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J Vet Clin 2022; 39(6): 311-318

https://doi.org/10.17555/jvc.2022.39.6.311

Published online December 31, 2022

Cadaveric Feasibility Study of Knotless Barbed Suture for Tracheal Anastomosis in Dogs

Hyeon-Ah Min , Chang-Hwan Moon , You-Jeong Jeong , Hae-Beom Lee , Dae-Hyun Kim , Seong Mok Jeong

Department of Veterinary Surgery, College of Veterinary Medicine, Chungnam National University, Daejeon 34134, Korea

Correspondence to:*jsmok@cnu.ac.kr

Received: November 1, 2022; Revised: December 6, 2022; Accepted: December 8, 2022

Copyright © The Korean Society of Veterinary Clinics.

Appropriate suture technique is crucial for successful tracheal anastomosis. However, standards for an ideal suture method have not yet been established. A previous study suggested tracheal anastomosis using barbed sutures that do not require knots; however, their use in small animals has not been reported. In this study, we aimed to compare knotless barbed sutures with conventional smooth sutures in terms of maximum tensile strength and suturing time in canine tracheal models to demonstrate the feasibility of using barbed sutures in tracheal anastomosis in dogs. Tracheal segments harvested from nine beagle dog cadavers were randomly assigned to three suture groups: barbed suture (B), smooth suture in simple interrupted pattern (SI), and smooth suture in simple continuous pattern (SC). The maximum tensile force and suturing time were compared according to the suturing method, and the mode of failure was evaluated. The average suturing time was 3.29 min in the B group; 4.41 min, SC group; and 8.99 min, SI group (p < 0.001). The average maximum tensile force in the SC group was 134.97 N, which was stronger than the SI (110.57 N) and B groups (103.10 N) (p < 0.05 and p < 0.01, respectively). The difference between the B and SI groups was not significant (p = 0.05). The B group demonstrated comparable mechanical strength and shorter suture time compared with the SI group. Therefore, tracheal anastomosis using barbed sutures could be an effective alternative to conventional smooth sutures in dogs.

Keywords: barbed suture, dogs, suturing time, tensile force, tracheal anastomosis.

Tracheal resection and anastomosis is a surgical procedure to remove a portion of the tracheal segments and then reconnect the ends (16,17). It is performed to correct various forms of tracheal stenosis, such as tracheal trauma, irreparable damage to tracheal portions, tracheal avulsion, and tracheal masses (2,15,16,39). Although some degree of luminal stenosis is inevitable after surgery, incorrect anastomosis and excessive strain at the anastomosis site are significant risk factors for the development of critical stenosis (2,10,16,22,23,36). Therefore, the suture technique to minimize anastomotic tension and achieve precise apposition is crucial for surgical success in tracheal resection and anastomosis.

Numerous studies have been conducted to select appropriate suture methods in small animals (3,11,15,22). Nevertheless, controversy remains over which suture materials and patterns are ideal for tracheal anastomosis (3,5,18,24). The continuous pattern has advantages in tension distribution and the interrupted pattern in tissue alignment and airtightness, and both suture patterns are applicable to tracheal anastomosis (3,5,10,14). Suture materials are typically determined by the operator’s preference because they are less important than suture patterns with regard to complications and prognosis in tracheal anastomosis (3,10,18). Although various sutures can be used for tracheal surgery, monofilament absorbable sutures are recommended because of the reported association between the use of multifilament nonabsorbable sutures and a high complication rate (18,32). However, the sutures must be strong enough to provide the mechanical support required for anastomosis (36).

Barbed sutures have small projections on their surface, providing an even tension distribution and suture anchor points (25,33). The presence of barbs obviates the need for knots and reduces pressure on the tissue over a larger contact area (26,31). Consequently, it overcomes the issues of overtightening knots and knot stimulations in traditional smooth sutures (19,21,34,41). Accordingly, the application of barbed sutures has been studied in various fields of veterinary medicine (13,19,27,37,40). Barbed sutures are expected to be effective in tracheal resection and anastomosis, where accurate alignment and proper tension distribution are closely associated with surgical prognosis (4,23,30,36). However, to the best of our knowledge, the application of barbed sutures in canine tracheas has not yet been reported. Although tracheal anastomosis using barbed sutures has been suggested in previous human medical research, differences exist in the patterns and threads between the compared sutures (7). In addition, because of the differences in the mechanical strength of the trachea between species (11), evaluation of the use of barbed sutures in dogs based on human studies is inappropriate.

This study aimed to compare knotless barbed sutures with conventional smooth sutures in terms of maximum tensile strength and suturing time of tracheal anastomosis on canine tracheas harvested from cadaveric dogs to demonstrate the feasibility of using knotless barbed sutures for canine tracheal resection and anastomosis. We hypothesized that barbed suture tracheal anastomosis would result in faster closure time and comparable tensile force than smooth suture tracheal anastomosis, and that the use of barbed suture would be feasible for canine tracheal resection and anastomosis.

Specimen preparation

We obtained nine adult beagle dog cadavers euthanized for reasons unrelated to this study. The dogs were confirmed to be healthy with no underlying medical conditions. The trachea from the cricoid cartilage to the carina was harvested within 2 h of euthanasia. The remaining soft tissue adherents were carefully removed while preserving the dorsal tracheal membrane. Each trachea was divided into thirds, and the length and diameter of each segment were measured. Tracheal segments were labeled, individually immersed in 0.9% NaCl solution, and refrigerated at 4°C before resection and anastomosis.

