S6A-07 SESSION 6A: CORONAL SYNOSTOSIS SEVERITY OF ORBITAL DYSMORPHOLOGY CORRELATES WITH STRABISMUS IN UNICORONAL CRANIOSYNOSTOSIS PATIENTS UNDERGOING FRONTAL ORBITAL ADVANCEMENT

Abstract

Introduction: The purpose of this study is to determine what craniometric changes occur to both orbits of unicoronal craniosynostosis (UCS) undergoing frontal orbital advancement and remodeling (FOAR) and which of these changes are associated with new onset of postoperative strabismus. Methods: A retrospective analysis of pre and postoperative 24 UCS orbits and 24 control orbits were analyzed, totaling 144 orbits. Eight parameters were evaluated utilizing multivariate logistic regression analysis: orbital volume, horizontal and vertical cone angles, orbital depth, corneal projection, orbital rim height and width, as well as modified orbital index (MOI). MOI is an indicator of severity of Harlequin deformity. Results: Significant differences in orbital dimensions and angles were present bilaterally in UCS orbits when compared to controls. FOAR increased the ipsilateral UCS orbital volume from 13,183.93 ± 2,003.45mm to 16,220.43 ± 2,322.54mm (p<0.001). Ipsilateral horizontal cone angles were increased from 48.49 ± 5.24° to 53.50 ± 6.51° (p=0.004). Ipsilateral vertical cone angles were decreased from 73.27 ± 8.00° to 66.23 ± 9.62° (p=0.003). Ipsilateral MOI improved from 0.83 ± 0.06 to 0.88 ± 0.06 (p=0.003). Contralaterally, orbital volume also improved to 15,670.33 ± 1,988.17mm (p<0.001), a 13.4% increase. Three of the nineteen UCS patients (15%) developed transient postoperative strabismus, which resolved with eye patching. The majority of patients developed postoperative strabismus with an MOI change of greater than 20%. Logistic regression analysis displayed a significant association between new-onset strabismus and a change in MOI with a coefficient of 30.84 ±14.51 (p<0.05). Conclusion: This is the first craniometric study evaluating the association between three dimensional changes incurred by UCS orbits undergoing FOAR and strabismus. The orbital dysmorphology in UCS is bilateral in nature, and it is not wholly treated with conventional FOAR. Severity of ipsilateral orbital dysmorphology is correlated with incidence of postoperative strabismus following conventional FOAR. An ipsilateral MIO change of greater than 20% would seem to suggest that the greater the correction of Harlequin deformity may be associated with FOAR-induced strabismus. We can hypothesize those who require more radical correction, i.e. had a more severe preoperative orbital dysmorphology, are at increased risk for developing strabismus. Our methodology precludes determination of causality, but the correlation is strong. Future research is needed to develop strategies to mitigate risk of development of strabismus in this group of patients.