Accuracy of maxillary repositioning surgery using CAD/CAM customized surgical guides and fixation plates

The advent of three-dimensional imaging and computer-aided surgical simulation (CASS) have brought about a paradigm shift in surgical planning. The aim of this study was to assess the accuracy of maxillary repositioning surgery using computer-aided design and manufacturing (CAD/CAM) customized titanium surgical guides and fixation plates. Thirty consecutive adult patients, 13 male and 17 female, with a mean age of 29.2 years and 25.5 years, respectively, requiring Le Fort I maxillary osteotomy, with or without simultaneous mandibular surgery, were evaluated retrospectively. All orthognathic surgeries were performed by one experienced surgeon. The pre-surgical and post-surgical volumetric imaging were superimposed to assess the linear and angular differences between the planned and actual positions of the maxilla following surgery. With the use of the CAD/CAM titanium surgical guides and fixation plates, all surgical movements were within 2 mm and 4° of the planned movements, which is considered clinically insignificant. The overall root mean square error between the planned and actual surgical movements was 0.38 mm in the transverse dimension, 0.64 mm in the anteroposterior dimension, and 0.55 mm in the vertical dimension. In regard to the centroid of the maxilla, the absolute angular difference of the maxillary centroid was 1.06° in pitch, 0.47° in roll, and 0.49° in yaw. Maxillary repositioning surgery can be performed with high accuracy using CAD/CAM titanium surgical guides and fixation plates.     

Comparison of three different types of splints and templates for maxilla repositioning in bimaxillary orthognathic surgery: a randomized controlled trial

The selection and implementation of a plan for maxillary surgery is of the utmost importance in achieving the desired outcome for the patient undergoing two-jaw orthognathic surgery. Some splint-based and splintless methods, accompanied by computer-assisted techniques, are helpful in improving surgical plan implementation. However, randomized controlled trials focused on this procedure are lacking. This study included 61 patients who underwent bimaxillary surgeries. The patients were randomly assigned to a conventional resin occlusal splint (CROS) group, a digital occlusal splint (DOS) group, or a digital templates (DT) group, in a 1:1:1 ratio. The mean linear distance between the planned and actual postoperative positions of eight selected points on the surfaces of the maxillary teeth was selected as the outcome measure. The distance was significantly smaller in the DT group (1.17 ± 0.66 mm) when compared to both the CROS group (2.55 ± 0.95 mm, P < 0.05) and DOS group (2.15 ± 1.12 mm, P < 0.05). However, the difference between the CROS group and DOS group was not statistically significant. These findings indicate that using digital templates results in the best performance in transferring the surgical plan to the operation environment as compared to the other two types of splints. This suggests that the application of digital templates could provide a reliable treatment option.     

Accuracy of Le Fort I osteotomy in bimaxillary splint-based orthognathic surgery: focus on posterior maxillary movements

This retrospective study was performed to verify the accuracy of horizontal and vertical repositioning of the maxilla in bimaxillary osteotomy with a focus on posterior vertical displacement. Data from 39 orthognathic patients undergoing bimaxillary surgery including a one-piece Le Fort I osteotomy with pitch rotation and advancement at the University Hospitals of Leuven (Belgium), between January 2015 and April 2016, were included in the study. Preoperative and 1-week postoperative lateral cephalograms were digitized and imported into cephalometric software. Horizontal and vertical measurements of dental landmarks were used to assess the accuracy of maxillary repositioning, and errors were reported in terms of the mean and absolute mean. The horizontal advancements were randomly under- and over-corrected an average of 1.4 mm ± 1.2 mm. Vertical repositioning of the anterior maxilla followed the planning. A tendency for under-correction was found for posterior vertical intrusion of the maxilla. The same tendency towards under-correction of posterior maxillary inferior repositioning was detected when planned movements were greater than 3 mm. For all studied groups, no significant difference was found between the planning and the results achieved, validating the use of intermediate splints.     

