# Patent

## Title
Components for artificial joints

## Abstract

A component of an artificial joint according to an exemplary aspect of the present disclosure includes, inter alia, a hollow tube including bone ingrowth material. Further, the hollow tube is selectively expandable. The bone ingrowth material allows the component to become biologically fixed to adjacent bone. Further, expansion of the hollow tube increases friction between the hollow tube and the adjacent bone, which increases stability.

## Background
BACKGROUND
This disclosure relates to components for artificial joints and, more particularly, to artificial femoral and tibial components for use during unicondylar or total knee arthroplasty procedures.
A total knee arthroplasty, also known as total knee replacement, is a surgical procedure in which parts of the knee joint are replaced with artificial components (sometimes referred to as prostheses). In a typical total knee arthroplasty procedure, an artificial femoral component is attached to the femur, an artificial tibial component is attached to the tibia, and a spacer is provided between the femoral and tibial components.
SUMMARY
This disclosure describes components for artificial joints. The components can be used during joint replacement procedures. For example, the components could be artificial femoral or tibial components for use during unicondylar or total knee arthroplasty procedures.
An artificial joint component according to an exemplary aspect of the present disclosure includes, inter alia, a hollow tube including bone ingrowth material. Further, the hollow tube is selectively expandable. The bone ingrowth material allows the component to become biologically fixed to adjacent bone. Further, expansion of the hollow tube increases friction between the hollow tube and the adjacent bone, which increases stability.
In a further embodiment, the component includes an opening aligned with the hollow tube, and a plug receivable in the opening. The plug is configured to engage an interior of the hollow tube to expand the hollow tube. The hollow tube may, in some embodiments, include a slit along substantially the entire length thereof to allow for expansion.
An artificial knee according to an exemplary aspect of the present disclosure includes, inter alia, an artificial femoral component including a hollow tube having bone ingrowth material, and an artificial tibial component including a hollow tube having bone ingrowth material. Further, the hollow tube of one of the artificial femoral component and the artificial tibial component is selectively expandable. Additionally, the artificial knee includes a spacer located between the artificial femoral component and the artificial tibial component.
In a further embodiment, the artificial femoral component further includes an anterior surface providing an articulating surface relative to the spacer. The artificial femoral component also includes a posterior surface substantially covered by bone ingrowth material. Further, the hollow tube of the artificial femoral component projects in a posterior direction from the posterior surface.
A method according to an exemplary aspect of the present disclosure includes, inter alia, expanding a hollow tube of a component of an artificial joint, the hollow tube including bone ingrowth material.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates an example artificial joint. In this example, the artificial joint is an artificial knee.
FIG. 2A is a posterior-perspective view of an example artificial femoral component.
FIG. 2B is a posterior view of the artificial femoral component of FIG. 2A.
FIG. 2C is a cross-sectional view of the artificial femoral component taken along line 2C-2C of FIG. 2B.
FIG. 2D is a close-up view of the encircled area in FIG. 2C, and illustrates a hollow tube with bone ingrowth material on a solid backing.
FIG. 2E is a close-up view of the encircled area of FIG. 2C, and illustrates a hollow tube made entirely of bone ingrowth material.
FIG. 3A is a superior-perspective view of an example artificial tibial component.
FIG. 3B is a superior-perspective view of the artificial tibial component of FIG. 3A, and illustrates first and second plugs inserted into respective openings.
FIG. 3C is a side view of the artificial tibial component of FIG. 3A.
FIG. 4A is a cross-sectional view of the artificial tibial component taken along line 4A-4A of FIG. 3A.
FIG. 4B is a cross-sectional view of the artificial tibial component taken along line 4B-4B of FIG. 3B.
FIG. 4C is a cross-sectional, side view of the artificial tibial component illustrating a second example plug type.
FIG. 4D is a cross-sectional, side view of the artificial tibial component illustrating a third example plug type.
FIG. 5 is a flow chart representative of an example method according to this disclosure.



