Radiographic Assessment of Three Dimensional Mandibular Position Using Splint-less Patient Specific Implant

Overview

The purpose of this study was to assess the accuracy of a splint-less approach for mandibular jaw orthognathic surgery. This approach utilized a personalized orthognathic surgical guide (POSG) system, which comprised a set of cutting guides and 3D printed custom titanium fixation plates for bilateral sagittal split osteotomies (BSSOs). The cutting guides were first used to predrill screw holes and guide osteotomies. The custom plates were then used to reposition and stabilize the bony segments as planned, without the use of surgical splints or any additional tool such as surgical navigation

Surgical technique: The buccal bony surface of the mandible was exposed as a routine sagittal split osteotomy. First, the mandibular cutting guide was installed using the tooth-borne splint portion of the guide. Second, the lower portion of the guide was temporarily fixed with titanium screws through the designed screw holes on the guide. The planned margins for vertical osteotomy/ ostectomy were then marked by a pencil. Once the cutting guide was removed, the sagittal split osteotomy was completed as usual. Finally, the distal and proximal segments were fixed together using the custom plates and screw holes that were used by the cutting guide. Accuracy of preoperative surgical planning, and validation of the use of patient specific implants (PSI) in bilateral sagittal split osteotomy (BSSO) by comparing the planned outcomes to the actual postoperative outcomes by two methos. A)Evaluation the discrepancy between planned and obtained post-operative position of the mandibular plates, rami, and occlusion by analyzing the discrepancies in terms of rotation (roll, pitch and yaw) and translation (antero-posterior, lateral and vertical). These movements were determined by incorporating the segments in homologous bounding-boxes, aligning the planned model to the post-op result colorimetric map inspection. B) Measurements of the linear differences between the planned and postoperative positions of the mandibular midlines, the chin, and the gonial angle.