Intramedullary anchor for interphalangeal arthrodesis

Patent metadata

Field	Value
Publication number	US-10080597-B2
Application number	US-201414420260-A
Country	US
Kind code	B2
Filing date	Dec 19, 2014
Priority date	Dec 19, 2014
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

An intramedullary implant has opposite ends inserted into bores in abutting phalanges for correcting hammer toe and for similar arthrodesis procedures. A rear end of the implant may be threaded and is received in a bore in the proximal phalanx. A front end has an asymmetric pointed shape with longitudinally and/or angularly spaced rear-facing gripping flukes. The pointed front end is received in the middle phalanx. The asymmetric pointed shape is self-aligning, enabling entry to begin without first longitudinally aligning the bones. The rear end when screwed into place can be rotated to select the orientation of the asymmetric pointed shape. The pointed front end is inserted and pushed to bring the phalanges into abutment where the implant holds them against retraction or rotational displacement.

First claim

What is claimed is:

1. An intramedullary implant, comprising;
an implant body including an anchor end and a shaft, the shaft defining a longitudinal axis, the anchor end being configured for insertion in one direction into a bore in a bone for gripping sides of the bore, and resisting retraction of the intramedullary implant from the bone in an opposite direction;
wherein the anchor end is a single conical body having a surface shaped as a portion of a single cone, the surface tapering outward and rearward from an apex point of the single cone, where the apex point is disposed along the longitudinal axis of the shaft, the single cone having an undercut on a single side of the longitudinal axis, the undercut extending only partially around the single cone so the cone is not rotationally symmetrical about an axis thereof, the surface extending to a first gripping fluke formed by a barb generated by the undercut and a second gripping fluke formed by a rear edge of the single conical body spaced back from the apex;
wherein said first and second gripping flukes are longitudinally spaced from one another relative to the longitudinal axis and taper outward and rearward, and
wherein the conical body defines a central axis passing through the apex point, the central axis disposed at an oblique angle with respect to the longitudinal axis such that a distance from the longitudinal axis to a first point on the surface is greater than a distance from the longitudinal axis to a second point on the surface which is diametrically opposed from and longitudinally aligned with the first point with respect to the longitudinal axis.

2. The implant of claim 1 , wherein the gripping fluke that is closer to the apex point has a greater angle of outward and rearward taper than the gripping fluke that is farther from the apex point.

3. The implant of claim 1 , wherein a diametrical span between locations on the first and second gripping flukes which are located on diametrically opposite portions of the surface is configured to be greater than an internal diameter of the bore, whereby the gripping flukes are configured to engage opposite sidewalls of the bore.

4. The implant of claim 1 , wherein the implant forms at least part of a prosthesis for arthrodesis of an inter-phalangeal joint and is configured for engagement of both phalanges abutting at said joint.

5. The implant of claim 1 , wherein the shaft is threaded.

6. A method for surgical repair of an interphalangeal joint, comprising:
forming a bore along a longitudinal bore axis in at least one phalanx at the joint;
providing an intramedullary support including an implant body including an anchor end and a shaft, the shaft defining a longitudinal axis, wherein the anchor end is a single conical body having a surface shaped as a portion of a single cone, the surface tapering outward and rearward from an apex point of the single cone, where the apex point is disposed along the longitudinal axis of the shaft, the single cone having an undercut on a single side of the longitudinal axis of the shaft, the undercut extending only partially around the single cone so the cone is not rotationally symmetrical about an axis thereof, the surface extending to a first gripping fluke formed by a barb generated by the undercut and a second gripping fluke formed by a rear edge of the single conical body spaced back from the apex, wherein said first and second gripping flukes are longitudinally spaced from one another relative to the longitudinal axis and taper outward and rearward, and wherein the conical body defines a central axis passing through the apex point, the central axis disposed at an oblique angle with respect to the longitudinal axis of the shaft such that a distance from the longitudinal axis of the shaft to a first point on the surface is greater than a distance from the longitudinal axis of the shaft to a second point on the surface which is diametrically opposed from and longitudinally aligned with the first point with respect to the longitudinal axis of the shaft;
orienting the implant body so the longitudinal axis of the shaft is oblique to the longitudinal bore axis and moving the apex point of the intramedullary support into the bore;
advancing the anchor end into the bore, whereby the anchor end brings the longitudinal axis of the shaft into alignment with the bore axis; and
continuing to advance the anchor end into the bore to an end position at which the gripping flukes engage the bore to prevent retraction.

7. The method of claim 6 , further comprising inserting the shaft into a second phalanx and rotationally aligning the intramedullary support such that the central axis is parallel to a sagittal plane prior to moving the anchor end into the bore.

8. The method of claim 7 , wherein the shaft is threaded, wherein said inserting of the shaft comprises screwing the intramedullary support into the second phalanx.

9. The method of claim 8 , wherein the anchor end protrudes beyond the second phalanx after screwing the intramedullary support into the second phalanx.

10. The method of claim 9 , further comprising rotating the shaft to selectively place the surface of the anchor end in position for guiding along the edge of the bore.

11. An intramedullary implant, comprising;
an implant body having a longitudinal axis; and
an anchor along the longitudinal axis, the anchor being configured for insertion in one direction into a bore in a bone for gripping sides of the bore, and resisting retraction of the intramedullary implant from the bone in an opposite direction;
wherein the anchor has:
an anchor head at a leading end of the implant body, the anchor having a point located along the longitudinal axis;
three convex surfaces tapering outward and rearward from the point at spaced angles around the anchor head, to respective first gripping flukes spaced back from the leading end, the gripping flukes defined by undercuts in the three convex surfaces, at least two of the undercuts being located at respectively different distances along the longitudinal axis relative to the point, the anchor head having three concave surfaces angularly spaced between respective ones of the three convex surfaces; and
three second gripping flukes longitudinally spaced from the first gripping flukes relative to the longitudinal axis, the three second gripping flukes angularly spaced from the three first gripping flukes.

12. The intramedullary implant of claim 11 , wherein the convex surfaces are arranged at respectively different angles from the longitudinal axis of the implant body.

Assignees

• Wright Medical Tech Inc

Inventors

• Shemwell Jessica L
• Branthover Pearce

Classifications

• A61F2002/4228

  for interphalangeal joints, i.e. IP joints · CPC title

• A61B17/7291 Primary

  for small bones, e.g. in the foot, ankle, hand or wrist · CPC title

• A61B17/7283

  with special cross-section of the nail · CPC title

• A61B17/7233

  with special means of locking the nail to the bone · CPC title

• A61B2017/681

  Alignment, compression, or distraction mechanisms · CPC title