Repositioning Of Maxilla Research Articles

Navigation in Orthognathic Surgery: 3D Accuracy

This article aims to determine the absolute accuracy of maxillary repositioning during orthognathic surgery according to simulation-guided navigation, that is, the combination of navigation and three-dimensional (3D) virtual surgery. We retrospectively studied 15 patients treated for asymmetric dentofacial deformities at the Oral and Maxillofacial Surgery Unit of the S.Orsola-Malpighi University Hospital in Bologna, Italy, from January 2010 to January 2012. Patients were scanned with a cone-beam computed tomography before and after surgery. The virtual surgical simulation was realized with a dedicated software and loaded on a navigation system to improve intraoperative reproducibility of the preoperative planning. We analyzed the outcome following two protocols: (1) planning versus postoperative 3D surface analysis; (2) planning versus postoperative point-based analysis. For 3D surface comparison, the mean Hausdorff distance was measured, and median among cases was 0.99 mm. Median reproducibility < 1 mm was 61.88% and median reproducibility < 2 mm was 85.46%. For the point-based analysis, with sign, the median distance was 0.75 mm in the frontal axis, -0.05 mm in the caudal-cranial axis, -0.35 mm in the lateral axis. In absolute value, the median distance was 1.19 mm in the frontal axis, 0.59 mm in the caudal-cranial axis, and 1.02 mm in the lateral axis. We suggest that simulation-guided navigation makes accurate postoperative outcomes possible for maxillary repositioning in orthognathic surgery, if compared with the surgical computer-designed project realized with a dedicated software, particularly for the vertical dimension, which is the most challenging to manage.

Surgical accuracy of three-dimensional virtual planning: a pilot study of bimaxillary orthognathic procedures including maxillary segmentation

This retrospective study evaluated the precision and positional accuracy of different orthognathic procedures following virtual surgical planning in 30 patients. To date, no studies of three-dimensional virtual surgical planning have evaluated the influence of segmentation on positional accuracy and transverse expansion. Furthermore, only a few have evaluated the precision and accuracy of genioplasty in placement of the chin segment. The virtual surgical plan was compared with the postsurgical outcome by using three linear and three rotational measurements. The influence of maxillary segmentation was analyzed in both superior and inferior maxillary repositioning. In addition, transverse surgical expansion was compared with the postsurgical expansion obtained. An overall, high degree of linear accuracy between planned and postsurgical outcomes was found, but with a large standard deviation. Rotational difference showed an increase in pitch, mainly affecting the maxilla. Segmentation had no significant influence on maxillary placement. However, a posterior movement was observed in inferior maxillary repositioning. A lack of transverse expansion was observed in the segmented maxilla independent of the degree of expansion.

Augmented reality as an aid in maxillofacial surgery: Validation of a wearable system allowing maxillary repositioning

AimWe present a newly designed, localiser-free, head-mounted system featuring augmented reality as an aid to maxillofacial bone surgery, and assess the potential utility of the device by conducting a feasibility study and validation. MethodsOur head-mounted wearable system facilitating augmented surgery was developed as a stand-alone, video-based, see-through device in which the visual features were adapted to facilitate maxillofacial bone surgery. We implement a strategy designed to present augmented reality information to the operating surgeon. LeFort1 osteotomy was chosen as the test procedure. The system is designed to exhibit virtual planning overlaying the details of a real patient. We implemented a method allowing performance of waferless, augmented-reality assisted bone repositioning. In vitro testing was conducted on a physical replica of a human skull, and the augmented reality system was used to perform LeFort1 maxillary repositioning. Surgical accuracy was measured with the aid of an optical navigation system that recorded the coordinates of three reference points (located in anterior, posterior right, and posterior left positions) on the repositioned maxilla. The outcomes were compared with those expected to be achievable in a three-dimensional environment. Data were derived using three levels of surgical planning, of increasing complexity, and for nine different operators with varying levels of surgical skill. ResultsThe mean error was 1.70 ± 0.51 mm. The axial errors were 0.89 ± 0.54 mm on the sagittal axis, 0.60 ± 0.20 mm on the frontal axis, and 1.06 ± 0.40 mm on the craniocaudal axis. The simplest plan was associated with a slightly lower mean error (1.58 ± 0.37 mm) compared with the more complex plans (medium: 1.82 ± 0.71 mm; difficult: 1.70 ± 0.45 mm). The mean error for the anterior reference point was lower (1.33 ± 0.58 mm) than those for both the posterior right (1.72 ± 0.24 mm) and posterior left points (2.05 ± 0.47 mm). No significant difference in terms of error was noticed among operators, despite variations in surgical experience. Feedback from surgeons was acceptable; all tests were completed within 15 min and the tool was considered to be both comfortable and usable in practice. ConclusionWe used a new localiser-free, head-mounted, wearable, stereoscopic, video see-through display to develop a useful strategy affording surgeons access to augmented reality information. Our device appears to be accurate when used to assist in waferless maxillary repositioning. Our results suggest that the method can potentially be extended for use with many surgical procedures on the facial skeleton. Further, our positive results suggest that it would be appropriate to proceed to in vivo testing to assess surgical accuracy under real clinical conditions.

