A Three-dimensional Analysis of Zygomatic Symmetry in Normal, Uninjured Faces

Symmetry recovery in zygomaticomaxillary complex fractures compared to normal unfractured population: A new reliable 3D evaluation

OBJECTIVE

This study aims to quantify the facial symmetry of surgically treated zygomaticomaxillary complex (ZMC) fractures through a new reliable three-dimensional evaluation method, which is crucial for improving post-operative aesthetic and functional outcomes.

MATERIAL AND METHODS

Healthy patients and patients with surgically treated ZMC fractures were retrospectively reviewed. Using Brainlab Elements® the zygomatic bone and the orbit of each patient was segmented and mirrored. Subsequently, the mirrored side was matched with the other side via volume-based registration, using the segmented orbit as reference. Volumetric asymmetry was measured using 3-matic software, and a surface-based matching technique was used to calculate the mean absolute differences (MAD) between the surfaces of the two sides of the ZMC. The reliability of this novel method using volume-based registration was tested, and the intra-class correlation coefficient was assessed.

RESULTS

The MAD between the surfaces of the left and right sides in the control group was 0.51 mm (±0.09). As for the ZMC fracture group, MAD was 0.78 mm (±0.20) and 0.72 mm (±0.15) pre- and post-operatively, respectively. The MAD showed statistically significant differences between pre- and post-operative groups (p = 0.005) and between control and post-operative groups (p < 0.001). The intra-class correlation coefficient was high (≥0.99).

CONCLUSIONS

This evaluation method using mirroring and volume-based registration to determine the symmetrical position of the ZMC is reliable. The surface-based measurements revealed an improved symmetry after surgery. However, the symmetry of the treated patients remained lower than the control group.

Intraoperative Computed Tomography in the Surgical Treatment of Zygomatic Complex Fracture: A Retrospective Cohort Study

This study aimed to assess the effectiveness of intraoperative computed tomography (ICT) in managing zygomatic complex (ZMC) fractures surgically. A total of 143 patients (84 men, 59 women; average age 37.13 y) undergoing surgical treatment for ZMC fractures participated in this retrospective cohort study, with 72 in the ICT group and 71 in the control group. There were no notable differences in gender, age, time from injury to surgery, and surgical duration between the two groups. The ICT group exhibited significantly fewer surgical approaches than the control group (1.39±0.519 vs. 2.07±0.617, P<0.001). Fixation points in the ICT group (1-point: 42, 2-point: 14, 3-point: 16) significantly differed from the control group (1-point: 15, 2-point: 17, 3-point: 39), P<0.001. Symmetry of reduction was assessed through immediate postoperative images, and stability was compared between immediate postoperative images and those taken at least 3 months later. Both assessments revealed no significant differences between the 2 groups. This study indicates that ICT facilitates prompt evaluation of ZMC reduction, minimizing the necessity for incisions and internal fixation, while achieving comparable reduction efficacy and long-term stability to conventional approaches.

Three-dimensional measurements of symmetry for the mandibular ramus

BACKGROUND

The study examines a sample of patients presenting for viscerocranial computer tomography that does not display any apparent signs of asymmetry, assesses the three-dimensional congruency of the mandibular ramus, and focuses on differences in age and gender.

METHODS

This cross-sectional cohort study screened viscerocranial CT data of patients without deformation or developmental anomalies. Segmentations were obtained from the left and right sides and superimposed according to the best-fit alignment. Comparisons were made to evaluate three-dimensional congruency and compared between subgroups according to age and gender.

RESULTS

Two hundred and sixty-eight patients were screened, and one hundred patients met the inclusion criteria. There were no statistical differences between the left and right sides of the mandibular ramus. Also, there were no differences between the subgroups. The overall root mean square was 0.75 ± 0.15 mm, and the mean absolute distance from the mean was 0.54 ± 0.10 mm.

CONCLUSION

The mean difference was less than one millimetre, far below the two-millimetre distance described in the literature that defines relative symmetry. Our study population displays a high degree of three-dimensional congruency. Our findings help to understand that there is sufficient three-dimensional congruency of the mandibular ramus, thus contributing to facilitating CAD-CAM-based procedures based on symmetry for this specific anatomic structure.

