Investigating the cause of late deformity following fronto-orbital remodelling for metopic synostosis using 3D CT imaging

Publication date: Available online 16 November 2018

Source: Journal of Cranio-Maxillofacial Surgery

Author(s): Naiara Rodriguez-Florez, Aran Florez-Tapia, Noor U.O. Jeelani, Sylvia Schievano, David J. Dunaway, Richard D. Hayward

Summary

Purpose

Late deformity/indentation is well-recognised following fronto-orbital remodelling (FOR) for metopic synostosis. We hypothesise that if damage to temporalis muscle were a contributor, the thickness of soft tissue and bone in the affected area would be reduced.

Materials and Methods

Soft tissues and bone were separately segmented and reconstructed three-dimensionally from computed tomograms of 8 patients 1.5 to 18 years post-FOR performed at 16 ± 2 months for metopic synostosis and from 8 age-matched controls. Soft tissue (taken as proxy for temporalis muscle) and bone thickness overall and in the indented areas were computed.

Results

Post-FOR, three-dimensional soft tissue thickness maps demonstrated temporalis extending upwards but falling short of the indented area. Overall skull thickness increased with age post-FOR (logarithmic fit R²= 0.71) and for controls (R²=0.90). Although immediately post-FOR the future indented area had a thickness of 98% of control, it decreased linearly to 64% 16 years later (Pearson's r=0.84).

Conclusion

These findings suggest that late post-FOR deformity/indentation is enhanced by limited upward extension (or retraction downwards) of temporalis muscle, while bone thickness in the affected area gradually decreases. This supports the hypothesis that aberrant re-attachment of the temporalis muscle makes a material contribution to late deformity following FOR for metopic synostosis.

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