Variación de la dimensión del espacio orofaríngeo después de la cirugía de retroceso mandibular en pacientes con deformidad dentofacial clase III / Variation in the oropharyngeal space after mandibular setback surgery in class III malocclusion patients

OBJETIVOS: Comparar la variación de la dimensión del espacio orofaríngeo (EO) en el prequirúrgico, postquirúrgico inmediato y postquirúrgico de 5 a 24 meses después de la cirugía de retroceso mandibular (CRM). MATERIALES Y MÉTODOS: Se evaluaron las radiografías cefalométricas prequirúrgicas, postquirúrgicas inmediatas y postquirúrgicas de 5 a 24 meses de 20 pacientes con CRM del Servicio de Cirugía Oral y Maxilofacial de dos instituciones. Se cuantificó la dimensión del EO en diferentes momentos. RESULTADOS: No se encontraron diferencias de significación entre la cantidad de retroceso mandibular y la variación de la dimensión del EO. CONCLUSIONES: Existe una leve disminución de la dimensión del EO después de la CRM. No son estadísticamente significantes entre los momentos de evaluación. No se encontró correlación entre el retroceso mandibular y la disminución del EO

OBJECTIVE: The aim of this study was to compare the variation in the size of the oropharyngeal space (OS) in the preoperative, immediate postoperative and post-operative 5 to 24 months according to the amount of mandibular setback. MATERIAL AND METHOD: Variation were evaluated on cephalometric radiographs taken few days before the surgery (Rx1), immediate postoperative (Rx2) and postoperative long time (5 to 24 months) (Rx3). The subjects were 20 patients (18 - 36 years) in whom dentofacial deformity class III was corrected by bilateral sagittal split ramus osteotomy setback. Surgery was done in two Oral and Maxillofacial specialized institutions, since 2003 to 2010. We examined the size of the oropharyngeal space at different times before and after mandibular setback surgery. RESULTS: These shows no significant difference between the amount of mandibular setback and decrease the size of the oropharyngeal space. It was determined that the oropharyngeal space immediately after surgery increases and decreases over time as a result of soft and hard tissue adaptation. CONCLUSIONS: We conclude that there is a slight decreased in the anteroposterior dimension of oropharynx after mandibular setback surgery, however the variations is no statistically significant difference between the moments of evaluation (the amount of mandibular recoil and the decrease in OS)

A systematic review of soft-to-hard tissue ratios in orthognathic surgery. Part III: Double jaw surgery procedures.

OBJECTIVE: The aim was to determine the soft-to-hard tissue ratios in profile view in bimaxillary orthognathic surgical corrections. MATERIAL AND METHODS: A systematic review of studies published in different languages was performed by searching the Medline, Embase, Cochrane Library, Lilacs, Scopus, and Science Direct databases up to August 2015. Additional studies were identified by reference analyses. The methodological quality was evaluated using the instrument developed by the Effective Public Health Practice Project and the Level of Evidence using the Level of Evidence scale from the Oxford Centre for Evidence-based Medicine. RESULTS: The search identified 16 articles; one of which was included from the manual reference search. The analysis of bias revealed weak methodological quality for all the studies included (LOE IV). The studies were retrospective and presented widely varying ratios. In sagittal movements Sn:ANS showed consistency in the evaluations with 60%-90% ratios in five articles. Pn:A presented 66%-90% when V-Y suturing is executed and Ls:U1 ratio was 60%-100% in 6 articles. In vertical direction, poor data are available, considering Sn:A between 54% and 91% in 3 articles and Ls:U1 between 66% and 97% in 3 articles. The Mla-to-point B ratio in sagittal movements was 100% in six articles and Pg-to-sPg demonstrated a relationship between 90% and 100% in 8 articles. CONCLUSION: Soft-to-hard tissue ratios varied greatly in literature. The results for the mentolabial angle and soft Pogonion changes were apparently more uniform. The low LOE of the studies prevented a more in-depth analysis.

Virtual surgical planning for orthognathic surgery using digital data transfer and an intraoral fiducial marker: the charlotte method.

PURPOSE: We describe an alternative workup protocol for virtual surgical planning of orthognathic surgery using an intraoral fiducial marker, clinical photography, and the digital transfer of occlusal data. We also discuss our initial experience using this protocol in a series of patients. PATIENTS AND METHODS: A retrospective cohort study was performed of consecutive patients who had undergone combined maxillary and mandibular osteotomies for the correction of dentofacial deformities at 1 center. These patients underwent treatment planning using the modified virtual surgical planning protocol described in the present report. The primary outcome evaluated was the accuracy of the method, which was determined through superimposition of the surgical plan to the postoperative cone-beam computed tomography (CBCT) scan. The secondary outcomes included the accuracy of the natural head position readings and the adequacy of the CBCT scanned stone models for the fabrication of occlusal splints. RESULTS: The population included 25 patients. The root mean standard deviation (RMSD) from the preoperative plan to the postoperative scan at the maxillary cephalometric points was 1.2, 1.4, and 2.1 mm in the axial, sagittal, and coronal planes, respectively. The RMSD of the superimposed plan to the postoperative scan at the 3 mandibular cephalometric points was 1.2, 0.8, and 0.7 mm in the axial, sagittal, and coronal planes, respectively. The average variance from the axial, sagittal, and coronal planes for the natural head position was 0.05, 2.22, and 0.69 mm, respectively. All splints fabricated from the CBCT occlusal data fit the stone models and were used intraoperatively. In the subset of patients whose models were both digitally transferred and laser scanned, the superimposition of the laser scan data to the CBCT scanned data was found to have a maximum variation of 0.2 mm at the occlusal level. CONCLUSIONS: The use of an intraoral fiducial marker changed the workflow for the data collection needed for virtual surgical planning of the correction of dentofacial deformities, while still obtaining accurate results. Because the device does not cause lip distortion, the possibility of virtually predicting a more expectant postoperative lip position exists without the need for additional scans. Furthermore, this work flow allows the transfer of data to be isolated to digital media.

