Possible errors in pin insertion positions using the C-arm.

In order to measure errors in pin positions, a tibia with referenced pin insertions was radiographed in various locations using a mini C-arm. Changes in pin position locations up to seven millimeters and twelve degrees were found. To minimize these errors, limbs should be centered and parallel to the plane of the imaging screen of the C-arm. If possible, pin insertions should be made in this plane. Magnification due to the distance from the screen should be determined for precise pin positioning.