An In Vitro Comparison of Two Suture Intervals Using Braided Absorbable Loop Suture in the Equine Linea Alba

Ultrasonographic evaluation of the width, thickness, and length of the normal linea alba in standing and dorsal recumbent horses

OBJECTIVE

To determine the variability in length, width, and thickness of the equine linea alba (LA) and the effect of a standing vs dorsal recumbent position on these measurements.

STUDY DESIGN

Descriptive anatomical comparative study.

ANIMALS

Standing horses (N = 75; in 30 horses, measurements were obtained in dorsal recumbency first and repeated after horses were standing).

METHODS

Linea alba length was measured in standing position from xiphoid to umbilicus, and transverse ultrasonographic images were obtained at five reference points to measure LA width and thickness. In 30 horses, measurements were obtained in dorsal recumbency first and repeated after horses were standing.

RESULTS

There was wide variation in LA width and thickness between standing horses, with gradual increase from xiphoid (range, 0.14-0.64 cm) to umbilicus (range, 0.2-2.97 cm). Linea alba length in standing position was 51.09 ± 6.219 cm. Width was independent of the size of the horse; thickness and length were correlated at some reference points to height (r = 0.346-585, P < .05) and weight (r = 0.324-0.642, P < .05). Different LA shapes could be identified. In dorsal recumbency, the LA was smaller in width at all reference points (15%-23%, P < .05) and shorter (20%, P < .001) compared with standing.

CONCLUSION

In addition to the wide variability in LA measurements and shapes between horses, there was a significant decrease in LA width and length when horses changed from standing to dorsal recumbency.

CLINICAL SIGNIFICANCE

The difference in LA length and width between dorsal recumbency and when standing could increase tension on sutures after laparotomy and should be taken into account when surgeons are closing the abdomen.

Tensile strength and early healing of self-locking and surgeon's knots

OBJECTIVE

To compare the biomechanical properties and healing of ventral midline celiotomies (VMC) closed with a self-locking knot combination and forwarder start and Aberdeen end (F-A) vs a traditional knot combination and surgeon's start and end (S-S).

STUDY DESIGN

In vivo, experimental.

ANIMALS

Twenty-one horses.

METHODS

Fourteen horses underwent VMC, which was closed with either an F-A (n = 7) or an S-S (n = 7) knot combination. Incisions were subjectively graded by masked evaluators for dehiscence, edema, and drainage. Biomechanical testing was performed on three abdominal segments, and histology was performed on one segment from each animal after humane euthanasia 10 days post-VMC. The abdominal wall of control horses (n = 7, no celiotomy) was collected for biomechanical testing.

RESULTS

Forwarder start and Aberdeen end and S-S horses had less tensile strength compared with control horses (P ≤ .001). No differences were detected between treatment groups for any variable evaluated, including tensile strength (P = .975), location of failure (P = .240), and histologic healing at the knot (P = .600).

CONCLUSION

Closure of VMC with self-locking knots resulted in biomechanical and healing features similar to those with a traditional closure technique, with neither restoring the tensile strength of the linea alba.

CLINICAL SIGNIFICANCE

Results of this study provide evidence to support a clinical trial to evaluate long-term performance of the F-A self-locking knot closure in horses.

Suture length to wound length ratio in 175 small animal abdominal midline closures

Experimental and human studies have reported the advantages of a suture length to wound length (SL:WL) ratio greater than 4:1 in midline abdominal closure. This is achieved when the tissue bite (TB) is equal to or larger than the stitch interval (SI). Although TB and SI values are recommended in some textbooks, SL:WL ratios are rarely reported in veterinary textbooks. Additionally, no clinical data regarding these parameters could be found in small animals. Therefore, the aim of this study was to evaluate the SL:WL ratio of midline laparotomy closure in dogs and cats performed by surgeons with different levels of expertise and to compare the findings with current textbook recommendations. Midline laparotomy incisions of 100 dogs and 75 cats were closed in continuous pattern by diplomates and residents of both the European College of Veterinary Surgeons (ECVS) and the European College of Animal Reproduction (ECAR). The mean SL:WL ratio was 2.5 ± 0.7:1. The surgeons´ level of experience and the species and body weights of the animals did not have any significant influence on the SL:WL ratio. A moderate negative correlation was observed between the mean SI to mean TB (SI:TB) ratio and the SL:WL ratio. In this study, the mean SI matched the textbook recommendations both in feline and canine species, whereas the TB in cats was different. In this study, the SL:WL ratio was less than 4:1 without apparent complications. Because of the low prevalence of incisional hernia in dogs and cats larger studies are necessary to evaluate clinical significance of the presented data.