Predictability and accuracy of maxillary repositioning during bimaxillary surgery using a three-dimensional positioning technique.

The purpose of this retrospective study was to evaluate the predictability and accuracy of maxillary repositioning during bimaxillary surgery using a three-dimensional positioning technique. Twenty-six adult patients who underwent bimaxillary surgery requiring high superior maxillary impactions were divided into 2 groups. In group A, a three-dimensional positioning technique during maxillary repositioning was used along with an intermediate occlusal splint. In group B, only an intermediate occlusal splint with internal reference points was used. Both groups had measurements from predictive tracings compared to postoperative cephalograms to assess the accuracy of horizontal and vertical movements of the maxilla. Group A showed excellent correlation between the planned and actual maxillary positions in vertical and horizontal dimensions. In group B, the maxilla tended to move anteriorly than planned. Use of the three-dimensional positioning technique offered a predictive and accurate method for maxillary repositioning.

Accuracy of maxillary repositioning in two-jaw surgery with conventional articulator model surgery versus virtual model surgery

The purpose of this study was to compare the accuracy of maxillary repositioning using the recently introduced computerized virtual model surgery (VMS) with conventional articulator model surgery (AMS). Forty-two patients who had undergone bimaxillary surgery were investigated retrospectively in this study. The patients were divided into two groups: conventional AMS (n=23) and VMS (n=19) for intermediate splint fabrication in maxillary positioning. Planned surgical movements and actual postsurgical changes of the lateral and frontal cephalometric measurements were compared. Although variations from the planned surgical movements were relatively small, both methods had statistically significant errors in some of the linear measurements. Both groups had a similar range of errors. The overall absolute mean discrepancy between the planned and actual surgical movements for the linear measurements was 1.17mm (0–3.6mm) in AMS and 0.95mm (0–3.2mm) in VMS. Of the total measurements, measurements reflecting a surgical discrepancy of more than 2mm or 2° comprised 12.0% of the cases in AMS and 7.9% in VMS. The surgical accuracy of maxillary positioning with VMS was comparable to conventional AMS. Because VMS has the definitive advantage of eliminating the complex laboratory step and shortening the laboratory time, this can be accepted as an alternative to AMS.

Surgical correction of class II skeletal malocclusion in an adult patient

Correction of skeletal deformities in adult patients with orthodontics is limited. Orthognathic surgery is the best option for cases when camouflage treatment is questionable and growth modulation is not possible. This case report illustrates the benefit of the team approach in correcting vertical maxillary excess along with class II skeletal deformity. A cosmetic correction was achieved by superior repositioning of maxilla with LeFort I osteotomy and augmentation genioplasty, along with orthodontic treatment. The patient's facial appearance was markedly improved along with functional and stable occlusion

The Comparative Study of Thin and Thick Surgical Splint During Le Fort I Osteotomy in Vertical Maxillary Excess

In the maxillary superior reposition during Le Fort I surgery, 2 types of intermediate surgical splints (thick and thin splints) are used which help to place the maxilla in its new position. The aim of the study was to compare thin and thick surgical splint during Le Fort I osteotomy in vertical maxillary excess subjects. Splints were prepared using a model surgery on casts and were used during surgery. We determined changing in vertical reference lines on the maxilla when it was positioned. We evaluated 19 subjects (6 females and 13 males) that consisted of 10 skeletal class II-vertical maxillary excess (VME), 8 skeletal class III-VME, and 1 pure VME. Results showed that the changing the splint would lead to change in reference lines in 6 subjects (32%). In 4 subjects, reference line changes were positive and in 2 subjects were negative. In the remaining 13 (68%) subjects, no changes occurred. A significant relationship was seen among the maxillary superior reposition, incisal pin changes, and reference line changes. In conclusion, following the use of the thin and thick splints, the maxilla can take different positions. The possibility of variations in using thin and thick splints is related to the changes in the incisal pin and the amount of maxillary impaction. Furthermore, the use of thick splints will cause the maxilla to take a more correct position.

