Positioning In Orthognathic Surgery Research Articles

A CAD/CAM Maxillary Guiding for Osteotomy, Drilling and Maxillary Positioning in Orthognathic Surgery: Accuracy Analysis.

A CAD/CAM Maxillary Guiding for Osteotomy, Drilling and Maxillary Positioning in Orthognathic Surgery: Accuracy Analysis.

Custom made cutting guides and osteosynthesis plates versus CAD/CAM occlusal splints in positioning and fixation of the maxilla in orthognathic surgery: A prospective randomized study

The aim of this study is to compare the accuracy of maxilla positioning in orthognathic surgery with the use of custom-made devices (cutting guides and patient-fitted osteosynthesis plates) comparing to CAD/CAM splints.A prospective randomized study was performed. Patients with dentofacial deformities undergoing orthognathic surgery were compared, using customized guides (experimental group) vs. CAD/CAM surgical splints (control group) for the repositioning of the upper maxilla. Preoperative and postoperative CT scans were used to compare positioning and fixation of the maxilla in the three planes of space.A total of 30 patients were included in the study (15 patients in each study group). The mean error obtained with customized guides was 0.8 mm (range 0.1–1.9) in the anterior-posterior axis, 0.4 mm (range 0–1.4) in the vertical axis and 0.2 mm (range 0–1.1) in the horizontal axis. There were statistically significant differences in the anterior-posterior and vertical axes in favour of the customized implants, whereas there were no differences in the horizontal plane. Furthermore, there was a mean reduction of the operative time of 36.5 min in the experimental group.Within the limitations of the study it seems that patient specific surgical guides should be preferred when accuracy of repositioning of the maxilla and saving operative time are the priority.

Robot-Assisted Maxillary Positioning in Orthognathic Surgery: A Feasibility and Accuracy Evaluation.

Several methods enabling independent repositioning of the maxilla have been introduced to reduce intraoperative errors inherent in the intermediate splint. However, the accuracy is still to be improved and a different approach without time-consuming laboratory process is needed, which can allow perioperative modification of unoptimized maxillary position. The purpose of this study is to assess the feasibility and accuracy of a robot arm combined with intraoperative image-guided navigation in orthognathic surgery. The experiments were performed on 12 full skull phantom models. After Le Fort I osteotomy, the maxillary segment was repositioned to a different target position using a robot arm and image-guided navigation and stabilized. Using the navigation and the postoperative computed tomography (CT) images, the achieved maxillary position was compared with the planned position. Although the maxilla showed mild displacement during the fixation, the mean absolute deviations from the target position were 0.16 mm, 0.18 mm, and 0.20 mm in medio-lateral, antero-posterior, and supero-inferior directions, respectively, in the intraoperative navigation. Compared with the target position using postoperative CT, the achieved maxillary position had a mean absolute deviation of less than 0.5 mm for all dimensions and the mean root mean square deviation was 0.79 mm. The results of this study suggest that the robot arm combined with the intraoperative image-guided navigation may have great potential for surgical plan transfer with the accurate repositioning of the maxilla in the orthognathic surgery.

Accuracy of Splintless Maxillary Positioning in Orthognathic Surgery Using Patient-Specific Titanium Plates

Orthognathic surgery has traditionally been performed using stone model surgery. This process, with its multitude of laboratory steps, may be fraught with inaccuracies. Small errors in this process can get magnified downstream, resulting in altered maxillary and ultimately mandibular position and outcomes. With the advent of new technology, patient-specific maxillary cutting guides with predictive plate holes and 3D-printed plates have allowed surgeons to position the maxilla solely based on the patient-specific guide and plate. This eliminates the need for vertical reference markings, intermediate splints, and positioning the maxilla relative to the mandible. As this technology is relatively new, the goal of this study is to evaluate the accuracy of patient-specific surgical guides and plates in maxillary positioning at our institution.

A new approach in three dimensions to define pre- and intraoperative condyle–fossa relationships in orthognathic surgery – is there an effect of general anaesthesia on condylar position?