Suture length to wound length ratio for simple continuous abdominal closures in veterinary surgery: An experimental in vitro study

Objective

This study aimed to investigate the suture length to wound length ratio (SL:WL) in an in vitro model of abdominal wall closure. Effects of the surgeon’s experience level on the SL:WL ratio were evaluated, hypothesizing that small animal surgeons do not spontaneously apply SL:WL ratios equal to or larger than 4:1.

Procedures

Three groups of surgeons with varying levels of experience performed 4 simple continuous sutures before (3 sutures) and after (1 suture) being educated on principles of the SL:WL ratio. All sutures were evaluated for their gaping, number of stitches, stitch intervals, tissue bite size and suture length.

Results

No significant differences in suture parameters or SL:WL ratios were found among the 3 groups, and 60.5% of control sutures and 77.0% of test sutures had SL:WL ratios above 4:1. There was a significant improvement in the mean ratio after the information was provided (p = 0.003). Overall, the SL:WL ratios ranged from 1.54:1 to 6.81:1, with 36.3% falling between 4:1 and 5:1 (5.17 mm mean stitch interval, 5.52 mm mean tissue bite size). A significant negative correlation was observed between the SL:WL ratio and the stitch interval to tissue bite ratio (r = -0.886). Forty-nine of 120 sutures fulfilled the current recommendations for abdominal wall closure with a mean SL:WL ratio of 4.1:1.

Conclusion

A SL:WL ratio larger than 4:1 was achieved in 60% of the control sutures and in 77% of test sutures. Additional animal studies are necessary to evaluate the SL/WL ratio in small animal surgery.

Bursting strength of surgeon's and self-locking knots for closure of ventral midline celiotomy in horses

OBJECTIVE

To compare the bursting strength and failure mode of ventral midline celiotomy closed with a simple continuous suture pattern with 1 of 2 knot combinations, a novel self-locking knot combination of a forwarder start with an Aberdeen end knot (F-A) and a traditional combination of a surgeon's start with a surgeon's end knot (S-S).

STUDY DESIGN

Ex vivo experimental.

SAMPLE POPULATION

Equine cadavers (n = 14).

METHODS

A 20-cm ventral midline celiotomy was created in 14 equine cadavers. Horses were assigned to celiotomy closure with an F-A or S-S knot combination. Prior to closure, a 200-L inflatable bladder was placed in the abdomen and then insufflated until failure of the celiotomy closure. The horses' signalment, weight, breed, and age, as well as knot combination type, mode of failure, closure time, and bursting strength (mm Hg) were recorded.

RESULTS

The median bursting strength was significantly greater when incisions were closed with the F-A knot combination (388 mm Hg) compared with the S-S knot combination (290 mm Hg) (P = .035). Most incisions failed along the fascia when closed with F-A combinations and at the knot when closed with S-S combinations.

CONCLUSION

The bursting strength of ventral midline incisions in equine cadavers was increased by an average of 25% when closed with the self-locking F-A knot combination.

CLINICAL SIGNIFICANCE

Closing ventral midline celiotomies with an F-A knot combination may provide a more secure closure than the traditional S-S knot combination. Additional in vivo investigation is required prior to recommending this closure in clinical cases.

Biomechanical properties of feline ventral abdominal wall and celiotomy closure techniques

Objective

To compare biomechanical properties and mechanism of failure of 3 regions of ventral abdominal wall in cats by using 2 suture materials, 2 suture bite‐to‐stitch intervals (SBSI), and full‐thickness versus fascia‐only closure.

Study Design

Randomized, cadaveric, ex vivo mechanical testing.

Sample Population

16 adult cat cadavers, 3 samples per cat.

