Tensile characteristics of PTFE sutures

Does Knot Configuration Improve Tensile Characteristics of Monofilament Suture Materials?

PURPOSE

The effects of knot configuration used in surgical procedures are often overlooked when surgeons are looking for an ideal suture material. This study aimed to investigate the mechanical properties of monofilament suture materials used in oral and maxillofacial surgery under diverse knot configurations.

MATERIALS AND METHODS

A custom-made experimental platform and a microtensile test device were used to evaluate the mechanical properties of the tested subjects. There were 2 predictor variables: suture material and knot configuration. Three types of nonabsorbable and monofilament suture materials with 4-0 gauge, including nylon, polypropylene, and polytetrafluoroethylene, were tested. Four different knot configurations-a surgeon's knot square plus a square knot (2 = 1 = 1), a surgeon's knot granny plus a square knot (2 × 1 = 1), a reverse surgeon's knot granny plus a square knot (1 × 2 = 1), and a reverse surgeon's knot square plus a square knot (1 = 2 = 1)-were also used with each of the suture materials. The tensile strength (N) and elongation (μm) of each sample were measured as the outcomes. The data were statistically analyzed using 2-way analysis of variance and Tukey's honestly significant difference tests. The significance level was set at P < .05.

RESULTS

Overall, 120 samples were tested. Statistical analysis revealed that the highest tensile strength (28.6 N) was found for nylon in the surgeon's knot square plus a square knot (P < .05). Polypropylene showed a similar high tensile strength value (24.7 N) in the reverse surgeon's knot granny plus a square knot (P > .05). Polytetrafluoroethylene demonstrated significantly lower values for both tensile strength in tested configurations (within the range of 5.2-8.5 N). Under diverse configurations, polypropylene suture samples offered the most stable tensile strength and elongation.

CONCLUSIONS

The present study demonstrated that different knot configurations might improve the mechanical profile of commonly used monofilament suture materials. The surgeon's knot square (2 = 1), commonly used by surgeons worldwide, proved to be the most beneficial knot configuration in this study in terms of tensile strength and elongation. Further research on optimal knot configuration may be just as important as seeking an ideal suture material.

Biomechanical characteristics of different methods of neo-chordal fixation to the papillary muscles

BACKGROUND AND AIM OF THE STUDY

Several techniques have been described for neo-chordal fixation to the papillary muscles without any reported clinical differences. The objective of this study is to compare in vitro the biomechanical properties of four of these common techniques.

METHODS

We studied the biomechanical properties of expanded polytetrafluoroethylene neo-chordal fixation using four techniques: nonknotted simple stitch, nonknotted figure-of-eight stitch, knotted pledgeted mattress stitch, and knotted pledgeted stitch using commercially available prefabricated loops. Neo-chordae were submitted to a total of 20 traction-relaxation cycles with incremental loads of 1, 2, and 4 N. We calculated the elongation, the force-strain curve, elasticity, and the maximum tolerated load before neo-chordal failure.

RESULTS

The elongation of the neo-chordae was lowest in the simple stitch followed by the figure-of-eight, the pledgeted mattress, and he commercially prefabricated loops (p < .001). Conversely, the elastic modulus was highest in the simple stitch followed by the figure-of-eight, the pledgeted mattress, and the prefabricated loops (p < .001). The maximum tolerated load was similar with the simple stitch (28.87 N) and with the figure-of-eight stitch (31.39 N) but was significantly lower with the pledgeted mattress stitch (20.51 N) and with the prefabricated loops (7.78 N).

CONCLUSION

In vitro, neo-chordal fixation by nonknotted simple or nonknotted figure-of-eight stitches resulted in less compliance as opposed to the use of knotted pledgeted stitches. Fixation technique seemed to influence neo-chordal biomechanical properties, however, it did not seem to affect the strength of the suture when subjected to loads within physiological ranges.

Artificial chordae for mitral valve repair

BACKGROUND

Mitral valve repair using expanded polytetrafluoroethylene sutures to replace mitral chordae tendineae is a well-established procedure. However, the incidence of neo-chordae failure causing recurrent mitral regurgitation is not well defined.

