Shape adaptable intramedullary fixation device
Implantable devices for fixation of curved bone such as the pelvic ring pubic symphysis and acetabulum, and methods for the use of the devices are disclosed. The implantable devices are convertible between a flexible state and a rigid state, and include an elongate structure having a proximal bone interface, a main body, and a distal bone interface. In a flexible state, the devices may be inserted along, and conform to a curved pathway, and in the rigid state, the devices may support the mechanical loads required to fixate a fracture.
1. A medical apparatus for bone fixation, the medical apparatus comprising:
a flexible body defining a main axis, having a proximal end and a distal end, and including individual segments each having a mechanical engagement structure configured to interlock the individual segment to at least one adjacent individual segment, a face, and apertures arranged along the face to form lumens in the flexible body;
a bone-engagement feature positioned substantially at the distal end, and
fibers extending through the lumens, wherein the apparatus is configured such that fixing the fibers into position relative to each other causes the flexible body to transition to a rigid state.
2. The medical apparatus of claim 1 wherein while the flexible body is locked, the individual segments are held together in a fixed relationship.
3. The medical apparatus of claim 1 wherein the fibers are mechanically fixed substantially at the distal end.
4. The medical apparatus of claim 1 wherein the fibers are arranged within the apertures of the individual segments such that the flexible body is configured to support shear loading between the individual segments.
5. The medical apparatus of claim 1 wherein each of the individual segments comprises a respective first end and a respective second end, the first end having a male engagement structure and the second end having a female engagement receptacle configured to receive a male engagement structure of another individual segment.
6. The medical apparatus of claim 5 wherein the male engagement structure is configured to operate as a fulcrum.
7. The medical apparatus of claim 5 wherein the male engagement structure and the female receptacle are configured to transfer torque between the individual segments.
8. The medical apparatus of claim 5 wherein the male engagement structure and the female receptacle of at least two of the individual segments are of different sizes.
9. The medical apparatus of claim 5 wherein the male engagement structure and the female receptacle are configured to prevent the individual segments from separating while a tensile force is applied between the proximal and distal ends.
10. The medical apparatus of claim 1 wherein at least two of the fibers are of different lengths.
11. The medical apparatus of claim 1 wherein at least two of the individual segments are of different sizes, shapes, masses, or lengths.
12. The medical apparatus of claim 1 wherein:
the fibers are configured to move relative to each other at the proximal end while the flexible body is in a flexible state; and
the fibers are configured to be fixed into position relative to each other at the proximal end while the flexible body is in a rigid state.
13. The medical apparatus of claim 1 wherein the fibers are configured to be fixed into position at the proximal end of the flexible body while the flexible body is in a rigid state.
14. A medical apparatus for fixation of fractured bone, the apparatus comprising:
an elongate body having a proximal end, a distal end, and a flexible body portion including interconnected segments, at least one of the interconnected segments including a face having apertures that are spaced apart from each other;
a bone-engagement feature positioned at the distal end; and
a plurality of fibers disposed longitudinally within the elongate body circumferentially spaced in relation to one another and each passing through a respective one of the apertures, wherein the apparatus is configured such that fixing the fibers into position relative to each other causes the flexible body portion to transition into a rigid state.
15. The medical apparatus of claim 14 wherein at least one of the interconnected segments includes a first engagement portion configured to engage, pivotally, a second engagement portion of an adjacent interconnected segment.
16. The medical apparatus of claim 15 wherein the bone-engagement feature includes an end recessed portion configured to receive the first engagement portion of one of the interconnected segments.
17. The medical apparatus of claim 14 wherein each of at least one of the interconnected segments includes:
a respective first end and a respective protrusion extending axially from the first end; and
a respective second end and a respective recessed portion disposed in the second end and configured to receive a protrusion of an adjacent one of the interconnected segments.
18. The medical apparatus of claim 17 wherein the respective protrusion and the respective recessed portion of each of the at least one of the interconnected segments are radially spaced approximately ninety degrees from each other.
19. The medical apparatus of claim 17 wherein:
the respective protrusion includes a respective set of two individual tabs; and
the respective recessed portion includes a respective set of two apertures.
20. The medical apparatus of claim 19 wherein:
the interconnected segments each have a respective outer cylindrical surface, and
a respective at least one side of each the two individual tabs coincides with the outer cylindrical surface.
21. The medical apparatus of claim 14 wherein the apertures comprise:
a first aperture located at a center of the at least one interconnected segment and configured to receive a guidewire for guiding the flexible body portion at a desired location within a fractured bone; and
second apertures circumferentially spaced around the first aperture, wherein each of the fibers passes through a respective one of the second apertures.
22. A medical apparatus for fixation of fractured bone, the apparatus comprising:
an elongate body having a proximal end, a distal end, and a flexible body portion including interconnected segments, at least one of the interconnected segments including a face having apertures that are spaced apart from each other;
a bone-engagement feature positioned at the distal end;
a plurality of fibers disposed longitudinally within the elongate body circumferentially spaced in relation to one another and each passing through a respective one of the apertures;
a first aperture located at a center of the at least one interconnected segment and configured to receive a guidewire for guiding the flexible body portion at a desired location within a fractured bone; and
second apertures circumferentially spaced around the first aperture, wherein each of the fibers passes through a respective one of the second apertures.