Craniofacial integration and modularity in untreated cleft lip and palate.

Abstract

Objectives: To quantify craniofacial variation, integration, and modularity in untreated adults with orofacial clefts who had not undergone surgery, as well as in unaffected controls.

Materials and methods: Fourteen cephalometric landmarks depicting the skull base, maxilla, and mandible were identified on lateral cephalograms of 295 adult Proto-Malayid individuals. The sample included 243 individuals with unoperated clefts-179 with complete unilateral cleft lip and alveolus (UCLA, mean age 23.7 years) and 66 with complete unilateral cleft lip, alveolus, and palate (UCLAP, mean age 24.5 years)-and 50 unaffected controls (NORM, mean age 21.2 years). Geometric morphometrics were used to analyze craniofacial shape variability, integration, and modularity. Principal component analysis (PCA) was used to assess shape variability, while canonical variates analysis (CVA) was used to evaluate group differences by calculating Mahalanobis and Procrustes distances. Integration and modularity were tested for five scenarios: (1) skull base vs. maxilla vs. mandible, (2) skull base with maxilla vs. mandible, (3) skull base with mandible vs. maxilla, (4) skull base vs. maxilla with mandible, and (5) anterior vs. posterior modules. The RV coefficient and covariance ratio were used to assess covariation strength.

Results: The first 6 principal components (PC1-PC6) explained 72% of the total shape variability, with vertical shape variation and sagittal relationships being the primary sources of variability. Craniofacial shape varied significantly among the groups, with the largest Mahalanobis and Procrustes distances observed between the NORM and UCLAP groups (p < 0.001), and the smallest between the UCLA and UCLAP groups (p < 0.001). Modularity and integration patterns differed between cleft-affected individuals and controls; Those with clefts had anterior and posterior modules separated by the pterygomaxillary plane, while controls showed distinct modules for the skull base, maxilla, and mandible or combined skull base-mandible and maxilla.

Conclusions: Unoperated unilateral UCLA and UCLAP affect craniofacial integration and modularity.

Clinical relevance: These insights highlight the importance of individualized treatment approaches that consider congenital craniofacial organization, potentially improving long-term functional and aesthetic outcomes.