How accurate is digital-assisted Le Fort I maxillary osteotomy? A three-dimensional perspective

Indications and limitations of CAD/CAM splints in Le Fort I osteotomy

The surgical outcome of planned Le Fort I osteotomy (LFI) is important for successful orthognathic surgery. The aim of this study was to evaluate the accuracy of LFI using a CAD/CAM intermediate splint by performing a three-dimensional (3D) comparison of the planned and postoperative maxillary positions. This retrospective study evaluated 31 patients who underwent LFI with a CAD/CAM intermediate splint. The patients were classified into three skeletal malocclusion types: Class III, Class II, and facial asymmetry. Five maxillary reference points and two axes were measured using computed tomography obtained pre-surgery and at 4 days post-surgery and on the preoperative virtual operation 3D images. The 'movement by simulation' and 'deviation from simulation' of the maxilla were analysed by surface superimposition of the virtual LFI osteotomy segments. The deviation from simulation of Class II in the anteroposterior direction, ranging from 1.11 ± 1.05 mm (at PNS) to 3.24 ± 1.09 mm (at U1) (mean ± standard deviation values for the reference points), was significantly more forwards than that of Class III (P < 0.001). A detailed 3D study of the accuracy of LFI using CAD/CAM splints revealed high accuracy and good indication for Class III, but low accuracy, with deviation that exceeded the clinically acceptable range, in Class II and facial asymmetry.

Compare the accuracy and performance of two different types of CAD-CAM surgical guides for maxillary positioning in orthognathic surgery

Three-dimensional computer-aided design/manufacturing (CAD/CAM) maxillary guides have been developed to enhance surgical predictability, reducing mandibular interference and improving planning accuracy, especially in asymmetrical cases. This study aimed to compare the accuracy of two types of CAD/CAM guides used for maxillary positioning in orthognathic surgery. In this retrospective cohort study, 38 patients who underwent bimaxillary orthognathic surgery by the same surgeon were divided into two groups. Group 1 (n = 21) used a tooth-bone-supported guide with dual functionality for maxillary positioning and osteotomy. Group 2 (n = 17) used a bone-supported guide combined with pre-modeled titanium miniplates for osteotomy and drilling. Four fixed anatomical points (one bone and three dental) were marked preoperatively and postoperatively to assess 3D maxillary movement along the mediolateral (X), anteroposterior (Y), and vertical (Z) axes. The primary outcome was the precision of maxillary positioning, assessed by overlapping preoperative virtual planning and postoperative cone-beam computed tomography (CT) images. Quantitative differences in millimeters between the planned and achieved positions were measured for all points and axes. The groups were compared using Student's t-test (p < 0.05). Results showed that both groups achieved mean discrepancies of less than 1 mm across all points and axes. No significant differences in accuracy were observed between the two systems (p > 0.05). These findings suggest that both CAD/CAM guide systems provide high precision in maxillary positioning, offering reliable options for orthognathic surgeries based on surgeon preference.

Virtual surgical planning in orthognathic surgery: A prospective evaluation of postoperative accuracy

OBJECTIVES

The development of 3D computer-assisted technologies over the past years has led to vast improvements in orthognathic surgery. The aim of the present study was to evaluate differences in maxillary position between 3D virtual surgical planning (VSP) and surgical results.

MATERIALS AND METHODS

We assessed data from 25 patients who underwent bimaxillary non-segmented orthognathic surgery with 3D VSP. Each patient underwent a postoperative CT scan within 40 days after surgery. We compared the STL (Standard Triangulation Language) file from the VSP with that obtained from the postoperative CT.

RESULTS

According to our comparative analysis, the postoperative and VSP 3D models did not statistically differ. The Lin concordance correlation coefficient was always >0.95 for each landmark, but in 21 patients (84 % of the sample) we identified at least one point with a difference of more than 1.5 mm between the postoperative and VSP 3D model on at least one axis. The most frequently observed differences corresponded to sagittal translation and pitch rotation.

CONCLUSIONS

An intraoperative clinical and aesthetic evaluation of the consequences of bone movements on patient face is strongly recommended, also when we use VSP because we may have clinically significant differences from the planning.

Three-dimensional positioning of the maxilla using novel intermediate splints in maxilla-first orthognathic surgery for correction of skeletal class III deformity

OBJECTIVES

Successful orthognathic surgery requires accurate transfer of the intraoperative surgical plan. This study aimed to (1) evaluate the surgical error of a novel intermediate splint in positioning the maxilla during maxilla-first orthognathic surgery and (2) determine factors influencing surgical error.

