Raphael Olszewski

3D CT-based cephalometric analysis: 3D cephalometric theoretical concept and software.

IntroductionWe present an original three-dimensional cephalometric analysis based on a transformation of a classical two dimensional topological cephalometry.MethodsTo validate the three-dimensional cephalometric CT based concept we systematically compared the alignments of anatomic structures. We used digital lateral radiography to perform the classical two-dimensional cephalometry, and a three-dimensional CT surface model for the three-dimensional cephalometry.ResultsDiagnoses based on both two-dimensional and three-dimensional analyses were adequate, but the three-dimensional analysis gave more information such as the possibility of comparing the right and left side of the skull. Also the anatomic structures were not superimposed which improved the visibility of the reference landmarks.ConclusionWe demonstrated that three-dimensional analysis gives the same results as two-dimensional analysis using the same skull. We also present possible applications of the method.

Reproducibility of osseous landmarks used for computed tomography based three-dimensional cephalometric analyses

PURPOSE The aim of this paper was to measure the reproducibility of osseous landmark identification from two recently described three-dimensional (3D) cephalometric analyses: 3D-ACRO and 3D-Swennen analyses. The study population consisted of 13 patients examined with spiral 3D computed tomography (CT). We used a previously validated low-dose CT protocol. For each analysis, 22 cephalometric reference landmarks were identified on 3D CT surface renderings. Forty-four reference landmarks were identified per patient. Two series of identifications were performed by two independent observers. In total, 3432 imaging measurements were completed. The intra-observer reconstructed mean log was 1.210+/-1.042mm for the 3D-ACRO analysis, and 1.311+/-1.042mm for 3D-Swennen analysis (comparison: p=0.17 NS). The inter-observer reconstructed mean log was 1.799+/-1.037mm for the 3D-ACRO analysis, and 2.465+/-1.036mm for 3D-Swennen analysis (comparison: p=0.000000002). The difference between the intra- and inter-observer reconstructed mean logs were 1.486+/-1.057mm for 3D-ACRO and 1.880+/-1.056mm for 3D-Swennen analysis. In conclusions: 3D-ACRO analysis was significantly more reproducible than 3D-Swennen analysis (p=0.0027) due to the use of a majority of highly reproducible cephalometric landmarks. Finally, we propose a classification scheme and exclusion criteria for reference landmarks used in 3D cephalometrics, based on inter-observer reproducibility and anatomical reality.

Innovative procedure for computer-assisted genioplasty : three-dimensional cephalometry, rapid-prototyping model and surgical splint

The authors present a new procedure of computer-assisted genioplasty. They determined the anterior, posterior and inferior limits of the chin in relation to the skull and face with the newly developed and validated three-dimensional cephalometric planar analysis (ACRO 3D). Virtual planning of the osteotomy lines was carried out with Mimics (Materialize) software. The authors built a three-dimensional rapid-prototyping multi-position model of the chin area from a medical low-dose CT scan. The transfer of virtual information to the operating room consisted of two elements. First, the titanium plates on the 3D RP model were pre-bent. Second, a surgical guide for the transfer of the osteotomy lines and the positions of the screws to the operating room was manufactured. The authors present the first case of the use of this model on a patient. The postoperative results are promising, and the technique is fast and easy-to-use. More patients are needed for a definitive clinical validation of this procedure.

Towards an integrated system for planning and assisting maxillofacial orthognathic surgery

Computer-assisted maxillofacial orthognathic surgery is an emerging and interdisciplinary field linking orthognathic surgery, remote signal engineering and three-dimensional (3D) medical imaging. Most of the computational solutions already developed make use of different specialized systems which introduce difficulties both in the information transfer from one stage to the others and in the use of such systems by surgeons. Trying to address such issue, in this work we present a common computer-based system that integrates proposed modules for planning and assisting the maxillofacial surgery. With that we propose to replace the current standard orthognathic preoperative planning, and to bring information from a virtual planning to the real operative field. The system prototype, including three-dimensional cephalometric analysis, static and dynamic virtual orthognathic planning, and mixed reality transfer of information to the operation room, is described and the first results obtained are presented.

Les limites de la chirurgie des modèles en chirurgie orthognathique: implications théoriques et pratiques

Orthognathic model surgery is a classical technique used to simulate orthognathic surgical cases. However, a detailed analysis of this technique demonstrates that theoretical errors and inaccuracies can occur in routine practice. 2D and 3D cephalometric analysis is the first source of inaccuracies. Then, during the occlusal plane transfer from the patient to the semi-adjustable dental articulator, errors can occur by inaccurate manipulation of the facial bow. Simulating the operation on the plaster cast is difficult due to the lack of a real link between the cephalometric analysis and the model surgery. Rotation and translation movements of the plaster casts are insufficiently controlled during the model surgery stage. Finally, the splint, which transfers the final relative position of maxilla to the mandible, summates all of the errors of the previous stages.

Validity of 2D lateral cephalometry in orthodontics: a systematic review

Lateral cephalometric radiography is commonly used as a standard tool in orthodontic assessment and treatment planning. The aim of this study was to evaluate the available scientific literature and existing evidence for the validation of using lateral cephalometric imaging for orthodontic treatment planning. The secondary objective was to determine the accuracy and reliability of this technique. We did not attempt to evaluate the value of this radiographic technique for other purposes. A literature search was performed using specific keywords on electronic databases: Ovid MEDLINE, Scopus and Web of Science. Two reviewers selected relevant articles, corresponding to predetermined inclusion criteria. The electronic search was followed by a hand search of the reference lists of relevant papers. Two reviewers assessed the level of evidence of relevant publications as high, moderate or low. Based on this, the evidence grade for diagnostic efficacy was rated as strong, moderately strong, limited or insufficient. The initial search revealed 784 articles listed in MEDLINE (Ovid), 1,034 in Scopus and 264 articles in the Web of Science. Only 17 articles met the inclusion criteria and were selected for qualitative synthesis. Results showed seven studies on the role of cephalometry in orthodontic treatment planning, eight concerning cephalometric measurements and landmark identification and two on cephalometric analysis. It is surprising that, notwithstanding the 968 articles published in peer-reviewed journals, scientific evidence on the usefulness of this radiographic technique in orthodontics is still lacking, with contradictory results. More rigorous research on a larger study population should be performed to achieve full evidence on this topic.

