Comparison of incisional bursting strength of 2-strand continuous crossing and simple continuous patterns for closure of the equine linea alba

Abstract

The objective of this study was to assess and compare the bursting pressure and mode of failure of a 2-strand continuous crossing suture pattern and a simple continuous suture pattern for closure of the equine linea alba. No difference in bursting strength or mode of failure was found between the 2 suture patterns.

The simple continuous pattern is commonly used for closure of the equine linea alba (1,2), because of its speed of closure and even distribution of forces in the tissues compared with interrupted suture patterns (3). Closure under tension with a simple continuous pattern can be challenging, often requiring the suture material to be manipulated and tightened multiple times to achieve and maintain tissue apposition, potentially weakening the suture and causing more trauma to the tissues (4,5). A 2-strand continuous crossing suture pattern (continuous crossing) (Figure 1) was first described by White (6) and used in such cases to overcome tension and provide firm apposition with minimal tissue movement. The biomechanical properties of this pattern and its ability to resist forces placed upon an incision have not been evaluated.

Figure 1.

Continuous crossing pattern.

The objective of this study was to further assess and compare the bursting strength and mode of failure between these 2 continuous patterns for closure of the equine linea alba using a previously described ex-vivo model (1). We hypothesized that there would be no difference in bursting strength or mode of failure between the 2-strand continuous crossing pattern and a simple continuous pattern.

Sixteen horses that were euthanized for reasons unrelated to this study were randomly assigned to 2 experimental groups (simple continuous or continuous crossing group). Horses included in the study were older than 3 y of age, weighed between 300 kg and 600 kg, and had a grossly normal ventral midline. Of the 16 horses, 5 were geldings and 11 were mares. The horses consisted of 7 Quarter Horses, 3 Thoroughbreds, 2 Saddlebreds, 2 Arabians, 1 Trakehner, and 1 Appaloosa. The median age was 18 y (range: 8 to 30 y). The mean ± standard deviation (SD) body weight was 487 kg (± 67 kg). The Washington State University Institutional Animal Care and Use Committee approved all procedures.

Immediately following euthanasia, the animals were positioned in dorsal recumbency. The anus and vagina were sutured closed to prevent prolapse of internal organs. A 40-cm skin incision was made on the ventral midline. The subcutaneous tissues were dissected from the linea alba and external fascia of the rectus abdominis muscle for better exposure. Using a #10 scalpel blade, a 25-cm incision was made through the linea alba, starting at the umbilicus and extending cranially. A 200-L polyurethane bladder (New World Manufacturing, Cloverdale, California, USA) was inserted in the abdominal cavity and positioned flat against the ventral body wall. Ingress and egress tubing exited through stab incisions placed between the 14th and 15th ribs on either side of the abdomen. The ingress tubing was connected to a flow meter (MMA-26 flow meter; Dwyer Instruments, Michigan City, Indiana, USA) and an air compressor (Air Mate; EMGLO Compressors, Baltimore, Maryland, USA) for insufflation of the bag. The egress tubing was connected to a pressure transducer (PX 209; Omega Technologies, Stamford, Connecticut, USA) and a digital panel meter (DP-25 S; Omega Technologies) for pressure recording. Celiotomies were closed with USP 3 Polyglactin 910 (Vicryl; Ethicon, Johnson and Johnson, Summerville, New Jersey, USA) using 1 of the 2 suture patterns. Tissue bites were standardized, by use of a plastic template, to 15 mm from the edge of the incision and 15 mm apart. Eight celiotomies were closed with a simple continuous pattern and eight with a “2-strand continuous crossing” pattern (Figure 1). For the simple continuous pattern, 2 surgeons started at opposite ends of the incision and the 2 separate suture strands were tied to each other in the middle of the incision. The cranial and caudal knots were placed 10 mm cranial or caudal to the celiotomy, respectively. For the continuous crossing pattern 2 surgeons, standing on opposite sides of the horse, started on the caudal end of the incision and took alternating bites (Figure 1). The first suture line started 10 mm caudal to the incision and the second line started 15 mm from the first. Both lines were tied to each other at the end, 10 mm past the cranial end of the incision. The skin was not apposed to allow direct visualization of the body wall and suture at the point of failure during testing.

One camera, recording at 240 frames per second, at a resolution of 840 × 480 (Drift Ghost S; Drift Innovation LTD, London, United Kingdom) was placed directly above the incision to document mode of failure and another camera (Canon HFS100; Canon, Tokyo, Japan) recorded the digital meter. After closure of the incision, the polyurethane bladder was inflated at a rate of 40 L/min until failure occurred. Bursting strength was determined as the maximum pressure (mmHg) recorded before a sudden decrease in pressure.

