Facial asymmetry in young healthy subjects evaluated by statistical shape analysis.
BACKGROUND The purpose of this study was to quantitate preoperative osseous dysmorphology in a homogeneous group of 3-month-old infants with unilateral complete cleft lip and palate. METHODS High-resolution computed tomography scans of 28 infants with unilateral complete cleft lip and palate were the basis for study. Coordinate data from 43 landmarks on the skull were collected using surface-rendered reconstructions of scan data. Euclidean distance matrix analysis was used to assess the degree of asymmetry between the cleft and noncleft sides of the craniofacial skeleton. RESULTS Linear distances involving primary and secondary landmarks (those that are located on or within the bony cleft and those that are near the cleft in the adjacent oronasal area, respectively) were highly asymmetric, with significantly greater distances on the cleft side. In addition, small (1 to 5 percent) but statistically significant asymmetries in linear distances were found involving tertiary landmarks (those that are not directly associated with the cleft or adjacent oronasal area). Most linear distances involving the nasion, zygomaxillare superius, and frontozygomatic junction were significantly greater on the cleft side, and certain linear distances in and around the middle cranial fossa were significantly smaller on the cleft side. CONCLUSIONS The extreme asymmetry of primary and secondary landmarks is explained by the cleft itself and the obvious displacement of the premaxilla toward the noncleft side. The subtler, statistically significant asymmetry of the tertiary landmarks supports the idea that the unilateral cleft affects development of the entire face and possibly the cranial base. Euclidean distance matrix analysis of computed tomography landmark data is a useful methodology for the quantitative morphometry of children with untreated unilateral cleft lip and palate.