{'fraction_non_alphanumeric': 0.03036726906566326, 'fraction_numerical': 0.02220573427314643, 'mean_word_length': 5.502412129565816, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 1, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Outcomes following single, caudally based bilateral versus unilateral frontonasal sinusotomy for treatment of equine paranasal sinus disease

Abstract Background Bilateral sinus disease is relatively uncommon in horses, accounting for 3%–4.5% of horses with sinonasal disease, but may require bilateral paranasal surgery for complete resolution. Complications and recurrence following bilateral sinusotomy have not been reported or compared to those following unilateral procedures. Objective To describe clinical features and outcomes in horses undergoing standing single, caudally based bilateral frontonasal sinusotomy compared to unilateral frontonasal surgery. Methods Records of horses (n = 37) undergoing surgical treatment for sinus disease (five bilateral, 32 unilateral) were retrospectively reviewed (2010–2017) for signalment, presenting complaint, duration of signs preoperatively, diagnostic imaging, treatments administered, duration hospitalization, complications, and owner satisfaction with the procedure. Mann–Whitney testing was used to compare age, duration of hospitalization, and follow‐up time in horses undergoing unilateral or bilateral procedures. Fisher's exact testing was used to determine if sex predilection was present for unilateral or bilateral disease. Survival time and time to recurrence were compared by Kaplan–Meier survival curves and log‐rank curve comparison testing. Significance was assessed at p < 0.05. Results Length of signs prior to admission did not differ between horses with unilateral and bilateral disease (p = 0.09), but there was a tendency for horses with bilateral disease to have clinical signs for longer. Age (p = 0.19) and hospitalization duration (p = 0.53) did not differ between horses undergoing unilateral versus bilateral procedures. Recurrence or failure to resolve signs was reported in 11/32 (34%) of unilateral and 0/5 bilateral cases (p = 0.07). Conclusions The bilateral single, caudally based sinusotomy approach may be considered to effectively treat bilateral paranasal sinus disease without concern for increased risk of life‐threatening complications or longer hospitalization duration than would be typical for unilateral sinusotomy procedures.


INTRODUCTION
Diseases of the paranasal sinuses of the horse that may require surgery include primary sinusitis, neoplasia, equine ethmoid hematomas, sinus cysts, fistulas, trauma, mycotic infections, polyps, or dental disease (Dixon et al., 2012b;Tremaine & Dixon, 2001b). Bilateral disease is relatively uncommon, accounting for 3%-4.5% of horses with sinonasal disease, and may require bilateral paranasal sinus surgery for complete resolution (Beard et al., 1990;Coumbre et al., 1987;Dixon et al., 2011;Dixon et al., 2012a;Easley & DE, 2013;Silva et al., 2009;Tremaine & Dixon, 2001a, 2001bWoodford & Lane, 2006). Surgical approaches to the paranasal sinuses have been previously described in standing, sedated horses, with the advantages of reduced cost and lower risk of haemorrhage and complications associated with general anaesthesia (Barakzai & Dixon, 2014;Freeman et al., 1990;Quinn et al., 2005;Schumacher et al., 2000). For unilateral disease, a large frontonasal sinusostomy through the conchofrontal sinus provides improved exposure of multiple sinus compartments when compared to maxillary approaches, and the nasal passages may further be accessed through perforation of the medial wall (Freeman et al., 1990;Quinn et al., 2005;Schumacher et al., 2000). As an alternative to performing two individual flaps in cases of bilateral disease, a single, bilateral caudally based approach has been described in the treatment of bilateral mucocele in a Miniature Horse and bilateral sinus cysts in a Thoroughbred gelding (Easley & DE, 2013;Robert et al., 2019). Several studies have reported on recurrence rates and postoperative complications associated with sinusotomy in horses with unilateral paranasal sinus disease, describing long-term response to treatment for paranasal sinus disease between 12% and 92%, depending on the reason for performing surgery (Dixon et al., 2012b;Head & Dixon, 1999;Tremaine & Dixon, 2001b). However, the single, caudally based bilateral bone flap has not been evaluated relative to the unilateral frontonasal approach with respect to patient outcomes and complication rates postoperatively. As this approach represents a more recently reported modified procedure that might be rarely performed, information comparing the single, caudally based bilateral procedure to the more commonly done unilateral sinusotomy would be useful to practitioners to dispel concerns regarding instability of the bilateral sinusotomy or other postoperative complications or outcomes.
The objective of this study was to describe clinical features, complications and outcomes in horses undergoing a single, caudally based bilateral sinusotomy, and to compare those findings with horses undergoing unilateral frontonasal sinusotomy at a single academic referral centre over the same time period. We hypothesized that in the population of horses examined, horses undergoing the single, caudally based bilateral frontonasal sinusotomy would not differ in terms of postoperative complications and would have equivalent or improved rates of recurrence of clinical signs compared to those undergoing unilateral sinusotomy.

