Biomedical subjects

F Wanschitz

Publications and source records attributed to F Wanschitz.

10 recordsLinked to original sources

PubMed2005

Basic research and 12 years of clinical experience in computer-assisted navigation technology: a review.

Computer-aided surgical navigation technology is commonly used in craniomaxillofacial surgery. It offers substantial improvement regarding esthetic and functional aspects in a range of surgical procedures. Based on augmented reality principles, where the real operative site is merged with computer generated graphic information, computer-aided navigation systems were employed, among other procedures, in dental implantology, arthroscopy of the temporomandibular joint, osteotomies, distraction osteogenesis, image guided biopsies and removals of foreign bodies. The decision to perform a procedure with or without computer-aided intraoperative navigation depends on the expected benefit to the procedure as well as on the technical expenditure necessary to achieve that goal. This paper comprises the experience gained in 12 years of research, development and routine clinical application. One hundred and fifty-eight operations with successful application of surgical navigation technology--divided into five groups--are evaluated regarding the criteria "medical benefit" and "technical expenditure" necessary to perform these procedures. Our results indicate that the medical benefit is likely to outweight the expenditure of technology with few exceptions (calvaria transplant, resection of the temporal bone, reconstruction of the orbital floor). Especially in dental implantology, specialized software reduces time and additional costs necessary to plan and perform procedures with computer-aided surgical navigation.

Computer Graphics↗

PubMed2001

Principles of computer-assisted arthroscopy of the temporomandibular joint with optoelectronic tracking technology.

PURPOSE: This preliminary clinical study evaluated the applicability, accuracy, and benefits of computer-assisted arthroscopy of the temporomandibular joint (TMJ) with optoelectronic tracking technology. MATERIALS AND METHODS: A hybrid of reality and virtual reality is built as a composite-reality environment by extracting 3-dimensional anatomical structures through use of computed tomography, magnetic resonance imaging, radiography, and other types of imaging procedures commonly used in clinical praxis. These various independent sources of imaging data of a particular patient can be combined with and complemented by complex graphic simulations. Intraoperatively they are merged with online position data of surgical instruments inside the patient's TMJ. This hybrid model of detailed anatomical structures, guidelines, and real-time instrument positions allows the surgeon to accurately plan the arthroscopic intervention as well as to navigate effectively intraoperatively. RESULTS: In the first 10 cases of computer-assisted TMJ arthroscopy, composite reality environment technology permitted the online visualization of TMJ structures, puncture sites, instrument positions, and virtual pathways in relation to anatomical landmarks with high spatial accuracy (minimum, 0.0 mm; maximum, 2.5 mm; mean, 1.4 mm; SD, 0.6 mm) and high temporal resolution (100 ms). Past, present, and possible future instrument positions can be displayed. The application of computer-assisted arthroscopy caused little immobility for either surgeon or patient. CONCLUSION: Even experienced surgeons profit from improved precision in the handling of the arthroscope; thus this technology was found to be particularly useful in degenerative temporomandibular disorders and for triangulation procedures.

Arthroscopes↗

PubMed2001

Placement of endosteal implants in the zygoma after maxillectomy: a Cadaver study using surgical navigation.

Endosteal implants facilitate obturator prosthesis fixation in tumor patients after maxillectomy. Previous clinical studies have shown, however, that the survival of implants placed into available bone after maxillectomy is generally poor. Nevertheless, implants positioned optimally in residual zygomatic bone provide superior stability from a biomechanical point of view. In a pilot study, the authors assessed the precision of VISIT, a computer-aided surgical navigation system dedicated to the placement of endosteal implants in the maxillofacial area. Five cadaver specimens underwent hemimaxillectomy. The cadaver head was matched to a preoperative high-resolution computed tomograph by using implanted surgical microscrews as fiducial markers. The position of a surgical drill relative to the cadaver head was determined with an optical tracking system. Implants were placed into the zygomatic arch, where maximum bone volume was available. The results were assessed using tests for localization accuracy and postoperative computed tomographic scans of the cadaver specimens. The localization accuracy of landmarks on the bony skull was 0.6 +/- 0.3 mm (average +/- SD), as determined with a 5-df pointer probe; the localization accuracy of the tip of the implant burr was 1.7 +/- 0.4 mm. The accuracy of the implant position compared with the planned position was 1.3 +/- 0.8 mm for the external perforation of the zygoma and 1.7 +/-1.3 mm for the internal perforation. Eight of 10 implants were inserted with maximal contact to surrounding bone, and two implants were located unfavorably. Reliable placement of implants in this region is difficult to achieve. The technique described in this article may be very helpful in the management of patients after maxillary resection with poor support for obturator prostheses.

