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EQUINE VETERINARY EDUCATION / AE / AUGUST 2019


reviewed, and based on the type of castration performed, 30 horses were assigned to Group 2 (field control group) and 30 horses to Group 3 (primary closure castration). Group 2 (‘field’ control group) included only horses that


underwent routine field castration under injectable general anaesthesia either on a farm or in the OVC arena without any suture with the incisions left open to drain. Group 3 included 30 horses that underwent primary


closure castration in the operating room at the OVC Large Animal Referral Hospital as the ‘cleanest environment’ control group.


Surgical Procedures Group 1 – closed castration with transfixation Horses were placed in lateral recumbency on either straw, grass or sand with the upper leg tied. Liquid soap and water were used to wash the surgical field, then the area was dried with clean lap sponges. Depending on the anaesthesia research, the testicles were injected with lidocaine injection (lidocaine 2% HCl, 10–15 mL/testicle based on size) or an equal volume of saline (Sinclair et al. 2013). The testicles were pushed into the scrotum with one hand until the skin was taut. Using a scalpel, an incision was made parallel to the median raphe through the scrotal skin, tunica dartos and scrotal fascia until the parietal tunic was encountered. The testicle, still encapsulated by the parietal tunic, was grasped, and the scrotal fascia was ‘stripped’ (separated using a sterile gauze) from the parietal tunic until the cremaster muscle and tunic were fully exposed. In horses 2 years of age or older, the cremaster muscle was separated from the parietal tunic encasing the spermatic cord for a length of 3 or 4 cm and Serra emasculators were applied to the cremaster muscle and left in place for 30 s. Kocher forceps were then applied to the edge of the spermatic cord, close to the body wall. Approximately 3 cm distal to the body wall, a transfixation suture using No. 2 polyglactin 910 (coated VICRYL)1 was applied to the spermatic cord (including the cremaster in horses under 2 years) in the following manner: For the single knot ligature, the suture material was fixed through approximately 2 mm of the vaginal tunic in order to prevent slippage of the suture, and held in place with a simple throw, and then the suture material was looped around the spermatic cord, fixed with a surgeon’s knot, and followed by three more throws. Next, Serra emasculators2 were applied approximately 1.5 cm distal to the transfixation suture and held in place for at least 2 min. In horses with large spermatic cords (either over 650 kg or active breeding stallions), the emasculator was held in place for 3 min and then removed. The surgical site was checked for bleeding, and the other testicle was castrated in the same fashion. All castrations were performed by one of two board certified surgeons.


Group 2 – unsutured castration Horses were anaesthetised as described above. Horses were placed in lateral or dorsal recumbency based on surgeons’ preference on either straw, grass or sand with the upper leg (lateral) or both legs (dorsal) tied. The same preparation and the same approach were used as described above for closed castration, except that no transfixation suture was placed. All castrations were performed by one of two board certified surgeons.


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Group 3 – primary closure castration For the in-clinic castrations, a 14-gauge i.v. jugular catheter (BD Insyte -W)3 was routinely placed sterilely. All horses were medicated with xylazine (0.8–1 mg/kg bwt i.v.)4 as required to move into the induction stall. Anaesthesia was induced with ketamine (2 mg/kg bwt i.v.)5 and diazepam (0.02–0.04 mg/kg bwt i.v.)6, and horses were orotracheally intubated and maintained on isoflurane (Isoflurane USP)7 in oxygen via a circle rebreathing system. The surgical field was aseptically prepared, and after draping, scrotal skin incisions were made as described above and a closed castration technique with transfixation suture (absorbable suture material used was based on surgeons’ preference) was used. After ensuring that there was no bleeding from the transected cords, the median raphe was resected. Two deep fascia/subcutaneous layers were sutured using a continuous suture pattern to obliterate dead space. Then, an intradermal suture pattern was used. An absorbable suture material used for the three layers was based on the surgeons’ preference (Cox 1984). All castrations were performed by one of five board certified surgeons. The following information was collected: age, breed,


surgeon, position in surgery, volume of lidocaine injected into the testicle, medications used, surgery time in minutes, recovery score from anaesthesia and suture used. Follow-up post-operative information was obtained by telephone survey of owners or trainers (2014–2016) and included the following complications: scrotal swelling, excessive haemorrhage, omental herniation, intestinal herniation, incisional infection and septic funiculitis. Scrotal swelling was defined as swelling of the scrotal area/prepuce severe enough to require veterinary attention. Excessive haemorrhage was defined as post-operative bleeding requiring veterinary intervention by either packing of the surgical site or ligation of a vessel to stop the bleeding; incisional infection was defined as scrotal/ preputial swelling severe enough to require opening of the incisions and antibiotic treatment by the treating veterinarian; septic funiculitis was defined as infection of the remainder of the spermatic cord requiring referral to a surgical facility and necessitating surgical removal of the stump and debridement (Mason et al. 2005; Schumacher 2012).


Statistical analysis The data were analysed with SAS 9.48. Variables included nominal (surgical technique, breed,


surgeon, positioning during surgery (dorsal/lateral), type of suture, medications used) and discrete variables (duration of surgery in minutes, age in years, dose of lidocaine, number of complications). The recovery score (1–4) and most discrete variables were initially handled as continuous variables, but on occasion (e.g. age) grouped as categorical variables (e.g. age 1, 2, 3 + ) for further analysis. Complications (scrotal swelling, haemorrhage, omental or intestingal herniation, incisional infection or scirrhous cord) were recorded in dichotomous fashion (not/observed) and summarised as number of complications and dichotomous complications (yes/no). Categorical observations were summarised with frequency statistics (PROC FREQ) or summary statistics for continuous variables (PROC MEANS). Fisher-exact tests for categorical variables (e.g. age group (1, 2, 3 + ) and surgical approach) or ANOVA for continuous variables (e.g. surgical approach and duration of surgery). Alpha was set at ≤0.05.


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