Accuracy of two midsagittal planes in three-dimensional analysis and their measurement in patients with skeletal mandibular deviation: a comparative study

Analyzing Discrepancies and Correlations in Soft and Hard Tissue Asymmetry: A Focused Study on Hemifacial Microsomia and Isolated Microtia

BACKGROUND

This study aims to thoroughly investigate the distinctions and relationships between facial hard and soft tissue asymmetry, as well as their variations within different conditions and age groups.

METHODS

This cross-sectional study analyzed pre-treatment computed tomography (CT) images from 120 male patients aged 5 to 12 years with unilateral HFM (Pruzansky-Kaban types I and IIA) or isolated microtia. The 120 patients were categorized into four groups by condition (HFM or isolated microtia) and age (5-7, 8-12 years). Segmentation and extraction of anatomical landmarks were performed using Mimics software, followed by generating root-mean-square (RMS) values for facial asymmetry. Statistical analysis, including the Wilcoxon signed-rank test and Spearman correlation coefficient, was conducted to assess differences and correlations in asymmetry.

RESULTS

The study found that soft tissue asymmetry was generally greater than hard tissue asymmetry across all facial regions. The complexity of regional asymmetry correlations increased with age in HFM patients but decreased in isolated microtia patients. Significant correlations between hard and soft tissues were observed within the same anatomical regions, particularly in HFM patients aged 8-12 years.

CONCLUSION

The intricate interplay between hard and soft tissues was observed in HFM and isolated microtia patients. Personalized analysis of the causes of asymmetry in different regions is crucial for the formulation of effective treatment plans.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

A 3-Dimensional Morphometric Analysis of 4 Midsagittal Planes for CT Scan Reference Determination in Children with Syndromic Craniosynostosis

OBJECTIVE

To identify the suitable and practical midsagittal plane (MSP) reference for computed tomography (CT) scan skull analysis in patients with syndromic craniosynostosis.

DESIGN

Retrospective study.

SETTING

Tertiary referral hospital.

PATIENTS AND PARTICIPANTS

A total of 19 full skull CT scans of syndromic craniosynostosis patients.

METHODS

Seven craniofacial landmarks located on the midline and 4 MSPs that was previously published and clinically recognized (Planes: SPBaS, SPNSANS, SPLOrPo and SPZFTP) were constructed from the CT images. The absolute distance of every plane from 7 landmarks were then calculated. These distances were subsequently subjected to statistical analysis.

MAIN OUTCOME MEASURE(S)

The absolute distance of different MSPs from 7 landmarks.

RESULTS

The distances of landmarks measured to SPBaS were the highest, with the most prominent fluctuation. The fluctuation of the SPNSANS, SPLOrPo and SPZFTP had similar direction changes, with the latter being the closest. Pairwise comparisons demonstrated statistical differences (P < .008 using the Bonferroni correction) between the measured distances of A point (M = 0.25, SD = 0.16) and B point (M = 2.21, SD = 1.6) to SPNSANS. There were statistical significances between distances of B point (M = 1.68, SD = 1.07) and CG point (M = 0.55, SD = 0.37) to SPZFTP plane. There was no statistical significance on each landmark to SPLOrPo.

CONCLUSIONS

The study demonstrates that SPBaS is not recommended for MSP reference. While SPNSANS should be carefully selected, the application of SPLOrPo and SPZFTP are interchangeable, with the SPZFTP plane slightly exaggerating the mandible deviation relative to the superior and posterior of the midface.

Exploring Progression and Differences in Facial Asymmetry for Hemifacial Microsomia and Isolated Microtia: Insights from Extensive 3D Analysis

BACKGROUND

Aiming to measure and compare asymmetry of facial hard and soft tissues in patients with HFM and isolated microtia, examining how it evolves.

METHODS

This cross-sectional study assessed facial asymmetry in male East Asian patients aged 5-12 diagnosed with unilateral hemifacial microsomia (Pruzansky-Kaban types I and IIA) or isolated microtia. Using 3D imaging of computed tomography scans, it measured root-mean-square (RMS) values for surface deviations across facial regions. Statistical analyses explored differences between conditions and the relationship of age with facial asymmetry.