Tracheal resection and anastomosis

The three tracheal segments were equally distributed and randomly assigned to three suture groups according to the applied suture pattern. The three suture groups were the barbed suture (B), smooth suture in a simple interrupted pattern (SI), and smooth suture in a simple continuous pattern (SC). Each tracheal segment was excised and anastomosed using the split-cartilage technique. The middle tracheal ring of the segment was circumferentially split using a #11 blade. Sutures were placed around the divided tracheal ring, starting at one edge and exiting the other edge. Suture bites were taken uniformly at regular intervals of 3-5 mm. The dorsal membrane was sutured at the same level as the cartilage. A single surgeon conducted all the procedures with one assistant. During and after resection and anastomosis, all tracheal constructs were soaked and stored in 0.9% NaCl solution at 4°C until mechanical testing.

The B group was anastomosed using USP 3-0, unidirectional barbed V-LocTM 90 suture (V-LocTM Wound Closure Device, Covidien, Mansfield, MA, USA). V-LocTM 90 was made of polyglycomer 631 (glycolide, dioxanone, and trimethylene carbonate) and swaged on a 26-mm half-circle taper-point needle. The first bite was placed from the cartilaginous surface of one end to the luminal surface of the other end. The needle end of the suture was then passed through the pre-formed loop end effector to fix the suture line. The rest was sutured at 180° in a normal continuous pattern, and intermittent tension was applied to the suture to allow the barbs to pass through the tissue and be anchored. At the final closure, two additional bites were taken beyond the terminal commissure to secure the end according to the manufacturer’s instructions. The free end of the suture was cut by applying a gentle pulling force.

Considering the differences according to suture patterns, both interrupted and continuous patterns were performed using the same smooth suture. Thus, for both the SI and SC groups, USP 4-0, PDS® plus antibacterial sutures (Ethicon Inc., Somerville, NJ, USA) were used. PDS® plus was made of polydioxanone and swaged on a 17-mm half-circle taper-point needle. Both groups were anastomosed according to general procedures, applying constant tension to the sutures during anastomosis to maintain the apposition of the trachea. All the knots were square knots with six throws each.

A single investigator measured and recorded the total suturing time in minutes from the moment the suture needle first passed through the tissue to the cutting of the remaining suture flush after the last knot or fixation procedure. Measurement was stopped when the sutures were replaced.

Mechanical testing

Mechanical tests were performed on all tracheal constructs within 24 h of tracheal collection. The specimens were mounted on a universal testing machine (Model 34SC-1; Instron, Norwood, MA, USA) equipped with a 1-kN load cell (Fig. 1). Appropriately sized aluminum rods were used as the jigs. Jigs were inserted at the proximal and distal ends of the specimens and secured with hose clamps (11,31). Constructs were preloaded with 2 N, and the elongation measurements were then zero-calibrated. The constructs were subsequently distracted in the axial direction at 0.5 mm/s until failure.

Figure 1.(A) Photograph of an anastomosed canine trachea model mounted on a universal testing machine (Instron; Model 34SC-1) before tensile testing. (B-D) Photographs of constructs representing each group, a barbed suture (B), smooth suture in a simple interrupted pattern (C), and smooth suture in a simple continuous pattern (D).

Load (Newtons, N) and displacement (mm) data were obtained using a universal software program (Bluehill 3; Instron, Norwood, MA, USA) at a frequency of 63 Hz. Load-displacement curves of the raw data were generated. Maximum tensile force was defined as the peak value achieved during each distraction. Failure was defined as a sudden decrease in the distraction force.

All mechanical tests were video recorded, and a single investigator confirmed the failure mode through video footage. The modes of failure were suture breakage, suture pulling, and tissue failure.

Statistical analysis

Data were tested for parametric distribution using the Shapiro–Wilk test of normality. Continuous variables with normal distribution are expressed as mean ± standard deviation. Differences in means between groups were assessed using one-way analysis of variance. Unequal variance was allowed when appropriate. When differences were found among the means, Tukey’s honestly significant difference post-hoc test was conducted to make pairwise comparisons between the group means. Fisher’s exact test was performed to determine whether an association existed between the suture method and the failure mode. SPSS software (IBM SPSS Statistics for Windows version 26.0; IBM Corp., Armonk, NY, USA) was used for all statistical analyses. Statistical significance was set at p < 0.05.

All twenty-seven tracheal segments from nine beagle dog cadavers were resected, anastomosed, and mechanically tested (Table 1). Nine tracheal fragments were included in each experimental group, among which the number of proximal, middle, and distal tracheal segments was equal to three.

Table 1 Brief description of study groups

BSISC
n999
Suture3-0 V-Loc 904-0 PDS plus4-0 PDS plus
Suture patternContinuousSimple interruptedSimple continuous

B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern.



We determined whether a difference existed in the mean diameter and length of the specimens between the groups (Table 2). The overall average diameter and length of the specimens were 17.41 ± 1.67 mm and 33.19 ± 3.25 mm, respectively, and no difference was found between the suture groups (p = 0.364 and p = 0.987, respectively).

Table 2 Mean diameter and length of specimens for three suture groups

GroupMeanp-value
Diameter (mm)B16.78 ± 1.990.364
SI17.89 ± 1.45
SC17.56 ± 1.51
Total17.41 ± 1.67
Length (mm)B33.11 ± 3.650.987
SI33.11 ± 3.09
SC33.33 ± 3.46
Total33.19 ± 3.25

B, barbed suture; SC, smooth suture in a continuous pattern; SI, smooth suture in an interrupted pattern.



