Assessing the corrective effects of facial bipartition distraction in Apert syndrome using geometric morphometrics

Apert syndrome is a congenital disorder characterized by craniosynostosis and midface hypoplasia. This study looks to identify to what extent bipartition distraction corrects the morphological abnormalities of this condition. Preoperative and postoperative three-dimensional computed tomography (3DCT) scans of 10 patients with Apert syndrome (12-21 years) were identified from the Great Ormond Street Hospital database. To analyse preoperative and postoperative scans, 98 landmarks and 13 normal skulls were used. Principal component analysis (PCA) was used to analyse patterns in the datasets. Within each group, eigenvectors were identified that demonstrated the aspects of the skull where most variations were found. The analysis allowed both global shape measurement and local proportions. Postoperative and normal scans both showed the same first three principal components. Warping from preoperative to postoperative illustrates midface advancement and inward rotation of the orbits. Postoperative to normal warps demonstrate some remaining differences. The reliability of the used land marks varied between 77% and 95% for the highly reproducible landmarks between the two observers. 95% versus 100% were at least acceptable reproducible landmarks. This study allows us to understand the way bipartition distraction corrects the abnormalities of the Apert skull. Analysing the surgical outcome of facial bipartition with geometric morphometrics shows that some major Apert characteristics are corrected. Using the data and the output of further studies, surgical procedures can be adapted in order to achieve a postoperative result closer to the normal population.

Therapeutic clinical question Level IV.