External Reference Nasal Pin for Orthognathic Maxillary Positioning: What Is the Proper Method of Placement?

Purpose Intracranial perforation with an external reference nasal pin is a possible complication during maxillary orthognathic surgery. This study attempts to quantify the maximum allowable depth of pin penetration from the soft tissue nasion (STN) and hard tissue nasion (HTN) to the anterior cranial fossa (ACF) and to evaluate the depth and direction of the nasal pin track using postsurgical cone-beam computed tomography (CBCT). Materials and Methods Two groups of patients were evaluated. A retrospective cross-sectional chart review evaluated the distance from the STN and HTN to the ACF from random patients on CBCT scans. In addition, a different group of postsurgical orthognathic cases treated between March 2013 and August 2015 were analyzed for the depth and direction of the nasal pin track toward the next anatomic cavity, which included the ACF, frontal sinus, or nasal cavity. Results We identified 103 random patients, aged 14 to 90 years. The mean distance from the STN to the ACF was 21.85 mm (range, 14.06 to 29.12 mm), and the mean distance from the HTN to the ACF was 14.16 mm (range, 7.35 to 20.53 mm). Forty postsurgical CBCT scans showed an overall nasal pin track depth of 12.91 mm (range, 8.53 to 22.60 mm), with the direction of the pin track toward the nasal cavity in most cases. Conclusions The depth of penetration of an external reference nasal pin should be limited to a maximum of 10 to 12 mm from the STN. Initial skin penetration should begin immediately caudal to the STN, and the pin should be directed in a caudal direction to avoid inadvertent entrance into the ACF, as well as to facilitate a relatively safe penetration into the nasal cavity, if the maximum depth is excessive.