Katja Schwenzer-Zimmerer

Use of a modified high submandibular approach to treat condylar base fractures: Experience with 44 consecutive cases treated in a single institution

PURPOSEnThe aim of this article is to present our experience treating fractures of the condylar base with a modification of the high submandibular approach (HSA).nnnMATERIALS AND METHODSnBetween June 2012 and April 2015, 44 fractures of the condylar base were treated in the Department of Oral and Maxillofacial Surgery of the Medical Hospital of Graz using the modified HSA.nnnRESULTSnWe did not observe any damage (even transient) to the facial nerve or any complication related to violation of the parotid capsule (such as a salivary fistula, Frey syndrome, or a sialocele).nnnCONCLUSIONSnThis approach provides good access to the condylar base, ensuring easier internal fixation, excellent protection of the facial nerve and parotid gland, and good cosmetic results.

Osteosynthesis using cannulated headless Herbert screws in mandibular angle fracture treatment: A new approach?

INTRODUCTIONnFractures of the mandibular angle are a common type of facial skull fracture. Although operative treatment includes a wide range of fixation techniques, a definite gold standard method has yet to be established. Headless, cannulated Herbert screws, often used in many forms of minimally invasive trauma surgery, provide functional and stable fracture fixation.nnnMATERIALS AND METHODSnIn a prospective, double-randomised, controlled, parallel-group - designed, inxa0vitro trial, the biomechanical behaviour of the Herbert bone screw system was compared to that of a conventional locking plate system in 40 mandibular angle fractures of human mandible cadaver phantoms.nnnRESULTSnThe mean stress values were 250 (±68.0) N in the plate subgroup and 200 (±61.0) N in the screw subgroup. The respective mean strain values were 7.90 (±2.7) mm and 6.90 (±2.2) mm, and the respective mean stiffness were values 1.10 (±0.61) N/m and 0.78 (±0.40) N/m. The differences in the results obtained using the two treatments were not significant (pxa0=xa00.55).nnnCONCLUSIONSnThe biomechanical behaviour of the two fixation systems within the tested loads did not significantly differ with respect to postoperative parameters clinically relevant in osteosynthesis. Both systems met the mandibular angle assessment criterion, which is considered to be sufficient for clinical use. The results indicate the potential clinical utility of these two systems, and recommend further testing.

Complications in tissue expansion: A logistic regression analysis for risk factors

BACKGROUNDnTissue expansion is frequently used in reconstructive surgery. Although the surgical procedure is typically considered simple, reported complication rates of tissue expansions exceed 40%. There is little evidence concerning risk factors for complications in tissue expansion in body regions other than breast. The aim was to determine risk factors for complications in non-breast tissue expansion.nnnMETHODSn34 patients treated with subcutaneous tissue expanders between 2005 and 2014 were analyzed. Demographic data, body-mass index (BMI), mean arterial blood pressure (MAP), treatment indications, expansion site, previous expansion therapies in the same body region, smoking history, as well as expander characteristics (shape, volume, and filling mechanism) were ascertained. Complications were assessed and ranked according to severity based on the Clavien-Dindo classification. Binary logistic regression analysis adjusted for clinical characteristics was used. A p<0.05 was considered as statistically significant.nnnRESULTSnComplications were observed in 26 out of 71 expanders analyzed (36.6%), of whom 10 led to therapy failure. Expanders used in the limbs, female gender, and high expander volume turned out as significant risk factors. Patients with both a high MAP and low BMI developed tissue necrosis significantly more often (p=0.002). The use of tissue expansion after a burn was not associated with an increased risk for complications.nnnCONCLUSIONSnThis is the first study revealing female gender and low BMI as risk factors in tissue expander surgery. Thus, careful patient selection is mandatory to avoid complications in tissue expansion. Burn patients do not develop complications more often.

