Devices for generating and applying compression within a body
This disclosure describes exemplary screw and intramedullary devices that are better able to bring bone fragments into close proximity with each other, generate a compressive load, and maintain that compressive load for a prolonged period of time while healing occurs. The devices are made of a shape memory material.
1 . An intramedullary fusion device, comprising:
a shaft made of a shape memory material and defining a longitudinal axis, the shaft including a threaded end region, a barbed end region, a central bridge region, and a cannulation that extends through the barbed end region, the threaded end region, and the central bridge region, wherein the central bridge region includes a first end and a second end, the barbed end region includes a plurality of spaced apart barbs extending from the first end of the central bridge region that are radially spaced relative to the longitudinal axis, each of the plurality of spaced apart barbs includes a plurality of spaced barbed features axially spaced relative to the longitudinal axis, the central bridge region has a generally cylindrical shape and an outer diameter that is smaller than a major diameter of the threaded end region and a major diameter of the barbed end region, and the threaded end region is directly adjacent to the central bridge region; a first bone-engaging feature provided on the threaded end region, wherein the first bone-engaging feature includes a thread helically wrapped around the shaft at the threaded end region,
wherein the plurality of spaced apart barbs are separated from one another by a slot that extends at least partially into the central bridge region; and
a second bone-engaging feature provided on the barbed end region, the second bone-engaging feature movable between an unbiased condition in which it is co-radial with the longitudinal axis of the shaft and a biased condition in which a cross-sectional profile of the barbed end region is reduced, wherein the second bone-engaging feature occupies at least a portion of the cannulation when the second bone-engaging feature is in the biased condition, and the second bone-engaging feature returns to the unbiased condition following insertion into a bone.
2 . An intramedullary fusion device, comprising:
a shaft made of a shape memory material and defining a longitudinal axis, the shaft including a threaded end region, a barbed end region, and a central bridge region, wherein a cannulation extends through the barbed end region, the threaded end region, and the central bridge region, the central bridge region includes a first end and a second end, the barbed end region includes a plurality of spaced apart barbs extending from the first end of the central bridge region that are radially spaced relative to the longitudinal axis, each of the plurality of spaced apart barbs includes a plurality of spaced barbed features axially spaced relative to the longitudinal axis, the central bridge region has a generally cylindrical shape and an outer diameter that is smaller than a major diameter of the threaded end region and a major diameter of the barbed end region, and the threaded end region is directly adjacent to the central bridge region,
wherein the plurality of spaced apart barbs are separated from one another by a slot that extends at least partially into the central bridge region;
a first bone-engaging feature provided on the threaded end region; and
a second bone-engaging feature provided on the barbed end region, the second bone-engaging feature movable between an unbiased condition in which it is co-radial with the longitudinal axis of the shaft and a biased condition in which a cross-sectional profile of the barbed end region is reduced.
3 . The intramedullary fusion device as recited in claim 2 , wherein the shape memory material is Nitinol.
4 . The intramedullary fusion device as recited in claim 2 , wherein the shape memory material is PEEK.
5 . The intramedullary fusion device as recited in claim 2 , wherein the first bone-engaging feature includes a thread helically wrapped around the shaft at the threaded end region.
6 . The intramedullary fusion device as recited in claim 2 , wherein the second bone-engaging feature occupies at least a portion of the cannulation when the second bone-engaging feature is in the biased condition.
7 . The intramedullary fusion device as recited in claim 6 , wherein the second bone-engaging feature returns to the unbiased condition following insertion into a bone.
8 . The intramedullary fusion device as recited in claim 2 , wherein the central bridge region is neither threaded nor barbed.
9 . The intramedullary fusion device as recited in claim 2 , wherein the plurality of spaced apart barbs comprises four spaced apart barbs.
10 . The intramedullary fusion device as recited in claim 2 , wherein the intramedullary fusion device is receivable within a recess of a delivery device.
11 . The intramedullary fusion device as recited in claim 10 , wherein the second bone-engaging feature is removably held within the recess of the delivery device.
12 . The intramedullary fusion device as recited in claim 2 , wherein the slot extends through an outer diameter surface of the central bridge region.
13 . An intramedullary fusion system, comprising:
a delivery device including a recess and a drive feature; and
an intramedullary fusion device removably held within the recess of the delivery device, wherein the intramedullary fusion device includes:
a shaft made of a shape memory material and defining a longitudinal axis, the shaft including a threaded end region, a barbed end region, and a central bridge region, wherein a cannulation extends through the barbed end region, the threaded end region, and the central bridge region, the central bridge region includes a first end and a second end, the barbed end region includes a plurality of spaced apart barbs extending from the first end of the central bridge region that are radially spaced relative to the longitudinal axis, each of the plurality of spaced apart barbs includes a plurality of spaced barbed features axially spaced relative to the longitudinal axis, the central bridge region has a generally cylindrical shape and an outer diameter that is smaller than a major diameter of the threaded end region and a major diameter of the barbed end region, and the threaded end region is directly adjacent to the central bridge region,
wherein the plurality of spaced apart barbs are separated from one another by a slot that extends at least partially into the central bridge region;
a first bone-engaging feature provided on the threaded end region; and
a second bone-engaging feature provided on the barbed end region, the second bone-engaging feature movable between an unbiased condition in which it is co-radial with the longitudinal axis of the shaft and a biased condition in which a cross-sectional profile of the barbed end region is reduced; and
the drive feature of the delivery device is positioned between adjacent barbs of the plurality of spaced apart barbs of the barbed end region when the intramedullary fusion device is received within the recess of the delivery device.
14 . The intramedullary fusion system as recited in claim 13 , wherein the drive feature engages at least one of the plurality of spaced apart barbs to allow the threaded end region to be screwed into a bone.
15 . The intramedullary fusion system as recited in claim 13 , wherein the drive feature extends outwardly from a floor of the recess.