CLOSED INGUINAL CASTRATION TECHNIQUE COMPARED WITH FIELD CASTRATIONS


MATERIALS AND METHODS Patient selection


In a 3 month period (January to March 2021), all horses admitted to the clinic for routine inguinal castration (which is the standard in the author ' s clinic) and which proved to be clinically healthy on examina- tion, were enrolled in the study, with permission and full consent of the owners. Castrations in conjunction with another routine surgical procedure (i.e. arthroscopy) or pathological cases (i.e. inguinal her- niation) were not included.


Pre- surgical preparation


The patients are prepared for aseptic surgery under general anaes- thetic conditions in dorsal recumbency. On Day 0, prior to surgery, the horses were allowed access to wet hay or silage but received no concentrates. The horses were sedated in the stall with 0.04 mg/ kg romifidine (Sedivet 10 mg/mL, Boehringer Ingelheim), 0.02 mg/kg butorphanol (Torphadine 10 mg/mL, Dechra), and 0.02 mg/kg ace- promazine (Tranquisol P 10 mg/mL, CP- Pharma) per intravenous (i.v.) injection. Uncooperative animals were dart- sedated intramuscularly with the double dose of sedative. The sedated horses were walked to the recovery where an i.v. catheter was placed into the left jugu- lar vein through which another 0.04 mg/kg romifidine and 0.03 mg/ kg butorphanol were applied,


followed by 0.06 mg/kg diazepam


(Solupam 5 mg/mL, Dechra) and 2.2 mg/kg ketamine (Anesketin 100 mg/mL, Dechra). The horses were guided by a head rope while getting recumbent and were intubated immediately thereafter. Hoisting slings were applied to each of the four pasterns by which the horse was transported to the surgery table and positioned in dorsal recumbency, using an electric hoist running on a rail mounted to the ceiling, connecting recovery with the operating room. The penis was extracted cranially and tied to one of the extended fore- limbs, which were kept hoisted. The hindlimbs were left untied in a relaxed flexed position. The distal limbs were wrapped in clear pack- ing foil. Anaesthesia was maintained by oxygen and isoflurane (Isofluran


CP 1 mL/mL, CP- Pharma) under CO 2 absorption. Intraoperative an- algesia was achieved by the potentiating effect of the combination


of ketamine and butorphanol. Anaesthetic reports included actual


time, routine ECG, PO 2 , PCO 2 , heart rate and arterial pulse quality, capillary refill time, colour of mucous membranes, respiratory rate and depth and percentage of isoflurane. Onset of anaesthesia, onset of surgery and end of surgery and anaesthesia were indicated in the report. The inguinal site was prepared for aseptic surgery using a 4%


chlorhexidine gluconate scrub (Hibiscrub, Mölnlycke Healthcare), which was applied three times and wiped clean with 70% iso- propanol solution- soaked gauze. Preparation of the surgical site was finished by a 7.5% povidone- iodine spray (Braunol, B. Braun Melsingen), providing additional disinfection and a visible marker


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to the surgeon that the site was ready for surgery. The sterile inguinal site was draped and surgery started within 20 min after induction.


Surgical technique


The surgeon is standing next to the flank of the recumbent horse, facing caudal direction. A 5–10 cm skin incision is made over the palpable outer inguinal ring. The incision should be superficial, only cutting skin and the very thin lining of the tunica flava, avoid- ing subcutaneous blood vessels, visible underneath the thin skin. Minor haemorrhage is opposed by clamping. The underlying proxi- mal spermatic cord, caudolaterally covered by the cremaster muscle (Schumacher, 2012 ), is approached by strict blunt dissection to avoid haemorrhage from larger inguinal veins (pudendaepigastrical and in- ternal pudendal vein) using Mayo scissors in spreading fashion and digital separation of tissue. The vaginal process is hooked by a finger and retrieved by gently pulling and some pushing on the scrotum. The remaining attachment by the scrotal ligament (Schumacher, 2012 ) is separated by disruption. A Sand emasculator is then applied to the proximal part of the retrieved spermatic cord in the cranial to caudal direction just above the skin incision. The vaginal tunic, testicular artery and vein, ductus deferens and their mesenteries with lymph vessels and nerves are compressed and deformed by the emascula- tor reducing the size of the organ by squeezing out water. The Sand emasculator is left in place and the surgeon retrieves the spermatic cord similarly on the opposite side, crushing it with a second Sand emasculator. The emasculator leaves an impression on the vaginal process (Figure 1 ) after removal, which is the site of ligation with a double strand USP 1 Polyglactin 910 (Vicryl V627H, Eticon). The ligature closes the vaginal cavity and concurrently ligates the cre- master artery and vein on the caudal parietal vaginal tunic and the pre- compressed testicular artery and vein inside the vaginal cavity. The loose ends of the ligature are temporarily fixed by mosquito for- ceps, which keep the proximal pedicle retrievable. The distal part of the vaginal process including content is then cut by scissors 10 mm distal to the ligature. The cremaster muscle remnants on the proxi- mal vaginal process distal to the ligature may become necrotic and cause an inflammatory response and are therefore removed. The proximal vaginal process including pedicles is checked for haemor- rhage and released by cutting the loose ends of the ligature allowing it to contract towards the inner inguinal ring. The combined weight of the left and right removed tissue, being a measure of the size of the removed organs which have been related to complication rate (Birrell et al., 2020 ), was measured by an assistant on an electronic balance for future testing of the possible relation between p.o. SAA and the sum of weight of the organs. Wound closure was performed by adapting sub- cutaneous tissue and tunica flava in a simple contin- uous pattern using preferably monofilament USP 2- 0 Poliglecaprone 25 (Monocryl plus MCP589H, Eticon) or alternatively a braided USP 2- 0 Polyglactin 910 (Vicryl Plus VCP9900H or Vicryl JV586, Eticon) suture with swaged cutting needle. The same suture was used to


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