Creep behavior of commonly used suture materials in abdominal wall surgery

Developing and validating an implantable suture tension sensor

Introduction

Suture tension has a direct influence on the sutured tissue. For abdominal wall closure, suture tension should be optimal without causing tissue necrosis, which can result in surgical site infection or incisional hernia. The purpose of the present study is to evaluate a device that can measure suture tension in-situ and in real-time.

Materials and methods

A cheap, commercially available analog-to-digital converter was used, in conjunction with a force sensing resistor. A sensor probe housing was designed and 3D-printed. In order to test the sensor, a mechanical, computer controlled human abdominal wall model called the AbdoMAN was used.

Results

An implantable suture tension sensor was developed, keeping cost-effectiveness in mind. This sensor can translate tension in the suture into a downward force, applied to the force sensing resistor. The sensor's raw readout was characterized using a set of weights, from which a formula correlating the readout to a specific force, was derived. Preliminary validation was successfully performed using the AbdoMANmodel, which showed a progressive rise in suture tension when the intra-abdominal pressure was artificially increased over time.

Conclusion

The implantable suture tension sensor appeared to be capable of recording real time changes in suture tension, and the. validation process of this sensor has been initiated. With the information from devices like this, a much better understanding of the issues at play in the development of incisional hernia can be gained.

Electrospun Medical Sutures for Wound Healing: A Review

With the increasing demand for wound healing around the world, the level of medical equipment is also increasing, but sutures are still the preferred medical equipment for medical personnel to solve wound closures. Compared with the traditional sutures, the nanofiber sutures produced by combining the preparation technology of drug-eluting sutures have greatly improved both mechanical properties and biological properties. Electrospinning technology has attracted more attention as one of the most convenient and simple methods for preparing functional nanofibers and the related sutures. This review firstly discusses the structural classification of sutures and the performance analysis affecting the manufacture and use of sutures, followed by the discussion and classification of electrospinning technology, and then summarizes the relevant research on absorbable and non-absorbable sutures. Finally, several common polymers and biologically active substances used in creating sutures are concluded, the related applications of sutures are discussed, and the future prospects of electrospinning sutures are suggested.

The effect of different suturing materials for abdominal fascia wound closure on the collagen I/III expression ratio in rats

Background

Incisional hernia is a frequent complication of abdominal wall incision and has a high rate of recurrence. Most of the studies stated that non-absorbable sutures decreased incisional hernia incidences, but some stated otherwise. We aimed to compare the collagen type I/III ratio between monofilament non-absorbable sutures and multifilament absorbable sutures for abdominal fascia closure in Wistar albino rats.

Methods

Forty rats were divided into four groups. Groups 1 and 3 were sutured with monofilament non-absorbable (polyvinylidene fluoride). Groups 2 and 4 were sutured with multifilament absorbable (polyglycolide). Then, groups 1 and 2 were euthanized on day 4 (POD 4), while groups 3 and 4 were euthanized on day 7 (POD 7). Samples of fascia (1 × 0.5 cm) were taken for analysis. Collagen I/III ratios were measured using immunohistochemistry staining methods.

Results

While the expression of collagen I was not significantly different between monofilament non-absorbable and multifilament absorbable at POD 4 and 7 (p = 0.45 and 0.81, respectively), the expression of collagen III reached a significant level with p-values of 0.0003 and 0.0004 for POD 4 and 7, respectively. Moreover, the collagen I/III ratio was also significantly different between the two groups either at POD 4 (0.88 ± 0.23 vs. 0.53 ± 0.08; p = 0.0003) and 7 (1.77 ± 0.65 vs. 1.03 ± 0.28; p = 0.004).

Conclusions

Monofilament non-absorbable sutures show a significantly higher collagen I/III ratio than multifilament absorbable sutures for abdominal fascia closure in rats. Our findings imply that the usage of monofilament non-absorbable sutures might have a beneficial effect on decreasing the incisional hernia occurrence.

•

One of the most important factors that influences the occurrence of incisional hernia is suturing material.

•

Collagen is a major component of the extracellular matrix and plays an important role in maintaining tissue elasticity and tensility.

•

The usage of monofilament non-absorbable sutures might have a beneficial effect on decreasing the incisional hernia occurrence.