Suturing time

The mean suturing times for each suture group were compared (Table 3). Closure time (3.29 ± 0.67 min) was faster in the B group than in the SI (8.99 ± 1.02 min, p < 0.001) and SC groups (4.41 ± 0.95 min, p < 0.05). The SI group required a longer suturing time than the SC group (p < 0.001).

Table 3 Mean suturing time for three suture groups

Suturing time (min)BSISC
Mean3.29 ± 0.678.99 ± 1.024.41 ± 0.95
Median3.114.108.20
Range2.45-4.47.16-10.253.41-6.1

There were statistical differences in suture time between B and SI (p < .05), B and SC (p < 0.001), and SC and SI (p < 0.001), respectively. B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern.



Maximum tensile force

The mean maximum tensile force was compared (Fig. 2). The constructs in the SC group sustained a higher maximum load (134.97 ± 27.88 N) than those in the SI (110.57 ± 17.87 N, p < 0.05) and B (103.10 ± 3.92 N, p < 0.01) constructs. No difference was found between the constructs in the B and SI groups (p = 0.05).

Figure 2.Box and Whisker plots of mean values and standard deviations for the maximum tensile force in the three suture groups (B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern). There was a statistically significant difference in the maximum tensile forces among the groups (p < 0.001). Boxes represent the interquartile range, horizontal lines in boxes represent the median, and whiskers extend to maximum and minimum values. **p < 0.01; *p < 0.05; NS, not significant (p = 0.05).

Mode of failure

The failure mode of tracheal constructs differed (p < 0.001) between the groups (Table 4). In the SC and SI groups, suture pull-through occurred in 66.6% (6/9) and 100% (9/9) of the constructs, respectively. For the rest of the constructs in the SC group, 33.3% (3/9) failed because of suture breakage. In the B group, 100% (9/9) of the constructs failed because of suture breakage.

Table 4 Mode of failure for three suture groups

Mode of failureBSISCMarginal row totals
Suture breakage90312
Suture pull-through09615
Marginal column totals99927

The Fisher’s exact test, p < 0.001.

B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern.


We compared barbed and smooth sutures for tracheal resection and anastomosis in a cadaveric canine model. The B group had a shorter suture time and similar tensile strength to the SI group. Compared with the SC group, the B group had fast closure time and the tension was weak. Therefore, the two hypotheses were accepted. This study is the first to demonstrate the feasibility of barbed sutures for canine tracheal resection and anastomosis.

In this study, the B group showed 2.7 times faster closure times than the SI group. Shortening the suturing time can lead to a reduction in surgery time. Reducing the operating time during tracheal resection and anastomosis is associated with economic savings and lower risk of anesthesia. Prolongation of anesthesia has been proven to affect the occurrence of complications during and after surgery (35). Therefore, surgical safety is expected to increase with the use of barbed sutures. In addition, we found that passing barbed sutures required less manipulation than tying knots with conventional sutures during the anastomosis. With vital structures such as carotid sheaths, tracheal surgery requires advanced techniques to create precise knots and preserve the blood supply (36). Therefore, the knotless nature of barbed sutures is expected to facilitate anastomosis in practical surgeries. In addition, the tensile forces of the B (mean, 103.1 N) and SI groups (110.57 N) in this study were similar, and were almost the same as the ultimate strength of tracheal constructs (102.5 N) anastomosed using 2-0 polypropylene in an interrupted pattern in a previous study (11). These findings corroborated that the strength of the barbed suture was comparable with that of the interrupted pattern in canine tracheal anastomosis and suggested that the barbed suture could be a potential alternative to the interrupted pattern of smooth sutures. However, future studies in clinical patients are needed to confirm these inferences.

Comparison of the suture times of the continuous patterns of barbed sutures and smooth sutures confirmed the advantage of barbed sutures in terms of suturing time. Thus, the surgical benefits described above are expected. By contrast, the SC group showed 1.3 times stronger tensile force than the barbed suture (B) group. In addition, the SC group endured a higher tensile force than the SI group. This finding is consistent with previous reports that the continuous pattern is more resistant to breakage than the interrupted pattern in tracheal anastomosis (3,5,11,16). However, a previous study on tracheal anastomosis in dogs demonstrated that the tensile force of the interrupted pattern, which is weaker than that of the continuous pattern, can be compensated for by adding a horizontal mattress suture (11). Although the axial load of the B group in this study was lower than that of the SC group, the barbed suture can be reinforced by adding a tension-relieving suture when a higher anastomotic strength is required because of extensive resection.

Based on the maximum tensile force of the barbed suture measured in this study, we evaluated the possibility of using barbed sutures for tracheal anastomosis in dogs. The upper limit of tracheal resection in dogs is known to be 25%-50% by length (24), and a recent study reported that normal tracheal tissue begins to rupture after 50% elongation. In terms of tensile force, this corresponds to approximately 23 N (42). In addition, a study based on anastomotic tension reported that successful surgical outcomes without complications can be expected at 1750-1800 gram force or less, that is, about 17.65 N or less (8,30). The maximum tensile force of the B group ranged from 96.1 to 109.0 N, exceeding all of the above reference forces. Therefore, we deduced that barbed sutures can provide sufficient mechanical strength for canine tracheal resection and anastomosis.

