Correlation Between Skeletal And Soft Tissue Asymmetry In Patients With Hemifacial Microsomia: A CBCT Pilot Study.
Konstantinos Apostolopoulos, DDS1, Rany Bous, BDS, MSD1, Rahma Elnaghy, BDS, MRCS1, Anand R. Kumar, MD, FACS, FAAP2, Manish Valiathan, BDS, MDS, DDS, MSD1.
1Case Western Reserve University, Cleveland, OH, USA, 2University Hospital Cleveland Medical Center, Cleveland, OH, USA.
PURPOSE: Patients with Hemifacial Microsomia (HFM) exhibit variable levels of skeletal and soft tissue asymmetries. The purpose of this study was to utilize 3-Dimensional (3D) superimposition and color mapping of the soft and hard tissues among patients with HFM, to evaluate how the soft tissue discrepancies in various regions of the face may correlate to the skeletal discrepancy.
METHODS: This retrospective study analyzed initial (pretreatment) CBCTs of eight patients with HFM. These CBCTs were oriented using Dolphin software. The software was used to reconstruct the skeletal and soft tissue facial structures separately, which were subsequently exported as STL files. For each of the skeletal and soft tissue surface, the left side of the 3D model was mirrored using midsagittal plane as reference, in Meshmixer software, resulting in a perfectly symmetric skull and face based on two left sides (mirrored model) (Image 1, Image 2). Original and mirrored 3D models were exported to 3D Slicer software and superimposed by a surface best fit method, using the left side as reference. Differences between original right side and mirrored left side were assessed by colormap (Image 3) and were quantified by regional mesh differences on the three planes of space, in each group. The three planes were combined to produce an absolute difference between the two sides. Seven regions of interest were assessed: frontal bone area, endocanthion area, exocanthion area, malar area, maxillary frontal area, mandibular frontal area and gonion area. The correlations between the amount of skeletal asymmetry and soft-tissue asymmetry were evaluated by Pearson correlations.
RESULTS: Hard tissue asymmetry ranged from 1.4mm (Endocanthion) to 5.5mm (Gonion), while soft tissue asymmetry ranged from 1.5mm (Endocnathion) to 4.5mm (Gonion). The differences between the amount of skeletal and soft tissue asymmetry ranged between 0.2mm (Endocanthion) to 1.8mm (Malar region), with soft tissues showing slightly higher levels of asymmetry except for the Gonion and Frontal regions. Correlation between skeletal and soft tissue asymmetry were highly variable, with the highest correlation at Gonion (r=.874, p=.005) and the lowest at Exocanthion (r=.206, p=.624).
CONCLUSION: The results of this study show a high variability for the correlation between skeletal and soft tissue asymmetries among patients with HFM. Open source softwares can be valuable for assessing asymmetries in this cohort of patients. Clinicians should evaluate each component independently for proper diagnosis and treatment planning. Future studies with larger sample sizes are needed to confirm our findings.
Back to 2020 Posters