Radiographic distortion artifact of circular external fixators.

Abstract

Circular external fixators are commonly used to surgically treat a variety of orthopedic conditions. However, distortion artifact may mislead the radiographic interpreter as to the true anatomic location of the transfixing wires and either negatively impact patient healing or lead to unnecessary procedures. Distortion is due to unequal magnification of different parts of an object. The purpose of this study was to assess distortion of three circular external fixator apparatuses with the transfixing wires at 30, 60, and 90°. Distortion was greatest with all three apparatuses at 10° of rotation from parallel to the central X-ray beam. When comparing distortion between the three apparatuses, distortion was greatest with the transfixing wires at 30°. The study authors concluded that distortion artifact is most severe when the transfixing wires are at smaller angles and when they are farther from the X-ray table. The circular external fixator should be placed in the center of, and parallel to, the primary X-ray beam and as close to the table as possible to reduce/prevent distortion artifact and possible radiographic misinterpretation of transfixing wire location.