EQUINE DENTAL SINUSITIS
Procedures Dental extraction
Standing oral extraction was performed by various surgeons at HTK. Sedation and perioperative analgesia were administered at the discretion of the surgeon in charge with some horses re- ceiving
intraligamentary infiltration with local anaesthetics
(Lidocaine hydrochloride/adrenalin 20 mg + 0.0125 mg/mL) and some horses receiving maxillary nerve blocks (Teysen et al., 2020 ; Tremaine, 2007 ). The procedure was performed as described by Gieche ( 2020 ). In some cases, MTE was necessary to fully extract the tooth (Langeneckert et al., 2015 ). In the majority of horses, a plug of super-hydrophilic impression material (Splash Putty packs by Denmat) was placed in the alveolus with only a few exceptions. All horses received postoperative analgesia provided by flunixin (1.1 mg/kg s.i.d. PO) for a minimum of 3–5 days. Horses receiving perioperative AB (immediately pre-operatively or postoperatively) were administered either Trimethoprim/Sulfadiazine (TMP-sulfa; Oral paste 30 mg/kg b.i.d.) or procaine benzylpenicillin (20 mg/ kg i.m. s.i.d. or 10.000–20.000 IE/kg i.m. s.i.d.) for 5–10 days. The choice, whether to administer antibiotics or not, was based on the surgeon ' s preference.
Trephination of the sinus
In cases where debridement or further inspection of the sinus was needed a trephination as described by Perkins et al. ( 2009 ). To remove any material from the sinuses such as inspissated pus and/ or liquid exudate, the sinuses were lavaged thoroughly with luke- warm water. The incision was closed based on preference of the surgeon; either in two layers where the periosteum was closed in a simple interrupted pattern using an absorbable suture and the skin was closed with staples or in one layer only closing the skin using staples. The incision was bandaged using gauze swabs and tensoplast. Postoperative management was identical to den- tal extraction, except antibiotics were used in all cases of sinus trephination.
Transnasal lavage
In cases where sinus lavage was considered indicated and where the sinus could be approached nasally through the drainage angle, a 7.9 mm diameter flexible endoscope (SILVER SCOPE®) was used to perform transnasal
lavage. After accessing the middle nasal
meatus, the ethmoid region and the nasomaxillary aperture were visualised, and the paranasal sinuses were lavaged. If the natural opening to the sinuses was too narrow for the endoscope to ac- cess, inspissated pus, if any, was removed by lavage from within the middle meatus.
Treatment outcome
Initially, all horses were treated by means of dental extraction with or without AB. A treatment was considered successful if clinical signs resolved regardless of short-term complications such as pain, anorexia and lethargia. All of these complications were considered to be minor complications to the dental extraction. If a horse did not respond to initial treatment (continued nasal discharge), fur- ther treatment was initiated. Further treatment was either re- moval of alveolar sequestrae, administration of AB, change of AB, transnasal lavage or sinus trephination surgery (Figure 1 ). When a horse was subjected to more than one MSFF sinus trephination surgery, the following lavages were performed through an already existing opening. Treatment outcomes were defined based on whether horses were successful after one, two or three or more treatments or if the horse ended up being unsuccessful or sub- jected to euthanasia regardless of whether they received one, two or three or more treatments. Treatment outcomes were defined based on whether horses were successful following initial treat- ment, or if further treatment was required for the horses to be- come free of clinical signs.
Data analyses
For statistical analysis, the treatment outcomes were considered as binary-dependent variables and were categorised as ‘ successful ’ and ‘ unsuccessful ’ solely based on the response to initial treatment. The outcome variable ‘ successful ’ included horses from the group ‘ suc- cess after first treatment’ . The outcome variable ‘ unsuccessful’ group included the three remaining groups, that is, ‘ success after second treatment’, ‘success after three or more treatments’ and ‘unsuccessful/ no further treatment’ . Furthermore, horses were divided in two sub- groups called the ‘Antibiotics’ group and the ‘No-antibiotics’ group based on whether or not they received perioperative AB along with the dental extraction. The other categorical variables included ‘Breed’ (Warmblood, Coldblood, Pony or Thoroughbred), ‘Duration’ (Subacute or Chronic), ‘Tooth’ (08 ' s, 09 ' s, 10 ' s, 11 ' s or several teeth), ‘Extraction method’ (Standing oral extraction or MTE) and ‘Prior Antibiotics’ (yes or no). The variable ‘age’ was included as a numeri- cal variable. For all statistical analyses, the level of significance was set at 5% (Table 1 ). To analyse which categorical variables had a significant associa-
tion with success, a univariate analysis with Fishers exact test was performed by using the R function fisher.test . Also, to assess and determine any potentially confounding effects between AB and the other categorical variables (Breed, Duration, Extraction method, Tooth, Prior antibiotics), each variable was tested separately again by employing Fishers exact test to trace its effect on the likelihood of AB administration. The numerical variable ‘age’ could not be assumed to follow a normal distribution. Consequently, associations between age
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