Evaluation of a new suture material (Duramesh™) by measuring suture tension in small and large bites techniques for laparotomy closure in a porcine model

PURPOSE

After closure of laparotomies, sutures may pull through tissue due to too high intra-abdominal pressure or suture tension, resulting in burst abdomen and incisional hernia. The objective of this study was to measure the suture tension in small and large bites with a new suture material.

METHODS

Closure of the linea alba was performed with small bites (i.e., 5 mm between two consecutive stitches and 5 mm distance from the incision) and large bites (i.e., 10 mm × 10 mm) with Duramesh™ size 0 (2 mm) and PDS II 2-0 in 24 experiments on six porcine abdominal walls. The abdominal wall was fixated on an artificial computer-controlled insufflatable abdomen, known as the 'AbdoMan'. A custom-made suture tension sensor was placed in the middle of the incision.

RESULTS

The suture tension was significantly lower with the small bites technique and Duramesh™ when compared with large bites (small bites 0.12 N (IQR 0.07-0.19) vs. large bites 0.57 N (IQR 0.23-0.92), p  < 0.025). This significant difference was also found in favour of the small bites with PDS II 2-0 (p  < 0.038). No macroscopic tissue failure was seen during or after the experiments.

CONCLUSION

Closure of the abdominal wall with the small bites technique and Duramesh^™ was more efficient in dividing suture tension across the incision when compared to large bites. However, suture tension compared to a conventional suture material was not significantly different, contradicting an advantage of the new suture material in the prevention of burst abdomen and incisional hernia during the acute, postoperative phase.

New suture materials for midline laparotomy closure: an experimental study

Background

Midline laparotomy closure carries a significant risk of incisional hernia. This study examines the behavior of two new suture materials, an elastic material, polyurethane (PUe), and a barbed polydioxanone (PDXb) suture thread in a rabbit model of midline incision closure.

Methods

Three 2-cm midline incisions were made in 68 New Zealand White rabbits. The incisions were closed by running suture using four 3/0 threads: polypropylene (PP) (Surgipro®, Covidien), PUe (Assuplus®, Assut Europe), PDX (Assufil®, Assut Europe) or PDXb (Filbloc®, Assut Europe). Animals in each suture group were euthanized 3 weeks and 6 months after surgery. Histological sections of the tissue-embedded sutures were subjected to morphological, collagen expression, macrophage response and uniaxial tensiometry studies.

Results

No signs of wound dehiscence or complications were observed. At 3 weeks, all sutures were surrounded by connective tissue composed mainly of collagen III. PUe showed greater collagen I expression than the other sutures. All sutures elicited a macrophage response that diminished from 3 weeks to 6 months (p < 0.001). This response was similar for the non-reabsorbable sutures (PP and PUe) yet PDXb showed a significantly greater response than the other reabsorbable suture (PDX) at 3 weeks (p < 0.01). At this early time point, the tensile strength of PUe was similar to that of control intact tissue (p > 0.05).

Conclusion

Three weeks after surgery, PUe revealed more collagen I deposition than the remaining materials and this translated to a similar biomechanical behavior to linea alba, that could avoid the appearance of short term dehiscences and thus reduce the incidence of incisional hernia. PDXb provides no additional advantages in their behavior regarding PDX suture.

Knot integrity as a function of suture expiration

OBJECTIVE

To test the integrity of knots tied with expired suture and non-expired suture, using 5 different suture materials.

STUDY DESIGN

Knots were tied using expired and non-expired chromic catgut, polyglactin 910, polydioxanone, silk, or coated polyester. Expired sutures were a mean of 10.5 years past the date of expiration stamped on the packaging. Suture packaging was inspected for any flaws or humidity. There were 116 knots with expired suture and 109 non-expired knots. All knots were tied by hand. Suture was soaked in 0.9% sodium chloride for 60 seconds and subsequently transferred to a tensiometer where the tails of the knots were cut to 3 mm length. We compared the tensile strength of knots using a tensiometer to pull the knots until the suture broke or untied. A minimum of 30 knots were needed in order to detect a statistically significant main effect for expired and non-expired sutures with 80% power and a 5% chance of type I error.

