Robin Seeberger

Accuracy assessment for navigated maxillo-facial surgery using an electromagnetic tracking device

PURPOSE To evaluate the accuracy and the usability of an electromagnetic tracking device in maxillo-facial surgery through testing on a phantom skull under operating room (OR) conditions. MATERIAL AND METHODS A standard plastic skull phantom was equipped with a custom made model of the maxilla and with target markers and dental brackets. Imaging was performed with a computed tomography (CT) scanner. The extent and robustness of the electromagnetic tracking systems target registration error (TRE) was evaluated under various conditions. RESULTS For each measurement a total of 243 registrations were performed with 5 point registration and 4374 registrations with 6 point registration. The average target registration error for the 5 point registration under OR conditions was 2.1 mm (SD 0.86) and 1.03 (SD 0.53) for the 6 point registration. Metallic instruments applied to the skull increased the TRE significantly in both registration methods. CONCLUSION The electromagnetic tracking device showed a high accuracy and performed stable in both registration methods. Electromagnetic interference due to metallic instruments was significant but the extent of TRE was still acceptable in comparison to optical navigation devices. A benefit of EM tracking is the absence of line-of-sight hindrance. The test setting simulating OR conditions has proven suitable for further studies.

Long term effects of surgically assisted rapid maxillary expansion without performing osteotomy of the pterygoid plates

PURPOSE Surgically assisted rapid maxillary expansions (SARME) are commonly used to widen the maxilla. This study evaluates long term stability of surgically assisted rapid palatal expansion without performing osteotomy of the pterygoid plates and its effects on nasal airway volume. MATERIALS AND METHODS 13 patients (mean age 31, 23+/-6, 11) with a maxillary transverse deficit of at least 5mm were examined 1 month before and on average 63 months after a mean palatal distraction of 8.29+/-1.68mm by acoustic rhinometry. Profiles of the nasal airway volumes were collected. A cast model analysis was performed. The data were evaluated using Wilcoxon signed rank test. RESULTS A V-shaped movement of the segments was observed. The gain for total nasal volume was 23.25%. Findings indicate a significant enhancement of nasal volume in all patients (P<0.01) as result of the maxillary expansion. No relapse occurred in the study group. CONCLUSION SARME provides a long term stable orthodontic bite correction and permanently enhances the nasal airways. A transverse shift of the segments can be achieved over the whole bony palate even when no osteotomy of the pterygo-maxillary suture is performed.

Craniofacial metastases: A 20-year survey

In this study we analysed the long-term prognosis of 52 patients with distant metastases to the craniofacial area. All patients were treated in our department between 1989 and 2009. Possible predictive factors for the overall survival prognosis like age, gender, histopathological type of the metastasis, location and tissue structure of the area in the head and neck region, time between primary tumour and metastasis and the therapy were evaluated. 62% of the patients with distant metastases in the craniofacial area were male (32/52), the average age was 63 years. Adenocarcinoma was the most common histological type (20/52) and lung (12/52), malignant melanoma of the skin (9/52) and breast (8/52) the most common primary tumour site. In 35% of all patients, the primary tumour was not known at the time of the diagnosis of the craniofacial metastasis, this number reduced to 17% without the patients with a CUP syndrome. Patients survived an average of 14.4 months after manifestation of the metastases and 43.4 months after the manifestation of the primary tumour.

Changes after surgically-assisted maxillary expansion (SARME) to the dentoalveolar, palatal and nasal structures by using tooth-borne distraction devices

Different devices are available to aid surgically-assisted maxillary expansion. In this study we have evaluated the changes to the anchoring teeth, the hard palate, and the lower nasal passage made by tooth-borne distraction devices. Thirty-one patients (mean (SD) age 28 (2) years) with deficiencies in the transverse width of the maxilla were examined by computed tomography and cone beam scans before and after operation. The data were analysed with the help of Wilcoxons signed rank test and Spearmans r correlation. The mean (SD) distraction width was 6.5 (2.3) mm. All anchorage teeth were tilted (p<0.01). The axes changed by a mean (SD) of 4.8 (0.9)° in the first premolar and 3.1 (0.8)° in the first molar. The nasal isthmus increased by a mean (SD) of 2.5 (0.3) mm. The hard palate adjacent to the anchoring teeth increased anteriorly by a mean (SD) of 2.8 (0.4) mm and posteriorly by 2.7 (0.4) mm. The hard palate was lowered by 1.2 (0.8) mm. There was a significant correlation in the distraction width, with changes in the intercoronal and interapical distances of the anchoring premolars (p<0.05) and with the interapical distance of the anchoring molars (p<0.01). There was also a correlation between the distraction width and the overall gain in width of the lower nasal passage (p<0.05). The results suggested that surgically-assisted maxillary expansion with tooth-borne devices has significant effects on the anchoring teeth, the nasal floor, and the hard palate. Both tilting of the teeth and an evenly distributed movement of the segments were seen.

