Comparative strength of ligature points achieved by various surgical knot-tying techniques: an observational study using Maxon™ monofilament sutures

PURPOSE

Surgical knot-tying requires careful selection of the appropriate technique for optimal outcomes; however, evidence is lacking about the common ligation techniques combining square and slip knots (combination knots). This study investigates the strength of a combination knot, compared with other techniques.

METHODS

In this observational cohort study, we assessed the strengths of square, slip-granny, slip-reef, and combination knots using absorbable monofilament sutures, and compared them using ANOVA and a multilevel linear regression analysis. We also assessed the correlation between the number of throws and knot strength using Spearman's correlation analysis.

RESULTS

Among 80 ligatures, ANOVA indicated significant differences in knot strength among the techniques (p < 0.01). Multilevel linear regression showed that a combination knot was stronger than a slip knot (p < 0.01) and comparable to a square knot (p = 0.0721). Secondary analysis indicated that for combination knots, five throws could achieve sufficient knot strength.

CONCLUSION

Combination knots are as strong as square knots and stronger than slip knots, and thus present a reasonable option for surgical ligation.

Influence of a single locking throw on the in vitro holding security of five friction throws

OBJECTIVE

To compare the in vitro security of four different friction throws (square, surgeon's, Miller's, and strangle), with and without a locking throw, and a slip knot, on a vascular ligation model.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Nine groups with nine samples per group.

METHODS

Four throws (square, surgeon's, Miller's, and strangle), with and without a locking throw, and a square throw locked in slip knot fashion, were tested to measure leakage pressure.

RESULTS

The square and surgeon's throws leaked at a lower pressure than the Miller's and strangle throws (p < .0001). The leakage pressure was below physiologic arterial pressure for the square and the surgeon's throws. After the addition of a locking throw, the five knots leaked at a similar pressure (p = .5233) above physiologic arterial pressure.

CONCLUSION

Following the addition of a locking throw, all the constructs tested in this study leaked at a similar pressure. The leakage pressure for all knots exceeded physiologic arterial pressures.

CLINICAL SIGNIFICANCE

Any throw tested may be appropriate for secure vascular ligation if the initial throw is applied correctly.

Comparison of Hemorrhagic Complications with Double-ligated versus Auto-ligated Feline Ovarian Pedicles by Fourth-Year Veterinary Students

The objective of this article is to compare the occurrence of hemorrhagic complications in student-performed feline ovarian pedicle ligations using the traditional suture pedicle double-ligation (PDL) to the suture-less auto-ligation (AL) techniques, and to describe the stepwise method of teaching the AL technique to students. A total of 287 cats underwent an ovariohysterectomy (OHE) performed by a fourth-year veterinary student trained by veterinary faculty to perform the AL technique beginning with a low-fidelity model and progressing to live patient surgeries. Students performed the AL and PDL techniques on 146 and 141 cats respectively. Hemorrhagic complications occurred in 4 of 146 cats (2.7%) in the AL group and 8 of 141 (5.7%) in the PDL group and were not found to be significantly different (p = 0.2496). This article demonstrates that novice surgeons can safely perform the AL technique on feline ovarian pedicles without significantly increasing complications compared to the traditionally taught method when a stepwise training program is implemented. Additionally, this technique has been shown to be safe, effective, and more efficient when performed by experienced veterinary surgeons.¹ Veterinary institutions should consider including the AL technique in their core curricula as a standard method for feline ovarian pedicle ligation. Doing so will facilitate the development of more proficient entry-level practitioners who are better able to serve their patients, clients, employers, humane societies, and their communities by using a more efficient and safe feline ovariohysterectomy technique.

Comparison of the incidence of intra-operative haemorrhage from ovarian vessels during ovariectomy and ovariohysterectomy of dogs and cats performed by inexperienced surgeons using surgeon's and constrictor knots

Aims: To compare the incidence of intra-operative haemorrhage from ovarian vessels during ovariectomy (OV) and ovariohysterectomy (OVH) in dogs and cats performed by inexperienced surgeons using surgeon's and constrictor knots to ligate the ovarian pedicles.Methods: All client-owned female dogs (n = 51) and cats (n = 102) that presented for OV or OVH at two referral clinics in Belgium and France from January to June 2019 were included. Surgeries were performed by inexperienced surgeons under the supervision of diplomates or residents of the European College of Veterinary Surgeons. During routine and emergency OV or OVH one pedicle of each animal was ligated using a constrictor knot and the other with a surgeon's knot, the side assigned randomly. Time taken to perform each knot and the number of ligatures that resulted in intraoperative haemorrhage from the ovarian vessels were recorded. Body condition score (BCS) was recorded for 33 dogs and 22 cats.Results: The median time taken to perform constrictor knots in dogs (81 seconds), was longer than for surgeon's knots (69 seconds; p = 0.005). In cats, the median time taken to perform constrictor knots (109 seconds) was also longer than for surgeon's knots (90.5 seconds; p = 0.02).The number of dogs that had intra-operative haemorrhages from pedicles ligated with constrictor knots (2/102; 3.9%) was less than those ligated with surgeon's knots (10/102; 19.6%; p = 0.027). The median BCS of dogs that experienced haemorrhage (n = 8; median 5/9, min 3/9, max 7/9) was higher (p = 0.019) than that of dogs that did not experience haemorrhage (n = 25; median 4/9, min 3/9, max 8/9).There was no evidence (p = 1.0) of a difference in the proportion of cats that experienced intra-operative haemorrhage from pedicles ligated with constrictor knots (3/44; 6.8%) and those ligated with surgeon's knots (2/44; 4.5%). Two-thirds of the haemorrhages with constrictor knots were caused by pedicle rupture during tightening.Conclusions: The rate of intraoperative haemorrhage from the ovarian pedicle was lower when a constrictor knot was used compared to a surgeon's knot in dogs but not in cats. While the constrictor knot was more time consuming to tie this is not likely to have a clinical impact. Use of this knot by inexperienced surgeons in dogs may help to reduce the risk of intraoperative haemorrhage during OVH/OV.

