure. The two rows of wrist bones are all odd shapes held together like a jigsaw puzzle. Some bones in the first row overlap the bones in the second row. In other words, they don't line up underneath each other all the way across the wrist.
If the fracture is at an odd angle it's difficult to see on an X-ray. Usually a standard CT scan is needed to show angles and change in position of the bones.
New 3-D technology may be on the horizon. Japanese researchers have found a way to use 3-D imaging combined with computer software to create a model of the bone structure. By using the patient's normal side and comparing it to the injured side, they are able to see much more than 2-D images provide.
This kind of information helps the doctor diagnose quickly and accurately. Knowing exactly what's wrong helps the physician decide the best treatment and reduces complications.