Excessive ossification of the bandeau in Crouzon and Apert syndromes

Abstract

Background: The study aimed at assessing the variations in thickness of the supra-orbital bar in Crouzon (CS) and Apert syndromes (AS) before and after fronto-facial monobloc advancement (FFMBA) using CT-scan data.

Methods: All CS or AS patients who underwent FFMBA between 2008 and 2018 with available clinical and CT-scan data were included. Frontal bone thickness was assessed at five locations of the supra-orbital bar using the Half-Maximum-Height protocol and plotted over the bone surface.

Results: We included 210 CT-scans from 25 CS to 10 AS patients and 25 controls. Before FFMBA, CS children only had a significantly thicker frontal bone (+0.772 mm ± 0.312, p = 0.017). After FFMBA, a significant increase in frontal bone thickness was reported for CS at 3 months (+0.637 mm ± 0.141, p < 0.001), 6 months (+0.910 mm ± 0.120, p < 0.001) and 12 months (+1.099 mm ± 0.124, p < 0.001) post-operatively as well as in AS at 1 month (+2.069 mm ± 0.441, p < 0.001), 6 months (+1.247 mm ± 0.406, p = 0.003) and 12 months (+2.360 mm ± 0.284, p < 0.001) post-operatively. For both syndromes, age at FFMBA and specific FGFR2 mutations significantly influenced post-operative frontal bone thickness.

Conclusions: Craniofacial surgeons should be aware of the potential need for secondary surgery of the supra-orbital after FFMBA in CS and AS. Furthermore, a thicker supra-orbital bar is part of the CS phenotype, illustrating the role of FGFR2 in craniofacial growth.

Keywords: Apert; Bandeau; Crouzon; Frontal; Monobloc; Thickness.