Kurt Schicho

TREATMENT RESULTS OF BISPHOSPHONATE-RELATED OSTEONECROSIS OF THE JAWS

Osteonecrosis of the jaws occurs after the administration of bisphosphonates. An unequivocal treatment strategy is yet to be devised. We assess the treatment of patients with bisphosphonate‐related osteonecrosis of the jaws (BRONJ).

Stability of miniature electromagnetic tracking systems

This study aims at a comparative evaluation of two recently introduced electromagnetic tracking systems under reproducible simulated operating-room (OR) conditions: the recently launched Medtronic StealthStation, Treon-EM and the NDI Aurora. We investigate if and to what extent these systems provide improved performance and stability in the presence of surgical instruments as possible sources of distortions compared with earlier reports on electromagnetic tracking technology. To investigate possible distortions under pseudo-realistic OR conditions, a large Langenbeck hook, a dental drill with its handle and an ultrasonic (US) scanhead are fixed on a special measurement rack at variable distances from the navigation sensor. The position measurements made by the Treon-EM were least affected by the presence of the instruments. The lengths of the mean deviation vectors were 0.21 mm for the Langenbeck hook, 0.23 mm for the drill with handle and 0.56 mm for the US scanhead. The Aurora was influenced by the three sources of distortion to a higher degree. A mean deviation vector of 1.44 mm length was observed in the vicinity of the Langenbeck hook, 0.53 mm length with the drill and 2.37 mm due to the US scanhead. The maximum of the root mean squared error (RMSE) for all coordinates in the presence of the Langenbeck hook was 0.3 mm for the Treon and 2.1 mm for the Aurora; the drill caused a maximum RMSE of 0.2 mm with the Treon and 1.2 mm with the Aurora. In the presence of the US scanhead, the maximum RMSE was 1.4 mm for the Treon and 5.1 mm for the Aurora. The new generation of electromagnetic tracking systems has significantly improved compared to common systems that were available in the middle of the 1990s and has reached a high level of technical development. We conclude that, in general, both systems are suitable for routine clinical application.

Computer simulation and rapid prototyping for the reconstruction of the mandible.

Augmented-reality environments, that is, computer graphics merged with 3-dimensional representations of anatomic regions generated from imaging modalities (mainly computed tomography [CT] and magnetic resonance imaging), have their background in well-known and well-established conventional image-guided surgery, which we can describe as the “first generation of navigation.” 1-3 Although the surgeon is solely supplied with “information,” this technology significantly expands the range of the intraoperatively available information. Nevertheless, it does not provide any kind of haptic feedback, and the transfer of all the computer information is accomplished manually during the treatment of the patient. Technical progress led to the integration of rapid prototyping techniques (3-dimensional stereolithography) in image-guided surgery workflows and therefore can add “haptic” information to the computerbased visualization. Therefore we can call such approaches the “second generation of navigation.” Simulation and planning of surgical interventions by use of stereolithographic models can contribute to the optimization of treatment and can also enhance quality management in craniomaxillofacial surgery, because the specific anatomic situation of each patient can be comprehensively analyzed preoperatively. Navigation technology enables the precise transfer of the

Quantification and clinical relevance of head motion during computed tomography.

Objective:To quantify the 3-dimensional translation and rotation components of head motion during computed tomography and to analyze the influence of such motion on perceptible artifacts and distortion of volume image data sets. Methods:Using high-precision optoelectronic motion-capture technology, changes in patient head position during axial CT scanning were registered in 20 cases and 2 phantoms with a spatial relative resolution better than 0.003 cm. Statistical analysis was performed on a base of 6-dimensional measurement-vectors, each with 3 translation and 3 rotation values. Because of the recording frequency of the tracking system, more than 80,000 values were included in a statistical analysis. Results:All 20 patients had head motion during the CT scanning, with only 4 of 20 patients showing perceptible motion artifacts. The frequency, the extent, and the direction of the movements did not correlate with either the observations made by the radiologic staff or with the patient’s subjective estimation of comfort. Translation movements of the head during CT accounted for a maximum of 0.5 cm and rotations of more than 2° without perceptible motion artifacts. The extent of positional changes of the head was found to correlate with the duration of scanning (Pearson’s correlation coefficient: 0.647 for translation shifts, 0.453 for rotation shifts). The mean direction of head motion could be characterized predominantly as a rotation around the longitudinal axis of the body (xy plane) at a significance level of 0.01. Conclusion:Computed tomography evaluations of the head performed without rigid fixation suffer a spatial distortion of the volume image data sets, caused by interimage motion. The absence of motion artifacts is not correlated with the absence of motion.

Complication rates in the operative treatment of mandibular angle fractures: a 10-year retrospective.

