Marc Metzger

Recently, advances in imaging techniques for diagnostics and associated technologies have led to an improved preoperative planning for craniomaxillofacial surgeons. In particular, the application of navigation-aided procedures for orbital reconstruction has proved to be essential. Preforming orbital implants for orbital floor reconstruction and determining overcorrection with regard to the orbital floor reconstruction could be achieved using preoperative planning. It has turned out that the computation of soft tissue cuts is an essential prerequisite for the realistic placement of implants. We propose a simulation framework that allows for the static and dynamic cutting of soft and hard tissue representations. The framework comprises components to model tissue deformation, cutting of tissue and interaction between the physical bodies. Furthermore, volume and surface representations are decoupled which allows for an independent scaling in the complexity of the representations and, therefore, in the simulation and visualisation performance. In contrast to many other cutting approaches, our algorithm handles both representations simultaneously. The framework is used to simulate the realistic insertion of a preformed orbital implant model through the soft tissue cut and the prediction of the postoperative eye bulb position. Experiments show that the framework can be used to determine overcorrection and to preform orbital implants.

Three-dimensional reconstruction of the orbital floor is a key procedure in primary or secondary orbital deformity. A new procedure for individually bending and preforming implants preoperatively for the reconstruction of orbital fractures is presented. By using diagnostic computed tomographic scan data, the topography of the orbital floor and wall structures can be recalculated. After mirroring the unaffected side onto the affected side, the defect can be reconstructed virtually. Data of the individual virtual model of the orbital cavity are sent to a template machine that reproduces the surface of the orbital floor and medial walls automatically. A titanium mesh can then be adjusted preoperatively for exact three-dimensional reconstruction. Twelve patients with orbital fractures were treated using individually preformed titanium implants. All patients treated with this procedure showed normal eye mobility and function after primary reconstruction. The accuracy of the preformed implants lies in the range of 1 mm. This procedure offers an individual anatomical reconstruction of the orbital cavity true to original, especially when the deep orbital cone is affected. Navigation-aided procedures guarantee intraoperatively an exact placement of the preformed mesh even for precise reconstruction of extensive orbital defects.

A new concept was developed based on the experience gained in dental rehabilitation with implantation in the oral maxillofacial region. Despite the use of cooling systems, mechanically rotating instruments may damage the surrounding tissue due to the frictional heat generated. An alternative approach for bone removal is laser application. A preoperative plan was prepared. Laser ablation was performed in accordance with the data set on bovine bone using a navigation system. This new concept allows precise bone removal and adjustment of the laser power according to the preoperative plan. The power of the laser automatically decreases as it approaches the border of the planned cavity or important anatomical structures. The advantage of this approach is precise and safe bone removal without damaging the bone by frictional heat.

Nasolabial cysts are usually unilateral and are quite rare, while bilateral cysts are even rarer. Our report concerns a 48-year-old female with bilateral nasolabial cysts. After many years of misdiagnosis she was finally referred to our clinic with a subnasal swelling of unknown origin. Evaluation of the patient's medical history, clinical examination and of a previous CT scan led to the diagnosis of a nasolabial cyst, which was later confirmed by histological examination. Treatment involved the surgical excision. A complete surgical excision is recommended using a sublabial approach as the treatment of choice, although transnasal endoscopic marsupialization seems to be a simple and effective alternative. It has been shown that after successful marsupialization, the nasolabial cyst is converted to an air-containing paranasal sinus.

To facilitate a diagnosis of a lipoma, specific imaging is needed such as ultrasound or magnetic resonance imaging (MRI). Two male patients exhibiting a soft tissue tumor in the salivary gland area were examined using sonography and MRI. Final diagnosis was identified by excision biopsy. Ultrasound showed a hypoechoic, feathered, mostly ovoid structure. Color Doppler sonography does not detect any signals besides in cases of angiolipoma. This is accompanied by vessels and does not show the typical feathered structure. With MRI, it is possible to confirm the diagnosis by visualization of fat-equivalent intensity values. Diagnosing soft tissue swelling in the salivary gland, clinical examination and an ultrasound or MRI scan are recommended.

