Balvinder Khambay

How accurate is model planning for orthognathic surgery

The purpose of this study was to evaluate the accuracy of model surgery prediction after orthognathic surgery and to identify possible errors associated with the prediction process. The study included 46 patients who had undergone orthognathic surgical procedures; 22 in Group A who had had a Le Fort I osteotomy; and 24 in Group B who had had a Le Fort I osteotomy and mandibular setback surgery. The immediate postoperative and preoperative lateral cephalograms were analysed to calculate surgical changes; these were compared with those obtained from model surgery prediction and a statistical analysis was undertaken. The maxilla was more under-advanced and over-impacted anteriorly than predicted by model surgery. The amount of mandibular setback was more than that predicted by model surgery. None of the differences between prediction planning and actual surgical changes was statistically significant at p<0.05. Inaccuracy with the face bow recording, the intermediate wafer, and auto-rotation of the mandible in the supine or anaesthetized patient would appear to be the principal reasons for errors. Inaccuracies are associated with the transfer of prediction planning to model surgery planning and prediction, which should be eliminated to improve the accuracy and predictability of orthognathic surgery.

Preliminary assessment of skeletal stability after sagittal split mandibular advancement using a bioresorbable fixation system

We studied skeletal stability during the first year after mandibular advancement and fixation with bioresorbable self-reinforced poly-L-lactide (SR-PLLA) screws in 11 patients by cephalometric measurements. We compared these with a cohort of 11 patients, in whom titanium screws were used for fixation. We found no significant difference between the two groups in the median preoperative cephalometric values and the median changes after operation. There was also no significant difference between the two groups regarding the median extent of relapse 1-year after operation. We conclude that bioresorbable SR-PLLA screws are comparable to metallic screws for fixation of bone after sagittal split mandibular advancement.

Objective evaluation of the latissimus dorsi flap for breast reconstruction using three-dimensional imaging

BACKGROUNDnThe latissimus dorsi muscle flap is a common method for the reconstruction of the breast following mastectomy. The study aimed to assess the quality of this reconstruction using a three-dimensional (3D) imaging method. The null hypothesis was that there was no difference in volume between the reconstructed breast and the opposite side.nnnMETHODSnThis study was conducted in forty-four patients who had had immediate unilateral breast reconstruction by latissimus dorsi muscle flap. The breast was captured using the 3D imaging system. Ten landmarks were digitised on the 3D images. The volume of each breast was measured by the application of Breast Analysis Tool software. The symmetry of the breast was measured using Procrustes analysis. The impact of breast position, orientation, size and intrinsic shape on the overall breast asymmetry was investigated.nnnRESULTSnThe null hypothesis was rejected. The reconstructed breast showed a significantly smaller volume when compared to the opposite side, p < 0.0001, a mean difference of 176.8 cc and 95% CI (103.5, 250.0). The shape and the position of the reconstructed breast were the main contributing factors to the measured asymmetry score.nnnCONCLUSIONSn3D imaging was efficient in evaluating the outcome of breast surgery. The latissimus dorsi muscle flap on its own for breast reconstruction did not restore the volume and shape of the breast fully lost due to complete mastectomy. The modification of this method and the selection of other or additional surgical techniques for breast reconstruction should be considered. The asymmetry analysis through reflection and Procrustes matching was a useful method for the objective shape analysis of the female breast and presented a new approach for breast shape assessment. The intrinsic breast shape and the positioning of the breast were major components of postoperative breast asymmetry. The reconstructed breast was smaller overall than the un-operated breast at a significant level when assessing the breast volume using the surface area. 3D imaging by multiple stereophotogrammetry was a useful tool for volume measurements, shape analysis and the evaluation of symmetry.

An assessment of the quality of care provided to orthognathic surgery patients through a multidisciplinary clinic

The quality of care delivered to 74 patients undergoing orthognathic surgery was assessed using a patient satisfaction questionnaire and data collected from hospital case records. Surgical complications, hospital services, patient satisfaction, and impact on quality of life, were the main aspects considered. The majority of patients reported that their treatment objectives had been achieved and that they were satisfied with the quality of care provided. The main concern of the patients regarding the clinic was the waiting time before an appointment could be offered. Eating and breathing difficulties and low mood after surgery were the main reported complications. Sixty-three patients experienced post-operative weight loss. The importance of a nutritious, high calorie soft diet should be emphasised and the use of menthol inhalations following maxillary osteotomies should be considered more frequently. Clinicians should be aware of post-operative low mood, which may require psychological support. We developed a sensitive assessment battery with comprehensive parameters to audit quality of orthognathic surgery service, and recommend that a similar approach should be considered by teams which undertake management of orthognathic patients.