Perioperative patient management
Routine perioperative treatment included IV administration of balanced isotonic fluids at 50-100 ml/kg/day (approximately 1-2 L/h) intraoperatively or longer postoperatively depending on clinician preference and based on interpretation of laboratory findings, intraoperative blood loss, and clinical assessment. Approximately 30 min prior to surgery and for at least 3-7 days following surgery, horses received perioperative antibiotics, which included some combination of trimethoprim sulfamethoxazole (30 mg/kg PO q12h), doxycycline (10 mg/kg PO q12h), cephazolin (11 mg/kg IV q8h), and gentamicin (6.6 mg/kg IV q24h), based on the preference of the attending clinician. All horses received anti-inflammatories (either phenylbutazone (2.2 mg/kg PO q12h) or flunixin meglumine (1.1 mg/kg PO q12h)) at 30 min preoperatively and for at least 3 days postoperatively.
All procedures, unilateral and bilateral, were performed with horses standing and sedated. Horses were restrained in the stocks by an experienced handler and sedated with an initial bolus of detomidine (0.01 mg/kg IV) and butorphanol tartrate (0.01 mg/kg IV) followed by detomidine (20 mg in 1 L NaCl, titrated to effect). Prior to creating the sinusotomy incision, the skin along the edges of the proposed surgical incision site was desensitized with approximately 30 ml local anaesthetic solution (2% mepivacaine). The skin, subcutaneous tissues, and periosteum overlying the bone was incised in such a way as to overlap the bone incision by 5 mm. For both unilateral and bilateral procedures, an oscillating bone saw was used to cut the periosteum and underlying exposed bone in order to create the flap sinusotomy.
Postoperatively, blood transfusion was performed based on clinician discretion following clinical and clinicopathologic assessment during surgery (perceived volume of blood loss, heart rate, haematocrit, and lactate). Additional postoperative pain management (butorphanol tartrate 0.01-0.1 mg/kg IM) was administered based on perceived postoperative discomfort. Sinus packing was removed 1-2 days postoperatively through the nostril. Additional postoperative sinus lavage was not performed in any case.

Surgical techniques
All procedures were performed with horses standing and sedated. The surgical procedures used for unilateral frontonasal sinusotomy and the single, caudally based bilateral sinus flap were performed similarly to that previously described by Schumacher et al. (2000), Freeman et al. (1990), and Easley and Freeman (2013). In creating the single bilateral flap sinusotomy, the rostral and lateral margins are similar to the unilateral frontonasal flap described by Freeman et al. (1990), with the difference that the bilateral approach spanned both frontal bones. The skin along the edges of the proposed incision site was desensitized with approximately 30 ml 2% mepivacaine. Compatible blood donors were identified preoperatively by cross matching in all cases. Before performing the flap, two stab incisions were made at a distance of 2 cm to the right and left of midline at the caudal border of the proposed flap. A 2.0 mm Steinman pin on a hand-held chuck was used to create a hole through the frontal bone in each stab for infusion of 50 ml of 2% mepivacaine into the frontal sinuses to desensitize a portion of the sinus mucosa prior to entering the sinuses. The lateral margins were identified at approximately 2 cm medial to the medial canthus of each eye and extended rostrally two-thirds the distance from the medial canthus of the eye to the infraorbital foramen ( Figure 1). The skin and subcutaneous tissues were incised using a #20 scalpel blade to be approximately 5 mm larger than the periosteal and bone incision. The periosteum was elevated 5 mm from the site of the proposed osteotomy incision using the handle of a scalpel blade. An oscillating bone saw was used to cut the underlying exposed bone perpendicular to its surface to create the bone flap.