Clinical evaluation of semi-automatic open-source algorithmic software segmentation of the mandibular bone: Practical feasibility and assessment of a new course of action

Introduction Computer assisted technologies based on algorithmic software segmentation are an increasing topic of interest in complex surgical cases. However—due to functional instability, time consuming software processes, personnel resources or licensed-based financial costs many segmentation processes are often outsourced from clinical centers to third parties and the industry. Therefore, the aim of this trial was to assess the practical feasibility of an easy available, functional stable and licensed-free segmentation approach to be used in the clinical practice. Material and methods In this retrospective, randomized, controlled trail the accuracy and accordance of the open-source based segmentation algorithm GrowCut was assessed through the comparison to the manually generated ground truth of the same anatomy using 10 CT lower jaw data-sets from the clinical routine. Assessment parameters were the segmentation time, the volume, the voxel number, the Dice Score and the Hausdorff distance. Results Overall semi-automatic GrowCut segmentation times were about one minute. Mean Dice Score values of over 85% and Hausdorff Distances below 33.5 voxel could be achieved between the algorithmic GrowCut-based segmentations and the manual generated ground truth schemes. Statistical differences between the assessment parameters were not significant (p<0.05) and correlation coefficients were close to the value one (r > 0.94) for any of the comparison made between the two groups. Discussion Complete functional stable and time saving segmentations with high accuracy and high positive correlation could be performed by the presented interactive open-source based approach. In the cranio-maxillofacial complex the used method could represent an algorithmic alternative for image-based segmentation in the clinical practice for e.g. surgical treatment planning or visualization of postoperative results and offers several advantages. Due to an open-source basis the used method could be further developed by other groups or specialists. Systematic comparisons to other segmentation approaches or with a greater data amount are areas of future works.

Assessment of tumor margins in head and neck cancer using a 3D-navigation system based on PET/CT image-fusion – a pilot study

OBJECTIVESnDetermination of tumor margins in patients with squamous cell carcinoma of the head and neck (SCCHN) is mostly based on preoperative magnetic resonance imaging (MRI) or computed tomography scans (CT). Local recurrence of disease is often correlated with the presence of positive resection margins after surgical treatment. Positron emission tomography/computed tomography (PET/CT) imaging plays a crucial role in the assessment of patients with SCCHN. The purpose of this study was to determine whether PET/CT could predict tumor extension.nnnMETHODSnIn 12 patients who underwent surgical treatment of primary SCCHN (Stage III-IV) F18-FDG PET/CT image-fusion was performed on a 3D navigation-system based workstation. Image-guided needle biopsies were obtained from four different, color-coded metabolic areas within the tumor. The histopathological findings were correlated with findings on corresponding PET/CT scans.nnnRESULTSn81.3% of biopsies from the central area were positive. Specimens taken from the outer metabolic zone were positive in 66.7% of the patients. The highest incidence of positive biopsies was found in the zone adjacent to the outermost area. There was a statistically significant difference in positive tumor histopathology when comparing the various metabolic zones (pxa0=xa00.03).nnnCONCLUSIONnExact determination of tumor is an important research topic, although results remain controversial. The results of this study suggest that in some cases PET scans may overestimate tumor extension.

Algorithmic evaluation of lower jawbone segmentations

The lower jawbone (or mandible), is due to its exposure to complex biomechanical forces the largest and strongest facial bone in humans. In this publication, an algorithmic evaluation of lower jawbone segmentation with a cellular automata algorithm called GrowCut is presented. For an evaluation, the algorithmic segmentation results were compared with slice-by-slice segmentations from two specialized physicians, which is considered to assess the given ground truth. As a result, pure manual slice-by-slice outlining took on average 39 minutes (minimum 35 minutes and maximum 46 minutes). This stands in strong contrast to an algorithmic segmentation which needed only about one minute for an initialization, hence needing just a fraction of the manual contouring time. At the same time, the algorithmic segmentations could achieve an acceptable Dice Similarity Score (DSC) of nearly ninety percent when compared to the ground truth slice-by-slice segmentations generated by the physicians. This stands in direct comparison to somewhat above ninety percent Dice Score between the two manual segmentations of the jawbones. In summary, this contribution shows that an algorithmic GrowCut segmentation can be an alternative to the very time consuming manual slice-by-slice outlining in the clinical practice.

