073. Accuracy of 2D photography compared to 3D optical scanning in measuring the bifrontal angle

Authors: Nathan Leclair

Craniometrics objectively describe head shape features important for the diagnosis and classification of cranial deformities in pediatric patients. The bifrontal angle (BFA), defined anteriorly by the metopic suture and posterolaterlly by the orbits, is an important measure of trigonocephaly quantified from CT and 3D optical scans of patient heads. We recently developed the anterior arc angle (AAA) as a surface correlate of the BFA derived from standard top-down orthogonal photography. Here we demonstrate its agreement with 3D optical scanning-derived BFA measurements in an ambulatory craniofacial population.Methods: This study is a retrospective analysis of unique, paired (within 30-days of each other) AAA and BFA measurements. Test agreement was assessed using intraclass correlations (ICC) and Bland-Altman analysis.
19 paired measurements were analyzed from 12 unique patients (male:female, 7:5) seen by the Connecticut Children’s Division of Neurosurgery due to concerns for a head shape abnormality. Median age at the time of measurement was 5.2 months (IQR: 3.0 – 8.9). Cranial deformities included: anterior plagiocephaly (n = 2), trigonocephaly (n = 5), and scaphocephaly (n = 5). The ICC comparing 2D photography to 3D optical scans was 0.778 (CI95% = 0.51 – 0.908, p = 2.73E-05). Bland-Altman analysis demonstrated a mean difference between BFA and AAA measurements of 2.1O (CI95% = -1.4 – 5.6), with an upper limit of agreement of 16.5O (CI95% = 10.3 – 22.6) and a lower limit of agreement of -12.3O (CI95% = -18.4 – -6.1).
There is a high degree of agreement between photo-derived AAA and scan-derived BFA craniometrics. Given the availability of digital photography and low cost of photo-based craniometrics derivation, photo-derived AAA metric may be a preferable technique for routine ambulatory screening of trigonocephaly patients compared to CT or optical scanning.