METHODS

We have reviewed the reported cases of complications after mitral valve repair related to the use of neo-chordae. This study was mainly carried out through PubMed, Medline, and Google Chrome websites.

RESULTS

We have identified a total of 26 patients presenting with rupture of polytetrafluoroethylene neo-chordae, mostly being described as isolated cases. Few other cases of recurrent mitral regurgitation with hemolysis were found, where reoperation was not caused by neo-chordal failure but most likely by technical errors. At pathological investigation the findings were substantially similar in all reported cases. The neo-chordae retained their length and pliability, became covered with host tissue and rupture was mainly related to suture size. Mild calcification was observed not interfering with chordal function; chordal infection did never occur.

CONCLUSIONS

The use of artificial neo-chordae provides excellent late results with durable mitral valve repair stability. Chordal rupture may occur late postoperatively leading to reoperation because of recurrent mitral regurgitation. Despite its rarity, this potential complication should not be overlooked during follow-up of patients after mitral valve repair using artificial neo-chordae.

Evaluation of Bacterial Colonization and Clinical Properties of Different Suture Materials in Dentoalveoler Surgery

PURPOSE

This study aimed to compare the effects of 10 different suture materials commonly used in dentoalveolar surgery on wound healing, their postoperative microbial colonization, and related clinical parameters.

METHODS

A total of 172 suture samples from patients who had undergone extraction of impacted third molars were included in the study. The suture materials studied were poly-glycolide-colactide, fast absorbable poly-glycolide-colactide, poly-glycolic acid-cocaprolactone, polydioxanone, silk, polypropylene, polyvinylidene difluoride, polyamide, polyester, and polytetrafluoroethylene (PTFE). The microbial colonization in all sutures and clinical parameters were evaluated after 1 week.

RESULTS

Multifilament sutures had higher bacterial colonization compared with monofilament sutures (P < .001). No dental plaque accumulation was observed in any samples of polypropylene sutures. Polydioxanone, PTFE, and poly-glycolic acid-cocaprolactone sutures exhibited less postoperative slack compared with all other sutures after 1 week. Patients with silk, polyvinylidene difluoride, and PTFE sutures had less suture-related discomfort. According to the Landry index score, monofilament sutures demonstrated superior wound healing to multifilament sutures (P = .019). In addition, nonabsorbable sutures showed significantly better wound epithelization than absorbable sutures (P ˂ .001).

CONCLUSIONS

Bacterial colonization and tissue reactions due to the surface properties of the suture affected the wound healing after dentoalveolar surgery. Multifilament sutures should not be applied for prolonged periods because of their tendency for microbial colonization. The tissue reaction to the absorbable suture materials may adversely affect wound healing.

Predictors of failure of mitral valve repair using artificial chordae

BACKGROUND

We investigate predictors of failure of mitral valve repair (MVr) using expanded polytetrafluoroethylene (ePTFE) and durability of them in the long-term period in single institution.

METHODS

Four hundred twenty-one consecutive patients with primary mitral valve disease underwent MVr using artificial chordae (group A: n=304) and suture repair (group S: n=117) at our institution from January 2002 to April 2020. A comparison study was performed to examine the long-term outcomes, re-operation rate and risk factors for re-operation.

RESULTS

One hospital death and 5 late deaths occurred in group S, and 20 late deaths occurred in group A. The re-operation rates were similar [group A; n=8 (2.6%), group S; n=6 (5%)]. The major cause of re-operation was ruptured ePTFE (CV-4: n=1, CV-5: n=6) in group A, and suture rupture in group S. Re-operation was performed after a median period of 88 months for ruptured ePTFE, and 26 months for group S. The rate of ePTFE rupture was 1.8% with CV5 and 0.2% with CV4. Risk factors for re-operation included post-operative arrhythmia, urgent operation, no annular-ring, ruptured ePTFE and suture rupture. The rates of freedom from re-operation and actuarial mitral valve survival rates at 5, 10, and 15 years were 99%, 95%, and 93% and 96%, 91%, and 89%, respectively, in group A, and 96%, 91%, and 91% and95%, 94%, and 94% in group S.