Power chains as an alternative to steel-wire ligatures in temporary maxillomandibular fixation: a pilot study

The aim of this study was to compare two techniques for temporary intraoperative maxillomandibular fixation (TIO-MMF) during orthognathic surgery: steel-wire ligatures versus power chains. Patients undergoing orthognathic surgery between October 2019 and March 2020 were included in a prospective cross-sectional study conducted in three participating hospitals. Data were collected using a standardized measurement form. A total of 44 patients were included, in whom TIO-MMF was applied 79 times. A statistically significant difference in intraoperative loss of stability of the segment relationship was found between steel-wire ligatures (11.4%) and power chains (0%). The mean application time of TIO-MMF differed significantly between steel-wire ligatures (99 seconds) and power chains (157 seconds) (P < 0.001). There was no statistical difference in occurrence of adverse events between the two techniques. This study found that the application of TIO-MMF with power chains is more stable compared to steel-wire ligatures. Steel-wire ligatures were significantly faster to apply, although the absolute difference (less than 1 minute) was small. Other possible advantages of the proposed technique are discussed. The results of this study suggest that power chains for the application of TIO-MMF in orthognathic surgery are a valuable alternative to steel-wire ligatures.     

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 1.17 mm (0–3.6 mm) in AMS and 0.95 mm (0–3.2 mm) in VMS. Of the total measurements, measurements reflecting a surgical discrepancy of more than 2 mm 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.     

Effect of computer-assisted design and manufacturing cutting and drilling guides accompanied with pre-bent titanium plates on the correction of skeletal class II malocclusion: a randomized controlled trial

This study was performed to assess the effect of correcting skeletal class II malocclusion based on the application of computer-assisted design and manufacturing (CAD/CAM) cutting and drilling guides accompanied with pre-bent titanium plates. Fifty patients with skeletal class II malocclusion were recruited into this prospective randomized controlled clinical trial and assigned to two groups. Patients underwent bilateral sagittal split ramus osteotomy directed by CAD/CAM cutting and drilling guides accompanied with pre-bent titanium plates (group A) or CAD/CAM splints (group B). Postoperative assessments were performed. Differences between the virtually simulated and postoperative models were measured. Patients in both groups had a satisfactory occlusion and appearance. More accurate repositioning of the proximal segment was found in group A than in group B when comparing linear and angular differences to reference planes; however, no significant difference was revealed for the distal segment. In conclusion, CAD/CAM cutting and drilling guides with pre-bent titanium plates can provide considerable surgical accuracy for the positional control of the proximal segments in bilateral sagittal split ramus osteotomy for the correction of skeletal class II deformities.     

Clinical feasibility evaluation of digital dental articulation for three-piece maxillary orthognathic surgery: a proof-of-concept study

Digital dental articulation for three-piece maxillary orthognathic surgery is challenging. The purpose of this proof-of-concept study was to evaluate the clinical feasibility of a newly developed mathematical algorithm to digitally establish the final occlusion for three-piece maxillary surgery. Five patients with jaw deformities who had undergone a three-piece double-jaw surgery that was planned virtually were randomly selected for this study. The final occlusion had been hand-articulated using stone casts, scanned into the computer and used in the surgery. These hand-articulated occlusions served as the control group. To form the experimental group, the three-piece maxillary dental arch was articulated again automatically from the patient’s original occlusion using the mathematical algorithm. The hand- and algorithm-articulated occlusions were then evaluated qualitatively by two experienced orthodontists. A quantitative evaluation was also performed. The results of the qualitative evaluation showed that all of the three-piece occlusions, hand- and algorithm-articulated, were clinically acceptable based on the American Board of Orthodontics grading system. When compared, two of the algorithm-articulated occlusions were clearly better (40%), one was the same (20%), and two were slightly worse (40%) than the hand-articulated occlusions. All of the quantitative measurements were comparable between the two articulation methods. In conclusion, the results of this study demonstrate that it is clinically feasible to digitally articulate the three-piece maxillary arch to the intact mandibular dental arch.     