Intraosseous malformations are rarely reported in the maxillofacial area. Because of bone growing processes, it is still a challenge to find the appropriate way to treat this disorder. The gold standard treatment for arteriovenous malformation is an endovascular embolization, combined with surgery. The case of a 14-year-old boy with arteriovenous malformation of the mandible was followed during a period of 8 years. Several embolizations and surgical interventions were required, culminating in bone reconstruction with a fibula graft to achieve normal mandibular form and function. There was no recurrence of the malformation during the follow-up period. To obtain stable results in the case of intraosseous arteriovenous malformations of the mandible, a combination of embolization and surgery is recommended. Superselective embolization is possible in an emergency case.

The aim of this study was to evaluate the advantage of computer-assisted analysis of the oral brush biopsy compared with synchronous scalpel biopsy in the early detection of oral lesions. In this prospective, randomized, controlled study, brush and scalpel biopsies were performed on 75 patients. Six patients had to be excluded due to inadequate results, and 43 were shown to have dysplastic epithelium, 15 carcinoma, and 11 suspicious lesions. Therefore, the sensitivity for the detection of abnormal cells by means of OralCDx was 52%, specificity 29%, and the positive predictive value 63%. According to our results, the use of oral brush biopsy as a standardized, minimally invasive method of screening oral lesions should be reconsidered.

To compare the accuracy of 3 computer-aided surgery systems for maxillofacial reconstruction. Evaluation of 3 computer-aided surgery systems: StealthStation, VectorVision, and Voxim. The University of California, Davis, Department of Otolaryngology computer-aided surgery laboratory. Four fresh cadaveric heads. Mean target registration error. The StealthStation was the most accurate (mean [SD] target registration error, 1.00 [0.04] mm), followed by VectorVision (1.13 [0.05] mm) and then Voxim (1.34 [0.04] mm). All values met statistical significance (P < .05). Measurable accuracy differences were found among the navigation systems evaluated. The StealthStation was the most accurate. However, the differences are small, and the clinical significance for maxillofacial reconstruction is negligible.

The removal of sphenoid bone parts was performed by the admitting neurosurgeons on a patient who presented an optic nerve compression syndrome. Beside the orbital trauma, an extensive midfacial trauma was sustained with dislocated multifractures of the zygomatic complex. In a secondary procedure, the orbital cavity was reconstructed successfully using 3 different methods of computer-assisted surgery. First, the reconstruction of the zygomatic complex was controlled intraoperatively by a virtual model obtained by mirroring the unaffected side to the affected side. Second, extracorporeal bone parts were virtually preoperatively relocated and orientated. The reconstruction of the orbital cavity by the insertion of these bony fragments was performed intraoperatively as planned after the zygomatic complex reconstruction. Third, the virtual reconstruction of the orbital floor was performed using preoperatively individually bent and preformed orbital titanium mesh. Combinations of these methods demonstrate the practical and high value of computer-assisted surgery in complex reconstructive craniofacial surgery.

The X-linked deafness syndrome is characterised by a complex labyrinth malformation with a shortened cochlea with missing bony separation between the cochlea and internal auditory canal and a deviant route of the facial nerve. Cochlear implant surgery in this malformation may be complicated by an unintended electrode insertion into the internal auditory canal. The authors report a new surgical approach: intraoperative three dimensional-volume tomography (3D-VT)-based navigation and direct intraoperative control by 3D-VT. The navigation dataset was based on intraoperative 3D-VT after performing the mastoidectomy and posterior tympanotomy. The cochleostomy was then performed under navigation control. After insertion, the electrode position was directly visualised by 3D-VT. On the basis of the reconstruction results, the electrode position was corrected and an intracochlear insertion resulted. Cochlear implantation in X-linked deafness malformation can be facilitated using intraoperative 3D-VT-assisted navigation and intraoperative 3D-VT control of the electrode position. This approach enhances the precision of navigation and reduces the risk of improper electrode placement and additional surgery in complex malformations. Copyright © 2009 John Wiley & Sons, Ltd.