Quantifying Orthotic Correction of Trigonocephaly Using Optical Surface Scanning

Numerous publications describe techniques to measure trigonocephaly caused by metopic synostosis, but they are potentially hazardous for use in acquiring longitudinal data. Optical surface scanning technology can safely yield craniometrics but has not established a practical means for measuring objective morphological changes to trigonocephaly during the practical time constraints of a clinical visit. The purpose of this preliminary study was to evaluate a method for safely and repeatedly measuring frontal angle (FA) using technology available at multiple centers providing treatment with cranial remolding orthoses.Optical scans of infants who underwent endoscopic-assisted minimally-invasive craniectomy for repair of metopic synostosis with cranial remolding were retrospectively analyzed. A novel FA measurement technique "FA30" was developed based on repeatable, geometrically-related surface landmarks approximating the glabella and frontotemporali. Results were compared to a control group and categories of non-synostotic deformity. Inter-rater reliability was assessed for pre- and post-treatment scan measurements among separate clinicians.All trigonocephalic subjects (n = 5) had initial FA30 significantly lower than the control group and other cohorts (P < 0.001). During the course of orthotic cranial remolding following surgical release mean FA30 increased from 121.5° to 138.5° (P < 0.001), approaching the control group mean of 144.4°. Intraclass coefficient calculation showed high reliability (intraclass correlation coefficient: 0.993, 95% confidence interval: 0.957-0.998, P < 0.001), which was supported with Bland-Altman analyses of agreement.Optical surface scanning may provide a safe, accurate, and repeatable means to measure FA. Increase in FA30 demonstrates correction of trigonocephaly. The method presented enables expeditious reporting of treatment progress to the infant's surgeon and parents, and has potential for use in optimizing treatment outcomes at multiple centers.