The development of mechanical strength of surgically anastomosed arteries sutured with Dexon

Absorbable Suture in Vascular Surgery

The choice of suture material in surgery is often individual and a result of personal experience. Cardiovascular surgeons have always been reluctant to use absorbable suture material for direct arterial or venous anastomoses for differ ent reasons, mainly because of suspected anastomotic dilatation or even rupture during or after the absorption phase. More than ten years ago, a new class of synthetic, monofilament, flexible, biodegradable suture material was intro duced for clinical use. Since then, much experimental and clinical work has been carried out to evaluate physical and biological characteristics of this class of suture material (polydioxanone/polydimethylsiloxane = [PDS] and polytri methylene-carbonate = [PTMC]) in many different tissues, including vascular tissue. There is increasing evidence that slow-absorbable sutures will gain clini cal importance for cardiovascular and peripheral vascular surgery in the fu ture, since many experimental and clinical studies during the last forty years have proven histologic superiority over nonabsorbable materials. Descriptions of healing processes in blood vessels after surgical anastomoses lead to the con clusion that persisting foreign suture material results in persistent cellular reac tions and chronic inflammatory responses and may consequently disturb physi ologic functions such as compliance at the anastomotic site. It is the purpose of this article to give a review of the literature. Implications are discussed for surgery of growing vessels, transplantation surgery, microsurgery, and surgery in infected anastomoses. Nonabsorbable suture material should no longer be used for direct vascular anastomoses.

Dynamic behavior of suture-anastomosed arteries and implications to vascular surgery operations

BACKGROUND

Routine vascular surgery operations involve stitching of disconnected human arteries with themselves or with artificial grafts (arterial anastomosis). This study aims to extend current knowledge and provide better-substantiated understanding of the mechanics of end-to-end anastomosis through the development of an analytical model governing the dynamic behavior of the anastomotic region of two initially separated arteries.

METHODS

The formulation accounts for the arterial axial-circumferential deformation coupling and suture-artery interaction. The proposed model captures the effects of the most important parameters, including the geometric and mechanical properties of artery and sutures, number of sutures, loading characteristics, longitudinal residual stresses, and suture pre-tensioning.

RESULTS

Closed-form expressions are derived for the system response in terms of arterial radial displacement, anastomotic gap, suture tensile force, and embedding stress due to suture-artery contact interaction. Explicit objective functionalities are established to prevent failure at the anastomotic interface.

CONCLUSIONS

The mathematical formulation reveals useful interrelations among the problem parameters, thus making the proposed model a valuable tool for the optimal selection of materials and improved functionality of the sutures. By virtue of their generality and directness of application, the findings of this study can ultimately form the basis for the development of vascular anastomosis guidelines pertaining to the prevention of post-surgery implications.

Compliance mismatch may promote graft-artery intimal hyperplasia by altering suture-line stresses

The role of graft-artery compliance mismatch in the development of distal anastomotic intimal hyperplasia (DAIH) is not yet resolved. Although DAIH develops at all surgically created anastomoses, increased compliance mismatch does not lead to greater hyperplasia formation in end-to-end anastomoses, but in end-to-side anastomoses, it leads to a profound increase in hyperplasia. The current study was undertaken to determine whether suture-induced anastomotic stresses could explain these findings. A large strain finite element analysis of vascular wall mechanics was performed to compare the influence of compliance mismatch on intramural stresses in end-to-end versus end-to-side anastomoses. A novel modelling approach was implemented which includes suture-induced stress concentrations. End-to-end and end-to-side graft-artery simulations were executed using (1) artery (compliance = C = 0.44% kPa(-1)), (2) vein (C = 0.33% kPa(-1)), and (3) Dacron (C = 0.14% kPa(-1)) grafts. Residual stresses due to axial tension were included and the anastomoses were statically inflated to 13.3 kPa (100 mmHg). Elevated intramural stresses were found to exist at both the end-to-end and end-to-side graft-artery junctions; however, in the end-to-end anastomosis, the maximum anastomotic stress was not a function of the graft compliance, whereas in the end-to-side anastomosis, the maximum stress was a strong function of graft compliance. For the 45 degree end-to-side geometry considered in this study, the maximum anastomotic stress concentration obtained using a stiff Dacron graft was more than 40% greater than that obtained using a compliant artery graft. In the end-to-end anastomosis, the Dacron graft led to a less than 5% increase in maximum stress over the artery graft. Therefore, increased compliance mismatch increases stresses and promotes DAIH in end-to-side junctions, but, it has little influence on either stresses or DAIH in end-to-end junctions. Thus, the proliferative influence of increased compliance mismatch on suture-line hyperplasia in end-to-side anastomoses can be explained by the resulting increase in intramural stresses. In addition, since high stresses were found in both geometries, elevated suture-line intramural stresses may be an important proliferative stimulus for intimal hyperplasia formation in all vascular reconstructions.

Vascular anastomoses with absorbable suture material: an experimental study

A synthetic, monofilament, absorbable suture material, polytrimethylene carbonate, was tested to determine its suitability for use in arterial anastomoses. The material studied is a copolymer made of trimethylene carbonate and polyglycolic acid, with a retention time in the tissue of up to six months. In an experimental group of 12 mongrel dogs, using simple end-to-end anastomoses, aortic and femoral patch grafts of bovine heterograft material and iliofemoral bypass implants of 5 mm of expanded polytetrafluoroethylene prostheses were performed and arteriographically and histologically documented. Direct intraindividual comparisons were made with the absorbable (polytrimethylene carbonate) and nonabsorbable (polypropylene, expanded polytetrafluoroethylene suture) materials, a total of 108 anastomoses. No suture material-related complications such as ruptures or suture line aneurysms occurred. Polytrimethylene carbonate sutures led to less inflammation and scar tissue formation than polypropylene sutures. Complete absorption of the suture material by hydrolytic decomposition was followed by an almost complete regeneration in all layers of the vessel wall. Regeneration of the connective tissue structures of the media was noted. Initial associated reactions in the intima eventually disappeared. Both suture materials were equivalent histologically in the early months of the study, but after 10 month follow-up differences were observed, especially in the structure of the media, apart from the fact that polytrimethylene carbonate is absorbed completely after four to seven months.

Efficacy of Dexon microsutures in rat major abdominal vessel anastomosis. I: Application to heterotopic heart transplant

A total of 52 syngeneic heterotopic heart transplants were performed using 9-0 Dexon microsutures to see if these anastomoses could be tolerable when challenged by the burden of transplanted heart and lung. Eighteen long-term surviving transplants were verified by reliable ECG, Doppler tracings, and direct palpation of the heart grafts. Animals sacrificed at monthly intervals beginning 3 to 6 months posttransplantation were free of thrombus, lung abscesses, and separation at the anastomoses. Even though foreign body reaction was still present up to 5 months posttransplantation, no actual sutures were present after 3 months. From these observations, Dexon microsuture is acceptable in organ transplantation procedures.