Composite Screw Having A Metallic Pin and a Polymeric Thread
A composite screw preferably made of a metallic pin embedded in a polymeric tubular structure having the outwardly facing threads, wherein the metallic pin comprises a screw head, an intermediate shaft and a screw tip, and the polymeric threaded tube is either molded onto the metallic shaft or the threaded is machined after molding a polymeric structure onto the shaft.
1 . A composite bone fixation system comprising:
i) a pin comprising:
a) a proximal head having a first maximum diameter D 1 ,
b) a distal tip having a second maximum diameter D 2 , and
c) an intermediate shaft portion having an outer surface defining a third maximum diameter D 3 ,
ii) a threaded polymeric tube comprising an inner bore and a threaded outer surface,
wherein the threaded polymeric tube is disposed over the outer surface of the substantially cylindrical intermediate shaft portion, and
wherein each of the first maximum diameter D 1 and second maximum diameter D 2 is greater than the third maximum diameter D 3 .
2 . A composite bone fixation system of claim 1 wherein the distal tip comprises a distally narrowing insertion taper.
3 . The composite bone fixation system of claim 1 wherein the distal tip is detachable from the shaft.
4 . The composite bone fixation system of claim 1 wherein detachable distal tip and the shaft comprise a male/female connection.
5 . The composite bone fixation system of claim 1 wherein the male/female connection is threaded.
6 . The composite bone fixation system of claim 1 wherein the male/female connection is a taper lock.
7 . The composite bone fixation system of claim 1 wherein the pin is metallic.
8 . The composite bone fixation system of claim 1 wherein the outer surface of the shaft portion is textured for increased adhesion of polymer
9 . The composite bone fixation system of claim 1 wherein the polymeric tube comprises carbon fiber.
10 . A method of performing surgery, comprising the steps of:
a) inserting into a vertebral body a screw comprising:
a pin comprising:
j) a proximal head having a first maximum diameter D 1 ,
ii) a distal tip having a second maximum diameter D 2 , and
iii) an intermediate shaft portion having an outer surface defining a third maximum diameter D 3 ,
a threaded polymeric tube comprising an inner bore and a threaded outer surface,
wherein the threaded polymeric tube is disposed over the outer surface of the intermediate shaft portion.
11 . A composite bone fixation system comprising:
i) a pin comprising:
a) a proximal head,
b) a distal tip, and
c) an intermediate shaft portion having a distally narrowing outer surface,
ii) a threaded polymeric tube comprising an inner bore and a threaded outer surface,
wherein the threaded polymeric tube is disposed over the outer surface of the intermediate shaft portion.
12 . The composite bone fixation system of claim 11 wherein the distal tip is formed by the distal narrowing of the intermediate shaft portion.
13 . The composite bone fixation system of claim 11 wherein the distal tip comprises a distally narrowing insertion taper.
14 . The composite bone fixation system of claim 11 wherein the distal tip is detachable from the shaft.
15 . The composite bone fixation system of claim 11 wherein detachable distal tip and the shaft comprise a male/female connection.
16 . The composite bone fixation system of claim 11 wherein the male/female connection is threaded.
17 . The composite bone fixation system of claim 11 wherein the male/female connection is a taper lock.
18 . The composite bone fixation system of claim 11 wherein the pin is metallic.
19 . The composite bone fixation system of claim 11 wherein the outer surface of the shaft portion is textured for increased adhesion of polymer
20 . The composite bone fixation system of claim 11 wherein the polymeric tube comprises carbon fiber.