Probing real-world Central European population midfacial skeleton symmetry for maxillofacial surgery

OBJECTIVES

Symmetry is essential for computer-aided surgical (CAS) procedures in oral and maxillofacial surgery (OMFS). A critical step for successful CAS is mirroring the unaffected side to create a template for the virtual reconstruction of the injured anatomical structure. The aim was to identify specific anatomical landmarks of the midfacial skeleton, to evaluate the symmetry in a group of the real-world Central European population, and to use these landmarks to assess midfacial symmetry in CT scans.

MATERIAL AND METHODS

The retrospective cross-sectional study defined landmarks of the midface's bony contour using viscerocranial CT data. The distances of the skeletal landmarks (e.g., the frontozygomatic suture and temporozygomatic suture) of the left and right sides from the midline were measured and statistically compared. Midfacial symmetry for reference points was defined as a difference within 0 mm and their mean difference plus one standard deviation.

RESULTS

We examined a total of 101 CT scans. 75% of our population shows symmetrical proportions of the midface. The means of the differences for the left and right sides ranged from 0.8 to 1.3 mm, averaging 1.1 ± 0.2 mm for all skeletal landmarks. The standard deviations ranged from 0.6 to 1.4 mm, with a computed mean of 0.9 ± 0.3 mm.

CONCLUSION

We established a methodology to assess the symmetry of the bony midface. If the determined differences were equal to or lower than 2.5 mm in the mentioned midfacial skeletal landmarks, then the symmetry of the bony midface was considered present, and symmetry-based methods for CAS procedures are applicable.

CLINICAL RELEVANCE

Many CAS procedures require facial symmetry. We provide an easy-to-apply method to probe for symmetry of the midface. The method may be used for population-based research, to check for proper reduction of fractures after reposition or to screen for symmetry prior to CAS planning.

Patient-specific pre-operative simulation of the surgically assisted rapid maxillary expansion using finite element method and Latin hypercube sampling: workflow and first clinical results

Asymmetric distraction with different expansions of left and right maxillary parts is a serious complication of surgically assisted rapid maxillary expansion. An individual, highly standardized surgical intervention based on three-dimensional finite element analysis (FEA) is a new method to improve the quality of therapy. We describe a fundamental simulation-based workflow for preoperative evaluation of the osteotomies in a pilot study to achieve symmetry. A CT scan of the skull was used for analysis. Many feasible osteotomy configurations were generated and optimized using Latin hypercube sampling method and FEA choosing an individual osteotomy and maxillary movement. We successfully applied this workflow to 14 patients with symmetrical distraction.

Quantitative analysis of soft tissue sagging after lateral midface fractures: A 10-year retrospective study

BACKGROUND

Lateral midface fractures occasionally require open reduction and internal fixation to restore function and facial symmetry. However, some patients retain facial asymmetry despite undergoing surgery due to hard tissue displacement or soft tissue sagging. This study aimed to determine the influence of soft tissue sagging on the postoperative facial symmetry.

METHODS

We examined the medical records of 590 patients who underwent planned plate removal after lateral midface or zygomatic bone fractures. After applying the inclusion and exclusion criteria, we analyzed 106 cases of lateral midface fractures for hard tissue displacement and soft tissue sagging using pre- and postoperative radiological imaging and postoperative face scanning.

RESULTS

We observed significantly larger soft tissue sagging (p &lt; 0.001) and hard tissue displacement (p = 0.006) on the fractured side than on the non-fractured side. There was no correlation between differences in the soft tissue sagging and those in the hard tissue displacement (|rho|=0). Linear regression analysis showed no statistical influence of sex or age group on the soft tissue sagging and hard tissue displacement.

CONCLUSION

Therefore, we recommend treating soft tissue sagging as a discrete aspect of midfacial fracture treatment to achieve optimal postoperative facial symmetry. From a clinical perspective, we recommend better soft tissue management during open fracture treatment than focusing mainly on the reduction of bony hard tissues.

Intraoperative Use of Ultrasonography in the Reduction of Zygomatico-Maxillary Complex Fractures

Study Design

A single blind randomized controlled study.

Objective

The aim of this study is to evaluate the use of ultrasonography intraoperatively to assess the reduction of unilateral zygomatic complex fractures with a control group using the conventional blind digit palpation.