Cadaver↗

PubMed1999

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 patient's 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.

Adult↗

PubMed1999

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.

Adolescent↗

PubMed1999

Histomorphologic findings on human bone samples six months after bone augmentation of the maxillary sinus with Algipore.

Sinus grafting, a popular and standard treatment for maxillary atrophy, uses a variety of grafting materials. In this study, specimens obtained 6 months after sinus grafting with Algipore were evaluated under light microscopy and showed osseoformation, xenograft degradation, and bone ingrowth into particles. Osteoblastic cells were embedded in the intracorpuscular bone matrix, which indicated that xenograft particles are an osseoconductive scaffold and stimulate matrix deposition. Acute inflammatory responses after insertion of Algipore did not occur. Particles were degraded during physiologic bone remodeling, and newly formed bone gradually replaced resorbed biomaterial.

Bone Substitutes↗

PubMed1998

Calibration of tracking systems in a surgical environment.

The purpose of this paper was to assess to what extent an optical tracking system (OTS) used for position determination in computer-aided surgery (CAS) can be enhanced by combining it with a direct current (dc) driven electromagnetic tracking system (EMTS). The main advantage of the EMTS is the fact that it is not dependent on a free line-of-sight. Unfortunately, the accuracy of the EMTS is highly affected by nearby ferromagnetic materials. We have explored to what extent the influence of the metallic equipment in the operating room (OR) can be compensated by collecting precise information on the nonlinear local error in the EMTS by using the OTS for setting up a calibration look-up table. After calibration of the EMTS and registration of the sensor systems in the OR we have found the average euclidean deviation in position readings between the dc tracker and the OTS reduced from 2.9+/-1.0 mm to 2.1+/-0.8 mm within a half-sphere of 530-mm radius around the magnetic field emitter. Furthermore we have found the calibration to be stable after re-registration of the sensors under varying conditions such as different heights of the OR table and varying positions of the OR equipment over a longer time interval. These results encourage the further development of a hybrid magnetooptical tracker for computer-aided surgery where the electromagnetic tracker acts as an auxiliary source of position information for the optical system. Strategies for enhancing the reliability of the proposed hybrid magnetooptic tracker by detecting artifacts induced by mobile ferromagnetic objects such as surgical tools are discussed.

Calibration↗

PubMed1998

Systematic distortions in magnetic position digitizers.

Medical devices equipped with position sensors enable applications like image guided surgical interventions, reconstruction of three-dimensional 3D ultrasound (US) images, and virtual or augmented reality systems. The acquisition of three-dimensional position data in real time is one of the key technologies in this field. The systematic distortions induced by various metals, surgical tools, and US scan probes in different commercial electromagnetic tracking systems were assessed in the presented work. A precise nonmetallic six degree-of-freedom measurement rack was built that allowed a quantitative comparison of different electromagnetic trackers. Also, their performance in the presence of large metallic structures was quantified in a phantom study on an acrylic skull model in an operating room (OR). The trackers used were alternating current (ac) and direct current (dc) based systems. The ac trackers were, on average, distorted by 0.7 mm and 0.5 degree by metallic objects positioned at a distance greater than 120 mm between the geometrical center of the sample and the sensor. In the OR environment, the ac system exhibits mean errors of 3.2 +/- 2.4 mm and 2.9 degrees +/- 1.9 degrees. The dc trackers are more sensitive to distortions caused by ferromagnetic materials (averaged value: 1.6 mm and 0.5 degree beyond a distance of 120 mm). The dc tracker shows no distortions from other conductive materials but was less accurate in the OR environment (typical error: 6.4 +/- 2.5 mm and 4.9 degrees +/- 2.0 degrees). At distances smaller than approximately 100 mm between sample and sensor error increases quickly. It is also apparent from our measurements that the influence of US scan probes is governed by their shielding material. The results show that surgical instruments not containing conductive material are to be preferred when using an ac tracker. Nonferromagnetic instruments should be used with dc trackers. Static distortions caused by the OR environment have to be compensated by precise calibration methods.

Acrylates↗

PubMed1997

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.

Computer Graphics↗

PubMed1997

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 surgeon's 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.

Adult↗