In vitro holding security of four friction knots of monofilament or multifilament suture used as a first throw for vascular ligation

OBJECTIVE

To evaluate holding security of 4 friction knots created with various monofilament and multifilament sutures in a vascular ligation model.

SAMPLE

280 friction knot constructs.

PROCEDURES

10 friction knots of 4 types (surgeon's throw, Miller knot, Ashley modification of the Miller knot, and strangle knot) created with 2-0 monofilament (polyglyconate, polydioxanone, poliglecaprone-25, and glycomer-631) and braided multifilament (silk, lactomer, and polyglactin-910) sutures were separately tied on a mock pedicle and pressure tested to the point of leakage. Linear regression analysis was performed to compare leakage pressures among suture materials (within friction knot type) and among knot types (within suture material).

RESULTS

Mean leakage pressure of surgeon's throws was significantly lower than that of all other knots tested, regardless of the suture material used. All the other knots had mean leakage pressures considered supraphysiological. Significant differences in mean leakage pressure were detected between various friction knots tied with the same type of suture and various suture types used to create a given knot. Variability in leakage pressure among knots other than the surgeon's throw was greatest for poliglecaprone-25 and lowest for polydioxanone.

CONCLUSIONS AND CLINICAL RELEVANCE

Most differences in knot security, although statistically significant, may not have been clinically relevant. However, results of these in vitro tests suggested the surgeon's throw should be avoided as a first throw for pedicle ligation and that poliglecaprone-25 may be more prone to friction knot slippage than the other suture materials evaluated.

In vitro holding strength of the laparoscopic Miller's knot compared with open Miller's knot, open surgeon's throw, and laparoscopic surgeon's throw in a vascular pedicle model

OBJECTIVE

To compare in vitro knot holding strength of the laparoscopic Miller's knot (LMK), open Miller's knot (MK), open surgeon's throw (Sx), and laparoscopic surgeon's throw (LSx) in a vascular pedicle model when used as the first throw for vascular ligation.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Ten constructs each of the Miller's knot and surgeon's throw performed openly and laparoscopically with 2-0 polyglyconate suture.

METHODS

Knot holding strengths of the LMK, MK, LSx, and Sx knots were evaluated on balloon dilation catheters used as vascular pedicle models. Laparoscopic knots were tied in a laparoscopic box trainer. Knot constructs were pressure tested to failure. Results were compared by Kruskal-Wallis and Steel-Dwass comparisons.

RESULTS

Both MK and LMK had mean leakage pressures above 300 mm Hg. The MK leaked at higher pressure than all other knots, including the LMK (P < .001). The LMK leaked at greater pressures compared with the Sx and the LSx (P < .001). No difference was detected between leaking pressures of the Sx and the LSx (P = .226), with both leaking at pressures below 40 mm Hg.

CONCLUSION

The LMK created a more secure first throw compared with the Sx and leaked at supraphysiologic pressures.

CLINICAL SIGNIFICANCE

The LMK has excellent knot holding strength on a vascular pedicle model and may be further evaluated for clinical application.

Shunt disconnection is less likely using a surgeon's knot compared with a surgical constrictor knot

INTRODUCTION

Ventriculo-peritoneal shunt malfunction is a common neurosurgical presentation, which may occur as a result of shunt disconnection at the level of the valve. Previous studies assessing ligatures have suggested that the constrictor knot is stronger in securing a ligature compared to the surgeon's knot. Our study compared the ability of each knot to secure shunt tubing to the valve.

METHODS

A medtronic shunt valve was secured to a peritoneal catheter using the surgeon's knot versus constrictor's knot. The weight and subsequent force (N) required to pull off the shunt tubing at the knot site were recorded.

RESULTS

The mean pull-off force was 11.7 N for the surgeon knot, and 8.9 N for the constrictor knot. There was significant difference in favour for the surgeon's knot compared to the constrictor knot.

CONCLUSIONS

The surgeon's knot is significantly stronger than the constrictor knot for securing a peritoneal catheter to a CSF shunt valve.