Methods

The study comprised of a sample size of 24 patients with 21 male and 3 female patients. Patients of all age groups diagnosed with unilateral displaced zygomatic complex fracture with or without mandible fracture were included in the study. The subjects were randomized into study and control groups based on a standard protocol with a total of 24 patients. Imaging was in the form of a preoperative and postoperative 3D computed tomography scan with reconstruction of the maxilla and mandible to interpret the diagnosis for all subjects. The inter-fracture distance of the fractured infraorbital rim were measured in 3 dimensions (antero-posterior, medio-lateral and supero-inferior) and compared pre and postoperatively. Preoperative, intraoperative and postoperative ultrasonographic examination was performed and recorded on all patients at the frontozygomatic region, infraorbital rim and zygomatic buttress to assess the proximity of the fractured margins pre reduction, post reduction and post fixation of the fracture segments.

Result

Statistical analytic results were significant in all 3 dimensions when measured postoperatively using computed tomography.

Conclusion

Ultrasonography is an effective screening and intraoperative tool in the armamentarium of oral and maxillofacial surgery to assess zygomatic complex fractures, avoiding incisions in aesthetic areas of the maxillofacial region.

Reduction malarplasty using a simulated surgical guide for asymmetric/prominent zygoma

Background

The present study introduces a reduction malarplasty using a three-dimensional (3D)-printed surgical guide and evaluates the guide’s technical applicability.

Methods

Twenty malarplasties were performed for 12 subjects with zygomatic asymmetry/prominency using the current method. 3D reconstruction of the craniomaxillofacial region and fine dental occlusion was made with image data from computed tomograpy and dental scanning. A computer-assisted surgical simulation was performed for reduction malarplasty and a surgical guide was designed for later 3D printing. The manufactured surgical guide was introduced to the operation field to guide the surgery; its surgical accuracy was confirmed by comparing five corresponding points from preoperative simulation and postoperative data.

Results

We successfully performed the reduction malarplasty with the surgical guide. The accuracy level of surgery fell to 0.93 mm of total median difference for the corresponding zygoma points of preoperative simulations and postoperative zygoma. The anterior and upper points showed less error level (0.59 and 0.73 mm difference, respectively) than did other points.

Conclusions

We developed a computer-assisted surgical technique using a surgical guide for asymmetrical/prominent zygoma which proved to be simple, practical, and accurate; it is expected to help surgeons perform reduction malarplasty with ease and accuracy.

A Novel Method for Quantitative Three-Dimensional Analysis of Zygomatico-Maxillary Complex Symmetry

To develop a reliable and accurate method to quantify the symmetry of the zygomaticomaxillary complex (ZMC).

Automated 3D Analysis of Zygomaticomaxillary Fracture Rotation and Displacement

Background

The zygomaticomaxillary complex (ZMC) can experience a multitude of deforming forces. There is limited understanding on which deformities alter patient outcomes. This study utilized an automated, three-dimensional analysis to elucidate which fracture patterns and rotational deformities are most prevalent and associated with postoperative complications.

Methods

This study was a 7-year retrospective review of patients with unilateral ZMC fractures who underwent surgical intervention. Patient demographics, injury mechanisms, presenting symptoms, and postoperative outcomes were collected. Segmentation was completed using Mimics software. The lateral-medial, superior-inferior, and anterior-posterior axes were manually identified on the zygoma and then displacement, rotational direction, and rotational degrees were automatically calculated using Geomagic software. Total displacement score was generated by summation of individual displacement scores at each of the five sutures.

Results

Eighty-one patients satisfied inclusion criteria. The most prevalent rotational pattern of the zygoma was medially-superiorly-posteriorly (P < 0.001). When comparing rotation along the three axes, the zygoma had the greatest rotation along the lateral-medial axis compared with the superior-inferior (P = 0.003) and anterior-posterior (P < 0.001) axes. Within each axis, the zygoma was more likely to rotate medially than laterally (P = 0.003) and posteriorly than anteriorly (P = 0.01). Multivariate analysis identified total displacement scores and degrees rotated along the lateral-medial axis as significant predictors of facial complications and reoperation.