Long-term follow-up
Owners were contacted by telephone for follow-up information.
Information collected included general health of the horse, postoperative complications, recurrence or lack of resolution of clinical signs, and subsequent treatment following hospital dismissal if applicable.

Data analysis
Continuous data were reported as median and interquartile ranges Age did not differ between horses with unilateral and bilateral disease  Table 1.
Preoperative antibiotics administered in unilaterally operated cases were trimethoprim sulfamethoxazole (30 mg/kg PO) in 23 cases, cephazolin (11 mg/kg IV) and gentamicin (6.6 mg/kg IV) in five cases, doxycycline (10 mg/kg PO q12h) in one case, potassium penicillin (22,000 MU/kg IV) and gentamicin (6.6 mg/kg IV) in two cases, ceftiofur crystalline (0.66 mg/kg IM) in one case, and no antibiotics in one case. Preoperative antibiotics administered in bilaterally operated cases were either trimethoprim sulfamethoxazole (30 mg/kg PO) in two cases or a combination of cephazolin (11 mg/kg IV) and gentamicin (6.6 mg/kg IV) in three cases. Postoperatively, horses were treated with up to 14 days of oral antibiotics, including trimethoprim sulfamethoxazole, doxycycline (10 mg/kg PO q12h), and/or metronidazole (30 mg/kg PO q12h).
Median duration of hospitalization of horses undergoing unilateral procedures was 5 days (IQR: 4-9 days). Median duration of hospitalization of horses undergoing bilateral procedures was 4 days (IQR: 3-8 days).
Duration of hospitalization did not differ between horses undergoing unilateral or bilateral procedures (p = 0.53) (Figure 2).