Failure mode (suture or abdominal wall) was determined for each incision after evaluation of slow motion video with direct visualization of the incision site. Suture failure was defined as suture breaking adjacent to the knot or away from the knot before abdominal wall failure. Abdominal wall failure was defined as intact suture loops tearing through the fascia or when the body wall failed lateral to the incision.

A Mann-Whitney U-test was used to compare the bursting pressures between groups. The significance level was set at P < 0.05. R version 3.1.1 was used for the statistical analysis. Median (range) bursting pressure for the continuous crossing pattern was 343.871 mmHg (range: 268.892 to 429.193 mmHg), and for the simple continuous pattern was 318.016 mmHg (range: 258.55 to 408.509 mmHg). There was no significant difference between bursting pressures when comparing suture patterns (P = 0.4). The predominant mode of failure was local fascial failure. Eleven out of sixteen horses (69%) failed at the fascia and only 2 horses in the simple continuous group, and 3 horses in the continuous crossing group had failure of the suture (Table 1).

Table 1.

Median (range) of bursting strength and mode of failure for each group.

	Simple continuous	Continuous crossing
Bursting pressure (mmHg)	316.01	343.87
(range)	(258.55 to 408.51)	(268.89 to 429.19)
Failure of wall (total)	6	5
Adjacent to celiotomy	5	4
Remote from celiotomy	1	1
Failure of suture (total)	2	3
Total number of horses	8	8

The strength of a closure depends not only on the suture material used, but also on suture pattern and intrinsic strength of the tissue, among other variables (7,8). The results of this study indicated that when using 3 Vicryl for closure of normal linea alba incisions, the strength of the closure was comparable between a simple continuous pattern and a continuous crossing pattern, as shown by their similar median bursting strengths. As described by White (6), the continuous crossing pattern has some important potential advantages over a simple continuous pattern when closing midline celiotomies under tension. The 2-strand continuous crossing pattern allows the surgeon to maintain apposition of the tissue edges by holding tension on 1 suture line, while the next tissue bite is placed with the second suture line. By alternating suture bites, the sutures interlace and lock each previous bite in position preventing slippage, thus minimizing the need for additional suture manipulation. Repetitive suture manipulation can weaken suture material, cause more trauma to tissues, and even cut through the surgeon’s gloves, breaking sterility (4).

The suture material selected for closure should be as strong as the tissue it is placed through (9). Previous studies utilizing 3 Vicryl on the equine linea alba, have concluded that this suture material is not as strong as the equine abdominal fascia as failure of the construct (suture/tissue) occurred most frequently at the suture level (1,10,11). The results of the present study differ from these earlier studies, as fascial failure occurred more often than suture failure. The ex-vivo model used in this study, unlike the model used by Trostle et al (11) and Fierheller and Wilson (10), more closely reproduces 3-dimensional forces placed upon the incision/suture construct, which may explain the difference in results. Since failure of the incision at maximal pressure was a very rapid event, evaluation in slow motion video allowed differentiation of primary body wall failure with secondary suture failure, from primary suture failure. In cases of primary body wall failure, it was noticed that when the initial failure occurred at the fascia, the polyurethane bladder forcefully exited the abdomen and resulted in subsequent suture breakage. This finding may help explain the difference between the present results and the ones from Magee and Gallupo (1), in which slow motion video was not available.

Normal abdominal body walls were used in this study, hence further work would be needed to determine the strength of this pattern in abnormal walls, such as cases of incisional hernias. A limitation of this study results from the use of cadavers, which limited the ability to evaluate the properties of the suture patterns when used for closure under excessive tension. In addition, the pattern strength was determined based on a single cycle to failure, immediately after suturing. This mimics what happens on acute dehiscence, such as when recovering from anesthesia, but does not necessarily represent delayed suture failures that are more likely due to repeated cycling of the suture material and incision.

In conclusion, this study reports the biomechanical properties, bursting strength, and mode of failure, of a 2-strand continuous crossing pattern, previously described by White (6), in comparison to the simple continuous pattern for closure of the linea alba in horses. The results demonstrate that, under the tested conditions, the continuous crossing pattern can be used without compromising the strength of the closure. Further biomechanical and clinical studies are necessary before fully considering the suitability of the 2-strand continuous crossing pattern to replace a simple continuous pattern in situations of excessive tension.