Incorrect registration of the condylar position in orthognathic surgery is supposed to cause postoperative relapse, condylar resorption and temporomandibular disorders. The aim of this prospective study was to evaluate the influence of general anaesthesia on centric relation (CR). Therefore, CR registered preoperatively in the awake patient and CR registered intraoperatively under general anaesthesia were recorded in 30 patients (14 men, 16 women) undergoing orthognathic surgery (skeletal class I: n=3, II: n=13, III: n=14; symmetric: n=20; asymmetric: n=10). CR records were digitized and, through superimposition on the preoperative cone beam computed tomography of the patient's skull, the superior, anterior and posterior joint space and the volumetric congruence of 120 condyles were analysed. The linear measurements of joint spaces did not demonstrate any clinically relevant discrepancy between the CR measured in the awake and anaesthetized patient. In contrast, volumetric analysis revealed statistically significant differences between both states, with an intraoperative condylar sag predominantly in the posterior–inferior direction. The patient’s skeletal class or symmetry had no significant influence on the intraoperative condylar displacement. Thus, the risk of fixing the condyle in an unphysiological position supports the idea of using intraoperative condylar positioning devices to achieve predictable and stable outcomes.

Clinical comparison of two external anatomical references for maxillary positioning in orthognathic surgery

espanolIntroduccion: El uso de puntos de referencia externos (ERP) como el pin nasal (NP) y el canto medial del ojo (EMC) proporciona puntos de referencia estables y reproducibles para el reposicionamiento maxilar. Los ERP son ampliamente utilizados por su practicidad para lograr el resultado estetico deseado en cirugia ortognatica (OS). Objetivos: El proposito de este estudio es comparar los ERP (NP y EMC), para definir cual es el mas preciso, y tambien definir sus limitaciones, en la fase intraoperatoria para el reposicionamiento vertical del maxilar. Pacientes y metodos: Realizamos un estudio retrospectivo en 26 pacientes que se sometieron a OS desde diciembre de 2015 hasta agosto de 2018. Antes de la osteotomia de Le Fort I, se realizaron las mediciones verticales. Se considero el ERP mas preciso el que obtuvo la menor diferencia promedio entre la medicion vertical de la planificacion prequirurgica y la obtenida en el periodo intraoperatorio. Resultados: El movimiento vertical planeado fue un promedio de -1,73 mm ± 1,97 SD, con el mayor movimiento de impactacion maxilar de -6 mm y el mayor descenso maxilar de 2 mm. La diferencia entre el movimiento vertical planificado y las medidas obtenidas de cambio vertical para NP tuvo un promedio de 0,05 mm ± 0,51 DE (IC 95 %, -0,15 - 0,26), y la diferencia entre el movimiento vertical planificado y las medidas obtenidas para EMC tuvo un promedio de 1,23 mm ± 1,29 DE (IC 95 %, 0,71 - 1,75), con una diferencia estadisticamente significativa (p = 0,0001) entre ellos de -1,18 mm ± 1,23 (IC 95 %, -1,67 - -0,68). Conclusiones: El uso del NP como ERP proporciona mayor precision y previsibilidad del movimiento en el reposicionamiento vertical del complejo maxilomandibular, en comparacion con el uso de EMC. Ambas tecnicas se pueden utilizar como complemento, teniendo en cuenta el efecto de la triangulacion. EnglishIntroduction: The use of external reference points (ERP) like the nasal pin (NP) and eye's medial canthus (EMC) provides a stable and reproductible landmarks for maxillary repositioning. ERP are widely used, for its practicality to achieve the desired aesthetic result in orthognathic surgery (OS). Objectives: The purpose of this study is to compare the ERPs: NP and EMC, to define which is the most accurate, and also define its limitations, in the intraoperative phase for vertical repositioning of the maxilla. Patients and methods: We performed a retrospective study on 26 patients who underwent OS from December 2015 to August 2018. Previous to the Le Fort I osteotomy, the vertical measurements were made. The most accurate ERP was considered to be the one that obtained the least average difference between the vertical measurement of the pre-surgical planning and that obtained in the intraoperative period. Results: The planned vertical movement was an average of -1.73 mm ± 1.97 SD, with the largest maxillary impaction movement of -6 mm and the largest maxillary descent of 2 mm. The difference between planned vertical movement and obtained measurements of vertical change for NP had an average 0.05 mm ± 0.51 SD (95 % CI, -0.15 - 0.26), and the difference between planned vertical movement and obtained measurements for EMC had an average 1.23 mm ± 1.29 SD (95 % CI, 0.71 - 1.75), with a statistically significant difference (p = 0.0001) between them of -1.18 mm± 1.23 (95 % CI, -1.67 - -0.68). Conclusions: The use of the NP as an ERP provides greater precision and predictability of movement in the vertical repositioning of the maxillomandibular-complex, compared to the use of EMC. Both techniques can be used as a complement, being aware of the effect of triangulation.