Effect of maxillary surgical movement on nasal cavity and maxillary sinus dimensions and function after Le Fort I osteotomy

This study was designed to evaluate the effects of different maxillary movements performed in Le Fort I surgery on the anatomy of the nasal cavity and maxillary sinus, occurrence of rhinosinusitis, and nasal airflow. Patients were divided into three groups: group I underwent pure advancement, group II underwent advancement with yaw rotation, and group III underwent advancement with impaction movements. All evaluations were performed using pre- and postoperative computed tomography images and surveys. Twenty-eight patients were enrolled. The mean pre- and postoperative nasal air volumes in group I were 22.74 ± 6.32 cm³ and 25.17 ± 6.19 cm³, respectively, showing a significant increase (P = 0.041). The mean pre- and postoperative maxillary sinus air volumes were 33.94 ± 13.72 cm³ and 26.28 ± 14.12 cm³ in group II and 35.29 ± 9.58 cm³ and 28.65 ± 8.42 cm³ in group III, respectively, showing significant reductions (P = 0.028 and P = 0.007, respectively). For all movements, the occurrence of septum deviation and nasal airflow impairment was not statistically significant. Pure maxillary advancement movement enhanced nasal cavity air volume. The yaw rotation movement significantly increased quantitative clinical rhinosinusitis symptoms. The risk of airflow impairment following Le Fort I surgery is low.     

Treatment of skeletal open bite using a navigation system: CAD/CAM osteotomy and drilling guides combined with pre-bent titanium plates

Severe skeletal open bite associated with posterior vertical maxillary excess and mandibular deformity is considered a difficult problem in orthodontic and surgical treatment. This study used a navigation system for the correction of severe skeletal open bite in order to accurately transfer the virtual plan to the actual operation and achieve precise rigid internal fixation in bimaxillary osteotomies of the jaws. Twelve patients with a severe skeletal open bite associated with vertical maxillary excess and mandibular deformity were recruited. All patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy with the guidance of this navigation system. Computed tomography and cephalometric examinations were performed to evaluate the correction of the deformity. Deviations between the simulated plan and actual postoperative outcome were measured to determine the precision of the surgery. Satisfactory and stable results were achieved in all patients postoperatively, without complications or relapse during follow-up. Photographs and cephalometric evaluations showed that the facial profile and occlusion were improved. Assessment of the deviations between the simulated plan and actual postoperative outcome showed that the navigation system can precisely transfer the virtual plan to the actual operation. The results suggest that the navigation system can accurately transfer the virtual plan to the actual operation during bimaxillary jaw osteotomies, without relapse, in patients with a severe skeletal open bite.     

Accuracy and cost effectiveness of a waferless osteotomy approach,using patient specific guides and plates in orthognathic surgery: a systematic review

The aim of this systematic review is to evaluate the accuracy of waferless osteotomy procedures in orthognathic surgery with a secondary aim to determine the cost-effectiveness of the procedure. A literature search was conducted on the databases PubMed and Scopus, with PRISMA guidelines followed. An initial yield of 4149 articles were identified, ten of which met the desired inclusion criteria. The total sample of patients undergoing waferless osteotomies included in this review was 142 patients. Nine of the studies used surgical cutting guides along with customised surgical plates to eliminate the surgical wafer and one study used pre-bent locking plates instead of customised plates. The eligible articles determined their surgical accuracy by comparing the positions of bony or dental landmarks on the pre-operative and post-operative images. The articles all reported acceptable accuracy within previously established clinical parameters. The majority of authors concluded that it is an accurate surgical approach and can be cost effective which is often a barrier to novel techniques however there were studies that contrasted the view of the cost efficacy. Due to the lack of published randomised controlled trials, current evidence is not strong enough to recommend the use of surgical cutting guides and customised/pre-bent plates for orthognathic surgery.     