PURPOSE Large-scale studies assessing complication rates and correlation of complications are still missing considering different fracture locations in the mandible. In the present retrospective study, complication rates of mandibular angle fractures treated by open reduction were assessed. MATERIALS AND METHODS Three hundred twenty-two patients (259 men, 63 women) with 335 surgically treated mandibular angle fractures were included in this study. RESULTS Fractures were caused by fights (46.6%), falls (19.2%), traffic accidents (14.6%), sports (11.9%), wisdom tooth removal (7.3%), and 0.9% other causes. Successful treatment occurred in 93.69% of fractures with 1 open reduction and in 6.31% with 2 open reductions. Of surgically treated patients, 71.47% (238) were completely free of complications. A detailed complication correlation matrix is given in the text. Ninety-five fractures treated with 1 miniplate, 170 with 2 miniplates, and 70 with other osteosynthesis concepts were compared regarding osteosynthesis failure and pseudarthrosis. CONCLUSION Similar osteosynthesis failure rates were shown for 1 miniplate and 2 miniplates.

Accuracy of craniofacial measurements: computed tomography and three-dimensional computed tomography compared with stereolithographic models.

In a retrospective study, distance measurements of nine children with craniofacial malformation were analyzed. The accuracy of measurements was compared when measured on a workstation using a 16-slice multidetector spiral computed tomography and on a stereolithographic model. Three different methods of defining distances were investigated: 1) on the stereolithographic plastic models, 14 distances connecting landmarks were identified with a digitizer (Polaris Tracker); 2) the same distances were defined at axial, coronal, and sagittal reformats of the computed tomography data set and measured using a Philips MX View workstation; and 3) the same 14 distances were defined at three-dimensional virtual reality models of the skulls at the same workstation. All measurements were performed with all three methods by three different readers. The following conclusions could be drawn: stereolithographic models provide a highly exact reproduction of the skull in children with craniofacial malformations. They are a reliable basis for all analytic and probatory endeavors preparing complicated surgical corrections. Three-dimensional virtual reality display modes serve significantly better for exact distance measurements on the complex surface of the human skull than planar reformats of the same computed tomography data sets.

Application of platelet-rich plasma for enhanced bone regeneration in grafted sinus.

PURPOSE The present study was conducted to evaluate the effect of platelet-rich plasma (PRP) on new bone formation and remodeling after grafting of the maxillary sinus with an algae-derived hydroxyapatite AlgOss/C Graft/Algipore. MATERIALS AND METHODS Fourteen consecutive patients with severely atrophic maxillae underwent uni- or bilateral grafting of the maxillary sinus with a mixture of collected bone, algae-derived hydroxyapatite AlgOss/C Graft/Algipore (ratio 1:10), and a combined addition of PRP and thrombin (Tissucol Kit; Baxter, Vienna, Austria) to allow for fast clotting. After an average healing period of 7.1 months bone samples were retrieved. Patients from a former consecutive series treated without PRP served as control group. Statistical analysis was done by Welch 2-sample t test and mixed linear model testing. RESULTS In the coronal specimen portions, mean values for newly formed bone area, biomaterial area and marrow space of 32.2% ± 10.4%, 20.1% ± 13.0%, and 47.7% ± 8.5% were found with PRP, respectively. In the control group the corresponding values were 27.6% ± 13.4%, 20.3% ± 12.9%, and 52.1% ± 9.3%. In the apical specimen portions in the PRP group, the newly formed bone area, biomaterial area, and marrow space was 25.7% ± 15.0%, 23.4% ± 14.9%, and 50.9% ± 12.5%, respectively. The corresponding values in the control group were 17.0% ± 8.6%, 34.5% ± 11.2%, and 48.5% ± 8.5%. CONCLUSIONS Statistical evaluation of the samples proved significantly better overall resorption of algae-derived hydroxyapatite AlgOss/C Graft/Algipore and increased new bone formation when PRP was used, especially in the apical region.

Patient-Specific Polyetheretherketone Facial Implants in a Computer-Aided Planning Workflow

PURPOSE In the present study, we report an innovative workflow using polyetheretherketone (PEEK) patient-specific implants for esthetic corrections in the facial region through onlay grafting. The planning includes implant design according to virtual osteotomy and generation of a subtraction volume. The implant design was refined by stepwise changing the implant geometry according to soft tissue simulations. MATERIALS AND METHODS One patient was scanned using computed tomography. PEEK implants were interactively designed and manufactured using rapid prototyping techniques. Positioning intraoperatively was assisted by computer-aided navigation. Two months after surgery, a 3-dimensional surface model of the patients face was generated using photogrammetry. Finally, the Hausdorff distance calculation was used to quantify the overall error, encompassing the failures in soft tissue simulation and implantation. RESULTS The implant positioning process during surgery was satisfactory. The simulated soft tissue surface and the photogrammetry scan of the patient showed a high correspondence, especially where the skin covered the implants. The mean total error (Hausdorff distance) was 0.81 ± 1.00 mm (median 0.48, interquartile range 1.11). The spatial deviation remained less than 0.7 mm for the vast majority of points. CONCLUSIONS The proposed workflow provides a complete computer-aided design, computer-aided manufacturing, and computer-aided surgery chain for implant design, allowing for soft tissue simulation, fabrication of patient-specific implants, and image-guided surgery to position the implants. Much of the surgical complexity resulting from osteotomies of the zygoma, chin, or mandibular angle might be transferred into the planning phase of patient-specific implants.