Contribuição topográfica do forame e língula mandibular em procedimentos cirúrgicos no ramo da mandíbula

Objetivo: analisar a topografia e biometria do forame mandibular e da lingula mandibular em crânios secos para verificar sua variabilidade e determinar suas posições topográficas. Material e Método: Para analisar as distâncias, foram realizadas medições utilizando um paquímetro digital Mitutoyo® devidamente calibrado para coletar a distância em milímetros, do centro do forame até as quatro margens (anterior, posterior, superior e inferior) do ramo mandibular (N = 176). Realizamos as medidas do forame mandibular em milímetros para determinar sua geometria externa. A lingula mandibular (N = 76) foi estudada quanto à sua localização topográfica e forma quando sua estrutura é preservada. Todos os dados foram documentados em um protocolo de coleta de dados com o objetivo de desenhar diagramas esquemáticos e arquivar as fotografias dos casos e a análise dos resultados. Resultados: em relação à frequência, o forame estava presente em todos os casos (100%), em ambos os lados da superfície medial do nervo mandibular. O número de forames de cada lado é único: foram observados 175 casos (99,5%). Apenas um forame (0,5%) era o dobro do lado direito. Em relação à sua posição em relação às margens da mandíbula, na maioria delas, está localizada próxima à margem inferior, variando entre 9,6 mm e 39,1 mm, com média de 26,0 mm. A margem posterior da mandíbula variou entre 6,8 mm e 24,0 mm, com média de 12,30 mm. A lingula mandibular dos maxilares foi analisada em 32 maxilares (64 casos), com formato triangular (55%), presente na maioria dos casos (86%) e posição ântero-superior em 43% deles. Conclusões: o forame mandibular é um elemento anatômico importante para o sucesso da técnica de bloqueio do nervo alveolar inferior. Sua estrutura acessória, a lingula mandibular, é uma posição de referência em cirurgia ortognática; devido à sua localização e aspecto, serve como um escudo protetor para o feixe neurovascular alveolar inferior

Customized Three-Dimensional Printing Spacers for Bone Positioning in Orthognathic Surgery for Correction and Prevention of Facial Asymmetry.

Orthognathic surgery is a powerful tool for correction of facial asymmetry and malocclusion. The goal is to achieve good dental function and facial aesthetics. Three-dimensional simulation is used for surgical planning, and bone gaps could be created to achieve facial balance. In this study, customized "spacers" were made using computer-aided design and three-dimensional printing for guides for use during surgery. With the final three-dimensional plan, the skull images were exported to 3-Matic software, where spacers were designed according to the bone gaps. Three-dimensionally-printed spacers were made and used to facilitate positioning and fixation. Consecutive patients with facial asymmetry were recruited in this prospective study. The postoperative outcome was assessed using a visual analogue scale and the three-dimensional facial surface area discrepancy index for subjective and objective evaluation. There were 12 patients and a total of 19 spacers for the Le Fort I and mandibular ramus segments. The spacers worked nicely during the bone fixation process. Mean preoperative and postoperative visual analogue scale scores were 4.83 and 7.14, with a statistically significant improvement for facial symmetry (p = 0.018). Mean preoperative and postoperative facial surface area discrepancy index was 0.95 and 0.98, and the correction of asymmetry was significant (p = 0.009). There were no related surgical complications. All patients were satisfied with the correction of facial asymmetry and malocclusion. The custom-made, three-dimensionally-printed spacers help to achieve surgical precision to correct and prevent facial asymmetry in orthognathic surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Therapeutic, IV.

