2026 Proffered Presentations
S101: DEFINING CT-BASED ANATOMICAL PARAMETERS FOR FREE FLAP RECONSTRUCTION OF THE CLIVUS VIA TRANSMAXILLARY INSET
Isabella Goncalves, BS; Corinne Rabbin-Birnbaum, BA; Jackie Yang, MD; Julia Canick, MD; Lindsey Moses, MD; Donato Pacione, MD; Chandranath Sen, MD; Paul Gardner, MD; Carlos Pinheiro Neto, MD, PhD; NYU Langone Health
Background: Endoscopic endonasal approaches have provided a less invasive alternative to open anterior skull base surgery and are now the predominant method of addressing ventral skull base pathologies. Despite conferring multiple advantages, this technique was originally criticized for its high rate of CSF leaks, thus limiting its utility to small lesions.1,2,3 The development of the pedicled nasoseptal flap for endoscopic closure of skull base defects reduced the rate of post-operative CSF leaks from approximately 20-30% to approximately 5%.1,4,5 However, the nasoseptal flap lacks the robust tissue volume required for reconstruction of large defects, particularly in the setting of osteoradionecrosis (ORN). 6 The anterolateral thigh (ALT) free flap is a versatile flap which can be used for skull base repair. Recently, Pan et al. described endoscopic repair using ALT free flaps in patients with large-scale osteonecrosis of the skull base after radiation. As this technique becomes more widely used, further studies are needed to determine the optimal length of the pedicle and harvested muscle in order to direct surgical planning.
This study aims to define key skull base dimensions using computed tomography (CT) scans from healthy subjects in order to optimize muscle volume and pedicle length for endoscopic inset of ALT free flaps. Additionally, we simulate the transmaxillary pathway of flap inset to estimate the distance the flap must traverse to achieve complete coverage of the clivus.
Methods: A retrospective cohort study was performed. Measurements were taken from head CT scans of adult patients without sinonasal or skull base pathology. To ascertain optimal dimensions of muscle harvest for an ALT free flap for a transmaxillary inset and complete clival coverage, the following measurements were taken from each scan: distance from the anterior wall of maxillary sinus to the mid-clivus in axial view, the lateral-to-lateral distance between the sphenoid sinus walls at level of the paraclival carotid in axial view, the lower clivus from one hypoglossal canal to the other in axial view, and the foramen magnum to planum sphenoidale in sagittal view.
Results: In preliminary analysis of 20 scans, the average measurement of anterior wall of maxillary sinus to the mid-clivus was 80.47 mm (min 70.4, max 93.8, SD 6.17), lateral-to-lateral wall of the sphenoid sinus at level of the paraclival carotid was 29.16 mm (min 20.2, max 37.7, SD 5.00), lower clivus from one hypoglossal canal to the other was 36.26 mm (min 32.4, max 45.3, SD 3.38), and foramen magnum to planum sphenoidale was 62.34 mm (min 58.6, max 71.9, SD 3.40).
Conclusions: CT-based measurements of skull base anatomy provide critical parameters for planning ALT free flap reconstruction of the clivus. Our simulation of the transmaxillary inset pathway demonstrates the necessary muscle volume and pedicle length required to achieve complete clival coverage, supporting its feasibility for large midline skull base defects.