150 Intraoperative Photogrammetry for Quantitative Measurement of Cranial Vault Remodeling by Fronto-Orbital Advancement in Craniosynostosis

INTRODUCTION: Premature fusion of cranial sutures inhibits skull growth perpendicular to the affected suture, resulting in cranial and skull base deformities with morphologic and functional consequence. Surgical intervention for craniosynostosis simultaneously corrects the bony deformity and expands the intracranial volume to improve cosmetic development and reduce intracranial pressure. This is accomplished with fronto-orbital advancement for metopic (30%) and unilateral coronal (10%) synostoses. Essential intraoperative feedback on vault remodeling is currently limited to qualitative judgement. METHODS: An iPhone 15 acquired simultaneous video and lidar for 60 seconds after bony exposure and after remodeling. Scale-invariant features (SIFT) were extracted and matched between frames, enabling camera pose estimation and dense point cloud reconstruction of scene geometry. The pre- and post-remodeling point clouds were aligned using M-estimator sample consensus (MSAC), which identified and registered the intact biparietal bony convexity. From the thin-cut preoperative CT, we generated a Laplacian-smoothed mesh surface of the skull. The pre-remodeling point cloud was aligned to this ground-truth mesh with landmark registration. RESULTS: Intraoperative imaging was completed in 5 patients (mean age 18 months). Absolute error (mean 2.3 mm) was measured using average Euclidean distance between bony landmarks on the preoperative CT mesh model and the pre-remodeling point cloud. Relative error (mean 1.8%) was measuring using the scaling factor derived from the affine transform between pre- and post-remodeling point clouds. Cranial vault symmetry was evaluated across the sagittal plane to highlight areas requiring correction. Cranial vault volume was calculated above a plane traversing the nasion and bilateral zygomatic roots (mean increase of 143 mL or 19%). CONCLUSIONS: Pairing widely available camera technology with this fast and robust algorithmic pipeline delivers timely intraoperative feedback to guide the definitive correction of cranial vault deformity without radiation.