Guidelines for Implementing a Low-Cost Volunteer Desexing Skills Training Program for Veterinary and Veterinary Technology Students

Although desexing surgeries are considered a core clinical skill for small animal veterinary practice, it can be challenging for veterinary schools to provide students with adequate training opportunities in the traditional curriculum. At the Massey University School of Veterinary Science, we recently established an innovative extracurricular volunteer program designed to have students teaching other students how to perform different elements of desexing procedures as they progress through their degree. This program includes administrative and assistant roles for first-year students (responsible for client communication, patient restraint, and medical record keeping), physical exam and recovery roles for second-year students (responsible for assessing patient fitness for surgery, drawing up anesthetic drugs, and monitoring patients in recovery), anesthesia and neuter surgeon roles for third-year students (responsible for inducing, preparing, and monitoring spay patients and performing cat neuter surgeries), and spay surgeon roles for fourth- and fifth-year students (responsible for performing cat spay surgeries, discharging patients, and following up with clients to monitor recovery). This program has been successful in improving student confidence and competence while also providing a valuable low-cost desexing service to the community. In this article, we discuss the practical considerations and processes involved in implementing this program, including mapping the existing surgical curriculum, recruiting patients, setting up the surgical facilities, purchasing equipment and supplies, establishing standard operating procedures, developing training materials, maintaining clinic records, and monitoring program outcomes. These resources can serve as guidelines for other veterinary schools looking to expand desexing surgery training opportunities for students.

Evaluation of three ligatures in simulated equine open castration

OBJECTIVE

To compare three surgical knots for preventing leakage from the vascular bundle during ligation in simulated equine open castrations.

STUDY DESIGN

Randomized, case-control, in vitro study.

SAMPLE POPULATION

Testes (N = 60) collected from 30 horses.

METHODS

Testes were collected from 30 horses and randomly assigned to one of three groups: group G (friction, giant knot), group T (modified transfixing knot), or group S (sliding, strangle knot; n = 20/group). The assigned knot was used to ligate the vascular bundle during open castration. The length of suture material used and the leak pressure of the testicular artery were measured and compared between groups.

RESULTS

Strangle knots consistently leaked at higher pressures (median, 735.5 mm Hg; interquartile range [IQR], 735.5-735.5) compared with giant (median, 441.3 mm Hg; IQR, 367.8-643.6) and transfixing (median, 419.2 mm Hg; IQR, 323.6-643.6; P < .0001) knots. Both the strangle (median, 5 cm; IQR, 4.5-5.5) and giant (median, 6 cm; IQR, 5.35-6.075) knots required less suture material compared with the transfixing (median, 9.2 cm; IQR, 8.425-10.38; P < .0001) knot.

CONCLUSION

The three surgical knots tested withstood pressure well above physiological levels in simulated open castrations. The strangle knot withstood higher pressure and required similar (giant) or less (transfixing) suture material than the other two knots.

CLINICAL SIGNIFICANCE

This study provides evidence to support the use of a strangle knot to ligate the vascular bundle during simulated open castrations in horses.

Cross-sectional survey of surgical techniques used to perform dog and cat spays in New Zealand veterinary practice

Aims: To describe the variation in surgical techniques used by veterinarians to perform routine dog and cat spays in first-opinion veterinary practice in New Zealand, and how these techniques differed with the number of years since the veterinarian graduated.Methods: A cross-sectional survey of veterinarians registered to practice in New Zealand was conducted online between 1 April and 30 May 2018. Respondents were asked their year of graduation and about the procedures, they would use to perform a routine spay of a healthy, 5 kg, young adult, female domestic shorthair cat, and a healthy, 20 kg, young adult, female mixed-breed dog. The number of years since graduation was calculated by subtracting the reported year of graduation from 2018.Results: Overall, 282 respondents provided details about dog spays, and 361 about cat spays, and the median number of years since graduation was 14 (min 0, max 50). Only 54/282 (19.1%) respondents performing dog spays and 43/361 (11.9%) performing cat spays wore a surgical cap, gown, mask, and gloves. For dog spays, 278 (98.6%) respondents used a ventral midline approach and 147 (52.1%) used manual exteriorisation of the uterus. Most used two clamps (168; 59.6%) and used two encircling ligatures (152; 53.9%) for removal of the uterus. For cat spays, 254 (70.4%) respondents used a ventral midline approach and 313 (86.7%) used a spay hook for exteriorising the uterus. Most used two clamps (250; 69.3%) with one encircling ligature (213; 59.0%) for removal of the uterus. Simple interrupted external or intradermal patterns were mostly used for skin closure for both dog and cat spays. For cat spays, the percentage of respondents using the ventral midline approach decreased with increasing years since graduation (p < 0.001). For both dog and cat spays, the percentage of respondents using two encircling ligatures and transfixation ligation of the uterus, and using a simple continuous suture pattern for the closure of the abdomen, decreased with number of years since graduation (p < 0.05).Conclusions and clinical relevance: Veterinarians responding to this survey used a wide range of techniques to perform routine dog and cat spays, some of which were associated with the number of years since graduation. It may be beneficial to provide veterinarians with resources to reflect on their current approaches for performing routine spays. However further research is needed to determine whether any surgical techniques are superior to others.