MATERIALS AND METHODS

This prospective study examined 83 patients who consecutively underwent Le Fort I osteotomy for correction of skeletal class III deformity using a novel intermediate splint and a bilateral sagittal split osteotomy. Surgical error was the outcome variable, measured as the difference in postoperative translational and rotational maxillary position from the virtual plan. Measures included asymmetry, need and amount for mandibular opening during fabrication of intermediate splints, and planned and achieved skeletal movement.

RESULTS

Mean errors in translation for vertical, sagittal, and transversal dimensions were 1.0 ± 0.7 mm, 1.0 ± 0.6 mm, and 0.7 ± 0.6 mm, respectively; degrees in rotation for yaw, roll, and pitch were 0.8 ± 0.6, 0.6 ± 0.4, and 1.6 ± 1.1, respectively. The transverse error was smaller than sagittal and vertical errors; error for pitch was larger than roll and yaw (both p < 0.001). Error for sagittal, transverse, and roll positioning was affected by the achieved skeletal movement (roll, p < 0.05; pitch and yaw, p < 0.001). Surgical error of pitch positioning was affected by planned and achieved skeletal movement (both p < 0.001).

CONCLUSIONS

Using the novel intermediate splint when performing Le Fort I osteotomy allowed for accurate positioning of the maxilla.

CLINICAL RELEVANCE

The novel intermediate splint for maxillary positioning can be reliably used in clinical routines.

Cumulative exposure and lifetime cancer risk from diagnostic radiation in patients undergoing orthognathic surgery: a cross-sectional analysis

Radiation doses in dentomaxillofacial imaging are typically very low. However, diagnostic and follow-up protocols in orthognathic surgery result in a patient-specific risk in effective dose. Estimating the cancer risks from these exposures remains abstract for many maxillofacial surgeons. In this study, 40 orthognathic patients were randomly sampled and their cumulative effective dose (ED) calculated. The lifetime attributable risk of cancer (LAR) was calculated based on the standard radiological protocol for orthognathic surgery follow-up using methods described in the BEIR VII report and RadRAT. The mean cumulative ED of the 40 sampled patients at the end of their 2-year follow-up period was 1.91 ± 0.58 mSv. The LAR at the end of follow-up was 17.65 (90% confidence interval 6.46-32.90) per 100,000 person-years for male orthognathic patients and 13.93 (90% confidence interval 6.27-25.24) per 100,000 person-years for female orthognathic patients. This represents 0.70% and 0.68%, respectively, of the baseline cancer risk for oral, thyroid, and brain cancer combined. Although theoretical, these results provide a framework for interpreting radiation doses and cancer risks in patients undergoing orthognathic surgery. Considering the increased radiation sensitivity in children and adolescents, indication-oriented and patient-specific imaging protocols should be advised.

Three-dimensional planning accuracy and follow-up of Le Fort I osteotomy in cleft lip/palate patients

OBJECTIVES

Our aim was to determine the accuracy of the three-dimensional (3D) virtual planning and stability of LeFort I osteotomy in cleft lip and/or palate patients (CLP) using a validated 3D method.

MATERIALS AND METHODS

Eight patients with a history of cleft lip/palate treated with LeFort I osteotomy for maxillary hypoplasia between January 2016 and April 2020 were included in this retrospective study. Three-dimensional virtual planning was performed using Proplan software then transferred to the operation theater via 3D printed occlusal wafers. The accuracy of the 3D planning and the 1-year stability of the maxilla were evaluated by means of a validated semiautomatic stepwise module in Amira software resulting into 3 linear measurements: anterior/posterior, medial/lateral, superior/inferior and 3 rotational measurements: pitch, roll, yaw.

RESULTS

The largest mean absolute difference (MAD) for accuracy assessment was found in the A/P direction (2.75mm±2.25 mm) and in pitch (3.23°±2.11°). For A/P translation, an error of >2 mm was observed in 5(62.5%), for S/I translation an error of >2 mm was observed in 4(50.0%) of the 8 patients, whereas for pitch 3 patients(37,5%) showed an error >4° At one year follow-up, the largest linear and rotational MAD was found in the A/P direction (1.20mm±0.92 mm) and in pitch (3.31°±2.31°).

CONCLUSIONS

Findings of this study show that 3D virtual computer-assisted orthognathic surgery enables an accurate repositioning of the hypoplastic maxilla in CLP patients. However, A/P translations and pitch rotations remain challenging to achieve during surgery. These movements were also found to be least stable at one year follow-up.

