Advancements in veterinary anesthesia have shifted many sinus surgeries from general anesthesia to the standing, sedated horse. Standing surgery significantly reduces intraoperative hemorrhage - a major challenge in equine head surgery - and avoids the risks associated with recovery from general anesthesia. Regional anesthesia is achieved through nerve blocks (maxillary, mandibular, infraorbital and mental) combined with local infiltration of the surgical site.
1. Trephination
Trephination involves creating a small circular opening (typically 1.- 2 cm) into the sinus bone. This is often the first step for sinuscopy, allowing a rigid - or flexible endoscope to be inserted for direct visualization and biopsy1,2. Trephination sites are specific to the targeted sinus:
Conchofrontal sinus: Medial to the bony orbit
Caudal maxillary sinus: Rostral and ventral to the orbit
Rostral maxillary sinus: Dorsal to the facial crest
While excellent for (endoscopic) diagnosis and lavage, trephination offers limited room for debriding inspissated (thickened) pus or removing large masses.
2. Osteoplastic bone flaps
For complex cases requiring extensive access, a bone flap is the gold standard. A three-sided incision is made through the skin and periosteum, and the bone is cut (often using an oscillating saw or osteotome) while remaining attached to a “hinge” of soft tissue or periosteum1.
Frontonasal bone flap: This provides the widest access to the conchofrontal sinus, the ethmoid turbinates, and the frontomaxillary opening. It is the preferred choice for treating ethmoid hematomas and cysts.
Maxillary bone flap: Centered over the facial crest, this flap allows access to the rostral and caudal maxillary sinuses. It is frequently used for dental-related sinusitis (e.g., tooth root infections) or removing large tumors.
3. Minimally invasive sinus surgery
Modern techniques focus on creating larger drainage pathways with minimal external trauma. This includes the use of laser surgery via sinuscopes to fenestrate internal septa or the enlargement of the nasomaxillary opening using electrosurgical instruments2 to facilitate natural clearance of exudate.
Intraoperative Considerations and Drainage
The primary goal of sinus surgery is often the restoration of drainage. If the natural ostium is blocked, surgeons may perform a transnasal conchotomy or create a “sino-nasal window.” This involves breaking through the thin bone of the ventral conchal sinus into the nasal meatus, allowing gravity to assist in flushing out debris postoperatively.
Postoperative Care and Complications
Postoperative management usually involves sinus lavage with sterile saline via a temporary indwelling catheter. Complications occur in approximately 25% of cases and include:
Suture periostitis: Bony swelling at the flap edges
Sequestrum formation: Small pieces of bone that lose blood supply and become infected
Chronic drainage: Often due to undetected necrotic bone or incomplete removal of dental fragments
In conclusion, surgical access to the equine sinuses has evolved from aggressive “open” procedures to more targeted, standing interventions. The choice between trephination and a bone flap depends entirely on whether the objective is simple visualization or the removal of obstructive tissue1.
References
1 Dixon P, Barnett T, Parente E, Morgan R, O’Leary JM, Vlaminck L, et al.. A multicentre study of computed tomographic and clinical features of 1600 cases of equine sinonasal disease. Part 4: treatments and response to treatments. [Internet]. Authorea; 2025 Dec 31 [cited 2026 Mar 31].
2 Bach FS, Böhler A, Schieder K, Handschuh S, Simhofer H. Surgical enlargement of the nasomaxillary aperture and transnasal conchotomy of the ventral conchal sinus: Two surgical techniques to improve sinus drainage in horses. Vet Surg. 2019 Aug;48(6):1019-1031. doi: 10.1111/vsu.13207.