Changes in the mandibular and dento-alveolar structures by the use of tooth borne mandibular symphyseal distraction devices

PURPOSE Different devices to perform a mandibular symphyseal distraction osteogenesis (MSDO) are available. This study evaluates how tooth borne distraction devices change to the teeth, the mandible and the condyles. MATERIALS AND METHODS 19 patients (mean age 27.1) with anterior width deficiencies of the mandible were examined with routine pre- and postoperative CT-scans 1 month before and 4 months after a mean distraction width of 5.68 mm (SD 0.88). The anchorage teeth of the tooth borne device were examined concerning displacement of their axes as well as the movement of the condyles and the mandibular symphysis. The data were evaluated using Wilcoxon signed rank test and Spearman rho correlation. RESULTS Significant tilting of the anchorage teeth was observed (p<0.01). The axes changed by 3.32° (SD 1.57) in the first premolar and by 2.63° (SD 1.75) in the first molar. A total of 2.67 mm (SD 1.17) of bone was formed on the symphysis. A significant correlation was found between distraction width and intercoronal distance changes of the anchorage teeth (p<0.01). No significant change of the intercondylar distance was found pre- and postoperatively in the Wilcoxon test. CONCLUSION MSDO with tooth borne devices has strong effects on the anchorage teeth. No severe effects on the condyles were observed. The postoperative width gain is a result of newly generated bone in the symphysis and tooth tilting. Nevertheless stable postoperative bite corrections are achievable.

The Use of Self-Inflating Soft Tissue Expanders Prior to Bone Augmentation of Atrophied Alveolar Ridges

BACKGROUND Extensive bone augmentation procedures are frequently performed prior to implant surgery. To achieve tension-free wound closure at the grafted site and thus avoid dehiscence and exposure or total loss of the bone graft, extensive soft tissue mobilization is required. In vitro studies have shown the potential of self-filling osmotic tissue expanders to optimize the amount of resulting soft tissue and vascularization of the recipient site. PURPOSE The purpose of this prospective clinical study was to evaluate the application and complication rate of osmotic hydrogel expanders inserted subperiosteally prior to bone grafting. METHODS In this prospective observational study, eight patients were implanted with 11 intraoral osmotic hydrogel expanders prior to bone augmentation procedures. All expanders were placed in subperiosteal positions using the tunnel technique. The occurrence of soft tissue-related complications such as necrosis, perforation, infection, or wound dehiscence leading to expander loss was defined as the primary parameter for analysis and evaluation. Further clinical parameters were soft tissue quality and quantity as well as expansion duration. RESULTS The expansion time depended upon defect size and expander dimensions. Complications, that is, perforation of the expanders through the oral mucosa, occurred in two patients (3 expanders) who suffered from extreme preoperative scarring in the treated areas owing to prior trauma in one patient and cleft surgery in the other. Patients were grafted with autologous (n = 7) or synthetic (n = 1) block grafts. The expanders were removed during bone grafting surgery. No further dehiscence occurred during the observation period, and all patients were treated successfully with dental implants and subsequent prosthetic reconstruction. CONCLUSIONS Within the limits of this observational clinical study, hydrogel expanders may help to generate additional soft tissue, and they might contribute to the overall improvement of the bone augmentation process by reducing the risk of complications related to the lack of soft tissue. Further randomized controlled studies are necessary.

Surgical outcome after using a modified technique of the pi-procedure for posterior sagittal suture closure

Fusion of the sagittal suture is the most prevalent form of craniosynostosis. Due to the variety of deformities of scaphocephaly depending on the location of the fused sagittal suture, the surgical procedure has to be adjusted to the individual case. In this study, 38 patients with a predominantly posterior sagittal suture closure were treated with a modified technique of the pi-procedure and the surgical outcome has been evaluated with respect to complications, morphological and aesthetic outcome. The improvement of the cephalic index in our series in the follow-up examination (mean 60.1 months) after surgery was significant (p<0.0001). According to the classification of Whitaker, 31 patients had a Class 1 outcome, with excellent surgical results. Aesthetic outcomes were excellent in 29, good in 5, and poor in 4 of cases, as judged by both the families and the craniofacial team. No severe complications have been observed. Posterior sagittal suture with marked occipital bulging can be successfully treated with this modified posterior procedure with a low complication rate, significant improvement of the cephalic index and a good aesthetic outcome. In all cases of sagittal synostosis, the operative procedure should be tailored to the nature and severity of the deformity.