RESULTS

A total of 120 patients were categorized into four groups by condition (HFM or isolated microtia) and age (5-7 and 8-12 years). Patients with HFM exhibited the greatest asymmetry in the lower cheek, while those with isolated microtia showed primarily upper face asymmetry. Significant differences, except in the forehead and nasal soft tissue, were noted between the groups across age categories. Notable distinctions in hard tissue were found between age groups in the nasal and mid-cheek areas for patients with HFM (median RMS (mm) 0.9 vs. 1.1, P = 0.02; 1.5 vs. 1.7, P = 0.03) and in the nasal and upper lip areas for patients with isolated microtia (median RMS (mm) 0.8 vs. 0.9, P = 0.002; 0.8 vs. 1.0, P = 0.002). Besides these areas for HFM, no significant age-asymmetry correlation was detected.

CONCLUSIONS

Significant differences in facial asymmetry were observed between HFM and isolated microtia, with the asymmetry in specific area evolving over time.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Establishment of the mid-sagittal reference plane for three-dimensional assessment of facial asymmetry: a systematic review : Establishment of the mid-sagittal reference plane: a systematic review

OBJECTIVE

To systematically review the literature for mid-sagittal plane establishment approaches to identify the most effective method for constructing the mid-sagittal plane for the evaluation of facial asymmetry.

MATERIALS AND METHODS

Six electronic databases (PubMed, Medline (via Ovid), EMBASE (via Ovid), Cochrane Library, Web of Science, and Scopus) and grey literature were searched for the studies that computed the mid-sagittal reference plane three-dimensionally, using a combination of MeSH terms and keywords. The methodological quality and the level of evidence for the included studies were analyzed using QUADAS-2 and GRADE, respectively.

RESULTS

The preliminary search yielded 6746 records, of which 42 articles that met the predefined inclusion criteria were included in the final analysis. All the included articles reported the construction of the mid-sagittal reference plane (MSP) using varied methods. The risk of bias and concerns regarding the applicability of the included studies were judged to be 'low'. The level of evidence was determined to be 'low' for the effectiveness of the technique and 'moderate' for the ease of clinical applicability.

CONCLUSION

Despite methodological heterogeneity, this review substantiates the comparable efficacy of cephalometric and morphometric MSP construction methods. A fully automated morphometric MSP holds promise as a viable option for routine clinical use. Nevertheless, future prospective studies with an emphasis on the impact, accuracy, and clinical applicability of MSP construction techniques in cases of facial asymmetry are required.

CLINICAL RELEVANCE

The present review will assist clinicians in selecting the most suitable method for MSP construction, leading to improved treatment planning and ultimately more favorable treatment outcomes.

Three-dimensional assessment of facial asymmetry in class III subjects, part 2: evaluating asymmetry index and asymmetry scores

OBJECTIVES

To evaluate the outcomes of corrective surgical treatment for craniofacial asymmetry using four different methods with the aim of developing the best technique for craniofacial asymmetry assessment.

MATERIALS AND METHODS

CBCT images of twenty-one class III subjects with surgically corrected craniofacial asymmetry and twenty-one matched controls were analyzed. Twenty-seven hard tissue landmarks were used to quantify asymmetry using the following methodologies: the asymmetry index (AI), asymmetry scores based on the clinically derived midline (CM), Procrustes analysis (PA), and modified Procrustes analysis (MPA).

RESULTS

Modified Procrustes analysis successfully identified pre-operative asymmetry and revealed severe asymmetry at the mandibular regions compared to controls, which was comparable to the asymmetry index and clinically derived midline methods, while Procrustes analysis masked the asymmetric characteristics. Likewise, when comparing the post-surgical outcomes, modified Procrustes analysis not only efficiently determined the changes evidencing decrease in facial asymmetry but also revealed significant residual asymmetry in the mandible, which was congruent with the asymmetry index and clinically derived midline methods but contradictory to the results shown by Procrustes analysis.

CONCLUSIONS

In terms of quantifying cranio-facial asymmetry, modified Procrustes analysis has evidenced to produce promising results that were comparable to the asymmetry index and the clinically derived midline, making it a more viable option for craniofacial asymmetry assessment.

CLINICAL RELEVANCE

Modified Procrustes analysis is proficient in evaluating cranio-facial asymmetry with more valid clinical representation and has potential applications in assessing asymmetry in a wide spectrum of patients, including syndromic patients.