DETAILED DESCRIPTION
This disclosure describes components for artificial joints. The components can be used during joint replacement procedures. For example, the components could be artificial femoral or tibial components for use during unicondylar or total knee arthroplasty procedures.
In some embodiments, a component of an artificial joint includes a hollow tube having bone ingrowth material. The hollow tube includes bone ingrowth material adapted to provide stability to the component via biological fixation. The hollow tube is also selectively expandable. Expansion of the hollow tube increases friction between the hollow tube and the adjacent bone, which further increases fixation. The artificial components of the present disclosure are “cementless,” i.e., they can be fixed to bone without the use of bone cement.
In a further embodiment, the component includes an opening aligned with the hollow tube, and a plug receivable in the opening. The plug is configured to engage an interior of the hollow tube to expand the hollow tube.
In a further embodiment, the opening and the plug are threaded.
In a further embodiment, the plug includes a threaded shank projecting beyond the hollow tube and configured to engage bone.
In a further embodiment, the plug includes a flared portion distal of the threads, the flared portion configured to engage an interior of the hollow tube.
In a further embodiment, the hollow tube includes at least one slit along a substantially an entire length thereof.
In a further embodiment, the hollow tube includes a layer of bone ingrowth material provided on a substantially solid backing material.
In a further embodiment, the hollow tube consists of bone ingrowth material.
In a further embodiment, the hollow tube is substantially cylindrical and defines an interior cavity.
In a further embodiment, the component is a tibial tray, and wherein the hollow tube projects from an inferior surface of the tibial tray.
An artificial knee according to an exemplary aspect of the present disclosure includes, inter alia, an artificial femoral component including a hollow tube having bone ingrowth material, and an artificial tibial component including a hollow tube having bone ingrowth material. Further, the hollow tube of one of the artificial femoral component and the artificial tibial component is selectively expandable. Additionally, the artificial knee includes a spacer located between the artificial femoral component and the artificial tibial component.
In a further embodiment, the artificial femoral component further includes an anterior surface comprising an articulating surface relative to the spacer. The artificial femoral component also includes a posterior surface substantially covered by bone ingrowth material. Further, the hollow tube of the artificial femoral component projects in a posterior direction from the posterior surface.
In a further embodiment, the artificial femoral component includes two hollow tubes, and each of the hollow tubes of the artificial femoral component includes bone ingrowth material.
In a further embodiment, the artificial tibial component further includes an opening aligned with the hollow tube of the artificial tibial component, and a plug receivable in the opening. The plug is configured to engage an interior of the hollow tube to expand the hollow tube.
In a further embodiment, the opening and the plug are threaded.
In a further embodiment, the plug includes one of (1) a threaded shank projecting beyond the hollow tube and configured to engage bone, and (2) a flared portion distal of the threads and configured to engage the hollow tube.
In a further embodiment, the hollow tube of the artificial tibial component includes at least one slit along substantially the entire length thereof.
A method according to an exemplary aspect of the present disclosure includes, inter alia, expanding a hollow tube of a component of an artificial joint, the hollow tube including bone ingrowth material.
In a further embodiment, the method further includes forming a hole in bone and inserting the hollow tube into the hole. The hollow tube is sized to substantially correspond to the size of the hole.
In a further embodiment, the hollow tube is expanded as a plug is inserted into an opening of the component.
FIG. 1 illustrates an example artificial joint 20. In this non-limiting example, the artificial joint 20 is an artificial knee. While an artificial knee is specifically mentioned herein, this disclosure is not limited to artificial knees and can have applications in other parts of the body.
The artificial joint 20 includes an artificial femoral component 22 connected to a femur 24, an artificial tibial component 26 connected to a tibia 28, and a spacer 30 arranged between the artificial femoral component 22 and the artificial tibial component 26. In this non-limiting example, the artificial femoral and tibial components 22, 26 are made of metallic materials, and the spacer 30 is made of a plastic material. However, this disclosure is not limited to these particular materials.
In a non-limiting example, the artificial tibial component 26 is a tibial tray having a base plate 32. A superior, or top, portion of the base plate 32 is configured to support the spacer 30, and the inferior, or bottom, of the base plate 32 is configured to mate with a tibial plateau cut 33. The “superior” and “inferior” directions are labeled in the figures for purposes of explanation only.
The artificial femoral component 22 includes an anterior surface 34, which provides an articulating surface that engages the spacer 30. The artificial femoral component 22 further includes a posterior surface 36 configured to mate with cuts of the femur 24.
FIG. 2A illustrates an example artificial femoral component 22 from a posterior perspective. The “anterior” and “posterior” directions are labeled across the figures for purposes of explanation only. In this example, the posterior surface 36 of the artificial component 22 has proximal and distal planar surfaces 38, 40, and a planar chamfer surface 42 extending between the proximal and distal planar surfaces 38, 40. The planar surfaces 38, 40, 42 correspond to cuts made in the femur 24.
In this example, the posterior surface 36 is substantially covered with a layer 44 of bone ingrowth material. The bone ingrowth material is relatively porous, which allows bone to grow into the layer 44. The bone ingrowth material may be provided by a metal foam material in some examples. As bone grows into the layer 44, the artificial femoral component 22 becomes biologically fixed to the femur 24. The layer 44 of bone ingrowth material may be fused to the posterior side of the femoral component 22. In another non-limiting example, the layer 44 is provided using a deposition coating process.
To further increase stability, the artificial femoral component 22 includes first and second hollow tubes 46, 48 projecting from the posterior surface 36 in a posterior direction. In this example, the first hollow tube 46 projects from the surface 38, and the second hollow tube 48 projects from the surface 42. Further, the first and second hollow tubes 46, 48 are substantially cylindrical and have a hollow interior providing respective cavities 50, 52 therein. While two hollow tubes are illustrated in this example, this disclosure extends to artificial femoral components having one or more hollow tubes.
With reference to FIG. 2B, the first hollow tube 46 is arranged about a first axis A1, and the second hollow tube 48 is arranged around about a second axis A2. In this example, the axes A1, A2 are spaced-apart from one another in the medial and lateral directions. The “medial” and “lateral” directions are shown in FIG. 2B for purposes of explanation only. Further, as seen in FIG. 2C, the first and second axes A1, A2 are inclined such that they are substantially parallel to one another. Additionally, in this example, the first hollow tube 46 has a length L1, which is shorter than a length L2 of the second hollow tube 48.
