Methods of fabricating stents with enhanced fracture toughness

Abstract

Stents and methods of manufacturing a stents with enhanced fracture toughness are disclosed.

1 . (canceled) 
     
     
         2 . A method of treating a blood vessel with a biodegradable stent comprising
 deploying a biodegradable stent in a blood vessel from a crimped diameter to an intended deployment diameter, the biodegradable stent including a cylindrically-shaped scaffold extending longitudinally from a proximal end to a distal end, the scaffold comprising a poly(L-lactide)-based biodegradable polymer,   wherein the scaffold includes a pattern comprising a first cylindrical ring of struts adjacent to a second cylindrical ring of struts,   wherein the first cylindrical ring of struts includes first bending elements with curved portions having apices and the second cylindrical ring of struts includes second bending elements with curved portions having apices,   wherein apices pointing to a proximal end of the scaffold of the first bending elements are longitudinally aligned with the apices pointing to the distal end of the scaffold of the second bending elements,   wherein longitudinal linking struts connect the first cylindrical ring with the second cylindrical ring, the scaffold formed by cutting the pattern in a tube,   wherein the curved portions bend outward when the scaffold is deployed to allow for radial expansion of the scaffold,   wherein no cracks form in the curved portions of the first and second bending elements when the stent is deployed to the intended deployment diameter.   
     
     
         3 . The method of  claim 2 , wherein the tube has been processed to increase crystallinity prior to cutting, the biodegradable polymer after the processing has a crystallinity of less than 50%. 
     
     
         4 . The method of  claim 3 , wherein the biodegradable polymer after the processing has a crystallinity less than 40%. 
     
     
         5 . The method of  claim 2 , wherein curved portions of the bending elements have no cracks at the crimped diameter, 
     
     
         6 . The method of  claim 2 , wherein the bending elements have an angle greater than 90° at a diameter the pattern is cut, and wherein the scaffold has adequate radial strength to hold open the blood vessel. 
     
     
         7 . The method of  claim 3 , wherein the processing comprises radially expanding the tube to an expanded diameter prior to forming the pattern in the tube at the expanded diameter, the radial expansion providing induced molecular orientation in the circumferential direction in the scaffold. 
     
     
         8 . The method of  claim 2 , wherein the scaffold has induced molecular orientation in the circumferential direction. 
     
     
         9 . The method of  claim 3 , wherein the processing comprises heating the tube to a temperature above a glass transition temperature (Tg) of the biodegradable polymer. 
     
     
         10 . The method of  claim 2 , wherein the bending elements have an angle greater than 110° at the diameter the pattern is cut.