Conclusions

This study suggests that patients with unilateral ZMC fractures who undergo surgical intervention are at an increased risk for adverse outcomes with greater rotation along the lateral-medial axis and higher total displacement scores. Additionally, the automated analysis method described can provide objective data to better characterize ZMC fractures.

The Volume Difference Along the External Surface of the Zygomatic Bone: A Novel Method of Measuring Zygomatic Bone Asymmetry

ABSTRACT

This study introduced the volume difference along the external surface (VDAES) of the zygomatic bone as a novel approach to assess zygomatic bone asymmetry and was the first to describe a distinctive, 4-step method of measuring it. VDAES has a potential to be used as an objective tool to evaluate dislocation and can assist surgeons in predicting risks of long-term cosmetic complications in patients with zygomaticomaxillary complex fractures. After having measured 100 healthy study participants, the observed median VDAES was 1.48 cm3 for all study participants, 2.02 cm3 for males, and 1.09 cm3 for females, with the gender difference being significant (P = 0.003). Additional studies are needed to test the hypothesis of whether VDAES is more relevant than conventional methods of clinically evaluating zygomatic bone asymmetry.

Three-dimensional facial hard tissue symmetry in a healthy Caucasian population group: a systematic review

OBJECTIVE

The aim of this study was to quantify the symmetry of the facial hard tissue structures using three-dimensional radiographic imaging modalities in a normal Caucasian population group.

MATERIALS AND METHODS

Electronic literature search was conducted in the following databases: PubMed, Embase, Web of Science, and Cochrane Library up to February 2021. The studies assessing symmetry of facial bones using computed tomography (CT) and cone beam CT were included.

RESULTS

The initial search revealed 8811 studies. Full-text analysis was performed on 33 studies. Only 10 studies were found eligible based on the inclusion criteria. The qualitative analysis revealed that a significant variability existed in relation to the methodologies applied for symmetry quantification.

CONCLUSION

The current review suggested that the overall relative symmetry of the normal Caucasian population group varied depending on the skeletal structure being assessed; however, majority of the observations showed a symmetry within the range of 1 mm without any significant difference between left and right sides.

CLINICAL RELEVANCE

The quantification of facial hard tissue structure symmetry is vital for the diagnosis and treatment planning of orthodontic and/or maxillofacial surgical procedures. Prospero registration number CRD42020169908.

Relationships of Reference Points, Planes and Skull Symmetry on Posterior-anterior Cephalograms in Healthy Young Adults

BACKGROUND

Radiological cephalometry is an important diagnostic tool for analyzing the shape and proportions of the skull. Standardized teleradiography of the skull in posterior-anterior (PA) projection provides orientation data on the symmetry and vertical relations of the skull. The comparison of individual findings with normal values places high demands on the selection of a control group. The aim of this study was to characterize a group to be used as a standard for cephalometric comparisons.

PATIENTS AND METHODS

PA teleradiographs of 23 healthy young adults were analyzed. Distances from reference measuring points to the median sagittal plane and the orbital horizontal plane were made. All individuals showed ideal occlusion. None of the participants had been subjected to orthodontic therapy or craniomaxillofacial surgery.

RESULTS

The measurement results showed a high degree of lateral symmetry of the skeletal reference points and planes. Comparison of the vertical reference lines confirmed the symmetrical constitution of the facial skeleton.

CONCLUSION

The study group is suitable for comparison with the cephalometric evaluations of other study groups.

Is Zygomatic Osteotomy a Viable Option to Achieve Symmetry and Stability in Post-traumatic Residual Deformity of the Zygomaticomaxillary Complex?

PURPOSE

In residual deformity cases, it is difficult to reposition the zygomaticomaxillary-complex (ZMC) intraoperatively, due to resorbed fracture edges, and lack of zygoma analysis to 3-dimensionally quantify the deformity. Instability after zygomatic osteotomy and miniplate fixation (ZOMF) due to the gap between osteotomized segments, scar tissue, muscle pull, and other factors is also unknown. The study aims to evaluate symmetry and stability after ZOMF.

