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An Update Of Cephalic Index Norms In A Large Population Of Well Children
Alannah Phelan, MD, Jing Xu, BS, Garrick Gu, BA, Jacob Wood, BS, Joyce K. McIntyre, MD, Janice F. Lalikos, MD, Janice F. Lalikos, MD.
University of Massachusetts Medical School, Worcester, MA, USA.

PURPOSE:
The incidence of deformational brachycephaly has increased dramatically since the implementation of Back-to-Sleep Campaign. Cephalic index (CI), the ratio of head width to length, is one normative indicator used by insurers to derive criteria for plagiocephaly helmet authorization. Current norms were established by a small sample of white children in the 1987 Farkas and Munro data set, but numerous studies have since then indicated a change to this norm. This study aims to redefine the CI norm within a large and diverse population of well children. Secondary aims include examining risk factors related to increased CI and how CI changes with age.
METHODS:
Children aged 0 to 3 months, 4 to 6 months, 7 to 8 months, 9 to 12 months, 2 to 3 years, and 12 to 14 years are enrolled during well child check visits. Those with prior diagnoses of premature birth, positional plagiocephaly or other craniofacial disorders were excluded. Biparietal diameter, anteroposterior diameter and head circumference were obtained using a manual caliper and tape measure. A survey containing the subjects’ birth history, past medical history and sleeping habits is administered to the parents. Student t-test, one-way ANOVA test and linear regression were used for analysis.
RESULTS:
In total, 1,335 subjects were recruited. 179 were excluded due to prematurity (145) and inaccurate (16) or repeat (14) measurements. Of the 1,156 included, 49% are males; 41% are non-Hispanic Caucasian, 31% are Hispanic, 18% are African American, 9% are Asian and 7% are mixed race. Mean CI for subjects aged 0-6 months are 83.2 ± 6.55 for males and 83.2 ± 5.93 for females, which is significantly greater than the established norms of 74.4 ± 5.2 and 74.3 ± 6.1, respectively [p < 0.0001]. Infants of Asian race have significantly greater CI compared to all other groups with a mean difference of 4 (p < 0.0005) for infants between 0-6 months of age. History of back sleep and first-born children were risk factors for increased CI for 2 to 3 year age group, however after stratification, only back sleep is significant. Scatterplot of CI and age shows positive trend from 0 to 6 months (R2 = 0.051, p < 0.0001) and negative trend from 7 to 48 months (R2 = 0.021, p = 0.0009).
CONCLUSION:
Mean CI has significantly increased for infants 0-6 months of age compared to the old established norms. This significant change may be directly associated with Back-to-Sleep Campaign, since back sleep was found to be a significant risk factor for increased CI. Our pooled data suggest that CI increases initially from 0 to 6 months, and naturally decreases afterwards without intervention. The current criteria for orthotic treatment should be re-examined due to this significant shift in CI norms and new insight in CI trend.


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