Reconstruction of Severely Atrophied Alveolar Ridges with Calvarial Onlay Bone Grafts and Dental Implants

OBJECTIVE Severely atrophied alveolar ridges are most commonly reconstructed with free autologous bone grafts from the iliac crest. The use of these grafts, however, is frequently associated with bone resorption as possible late complication after implant surgery and prosthetic loading. Other donor sites, especially intraoral donor sites, show limited availability. The aim of this present study was to evaluate the clinical and radiographical outcome of alveolar ridge reconstruction with bone from the calvarium and subsequent implant rehabilitation. PATIENTS AND METHODS Reconstruction was performed by using calvarial split grafts in case of severe and complex alveolar ridge defects induced by trauma or bone atrophy. Fifteen patients were treated at 19 different intraoral recipient sites (15 sites in the maxilla, four in the mandible). Autologous block grafts were used for combined vertical and horizontal grafting. After a 3-month healing period, patients received dental implants. A total of 99 dental implants (OsseoSpeed™, Astra Tech AB, Mölndal, Sweden) were inserted and left to heal in a submerged position for 3 months before the prosthetic implant-based rehabilitation was performed. RESULTS No donor site complications occurred during or after surgery. At the intraoral recipient sites two infections occurred, leading to partial loss of the grafts. Implant placement, however, was possible in all cases. Two of 99 implants were lost in two patients prior to prosthetic loading. Patients were followed up clinically and radiographically for an average observation period of 28 months. Implant survival rate and success rates were 97.85 and 95.7%, respectively, and a minimal marginal bone loss was documented. DISCUSSION The low morbidity at the donor sites and the good marginal bone stability in the reconstructed regions indicate that calvarial bone grafts represent a viable treatment alternative to grafts from the iliac crest.

Approach to intraoperative electromagnetic navigation in orthognathic surgery: A phantom skull based trial.

INTRODUCTION Intraoperative guidance using electromagnetic navigation is an upcoming method in maxillofacial surgery. However, due to their unwieldy structures, especially the line-of-sight problem, optical navigation devices are not used for daily orthognathic surgery. Therefore, orthognathic surgery was simulated on study phantom skulls, evaluating the accuracy and handling of a new electromagnetic tracking system. MATERIAL AND METHODS Le-Fort I osteotomies were performed on 10 plastic skulls. Orthognathic surgical planning was done in the conventional way using plaster models. Accuracy of the gold standard, splint-based model surgery versus an electromagnetic tracking system was evaluated by measuring the actual maxillary deviation using bimaxillary splints and preoperative and postoperative cone beam computer tomography imaging. The distance of five anatomical marker points were compared pre- and postoperatively. RESULTS The electromagnetic tracking system was significantly more accurate in all measured parameters compared with the gold standard using bimaxillary splints (p < 0.01). The data shows a discrepancy between the model surgical plans and the actual correction of the upper jaw of 0.8 mm. Using the electromagnetic tracking, we could reduce the discrepancy of the maxillary transposition between the planned and actual orthognathic surgery to 0.3 mm on average. DISCUSSION The data of this preliminary study shows a high level of accuracy in surgical orthognathic performance using electromagnetic navigation, and may offer greater precision than the conventional plaster model surgery with bimaxillary splints. CONCLUSION This preliminary work shows great potential for the establishment of an intraoperative electromagnetic navigation system for maxillofacial surgery.

Magnetic resonance imaging in isolated sagittal synostosis.

Abstract Isolated fusion of the sagittal suture is the most prevalent form of craniosynostosis. Although the typical clinical appearance usually points the way to the right diagnosis, computed tomographic (CT) scans are still recommended as necessary tools for both the diagnosis of scaphocephaly and the preoperative planning. Because CT scans are accompanied by the biological effects of ionizing radiation, some authors have already postulated the use of magnetic resonance imaging (MRI) especially because MRI seems to be valuable for detecting intracranial anomalies compared with CT scans. Hence, we investigated the preoperative MRIs of 42 children with isolated sagittal synostosis to evaluate the frequency of brain anomalies and their therapeutic consequences. In our study, 10 patients (23.8%) showed pathologic MRI findings such as ventricular dilatation and hypoplastic corpus callosum, whereas 32 patients (76.2%) had an unremarkable MRI except a pathognomonic secondary deformation of the brain caused by the abnormally shaped skull, which was present in all patients. Seven patients showed clinically significant symptoms including papilledema or psychomotoric developmental delay; however, the clinical appearance was not predictive for pathologic MRI findings and vice versa. As the detection of brain anomalies had no influence on the surgical procedure or led to any additive therapy in our patients, we conclude that evaluation of possible pathologic brain findings does not legitimate the general use of MRI in clinically normal children with isolated sagittal synostosis.