Wafer as an adjunct to plating patient-specific implants for the multi-segment maxilla: a useful tool

Virtual surgical planning for orthognathic surgery using patient-specific implants (PSI) is usually waferless nowadays. However, without an occlusal wafer, difficulties arise in controlling the accuracy of multi-segment maxillary osteotomies, especially for expansion and rotational movements of each segment. It is technically challenging intraoperatively to manipulate multiple segments to fit into the PSI, as the relatively small bone segments need to be secured into the PSI while simultaneously achieving individual segment movements in all planes and with potential bony interferences with each other. Therefore, the use of a maxillary tooth-supported surgical guide is proposed and described. When the guide is inserted before the PSI, it overcomes difficulties in handling multiple maxillary segments and facilitates achieving maximal positional precision of each individual bone segment. The guide enables multiple smaller segments to behave as one unit with the designated occlusion whilst visualizing bony interferences before PSI plating is commenced. Adding a tooth-borne surgical guide in the form of a wafer and a customized arch bar is a cost-effective method to enhance accuracy in virtually planned multi-segment maxillary surgery. Further investigations are required to validate the accuracy and advantages of using wafers and PSI in multi-segment maxillary and mandibular orthognathic surgeries.     

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.     

上颌前突矫治术后软组织侧貌改变的研究

目的:分析上颌前份节段性骨切开矫治上颌前突术后软组织侧貌改变情况,探讨其稳定性。方法:对21例上颌前份节段性骨切开成年男性患者术前、术后1个月及术后1年的X线头影测量片进行对比研究。结果:术后软组织侧貌改变:上中切牙切缘点Is平均后移6.1±2.7m(mP<0.01),上唇突点Ls平均后移4.6±1.6m(mP<0.01),鼻唇角Cm-Sn-Ls平均增加6.8°±5.6(°P<0.01),上下唇间隙Stms-Stmi平均缩小4.5±3.5m(mP<0.01),露齿程度Is-Stms平均减小2.1±2.2m(mP<0.05),上唇突度减小,上唇厚度、长度及软组织面型角G-Sn-Pgss无显著改变(P<0.05)。术后1年颜面软组织侧貌改变的稳定性与术后早期相比,在水平方向上,所有指标复发率均超过10%。在垂直方向上各项指标复发率均在10%以内。结论:上颌前份节段性骨切开术矫正上颌前突,患者软组织侧貌的改善明显,效果稳定。     

Improvement in accuracy of maxillary repositioning of Le Fort I osteotomy with Orthopilot™ Navigation System: evaluation of 30 patients

Traditional model surgery with facebow transfer is not very accurate. We aimed to demonstrate that the Orthopilot™ Navigation System improves the accuracy of maxillary repositioning during Le Fort I osteotomy. Thirty patients underwent Le Fort I osteotomy alone or associated to sagittal split osteotomy. The maxilla positioning was done in two phases. First, the maxilla was positioned with the traditional occlusal splint, the position (“without Orthopilot™”) was recorded by the Orthopilot™. In the second phase, the Orthopilot™ was used to improve positioning; and the final position (“with Orthopilot™”) was recorded, after osteosynthesis. Positioning data were compared with planned data. Positioning data with and without the Orthopilot™ were also compared. Accuracy was classified in distinct classes with three major criteria (conformity, non-conformity, failure) according to the discrepancies. Conformity rate was significantly greater with the Orthopilot™ (2 without the Orthopilot™ compared with 8 with the Orthopilot™; p = 0.01). The failure rate was significantly lower with the Orthopilot™ (18 without Orthopilot™ compared with 7 with the Orthopilot™; p = 0.002). Dispersions of discrepancies were usually lower in all directions with the Orthopilot™. Navigation reduced the risk of discrepancy without cancelling it, especially when large movements are planned. The Orthopilot™ therefore improved the accuracy of traditional occlusal splint during Le Fort I osteotomy.     

Maxillary osteotomy complications in piezoelectric surgery compared to conventional surgical techniques: a systematic review

A systematic review was conducted to investigate the available evidence on maxillary complications related to piezoelectric and conventional surgery. Seven databases were searched. A total of 996 maxillary osteotomies were analysed, 864 performed with conventional tools and 132 with a piezoelectric device. One hundred and fifty-six complication events were reported. The complications, in descending order of overall prevalence, were as follows: neurosensory disturbance (64.7%), haemorrhage (8.3%), oroantral communication (7.7%), soft tissue injury (7.7%), tooth injury (5.1%), infection (3.2%), osteonecrosis (1.9%), and permanent nerve injury (1.3%). Among the complications, the results showed the highest prevalence for neurosensory disturbance, and haemorrhage was the most reported complication and the second most prevalent complication. A three-fold meta-analysis was performed. Using GRADEpro, the level of evidence was determined for each complication. The current low level of evidence suggests that piezoelectric bone surgery reduces critical and important complications during maxillary osteotomy procedures, such as neurosensory disturbance, haemorrhage, oroantral communication, tooth injury, and permanent nerve injury. However, an effective comparison between the two techniques was difficult to perform with the current available literature. Due to the small sample sizes in the piezoelectric surgery studies, caution should be exercised when considering almost non-existent reported complications.     

