Impact of one-piece fronto-orbital distraction osteogenesis on orbital morphology and the development of strabismus in patients with unilateral craniosynostosis

Unicoronal craniosynostosis (UCS) is associated with orbital dysmorphologies that underlie ophthalmologic dysfunctions, such as strabismus. This study aimed to assess orbital dysmorphology in patients with UCS and how it changes after fronto-orbital distraction osteogenesis (FODO), and to analyze the features of new-onset strabismus.A retrospective analysis was conducted on 19 patients with UCS who underwent FODO between May 2008 and November 2020. Ophthalmologic records and computed tomography were reviewed. Seven parameters, including width, height, volume, and 4-direction orbital angles were evaluated in patients with UCS and compared with those of age-matched control subjects.The superolateral angle (SLA) and vertical angle (VA) of the ipsilateral orbit and the superomedial angle (SMA) of the contralateral orbit were more obtuse than those of the controls. Following FODO, the ipsilateral SLA was decreased from 69.2±5.4 degrees to 59.1±4.2 degrees (p=0.001), and the contralateral SMA was decreased from 64.8±5.8 degrees to 60.2±6.0 degrees (p=0.003). Four of the 17 patients without strabismus in the preoperative period developed strabismus, and the horizontal type was the most common. Logistic regression analysis demonstrated a significant association between new-onset strabismus and superomedial angle difference between both orbits (p=0.041, odds ratio: 1.39).Orbital dysmorphology in the UCS is bilateral, and the orbital roofs are dysmorphic. The bilateral orbital roofs are lifted toward the fused coronal suture and can be improved after FODO. Horizontal strabismus, such as esotropia and exotropia, is common after FODO, and superomedial orbital roof asymmetry may play a role in its development.