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 pedicle screw, 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 along at least a portion of the length of the shank 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, wherein the three-dimensional open network body comprises at least one of: a scaffold of random open and interconnected pores formed along at least a central portion of the shank, at least one elongate helix formed along the entire length of the shank, or an organized or random arrangement of trusses formed along the entire length of the shank;
a partially spherical pedicle screw head that is monolithic with the shank at the proximal end of the shank, wherein at least a portion of the pedicle screw head includes the three-dimensional open network body;
a tip that is tapered relative to the shank and is integral with the shank at the shank's distal end;
and
at least one solid thread extending along an external surface of the shank,
wherein the at least one solid thread and the three-dimensional open network body are formed from metal, and
wherein the at least one solid thread is integral with a surface of the three-dimensional open network body.
2. The pedicle screw of claim 1 , wherein the scaffold of random open and interconnected pores mimic a trabecular bone structure.
3. The pedicle screw of claim 1 , wherein the three-dimensional open network body is formed by a process selected from the group consisting of: additive (3D) manufacturing, conventional machining, assembly of subparts, and combinations thereof.
4. The pedicle screw of claim 1 , wherein the at least one elongate helix includes a primary helix and a secondary helix defining a dual helical body.
5. The pedicle screw of claim 4 , wherein the secondary helix is entwined with the primary helix, each helix having a different pitch.
6. The pedicle screw of claim 1 , wherein the open network body comprises the organized arrangement of trusses.
7. The pedicle screw of claim 1 , wherein the at least one solid thread includes:
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.
8. The pedicle screw of claim 7 , 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 pedicle screw 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 pedicle screw head is unthreaded.
9. The pedicle screw of claim 1 , wherein the shank includes the three-dimensional open network body along an entirety of the length of the shank.
10. The pedicle screw of claim 1 , wherein when the three-dimensional open network body comprises the scaffold of random open and interconnected pores, the pedicle screw includes a solid-walled cannula formed through the shank, the pedicle screw head, and the tip, and the scaffold of random open and interconnected pores surrounds the solid-walled cannula.
11. The pedicle screw of claim 1 , wherein when the three-dimensional open network body comprises the organized or random arrangement of trusses, the pedicle screw is not cannulated through the shank, the pedicle screw head, and the tip, and the shank includes a solid core and the organized or random arrangement of trusses surrounds the solid core.
12. The pedicle screw of claim 1 , wherein when the three-dimensional open network body comprises the scaffold of random open and interconnected pores, the shank further 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.
13. The pedicle screw of claim 1 , wherein the shank diameter along at least the proximal end of the shank is approximately equal to a diameter of the pedicle screw head.
14. The pedicle screw of claim 1 , wherein the shank diameter along at least the proximal end of the shank is smaller than a diameter of the pedicle screw head, and wherein the pedicle screw head is substantially spherical or hemispherical.
15. A pedicle screw comprising:
a shank having a length from a proximal end to a distal end;
a non-porous, partially spherical pedicle screw head that is monolithic with the shank at its proximal end, the non-porous pedicle screw head being formed from a solid material and comprising a tool recess configured for engagement with a driving instrument;
a tip that is integral with the shank at its distal end, the tip being non-porous and formed from a solid material; and
at least one non-porous thread formed along an external surface of the pedicle screw;
wherein a first portion of the shank adjacent the distal end includes a three-dimensional open network body comprising a scaffold of open and interconnected pores mimicking a 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, and wherein a second portion of the shank adjacent the proximal end is non-porous,
wherein the at least one thread is continuous along a thread length of the pedicle screw from the tip into and over at least a portion of the second portion of the shank,
wherein the at least one thread and the three-dimensional open network body are formed from metal,
wherein the at least one thread is integral with a surface of the three-dimensional open network body, and
wherein the three-dimensional open network body is exposed in gaps between the at least one thread.
16. A fixation implant comprising:
a shank having a length from a proximal end to a distal end;
a non-porous, partially spherical head that is monolithic with the shank at its proximal end, the partially spherical head being formed from a solid material and comprising a tool recess configured for engagement with a driving instrument;
a tip that is integral with the shank at its distal end, the tip being non-porous and formed from a solid material; and
at least one non-porous thread formed along an external surface of the fixation implant;
wherein a first portion of the shank adjacent the distal end includes a three-dimensional open network body comprising a scaffold of open and interconnected pores mimicking a 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, and wherein a second portion of the shank adjacent the proximal end is non-porous,
wherein the at least one thread is continuous along a thread length of the fixation implant from the tip into and over at least a portion of the second portion of the shank,
wherein the at least one thread and the three-dimensional open network body are formed from metal,
wherein the at least one thread is integral with a surface of the three-dimensional open network body, and
wherein the three-dimensional open network body is exposed in gaps between the at least one thread.
17. The fixation implant of claim 16 , wherein the three-dimensional open network body includes at least one additive material selected from the group consisting of polymers, biodegradable polymers, PEK, PEEK, PAEK, bone material, BMP, hydroxyapatite, and combinations thereof.