The mode of failure in our study was associated with the suture patterns. In this study, 100% of the B group and 33.3% of the SC group failed because of suture breakage. The results showed that the suture itself is the weakest part of the construct (12,38). However, 66.6% of the SC and 100% of the SI groups failed because of suture pull-through. These findings indicate that the suture itself is stronger than the holding capacity of the tracheal tissue (12,38). The strength of the suture was attributed to the material rather than the pattern. Therefore, the author speculated a higher probability of suture breakage in the B group than in the SI and SC groups because the strength of Glycomer613, a V-Loc 90 material, was weaker than that of polydioxanone, a PDS plus material (20). In addition, suture breakage occurred in all dogs in the B group, indicating that the strength of the barbed suture itself was a limiting factor in obtaining a high tensile strength (29). Therefore, using a barbed suture with a larger suture size or a sturdy material may achieve a higher tensile strength than our results in the B group. In the present study, no tissue failure was observed, whereas in previous studies, anastomosed tracheae commonly failed because of tissue failure (7,11). Tissue failure occurs when the final sutured structure is stronger than the tissue composition or adhesion forces (12,38). The authors surmise that the differences in failure modes result from the differences in anastomosis techniques. As the mechanical properties of the trachea mainly depend on the cartilage, the split cartilage technique is more resistant to failure than the annular ligament technique (43). The split cartilage technique places sutures around a segmented tracheal ring, whereas the annular ligament cartilage technique places sutures through the annular ligament. Thus, in the annular ligament cartilage technique, as in the previous study, the soft ligament can be torn by the suture, thereby easily resulting in tissue failure.

Although the criteria for an appropriate suture for tracheal anastomosis are ambiguous, selecting a suitable suture for the experiment was necessary. Barbed sutures made from monofilament absorbable materials with good handling properties and minimal tissue reactivity include Quill® and V-LocTM (28). V-Loc 90 barbed sutures were selected from among Quill barbed sutures made from polydioxanone, V-Loc 180 barbed sutures made from polyglycolic acid, and V-Loc 90 barbed sutures made from Glycomer 631. This is because V-Loc 90 with a 90-day absorption profile was the most appropriate, given that tracheal tissues heal for an average of 22 days (9). The size of the suture was determined according to the specimen size, with USP 3-0 V-Loc 90 being the most suitable. However, V-Loc 180 or Quill barbed sutures, which have longer absorption profiles, can be used if tension must be maintained for a longer period. Furthermore, a further study comparing the convenience of unidirectional and bidirectional barbed sutures is required. Smooth sutures were selected on a basis similar to barbed sutures. Among PDS made of polydioxanone and Maxon made of polyglycolic acid, PDS was selected as the representative of conventional smooth sutures because it is theoretically known to be better for tracheal anastomosis (32). According to the manufacturer, 4-0 PDS Plus (18.41 N) and 3-0 V-Loc 90 (17.36 N) had the smallest difference in suture strength; therefore, the USP 4-0 size was used for the PDS plus suture.

This study has several limitations. First, owing to the nature of the ex vivo cadaver design, implementing various clinical conditions, such as bleeding, securing the surgical field, and continuous tension applied to the trachea, was difficult and tissue response could not be evaluated using sutures. Second, we measured the mechanical strength of the trachea in normal dogs. Since tracheal resistance can be affected by age and disease state (6,24,30), prudent application of the study results is required. Third, although various forces act on the trachea according to the movement of the neck and respiration (1), we only evaluated the strength of the suture methods based on the axial tensile force. Additional mechanical tests are required for various resistances. Therefore, in relation to this study, we emphasize the need for further clinical studies targeting various patients and histopathological research on postoperative tracheal tissue response to barbed sutures.

In conclusion, the present study demonstrated the feasibility of barbed sutures in tracheal resection and anastomosis by confirming a faster suture time and adequate tensile strength compared with smooth sutures in an ex vivo canine model. Thus, we propose knotless barbed sutures as an effective alternative to the conventional smooth sutures for tracheal resection and anastomosis in dogs. This study highlights the need for additional clinical studies in dogs undergoing tracheal anastomosis. We expect the versatile use of barbed sutures in veterinary medicine.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2022R1F1A1071251).

Conceptualization: Min HA, Jeong SM; Data curation: Min HA; Formal analysis: Min HA, Jeong YJ; Funding acquisition: Jeong SM; Investigation: Min HA; Supervision: Jeong SM; Writing - original draft: Min HA, Moon CH; Writing - review & editing: Moon CH, Lee HB, Kim DH, Jeong SM.

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Article

Original Article

J Vet Clin 2022; 39(6): 311-318

Published online December 31, 2022 https://doi.org/10.17555/jvc.2022.39.6.311

Copyright © The Korean Society of Veterinary Clinics.

Cadaveric Feasibility Study of Knotless Barbed Suture for Tracheal Anastomosis in Dogs

Hyeon-Ah Min , Chang-Hwan Moon , You-Jeong Jeong , Hae-Beom Lee , Dae-Hyun Kim , Seong Mok Jeong

Department of Veterinary Surgery, College of Veterinary Medicine, Chungnam National University, Daejeon 34134, Korea

Correspondence to:*jsmok@cnu.ac.kr

Received: November 1, 2022; Revised: December 6, 2022; Accepted: December 8, 2022

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Appropriate suture technique is crucial for successful tracheal anastomosis. However, standards for an ideal suture method have not yet been established. A previous study suggested tracheal anastomosis using barbed sutures that do not require knots; however, their use in small animals has not been reported. In this study, we aimed to compare knotless barbed sutures with conventional smooth sutures in terms of maximum tensile strength and suturing time in canine tracheal models to demonstrate the feasibility of using barbed sutures in tracheal anastomosis in dogs. Tracheal segments harvested from nine beagle dog cadavers were randomly assigned to three suture groups: barbed suture (B), smooth suture in simple interrupted pattern (SI), and smooth suture in simple continuous pattern (SC). The maximum tensile force and suturing time were compared according to the suturing method, and the mode of failure was evaluated. The average suturing time was 3.29 min in the B group; 4.41 min, SC group; and 8.99 min, SI group (p < 0.001). The average maximum tensile force in the SC group was 134.97 N, which was stronger than the SI (110.57 N) and B groups (103.10 N) (p < 0.05 and p < 0.01, respectively). The difference between the B and SI groups was not significant (p = 0.05). The B group demonstrated comparable mechanical strength and shorter suture time compared with the SI group. Therefore, tracheal anastomosis using barbed sutures could be an effective alternative to conventional smooth sutures in dogs.