Accuracy of three-dimensional, paper-based models generated using a low-cost, three-dimensional printer

Our study aimed to determine the accuracy of a low-cost, paper-based 3D printer by comparing a dry human mandible to its corresponding three-dimensional (3D) model using a 3D measuring arm. One dry human mandible and its corresponding printed model were evaluated. The model was produced using DICOM data from cone beam computed tomography. The data were imported into Maxilim software, wherein automatic segmentation was performed, and the STL file was saved. These data were subsequently analysed, repaired, cut and prepared for printing with netfabb software. These prepared data were used to create a paper-based model of a mandible with an MCor Matrix 300 printer. Seventy-six anatomical landmarks were chosen and measured 20 times on the mandible and the model using a MicroScribe G2X 3D measuring arm. The distances between all the selected landmarks were measured and compared. Only landmarks with a point inaccuracy less than 30% were used in further analyses. The mean absolute difference for the selected 2016 measurements was 0.36 ± 0.29 mm. The mean relative difference was 1.87 ± 3.14%; however, the measurement length significantly influenced the relative difference. The accuracy of the 3D model printed using the paper-based, low-cost 3D Matrix 300 printer was acceptable. The average error was no greater than that measured with other types of 3D printers. The mean relative difference should not be considered the best way to compare studies. The point inaccuracy methodology proposed in this study may be helpful in future studies concerned with evaluating the accuracy of 3D rapid prototyping models.

Three-dimensional appearance of the lips muscles with three-dimensional isotropic MRI: in vivo study.

IntroductionOur knowledge of facial muscles is based primarily on atlases and cadaveric studies. This study describes a non-invasive in vivo method (3D MRI) for segmenting and reconstructing facial muscles in a three-dimensional fashion.MethodsThree-dimensional (3D), T1-weighted, 3 Tesla, isotropic MRI was applied to a subject. One observer performed semi-automatic segmentation using the Editor module from the 3D Slicer software (Harvard Medical School, Boston, MA, USA), version 3.2.ResultsWe were able to successfully outline and three-dimensionally reconstruct the following facial muscles: pars labialis orbicularis oris, m. levatro labii superioris alaeque nasi, m. levator labii superioris, m. zygomaticus major and minor, m. depressor anguli oris, m. depressor labii inferioris, m. mentalis, m. buccinator, and m. orbicularis oculi.Conclusions3D reconstruction of the lip muscles should be taken into consideration in order to improve the accuracy and individualization of existing 3D facial soft tissue models. More studies are needed to further develop efficient methods for segmentation in this field.

Preoperative, intraoperative, and postoperative complications in orthognathic surgery: a systematic review.

ObjectivesThe aim of this study was to determine whether orthognathic surgery is associated with any complications, and what type of complications may occur.Materials and methodsData were obtained using PubMed (MEDLINE), ISI Web of Knowledge, Ovid, Cochrane Library, Embase Library, and an additional manual search. The titles and abstracts of the electronic search results were screened and evaluated by two observers for eligibility according to the inclusion and exclusion criteria.ResultsA total of 1924 articles were identified, and we retained 44 articles for the final analysis. The Prisma diagram flowchart demonstrates our selection scheme. For the purpose of this study, the Cochrane data extraction form was modified. One review author extracted data from the included studies, and the second author checked all of the forms. The hierarchy of evidence classification from the UK NHS Centre for Reviews and Dissemination was used to assess the level of evidence for the retrieved studies.ConclusionsAn evaluation of the obtained studies revealed the existence of a large number of varied complications associated with orthognathic surgery procedures.Clinical relevanceOral and maxillofacial surgeons, orthodontists, and the surgical team need to prevent such complications during preoperative, intraoperative, and postoperative periods to increase the safety of orthognathic surgery procedures. This review was registered on http://www.crd.york.ac.uk/PROSPERO as CRD42013004711.

Shape and volume of craniofacial cavities in intentional skull deformations

Intentional cranial deformations (ICD) have been observed worldwide but are especially prevalent in preColombian cultures. The purpose of this study was to assess the consequences of ICD on three cranial cavities (intracranial cavity, orbits, and maxillary sinuses) and on cranial vault thickness, in order to screen for morphological changes due to the external constraints exerted by the deformation device. We acquired CT-scans for 39 deformed and 19 control skulls. We studied the thickness of the skull vault using qualitative and quantitative methods. We computed the volumes of the orbits, of the maxillary sinuses, and of the intracranial cavity using haptic-aided semi-automatic segmentation. We finally defined 3D distances and angles within orbits and maxillary sinuses based on 27 anatomical landmarks and measured these features on the 58 skulls. Our results show specific bone thickness patterns in some types of ICD, with localized thinning in regions subjected to increased pressure and thickening in other regions. Our findings confirm that volumes of the cranial cavities are not affected by ICDs but that the shapes of the orbits and of the maxillary sinuses are modified in circumferential deformations. We conclude that ICDs can modify the shape of the cranial cavities and the thickness of their walls but conserve their volumes. These results provide new insights into the morphological effects associated with ICDs and call for similar investigations in subjects with deformational plagiocephalies and craniosynostoses.