Orthognathic surgery is a widely performed procedure to correct dentofacial deformities. Virtual treatment planning is an important preparation step. One advantage of the use of virtual treatment planning is the possibility to assess the accuracy of orthognathic surgery. In this study, a tool (OrthoGnathicAnalyser 2.0), which allows for quantification of the accuracy of orthognathic surgery, is presented and validated. In the OrthoGnathicAnalyser 2.0 the accuracy of the osseous chin can now be assessed which was not possible in the earlier version of the OrthoGnathicAnalyser. 30 patients who underwent bimaxillary surgery in combination with a genioplasty were selected from three different centers in the Netherlands. A pre-operative (CB)CT scan, virtual treatment planning and postoperative (CB)CT scan were required for assessing the accuracy of bimaxillary surgery. The preoperative and postoperative (CB)CT scans were aligned using voxel-based matching. Furthermore, voxel-based matching was used to align the pre-operative maxilla, mandible and rami towards their postoperative position whereas surface-based matching was used for aligning the pre-operative chin towards the postoperative position. The alignment resulted in a transformation matrix which contained the achieved translations and rotations. The achieved translations and rotations can be compared to planning values of the virtual treatment plan. To study the reproducibility, two independent observers processed all 30 patients to assess the inter-observer variability. One observer processed the patients twice to assess the intra-observer variability. Both the intra- and inter-observer variability showed high ICC values (> 0.92) and low measurement variations (< 0.673±0.684mm and < 0.654±0.824°). The results of this study show that the OrthoGnathicAnalyser 2.0 has an excellent reproducibility for quantification of skeletal movements between two (CB)CT scans.

Restoration of the orbit is the first and most predictable step in the surgical treatment of orbital fractures. Orbital reconstruction is keyhole surgery performed in a confined space. A technology-supported workflow called computer-assisted surgery (CAS) has become the standard for complex orbital traumatology in many hospitals. CAS technology has catalyzed the incorporation of personalized medicine in orbital reconstruction. The complete workflow consists of diagnostics, planning, surgery and evaluation. Advanced diagnostics and virtual surgical planning are techniques utilized in the preoperative phase to optimally prepare for surgery and adapt the treatment to the patient. Further personalization of the treatment is possible if reconstruction is performed with a patient-specific implant and several design options are available to tailor the implant to individual needs. Intraoperatively, visual appraisal is used to assess the obtained implant position. Surgical navigation, intraoperative imaging, and specific PSI design options are able to enhance feedback in the CAS workflow. Evaluation of the surgical result can be performed both qualitatively and quantitatively. Throughout the entire workflow, the concepts of CAS and personalized medicine are intertwined. A combination of the techniques may be applied in order to achieve the most optimal clinical outcome. The goal of this article is to provide a complete overview of the workflow for post-traumatic orbital reconstruction, with an in-depth description of the available personalization and CAS options.

Orbital reconstruction is one of the most complex procedures in maxillofacial surgery. It becomes even more complex when all references to the original anatomy are lost. The purpose of this article is to provide an overview of techniques for complex three- and four-wall orbital reconstructions. Preoperative virtual surgical planning is essential when considering different reconstruction possibilities. The considerations that may lead to different approaches are described, and the advantages and drawbacks of each technique are evaluated. It is recommended to reconstruct solitary three-wall or four-wall orbital defects with multiple patientspecific implants. Optimizations of this treatment protocol are suggested, and their effects on predictability are demonstrated in a case presentation of a four-wall defect reconstruction with multiple patient-specific implants.

Management of orbital fractures has been a topic of controversy for the last 50 years. There is consensus on acute indications for orbital reconstruction and the need for surgery in large fractures with severe functional symptoms or early enophthalmos. Small fractures without complaints will generally be treated without surgery. There is a large grey area between these more obvious cases with no clear consensus about the indication and timing of treatment. It is difficult to predict which of the symptoms (diplopia and limited motility) will resolve spontaneously, and no clear predictors for the development of enophthalmos exist. This chapter describes the relevance of clinical symptoms and considerations for conservative or surgical treatment, based on the latest scientific evidence. A well-designed and generally accepted clinical protocol for orbital fractures ensures a uniform treatment approach, cooperation between different specialities, and adequate outcome evaluation. This facilitates the clinical decision-making and optimisation of the treatment.

Accurate registration is vital to transfer the virtual surgical plan during surgery. This study's goal was to present and clinically validate a virtual splint registration workflow. Ten dentate patients requiring revision surgery were included. Specific inclusion criterion for this study was the presence of at least two osteosynthesis screws on the orbital rim from a previous surgery. Dedicated orthognathic surgery software was used to fuse the maxillary dental scan with the computed tomography and generate a dental splint, which was imported into the navigation software and augmented with fiducial markers. Registration points were indicated virtually and the augmented splint was three-dimensionally printed. Intraoperatively, the splint was fitted on the maxillary dentition and the fiducial markers were used for registration. Accuracy of the registration procedure was quantified by calculating the difference between the landmarks acquired by indicating the pre-existing osteosynthesis material with the navigation pointer and in the virtual planning software. After acquisition of the landmarks, the screws were removed and surgery proceeded according to plan. A median target registration error of 1.53 mm was found. The advantages of the virtual splint registration workflow are that it does not require extensive computer-aided design skills or repeated preoperative imaging, and is non-invasive.