How accurate are patient-specific osteotomy guides and fixation plates in orthognathic surgery?

Abstract Purpose This study evaluates the accuracy of orthognathic surgical movements completed with patient-specific osteotomy guides and fixation plates and provides an example of the use of volumetric analysis to evaluate post-surgical results. Materials and methods Utilizing three-dimensional (3D) overlay and anthropometric points, the pre-operative virtual surgical plan (VSP) was compared to the post-operative computed tomography (CT) scan. The average deviation in the movements between each patient's scans was calculated; additionally, volumetric analysis consisted of overlapping the virtually planned jaws with the surgically obtained maxilla and mandible, allowing accuracy to be calculated as a percentage and provide visualization of where errors occurred. Results 9 orthognathic surgeries were completed using patient-specific guides and plates. In the anterior-posterior and left-right planes, the maxilla was under-corrected 0.79 mm and 0.01 mm respectively, whereas it was over-corrected in the superior-inferior plane by 0.15 mm; this corresponded with an average maxillary volume overlap of 82.59%. In the left-right and superior-inferior planes, the mandible was under-corrected 1.40 mm and 0.36 mm respectively, whereas it was over-corrected in the left-right plane by 0.10 mm; this corresponded with an average mandibular volume overlap of 77.52%. The volume overlap difference between the maxilla and mandible was not significant. Conclusion Patient-specific guides and plates in orthognathic surgery can achieve acceptable results when measured by traditional cephalometric point analysis. Our protocol demonstrates the use of pre- and post-surgical CT scans to compare and evaluate surgical outcome as a percentage of positional volumetric accuracy as well as pinpoint the sources of error.