Evaluation of Andrews’ Analysis As a Predictor of Ideal Sagittal Maxillary Positioning in Orthognathic Surgery

There is no universally accepted method for determining the ideal sagittal position of the maxilla in orthognathic surgery. In “Element II” of “The Six Elements of Orofacial Harmony,” Andrews used the forehead to define the goal maxillary position. The purpose of this study was to compare how well this analysis correlated with postoperative findings in patients who underwent bimaxillary orthognathic surgery planned using other guidelines. We hypothesized that the Andrews analysis would more consistently reflect clinical outcomes than standard angular and linear measurements.

Maxillary Sagittal Position in Relation to the Forehead: A Target for Orthognathic Surgery.

The relationship of the maxillary incisor to forehead position and angulation may be a predictor for the esthetic antero-posterior maxillary position in orthognathic surgery, but this has not been fully explored in the existing literature. Additionally, this analysis requires a lateral smiling photograph, which is not typically included in orthodontic/orthognathic records. This is a bidirectional study of Caucasian orthodontic patients with malocclusions correctable with nonsurgical and nonextraction treatment. Subjects for Group 1 were enrolled prospectively and records included a lateral smiling photograph. Group 2 patients were collected retrospectively with standard records. The analysis described in Andrews' Element II of The Six Elements of Orofacial Harmony was applied to the smiling photographs for Group 1, resulting in "Incisor- goal anterior limit line (GALL)" measurements. A modified analysis utilizing cephalometric tracings was applied for both the groups, and the results were compared. Forty-nine subjects with mean age 11.8 ± 1.2 years were included (n = 14 for Group 1, n = 35 for Group 2). Mean Incisor-GALL distances were 3.71 ± 5.39 mm for females and 4.47 ± 5.06 mm for males. Correlation between analyses was excellent (intraclass correlation coefficient = 0.872). In conclusion, a modified approach to measuring the Incisor-GALL distance using standard orthodontic records correlated closely with the analysis described by Andrews. Normal values for this measurement are presented for Caucasian patients.

Evaluation of Andrews' Analysis as a Predictor of Ideal Sagittal Maxillary Positioning in Orthognathic Surgery

There is no universally accepted method for determining the ideal sagittal position of the maxilla in orthognathic surgery. In "Element II" of "The Six Elements of Orofacial Harmony," Andrews used the forehead to define the goal maxillary position. The purpose of this study was to compare how well this analysis correlated with postoperative findings in patients who underwent bimaxillary orthognathic surgery planned using other guidelines. The authors hypothesized that the Andrews analysis would more consistently reflect clinical outcomes than standard angular and linear measurements. This is a retrospective cohort study of patients who had bimaxillary orthognathic surgery and achieved an acceptable esthetic outcome. Patients with no maxillary sagittal movement, obstructive sleep apnea, cleft or craniofacial diagnoses, or who were non-Caucasian were excluded. Treatment plans were developed using photographs, radiographs, and standard cephalometric measurements. The Andrews analysis, measuring the distance from the maxillary incisor to the goal anterior limit line, and standard measurements were applied to end-treatment records. The Andrews analysis was statistically compared with standard methods. There were 493 patients who had orthognathic surgery from 2007 through 2014, and 60 (62% women; mean age, 22.1±6.8yr) met the criteria for inclusion in this study. The mean Andrews distances were -4.8±2.9mm for women and -8.6±4.6mm for men preoperatively and -0.6±2.1mm for women and -1.9±3.4mm for men postoperatively. For women, the Andrews analysis was closer to the goal value (0mm) postoperatively than any standard measurement (P<.001). For men, the linear distance from the A point to a vertical line tangent to the nasion from the McNamara analysis performed best (P<.001), followed by the Andrews analysis. The Andrews analysis correlated well with the final esthetic sagittal maxillary position in the present sample, particularly for women, and could be a useful tool for orthognathic surgical planning.