MATERIALS AND METHODS

In this prospective study, a ZMC analysis was designed and patients with unilateral post-traumatic residual deformity (>10 weeks) of ZMC were treated with ZOMF. Measurements were evaluated on affected and unaffected sides at preoperatively, immediately, and 6 months postoperatively using MIMICS software. The primary outcome variable was the symmetry and stability of ZMC. Secondary parameters were changes in orbital volume, diplopia, ocular motility, mouth opening, and patient satisfaction. P < .05 was considered statistically significant. The continuous variables were compared by paired t-test. The change within the continuous variable with time was assessed by repeated measure ANOVA, followed by multiple comparisons using the Bonferroni test. The changes within the categorical variable were assessed by the McNemar test.

RESULTS

Ten patients were enrolled (mean age = 29.2 ± 9.97 years; male:female = 9:1; right:left = 4:6). The mean duration from trauma to surgery was 34.84 ± 31.35 weeks. There was an improvement in the symmetry in anteroposteriorly (P = .005), mediolaterally (P = .001), and at the arch (P = .011) postoperatively. All parameters remained stable at 6 months postoperatively (difference not significant, P > .05); with the median satisfaction score of 4 of 5. Significant improvement in mouth opening (P = .014) and orbital volume (P = .001) was noted.

CONCLUSIONS

Virtual measurements as per the proposed protocol helped in communication and quantifying ZMC. Four-point fixation with miniplates provided enough stability over the 6-month follow-up period.

Quantitative evaluation of symmetry after navigation-guided surgical recontouring of zygomatic fibrous dysplasia: a comparative study

Zygomatic fibrous dysplasia is a slowly progressive disorder of bone, which commonly causes facial asymmetry. Precise surgical recontouring can effectively improve facial aesthetics. The aim of this study was to quantitatively evaluate the effectiveness of surgical navigation guidance in correcting zygomatic asymmetry. The study included 26 patients with unilateral zygomatic fibrous dysplasia who underwent bony recontouring. They were divided into two groups according to the use of intraoperative surgical navigation (navigation group and conventional group; n=13 in each group). Clinical outcomes were evaluated using three-dimensional computed tomography. Six pairs of landmarks were identified, and the coordinates were used to calculate asymmetry indices. The curvature of protruding regions in the surgical area was measured to determine facial skeletal symmetry in three dimensions. The results were compared between the groups. All patients recovered uneventfully and their facial symmetry and aesthetics improved. For three of the six pairs of landmarks, symmetry was better in the navigation group than in the conventional group (all P≤ 0.02). The postoperative curvature ratios were better (more symmetrical) in the navigation group (P= 0.01). Surgical navigation enhances postoperative facial symmetry. However, the clinical significance of this enhancement when compared to conventional non-navigation surgery needs further investigation.

Nasal Floor Asymmetry Is Associated With Nasal Obstruction

PURPOSE

The role of morphologic characteristics of the nasal cavity in nasal obstruction is not yet sufficiently understood. The aim of this study was to determine which morphometric parameters of the nasal cavity severely impair nasal breathing and when.

PATIENTS AND METHODS

In a hospital-based, computed tomography-morphometric cross-sectional study, we evaluated computed tomography coronal scans of patients with known nasal obstruction scheduled to undergo functional nasal surgical procedures (cases) and trauma patients without facial involvement or known nasal obstruction (controls). The primary predictor variable was case versus control. In both groups, we measured and compared the piriform aperture width; nasal floor canting; piriform aperture vertical height, height-width ratio, and total cross-sectional area; height difference between the right and left nasal floors; and nasal septal thickness; as well as age and gender differences. Metric data means, standard deviations, and 95% confidence intervals were calculated and analyzed.

RESULTS

The sample was composed of 60 patients evenly divided between cases and controls. Of these, 30 were men. The average age of the cases and controls was 27.4 ± 7.8 years and 38.5 ± 18.6 years, respectively (P < .001). The differences in piriform aperture width were not statistically significant between cases and controls (23.3 ± 1.9 mm and 23.8 ± 1.7 mm, respectively; P > .2). In contrast, we noted statistically significant differences between cases and controls in nasal floor canting (5.4° ± 4.6° and 1.8° ± 1.5°, respectively; P < .001) and height difference between the right and left nasal floors (1.8 ± 1.2 mm and 1.0 ± 0.7 mm, respectively; P = .002).

