W. Millesi

Computer-aided navigation in secondary reconstruction of post-traumatic deformities of the zygoma

Augmented reality technology was used in 5 patients for secondary reconstruction of post-traumatic unilateral deformities of the zygomaticomaxillary complex. Three electromagnetic sensors interfaced to a computer-aided navigation system (ARTMA Biomedical Inc.) were utilized. The computer navigation procedure was planned by drawing graphic lines on the CT scan at the level of the zygomatic arch, representing the outer surface of the zygoma. The desired position of the displaced zygoma was planned by mirroring from the healthy side, using a virtual mid-sagittal plane. These virtual graphics were presented intraoperatively on a TV monitor and also on the surgeons see-through head-mounted display. Correct reduction was assumed when the virtual line representing the position of the zygoma before the osteotomy reached the virtual line defined preoperatively as the desired position. The advantages of the technique presented are that a complete exposure of the zygomatic bone is no longer necessary, and coronal and subciliary incisions may be avoided unless enophthalmos correction has to be carried out, which was in fact necessary in 2 patients. The results of zygomatic reconstruction have been satisfactory in all 5 patients.

Positioning of dental implants using computer-aided navigation and an optical tracking system: case report and presentation of a new method

A navigation system for computer-aided surgery (Virtual Patient System, VPS) has been described in previous studies for different indications in oral and maxillofacial surgery. The aim of the system is the intraoperative transfer of preoperative planning on radiographs or CT scans on the patient, in real-time, and independent of the position of the patients head. Until now an electromagnetic tracking system has been used for intra-operative position measurement. For placement of dental implants, the electromagnetic tracking system is not suitable since the motor of the implant drill leads to a considerable distortion of the magnetic field, thus direct visualization of drilling the implant socket was not possible. To overcome this problem, an optical tracking system which is not disturbed by conductive materials was integrated in the VPS system. The first patient operated on with this system had a posttraumatic loss of the upper incisors; three implants have been placed according to the prosthetic axis previously planned on radiographs and CT scans. The experience gained in this intervention led to the conclusion that computer-aided surgery provides a valuable tool in implant dentistry.

Posterior ischemic optic neuropathy following bilateral radical neck dissection

A patient is presented with posterior ischemic optic neuropathy (PION) after bilateral radical neck dissection, probably caused by hemodynamic hypotension, combined with other factors. A postmortem histologic study of the optic nerve was performed to analyze the pathogenic mechanism of blindness. To prevent this complication, one should favor a two-stage procedure, avoiding drug-induced hypotension, overtransfusion, and anemia. During the postoperative period, visual acuity should be monitored regularly, and proper positioning of the patients head is necessary.

Computer-aided surgery in distraction osteogenesis of the maxilla and mandible

When using unidirectional intraoral distraction devices, it is desirable to be able to determine the final position of the bone fragment after the distraction procedure. However, additional constraining forces from adjacent tissues render the prediction of the distraction direction difficult. We have utilised computer-aided surgery in three patients for intraoperative control of the distraction direction. In one cleft palate patient, suffering from maxillary hypoplasia and anterior open bite, a modified Le Fort I osteotomy and maxillary distraction was performed. Despite a ventrocaudal position of the distraction device, intraoperative computer visualisation showed an unfavourable caudal vector of distraction without any anterior movement. The final result confirmed the direction indicated by the computer. Maxillary advancement remained insufficient. In two patients suffering from mandibular hypoplasia, intraoperative assessment revealed a favourable direction of distraction. The distraction procedure led to a satisfactory result in both cases. Computer-aided surgery is helpful in assessing the vector of distraction intraoperatively, making the result of the distraction procedure more predictable and allowing instant correction by adequate reapplication of the device.

Reconstruction of the floor of the mouth with a fascial radial forearm flap, prelaminated with autologous mucosa

To circumvent the disadvantages of extraoral skin within the oral cavity and to cover mucosal defects by mucosa, we successfully prelaminated the radial forearm flap by insertion of buccal mucosa in ten patients. In a first-step operation, free grafts of buccal mucosa were fixed to the forearm fascia and covered with an alloplastic sheet, separating the mucosa grafts and the dissected fascia between and around the grafts from the overlaying subcutaneous tissue. The dimension of the alloplastic sheet in the subcutaneous pocket was chosen according to the size of the desired flap. Underneath the alloplastic sheet, the mucosal grafts merged and the mucosal surface increased by advancing of epithelial cells under in vivo culture conditions. After two months, mucosal prelamination of the distal radial forearm fascia had led to thin, pliable and resistant fasciomucosal flaps with a mucosal surface up to 7x4 cm, allowing physiological intraoral reconstruction. The preservation of skin and subcutaneous tissue of the forearm also enabled primary wound closure, reducing donor-site morbidity.

Remote stereotactic visualization for image-guided surgery: technical innovation.