Systematic three-dimensional analysis of wafer-based maxillary repositioning procedures in orthognathic surgery

PurposeLittle is known about the three-dimensional (3D) transfer accuracy in maxillary repositioning procedures based on conventionally manufactured dental-mounted wafers. The purpose of the present study was a systematic 3D analysis for wafer-based maxillary positioning in orthognathic surgery. Materials and methodsA total of 92 patients underwent Le Fort I in addition to mandibular bilateral sagittal split osteotomies (BSSO). Alignment of the pre- and postsurgical CBCT data sets allowed measuring maxillary position changes in axial, sagittal and transversal directions. ResultsThe highest achieved absolute transfer inaccuracies were 1.37 mm, ±0.84 in the sagittal direction, followed by 1.15 mm, ±0.69 in the axial, as well as 1.05 mm, ±0.79 in the transversal direction. The largest relative deviations could be found for repositions in the transversal plane (109.4%, ±4.5), followed by the axial (66.2%, ±51.5) and sagittal plane (49.3%, ±2.2). Significant transfer accuracy differences of repositioning procedures in the sagittal direction, mainly advancement procedures, could be detected if performed with (1.75 mm, ±0.90) or without (1.18 mm, ±0.78) additional rotational correction component. No significant differences were found between unidirectional and multidirectional maxillary correction procedures. ConclusionThe present study for the first time delivers systematic 3D accuracy data of wafer-based maxillary positioning procedures, attesting to its feasibility but also further encouraging the search for improvement strategies.

Condylar positioning in orthognathic surgery – a pilot study

Condylar positioning in orthognathic surgery – a pilot study

A novel navigation system for maxillary positioning in orthognathic surgery: Preclinical evaluation.

Appropriate positioning of the maxilla is critical in orthognathic surgery. As opposed to splint-based positioning, navigation systems are versatile and appropriate in assessing the vertical dimension. Bulk and disruption to the line of sight are drawbacks of optical navigation systems. Our aim was to develop and assess a novel navigation system based on electromagnetic tracking of the maxilla, including real-time registration of head movements. Since the software interface has proved to greatly influence the accuracy of the procedure, we purposely designed and evaluated an original, user-friendly interface. A sample of 12 surgeons had to navigate the phantom osteotomized maxilla to eight given target positions using the software we have developed. Time and accuracy (translational error and angular error) were compared between a conventional and a navigated session. A questionnaire provided qualitative evaluation. Our system definitely allows a reduction in variability of time and accuracy among different operators. Accuracy was improved in all surgeons (mean terror difference = 1.11 mm, mean aerror difference = 1.32°). Operative time was decreased in trainees. Therefore, they would benefit from such a system that could also serve for educational purposes. The majority of surgeons who strongly agreed that such a navigation system would prove very helpful in complex deformities, also stated that it would be helpful in everyday orthognathic procedures.

A hypothesis on the desired postoperative position of the condyle in orthognathic surgery: a review

It is very important to clarify the relationship between a dentofacial structure and a temporomandibular joint (TMJ) structure in orthognathic surgery. Recently, it was reported that the skeletal and occlusal patterns were associated with the TMJ morphology, including the disk position. In orthognathic surgery, some surgeons state that alterations in the condylar position from surgery can lead to malocclusion associated with the risk of early relapse, and also favor the development of temporomandibular disorders. For these reasons, several positioning devices have been proposed and applied, but now there is no scientific evidence to support the use of condylar positioning devices. There are some reasons why scientific evidence cannot be obtained; however, it also includes the question of whether the preoperative position of the condyle is the desired postoperative position. The purpose of this study was to verify the desired condylar position in orthognathic surgery, based on literature on the postoperative condylar position in orthognathic surgery. From the studies reviewed, it was suggested that the preoperative position of the condyle was not the desired postoperative position in orthognathic surgery.