The first and second hollow tubes 46, 48 are configured such that bone may grow into the first and second cavities 50, 52, which increases the surface area of the tubes 46, 48 exposed to bone, which in turn increases fixation. But further, bone may grow into at least a portion of the first and second hollow tubes 46, 48 themselves.
In one example, as illustrated in FIG. 2D, the first hollow tube 46 is provided by a solid backing material 54 supporting an outer layer 56 of bone ingrowth material. Alternatively, as illustrated in FIG. 2E, the hollow tube 46 may be provided entirely by bone ingrowth material 58. These arrangements allow bone to grow into the hollow tubes 46, 48, which increases stability and reliability of the artificial femoral component 22. While the first hollow tube 46 is illustrated in FIGS. 2D-2E, it should be understood that the second hollow tube 48 could be arranged similarly.
FIGS. 3A-3C illustrate an example artificial tibial component 26 from a superior-perspective view. In this example, the base plate 32 of the tibial component 26 includes a rim 68 extending around a perimeter and establishing a pocket 70 therein. The pocket 70 receives a portion of the spacer 30. In this example, the pocket 70 includes first and second threaded openings 72, 74. The first and second threaded openings 72, 74 are configured to receive first and second threaded plugs 76, 78, which are configured to expand respective first and second hollow tubes 80, 82 (FIG. 3C) aligned with the first and second threaded openings 72, 74, as will be discussed below. While reference is made to “threaded” openings and plugs, this disclosure extends to non-threaded arrangements. Further, while two sets of openings, plugs, and tubes are illustrated, this disclosure extends to artificial tibial components with one or more of such sets. Additionally, while the artificial tibial component 26 is shown having expandable hollow tubes, the artificial femoral component 22 could also include expandable hollow tubes. While the hollow tube may be expandable in an embodiment, in another embodiment the hollow tubes are not expandable.
In this example, an inferior surface 84 of the tibial component 26 is substantially covered by a layer 86 of bone ingrowth material. The bone ingrowth material may be the same type of bone ingrowth material as described above relative to the artificial femoral component 22, and may be applied in the same way. Further, the first and second hollow tubes 80, 82 are also provided with bone ingrowth material on a solid backing, or are alternatively provided entirely by bone ingrowth material, as in the examples of FIGS. 2D and 2E, respectively.
In this example, the first and second hollow tubes 80, 82 are provided along first and second axes A3, A4. The first and second axes A3, A4 are substantially perpendicular to the inferior surface 84 of the tibial component 26. The first and second hollow tubes 80, 82 project in the inferior direction from the inferior surface 84 by a length L3.
The first and second hollow tubes 80, 82 in this example are provided with one or more slits 88, 90 along substantially the entire length L3 of the first and second hollow tubes 80, 82. The slits 88, 90 allow expansion of the first and second hollow tubes 80, 82 in the radially outward directions R1, R2 relative to the respective axes A3, A4.
In one example, the first and second hollow tubes 80, 82 are selectively expandable in the radially outward directions R1, R2 upon insertion of the first and second plugs 76, 78 into the first and second threaded openings 72, 74. Expansion of the first and second hollow tubes 80, 82 in the radially outward directions R1, R2 increases the friction between the first and second hollow tubes 80, 82 and the corresponding tibial bone, which increases stability of the artificial tibial component 26.
FIG. 4A is a cross-sectional view taken along line 4A-4A from FIG. 3A. FIG. 4A illustrates the detail of the first threaded opening 72 and the first hollow tube 80. In this example, the first threaded opening 72 includes a threaded portion 92 having a first diameter D1 adjacent the pocket 70. The diameter of the first threaded opening 72 gradually tapers down to a second diameter D2, which is less than the first diameter D1. The threaded portion 92 terminates at a point inferior to (i.e., beneath) the inferior surface 84 and within the interior of the first hollow tube 80, in this example.
With reference to FIG. 5, an example method 110 of installing the artificial tibial component 22 is described. In the method 110, openings are formed in a bone, such as a tibial bone, at 112. Next, the first and second hollow tubes 80, 82 are received in those openings, at 114. Finally, the first and second hollow tubes 80, 82, are expanded, at 116. In one example, the first and second hollow tubes 80, 82 are expanded as the first and second threaded plugs 76, 78 are inserted into openings 72, 74.
Specifically, with reference to FIG. 4B, the first threaded plug 76 is inserted into the first threaded opening 72 by way of a driver, for example. In this example, the first threaded plug 76 is inserted in a first insertion direction I1, from the superior side of the artificial tibial component 22 toward the inferior side of the artificial tibial component 22. The first threaded plug 76 is sized such that its outer diameter substantially corresponds to the first diameter D1. As the first threaded plug 76 moves toward the second diameter D2 of the first threaded opening 72, the first threaded plug 76 expands the first hollow tube 80 in the radially outward direction R1 relative to the first axis A3.
FIGS. 4C and 4D illustrate alternative plug configurations. FIG. 4C illustrates a second type of plug 94 having a threaded portion 96 similar to the first plug 76. Distal of the threaded portion 96, the plug 94 includes a flared portion 98. The flared portion 98 tapers from a maximum dimension at the distal end 100 of the plug 94 to the threaded portion 96. In this example, the plug 94 may be inserted in a second direction I2 opposite direction I1. The flared portion 98 is sized to abut the interior of the first hollow tube 80 and expand the first hollow tube 80 in the radially outward direction R1.
With reference to FIG. 4D, a third type of plug 102 includes a first threaded portion 104 sized similarly to the threads of the first threaded plug 76. The plug 102 further includes a shank portion 106 configured to project beyond the inferior end of the first hollow tube 80 and including a second threaded portion 108 for engaging bone. The shank portion 106 has an outer dimension smaller than the first threaded portion 104. The first threaded portion 104 serves to expand the first hollow tube 80 in substantially the same way as the plug 76, while the second threaded portion 108 provides additional fixation relative to the tibial bone.
It should be understood that terms such as “superior,” “inferior,” “anterior,” “posterior,” “medial,” “lateral,” etc., are used herein for purposes of explanation, and should not be considered otherwise limiting. Terms such as “generally,” “substantially,” and “about” are not intended to be boundaryless terms, and should be interpreted consistent with the way one skilled in the art would interpret those terms.
Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.
One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.

