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

Abstract

The rostral RMS trephine portal is more reliable than the caudal site for entering the RMS. Horses <or=5 years are at high risk for the trephine site overlying a cheek tooth and we advise that RMS trephination in this age group be performed with radiographic guidance.

Comparison of Sinoscopic Techniques for Examining the Rostral Maxillary and Ventral Conchal Sinuses of Horses

“…14 Variation in paranasal sinus morphology, particularly of the maxillary septum, both with age and between horses, 5,15 means that direct, single-portal approaches to the RMS like we performed cannot reliably provide consistent access to the RMS. 2,4 In agreement with other studies, 2,4 we found that the rostral RMS approach provides more reliable access to the RMS than does the caudal RMS approach. By using a trans-illumination technique to identify the position of the maxillary septum the accuracy of direct trephination of the RMS was greatly enhanced using the light-indicated RMS approach.…”

“…The RMS accommodates the reserve crowns of the 3rd, 4th, and 5th cheek teeth (Triadan 08, 09, 10), 5 and thus a complication of direct trephination into the RMS is damage to the alveolar bone overlying the apices of these cheek teeth or damage to the underlying teeth. 4 In agreement with a recent study, 4 damage to the alveolar bone and the apices of the cheek teeth was most prevalent in horses o6 years of age with the rostral RMS approach. Others have suggested that the skull should be examined radiographically before trephining into the RMS to guide selection of a portal that avoids the maxillary septum and dental structures.…”

“…Others have suggested that the skull should be examined radiographically before trephining into the RMS to guide selection of a portal that avoids the maxillary septum and dental structures. 2,4 Identifying the maxillary septum radiographically, is however a difficult task because the maxillary septum is composed of both bone and radiolucent cartilage and courses obliquely through the sinuses. 16,17 Beyond providing the best observation of the RMS and VCS, the frontal VCB approach results in direct communication between all paranasal sinus compartments enabling effective lavage of all compartments through a single portal.…”

“…2 Access to the RMS using these direct approaches is especially difficult in horses o6 years old because the unerupted crowns of the cheek teeth (Triadan 08, 09, 10) occupy most of the RMS, preventing manipulation of the endoscope. 4 Access into the RMS and VCS by perforating the ventral conchal bulla (VCB), with the horse sedated or anesthetized, either through a large frontonasal bone flap [5][6][7] or through a large trephine hole in the frontal bone 8 has been described. Examination of the VCS is important because this sinus is a frequent site at which inspissated exudate accumulates.…”

Equine paranasal sinus disease: A long‐term study of 200 cases (1997–2009): Ancillary diagnostic findings and involvement of the various sinus compartments

“…Endoscopic examination of the RMS and VCS was usually possible following perforation of the VCB, without having to trephine directly into the RMS ‐ which is technically difficult in young horses and risks damaging the alveoli (Barakzai et al . 2008; Perkins et al .…”