RESULTS

A total of 225 knots were tied. Overall, we found no difference in mean tension between expired suture (77.5 ± 31.7 N) and non-expired suture at failure (81.9 ± 30.2 N). All the sutures broke at the knot and none untied. Expired chromic and polydioxanone were significantly weaker than the non-expired suture of the same material (p = 0.002 and p = 0.001, respectively). There was no statistically significant difference in tensile strength between expired absorbable or permanent suture materials. Based on a univariate analysis of variance ([SCAP]ANOVA)[R] there was no difference in the tension at failure between expired and non-expired sutures with suture packet as a covariate. No suture untied when knotted with expired suture.

CONCLUSIONS

Under laboratory conditions, expired chromic and polydioxanone sutures broke at lower tensile strength than non-expired sutures of the same material.

Tensile strength of a surgeon's or a square knot

OBJECTIVE

To test the integrity of surgeon's knots and flat square knots using 4 different suture materials.

STUDY DESIGN

Chromic catgut, polyglactin 910, silk, and polydioxanone sutures were tied in the 2 types of knot configurations. For all sutures, a 0-gauge United States Pharmacopeia suture was used. Knots were tied by a single investigator (J.B.). The suture was soaked in 0.9% sodium chloride for 60 s and subsequently transferred to a tensiometer where the tails were cut to 3-mm length. We compared the knots, measuring knot strength with a tensiometer until the sutures broke or untied.

RESULTS

A total of 119 throws were tied. We found no difference in mean tension at failure between a surgeon's knot (79.7 N) and a flat square knot (82.9 N). Using a chi(2) test, we did not find a statistically significant difference in the likelihood of knots coming untied between surgeon's knots (29%) and flat square knots (38%).

CONCLUSIONS

Under laboratory conditions, surgeon's knots and flat square knots did not differ in tension at failure or in likelihood of untying.

Suture end length as a function of knot integrity

OBJECTIVE

To evaluate tension at the failure of 3 commonly used sutures when suture ends were cut to 3 lengths.

STUDY DESIGN

Knots were tied using U.S. Pharmacopeia Size 0-0 polyglactin 910, silk, or polydioxanone sutures. The knots were tied randomly on a jig by the same surgeon. End lengths were then cut to random lengths of 0, 3, and 10 mm. We compared the individual knot strength when subjected to tensile forces via tensiometer with the point of knot failure, which was defined as untying and/or breaking of the knot.

RESULTS

Three types of suture were divided into 3 groups based on end lengths for a total of 178 knots. A logistic regression analysis showed the odds of knots coming untied were highest for polyglactin 910 (odds ratio [OR] = 33.7; 95% confidence interval [CI] = 4.1-277.1). End length also had a significant effect on knots untying, with the 0-mm knots being more likely to come untied (OR, 21.2; 95% CI, 2.9-153.0). Post hoc tests for a 3 x 3 analysis of variance found that silk knots failed at significantly lower tension than polydioxanone (p < 0.001) and polyglactin 910 (p < 0.001) knots.

CONCLUSIONS

The knots with an end length of 0 mm were significantly more likely to come untied than either 3- or 10-mm knots. Among all the materials, polyglactin 910 was the most prone to untying; however, it resulted in untying at a mean tension greater than the breaking point of silk.

Primary mesh augmentation with fibrin glue for abdominal wall closure--investigations on a biomechanical model

BACKGROUND

The occurrence of incisional hernias after various types of abdominal procedures and incisions continues to be a problem. A number of studies conducted for diverse risk groups have identified a beneficial role for the prophylactic use of mesh augmentation. To what extent this affects the stability of a suture was tested in our biomechanical model.

MATERIALS AND METHODS

To that effect, we compared three groups, carrying out six measurements in each case: (1) single suture in a muscle specimen, (2) suture and additional reinforcement with fibrin glue, and (3) suture and additional reinforcement with a mesh fixed with fibrin glue (Tissucol, Tisseel; with an overlap of 2 cm to all sides).

RESULTS

The single suture conferred a tensile strength, which in our model, was just above the prescribed maximum abdominal pressure of 32 N (37.3 N). The additional use of fibrin glue did not have any significant impact on this result (41.8 N). Only through mesh augmentation with fibrin glue was it possible to achieve a significantly greater tensile strength (64.5 N, p = 0.003).

CONCLUSIONS

The prophylactic use of meshes for stabilization of laparotomy closures appears to be effective. Adequate mesh fixation can be achieved with fibrin glue alone. Further experimental studies and in particular randomized clinical trials are needed to demonstrate proof of the long-term advantages of mesh augmentation in risk groups.