Clinical significance of creative 3D-image fusion across multimodalities [PET + CT + MR] based on characteristic coregistration

OBJECTIVEnTo investigate a registration approach for 2-dimension (2D) based on characteristic localization to achieve 3-dimension (3D) fusion from images of PET, CT and MR one by one.nnnMETHODnA cubic oriented scheme of9-point & 3-plane for co-registration design was verified to be geometrically practical. After acquisiting DICOM data of PET/CT/MR (directed by radiotracer 18F-FDG etc.), through 3D reconstruction and virtual dissection, human internal feature points were sorted to combine with preselected external feature points for matching process. By following the procedure of feature extraction and image mapping, picking points to form planes and picking planes for segmentation were executed. Eventually, image fusion was implemented at real-time workstation mimics based on auto-fuse techniques so called information exchange and signal overlay.nnnRESULTnThe 2D and 3D images fused across modalities of [CT+MR], [PET+MR], [PET+CT] and [PET+CT+MR] were tested on data of patients suffered from tumors. Complementary 2D/3D images simultaneously presenting metabolic activities and anatomic structures were created with detectable-rate of 70%, 56%, 54% (or 98%) and 44% with no significant difference for each in statistics.nnnCONCLUSIONnCurrently, based on the condition that there is no complete hybrid detector integrated of triple-module [PET+CT+MR] internationally, this sort of multiple modality fusion is doubtlessly an essential complement for the existing function of single modality imaging.

Digital replacement of the distorted dentition acquired by cone beam computed tomography (CBCT): a pilot study

During cone beam computed tomography (CBCT) scanning, intra-oral metallic objects may produce streak artefacts, which impair the occlusal surface of the teeth. This study aimed to determine the accuracy of replacement of the CBCT dentition with a more accurate dentition and to determine the clinical feasibility of the method. Impressions of the teeth of six cadaveric skulls with unrestored dentitions were taken and acrylic base plates constructed incorporating radiopaque registration markers. Each appliance was fitted to the skull and a CBCT performed. Impressions were taken of the dentition with the devices in situ and dental models were produced. These were CBCT-scanned and the images of the skulls and models imported into computer-aided design/computer-aided manufacturing (CAD/CAM) software and aligned on the registration markers. The occlusal surfaces of each dentition were then replaced with the occlusal image of the corresponding model. The absolute mean distance between the registration markers in the skulls and the dental models was 0.09±0.02mm, and for the dentition was 0.24±0.09mm. When the method was applied to patients, the distance between markers was 0.12±0.04mm for the maxilla and 0.16±0.02mm for the mandible. It is possible to replace the inaccurate dentition on a CBCT scan using this method and to create a composite skull which is clinically acceptable.

Evaluation of an interactive multi-media device for delivering information on Le Fort I osteotomy

This study was carried out on volunteers to evaluate a newly developed interactive software package aimed at informing prospective Le Fort I osteotomy patients regarding the surgical technique and possible complications. The aim of the study was to compare two methods of information delivery; a multi-media tablet device delivering both graphic and verbal information, and an audio device delivering essentially the same information in verbal form only. The null hypothesis was that there would be no difference between the efficiencies of the two methods. The subjects ability to recall the information delivered by both devices was assessed using a questionnaire. The tablet device participants scored an average of 15.48 points, while the audio device participants scored an average of 268 points. The difference was statistically significant (p < 0.001), suggesting that the multi-media tablet device was more effective method.

Self-correction of 3D reconstruction from multi-view stereo images

We present a self-correction approach to improving the 3D reconstruction of a multi-view 3D photogrammetry system. The self-correction approach has been able to repair the reconstructed 3D surface damaged by depth discontinuities. Due to self-occlusion, multi-view range images have to be acquired and integrated into a watertight non-redundant mesh model in order to cover the extended surface of an imaged object. The integrated surface often suffers from “dent” artifacts produced by depth discontinuities in the multi-view range images. In this paper we propose a novel approach to correcting the 3D integrated surface such that the dent artifacts can be repaired automatically. We show examples of 3D reconstruction to demonstrate the improvement that can be achieved by the self-correction approach. This self-correction approach can be extended to integrate range images obtained from alternative range capture devices.