Additional data from imaging sources using computer navigation assistance enables virtual visualization of anatomical structures in three dimensions for stereotactic navigation during an operation. Recent developments in communication technology enable the broadcasting not only of video data, but also of stereotactic navigation data via the network. By telepresence/teleconsulting, the composite images and overlapping graphics (instrument, target structure, landmark, contour) can be seen in connected clinics, with the possibility of interactive graphic assistance. In cranio-maxillofacial surgery, the first surgical teleconsultation in real time via telecommunication of stereotactic data was performed in August 1996. A patient suffering from a post-traumatic deformity following multiple comminuted midface fractures was re-osteotomized with the aid of image-guided surgery using teleconsultation: the intraoperative position achieved could be discussed with different surgeons with regard to symmetry, hard/soft tissue relationships and occlusal details, with the possibility of on-screen planning interaction and real time evaluation of the results, over a distance of 500 km.

Über das Risiko der Mitresektion der Arteria carotis communis bzw. interna bei der Exstirpation von Tumoren im maxillo-facialen Bereich

Im Zeitraum von 1963 bis 1988 wurde an der hiesigen Klinik bei 71 Patienten (60 Manner, 11 Frauen) mit einem durchschnittlichen Alter von 49 Jahren (maximum 80 a, minimum 23 a) die Arteria carotis interna (ACI) ligiert.

Osteolysen im Kieferbereich als erster Hinweis auf einen primären Hyperparathyreoidismus

ZusammenfassungGrundlagen: Bei primärem Hyperparathyreoidismus (PHPT) werden osteolytische Veränderungen im Mund-, Kiefer- und Gesichtsbereich im Gegensatz zum übrigen Skelettsystem selten beobachtet, können aber den ersten klinischen Hinweis auf die endokrine Erkrankung darstellen. Aus diesem Grund ist die Kenntnis dieser Veränderungen, ihre differentialdiagnostische Abklärung und Therapie für den Zahnarzt und im besonderen für den Mund-, Kiefer- und Gesichtschirurgen von großer Bedeutung,n Methodik: 11 von 388 Patienten mit histologisch verifiziertem PHPT zeigten ossäre Manifestationen im Mund-, Kiefer- und Gesichtsbereich; bei 7 Patienten waren die diagnostischen und therapeutischen Details komplett. In einer retrospektiven Untersuchung wurden die Symptomatologie, die Diagnose und die Behandlung der osteolytischen Läsionen analysiert.n Ergebnisse: Bei 2 Patienten wurde der PHPT als Grunderkrankung unverzüglich erkannt. Beiden Patienten wurde eine entsprechende Therapie zuteil, nämlich eine chirurgische Behandlung des PHPT und nur nach einer Beobachtungszeit von mehreren Monaten die chirurgische Abtragung persistierender Tumoren. Bei 5 Patienten war die korrekte Diagnose des PHPT um durchschnittlich mehr als 6 Monate verzögert. Zuvor wurden die Osteolysen einer mund-, kiefer- und gesichtschirurgischen Therapie zugeführt. Zur Entfernung der Läsionen (Riesenzellgranulome) wurden 2 Existirpationen und 3 Kieferteilresektionen durchgeführt.n Schlußfolgerungen: Retrospektiv mußte diese Therapie, vor allem in Anbetracht der Kieferteilresektionen, als zu radikal erscheinen. Bei Patienten mit Riesenzellgranulomen oderähnlichen Läsionen im Mund-, Kiefer- und Gesichtsbereich muß das Vorliegen eines PHPT als Grundkrankheit durch Serumkalziumbestimmung ausgeschlossen werden.SummaryBackground: In primary hyperparathyroidism (PHPT) osteolytic lesions in the oral and maxillofacial region are rare symptoms, compared to lesions in the outer skeletal system. Nevertheless, they could be the first clinical manifestation of the metabolic disease. Therefore the knowledge of differential diagnosis and therapy is of great importance for the dentist, and especially the oral and maxillofacial surgeon.n Methods: 11 out of 388 patients with histiologically verified PHPT showed osseous manifestations in the jaws; a complete analysis of diagnostic and therapeutic details was achieved in 7 patients. In a retrospective study, the symptomatology, diagnosis and treatment of the osteolytic lesions are reviewed.n Results: In only 2 patients PHPT was immediately recognized as the primary disease. Both patients recieved adequate therapy (surgical treatment of the PHPT and after a period of several months removal of the tumor of the jaws by conservative surgery). In 5 patients, correct diagnosis of PHPT was delayed by an average time of more than 6 months. Formerly, maxillofacial surgery was carried out in all cases. To remove the tumors (giant cell granulomas), 2 exstirpations and 3 partial resections of the jaws were performed.n Conclusions: Retrospectively, surgery was too radical in these patients. We request PHPT to be excluded by determining serum calcium in all patients with giant cell granulomas or similar lesions in the jaws.