CONCLUSIONS

The long-term surgical outcomes of MVr using both techniques were feasible. Over the long-term, the ePTFE rupture rate of CV-5 was higher than that of CV-4.

Comparison between tensile characteristics of various suture materials with two suture techniques: an in vitro study

OBJECTIVE

The first objective of the present study was to evaluate the tensile strength and elongation to failure of commonly used suture materials in oral surgery. As a secondary objective, it was aimed to make a comparison between two different suture techniques within the same suture materials.

MATERIALS AND METHODS

Eight different suture materials with 3-0 gauge (silk, polytetrafluoroethylene, polypropylene, polyester, polyglactin 910, polyglycolic acid, poliglecaprone 25, polydioxanone) underwent tensile testing for maximum load of failure and elongation rate. All strands were tied by one investigator on the experimental platform using the surgeon's knot plus additional square knots in both simple suture and horizontal mattress suture techniques. Prepared specimens were examined using a microtensile testing device before (baseline) and after 3, 7, and 14 days' immersion in artificial saliva.

RESULTS

Statistical analysis of the current study revealed that the tensile strength for polyglycolic acid, polyglactin 910, polypropylene, and silk sutures was significantly lower at day 3 than at the baseline. By day 14, polyglycolic acid and polyglactin 910 showed a significant reduction in tensile strength for both techniques. While polydioxanone obtained the highest tensile strength and elongation values in both techniques, polytetrafluoroethylene showed the most stable tensile strength even with the lowest value. Tensile strength in simple suture techniques was almost twice than that of horizontal mattress suture technique for each specimen.

CONCLUSIONS

Polyglycolic acid and polyglactin 910 were considerably sensitive to immersion time. Polydioxanone demonstrated optimum performance during each immersion period among the tested materials, whereas polytetrafluoroethylene was the most stable.

CLINICAL RELEVANCE

The selection of the most proper suture material remains challenging for clinicians. The present study provides relevant information for clinicians to guide them in their choice of the suitable material. In this context, clinicians can benefit from the use of polydioxanone for its high tensile strength regardless of the suture technique used, whereas polytetrafluoroethylene shows a long-term stability. The strength and stability differences among suture materials and techniques need to be considered before making an informed decision.

Simple Extracorporeal Knot-Tying Technique in Minimal Access Surgery

Extracorporeal knot tying is one of the challenges in minimally invasive surgery. The current aids are often associated with mechanical failures and application difficulties, a long learning curve, fraying of sutures, user errors, increased cost, and reduced haptic feedback. We describe a technique that is very conventional and uses a polytetrafluoroethylene pledget to lower the knot. Also, there is no contact between the suture and the instrument at any point, and therefore fraying and tearing of sutures is not an issue. The technique is simple and inexpensive and has an extremely short learning curve.

Rupture of GORE-TEX neochordae 10 years after mitral valve repair

The current non-resectional paradigm in mitral valve (MV) repair emphasizes the use of polytetrafluoroethylene (PTFE) for artificial chordal replacement. While excellent long-term durability of repair using PTFE neochordae has been established, there have been rare reports of neochordal rupture at various times after surgery. We report a case of artificial chordal rupture 10 years after anterior mitral leaflet repair, necessitating reoperation. This complication may have been precipitated by maldistributed intracardiac tensile forces as a consequence of a malpositioned annuloplasty band.

