Quantifying Soft Tissue Shape and Symmetry: Patients with Cleft Lip/Palate and Facial Paralysis

BACKGROUND: The objective of this study was to demonstrate simple three-dimensional analyses of facial soft tissue shape and asymmetry. METHODS: There were 2 study samples: one retrospective comprised patients with repaired cleft lip and palate (CL/P) and control subjects; and the other prospective comprised patients with unilateral facial paralysis (FP) and control subjects. The data collected were digitized three-dimensional facial landmarks. Scores for shape and asymmetry of subjects’ faces and for different facial regions were generated using Procrustes methods. Pivotal bootstrap methods and analysis of variance were used to test for significant differences in the scores between the patients and controls, and plots of the scores were generated to compare differences among the subjects. RESULTS: (1) Shape scores: The CL/P patients demonstrated significant overall and regional facial differences (P ≤ 0.01). The patients were further from the control mean, especially those with unilateral CL/P. Patients with FP demonstrated significant differences (P ≤ 0.05) for the lower face only. (2) Asymmetry scores: CL/P and FP patients demonstrated significant overall and regional facial differences (CL/P, P ≤ 0.0001; FP, P ≤ 0.01). CL/P and FP patients were more asymmetric and were further from the control mean, and patients with unilateral CL/P were more asymmetric than the bilateral CL/P patients. CONCLUSION: Clinicians can use the analyses to isolate differences and/or changes in the face due to shape or asymmetry, or a combination of both; based on the score plots, the extent of the shape and asymmetry differences can be compared among subjects and the extent of changes due to surgery measured.