CONCLUSIONS

Nasal floor canting of 3° or greater and a height difference between the right and left nasal floors of 1.5 mm or greater may contribute to the etiology of clinically relevant nasal obstruction. A piriform aperture width of 22 mm or less may be considered narrow. Future studies can determine when and how exactly to surgically address a clinically relevant narrow piriform aperture and nasal floor canting.

Computer-guided contouring of craniofacial fibrous dysplasia involving the zygoma using a patient-specific surgical depth guide

The aim of this study was to introduce a new computer-guided technique for contouring and shaving of craniofacial fibrous dysplasia involving the zygoma. Computer-guided contouring was performed for five patients with unilateral craniofacial fibrous dysplasia involving the zygoma, using a patient-specific surgical depth guide. This patient-specific guide with depth holes was virtually designed for each patient based on mirroring of the unaffected side. The guide was printed using rapid prototyping. In the surgical theatre, the guide was seated in place and implant drills were inserted through the guide holes, creating depth holes according to the preoperative planning. Bone removal was then continued using surgical burs and/or bone chisels, connecting the guiding depth holes. Satisfaction with facial aesthetics was evaluated by the patients using a Likert scale, and by the surgeons using the Whitaker rating scale. All patients were satisfied with the postoperative facial aesthetics. Four patients were rated category I on the Whitaker rating scale, and one patient as category II. In conclusion, this patient-specific surgical depth guide appears to offer a solution for the unpredictability of conventional bone removal in unilateral craniofacial fibrous dysplasia, especially in three-dimensional multiplanar areas such as the zygoma. Further investigations are required.

Anthropometric Research of Metric Characters in Zygomatic Complex Region

OBJECTIVES

To get and analyze the metric data of zygomatic region for the plasty of zygoma.

MATERIALS AND METHODS

A total of 108 dry skulls in Chinese Han population were randomly collected and measured. The metrical data were divided into 4 parts, including the relative position of contour height of zygomatic bone, the relative prominence of zygomatic bone, the relative prominence of zygomatic arch, and the angle of the zygomatic bone and arch.

RESULTS

The measurements in the 4 parts showed significantly difference between male and female (P < 0.05). For relative position of contour height of zygomatic bone group, the data of male is significantly bigger than female (P < 0.05). For relative prominence of zygomatic bone/zygomatic arch group, zygoma/zygomatic arch of male significantly protruded more than female (P < 0.05).

CONCLUSION

The location of male zygoma is more protruding than female. The female zygoma is squarer than male and marginal process is helpful in zygomatic plasty.

CLINICAL RELEVANCE

These studies show and analyze the metric data of zygomatic region in Chinese Han population for the plasty of zygoma. These different characters between males and females could be helpful in zygomatic plasty of Chinese Han population based on this research.

Natural variation of the zygomaticomaxillary complex symmetry in normal individuals

OBJECTIVE

The study aim was to investigate variations in the symmetry of the zygomaticomaxillary complex (ZMC) in normal individuals.

METHOD

Computed tomography datasets of 200 individuals without facial fractures were analyzed using a validated three-dimensional analysis technique. The absolute average distance (AD) and 90th percentile distance (NPD) were calculated, representing respectively the overall and maximum symmetry between bilateral ZMCs.

RESULTS

The mean AD and NPD of the total study group was 0.9 ± 0.3 mm (95% CI 0.3-2.3) and 1.7 ± 0.5 mm (95% CI 0.5-3.9), respectively. The mean AD and NPD in males were 1.0 ± 0.3 mm (95% CI 0.28-2.34) and 1.9 ± 0.5 mm (95% CI 0.5-3.9) versus 0.8 ± 0.3 mm (95% CI 0.4-1.7) and 1.6 ± 0.5 mm (95% CI 0.8-2.9), respectively, for females. A statistically significant difference between male and female was found for both AD and NPD (p < 0.01). The male population <40 years had a mean AD and NPD of 1.0 ± 0.3 mm and 1.8 ± 0.5 mm, which was not statistically significant when compared with males >40 years.

CONCLUSION

The naturally occurring anatomic variation in ZMC symmetry described in this study is proposed as a benchmark for evaluating the amount of preoperative displacement and postoperative reduction of ZMC in trauma cases.