Resorptive Intramedullary Implant Between Two Bones or Two Bone Fragments

Abstract

The invention relates to a resorptive intramedullary implant between two bones or two bone fragments. The implant includes a single-piece body (1) having a generally elongate shape and having, at each end, areas for anchoring to the bone portions in question, characterized in that one of said areas (A1) has a cylindrical cross-section while the other area (A2) has a flat cross-section.

Claims

1-11. (canceled)

12. An intramedullary implant for insertion into first and second bone parts, the implant comprising: a threaded first end for anchoring to the first bone part; and a second end extending from the first end for anchoring to the second bone part, the second end having a body portion, a plurality of arms projecting from the body portion, and a projection extending from each of the arms.

13. The intramedullary implant of claim 12, wherein the plurality of arms includes first and second arms, the projection extending from the first arm is a first projection, the projection extending from the second arm is a second projection, and the first projection extends from the first arm in a different direction than a direction the second projection extends from the second arm.

14. The intramedullary implant of claim 13, wherein a third projection spaced apart from the first projection extends from the first arm.

15. The intramedullary implant of claim 14, wherein a fourth projection spaced apart from the second projection extends from the second arm.

16. The intramedullary implant of claim 14, wherein the first and the third projections extend in the same direction.

17. The intramedullary implant of claim 12, wherein the second end extends from the first end to define a step.

18. The intramedullary implant of claim 17, wherein either one or both of the first end and the second end define a longitudinal axis, and wherein the step extends in a direction transverse to the longitudinal axis and provides an abutment to prevent overinsertion of the implant into one of the bone parts.

19. The intramedullary implant of claim 12, wherein the arms define an opening therebetween.

20. The intramedullary implant of claim 12, wherein the intramedullary implant is made of a polymer.

21. The intramedullary implant of claim 12, wherein each of the projections includes a flat surface, the flat surfaces being coplanar.

22. An intramedullary implant for insertion into first and second bone parts, the implant comprising: a threaded first end for anchoring to the first bone part; and a second end extending from the first end for anchoring to the second bone part, the second end having a body portion defining an opening in a median portion thereof and a plurality of projections extending in different directions away from the body portion.

23. The intramedullary implant of claim 22, wherein at least one of the plurality of projections extends away from the body portion on a first side of the opening and at least one of the plurality of projections extends away from the body portion on a second side of the opening opposite the first side.

24. The intramedullary implant of claim 22, wherein first and second projections of the plurality of projections extend away from the body portion on the first side of the opening and a third projection of the plurality of projections extends away from the body portion on the second side of the opening in a different direction than the first and the second projections extend away from the body portion.

25. The intramedullary implant of claim 24, wherein the first and the second projections extend in the same direction.

26. The intramedullary implant of claim 22, wherein the body portion includes a pair of arms and the opening is defined by the pair of arms.

27. The intramedullary implant of claim 22, wherein the second end extends from the first end to define a step.

28. The intramedullary implant of claim 27, wherein either one or both of the first end and the second end define a longitudinal axis, and wherein the step extends in a direction transverse to the longitudinal axis and provides an abutment to prevent overinsertion of the implant into one of the bone parts.

29. The intramedullary implant of claim 22, wherein the intramedullary implant is made of a polymer.

30. The intramedullary implant of claim 22, wherein each of the plurality of projections includes a flat surface, the flat surfaces being coplanar.

31. An intramedullary implant for insertion into first and second bone parts, the implant comprising: a threaded first end for anchoring to the first bone part; and a second end extending from the first end for anchoring to the second bone part, the second end having a body portion and a plurality of projections extending in different directions away from the body portion, wherein the implant defines a longitudinal axis passing through the first and the second ends, and wherein the second end extends from the first end to define a step extending in a direction transverse to the longitudinal axis and providing an abutment to prevent overinsertion of the implant into one of the bone parts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention is explained in more detail hereinafter with reference to the attached drawings, in which:

[0018] FIG. 1 is a perspective view of the implant;

[0019] FIG. 2 is a front view of the implant before insertion into the bone part in question;

[0020] FIG. 3 is a side view corresponding to FIG. 2;

[0021] FIG. 4 is a view like FIG. 2 showing the position of the anchor arms of the flat section after insertion;

[0022] FIG. 5 is a perspective view of another advantageous embodiment of the implant;

[0023] FIGS. 6 and 7 show the installation of the implant into two bone parts.

DETAILED DESCRIPTION

[0024] The implant according to the invention has a one-piece body 1 of elongated shape and having a first proximal zone A1 and a second distal zone A2. The entire implant body is made of a resorptive material whose mechanical properties are determined for the implant to be resorbed in no less than about 6 months. In one embodiment, the implant is composed of lactic acid polymer or copolymer (PLA, PGA . . . ).

[0025] As will be described later in the description, the zones A1 and A2 have anchor formations for the respective bone parts. Taking into account the specific characteristics of the resorptive material and to attain the given object of anchor and stability, the zone A1 is of a cylindrical shape section whereas the other zone A2 is flat.

[0026] The zone A1 has a generally cylindrical outer surface 1a with a limited taper toward its free end. The surface la has a helical rib forming a screwthread 1a1.

[0027] The zone A2 is flat and has substantially in its center, an opening 1b adapted to enable elastic deformation of the zone A2. More particularly, the opening 1b defines at least two anchor arms 1c and 1d, each having at least one outwardly projecting tooth 1c1, 1d1.

[0028] Advantageously, between the two zones A1 and A2 the body 1 has a central zone C for transition adapted to resist shear and flexion forces that can occur at the end of a bone. By way of nonlimiting example, this median zone C can have a length of about 3.5 mm and a thickness of about 2 mm, for an overall implant length comprised between about 15 and 25 mm and a diameter of about 2 or 3 mm at the zone A1.

[0029] In the embodiment shown in FIG. 1, the two zones A1 and A2 are coaxial.

[0030] To solve the problem of adaptation to the shape of the implantation site, the anchor zones A1 and A2 can be offset at an angle adapted to the geometry of the bone site. This angle is comprised between about 1 and 30 and, advantageously, on the order of 10 when the implant is for foot arthrodesis (FIG. 5).

[0031] In this embodiment in which the two anchor zones are angularly offset, the bend is located so as to correspond substantially to the arthrodesis line of the bone parts being fused.

[0032] FIGS. 6 and 7 schematically show the positioning of the implant according to the invention between two bone parts O1 and O2. After suitable holes have been made in the bone by a rasp-type tool, the operator screws the thread la into the bone part O1 substantially up to the median zone C that serves as abutment preventing the implant from sinking too deeply into the bone (FIG. 6). The operator then fits the second bone part O2 back onto the anchor arms 1d and 1c of the zone A2, the anchor arms then spread and tighten by elasticity (FIG. 7).

[0033] The operative technique can be the following:

[0034] Drilling of the two holes with a conventional drill;

[0035] Preparation of the holes with a rasp for the flat side and a bone tap to form the inner screw thread on the cylindrical side;

[0036] Use of a screwdriver with a gripper end;

[0037] Screwing in the cylindrical side P1 [A1] for an arthrodesis IPP of the foot;

[0038] Fitting of the bone back onto the flat side [A2] of the implant.

[0039] The advantages are readily apparent from the description; in particular, it is to be emphasized and understood that the combination of the two anchor zones A1 and A2 of cylindrical and a flat shape, respectively, significantly enhances anchor and stability of the implant adapted to the geometry of the bone site and to the material properties, namely, a resorptive material.