A preoperative planning system for oral implant surgery was developed which takes as input computed tomographies (CT's) of the jaws. Two-dimensional (2-D) reslices of these axial CT slices orthogonal to a curve following the jaw arch are computed and shown together with three-dimensional (3-D) surface rendered models of the bone and computer-aided design (CAD)-like implant models. A technique is developed for scanning and visualizing an eventual existing removable prosthesis together with the bone structures. Evaluation of the planning done with the system shows a difference between 2-D and 3-D planning methods. Validation studies measure the benefits of the 3-D approach by comparing plans made in 2-D mode only with those further adjusted using the full 3-D visualization capabilities of the system. The benefits of a 3-D approach are then evident where a prosthesis is involved in the planning. For the majority of the patients, clinically important adjustments and optimizations to the 2-D plans are made once the 3-D visualization is enabled, effectively resulting in a better plan. The alterations are related to bone quality and quantity (p < 0.05), biomechanics (p < 0.005), and esthetics (p < 0.005), and are so obvious that the 3-D plan stands out clearly (p < 0.005). The improvements often avoid complications such as mandibular nerve damage, sinus perforations, fenestrations, or dehiscences.

Although the actual experience is limited, the idea of using a template with drill guide might simplify and shorten the surgical act and at the same time enhance the accuracy of C1-C2 transarticular screw positioning.

Abstract. Posterior transarticular spine fusion is a surgical procedure used to stabilize the cervical bodies C1 and C2. Currently, spine screws are used most frequently, according to the procedure of Magerl. As the anatomy is rather complex and the view is limited, this procedure has a high risk factor. Thus we present and validate a planning system for cervical screw insertion based on preoperative CT imaging. It allows a neurosurgeon to interactively determine the desired position of the cervical screws, based on appropriate and in real-time calculated reslices through the preoperative CT data. Guided by this information, a personalized mechanical drill guide is produced. The system is validated by five cadaver experiments. Based on the preoperative planning, screws are inserted through the drill guide. A semi-automatic technique is used to extract the screw locations from the postoperative images. The deviations of the axes of the planned and the inserted screws are determined in this way. We have observed that the drill guides are not yet stable enough to cope with the drilling forces that they are subjected to. As a result, they tend to displace. However, most of the inserted screws were judged to be adequately placed. No vascular compromise nor invasion of the spinal canal was observed.