A test of two midfacial growth models using path analysis of normal human fetal material.

Predictions about the temporal sequencing (i.e., primacy) and causal relationships between various midfacial growth components, as suggested by two midfacial growth models (functional matrix and septal traction), were examined in the present study. The relationships between quantitative changes in the nasal septum, nasal airway, nasolabial musculature, and premaxilla of 15 normal human fetal specimens, ranging in age from 12 to 20 weeks postmenstrual age, were assessed using the multivariate technique of path analysis. Path analysis results revealed that the causal sequence of variables proposed by the septal-traction model explained more of the variance in premaxillary size (87 percent goodness-of-fit) than did the sequence of variables proposed by the functional matrix model (65 percent goodness-of-fit). These results suggest that the septal-traction model may be a more parsimonious and primary explanation of early human fetal midfacial growth than the functional matrix model. Path analysis results also reiterate the observed complex developmental relationships within the fetal labioseptopremaxillary region, knowledge of which may be important in the surgical management of infants with complete cleft.