Abstract
Microvascular surgery is becoming a prevalent surgical practice. Replantation, hand reconstruction, orthopedic, and free tissue transfer procedures all rely on microvascular surgery for the repair of venous and arterial defects at the millimeter and submillimeter levels. Often, a vascular graft is required for the procedure as a means to bridge the gap between native arteries. While autologous vessels are desired for their bioactivity and non-thrombogenicity, the tedious harvest process, lack of availability, and caliber or mechanical mismatch contribute to graft failure. Thus, there is a need for an off-the-shelf artificial vascular graft that has low thrombogenic properties and mechanical properties matching those of submillimeter vessels. Poly(vinyl alcohol) hydrogel (PVA) has excellent prospects as a vascular graft due to its bioinertness, low thrombogenicity, high water content, and tunable mechanical properties. Here, we fabricated PVA grafts with submillimeter diameter and mechanical properties that closely approximated those of the rabbit femoral artery. In vitro platelet adhesion and microparticle release assay verified the low thrombogenicity of PVA. A stringent proof-of-concept in vivo test was performed by implanting PVA grafts in rabbit femoral artery with multilevel arterial occlusion. Laser Doppler measurements indicated the improved perfusion of the distal limb after implantation with PVA grafts. Moreover, ultrasound Doppler and angiography verified that the submillimeter diameter PVA vascular grafts remained patent for 2 weeks without the aid of anticoagulant or antithrombotics. Endothelial cells were observed in the luminal surface of one patent PVA graft. The advantageous non-thrombogenic and tunable mechanical properties of PVA that are retained even in the submillimeter diameter dimensions support the application of this biomaterial for vascular replacement in microvascular surgery.
Highlights
Microvascular surgery contributes widely to various surgical procedures, such as replantation and free tissue transfer (Griffin and Thornton, 2005), free flap surgery (Shen et al, 1988), orthopedic surgeries (Doi et al, 1977; Judet et al, 1981), and digital reconstruction (Lanzetta, 1995)
The problems of expanded polytetrafluoroethylene (ePTFE) grafts are further magnified in the submillimeter scale, where the low shear stress and flow, and high risk of blood stasis can lead to rapid graft thrombosis and failure (Barnes, 1980; Sarkar et al, 2006). ePTFE grafts with 1 mm diameter have all failed after implantation in vivo, showing rapid and extensive thrombosis within a few days of implantation (Lidman et al, 1980; Ganske et al, 1982; Harris and Seikaly, 2002)
The internal diameter (ID) and wall thickness between Poly(vinyl alcohol) hydrogel (PVA) grafts cross-linked at different temperatures but with similar ID showed minute differences
Summary
Microvascular surgery contributes widely to various surgical procedures, such as replantation and free tissue transfer (Griffin and Thornton, 2005), free flap surgery (Shen et al, 1988), orthopedic surgeries (Doi et al, 1977; Judet et al, 1981), and digital reconstruction (Lanzetta, 1995). During these procedures, vascular grafts are required to anastomose blood vessels together, repair vascular defects, and restore blood flow. The development of a new type of off-the-shelf synthetic vascular graft with submillimeter diameter for microvascular surgery is needed
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