Navigated repositioning of the maxilla: technical note

Elective maxillary osteotomy requires the maximum effort for accurate repositioning. The main concern during orthognathic surgery is the transfer of preoperatively simulated maxillary movements to the actual operation. Various methods of maxillary repositioning have been described, which range from using internal or external reference points to positional plates and augmented reality.1–5

The Surgical Predictability of Maxillary Advancement and Impaction in Le Fort I Osteotomy

ABSTRACT Objective: The aim of this study was to evaluate and compare the amount of preoperatively planned surgical movement of the maxilla and postoperatively obtained maxillary repositioning. Materials and Method: Thirty-one patients (16 female and 15 male) were included in this study. Fifteen combined maxillary advancement and impaction, 5 isolated maxillary impaction, and 11 isolated maxillary advancement surgeries were performed by the same surgical team. The 31 patients were divided into 2 groups: group 1 (GoGnSN≤38°) and group 2 (GoGnSN>38°). Various measurements from the horizontal and vertical reference lines were used to compare the predicted maxillary movement and the postoperatively obtained maxillary position. All variables were evaluated by Student's 2-tailed paired t tests. Results: There were statistically significant differences between the preoperatively planned and surgically obtained impaction movements of all evaluated landmarks, but no significant difference was seen between the plan...

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An accurate maxillary superior repositioning technique without intraoperative measurement in bimaxillary orthognathic surgery

This article describes a simple and accurate technique for maxillary superior repositioning without any intraoperative measurement using reference points that can be the source of error in bimaxillary orthognathic surgery. A bilateral straight locking miniplates (SLMs)/screw system secured to the maxilla and mandible maintains the three-dimensional relationship between the mandible and the skull base precisely like the incisor pin of an articulator in model surgery. The maxilla can then be accurately moved into the planned position identical to that in model surgery by the SLMs technique.

Importance of the vertical incisor relationship in the prediction of the soft tissue profile after Class III bimaxillary surgery

To quantify the relative soft tissue profile response to the skeletal changes resulting from bimaxillary surgery to correct Class III malocclusion in patients with different vertical incisor relationships presurgery. The sample comprised lateral cephalograms of 80 consecutive patients before and 2 months after surgery. All patients had one-piece Le Fort I and bilateral sagittal split osteotomies. Patients were divided in three subgroups according to their preoperative characteristics, as follows: (1) open-bite patients, (2) patients with positive overbite and the upper lip resting on upper incisors, and (3) patients with positive overbite and the upper lip resting on lower incisors (lip-block). Trimmed means of soft to hard tissue ratios were calculated for the subgroups. Regression analyses were performed to examine factors influencing the soft tissue changes. There were strong correlations between the horizontal movement of upper incisors and upper lip in patients with open bite (r = 0.77) and in patients with positive overbite and upper lip resting on upper incisors (r = 0.85). The upper lip followed the maxilla with a ratio of 0.5∶1. In patients with lip-block, the association between maxillary repositioning and upper lip changes was weak. In all groups a strong association between horizontal soft and hard tissue changes was observed for the lower lip and chin, but the pattern differed depending on the vertical movement of the mandible. In the prediction of soft tissue response it is important to take into account the vertical incisor relationship, particularly in patients with lip-block.

