Wock Hallermann

A New System for Computer-Aided Preoperative Planning and Intraoperative Navigation During Corrective Jaw Surgery

A new system for computer-aided corrective surgery of the jaws has been developed and introduced clinically. It combines three-dimensional (3-D) surgical planning with conventional dental occlusion planning. The developed software allows simulating the surgical correction on virtual 3-D models of the facial skeleton generated from computed tomography (CT) scans. Surgery planning and simulation include dynamic cephalometry, semi-automatic mirroring, interactive cutting of bone and segment repositioning. By coupling the software with a tracking system and with the help of a special registration procedure, we are able to acquire dental occlusion plans from plaster model mounts. Upon completion of the surgical plan, the setup is used to manufacture positioning splints for intraoperative guidance. The system provides further intraoperative assistance with the help of a display showing jaw positions and 3-D positioning guides updated in real time during the surgical procedure. The proposed approach offers the advantages of 3-D visualization and tracking technology without sacrificing long-proven cast-based techniques for dental occlusion evaluation. The system has been applied on one patient. Throughout this procedure, we have experienced improved assessment of pathology, increased precision, and augmented control

Microsurgical reconstruction of the head and neck – Current practice of maxillofacial units in Germany, Austria, and Switzerland

Refinement in microvascular reconstructive techniques over the last 30 years has enabled an increasing number of patients to be rehabilitated for both functional and aesthetic reasons. The purpose of this study was to evaluate different microsurgical practice, including perioperative management, in Germany, Austria, and Switzerland. The DÖSAK collaborative group for Microsurgical Reconstruction developed a detailed questionnaire which was circulated to units in the three countries. The current practice of the departments was evaluated. Thirty-eight questionnaires were completed resulting in a 47.5% response rate. A considerable variation in the number of microsurgical reconstructions per year was noted. In relation to the timing of bony reconstruction, 10 hospitals did reconstructions primarily (26.3%), 19 secondarily (50%) and 9 (23.7%) hospitals used both concepts. In the postoperative course, 15.8% of hospitals use inhibitors of platelet aggregation, most hospitals use low molecular heparin (52.6%) or other heparin products (44.7%). This survey shows variation in the performance, management, and care of microsurgical reconstructions of patients. This is due in part to the microvascular surgeons available in the unit but it is also due to different types of hospitals where various types of care can be performed in these patients needing special perioperative care.

Prediction of dental implant torque with a fast and automatic finite element analysis: a pilot study

OBJECTIVES Despite its importance, implant removal torque can be assessed at present only after implantation. This paper presents a new technique to help clinicians preoperatively evaluate implant stability. STUDY DESIGN Planning software has been combined with an in-house finite element solver. Once the clinician has chosen the implant position on the planner, a finite element analysis automatically calculates the primary stability. The process was designed to be as simple and fast as possible for clinical use. This paper describes application of the method to the prediction of removal torque. A preliminary validation has been performed in both polyurethane foam and sheep bone. RESULTS The predicted torque is quantitatively equivalent to experimental values with correlation coefficients of >0.7 in both materials. CONCLUSIONS This preliminary study is a first step toward the introduction of finite element models in computer-assisted surgery. The fact that the process is fast and automatic makes it suitable for a clinical use.

3D surgical planning and navigation for CMF surgery

In this paper we describe a system for corrective and reconstructive CMF surgery that allows planning of bone segment relocations in 3D and transfer of the goal positions into an intra-operative navigation module, which provides guidance to realize the planned movement. In addition, the pre-operative planning module offers functions of mirroring and allows insertion of distraction devices. We present three clinical cases of CMF surgical procedures planned a posteriori with our application: bimaxillary realignment, involving subcondylar osteotomy of the mandible and LeFort I osteotomy, secondary orbital reconstruction and mandibular reconstruction.