Self-expanding metal mesh stent

Recent technological advances in the last two decades have led to the development of self-expanding or expandable metallic mesh stents. These stents represent the latest technology for the treatment of malignant and benign airway obstructions. A stent can be described as a tubular prosthesis that maintains luminal patency and a predefined luminal diameter of a tubular structure by opposing radial forces to extrinsic or intramural compressive forces. Thus, a stent provides internal support for luminal patency. 

The use of PHA coatings to enhance biocompatibility of vascular stents was shown to be an effective modification. Self-expanding nitinol mesh vascular stents were coated with PHA and PHA loaded with an antiproliferative drug. Stents were placed in the femoral artery of dogs and examined for 120 days. The analysis of the state of the vessels and morphometric examination showed the effectiveness of coating vascular stents with PHA, especially PHA loaded with an antiproliferative drug. Reactive changes in the vessel wall were less pronounced and no complications occurred that are usually caused by implantation of uncoated metal stents (Protopopov et al. 2005, 2008). 

There are now various expandable meshed metallic stents used in the ureter such as Wallstents (Schneider, Minneapolis, Minn.), Palmaz-Schatz (Johnson and Johnson Interventional Systems, Warren, N.J.) and Ultraflex (Boston Scientific, Boston, Mass.) stents. The Wallstent consists of multiple stainless steel filaments (0.14 mm in caliber), woven in a crisscross pattern to form a tubular mesh that self-expands to a predetermined diameter and length. The stent is compliant and flexible it moulds to the lumen of the ureter but leaves more than 75% of its surface free of metal. Expandable metal stents have received widespread recognition in the treatment of a variety of occlusive diseases, particularly in the arterial and biliary systems. The advantages over plastic polymers are their larger luminal diameter, the ease of placement, the ability to limit the length of the area the stent covers so that it closely... 

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