The effect of maxillary advancement and impaction on the upper airway after bimaxillary surgery to correct Class III malocclusion

The aim of this study was to evaluate the upper airway changes after simultaneous maxillary advancement/impaction and mandibular setback in skeletal Class III malocclusion. The subjects included 76 patients whose treatment included 1-piece LeFort I and bilateral sagittal split osteotomies. Lateral cephalograms were taken before surgery and 2 months and 3 years postoperatively. In order to analyze the effect of maxillary repositioning, the material was divided into subgroups according to whether the maxillary impaction and advancement were clinically significant (≥2 mm) or not. Advancement of the maxilla with or without impaction resulted in a significant long-term increase (P<0.001) in airway dimension at the nasopharyngeal level (13%-21% increase). At the oropharyngeal and retrolingual levels, a decrease took place but was significant (P<0.05) only at the oropharyngeal level when the maxilla was not impacted. When the maxilla was not advanced, there was no significant change, except at the hypopharyngeal level (12% decrease) (P<0.01). Clinically significant advancement (≥2 mm) of the maxilla significantly increased the airway dimension at the nasopharyngeal level and to some extent compensated for the effect of mandibular setback at the hypopharyngeal level.

Accuracy of maxillary positioning in bimaxillary surgery

The aim of the study was to investigate the accuracy of a modified pin system for the vertical control of maxillary repositioning in bimaxillary osteotomies. The preoperative cephalograms of 239 consecutive patients who were to have bimaxillary osteotomies were superimposed on the postoperative films. Planned and observed vertical and horizontal movements of the upper incisor were analysed statistically. The mean deviations of −0.07 mm (95% confidence intervals (CIs) −0.17 to 0.04 mm) for the vertical movement and 0.12 mm (95% CI −0.06 to 0.30 mm) for the horizontal movement did not differ significantly from zero. Comparison of the two variances between intrusion and extrusion of the maxilla did not differ significantly either ( p = 0.51). These results suggest that the modified pin system for vertical control combined with interocclusal splints provides accurate vertical positioning of the anterior maxilla in orthognathic surgery.

A clinical study on the stability of posterior-superior maxillary repositioning by Le Fort I osteotomy: a review of 3 patients

The purpose of this paper is to show the practicability of the posterior-superior repositioning of the maxilla by Le Fort I osteotomy with the pterygoid process fracture and the descending palatine artery preserved. We examined the movement precision and the stability of 3 cases, in which the maxillary protrusion with vertical maxillary excess was treated only by moving the maxilla backward at more than 3.0mm distance. The postsurgical positions of maxilla were more posterior to the presurgical expectations, but their differences were within 1mm.

P.298 Stability after Le Fort I sliding osteotomy for anterior and inferior repositioning of the maxilla

Nineteen patients underwent Le Fort I osteotomy and inferior maxillary repositioning. Miniplates were used to maintain the maxilla in its new position. The patients were followed from 12 to 58 months, postoperatively. Fourteen patients were considered to be stable over the long term. Five patients had a long-term relapse of more than 30%. A tendency towards greater relapse was seen in patients with more than 5 mm inferior repositioning, and in patients who had concurrent segmental osteotomies of the maxilla. In spite of the use of miniplates, there continues to be an element of unpredictability with regard to vertical relapse after inferior maxillary repositioning, and this may be related to soft-tissue influences.

Three-dimensional Assessment of the Accuracy of Maxillary Repositioning by Le Fort I Osteotomy with Emphasis on Maxillary Backward Transference

Objective: To evaluate the accuracy of repositioning of the maxilla by Le Fort I osteotomy with emphasis on maxillary backward transference.Materials and Methods: Thirty patients with jaw deformity who underwent Le Fort I osteotomy were enrolled in the study. The patients were divided into 3 groups: backward transference group, in whom both molar regions were moved >2 mm in the posterior direction; forward transference group, in whom both molar regions were moved >2 mm in the anterior direction; and minor transference group, in whom both molar regions were moved <2 mm. The 3-dimensional position of the maxillary central incisor (U1) and both first molars (R6, L6) were measured on presurgical, surgical, and post-surgical dental models. The difference between planned and actual movements was analysed using Wilcoxon signed-rank test.Results: In the backward transference group, the maxilla was moved backward to excess, probably because of a preconception that forward movement after the operation due to occlusal force will occur. In the forward transference group, the maxilla was located more forward as a consequence of being excessively moved upwards. In the horizontal direction, influence of the operator's position and the plate fixation method were thought to explain the differences between the backward transference group and the forward transference group.Conclusion: To perform the operation more precisely, additional reference points with a plane factor are needed for Le Fort I osteotomy. In the future, the infrared sensor might be useful and effective.