Brustform und symmetrie untersuchung durch statistische procrustes analyse basierend auf landmarken

Einleitung/Zielsetzung: Eine mathematische Analyse der Brustform und -symmetrie durch landmarkbasierte Procrustes Berechnung wird vorgestellt. Eine Evaluation von einzelnen Komponenten der Brustsymmetrie und mogliche Einflussnahme bei der Brustrekonstruktion erfolgt. n nMaterial & Methoden: Brust Asymmetrie wird quantifiziert als das Mas der Unterschiede zwischen einer 3D Landmark-Konfiguration auf einer Brust und ihres reflektierten Bildes. Zehn Landmarken, jeweils vier pro Seite und zwei fur eine Mittelliniendefinition wurden digital markiert und ihre 3D Koordinaten statistisch mithilfe eines Softwareprogrammes R ausgewertet. Uber eine Mittellinie vom Jugulum zum Manubrium sterni erfolgte eine spiegelbildliche Uberlagerung der einen auf die andere Brust. Die Daten einer rekonstruierten und nicht-operierten Brust von vier und vierzig Patientinnen wurden untersucht. Die statistischen Unterschiede der Procrustes Analyse gingen in einen Asymmetrie Score ein und Anteile einzelner Komponenten wurden berechnet. Diese waren die Grose, Lokation und Orientierung der Brust und daruber hinaus brusteigene morphologische Oberflachenformdaten. n nErgebnisse: Brustasymmetrie fand sich bei allen vier-und vierzig Patientinnen und der mittlere Asymmetrie score betrug 0,52. Der Berechnung der Anteile der einzelnen Komponenten des Asymmetrie Score ergab, dass morphologische Oberflachendaten hierbei am starksten zum Asymmetrie Score beitrugen, dicht gefolgt von Daten zur Lokation, entsprechend der Positionierung der Brust auf der Thoraxwand. Brustgrose und Orientierung spielten hingegen eine geringere Rolle. n nZusammenfassung: Bei der Betrachtung der Brustsymmetrie spielt die Form eine wichtigere Rolle als die Grose wie durch die statistische Procrustes Analyse objektiv nachgewiesen wurde. Fast ebenso wichtig wie die Form ist die Positionierung der Brust auf der Thoraxwand, die deutlich starker zur gesamten Brustsymmetrie beitragt als eine Grosenerhebung oder Achsendrehung.

A paradigm shift in the diagnosis & management of dentofacial deformities.

For many years the diagnosis of dentofacial deformities and the prediction planning of the surgical correction were limited to two dimensional (2D) radiographs and photographs. There are many limitations associated with this approach which include geometrical distortion and superimposition in 2D images, evaluation and prediction planning are limited to the patients’ profile, facial asymmetries are not fully analysed and 3D soft tissue changes following orthognathic surgery are not considered. n nOver the last few years there has been a significant paradigm shift in our clinical approach towards the management of dentofacial deformities (Swennen et al., 2009). The ultimate goal of orthognathic surgery is to improve the harmony of soft tissue appearance which is usually the patients’ main concern. Improving labial seal, naso-labial configuration and chin prominence are amongst the main objectives for orthognathic surgery. Improving medio-lateral, vertical and antero-posterior asymmetries of facial morphology can be readily achieved with standard orthognathic procedures. The morphology of the vermillion border of both upper and lower lips is altered significantly with orthognathic surgery. Therefore, the magnitude and direction of movement of the osteotomy segmented should be planned to archive the required alterations in the oro-facial appearance. This would not be achieved unless the position and the inclination of the teeth are pre-planned to allow the desired movements of the osteotomy segments (Fig. 1). Therefore, it is a necessity for the majority of cases to undergo presurgical orthodontic treatment to decompensate and reveal the true extent of the underlying deformities in preparation for orthognathic surgery. The team approach between the orthodontist, surgeons and technologist is essential to plan the cases appropriately and archive the best possible results following orthognathic surgery (Fig. 1). n n n nFigure 1 n nA diagram illustrating the mechanism of planning and executing the surgical correction of dentofacial deformities. n n n nThe need for comprehensive and full analysis of dento-facial morphology has inspired clinicians to adopt 3D imaging modalities to capture and analyse facial soft tissue morphology, the shape of the jaw bones as well as the dental occlusion (Benington et al., 2010, Fig. 2). Three-dimensional imaging techniques have attempted to overcome the shortcomings of conventional two-dimensional methods. These techniques have included: morphanalysis, laser scanning, 3D computerised tomography scanning, 3D ultrasonography, Moire topography and contour photography. n n n nFigure 2 n nA diagram illustrating the 3D images of the face, skull and dentition.