Keywords: barbed suture, dogs, suturing time, tensile force, tracheal anastomosis.

Introduction

Tracheal resection and anastomosis is a surgical procedure to remove a portion of the tracheal segments and then reconnect the ends (16,17). It is performed to correct various forms of tracheal stenosis, such as tracheal trauma, irreparable damage to tracheal portions, tracheal avulsion, and tracheal masses (2,15,16,39). Although some degree of luminal stenosis is inevitable after surgery, incorrect anastomosis and excessive strain at the anastomosis site are significant risk factors for the development of critical stenosis (2,10,16,22,23,36). Therefore, the suture technique to minimize anastomotic tension and achieve precise apposition is crucial for surgical success in tracheal resection and anastomosis.

Numerous studies have been conducted to select appropriate suture methods in small animals (3,11,15,22). Nevertheless, controversy remains over which suture materials and patterns are ideal for tracheal anastomosis (3,5,18,24). The continuous pattern has advantages in tension distribution and the interrupted pattern in tissue alignment and airtightness, and both suture patterns are applicable to tracheal anastomosis (3,5,10,14). Suture materials are typically determined by the operator’s preference because they are less important than suture patterns with regard to complications and prognosis in tracheal anastomosis (3,10,18). Although various sutures can be used for tracheal surgery, monofilament absorbable sutures are recommended because of the reported association between the use of multifilament nonabsorbable sutures and a high complication rate (18,32). However, the sutures must be strong enough to provide the mechanical support required for anastomosis (36).

Barbed sutures have small projections on their surface, providing an even tension distribution and suture anchor points (25,33). The presence of barbs obviates the need for knots and reduces pressure on the tissue over a larger contact area (26,31). Consequently, it overcomes the issues of overtightening knots and knot stimulations in traditional smooth sutures (19,21,34,41). Accordingly, the application of barbed sutures has been studied in various fields of veterinary medicine (13,19,27,37,40). Barbed sutures are expected to be effective in tracheal resection and anastomosis, where accurate alignment and proper tension distribution are closely associated with surgical prognosis (4,23,30,36). However, to the best of our knowledge, the application of barbed sutures in canine tracheas has not yet been reported. Although tracheal anastomosis using barbed sutures has been suggested in previous human medical research, differences exist in the patterns and threads between the compared sutures (7). In addition, because of the differences in the mechanical strength of the trachea between species (11), evaluation of the use of barbed sutures in dogs based on human studies is inappropriate.

This study aimed to compare knotless barbed sutures with conventional smooth sutures in terms of maximum tensile strength and suturing time of tracheal anastomosis on canine tracheas harvested from cadaveric dogs to demonstrate the feasibility of using knotless barbed sutures for canine tracheal resection and anastomosis. We hypothesized that barbed suture tracheal anastomosis would result in faster closure time and comparable tensile force than smooth suture tracheal anastomosis, and that the use of barbed suture would be feasible for canine tracheal resection and anastomosis.

Materials and Methods

Specimen preparation

We obtained nine adult beagle dog cadavers euthanized for reasons unrelated to this study. The dogs were confirmed to be healthy with no underlying medical conditions. The trachea from the cricoid cartilage to the carina was harvested within 2 h of euthanasia. The remaining soft tissue adherents were carefully removed while preserving the dorsal tracheal membrane. Each trachea was divided into thirds, and the length and diameter of each segment were measured. Tracheal segments were labeled, individually immersed in 0.9% NaCl solution, and refrigerated at 4°C before resection and anastomosis.

Tracheal resection and anastomosis

The three tracheal segments were equally distributed and randomly assigned to three suture groups according to the applied suture pattern. The three suture groups were the barbed suture (B), smooth suture in a simple interrupted pattern (SI), and smooth suture in a simple continuous pattern (SC). Each tracheal segment was excised and anastomosed using the split-cartilage technique. The middle tracheal ring of the segment was circumferentially split using a #11 blade. Sutures were placed around the divided tracheal ring, starting at one edge and exiting the other edge. Suture bites were taken uniformly at regular intervals of 3-5 mm. The dorsal membrane was sutured at the same level as the cartilage. A single surgeon conducted all the procedures with one assistant. During and after resection and anastomosis, all tracheal constructs were soaked and stored in 0.9% NaCl solution at 4°C until mechanical testing.

The B group was anastomosed using USP 3-0, unidirectional barbed V-LocTM 90 suture (V-LocTM Wound Closure Device, Covidien, Mansfield, MA, USA). V-LocTM 90 was made of polyglycomer 631 (glycolide, dioxanone, and trimethylene carbonate) and swaged on a 26-mm half-circle taper-point needle. The first bite was placed from the cartilaginous surface of one end to the luminal surface of the other end. The needle end of the suture was then passed through the pre-formed loop end effector to fix the suture line. The rest was sutured at 180° in a normal continuous pattern, and intermittent tension was applied to the suture to allow the barbs to pass through the tissue and be anchored. At the final closure, two additional bites were taken beyond the terminal commissure to secure the end according to the manufacturer’s instructions. The free end of the suture was cut by applying a gentle pulling force.

