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Occlusal-Based Intraoperative Surgical Positioning Guides: The missing link between virtual and actual orthognathic surgery.
Introduction: Advances in computer-aided design and modeling (CAD/CAM) have revolutionized preoperative planning in orthognathic surgery. Three dimensional (3D) virtual surgery allows an unparalleled visual understanding of the intended pre and post-operative skeletal and soft tissue relations after repositioning the maxillofacial skeletal segments. Virtual planning is replacing the traditional indirect planning techniques of 2-D cephalometry and articulated model surgery. Despite this remarkable advancement, intraoperatively, surgeons still employ the old methods of orthognathic surgery for repositioning skeletal segments, relying upon multiple splints, intraoperative intermaxillary fixation, external reference landmarks, and manual guesswork at condylar positioning. Based on virtual CAD/CAM planning and surgery, we introduce the use of occlusal based intraoperative surgical positioning guides (SPG) to address this issue. SPG are intraoperative guides that directly translate the virtual plan to the actual surgical procedure.
Methods and Patients: SPG are CAD/CAM designed intraoperative guides that reference selected stable skeletal landmarks to the mobilized skeletal-dental segments of the maxillofacial skeleton. SPG allow precise intraoperative translation of the virtual plan to the operating theater. SPG are designed by the surgeon during virtual surgery for the maxilla (LeFort I), mandible (BSSO-inverted L) and/or chin. SPG are manufactured from acrylic through additive stereolithographic techniques. The initial SPG establishes the stable reference landmarks, placed above or proximal to osteotomy lines and the final SPG translates the planned virtual movements of the osteotomized maxillofacial skeleton to the reference landmarks. Eighteen skeletally mature maxillofacial deformity patients have been treated utilizing surgical positioning guides and virtual preoperative planning. The patient diagnoses include cleft lip/palate, hemifacial microsomia, non-syndromic class II and class III dental facial deformities, facial asymmetry and craniofacial dysostoses. The performed osteotomies included one and multi-piece LeFort I osteotomies, sagittal split osteotomies, segmental mandibular osteotomies, inverted-L ramus osteotomies and genioplasties.
Results: All 18 patients had successful treatment outcomes with this surgical approach. Virtual planning, virtual design, and intraoperative application of surgical positioning guides will be illustrated through multiple case presentations.
Conclusions: The use of SPG offers all of the advantages of CAD/CAM virtual surgical planning, replacing cephalometry, face-bow transfers, and articulated model surgery. SPG then link the virtual plan to the operating theater. SPG allow for single splint surgery even with double-jaw procedures. SPG eliminate the need for intermediate splints, and eliminate the requirement for intraoperative intermaxillary fixation. During mandibular surgery SPG assures accurate condylar and proximal segment position, eliminating manual "guessing" of centric relation. SPG eliminates the need for intraoperative measurements and peripheral reference sites. The greatest advantage of SPG is the precise 3-D linkage of the virtual plan to the actual osteotomized skeletal segments during surgery.