On Virtual Surgical Planning in Cranio-Maxillofacial Surgery

Sammanfattning: The complex three-dimensional (3D) anatomy of the cranio-maxillofacial (CMF) region makes surgery a challenging task. Virtual surgical planning (VSP) has the potential to increase accuracy, reproducibility and shorten operation time. Key challenges in VSP are to accurately separate, or segment, certain structures of interest, such as the orbit, from the rest of the image, as well as to create an accurate 3D model of the facial bones and dentition for orthognathic surgery planning. The time required for planning and fabrication of guides for trauma surgery is another challenge. The overall aim of this thesis was to develop and evaluate new virtual planning tools for CMF-surgery and to investigate their usefulness. Study I, II discuss and evaluate image fusion of CT/CBCT and intraoral scanning for orthognathic surgery. A method for virtual bite registration in centric relation (CR) was also proposed. The workflow has the potential to eliminate traditional laboratory work, and may facilitate 3D computer-assisted-planning in orthognathic surgery. Study III deals with orbit segmentation and presents a semi-automatic method, using a deformable model tracing the inside of the orbit via haptic 3D interaction. The method was validated in retrospective unilateral orbital fracture cases. The fractured orbits were compared to the intact side by volume and shape analyses. The method showed high accuracy, precision, time-efficiency and thereby potential to be a powerful tool for planning and evaluating reconstruction of orbital fractures. Study IV evaluates an in-house haptic-assisted VSP system for complex mandibular fractures on a series of retrospective cases and an artificial case. The system showed high precision and time-efficiency, but relatively low accuracy. This study proposes a novel, fast and user-friendly way of integrating VSP into planning mandible trauma surgery and could help in reducing operating time and increase accuracy. Study V is a systematic review and meta-analysis studying potential time benefits using VSP in CMF surgery. The study suggests that VSP shortens the operating time and ischemia time for reconstructive surgery. VSP also appears to shorten the preoperative planning time for orthognathic surgery.