Two aspects, resulting from this study must be discussed. First, the proposed SSM could be aligned on individual fracture patterns of the midface by using landmarks on easily identifiable bony structures without manual corrections.
Second, by measure the distances between die aligned SSM and the achieved reconstruction, a clinically relevant statement could be said.
In terms of the successful application of SSM, the study proves that the technique is robust enough to virtually capture even complex fracture patterns with the precision and robustness shown in preliminary studies and to provide reconstruction suggestions [5, 13, 14].
Future research in the field of Computer-assisted surgery has to focus on the clinical feasibility of the shown technique. The SSM will be used by the surgeon to plan the fracture reduction preoperatively. Complex planning on the computer can be automated by the SSM, thus reducing on-screen time. The transfer of the SSM-based, virtually planned reduction steps into the operation room can be done by navigational devices or by intraoperative imaging modalities.
In terms of clinical message, the study confirms the known problem in complex midface trauma [9, 18]. Despite the fact that the midface is well aligned and although the classical top-to-bottom or bottom-to-top approach was respected and, in the case of our department, all fracture reductions were controlled by intraoperative CBCT, the midface still needs to be moved forward [8].
In our study, we could demonstrate that an increased fracture complexity still leads to an increased dorsal impaction, despite intraoperative imaging, especially in locations where good visibility is not guaranteed.
A special feature stands out when looking at Fig. 4. Within the orbit, larger deviations are conspicuous. One reason for this may be that in case of complex trauma at our department, the orbital floor is sometimes supplied secondarily.
For the Le Fort III fracture, the medial infraorbital rim and the lateral supraorbital rim, or in NOE fractures, the medial superior and inferior aspects of the orbital rim are more dorsally displaced than areas that can be controlled by direct visibility. The visibility is an important factor, defined by the surgical approach. The coronal approach used in the LeFort III and in one NOE fracture offers a good visibility but increases surgical invasiveness. The impaction of the midface, which is often still present, can be an argument to choose the more invasive approach more often in order to further improve the surgical result in the future.
However, if the number of patients in the individual groups is taken into account, a definitive statement regarding the absolute distance of impaction is only possible to a limited extent.
Nevertheless, to improve patient care, the clinical routine includes the option of virtual planning before the operation, using the established methods of mirroring or registration. However, the mirroring and registration techniques can only be applied to unilateral fractures [19,20,21]. In the case of a bilateral midface fracture, there is still no clinically proven concept of how to virtually restore the midface compartment.