Implants for tissue fixation and fusion
A fixation implant includes a head, a shank and a distal tip, and one or more of the head, shank and distal tip may be cannulated. The shank includes a threaded ingrowth portion extending from the head to the tapered distal tip that includes external threads, and at least one open network body extending along the length of the ingrowth portion. The open network body selected from one or a combination of a helix, an arrangement of trusses, a scaffold of open and interconnected pores, a porous framework of random open and interconnected pores, and combinations of these.
1. A fixation implant, comprising:
a shank having a length from a proximal end to a distal end, a shank diameter that is continuous or tapered from the proximal end to the distal end, and a shank periphery along the length of the shank, the shank comprising a three-dimensional open network body comprising a scaffold of random open and interconnected pores mimicking trabecular bone structure that allows communication through the three-dimensional open network body and 360 degrees around the shank to optimize complete bony integration when inserted in bone;
a head that is integral with the shank at a proximal end of the shank;
a solid tip that is tapered relative to the shank and is integral with the shank at the shank's distal end;
a first solid thread having a first pitch extending along an external surface of the tip;
a second solid thread having a second pitch extending along a first portion of an external surface of the shank; and
a third solid thread having a third pitch extending along a second portion of the external surface of the shank,
wherein:
the second portion of the external surface of the shank is disposed between the first portion of the external surface of the shank and the head;
the second pitch is greater than each of the first pitch and the third pitch;
the first solid thread is separated from the second solid thread by a first unthreaded portion of the shank;
the second solid thread is separated from the third solid thread by a second unthreaded portion of the shank; and
the head is unthreaded.
2. The fixation implant of claim 1 , wherein the open and interconnected matrix is formed from a metal, a biocompatible polymer, or a combination thereof.
3. The fixation implant of claim 1 , wherein the open and interconnected matrix is formed by a process selected from the group consisting of: additive (3D) manufacturing, conventional machining, assembly of subparts, and combinations thereof.
4. The fixation implant of claim 1 , wherein the shank includes a plurality of fenestrations selected from the group consisting of an opening, a slot, or a combination thereof around the periphery of the shank to further enhance bony ingrowth.
5. The fixation implant of claim 1 , wherein the shank diameter along at least the proximal end of the shank is approximately equal to a diameter of the head.
6. The fixation implant of claim 1 , wherein the shank diameter along at least the proximal end of the shank is smaller than a diameter of the head, and wherein the head is substantially cylindrical.
7. The fixation implant of claim 1 , wherein the shank diameter along at least the proximal end of the shank is smaller than a diameter of the head and wherein the head is substantially hemispherical.
8. The fixation implant of claim 1 , wherein the shank diameter along at least the proximal end of the shank is smaller than a diameter of the head and wherein the head is substantially frustroconical from the proximal end of the shank.
9. The fixation implant of claim 1 , wherein the fixation implant is cannulated through the shank, the head and the tip.
10. The fixation implant of claim 1 , wherein the fixation implant is not cannulated through the shank, the head and the tip.