'Direct DICOM slice landmarking' a novel research technique to quantify skeletal changes in orthognathic surgery

The limitations of the current methods of quantifying the surgical movements of facial bones inspired this study. The aim of this study was the assessment of the accuracy and reproducibility of directly landmarking of 3D DICOM images (Digital Imaging and Communications in Medicine) to quantify the changes in the jaw bones following surgery. The study was carried out on plastic skull to simulate the surgical movements of the jaw bones. Cone beam CT scans were taken at 3mm, 6mm, and 9mm maxillary advancement; together with a 2mm, 4mm, 6mm and 8mm “down graft” which in total generated 12 different positions of the maxilla for the analysis. The movements of the maxilla were calculated using two methods, the standard approach where distances between surface landmarks on the jaw bones were measured and the novel approach where measurements were taken directly from the internal structures of the corresponding 3D DICOME slices. A one sample t-test showed that there was no statistically significant difference between the two methods of measurements for the y and z directions, however, the x direction showed a significant difference. The mean difference between the two absolute measurements were 0.34±0.20mm, 0.22±0.16mm, 0.18±0.13mm in the y, z and x directions respectively. In conclusion, the direct landmarking of 3D DICOM image slices is a reliable, reproducible and informative method for assessment of the 3D skeletal changes. The method has a clear clinical application which includes the analysis of the jaw movements “orthognathic surgery” for the correction of facial deformities

Assessing the outcome of orthognathic surgery by three-dimensional soft tissue analysis

Studies of orthognathic surgery often focus on pre-surgical versus post-surgical changes in facial shape. In contrast, this study provides an innovative comparison between post-surgical and control shape. Forty orthognathic surgery patients were included, who underwent three different types of surgical correction: Le Fort I maxillary advancement, bilateral sagittal split mandibular advancement, and bimaxillary advancement surgery. Control facial images were captured from volunteers from local communities in Glasgow, with patterns of age, sex, and ethnic background that matched those of the surgical patients. Facial models were fitted and Procrustes registration and principal components analysis used to allow quantitative analysis, including the comparison of group mean shape and mean asymmetry. The primary characteristic of the difference in shape was found to be residual mandibular prognathism in the group of female patients who underwent Le Fort I maxillary advancement. Individual cases were assessed against this type of shape difference, using a quantitative scale to aid clinical audit. Analysis of the combined surgical groups provided strong evidence that surgery reduces asymmetry in some parts of the face such as the upper lip region. No evidence was found that mean asymmetry in post-surgical patients is greater than that in controls

3D soft-tissue, 2D hard-tissue and psychosocial chantes following orthognathic surgery

A 3D imaging system (C3D®), based on the principles of stereophotogrammetry, has been developed for use in the assessment of facial changes following orthognathic surgery. Patients’ perception of their facial appearance before and after orthognathic surgery has been evaluated using standardised questionnaires, but few studies have tried to link this perception with the underlying two-dimensional cephalometric data. Comparisons between patients’ subjective opinions and 3D objective assessment of facial morphology have not been performed. Aims: (1) To test the reliability of the 3D imaging system; (2) to determine the effect of orthognathic surgery on the 3D soft-tissue morphology; (3) to assess skeletal changes following orthognathic surgery; (4) to evaluate soft-tissue to hard-tissue displacement ratios; (5) to ascertain the impact of orthognathic surgery on patients’ perception of their facial appearance and their psychosocial characteristics, (6) to explore the dentofacial deformity, sex and age on the psychosocial characteristics; (7) to evaluate the extent of compatibility between the cephalometric and the three-dimensional measurements and (8) to determine if the magnitude of facial soft-tissue changes affects the perception of facial changes at six months following surgery. Results and Conclusions: C3D imaging system was proved to be accurate with high reproducibility. The reproducibility of landmark identification on 3D models was high for 24 out of the 34 anthropometric landmarks (SD£0.5 mm). One volumetric algorithm in the Facial Analysis Tool had an acceptable accuracy for the assessment of volumetric changes following orthognathic surgery (mean error=0.314 cm3). The error of cephalometric method was low and the simulation of mandibular closure proved to be reproducible. 2D soft-tissue measurements were compatible with 3D measurements in terms of distances, but angular measurements showed significant differences (p<0.05)

