Imageless Navigated Posterior Minimally Invasive Total Hip Replacement with the Orthosoft Navitrack System

not account for the imprecision associated with reaming or cup placement during surgery [9]. Imageless technology allows real-time intra-operative knowledge of the quantitative direction and depth of reaming; adjustment during reaming for variations in the bony anatomy to allow for correct cup coverage with optimal inclination; and allows adjustment of the anteversion of a cup to a desired combined anteversion through knowledge of the fixed femoral anteversion. In this study we determined the accuracy of, and reproducibility of, measurements of inclination, anteversion, and reproduction of the correct center of rotation of the acetabulum using the Orthosoft navigation program. Pelvic tilt was used to adjust the inclination and anteversion. Radiographs do not reflect the accuracy of the computer. The computer allows accurate real-time control of the placement of the acetabular components. If the femoral preparation is done first, so that the anteversion of the femoral component is known, the acetabulum can be customized for each patient to achieve a combined prosthetic mean anteversion of 35 +/– 5 degrees. The computer improved the skill of the surgeon to correctly and reproducibly implant the components.

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