Computer-assisted three-dimensional surgical planning: 3D virtual articulator: technical note.

This study presents a computer-assisted planning system for dysgnathia treatment. It describes the process of information gathering using a virtual articulator and how the splints are constructed for orthognathic surgery. The deviation of the virtually planned splints is shown in six cases on the basis of conventionally planned cases. In all cases the plaster models were prepared and scanned using a 3D laser scanner. Successive lateral and posterior-anterior cephalometric images were used for reconstruction before surgery. By identifying specific points on the X-rays and marking them on the virtual models, it was possible to enhance the 2D images to create a realistic 3D environment and to perform virtual repositioning of the jaw. A hexapod was used to transfer the virtual planning to the real splints. Preliminary results showed that conventional repositioning could be replicated using the virtual articulator.

[Malposition of the orbita from the surgical point of view]. / Fehlstellung der Orbita aus chirurgischer Sicht.

The individual appearance of a person is mainly determined by the head and, in particular, by the eyes. The orbita exerts a decisive influence on the harmony of the face. Anomalies of the neuro- and viscerocranium have varying impact on the orbits as well as on the structures of the bulb, resulting in dysmorphia or dystopia of the orbits which, in turn, lead to corresponding functional impairments. Premature craniosynostoses, representing the most frequent craniofacial malformation, may have an influence on the region of the orbita in different manner. Symptomatics depend on localisation, number and severity of the synostoses. Main symptoms are uni- or bilateral exophthalmus as well as hypo- or hypertelorism. The deformation of the patients is not only a "cosmetic problem" but often also a barrier to social communication with all consequent impairments of the patient's development. Sometimes it is even the only reason for a mental retardation of the child. Apart from augmentation of the intracranial volume, the main aim of corrective surgery, therefore, is normalisation of the patient's appearance. There are various surgical procedures for operative correction. However, therapy is not only directed towards the orbita but has to be integrated into the overall concept for therapy of the disease. In this article we show the surgical approaches for the treatment of orbital malformations caused by various craniofacial malformations, using clinical examples.

Piezosurgery--a new safe technique in cranial osteoplasty?

All surgical interventions on the neurocranium bear the risk of injury of the dura mater and development of a cerebrospinal fluid fistula. Therefore, despite careful preparation, damage to the dura mater cannot always be omitted. Especially after surgery and in patients with increased intracranial pressure (craniosynostoses) there is a high risk of perforating the dura. In this article a new surgical technique for osteotomy (Piezosurgery) that avoids perforation of the dura is presented. Ultrasonic microvibrations allow a selective cut of only mineralized structures without damage to the soft tissue. Even in case of accidental contact the dura remains undamaged. This advantage is also useful for bone splitting, to separate the tabula externa from the tabula interna in situ, without any risk of dura perforation even in case of the very thin bones in an infantile skull. The present work shows the applicability of piezoelectric surgery in high-risk patients after osteotomy, avoiding perforation of the dura mater.

Robot-assisted craniotomy.

In the Special Research Centre 414 of the German Research Funding (DFG, Bonn) a system for robot-assisted cranial surgery was developed. It is designed for the accurate and safe execution of craniotomies and repositioning of bone pieces. The system is intended for use in the surgical therapy of craniosynostosis. Preoperatively, CT imaging is performed. In a computerized planning system the position and shape of the intended craniotomy is intuitively planned on a virtual model of the patient's skull. Intraoperatively, after conventional removal of the covering soft tissue, the robot performs the craniotomy autonomously. Extensive testing in phantom studies and animal tests confirmed the reliability and accuracy of the system. A thorough risk analysis of the system was performed. In this paper, the first clinical use of the system on a patient is described and the clinical importance is discussed.

[Surgery of craniofacial deformities]. / Chirurgie kraniofazialer Fehlbildungen.

Most craniofacial abnormalities are craniosynostoses due to premature fusion of one or more craniofacial sutures. The typical cranial deformities result from growth inhibition perpendicular to the affected sutures. Functional impairment is caused either directly by the pathological growth pattern or indirectly by the increased intracranial pressure. Craniosynostosis is frequently accompanied by dysmorphia or dystopia of the orbits, resulting in possible functional problems. The indications for operation are to increase the intracranial volume and to correct aesthetic impairments. The planning of the surgical procedures has to consider the orbital problems. This review describes the different disease patterns of premature craniosynostosis and specific surgical approaches for their correction.

Standardized evaluation and documentation of findings in patients with craniosynostosis.

Surgical correction of craniosynostosis is usually performed according to standard procedures. However, a standard for clinical examination and report of findings for patients with craniosynostosis does not exist as yet. To compare findings from different hospitals, a documentation system was developed by a national craniosynostosis group. This system comprises a two-page document, clinical photographs, radiographs, CT scans, anthropometric measurements and molecular genetic findings. Data from craniosynostosis patients collected from participating hospitals are stored in a database, which facilitates online access. The documentation system was developed in cooperation with the group during 3 years since 1996. It was evaluated as being practicable and reliable and enables a comparability of findings reported in different hospitals. Molecular genetic analysis was found to support the investigation of patients with craniosynostosis and should therefore be integrated in the clinical evaluation.

3D norm data: the first step towards semiautomatic virtual craniofacial surgery.

When planning craniofacial surgical interventions, the ideal appearance of the patient is very important. The final appearance should be as close as possible to that which the patient would have if he/she were without defects. Our first step towards achieving this is to build a database containing sets of three-dimensional CT images that allows for comparison of the shape of a patient with defects to the typical shape of an age- and sex-matched "average" person without defects. We started to collect CT data from patients without pathologies and, in co-operation with two radiology institutes (in Mannheim and Heidelberg), over 100 CT data sets have now been collected and classified according to age and sex. It is necessary to choose an appropriate statistical method to calculate the norm data from the different data sets. Based on the statistical method, an age- and sex-matched "average" model of the anatomy will be created.