Sequencing of bimaxillary surgery in the correction of vertical maxillary excess: retrospective study

The aim of this study was to evaluate the precision of bimaxillary surgery performed to correct vertical maxillary excess, when the procedure is sequenced with mandibular surgery first or maxillary surgery first. Thirty-two patients, divided into two groups, were included in this retrospective study. Group 1 comprised patients who received bimaxillary surgery following the classical sequence with repositioning of the maxilla first. Patients in group 2 received bimaxillary surgery, but the mandible was operated on first. The precision of the maxillomandibular repositioning was determined by comparison of the digital prediction and postoperative tracings superimposed on the cranial base. The data were tabulated and analyzed statistically. In this sample, both surgical sequences provided adequate clinical accuracy. The classical sequence, repositioning the maxilla first, resulted in greater accuracy for A-point and the upper incisor edge vertical position. Repositioning the mandible first allowed greater precision in the vertical position of pogonion. In conclusion, although both surgical sequences may be used, repositioning the mandible first will result in greater imprecision in relation to the predictive tracing than repositioning the maxilla first. The classical sequence resulted in greater accuracy in the vertical position of the maxilla, which is key for aesthetics.     

Accuracy of Le Fort I osteotomy with combined computer-aided design/computer-aided manufacturing technology and mixed reality

The aim of this study was to verify the reproducibility and accuracy of preoperative planning in maxilla repositioning surgery performed with the use of computer-aided design/manufacturing technologies and mixed reality surgical navigation, using new registration markers and the HoloLens headset. Eighteen patients with a mean age of 26.0 years were included. Postoperative evaluations were conducted by comparing the preoperative virtual operation three-dimensional image (Tv) with the 1-month postoperative computed tomography image (T₁). The three-dimensional surface analysis errors ranged from 79.9% to 97.1%, with an average error of 90.3%. In the point-based analysis, the errors at each point on the XYZ axes were calculated for Tv and T₁ in all cases. The median signed value deviation of all calculated points on the XYZ axes was ?0.03 mm (range ?2.93 mm to 3.93 mm). The median absolute value deviation of all calculated points on the XYZ axes was 0.38 mm (range 0 mm to 3.93 mm). There were no statistically significant differences between any of the points on any of the axes. These values indicate that the method used was able to reproduce the maxilla position with high accuracy.     

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.     

Virtual surgical analysis: long-term cone beam computed tomography stability assessment of segmental bimaxillary surgery

The assessment of the stability of orthognathic surgery is often time-consuming, relies on manual re-identification of anatomical landmarks, and has been based on short-term follow-up. The purpose of this study was to propose and validate a semi-automated approach for three-dimensional (3D) assessment of the long-term stability of segmental bimaxillary surgery. The approach was developed and validated using cone beam computed tomography scans obtained at 2 weeks and 2 years postoperative. The stability of the surgical outcome was calculated as 3D translational and rotational differences between the short- and long-term postoperative positions of the individual bone segments. To evaluate reliability, intra-class correlation coefficients were calculated at a 95% confidence interval on measurements of two observers. Ten class II and III patients (six male, four female; mean age 24.4 years), who underwent a combined three-piece Le Fort I osteotomy, bilateral sagittal split osteotomy, and genioplasty, were included in the study. Intra- and inter-observer reliability were excellent (range 0.82–0.99). The range of the mean absolute difference of the intra- and inter-observer translational and rotational measurements were 0.14 mm (0.13)–0.44 mm (0.50) and 0.20° (0.16)–0.92° (0.78). The approach has excellent reliability for 3D assessment of long-term stability of segmental bimaxillary surgery.