Interactive Planning of Miniplates

In this contribution, a novel method for computer aided surgery planning of facial defects by using models of purchasable MedArtis Modus 2.0 miniplates is proposed. Implants of this kind, which belong to the osteosynthetic material, are commonly used for treating defects in the facial area. By placing them perpendicular on the defect, the miniplates are fixed on the healthy bone, bent with respect to the surface, to stabilize the defective area. Our software is able to fit a selection of the most common implant models to the surgeons desired position in a 3D computer model. The fitting respects the local surface curvature and adjusts direction and position in any desired way. Conventional methods use Computed Tomography (CT) scans to generate STereoLithic (STL) models serving as bending template for the implants or use a bending tool during the surgery for readjusting the implant several times. Both approaches lead to undesirable expenses in time. With our visual planning tool, surgeons are able to pre-plan the final implant within just a few minutes. The resulting model can be stored in STL format, which is the commonly used format for 3D printing. With this technology, surgeons are able to print the implant just in time or use it for generating a bending tool, both leading to an exactly bent miniplate.

Computer-aided position planning of miniplates to treat facial bone defects

In this contribution, a software system for computer-aided position planning of miniplates to treat facial bone defects is proposed. The intra-operatively used bone plates have to be passively adapted on the underlying bone contours for adequate bone fragment stabilization. However, this procedure can lead to frequent intra-operatively performed material readjustments especially in complex surgical cases. Our approach is able to fit a selection of common implant models on the surgeon’s desired position in a 3D computer model. This happens with respect to the surrounding anatomical structures, always including the possibility of adjusting both the direction and the position of the used osteosynthesis material. By using the proposed software, surgeons are able to pre-plan the out coming implant in its form and morphology with the aid of a computer-visualized model within a few minutes. Further, the resulting model can be stored in STL file format, the commonly used format for 3D printing. Using this technology, surgeons are able to print the virtual generated implant, or create an individually designed bending tool. This method leads to adapted osteosynthesis materials according to the surrounding anatomy and requires further a minimum amount of money and time.

Interaktive Planung von Gesichtsimplantaten

In diesem Beitrag wird eine neue Methode zur computerunterst utzten Behandlungsplanung von knochernen Gesichtsschadelbr uchen unter der Verwendung von Miniplatten vorgestellt. Diese Art von Implantaten wird verwendet, um Knochenbruche im Gesicht zu behandeln. Nach dem derzeitigen Stand der Technik verwendete Methoden wie die Plattenadaption an stereolithischen Modellen oder auf Basis einer computerunterstutzten Planung weisen allerdings eine geringere Flexibilitat, Mehrkosten oder hygienische Risiken auf. Mit der hier vorgestellten Software ist es den Chirurgen moglich, das Resultat vorab in nur wenigen Minuten an einem computervisualisierten Modell zu planen und anschliesend als STL-Datenformat zu exportieren, um es so in der zukunftstrachtigen 3D-Drucktechnologie verwenden zu konnen. Dadurch werden Chirurgen in die Lage gesetzt, das generierte Implantat oder eine entsprechende Biegevorlage flexibel fur jeden visualisierten Defekt im Behandlungszentrum prazise innerhalb weniger Stunden zu erstellen.

Surgical Safety Checklist: Practice in Cranio-Maxiollofacial Surgery

Background The World Health Organization introduced the Surgical Safety Checklist (SSC) to improve patients’ security in a surgical treatment [1]. The idea of checklists is established in different areas of safety culture, for example in aviation to improve passengers’ security. The SSC was first introduced in 2007. Meanwhile it is worldwide used in developed as well as in developing countries [2] to reduce the complication rate in the operating room. In the Department of Cranio-Maxillofacial Surgery of the University Hospital Graz it is used since 2011. The wellstructured checklist ensures safety standards for the patient and the personal. After a time of conversion and adaption there can be seen an amendment in daily routine.