Osteosynthetic shape memory material intramedullary bone stent and method for treating a bone fracture using the same

Abstract

A method for providing stabilization and compression of a bone fracture, the method comprising: providing an intramedullary prosthesis sized for insertion into the intramedullary canal of a bone and having a distal end, a proximal end and a porous structure therebetween, wherein (i) in a first state, the prosthesis is longitudinally expanded and radially contracted, and (ii) in a second state, the prosthesis is longitudinally contracted and radially expanded, conforms to the shape of the adjacent bone and exerts forces on the adjacent bone; and positioning the intramedullary prosthesis within the intramedullary canal of a bone so that the intramedullary prosthesis spans the bone fracture, whereby to provide stabilization and compression of the bone fracture.

What is claimed is: 
     
         1 . A method for providing stabilization and compression of a bone fracture, the method comprising:
 providing an intramedullary prosthesis sized for insertion into the intramedullary canal of a bone and having a distal end, a proximal end and a porous structure therebetween, wherein (i) in a first state, the prosthesis is longitudinally expanded and radially contracted, and (ii) in a second state, the prosthesis is longitudinally contracted and radially expanded, conforms to the shape of the adjacent bone and exerts forces on the adjacent bone; and   positioning the intramedullary prosthesis within the intramedullary canal of a bone so that the intramedullary prosthesis spans the bone fracture, whereby to provide stabilization and compression of the bone fracture.   
     
     
         2 . A method according to  claim 1  wherein the intramedullary prosthesis is inserted into the intramedullary canal of a bone while in its first state. 
     
     
         3 . A method according to  claim 2  wherein, after the intramedullary prosthesis has been inserted into the intramedullary canal of a bone, the intramedullary prosthesis is transformed from its first state to its second state. 
     
     
         4 . A method according to  claim 3  wherein the intramedullary prosthesis is transformed from its first state to its second state via superelasticity. 
     
     
         5 . A method according to  claim 3  wherein the intramedullary prosthesis is transformed from its first state to its second state via temperature transition. 
     
     
         6 . A method according to  claim 3  wherein the intramedullary prosthesis is transformed from its first state to its second state via an expanding balloon. 
     
     
         7 . A method according to  claim 1  wherein the intramedullary prosthesis is self-expanding. 
     
     
         8 . A method according to  claim 7  wherein the intramedullary prosthesis comprises a shape memory alloy. 
     
     
         9 . A method according to  claim 8  wherein the shape memory alloy comprises Nitinol. 
     
     
         10 . A method according to  claim 1  wherein, when the intramedullary prosthesis is in its second state, the intramedullary prosthesis applies hoop stress radially to the surrounding bone and applies compressive force longitudinally to the surrounding bone so as to close the gap across the fracture line. 
     
     
         11 . A method according to  claim 10  wherein the hoop stress is generated by the radial expansion of the intramedullary prosthesis and the compressive force is generated by the foreshortening of the intramedullary prosthesis. 
     
     
         12 . A method according to  claim 1  wherein the intramedullary prosthesis has a modulus of elasticity which is similar to that of bone. 
     
     
         13 . A method according to  claim 1  wherein the intramedullary prosthesis has a modulus of elasticity within the range of 1-15 GPa. 
     
     
         14 . A method according to  claim 1  wherein the intramedullary prosthesis comprises at least one tang for engaging adjacent bone. 
     
     
         15 . A method according to  claim 1  wherein the intramedullary prosthesis is configured to accommodate bone in-growth. 
     
     
         16 . A method according to  claim 1  wherein the intramedullary prosthesis is spring-like and oscillates and vibrates so as to cause mechanical loading and catalyze fracture healing. 
     
     
         17 . A method according to  claim 1  wherein the porous structure comprises a stent. 
     
     
         18 . A method according to  claim 17  wherein the stent comprises Z struts. 
     
     
         19 . A method according to  claim 17  wherein the stent comprises W struts. 
     
     
         20 . A method according to  claim 17  wherein the stent comprises Z struts and W struts. 
     
     
         21 . A method according to  claim 1  wherein the intramedullary prosthesis is non-self-expanding. 
     
     
         22 . A method according to  claim 21  wherein the intramedullary prosthesis comprises stainless steel. 
     
     
         23 . A medical device for reducing fractures, the medical device being configured so that when it is deployed into the intramedullary canal of a bone, the medical device bridges the fracture, expands radially to apply hoop stress to the surrounding bone, and shortens as it expands to pull the fractured ends of the bone together. 
     
     
         24 . A medical device according to  claim 23  wherein the medical device comprises a stent. 
     
     
         25 . A medical device according to  claim 24  wherein the stent comprises a shape memory alloy. 
     
     
         26 . A medical device according to  claim 24  wherein the stent comprises Z struts. 
     
     
         27 . A medical device according to  claim 24  wherein the stent comprises W struts. 
     
     
         28 . A medical device according to  claim 24  wherein the stent comprises Z struts and W struts.