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EQUINE VETERINARY EDUCATION / AE / AUGUST 2019
TABLE 2: Detailed description of type of suture used for primary closure castration
Suture type Suture size
Lactomer 9-1/ Polyglactin (Polysorb)12
Glycomer 631 (Biosyn)12
Polyglyton 6211 (Caprosyn)12
Polydioxanone (PDS)13
Transfixation suture
No. 1 or No. 2 18
Deep tissue layers
No. 2.0 or No. 3.0 2
326 22 50
Intradermal No. 2.0 or No. 3.0
2 24 4 0
prolonged injectable techniques on room air (McCarty et al. 1990; Mama et al. 2005). Consequently, an increase in anaesthetic complications with inhalational anaesthesia compared to injectable anaesthesia may arise (Johnston et al. 2002). Also, a longer surgery time may increase the risk of infection and provide an explanation why post-operative infection rate in Group 3 was so much higher. In Group 1, the closed castration with transfixation had
of suture used (braided, monofilament or no suture) did not influence the occurrence of post-operative complications in this study.
Discussion
This is the largest study to date to compare the occurrence of post-operative complications of three different castration techniques. The results of our study support our hypothesis that using a closed castration technique with transfixation using a multifilament suture material (No. 2 polyglactin 910) under field conditions did not result in more post-operative complications than a closed field castration technique without suture or a primary closure castration in a hospital setting. In fact, almost twice the number of horses in the primary closure castration group (Group 3) had post-operative complications (n = 7in comparison to the field castrations Group 1; n = 3 and Group 2; n = 4, respectively), particularly swelling of the surgical site. Unfortunately, the statistical power of our study was too low to detect a significant difference between complications in the three groups as a power analysis indicates that 200 horses per group would be necessary to detect this 11–13% risk difference in post-operative complications. Despite the overall lack of significance in our study for specific complications, application of a transfixation suture did not prolong surgery or anaesthesia time, and anaesthetic recovery scores were comparable between Group 1 and Group 2 with injectable anaesthesia. Considering this, transfixation is a viable option for equine practitioners under field conditions as a strategy recommended to reduce the risk of serious post-operative complications such as evisceration (Moll et al. 1995; Schumacher 1996, 2012). However, this recommendation is only applicable to horses being anaesthetised under field condition. An evaluation of the transfixation technique in castrations performed under standing sedation, would provide additional useful information. It is important to consider the option of transfixation for field
castrations, especially for draught and Standardbred horses which reportedly have higher rates of evisceration (Moll et al. 1995; Schumacher 1996), as there are disadvantages to primary closure castrations. A primary closure castration is significantly more expensive and takes a significantly longer time to perform than either transfixed closed or unsutured closed castration. With an increased length of surgery time over 60 min, supplemental oxygen or general inhalant anaesthesia is recommended to support hypoventilation and the development of hypoxaemia reported in horses with
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three horses with post-operative signs of infection. Two of them resolved with antibiotic treatment, and one continued to have issues necessitating surgical removal of the infected spermatic cord (funiculitis). Interestingly, even though statistically not significant, in the primary closure castrations (Group 3) performed in the operating room, were five horses with post-operative infection, and three resolved with medical therapy, but two needed surgical removal of the infected cord. Post-operative infection rates were reported to range from 2.1% in castrations performed in an operating theatre under sterile conditions to 20.7% in standing castrations (Mason et al. 2005). There are only minor differences in technique that do not explain why the post- operative infection rate in Group 3 was so much higher than reported by described by Mason et al. 2005. In the former study cat gut was used instead of Vicryl to transfix the spermatic cord, but the other tissue layers in our study were sutured with similar material and suture pattern, except for the skin in Masons report, which was only sutured with three interrupted sutures instead of a continuous pattern. In one report where researchers used a questionnaire to obtain details about castration technique and post-operative complications in 23,229 horses, respondents felt that there was a significant rate of infection (13.5%) in using a ligature versus no ligature (2.8%) (Moll et al. 1995). This was only the impression of the 31 respondents that routinely used a suture around the spermatic cord and it is unclear what surgical castration technique was used in these cases and if this was performed standing or recumbent. Standardbred horses (except for one draught colt) were
the main breed in our primary closure castration Group 3, which is not surprising as Standardbred or draught horses are the breeds most commonly referred for primary closure castration at our clinic. In Standardbreds, an excessive size of the inguinal rings was perceived to be responsible for a higher rate of evisceration but was reported to only occur in less than 1% of horses (Moll et al. 1995). Furthermore, a recent study in draught foals reported a much higher rate of evisceration (4.8%) independent of open or closed castration technique (Shoemaker et al. 2004). A recent ex vivo study showed that use of a transfixation technique in closed castration resulted in significantly higher parietal tunic tensile strength and should be used to reduce the risk of evisceration (Comino et al. 2016). Similarly, a technique using a pretied loop (4S modified Roeder knot) of 1 polyglyconate (Maxon) placed over the emasculator and tightened around the common vaginal tunic and attached cremaster muscle (Carmalt et al. 2008), reduced the incidence of post-castration evisceration in draught foals (Carmalt et al. 2008). Another controversy exists about whether the placement
of a transfixation suture can reduce the risk of post-operative haemorrhage. A transfixation knot (Rijkhenuizen et al. 2013) or modified Roeder knot (Carmalt et al. 2008) has been recommended as the optimal method to use in castration.
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