Trephination of the Equine Rostral Maxillary Sinus: Efficacy and Safety of Two Trephine Sites

To examine 2 rostral maxillary sinus (RMS) trephine sites for safety and efficacy using skulls of horses of varying age. Descriptive study. Cadaveric equine skulls (n=40). Two RMS trephination sites (rostral, caudal) were made in each skull. Radiographic projections using markers at each site were used to determine if sites were within the RMS and directly overlying a cheek tooth. Sinusotomy in 14 skulls was used to determine correlation between radiographic and anatomic location of trephine sites, and of the rostrolateral aspect of the maxillary septum. Age-related risk of trephine site being directly over a cheek tooth was determined using logistic regression. Trephine site was within the RMS in 98% of skulls using the rostral portal and 68% using the caudal portal. The rostral site was over a cheek tooth in 18% of skulls compared with 10% using the caudal site. There was a significant negative relationship between the trephine site overlying a tooth and horse age for rostral (P=.02) and caudal (P=.03) sites. The radiographic appearance of the maxillary septum correlated to the rostrolateral portion of the septum in 12 of 14 skulls that had sinusotomy. The rostral RMS trephine portal is more reliable than the caudal site for entering the RMS. Horses