Methods

Three regions of ventral abdominal wall were mechanically tested (N = 48 samples). Preumbilical, umbilical (U), and postumbilical (POU) regions were harvested by using a template. The thickness of the linea alba was recorded. Six samples without celiotomy served as controls. Twenty‐eight samples were randomized to SBSI (2 × 2 or 5 × 5 mm) and suture material (3‐0 polyglactin 910 or 3‐0 polydioxanone) for simple continuous celiotomy closure. Fourteen samples were randomized to full‐thickness or fascia‐only closure. Samples were tested by linear distraction; tensile strength and mechanism of failure were recorded. Effects of body weight, thickness of linea alba, anatomic region, SBSI, type of closure, and suture material were evaluated by mixed model linear analysis. Load to failure was compared between males and females, full‐thickness and fascia‐only closure by independent t test, with P < .05 considered statistically significant.

Results

The POU region achieved lower loads to failure. Load to failure was greater in males compared with females. No difference was detected between full‐thickness and fascia‐only closure. Failure most commonly occurred by tearing of suture through tissues. Tissue failure with suture line loosening occurred mainly in the 5 × 5‐mm SBSI group.

Conclusion

The POU region is biomechanically weak and may therefore be predisposed to incisional herniation.

Incisional complications following ventral median coeliotomy in horses. Does suturing of the peritoneum reduce the risk?

OBJECTIVE

Despite advances in surgical technique in abdominal surgery, incisional complications are frequently reported following ventral midline laparotomy in horses. The aim of this study was to determine the incidence of incisional complications at our clinic and to identify possible risk factors. Furthermore, we investigated whether suturing the peritoneum leads to a reduction of incisional complications.

MATERIAL AND METHODS

In this retrospective study, records of patients of the Large Animal Clinic for Surgery of the University of Leipzig from January 2010 to December 2015 were analysed. Horses with ventral midline laparotomy following colic were included in the study. Evaluated parameters comprised breed, sex, age of the horse, localisation of the colic disease, invasiveness of the surgical intervention, duration of general anaesthesia, suture pattern of the laparotomy wound and postoperative fever or leukopenia. Incisional complications included suture dehiscence, exudation from the wound and incisional hernia formation. Wound oedema formation was evaluated separately.

RESULTS

Incisional complications in the form of exudation and suture dehiscence occurred in 8.9% (18/202) of the horses. Postoperative hernia formation was observed in 5.2% (9/173) of patients. Breed, sex, localisation of the colic disease, invasiveness of the surgical intervention, duration of general anaesthesia and postoperative leukopenia did not influence the frequency of incisional complications. An increased risk of incisional complications was found in horses aged 20 years and older (odds ratio [OR] 17.90), in animals with postoperative fever (OR 7.48) and in horses with unsutured peritoneum (OR 7.68). Furthermore, patients with moderate and severe wound oedema displayed a significantly increased risk for the development of incisional complications.

CONCLUSION AND CLINICAL RELEVANCE

Suture pattern is the only risk factor that can be directly influenced by the surgeon. Because a peritoneal suture is associated with a decreased risk of incisional complications, it should be standard practice when closing a laparotomy wound in the horse.

The effect of six knotting methods on the biomechanical properties of three large diameter absorbable suture materials

OBJECTIVE

To evaluate the effect of 6 different knotting methods on the mechanical properties of 3 large absorbable suture materials used in large animal surgery.

STUDY DESIGN

In vitro mechanical study. Sample Population- Knotted suture loops (n=15 per group).

METHODS

Suture loops were created between two low-friction pulleys with either 2 polydioxanone, 2 polyglactin 910 or 3 polyglactin 910. Strands were tied using 1 of 6 knotting technique: square knot, surgeon knot, clamped surgeon's knot, sliding half-hitch knot (HH), Delimar knot and self-locking knot (SLK). A single cycle to failure test was performed on each suture loop with a distraction rate of 100 mm/min. Failure modes were evaluated and breaking strength, elongation to failure and stiffness were compared.

RESULTS

All loops except two HH failed at the knot by acute breaking. The double-stranded SLK was both stronger and stiffer than all other knots for each suture material. Clamping the first throw of the surgeon knot decreased load to failure significantly (143.11 +/- 8.64 N) compared with not clamping (159.21 +/- 6.14 N) for polydioxanone. Stiffness and elongation to failure were respectively lower and increased for 2 polydioxanone compared with both polyglactin 910 materials for all knotting techniques.

CONCLUSIONS

Knotting techniques do influence structural properties of suture loops. The double strand loop conferred stiffer and stronger properties to the SLK CLINICAL RELEVANCE: Clamping the first throw of polydioxanone should be avoided when tying a suture under tension even using large diameter suture materials. Using a SLK might be considered as a useful alternative when excessive tension is present.