Considering the differences according to suture patterns, both interrupted and continuous patterns were performed using the same smooth suture. Thus, for both the SI and SC groups, USP 4-0, PDS® plus antibacterial sutures (Ethicon Inc., Somerville, NJ, USA) were used. PDS® plus was made of polydioxanone and swaged on a 17-mm half-circle taper-point needle. Both groups were anastomosed according to general procedures, applying constant tension to the sutures during anastomosis to maintain the apposition of the trachea. All the knots were square knots with six throws each.

A single investigator measured and recorded the total suturing time in minutes from the moment the suture needle first passed through the tissue to the cutting of the remaining suture flush after the last knot or fixation procedure. Measurement was stopped when the sutures were replaced.

Mechanical testing

Mechanical tests were performed on all tracheal constructs within 24 h of tracheal collection. The specimens were mounted on a universal testing machine (Model 34SC-1; Instron, Norwood, MA, USA) equipped with a 1-kN load cell (Fig. 1). Appropriately sized aluminum rods were used as the jigs. Jigs were inserted at the proximal and distal ends of the specimens and secured with hose clamps (11,31). Constructs were preloaded with 2 N, and the elongation measurements were then zero-calibrated. The constructs were subsequently distracted in the axial direction at 0.5 mm/s until failure.

Figure 1. (A) Photograph of an anastomosed canine trachea model mounted on a universal testing machine (Instron; Model 34SC-1) before tensile testing. (B-D) Photographs of constructs representing each group, a barbed suture (B), smooth suture in a simple interrupted pattern (C), and smooth suture in a simple continuous pattern (D).

Load (Newtons, N) and displacement (mm) data were obtained using a universal software program (Bluehill 3; Instron, Norwood, MA, USA) at a frequency of 63 Hz. Load-displacement curves of the raw data were generated. Maximum tensile force was defined as the peak value achieved during each distraction. Failure was defined as a sudden decrease in the distraction force.

All mechanical tests were video recorded, and a single investigator confirmed the failure mode through video footage. The modes of failure were suture breakage, suture pulling, and tissue failure.

Statistical analysis

Data were tested for parametric distribution using the Shapiro–Wilk test of normality. Continuous variables with normal distribution are expressed as mean ± standard deviation. Differences in means between groups were assessed using one-way analysis of variance. Unequal variance was allowed when appropriate. When differences were found among the means, Tukey’s honestly significant difference post-hoc test was conducted to make pairwise comparisons between the group means. Fisher’s exact test was performed to determine whether an association existed between the suture method and the failure mode. SPSS software (IBM SPSS Statistics for Windows version 26.0; IBM Corp., Armonk, NY, USA) was used for all statistical analyses. Statistical significance was set at p < 0.05.

Results

All twenty-seven tracheal segments from nine beagle dog cadavers were resected, anastomosed, and mechanically tested (Table 1). Nine tracheal fragments were included in each experimental group, among which the number of proximal, middle, and distal tracheal segments was equal to three.

Table 1 . Brief description of study groups.

BSISC
n999
Suture3-0 V-Loc 904-0 PDS plus4-0 PDS plus
Suture patternContinuousSimple interruptedSimple continuous

B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern..



We determined whether a difference existed in the mean diameter and length of the specimens between the groups (Table 2). The overall average diameter and length of the specimens were 17.41 ± 1.67 mm and 33.19 ± 3.25 mm, respectively, and no difference was found between the suture groups (p = 0.364 and p = 0.987, respectively).

Table 2 . Mean diameter and length of specimens for three suture groups.

GroupMeanp-value
Diameter (mm)B16.78 ± 1.990.364
SI17.89 ± 1.45
SC17.56 ± 1.51
Total17.41 ± 1.67
Length (mm)B33.11 ± 3.650.987
SI33.11 ± 3.09
SC33.33 ± 3.46
Total33.19 ± 3.25

B, barbed suture; SC, smooth suture in a continuous pattern; SI, smooth suture in an interrupted pattern..



Suturing time

The mean suturing times for each suture group were compared (Table 3). Closure time (3.29 ± 0.67 min) was faster in the B group than in the SI (8.99 ± 1.02 min, p < 0.001) and SC groups (4.41 ± 0.95 min, p < 0.05). The SI group required a longer suturing time than the SC group (p < 0.001).

Table 3 . Mean suturing time for three suture groups.

Suturing time (min)BSISC
Mean3.29 ± 0.678.99 ± 1.024.41 ± 0.95
Median3.114.108.20
Range2.45-4.47.16-10.253.41-6.1

There were statistical differences in suture time between B and SI (p < .05), B and SC (p < 0.001), and SC and SI (p < 0.001), respectively. B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern..



Maximum tensile force

The mean maximum tensile force was compared (Fig. 2). The constructs in the SC group sustained a higher maximum load (134.97 ± 27.88 N) than those in the SI (110.57 ± 17.87 N, p < 0.05) and B (103.10 ± 3.92 N, p < 0.01) constructs. No difference was found between the constructs in the B and SI groups (p = 0.05).

Figure 2. Box and Whisker plots of mean values and standard deviations for the maximum tensile force in the three suture groups (B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern). There was a statistically significant difference in the maximum tensile forces among the groups (p < 0.001). Boxes represent the interquartile range, horizontal lines in boxes represent the median, and whiskers extend to maximum and minimum values. **p < 0.01; *p < 0.05; NS, not significant (p = 0.05).

