Direct Remodeling of Occipital Bullet Deformity in Sagittal Synostosis Improves Two-Year Posterior Morphology After Modified Pi Procedure

Abstract

Background: Modifications of the Pi craniectomy technique are meant to address the occipital bullet deformity of sagittal synostosis but it is not clear if they result in persistent improvement. Our purpose was to use morphometric analysis to determine if a low occipital osteotomy with verticalization results in improved occipital shape after a modified pi procedure two years after surgery. Method: We performed a retrospective cohort study comparing modified Pi technique with and without a low occipital osteotomy with verticalization immediately and two years after surgery relative to age-matched normal controls. We used anthropometric measures and population-level anatomical templates using multivariate template construction script from Advanced Normalization Tools for comparison between groups. A subgroup analysis was performed for severe occipital bullet deformity at presentation. Results: We observed stable improvement in the angle of the inferior occiput with the occipital remodeling modification that persisted two years after surgery. This improvement was seen in the entire cohort and was greater in the severe sub-group analysis. Complications and blood transfusion volumes were not different between the two techniques. The LOOV group demonstrated improved posterior vertical height and cephalic index immediately after surgery, but these did not persist two years later. Conclusion: Occipital remodeling improves the bullet deformity but does not affect posterior vertical height two years after surgery. We recommend direct inferior occipital remodeling when using the Pi technique for young patients with acute occipital incline angles and occipital constriction.