Estabilidade do reposicionamento anterior da maxila através de análise cefalométrica lateral

Este estudo cefalométrico retrospectivo foi proposto objetivando analisar a estabilidade do reposicionamento anterior da maxila, utilizando-se a osteotomia Le Fort I. A amostra consistiu de 30 telerradiografias de dez pacientes submetidos a um avanço cirúrgico da maxila, sem segmentação desta ou associação com qualquer cirurgia na mandíbula, realizado pela Área de Cirurgia Buco-Maxilo-Facial da Faculdade de Odontologia de Piracicaba - Unicamp. A mesma técnica de fixação interna rígida foi utilizada para todos os pacientes, e nenhum enxerto ou substituto ósseo foi usado. Três radiografias cefalométricas laterais foram realizadas para cada paciente, nos períodos pré e pós-operatórios imediatos, e com, no mínimo, seis meses após a cirurgia. Sobre estas radiografias foram feitas linhas de referência horizontal e vertical. Os pontos cefalométricos utilizados para calcular as mudanças de posição da maxila foram tanto esqueléticos, quanto dentários. A análise estatística (teste t de student pareado) não demonstrou diferença estatística significante entre os intervalos pós-operatórios imediato e com no mínimo seis meses. Concluímos que o reposicionamento anterior da maxila, utilizando-se a osteotomia Le Fort I, com fixação interna rígida e sem o uso de enxertos autógenos ou qualquer substituto ósseo, é um procedimento estável.

The predictability of maxillary repositioning in LeFort I orthognathic surgery

Our ability to predict the outcome of any orthognathic procedure relies on the surgeon's ability to accurately reproduce the desired skeletal movements and on our understanding of the soft tissue changes associated with those movements. The purpose of this retrospective study was to evaluate the surgical accuracy of maxillary repositioning by comparing the objectives obtained from cephalometric prediction tracings with the actual skeletal changes achieved during maxillary and maxillomandibular procedures. The sample consisted of 46 patients from the files of 1 orthodontist. Presurgical and immediately postsurgical cephalometric radiographs were digitized, and the original surgical prediction was reproduced with Dentofacial Planner (Dentofacial Software, Toronto, Ontario, Canada) software. Vertical and horizontal measurements to several skeletal landmarks were used to assess the differences between the predicted maxillary position and the actual maxillary postsurgical position. Statistical differences were found for some measurements, particularly those related to the vertical placement of the posterior maxilla. Three variables were evaluated for their effect on the surgical discrepancies. The 2 surgeons with the most patients were evaluated and found to have differences in the direction of discrepancies but not the amount (absolute values). Significant differences were also found when evaluating surgical complexity (single-jaw vs bimaxillary procedures) and the direction of movement (impaction vs advancement) in direction only. To assess the overall fit of individual predictions, we calculated an average discrepancy for each patient; 80% of the actual results fell within 2 mm of the prediction, and 43% fell within 1 mm of the prediction. (Am J Orthod Dentofacial Orthop 2002;122:142-54)

Postsurgical growth changes in the mandible of adolescents with vertical maxillary excess growth pattern

This case-control study investigates the effects of superior maxillary repositioning by LeFort I osteotomy on adolescent mandibular growth. A total of 15 growing patients (average age, 12.8 years) with vertical maxillary excess who had undergone maxillary surgery were compared with matched untreated control subjects. Lateral cephalograms were evaluated and superimposed to describe the presurgical (1.6 years), surgical, and postsurgical (4.0 years) changes. During the presurgical period, comparisons of traditional measures and mandibular modeling changes showed no significant differences between the 2 groups. During surgery, the maxilla was impacted approximately 3 mm anteriorly and 1 mm posteriorly, which caused a 3.2° autorotation of the mandible. During the postsurgical period, there was no change in the vertical growth pattern of the surgical patients, with the vertical facial heights increasing the same as the control subjects and the mandible rotating backwards. Although there was no inhibition of mandibular growth in the patients postsurgically, there was a decrease in horizontal maxillary growth compared with control subjects. There were clear postsurgical changes in the mandibular modeling and condylar growth, which were indicative of adaptive compensations for surgical mandibular repositioning and autorotation. It is concluded that early maxillary impaction does not normalize or inhibit the vertical maxillary excess growth pattern; mandibular modeling and condylar growth undergo adaptive changes in response to repositioning. (Am J Orthod Dentofacial Orthop 2001;119:106-16)