Anatomical considerations of the frontal process of the maxilla for the endoscopic lacrimal surgeon.

PURPOSE: Dacryocystorhinostomy (DCR) involves creating an osteotomy in the frontal process of the maxilla (FPM). This study quantifies FPM thickness and angulation from an endoscopic perspective to inform surgical technique and instrument design.

METHODS

CT scans from 94 patients were digitally segmented to create 3D models of the FPM. From a nostril-level point in the mid-sagittal plane, line vectors were projected through the FPM to simulate endoscopic access. For each vector, bone thickness and entry (α) and exit (β) angles were calculated. The angular difference (Δ = |α - β|) was used to assess alignment with common rongeur jaw angles.

RESULTS

The maximum FPM thickness averaged 11.5 mm, reaching 20.8 mm postero-superiorly. The antero-superior region had the largest Δ (25.0°), indicating suboptimal alignment. The average α and β angles were 34.5° and 36.2°, respectively, with rather minimal regional variation.

CONCLUSIONS

The FPM's thickness and geometry hinder full bone removal during unpowered endoscopic DCR, particularly in the superior region. In 12% of cases, over one-third of the FPM may be inaccessible with standard rongeurs, risking incomplete sac exposure. These anatomical findings highlight the need for preoperative imaging and may guide the selection of surgical instruments to improve operative outcomes.