Characterisation of unicoronal synostosis for improved surgical outcomes

The severity of unicoronal synostosis is highly variable, but explanatory patient- or treatment-related factors have yet to be defined. There is a lack of standardised and precise measurements to quantify severity, and severity does not traditionally influence the choice of surgical treatment approach. The aim of this thesis was to provide an objective 3D morphological characterisation of unicoronal synostosis, to investigate the relationship between morphology and function, and to assess its relevance to surgical treatment. An automatic and objective statistical shape modelling workflow was developed to quantify the severity of orbital morphology. These 3D measures were used to evaluate the effects of surgery and subsequent growth, revealing persistent asymmetry after reconstruction by fronto-orbital advancement and remodelling. The preoperative heterogenicity of the forehead, skull base and orbits was objectively characterised, and its relationship to explanatory patient-specific factors was investigated in a retrospective two-centre cohort study conducted at Necker Hospital, France, and Uppsala University Hospital, Sweden. Peri-pterionic suture fusion seemed to limit asymmetry. Severe skull base asymmetry was associated with multiple additional issues, suggesting advantages of surgical strategies that address skull base asymmetry. Associations between ophthalmological manifestations and morphological orbital severity, or globe/orbit volume relations, were investigated preoperatively and at age three to five. Postoperative improvement in symmetry was associated with reduced anisometropia but also with new-onset strabismus, implying a complex relationship between morphology and function that is not yet fully understood. The relationship between preoperative morphological severity and long-term ophthalmological outcomes was also investigated in a retrospective two-centre cohort study conducted at Necker Hospital, France, and Uppsala University Hospital, Sweden. Global shape deviation of the ipsilateral orbit preoperatively was identified as a potential predictive factor for worse functional outcome. Neither age at surgery nor contralateral morphology were found to influence long-term functional outcomes. The results suggested benefits to surgical treatment methods that address only the ipsilateral side. In conclusion, these findings indicated a need to refine and individualise surgical treatment in unicoronal synostosis, based on factors influencing severity and long-term function, to enable successful morphological and functional outcomes. Best surgical practice in unicoronal synostosis has yet to be defined.