Correcting Exorbitism by Monobloc Frontofacial Advancement in Crouzon-Pfeiffer Syndrome: An Age-Specific, Time-Related, Controlled Study

Background: In FGFR2 craniosynostosis, midfacial hypoplasia features oculo-orbital disproportion and symptomatic exorbitism. Clinical consequences may mandate surgery at a young age to prevent globe subluxation, corneal ulceration, and potential loss of vision. Monobloc osteotomy and distraction osteogenesis (monobloc distraction) seek to correct exorbitism. A report of the age-related impact of monobloc osteotomy and distraction osteogenesis on orbital volume, globe volume, and globe protrusion is presented. Methods: Computed tomographic scan data from 28 Crouzon-Pfeiffer patients were assessed at preoperative, early postoperative, and 1-year follow-up time points. Orbital volumes, globe volumes, and globe protrusions were measured by manual and semiautomatic segmentation techniques, and these were compared to 40 age-matched controls. Results: Crouzon-Pfeiffer syndrome orbital volumes are significantly small, and are significantly overexpanded by distraction to endpoints correcting symptomatic exorbitism. Globe volumes are significantly larger than controls under 5 years, do not independently correlate with globe protrusion, and are unaffected by surgery. Correlation between orbital volume expansion and reduction of globe protrusion is not significant. Age-related variations of postoperative growth potential occur to 1 year postoperatively. The Crouzon-Pfeiffer syndrome FGFR2 orbit exhibits early growth acceleration followed by premature growth arrest at 10 to 14 years. Conclusions: Orbital volume expansion by monobloc osteotomy and distraction osteogenesis is not the sole determinant of reduced globe protrusion. Mean volume relapse of the orbit at 1 year is insignificant across the series. Derived Crouzon-Pfeiffer growth curves suggest that early functional monobloc in infants occurs on a background of dynamic orbital growth, which remains programmed to a Crouzon-Pfeiffer FGFR2 phenotype and aligns with the incidence of delayed clinical regression and later secondary surgery.