• Matthias Müller, Florian Gras, Ivan Marintschev, Thomas Mückley, and Gunter O Hofmann.
• Department of Trauma, Hand and Reconstructive Surgery, Friedrich Schiller University, Jena, Germany.
• Comput. Aided Surg. 2009 Jan 1; 14 (4-6): 109-16.

ObjectiveA novel, radiation- and reference base-free procedure for placement of navigated instruments and implants was developed and its practicability and precision in retrograde drillings evaluated in an experimental setting.Materials And MethodsTwo different guidance techniques were used: One experimental group was operated on using the radiation- and reference base-free navigation technique (Fluoro Free), and the control group was operated on using standard fluoroscopy for guidance. For each group, 12 core decompressions were simulated by retrograde drillings in different artificial femurs following arthroscopic determination of the osteochondral lesions. The final guide-wire position was evaluated by postoperative CT analysis using vector calculation.ResultsHigh precision was achieved in both groups, but operating time was significantly reduced in the navigated group as compared to the control group. This was due to a 100% first-pass accuracy of drilling in the navigated group; in the control group a mean of 2.5 correction maneuvers per drilling were necessary. Additionally, the procedure was free of radiation in the navigated group, whereas 17.2 seconds of radiation exposure time were measured in the fluoroscopy-guided group.ConclusionThe developed Fluoro Free procedure is a promising and simplified approach to navigating different instruments as well as implants in relation to visually or tactilely placed pointers or objects without the need for radiation exposure or invasive fixation of a dynamic reference base in the bone.

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