Mode of failure

The failure mode of tracheal constructs differed (p < 0.001) between the groups (Table 4). In the SC and SI groups, suture pull-through occurred in 66.6% (6/9) and 100% (9/9) of the constructs, respectively. For the rest of the constructs in the SC group, 33.3% (3/9) failed because of suture breakage. In the B group, 100% (9/9) of the constructs failed because of suture breakage.

Table 4 . Mode of failure for three suture groups.

Mode of failureBSISCMarginal row totals
Suture breakage90312
Suture pull-through09615
Marginal column totals99927

The Fisher’s exact test, p < 0.001..

B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern..


Discussion

We compared barbed and smooth sutures for tracheal resection and anastomosis in a cadaveric canine model. The B group had a shorter suture time and similar tensile strength to the SI group. Compared with the SC group, the B group had fast closure time and the tension was weak. Therefore, the two hypotheses were accepted. This study is the first to demonstrate the feasibility of barbed sutures for canine tracheal resection and anastomosis.

In this study, the B group showed 2.7 times faster closure times than the SI group. Shortening the suturing time can lead to a reduction in surgery time. Reducing the operating time during tracheal resection and anastomosis is associated with economic savings and lower risk of anesthesia. Prolongation of anesthesia has been proven to affect the occurrence of complications during and after surgery (35). Therefore, surgical safety is expected to increase with the use of barbed sutures. In addition, we found that passing barbed sutures required less manipulation than tying knots with conventional sutures during the anastomosis. With vital structures such as carotid sheaths, tracheal surgery requires advanced techniques to create precise knots and preserve the blood supply (36). Therefore, the knotless nature of barbed sutures is expected to facilitate anastomosis in practical surgeries. In addition, the tensile forces of the B (mean, 103.1 N) and SI groups (110.57 N) in this study were similar, and were almost the same as the ultimate strength of tracheal constructs (102.5 N) anastomosed using 2-0 polypropylene in an interrupted pattern in a previous study (11). These findings corroborated that the strength of the barbed suture was comparable with that of the interrupted pattern in canine tracheal anastomosis and suggested that the barbed suture could be a potential alternative to the interrupted pattern of smooth sutures. However, future studies in clinical patients are needed to confirm these inferences.

Comparison of the suture times of the continuous patterns of barbed sutures and smooth sutures confirmed the advantage of barbed sutures in terms of suturing time. Thus, the surgical benefits described above are expected. By contrast, the SC group showed 1.3 times stronger tensile force than the barbed suture (B) group. In addition, the SC group endured a higher tensile force than the SI group. This finding is consistent with previous reports that the continuous pattern is more resistant to breakage than the interrupted pattern in tracheal anastomosis (3,5,11,16). However, a previous study on tracheal anastomosis in dogs demonstrated that the tensile force of the interrupted pattern, which is weaker than that of the continuous pattern, can be compensated for by adding a horizontal mattress suture (11). Although the axial load of the B group in this study was lower than that of the SC group, the barbed suture can be reinforced by adding a tension-relieving suture when a higher anastomotic strength is required because of extensive resection.

Based on the maximum tensile force of the barbed suture measured in this study, we evaluated the possibility of using barbed sutures for tracheal anastomosis in dogs. The upper limit of tracheal resection in dogs is known to be 25%-50% by length (24), and a recent study reported that normal tracheal tissue begins to rupture after 50% elongation. In terms of tensile force, this corresponds to approximately 23 N (42). In addition, a study based on anastomotic tension reported that successful surgical outcomes without complications can be expected at 1750-1800 gram force or less, that is, about 17.65 N or less (8,30). The maximum tensile force of the B group ranged from 96.1 to 109.0 N, exceeding all of the above reference forces. Therefore, we deduced that barbed sutures can provide sufficient mechanical strength for canine tracheal resection and anastomosis.

The mode of failure in our study was associated with the suture patterns. In this study, 100% of the B group and 33.3% of the SC group failed because of suture breakage. The results showed that the suture itself is the weakest part of the construct (12,38). However, 66.6% of the SC and 100% of the SI groups failed because of suture pull-through. These findings indicate that the suture itself is stronger than the holding capacity of the tracheal tissue (12,38). The strength of the suture was attributed to the material rather than the pattern. Therefore, the author speculated a higher probability of suture breakage in the B group than in the SI and SC groups because the strength of Glycomer613, a V-Loc 90 material, was weaker than that of polydioxanone, a PDS plus material (20). In addition, suture breakage occurred in all dogs in the B group, indicating that the strength of the barbed suture itself was a limiting factor in obtaining a high tensile strength (29). Therefore, using a barbed suture with a larger suture size or a sturdy material may achieve a higher tensile strength than our results in the B group. In the present study, no tissue failure was observed, whereas in previous studies, anastomosed tracheae commonly failed because of tissue failure (7,11). Tissue failure occurs when the final sutured structure is stronger than the tissue composition or adhesion forces (12,38). The authors surmise that the differences in failure modes result from the differences in anastomosis techniques. As the mechanical properties of the trachea mainly depend on the cartilage, the split cartilage technique is more resistant to failure than the annular ligament technique (43). The split cartilage technique places sutures around a segmented tracheal ring, whereas the annular ligament cartilage technique places sutures through the annular ligament. Thus, in the annular ligament cartilage technique, as in the previous study, the soft ligament can be torn by the suture, thereby easily resulting in tissue failure.

