Developmental correlates of midfacial components in a normal and cleft lip and palate human fetal sample.

Midfacial hypoplasia in patients with complete clefts of the lip and palate is considered to be the result of congenital dysmorphogenesis combined with surgical effects. The present study describes congenital correlates of midfacial hypoplasia by examining the relationships between premaxillary size and a number of adjacent oronasal capsular components in a sample of second trimester normal and complete cleft fetal specimens. Midfacial relationships from previously published data from 3-D computer reconstructions of histologic material were assessed by multiple regression and path analyses. Stepwise multiple regression analysis revealed that the combination of age (body size) and nasal septal length were the best predictor variables of premaxillary length and accounted for 90 percent and 93 percent (p less than .01) of the variance in normal and cleft fetal specimens, respectively. Tongue length was seen to slightly increase the R2 values in the cleft, but not the normal sample. Path analysis results revealed that with body size held constant, nasal capsule volume explained only 3 percent of premaxillary variance, while septal length accounted for approximately 45 percent of the variance (p less than .05). Results show that the relationships of the midfacial components in the cleft fetal sample closely followed normal second-trimester midfacial growth patterns and suggest that the septal-traction model may be a more parsimonious and primary explanatory mechanism of early midfacial growth than the functional matrix model in both normal and complete cleft fetal specimens.