Physical and Mechanical Evaluation of Five Suture Materials on Three Knot Configurations: An in Vitro Study

The aim of this study was to evaluate and compare the mechanical properties of five suture materials on three knot configurations when subjected to different physical conditions. Five 5-0 (silk, polyamide 6/66, polyglycolic acid, glycolide-e-caprolactone copolymer, polytetrafluoroethylene) suture materials were used. Ten samples per group of each material were used. Three knot configurations were compared A.2=1=1 (forward⁻forward⁻reverse), B.2=1=1 (forward⁻reverse⁻forward), C.1=2=1 (forward⁻forward⁻reverse). Mechanical properties (failure load, elongation, knot slippage/breakage) were measured using a universal testing machine. Samples were immersed in three different pH concentrations (4,7,9) at room temperature for 7 and 14 days. For the thermal cycle process, sutures were immersed in two water tanks at different temperatures (5 and 55 °C). Elongation and failure load were directly dependent on the suture material. Polyglycolic acid followed by glycolide-e-caprolactone copolymer showed the most knot failure load, while polytetrafluoroethylene showed the lowest (P < 0.001). Physical conditions had no effect on knot failure load (P = 0.494). Statistically significant differences were observed between knot configurations (P = 0.008). Additionally, individual assessment of suture material showed statistically significant results for combinations of particular knot configurations. Physical conditions, such as pH concentration and thermal cycle process, have no influence on suture mechanical properties. However, knot failure load depends on the suture material and knot configuration used. Consequently, specific suturing protocols might be recommended to obtain higher results of knot security.

Intermediate and early rupture of expanded polytetrafluoroethylene neochordae after mitral valve repair

Neochordae construction using an expanded polytetrafluoroethylene suture is an accepted surgical technique to correct mitral regurgitation due to mitral valve prolapse. We report two cases of intermediate and early rupture of CV-5 expanded polytetrafluoroethylene neochordae after mitral valve repair. As a result of these cases, we now use CV-3 expanded polytetrafluoroethylene for neochordae construction with no failures.

Biomechanical performance of new vascular sutures and needles for use in polytetrafluoroethylene grafts

Two new cardiovascular monofilament sutures attached to taper point needles have been developed for use in expanded polytetrafluoroethylene (PTFE) grafts. One monofilament suture made of PTFE has a microporous structure that allows it to be channel swaged to a needle that closely approximates its suture diameter. The other suture is a monofilament polypropylene suture that has been extruded to produce a tapered swage end, which was significantly smaller than that of the remainder of the suture in order to be channel swaged to smaller diameter needles. On the basis of comprehensive biomechanical performances, the performance of the new needle suture products with needle/suture diameter ratios approaching 1:1 was superior to needle suture products with 2:1 needle/suture diameter ratios for use in PTFE vascular grafts, regardless of the suture material.

The influence of surface morphology and wettability on the inflammatory response against poly(L-lactic acid): a semi-quantitative study with monoclonal antibodies

In this study, the influence of surface morphology and wettability of both degradable and nondegradable polymer films on the inflammatory response after subcutaneous implantation in the rat was investigated. Degradable non-porous, porous, and "combi" (porous with a nonporous layer on one side) poly(L-lactic acid) (PLLA) films and nondegradable polytetrafluoroethylene (PTFE) and (porous) expanded PTFE (e-PTFE) were used. Contact angles measurements indicate that PLLA is more hydrophillic than PTFE. Assessment of the inflammatory response was performed after various periods of implantation (up till 180 days), with both conventional light microscopy and immunohistochemistry using monoclonal antibodies (mAbs). The inflammatory response observed initially can largely be considered as part of the wound healing reaction, and up till day 40 the inflammatory response against PLLA was minimally more intense than against PTFE (porous as well as nonporous). From day 40 on, the PLLA films provoke a more intense inflammatory response as compared to the PTFE films. Both porous PLLA and the porous side of the "combi" PLLA film provoke a more intense inflammatory response than nonporous PLLA and the nonporous side of the "combi" PLLA film, respectively. In general, PTFE and e-PTFE films provoke an inflammatory response which is minimally more intense than the one provoked by the sham operation. Almost no ingrowth of tissue was observed in the porous e-PTFE films. In contrast, there was abundant tissue ingrowth in and an inflammatory response against porous PLLA. It can be concluded that biodegradable PLLA films provoke a more intense inflammatory response than nondegradable PTFE films. Also, porosity enhances the inflammatory response. However, porosity enhances the inflammatory response only when the wettability of a biomaterial permits cellular ingrowth.