Although the criteria for an appropriate suture for tracheal anastomosis are ambiguous, selecting a suitable suture for the experiment was necessary. Barbed sutures made from monofilament absorbable materials with good handling properties and minimal tissue reactivity include Quill® and V-LocTM (28). V-Loc 90 barbed sutures were selected from among Quill barbed sutures made from polydioxanone, V-Loc 180 barbed sutures made from polyglycolic acid, and V-Loc 90 barbed sutures made from Glycomer 631. This is because V-Loc 90 with a 90-day absorption profile was the most appropriate, given that tracheal tissues heal for an average of 22 days (9). The size of the suture was determined according to the specimen size, with USP 3-0 V-Loc 90 being the most suitable. However, V-Loc 180 or Quill barbed sutures, which have longer absorption profiles, can be used if tension must be maintained for a longer period. Furthermore, a further study comparing the convenience of unidirectional and bidirectional barbed sutures is required. Smooth sutures were selected on a basis similar to barbed sutures. Among PDS made of polydioxanone and Maxon made of polyglycolic acid, PDS was selected as the representative of conventional smooth sutures because it is theoretically known to be better for tracheal anastomosis (32). According to the manufacturer, 4-0 PDS Plus (18.41 N) and 3-0 V-Loc 90 (17.36 N) had the smallest difference in suture strength; therefore, the USP 4-0 size was used for the PDS plus suture.

This study has several limitations. First, owing to the nature of the ex vivo cadaver design, implementing various clinical conditions, such as bleeding, securing the surgical field, and continuous tension applied to the trachea, was difficult and tissue response could not be evaluated using sutures. Second, we measured the mechanical strength of the trachea in normal dogs. Since tracheal resistance can be affected by age and disease state (6,24,30), prudent application of the study results is required. Third, although various forces act on the trachea according to the movement of the neck and respiration (1), we only evaluated the strength of the suture methods based on the axial tensile force. Additional mechanical tests are required for various resistances. Therefore, in relation to this study, we emphasize the need for further clinical studies targeting various patients and histopathological research on postoperative tracheal tissue response to barbed sutures.

In conclusion, the present study demonstrated the feasibility of barbed sutures in tracheal resection and anastomosis by confirming a faster suture time and adequate tensile strength compared with smooth sutures in an ex vivo canine model. Thus, we propose knotless barbed sutures as an effective alternative to the conventional smooth sutures for tracheal resection and anastomosis in dogs. This study highlights the need for additional clinical studies in dogs undergoing tracheal anastomosis. We expect the versatile use of barbed sutures in veterinary medicine.

Source of Funding

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2022R1F1A1071251).

Conflicts of Interest

The authors have no conflicting interests.

Author Contributions

Conceptualization: Min HA, Jeong SM; Data curation: Min HA; Formal analysis: Min HA, Jeong YJ; Funding acquisition: Jeong SM; Investigation: Min HA; Supervision: Jeong SM; Writing - original draft: Min HA, Moon CH; Writing - review & editing: Moon CH, Lee HB, Kim DH, Jeong SM.

Fig 1.

Figure 1.(A) Photograph of an anastomosed canine trachea model mounted on a universal testing machine (Instron; Model 34SC-1) before tensile testing. (B-D) Photographs of constructs representing each group, a barbed suture (B), smooth suture in a simple interrupted pattern (C), and smooth suture in a simple continuous pattern (D).
Journal of Veterinary Clinics 2022; 39: 311-318https://doi.org/10.17555/jvc.2022.39.6.311

Fig 2.

Figure 2.Box and Whisker plots of mean values and standard deviations for the maximum tensile force in the three suture groups (B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern). There was a statistically significant difference in the maximum tensile forces among the groups (p < 0.001). Boxes represent the interquartile range, horizontal lines in boxes represent the median, and whiskers extend to maximum and minimum values. **p < 0.01; *p < 0.05; NS, not significant (p = 0.05).
Journal of Veterinary Clinics 2022; 39: 311-318https://doi.org/10.17555/jvc.2022.39.6.311

Table 1 Brief description of study groups

BSISC
n999
Suture3-0 V-Loc 904-0 PDS plus4-0 PDS plus
Suture patternContinuousSimple interruptedSimple continuous

B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern.


Table 2 Mean diameter and length of specimens for three suture groups

GroupMeanp-value
Diameter (mm)B16.78 ± 1.990.364
SI17.89 ± 1.45
SC17.56 ± 1.51
Total17.41 ± 1.67
Length (mm)B33.11 ± 3.650.987
SI33.11 ± 3.09
SC33.33 ± 3.46
Total33.19 ± 3.25

B, barbed suture; SC, smooth suture in a continuous pattern; SI, smooth suture in an interrupted pattern.


Table 3 Mean suturing time for three suture groups

Suturing time (min)BSISC
Mean3.29 ± 0.678.99 ± 1.024.41 ± 0.95
Median3.114.108.20
Range2.45-4.47.16-10.253.41-6.1

There were statistical differences in suture time between B and SI (p < .05), B and SC (p < 0.001), and SC and SI (p < 0.001), respectively. B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern.


Table 4 Mode of failure for three suture groups

Mode of failureBSISCMarginal row totals
Suture breakage90312
Suture pull-through09615
Marginal column totals99927

The Fisher’s exact test, p < 0.001.

B, barbed suture; SI, smooth suture in an interrupted pattern; SC, smooth suture in a continuous pattern.


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Vol.39 No.6 2022-12-31

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The Korean Society of Veterinary Clinics

pISSN 1598-298X
eISSN 2384-0749

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