Clinical Experiences With Resorbable Ultrasonic-Guided, Angle-Stable Osteosynthesis in the Panfacial Region

PURPOSE In this study we report our experiences with the treatment of midfacial fractures and various other indications in regions with low load bearing (eg, dysmorphias) using the biodegradable Osteosynthesis System (SonicWeld Rx by KLS Martin, Tuttlingen, Germany), comprising biomechanical and histological aspects. PATIENTS AND METHODS Seventy-five patients were included in this study. We describe the application of this system for the treatment of fractures of the zygomamaxillary complex, frontal bone impression fractures, surgical treatment of mukocele in the frontal sinus, isolated fractures of the orbital floor, complex midfacial trauma and bone cap fixation, craniosynostoses, and fixation of a distracted bone fragment. RESULTS The pin insertion could be finished with a total failure rate of lower than 5%. In 3 patients, soft tissue swellings in regions with less subcutaneous fat were observed 6 to 8 months postoperatively. No fracture dislocations occurred. Scanning electron micrograph of the experimentally acquired connection between the resorbable plate and 2 pins clearly demonstrates a tight and reliable fusion to bone, both at the cortical as well as at the spongy compartment. Conventional histology leads to corresponding findings as scanning electron micrography, and shows a close fusion between all components. CONCLUSION This retrospective study shows the general feasibility, sufficient mechanical stability, and efficient intraoperative handling of this angle-stable, ultrasonic-guided resorbable Osteosynthesis System (ResorbX and SonicWeld Rx) for a wide variety of indications in craniomaxillofacial surgery.

A comparative analysis of optical and conventional axiography for the analysis of temporomandibular joint movements

STATEMENT OF PROBLEM Currently available systems for pantographic tracing are heavy, bulky, and can interfere with jaw movements. PURPOSE This study describes the development and clinical application of optoelectronic axiography designed to overcome system inherent problems of conventional bulky frame-based registration axiography. The purpose of this study is the comparison of the newly developed system and conventional axiography. MATERIAL AND METHODS Three-dimensional recordings of condylar pathways were acquired by means of infrared digitizers interfaced to newly developed software. Ten distinct curves in each of 10 subjects were recorded by synchronous optoelectronic axiography (100 tracings) and by conventional axiography (100 tracings). Usually, two 3-dimensional (3D) light weight sensors are provisionally fixed to the facial surface of a maxillary and mandibular incisor by means of a single orthodontic bracket. To allow for direct comparison of all 100 pairs of curves in this study, the 3D sensors of the optoelectronic system were attached to the bulky double face-bow system of the axiograph. The conformity of tracings (protrusion, opening/closing, mediotrusion, and laterotrusion) was evaluated by means of correlation analysis. Resulting axiographic recordings from both systems were evaluated by 3 experts (dentists, experienced in axiographic investigations, who were blind to the source of the data), focusing on standardized qualitative criteria of the recordings (homogeneity/smoothness, pathway-characteristics, excursion, and left/right-symmetry). After testing for normal distribution of the ratio scaled data (length of pathway, horizontal condylar inclination [HCI], Bennett angle) with the Kolmogoroff-Smirnov test (alpha=.01), axiographic curves were quantitatively compared by means of an intraclass correlation coefficient ([ICC] alpha =.01). The Wilcoxon test (alpha=.01) was used to evaluate equivalence of ordinally scaled values (homogeneity of tracings) and Cohens Kappa was used to compare excursion and left/right symmetry. RESULTS High correspondence between curves recorded by conventional and optoelectronic axiography was observed. The mean differences of lengths between the protrusive, opening/closing, and mediotrusive pathways were 0.0 mm, 0.6 mm, and 0.1 mm, respectively. Pathways and values for HCI were found highly correlated (pathways: 95% CI of ICC 0.9776-0.9908; HCI: 95% CI of ICC 0.8641-0.9597). The 95% CIs for differences of pathways, HCI-value, and Bennett angle were -0.1mm/0.3mm, -3.4 degrees/1.9 degrees, and -2.8 degrees/4.8 degrees, respectively. Pathway characteristics also corresponded well (Cohens Kappa: 0.73 for symmetric and 0.72 for asymmetric movements), 0.77 for left/right symmetry, whereas other characteristics showed less significant correlation (Cohens Kappa of excursion: 0.21 for symmetric and 0.09 for asymmetric movements, homogeneity: 0.08 for symmetric and 0.15 for asymmetric movements). CONCLUSION Within the limitations of this study, optoelectronic axiography proved to be an applicable, promising technique, leading to diagnostic interpretations equivalent (with respect to the CIs) to conventional axiography.