Accuracy of three-dimensional soft tissue simulation in bimaxillary osteotomies.

The purpose of this study was to evaluate the accuracy of an algorithm based on the mass tensor model (MTM) for computerized 3D simulation of soft-tissue changes following bimaxillary osteotomy, and to identify patient and surgery-related factors that may affect the accuracy of the simulation. Sixty patients (mean age 26.0 years) who had undergone bimaxillary osteotomy, participated in this study. Cone beam CT scans were acquired pre- and one year postoperatively. The 3D rendered pre- and postoperative scans were matched. The maxilla and mandible were segmented and aligned to the postoperative position. 3D distance maps and cephalometric analyses were used to quantify the simulation error. The mean absolute error between the 3D simulation and the actual postoperative facial profile was 0.81 ± 0.22 mm for the face as a whole. The accuracy of the simulation (average absolute error ≤2 mm) for the whole face and for the upper lip, lower lip and chin subregions were 100%, 93%, 90% and 95%, respectively. The predictability was correlated with the magnitude of the maxillary and mandibular advancement, age and V-Y closure. It was concluded that the MTM-based soft tissue simulation for bimaxillary surgery was accurate for clinical use, though patients should be informed of possible variation in the predicted lip position.

A more accurate soft-tissue prediction model for Class III 2-jaw surgeries.

INTRODUCTION: The use of bimaxillary surgeries to treat Class III malocclusions makes the results of the surgeries more complicated to estimate accurately. Therefore, our objective was to develop an accurate soft-tissue prediction model that can be universally applied to Class III surgical-orthodontic patients regardless of the type of surgical correction: maxillary or mandibular surgery with or without genioplasty. METHODS: The subjects of this study consisted of 204 mandibular setback patients who had undergone the combined surgical-orthodontic correction of severe skeletal Class III malocclusions. Among them, 133 patients had maxillary surgeries, and 81 patients received genioplasties. The prediction model included 226 independent and 64 dependent variables. Two prediction methods, the conventional ordinary least squares method and the partial least squares (PLS) method, were compared. When evaluating the prediction methods, the actual surgical outcome was the gold standard. After fitting the equations, test errors were calculated in absolute values and root mean square values through the leave-1-out cross-validation method. RESULTS: The validation result demonstrated that the multivariate PLS prediction model with 30 orthogonal components showed the best prediction quality among others. With the PLS method, the pattern of prediction errors between 1-jaw and 2-jaw surgeries did not show a significantly difference. CONCLUSIONS: The multivariate PLS prediction model based on about 30 latent variables might provide an improved algorithm in predicting surgical outcomes after 1-jaw and 2-jaw surgical corrections for Class III patients.

Symptomatic venous thromboembolism in orthognathic surgery and distraction osteogenesis: a retrospective cohort study of 4127 patients.

Venous thromboembolism is a common postoperative complication, and orthopaedic procedures are particularly at risk. We designed a retrospective, single centre, observational, cohort study of 4127 patients (mean (SD) age 27 (11) years) who had elective orthognathic operations or distraction osteogenesis between January 1970 and February 2012 at the VU University Medical Centre, Amsterdam, to investigate the incidence in this group over the 42-year period, 2 patients developed symptomatic venous thromboembolism (1 woman had a deep vein thrombosis (DVT) and 1 man had a DVT and pulmonary embolus) postoperatively. In relatively young patients with low to moderate risk factors and short hospital stay this type of operation is associated with a particularly low risk of developing thrombosis. It could be advisable to limit the use of thromboprophylaxis to patients at high risk or according to hospital guidelines.

A better statistical method of predicting postsurgery soft tissue response in Class II patients.

OBJECTIVE: To propose a better statistical method of predicting postsurgery soft tissue response in Class II patients. MATERIALS AND METHODS: The subjects comprise 80 patients who had undergone surgical correction of severe Class II malocclusions. Using 228 predictor and 64 soft tissue response variables, we applied two multivariate methods of forming prediction equations, the conventional ordinary least squares (OLS) method and the partial least squares (PLS) method. After fitting the equation, the bias and a mean absolute prediction error were calculated. To evaluate the predictive performance of the prediction equations, a leave-one-out cross-validation method was used. RESULTS: The multivariate PLS method provided a significantly more accurate prediction than the conventional OLS method. CONCLUSION: The multivariate PLS method was more satisfactory than the OLS method in accurately predicting the soft tissue profile change after surgical correction of severe Class II malocclusions.

Longitudinal trends in discharge patterns of orthognathic surgeries: is there a regionalization of procedures in teaching hospitals?

OBJECTIVE: The aim of this study was to determine if there is regionalization of orthognathic surgeries to teaching hospitals during the study period. STUDY DESIGN: The Nationwide Inpatient Sample for years 2000-2008 was used. Every hospitalization that had an orthognathic surgery was selected. Patient and hospital level variables were examined. The odds of an orthognathic surgery procedure being performed in a teaching hospital over the study period was computed with the use of a multivariable logistic regression model. RESULTS: During the study period, a total of 108,264 hospitalizations underwent orthognathic surgeries in the United States. The average age ranged from 27 years during the years 2006-2008 to 28.2 years during the years 2000-2002. After adjusting for multiple patient and hospital level factors, the year of procedure was not a significant predictor of increasing odds of an orthognathic surgery being performed in a teaching hospital. CONCLUSIONS: There is no evidence of concentration of orthognathic surgical procedures in teaching hospitals.