Craniofacial growth, modeling, and estimation of milestones

Understanding craniofacial growth is foundational for research into intra- and interspecies variation, evolution, and clinical care. The Craniofacial Growth Consortium Study (CGCS), combines cephalographs from historical growth studies to create a dense longitudinal record of growth from 6 to 22 years of age. Originally comprised of six historical studies, two new collections (Burlington Growth study and the ADA Forsyth Study) are described and added to the CGCS increasing the sample to 2,100 individuals (1,056 males, 1,044 females; median of 9 cephalographs/individual). Coordinate data for 16 cephalometric landmarks, and 48 semilandmarks, were collected from each cephalograph. Cephalometric points were collected independently by three assessors. Previously established error envelopes for each landmark are used to compare the three assessments. If two or more coordinates for a landmark grossly differ, the assessors have the option to retrace; if acceptable, they are averaged for each point. A total of 32 measures were calculated from the coordinates. A multilevel double logistic equation was implemented to estimate growth trajectories fitting each trait separately by sex. The models successfully identified growth milestones (e.g., age at peak growth velocity) for all but a single trait (N-ANS in females). Results demonstrate similarity among milestone estimates and the overall shape of the growth curve for most traits describing craniofacial. A subset of measures of small magnitude had early estimates of age at peak growth velocity and a small peak growth velocity. The six neurocranial traits were characterized as an asymptotic curve with difficulties in milestone estimation.