Objectives: The aims of the study were: (1) to develop a technique to quantify plagiocephaly that is safe, accurate, objective, easy to use, well tolerated, and inexpensive; and (2) to compare this method with tracings from a flexicurve ruler.
Design: A case-control study of 31 case infants recruited from outpatient plagiocephaly clinics and 29 control infants recruited from other pediatric outpatient clinics.
Participants: Infants in the study had been diagnosed with nonsynostotic plagiocephaly or brachycephaly and were between 2 and 12 months old.
Interventions: Infants' head shapes were measured using (a) digital photographs of a head circumference band and (b) a flexicurve ruler. Flexicurve tracings were scanned, and both the digital photos and the scanned flexicurve tracings were analyzed using a custom-written computer program.
Main outcome measures: The oblique cranial length ratio was used to quantify cranial asymmetry, and the cephalic index was used to quantify the degree of brachycephaly.
Results: The infants tolerated the photo technique better than the flexicurve. Also, mothers preferred the photo technique. There was less within-subject variance for the photos than for the flexicurve measurements. The results suggested that an oblique cranial length ratio of >or= 106% can define plagiocephaly and that a cephalic index of >or= 93% can define brachycephaly.
Conclusions: The photographic technique was better accepted and more repeatable than the flexicurve measuring system. We propose that "normal" head shape is indicated in infants with both an oblique cranial length ratio of less than 106% and a cephalic index of less than 93%.