Page 78 - Advanced concepts in orbital wall fractures

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Chapter 4
The plots in Fig. 2 and Fig. 3 illustrate the spread of the implant positions with the 95 % confidence interval in both groups. For all four indicated points, the solid circles are smaller and more centred around the average. This implies that the relative spread of the implant position is smaller in the group with preoperative planning. Mean pitch and roll are negative, and yaw is positive. This might be due to the anatomy of the orbit and pressure of the soft tissue during placement forcing the implant into a certain position. Intrasurgeon repeatability is high for translation, pitch, and roll and average for yaw. Intersurgeon repeatability is high for pitch and yaw and low for translation and roll. This may be explained by the fact that the relative deviation of the implant position is small.
Apart from the improved accuracy of the implant position, the use of virtual planning software on its own holds several other benefits. The software provides diagnostic tools (volumetric analysis, mirroring) and an in-depth overview of the anatomy, its landmarks and the actual defect to prepare for the surgery. The surgeon gains experience due to the virtual reconstruction and the fitting of different implant shapes and sizes. The planning also sets an objective target which enables the surgeon to do a postoperative analysis of the reconstruction. All these benefits make preoperative virtual planning suitable for both educational and research purposes. In severe cases, software tools such as mirroring produce a clear insight in the complexity of the case and it facilitates designing patient-specific implants14,26. It is also believed that it may act as an additional tool in decision-making towards the choice for referral to a specialised, tertiary centre. Preoperative planning software on its own is more affordable and easier to implement in less equipped clinics. If predictability and reliability improve with preoperative virtual planning, then navigation-assisted surgery may not always be necessary. Without navigation, additional expensive hardware is unnecessary, no specific scan protocol with navigation markers is needed, and no skull-fixed navigation receiver needs to be positioned. However, intraoperative control will be lacking without navigation. Postoperative or, rather, intraoperative 3D C-bow imaging will then be the most important evaluation tool for assessing reconstruction quality27,28. The combination of preoperative planning and intraoperative imaging allows the surgeon to fuse the