3D Analysis of Condylar Position after Sagittal Split Osteotomy of the Mandible in Mono- and Bimaxillary Orthognathic Surgery – a Methodology Study in 18 Patients

This study analyzes the condylar position with intercondylar distance and angle after sagittal split osteotomy in mono- and bimaxillary orthognathic surgery applying cone-beam computed tomography (CBCT) images before and after surgery. Data of 18 patients, ten males (mean age 28 years) and eight females (mean age 26 years) undergoing the described surgery between 2008 and 2009 were analyzed. CBCT scans were performed with the KaVo 3DeXam (KaVo, Biberach/ Riß, Germany) (identical with the iCAT scan device) before and after surgery. The exported DICOM data were analyzed with ImageJ morphometry software. Patients were also asked about TMJ problems. The two-tailed t test was used and significance was set at a p value less than p = 0.05. There was no significant difference between the pre- and postoperative distances between condylar centers (mean difference: 1 mm) (p = 0.69) and intercondylar angle (mean difference: 6.6°) (p = 0.27). CBCT is a novel imaging technique appropriate for detailed and three-dimensional analysis of the condylar position in orthognathic surgery. Available freeware analysis software can be applied for metrical measurements. Our cases showed no significant changes of condylar position immediately after surgery without intraoperative condylar fixation.

O.416 Supraforaminal mandible osteotomy with condyle positioning

Incorrect registration of the condylar position in orthognathic surgery is supposed to cause postoperative relapse, condylar resorption and temporomandibular disorders. The aim of this prospective study was to evaluate the influence of general anaesthesia on centric relation (CR). Therefore, CR registered preoperatively in the awake patient and CR registered intraoperatively under general anaesthesia were recorded in 30 patients (14 men, 16 women) undergoing orthognathic surgery (skeletal class I: n = 3, II: n = 13, III: n = 14; symmetric: n = 20; asymmetric: n = 10). CR records were digitized and, through superimposition on the preoperative cone beam computed tomography of the patient's skull, the superior, anterior and posterior joint space and the volumetric congruence of 120 condyles were analysed. The linear measurements of joint spaces did not demonstrate any clinically relevant discrepancy between the CR measured in the awake and anaesthetized patient. In contrast, volumetric analysis revealed statistically significant differences between both states, with an intraoperative condylar sag predominantly in the posterior–inferior direction. The patient’s skeletal class or symmetry had no significant influence on the intraoperative condylar displacement. Thus, the risk of fixing the condyle in an unphysiological position supports the idea of using intraoperative condylar positioning devices to achieve predictable and stable outcomes.

Intraoperative Fluoroscopic Verification of Condylar Position in Orthognathic Surgery

Intraoperative Fluoroscopic Verification of Condylar Position in Orthognathic Surgery

Application of an augmented reality tool for maxillary positioning in orthognathic surgery – A feasibility study

An augmented reality tool for computer assisted surgery named X-Scope allows visual tracking of real anatomical structures in superposition with volume rendered CT or MRI scans and thus can be used for navigated translocation of bony segments. In a feasibility study X-Scope was used in orthognathic surgery to control the translocation of the maxilla after Le Fort I osteotomy within a bimaxillary procedure. The situation achieved was compared with the pre-operative situation by means of cephalometric analysis on lateral and frontal cephalograms. The technique was successfully utilized in 5 patients. Maxillary positioning using X-Scope was accomplished accurately within a range of 1mm. The tool was used in all cases in addition to the usual intra-operative splints. A stand-alone application without conventional control does not yet seem reasonable. Augmented reality tools like X-Scope may be helpful for controlling maxillary translocation in orthognathic surgery. The application to other interventions in cranio-maxillofacial surgery such as Le Fort III osteotomy, fronto-orbital advancement, and cranial vault reshaping or repair may also be considered.

Maintenance of the preoperative condyle position in orthognathic surgery

A bimaxillary osteotomy for mandibular prognathism and maxillary retrognathia was performed on 30 patients with an Angle Class III malocclusion. The Luhr condylar positioning device was used intraoperatively to reproduce the condylar position. Pre- and postoperative condylar positions were compared by recording joint movements with axiography. Steps, jags and jumps as symptoms of pathological joint function could not be identified. Only in one case could a pathological shortening of the joint track length be measured. This suggests that the Luhr device is effective in securing condyle position and therefore temporomandibular joint (TMJ) function. Pre- and postoperative axiography is an adequate method of controlling these results and a helpful supplement to the armentarium of orthognathic surgery.