Screw with anchor features

Abstract

Screws for anchoring in cancellous or other low-quality bone are described. One type of screw addresses the problem of extravasation of bone cement when filling an area of low-quality bone. The screw includes an expandable container for retaining bone cement and anchoring the screw in low-quality bone. The screw also includes an anchoring device for holding the screw in place in the bone while it is supplied with bone cement or other appropriate filler. The screw further includes a head for connecting to a rod or other apparatus. A second type of screw uses an expandable container to deform two or more fins to compress cancellous bone and/or anchor in cancellous bone.

What is claimed is: 
     
         1 . A surgical method comprising:
 inserting an expandable screw into bone, wherein the expandable screw comprises:
 a head portion; 
 a body portion distally attached to the head portion; and 
 an expandable portion distally attached to the body portion; 
   attaching a fluid source to the expandable screw, wherein the fluid source comprises:
 a reservoir; and 
 a tube extending from the reservoir; and 
   injecting a fluid source into the expandable screw, thereby causing the expandable portion to expand in width within the bone.   
     
     
         2 . The surgical method of  claim 1 , wherein the head portion comprises a receiver for receiving the fluid source. 
     
     
         3 . The surgical method of  claim 1 , wherein the body portion comprises threads. 
     
     
         4 . The surgical method of  claim 1 , wherein the expandable portion comprises a plurality of fins that can change shape or deform. 
     
     
         5 . The surgical method of  claim 4 , wherein the expandable screw further comprises a container received within the plurality of fins, wherein the container is configured to receive fluid from the fluid source to push the plurality of fins outward into bone. 
     
     
         6 . The surgical method of  claim 5 , wherein the fluid received in the container is bone cement (PMMA). 
     
     
         7 . The surgical method of  claim 1 , wherein the expandable screw is inserted into cancellous bone. 
     
     
         8 . The surgical method of  claim 1 , wherein the expandable portion comprises one or more fins connected to a knob. 
     
     
         9 . The surgical method of  claim 1 , wherein the expandable portion comprises one or more fins that can assume a convex shape when expanded. 
     
     
         10 . The surgical method of  claim 1 , wherein the reservoir is pressurized. 
     
     
         11 . A surgical method comprising:
 inserting an expandable screw into bone, wherein the expandable screw comprises:
 a head portion; 
 a body portion distally attached to the head portion; and 
 an expandable portion distally attached to the body portion, wherein a container is received within the expandable portion; 
   attaching a fluid source to the expandable screw, wherein the fluid source comprises:
 a reservoir; and 
 a tube extending from the reservoir; and 
   injecting a fluid into the expandable screw, thereby causing the expandable portion to expand in width within the bone.   
     
     
         12 . The surgical method of  claim 11 , wherein the expandable screw is inserted at least in part into cancellous bone. 
     
     
         13 . The surgical method of  claim 11 , wherein the body portion comprises a first set of threads and the expandable portion comprises a second set of threads, wherein the first set of threads are continuous with the second set of threads. 
     
     
         14 . The surgical method of  claim 11 , wherein the expandable portion comprises a plurality of fins that terminate in a screw tip. 
     
     
         15 . The surgical method of  claim 11 , wherein the expandable portion comprises a plurality of fins that are capable of expansion, wherein fluid is injected into the container, which causes the plurality of fins to expand outwardly. 
     
     
         16 . The surgical method of  claim 11 , wherein expansion of the expandable screw causes compression of cancellous bone. 
     
     
         17 . The surgical method of  claim 11 , wherein the expandable portion comprise a plurality of fins, wherein the fins are capable of curving convexly. 
     
     
         18 . The surgical method of  claim 11 , wherein the expandable portion comprises a plurality of fins capable of expansion, wherein in a non-expanded state the fins are straight and in an expanded state the fins are curved. 
     
     
         19 . The surgical method of  claim 11 , wherein the reservoir is pressurized. 
     
     
         20 . The surgical method of  claim 11 , wherein the fluid received in the container is bone cement (PMMA).