DISCUSSION
This is the first study to compare outcomes of horses undergoing flap sinusotomy with either a single, caudally based bilateral or a unilateral frontonasal procedure. The results of this retrospective study demonstrate that bilateral paranasal sinus disease can be effectively treated through the single, caudally based approach described here without increased risk for life-threatening postoperative complications or duration of hospitalization. The improved visualization of the sinus compartments provided by the bilateral approach could make this procedure advantageous to rule out more extensive disease in cases where available imaging is inconclusive for bilateral involvement. All cases undergoing the bilateral procedure described here experienced full resolution of clinical signs without recurrence at the time of this clinical report despite involving more wide-spread disease processes.
Case selection and surgical technique likely also impact prognosis and probability of recurrence following sinusotomy.
Local anaesthetic applied along the intended surgical incision site and as lavage within the sinuses prior to flap creation was sufficient to desensitize the surgical region and minimize reaction during creation of the bilateral flap when cutting the dorsal septum between sinuses. Although additional analgesia for frontonasal sinus flaps has been described using maxillary or infraorbital nerve blocks, performed caudal to the pterygopalatine fossa or rostral at the infraorbital foramen, respectively, (Bardell et al., 2020;O'Neill et al., 2014;Staszyk et al., 2008;Stauffer et al., 2017) nerve blocks are not routinely performed in the authors' practice as local anaesthesia is generally con- actually demonstrating no detrimental effect on tissue healing and others indicating that there exists a differential effect depending on the type of local anaesthetic used (Abrao et al., 2014;Baxter et al., 2013;Bicer et al., 2018;Hanci et al., 2012;Kesici et al., 2018;Panneerselvam et al., 2016;Waite et al., 2010;Zeren et al., 2013). In summary, sinus lavage and local infusion were considered sufficient to perform the bilateral procedure in the cases presented.
Volume of haemorrhage that may occur when implementing the single, bilateral caudally based approach was a concern preoperatively, particularly when breaking down the underlying midline attachments between the dorsal aspect of the nasal septum and the septum between sinuses. However, haemorrhage was in most cases judged by clinicians as mild, and not more severe than can be expected through a unilateral approach in the standing position, consistent with the previous report of this technique for the treatment of mucocele in a Miniature Horse (Easley & Freeman, 2013). Intra-operative transfusion was considered necessary in one of the five cases, based on elevated pulse rate, perceived volume of blood loss during surgery, and decreasing haematocrit. This lack of additional haemorrhage may be explained in part by the disruption of normal underlying anatomy in cases with bilateral disease, as described previously (Easley & Freeman, 2013). In addition, the standing approach described here further reduces the risk of haemorrhage and is advocated by the authors in all cases if otherwise suitable for the individual patient as previously described (Schumacher et al., 2000).
Increased risk of incisional infection and dehiscence postoperatively due to interruption of the blood supply to the rostral end of the bilateral caudally based sinusotomy was also a concern with use of the bilateral approach. Postoperative incisional infection occurred in two of five cases, both of which were mild, responded as expected to oral antibiotics administered for 2 weeks and local aseptic preparation with betadine and saline lavage, and resolved completely. All horses in this case series received empirical broad-spectrum prophylactic antibiotic pre-and postoperatively. In cases of incisional infection, bacterial culture and sensitivity were not performed as infection resolved quickly.
Excessive surgical trauma or lack of perioperative antibiotic usage could also predispose to post-operative incisional infection in sinusotomy (Easley & Freeman, 2013).
The recurrence of clinical signs suggestive of sinusitis (e.g. nasal discharge) following sinusotomy procedures has been reported previously to occur in 13%-28% of unilaterally operated cases and is usually attributable to an on-going underlying problem, such as failure to remove inspissated pus from a compartment, residual presence of an intra-sinus mass, or an undetected infected cheek tooth (Quinn et al., 2005;Tremaine & Dixon, 2001a, 2001bWoodford & Lane, 2006 (Dixon et al., 2012b). It is acknowledged that true recurrence versus lack of resolution was difficult or impossible to distinguish in some of these cases as repeat CT scan was not possible postoperatively in most cases due to financial constraints. In summary, postoperative complications associated with the single caudally based flap approach were most frequently mild and not more severe than would generally be expected with a unilateral frontonasal approach based on previous reports and evaluation of our clinical population, indicating the bilateral approach may be considered safe to perform in cases with bilateral disease processes or where bilateral involvement cannot be definitively ruled out with available imaging (Barakzai, 2008;Quinn al., 2005;Tremaine, 2006 provides detailed information in assessing sinus disease in horses for a more accurate preoperative diagnosis to guide surgical planning (Easley & Freeman, 2013;Ostrowska et al., 2019;Textor et al., 2012).
Patients that experience recurrence or lack of resolution of clinical signs following sinusotomy are good candidates for CT examination if the cause of recurrence is not apparent (Barakzai & Dixon, 2014). Computed tomography scans were performed preoperatively in a similar percentage of cases (13/32 or 41% unilateral cases, 2/5 or 40% bilat- Limitations of the study include the retrospective nature of study design, relatively small number of horses evaluated that underwent bilateral sinusotomy and lack of a control group of horses that underwent two unilateral frontonasal sinusotomies. The retrospective study design restricts data collection in some instances due to the incompleteness of the medical records provided. The invoice, hospitalization report, and imaging reports were accessed to provide the most accurate representation of the data. Furthermore, this study evaluated cases of sinusitis at a single tertiary referral hospital, representing a population of horses that were selected for referral, in some cases following unsuccessful prolonged treatment by referring veterinarians. However, as active surveillance (i.e. contacting owners) was performed, it was likely that the rate of complications was accurately described.
As bilateral sinus disease is relatively uncommon, comparison of outcome parameters between different surgical centres over a longer time period may allow determination of whether the bilateral sinusotomy procedure is relatively more useful to resolve specific types of bilateral sinus disease.
In conclusion, the single caudally based bilateral frontonasal sinusotomy should be considered for surgical treatment of bilateral paranasal sinus disease as postoperative complication rates and duration of hospitalization were comparable to that described for unilateral surgery. Preoperative CT scan is recommended to definitively confirm bilateral involvement. Case selection and surgical technique likely impact prognosis and probability of recurrence following bilateral bone flap.

ACKNOWLEDMENTS
The authors would like to acknowledge the CCTSI NIH/NCATS CTSA TL1TR002533, NIH 5T32OD010437-19, and Carolyn Quan and