Morphologic outcome of bimaxillary surgery–An anthropometric appraisal

Objectives: To adequately perform orthognathic surgery procedures, it is from basic interest to understand the morphologic changes caused by orthognathic surgery. Anthropometric analyses of standardized frontal view and profile photographs could help to investigate and understand such changes. Study Design: We present a pre- to postoperative evaluation of orthognathic surgery results based on anthropometric indices described by Farkas and cephalometric measurements. 30 Class III patients undergoing maxillary advancement by Le Fort I Osteotomy and mandibular setback by bilateral sagittal split osteotomy were evaluated. Preoperative as well as three and nine months postoperative lateral cephalograms as well as standardized frontal view and profile photographs were taken. On the photographs 21 anthropometric indices given by Farkas were evaluated. In cephalograms SNA and SNB angle as well as Wits appraisal were investigated. Results: The investigated anthropometric indices showed a significant increase of the vertical height of the upper lip without changing the relation of the upper vermilion to the cutaneous upper lip. The lower vermilion height increased relatively to the cutaneous lower lip without vertical changes in the lower lip. Due to maxillary advancement the upper face height increased meanwhile the lower face height decreased due to mandibular setback. SNA and SNB angle and Wits appraisal showed typical changes related to surgery. Conclusions: The investigated photo-assisted anthropometric measurements presented reproducible results related to bimaxillary surgery

Evaluation of the esthetic results of a 40-patient group treated surgically for dentoskeletal class III malocclusion

A dentoskeletal Class III malocclusion results in unesthetic alterations of the soft tissues, which may cause psychologic and interpersonal problems. Surgical treatment, if based on cephalometric evaluations alone, can result in inadequate correction of facial esthetics. The aim of this paper is to discuss the esthetic needs observed in surgical planning of a group of 40 Class III patients and to compare the presurgical esthetic parameters with those recorded in the sixth month of follow-up. To obtain the proper esthetic result and to restore proper stomatognathic functionality, surgical treatment planning required the integration and correction of skeletal cephalometric planning. In 24 of the 40 patients, the skeletal and esthetic planning were in agreement with each other. In the remaining 16 patients, the correction of skeletal planning with the esthetic planning was necessary to obtain the correct esthetic and functional restoration. In all patients, esthetic, radiographic, and functional analysis at the sixth month of follow-up revealed the restoration of correct facial esthetics in the vertical, transverse, and sagittal planes; no temporomandibular joint problems; and a high degree of personal satisfaction regarding the esthetic and functional result obtained, including improvements in social life and in masticatory function. Cephalometric indications should always be compared with esthetic clinical indications and, possibly, the skeletal planning must be corrected by the esthetic needs, so that esthetic and functional success can be reached at the same time

Changes of the Posterior Airway Space Following Orthognathic Surgery in Class III

Objective: Adaptation of the pharyngeal airway space does occur after different surgical strategies of class III patients including mandibular setback, maxillary advancement and bimaxillary surgery. The aim of this study is to conduct a detailed cephalometric evaluation of the alterations taking place in the morphology of the pharyngeal airway space after treatment of class III skeletal deformity via different surgical procedures (i.e. mandibular setback, maxillary advancement, bimaxillary surgery) in both males and females.Methods: This study is a before-after cross sectional retrospective research. One hundred and twenty consecutive patients who were diagnosed as having skeletal class III deformity. All patients included in this study were adults who had completed their growth and had cephalograms within a month  prior to operation (T1) and 1 month to 9 months post-surgery (T2) taken in the natural head position. Patients were divided according to the type of surgery undertaken in three groups: group 1 (bimaxillary), group 2 (mandibular setback) and group 3 (maxillary advancement) surgeries. Posterior airway size was evaluated at both T1 and T2 in each group. The results were compared by paired t and one-way ANOVA tests.Results: Airway size decreased significantly in group 1 and 2 (p&lt;0.05) but increased in group 3(p&lt;0.05).Conclusion: Airway dimension and morphology as well as head and neck posture changed significantly in different surgical treatments of class III deformity