Impact of Minor Suture Fusion on Midface Hypoplasia in Syndromic Craniosynostosis

Purpose: Early onset of minor suture fusion in syndromic craniosynostosis is associated with midface dysplasia and is a common indication for craniofacial surgery. However, the potential effects of fusion severity on craniofacial growth patterns are not well understood. This study seeks to describe the impact of minor suture fusion severity on midface morphology in Crouzon syndrome. Methods: Pre-operative computed tomography images (CT) of 63 patients with Crouzon syndrome and 63 normocepahlic controls were included. Degree of suture fusion was assessed for the frontosphenoidal, sphenethmoidal, sphenosquamosal, sphenopetrosal, spheno-occipital synchondrosis, frontoethmoidal, and zygomaticosphenoidal sutures. Each suture was graded on a 5-point scale. The sella (S), nasion (N), A point (A), basion (BA), and anterior nasal spine (ANS) landmarks were used to calculate the SNA angle, BA-ANS length of the lower midface, and N-S length of the upper midface. Multiple linear regressions were used to analyze data. Results: The mean age was 43 months and 44% were female. The control group was significantly older (P < .01) than the patients with Crouzon syndrome. Advanced fusion of the spheno-occipital synchondrosis in Crouzon syndrome correlates with regression of the BA-ANS length by 0.563 mm per incremental increase in suture fusion (P < .01). Additionally, the lower midface (BA-ANS) was restricted to a greater degree than the upper midface (N-S) with progressive suture fusion in all patient types with ratios of these rates ranging between 0.602 and 0.89 for the 7 sutures analyzed. Suture fusion severity did not impact the SNA angle in any of the analyses performed. Conclusion: The severity of sheno-occipital synchondrosis fusion in Crouzon syndrome contributes to midface hypoplasia. Similarly, all anterior skull base sutures limited lower midface growth to a greater degree than the upper midface.