3-dimensional analysis of hard- and soft-tissue symmetry in a Chinese population

BACKGROUND

Facial symmetry severely affects appearance and function. Large numbers of patients seek orthodontic treatment to improve facial symmetry. However, the correlation between hard- and soft-tissue symmetry is still unclear. Our aim was to investigate the hard- and soft-tissue symmetry in subjects with different levels of menton deviation and sagittal skeletal classes with 3D digital analysis and to investigate the relationship between the entire and individual hard- and soft-tissues.

METHODS

A total of 270 adults (135 males and 135 females) consisting of 45 subjects of each sex in each sagittal skeletal classification group. All subjects were further classified into relative symmetry (RS), moderate asymmetry (MA) and severe asymmetry (SA) groups based on the degree of menton deviation from the mid-sagittal plane (MSP). The 3D images were segmented into anatomical structures and mirrored across the MSP after establishing a coordinate system. Original and mirrored images were registered by a best-fit algorithm, and the corresponding root mean square (RMS) values and colormap were obtained. The Mann‒Whitney U test and Spearman correlation were conducted for statistical analysis.

RESULTS

The RMS increased with greater deviations with regard to the deviation of the menton in most of anatomical structures. Asymmetry was represented in the same way regardless of sagittal skeletal pattern. The soft-tissue asymmetry had a significant correlation with dentition in the RS group (0.409), while in the SA group, it was related to the ramus (0.526) and corpus (0.417) in males and was related to the ramus in the MA (0.332) and SA (0.359) groups in females.

CONCLUSIONS

The mirroring method combining CBCT and 3dMD provides a new approach for symmetry analysis. Asymmetry might not be influenced by sagittal skeletal patterns. Soft-tissue asymmetry might be reduced by improving the dentition in individuals with RS group, while among those with MA or SA, whose menton deviation was larger than 2 mm, orthognathic treatment should be considered.

Orthodontic Perspective for Face Asymmetry Correction

Facial symmetry affects the perception of facial beauty. Overall, facial harmony with an appropriate facial proportion and satisfactory midline facial symmetry are crucial factors for facial attractiveness. The role of orthodontists in correcting facial asymmetry begins with providing suitable diagnosis of the condition and identifying patients’ expectations. Through a thorough, subjective clinical evaluation of dentofacial asymmetry, the procedures for the surgical orthodontic management of facial asymmetry are discussed. The aim of this clinical review is to provide information on surgical indications for facial asymmetry, optimal treatment goals, presurgical orthodontic preparation, the surgery-first approach, three-dimensional (3D) surgical simulation, postsurgical orthodontic finishing, and treatment outcome evaluation. A comprehensive 3D diagnosis with appropriate planning, accurate transference of surgical simulation to real surgery, slight overcorrection, periodic assessment of treatment outcomes, and awareness of treatment limitations are essential to improve treatment outcomes of facial 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.

Construction and validity of a midsagittal plane based on the symmetry of a 3-dimensional model of the relevant cranial base

INTRODUCTION

The midsagittal plane (MSP) is the foundation for 3-dimensional (3D) cephalometric analyses. This article aimed to provide a protocol to construct a reliable and accurate MSP for 3D cephalometric craniofacial analysis.

METHODS

Cone-beam computed tomography data of 16 adult patients without obvious bilateral asymmetry were collected. The model of the anterior cranial base and sphenoid bone was constructed, and the candidate MSP was determined on the basis of the symmetry of this model. Intraclass correlation coefficients were used to assess intra- and interexaminer reliability of the candidate MSP. To investigate the accuracy of this candidate MSP, we constructed a true plane of symmetry of craniomaxillofacial structure and a control plane on the basis of 3 cranial midline points. We then compared these with the candidate MSP.

RESULTS

This candidate MSP resembled the true plane of symmetry with all the mean absolute errors <1 mm, and all the absolute errors for the candidate MSP were significantly smaller than the control plane (P ≤0.002). The relative intra- and interexaminer reliability for this candidate MSP was almost perfect (intraclass correlation coefficients >0.9).

CONCLUSIONS

The candidate MSP constructed using this method was thought to be reliable and accurate for 3D cephalometric analysis in patients without obvious cranial asymmetry.