Illusory biplane radiographic images.

The commonly held belief that radiographs taken at right angles to one another will accurately portray the precise location of a metallic implant within a skeletal structure is erroneous. To the contrary, such biplane radiographs often provide misinformation about the exact location of metallic implants. The explanation for this phenomenon is discussed along with several methods to determine the accurate location of metallic implants when only biplane radiographs are available. Orthopedic surgeons should be particularly aware of this potential problem when biplane radiographs are taken at the time of insertion of multiple pins about the proximal femur.