## Claims

1. An artificial knee, comprising:
an artificial femoral component including a hollow tube having bone ingrowth material;
an artificial tibial component including a hollow tube having bone ingrowth material, wherein the hollow tube of one of the artificial femoral component and the artificial tibial component is selectively expandable; and
a spacer located between the artificial femoral component and the artificial tibial component.

2. The artificial knee as recited in claim 1, wherein the artificial femoral component further comprises:
an anterior surface comprising an articulating surface relative to the spacer; and
a posterior surface substantially covered by bone ingrowth material, wherein the hollow tube of the artificial femoral component projects in a posterior direction from the posterior surface.

3. The artificial knee as recited in claim 2, wherein the artificial femoral component includes two hollow tubes, each of the hollow tubes of the artificial femoral component including bone ingrowth material.

4. The artificial knee as recited in claim 1, wherein the artificial tibial component further comprises:
an opening aligned with the hollow tube of the artificial tibial component; and
a plug receivable in the opening, wherein the plug is configured to engage an interior of the hollow tube to expand the hollow tube.

5. The artificial knee as recited in claim 4, wherein the opening and the plug are threaded.

6. The artificial knee as recited in claim 5, wherein the plug includes one of (1) a threaded shank projecting beyond the hollow tube and configured to engage bone, and (2) a flared portion distal of the threads and configured to engage the hollow tube.

7. The artificial knee as recited in claim 1, wherein the hollow tube of the artificial tibial component includes at least one slit along substantially the entire length thereof.