Surgical Accuracy of Positioning the Maxilla in Patients With Skeletal Class II Malocclusion Using Computer-Aided Design and Computer-Aided Manufacturing-Assisted Orthognathic Surgery

OBJECTIVE

To evaluate the surgical accuracy of positioning the maxilla in patients with skeletal class II malocclusion using computer-aided design and computer-aided manufacturing (CAD/CAM)-assisted orthognathic surgery.

MATERIALS AND METHODS

The samples consisted of 10 patients with skeletal class II malocclusion, whose cone-beam computed tomographys taken before and immediately after surgery were available and who underwent bimaxillary orthognathic surgery by a single surgeon using Le Fort I osteotomy and bilateral sagittal split ramus osteotomy at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, Seoul, South Korea between January 2018 and December 2019. After virtual surgical planning was performed using the FACEGIDE system (Korea), surgical cutting guides, intermediate splints, and custom-made titanium mini-plates were fabricated using CAD/CAM technique. Using 8 landmarks (anterior nasal spine, point A, #16, #13, contact point between #11 and #21, #23, #26, posterior nasal spine), the mean differences between the virtually planned (Virtual) and actual postsurgical position of the maxilla (Actual) in the three-dimensional coordinates (ΔActual-Virtual) and their mean absolute deviations were investigated.

RESULTS

The mean differences of 8 landmarks were 0.42 mm left side movement in the transverse coordinate, 0.15 mm forward movement in the sagittal coordinate and 0.10 mm downward movement in the vertical coordinate. Their mean absolute deviations were 0.98, 0.67, and 0.62 mm in the sagittal, vertical, and transverse coordinates, respectively.

CONCLUSIONS

Since the mean difference was less than 0.5 mm and the range of error was less than 1.0 mm, CAD/CAM-assisted orthognathic surgery might have a high degree of surgical accuracy and clinical relevance in the positioning of the maxilla.

A Complete Digital Workflow for Planning, Simulation, and Evaluation in Orthognathic Surgery

The purpose of this study was to develop a complete digital workflow for planning, simulation, and evaluation for orthognathic surgery based on 3D digital natural head position reproduction, a cloud-based collaboration platform, and 3D landmark-based evaluation. We included 24 patients who underwent bimaxillary orthognathic surgery. Surgeons and engineers could share the massive image data immediately and conveniently and collaborate closely in surgical planning and simulation using a cloud-based platform. The digital surgical splint could be optimized for a specific patient before or after the physical fabrication of 3D printing splints through close collaboration. The surgical accuracy was evaluated comprehensively via the translational (linear) and rotational (angular) discrepancies between identical 3D landmarks on the simulation and postoperative computed tomography (CT) models. The means of the absolute linear discrepancy at eight tooth landmarks were 0.61 ± 0.55, 0.86 ± 0.68, and 1.00 ± 0.79 mm in left–right, advance–setback, and impaction–elongation directions, respectively, and 1.67 mm in the root mean square direction. The linear discrepancy in the left–right direction was significantly different from the other two directions as shown by analysis of variance (ANOVA, p < 0.05). The means of the absolute angular discrepancies were 1.43 ± 1.06°, 0.50 ± 0.31°, and 0.58 ± 0.41° in the pitch, roll, and yaw orientations, respectively. The angular discrepancy in the pitch orientation was significantly different from the other two orientations (ANOVA, p < 0.05). The complete digital workflow that we developed for orthognathic patients provides efficient and streamlined procedures for orthognathic surgery and shows high surgical accuracy with efficient image data sharing and close collaboration.

Validation of a novel method for canine eruption assessment in unilateral cleft lip and palate patients

Objective

The aim of this study was to propose and validate a three‐dimensional (3D) methodology for the assessment of canine eruption in patients born with unilateral cleft lip and palate (UCLP) following secondary alveolar bone graft (SABG).

Methods and Materials

A total of 10 patients (four females, six males; mean age: 8.8 years) with UCLP who underwent SABG were recruited. Pre‐ and 6‐month post‐operative cone‐beam computed tomography (CBCT) was acquired for all patients. Post‐operative data was registered onto pre‐operative data utilizing voxel‐based registration. Following superimposition, a segmentation process was applied to segment maxillary canine on both cleft and non‐cleft side. Thereafter, translational and rotational changes in canine position were assessed for both cleft and non‐cleft side by two observers.

Results

The intra‐class correlation coefficient (ICC) indicated excellent reliability (≥0.90) with inter and intra‐observer error of less than 0.05 mm. The overall ICC was found to be high for assessing both translational and rotational changes. The mean absolute inter‐ and intra‐observer difference for translational and rotational changes was found to be less than 1 mm and 3°.

Conclusion

The present method was found to be reliable proving to be clinically applicable for assessing maxillary canine eruption changes in both cleft and non‐cleft bone.