Shock-absorbing implant for use in shoulder arthroplasty

Abstract

A shock-absorbing implant for use in shoulder arthroplasty has a bearing surface, a mounting base affixed to or formed with the bearing surface, a convex element extending outwardly of the mounting base opposite the bearing surface, a receptacle positioned so as to slidably or pivotably receive a portion of the convex element therein, a housing receiving at least a portion of the receptacle therein, and a resilient element received in the housing and bearing against a surface of the housing and against a surface of the receptacle. The bearing surface can be concave when the implant is used as a glenoid implant. The bearing surface can be convex when the implant is used as a humeral head implant.

Claims

1. A shock-absorbing implant for use in shoulder arthroplasty, the shock-absorbing implant comprising: a bearing surface; a mounting base affixed to or formed with said bearing surface; a convex element extending outwardly of said mounting base opposite said bearing surface; a receptacle positioned so as to slidably or pivotably receive a portion of said convex element opposite said mounting base; a housing receiving at least a portion of said receptacle therein, said housing having a surface thereon; and a resilient element received in said housing and bearing against said surface of said housing and against a surface of said receptacle so as to urge said receptacle toward said portion of said convex element.

2. The shock-absorbing implant of claim 1, said bearing surface having a concavity formed on a surface thereof opposite said mounting base.

3. The shock-absorbing implant of claim 1, said bearing surface having a convexity formed on or attached to a surface thereof that is opposite said mounting base.

4. The shock-absorbing implant of claim 1, further comprising: a beam ring interposed between said convex element in said receptacle, said beam ring extending radially outwardly of said convex element.

5. The shock-absorbing implant of claim 4, said beam ring comprising: a central ring; and a plurality of arms extending radially outwardly of said central ring, said plurality of arms bearing against a side of said mounting base opposite said bearing surface.

6. The shock-absorbing implant of claim 5, each of said plurality of arms reducing in width from said central ring toward an outer end of the arm.

7. The shock-absorbing implant claim 5, each of said plurality of arms reducing in thickness from said central ring toward an outer end of the arm.

8. The shock-absorbing implant of claim 5, said central ring having an opening in an interior thereof, said convex element extending through said opening.

9. The shock-absorbing implant of claim 1, said receptacle having a first portion and a second portion, said first portion having a concavity formed therein, said concavity receiving the portion of said convex element therein.

10. The shock-absorbing implant claim 9, said portion of said convex element having a convexity having a radius, said concavity of said first portion of said receptacle having a radius, the radius of said concavity being greater than the radius of said convexity.

11. The shock-absorbing implant of claim 9, said housing having a well formed therein, said well having a first portion and a second portion, said first portion having an inner diameter greater than an inner diameter of said second portion, said resilient element bearing against said first portion of said receptacle, said surface of said housing being a shoulder formed at a bottom of said first portion of said well of said housing.

12. The shock-absorbing implant of claim 11, said second portion of said receptacle received in said second portion of said housing.

13. The shock-absorbing implant of claim 9, said housing having a well formed therein, said well having a first portion of a second portion, said first portion having an inner diameter greater than an inner diameter of said second portion, said resilient element received in said second portion of said housing and bearing against said first portion of said receptacle.

14. The shock-absorbing implant of claim 1, said housing comprising: a first housing element; and a second housing element affixed to said first housing element, said second housing element retaining said receptacle within said first housing element, said convex element extending through a wall of said second housing element so as to fit against a concave surface of said receptacle.

15. The shock-absorbing implant of claim 1, said convex element comprising: a partially spherical element; and a stem extending outwardly of said partially spherical element, said stem having an end opposite said partially spherical element that is affixed to said mounting base.

16. The shock-absorbing implant of claim 15, said convex element having a junction portion between said partially spherical element and said stem, said junction portion having a diameter less than a maximum diameter of said stem.

17. The shock-absorbing implant of claim 4, further comprising: a plurality of fasteners affixing said mounting base to said beam ring.

18. The shock-absorbing implant claim 1, said resilient element being a spring.

19. A shock-absorbing glenoid implant comprising: a concave bearing surface; a mounting base affixed to or formed with said concave bearing surface; a convex element extending outwardly of said mounting base opposite said concave bearing surface; a receptacle positioned so as to slidably or pivotably receive a portion of said convex element therein opposite said mounting base; a housing receiving at least a portion of said receptacle therein, said housing having a surface thereon; and a resilient element received in said housing and bearing against said surface of said housing and against a surface of said receptacle so as to urge said receptacle toward said portion of said convex element.

20. A shock-absorbing humeral head implant comprising: a convex bearing surface; a mounting base affixed to or formed with said convex bearing surface; a convex element extending outwardly of said mounting base opposite said convex bearing surface; a receptacle positioned so as to slidably or pivotably receive a portion of said convex element therein opposite said mounting base; a housing receiving at least a portion of said receptacle therein, said housing having a surface thereon; and a resilient element received in said housing and bearing against said surface of said housing and against a surface of said receptacle so as to urge said receptacle toward said portion of said convex element.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 is a side elevational view of the shock-absorbing implant in accordance with the preferred embodiment of the present invention.

(2) FIG. 2 is a cross-sectional view of the shock-absorbing implant of the preferred embodiment the present invention.

(3) FIG. 3 is an exploded view of the shock-absorbing implant of the present invention.

(4) FIG. 4 is an upper perspective view showing the beam ring as used in the shock absorbing implant of the present invention.

(5) FIG. 5 is a cross-sectional view of an alternative embodiment of the shock-absorbing implant of the present invention.

(6) FIG. 6 is an exploded view of the alternative embodiment of the shock-absorbing implant of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) Referring to FIG. 1, there is shown the shock-absorbing implant in accordance with the preferred embodiment of the present invention. In particular, the shock-absorbing implant 10 is configured as a glenoid implant. The shock-absorbing implant 10 includes a bearing surface 12, a mounting base 14 affixed to or formed with the bearing surface 12, a beam ring 16 secured to the underside of the mounting base 14 opposite the bearing surface 12, and a housing 18 positioned below the beam ring 16. As will be described hereinafter, the mounting base 14 will support a convex element such that the convex element extends downwardly. The receptacle is positioned within the housing 18 so as to slidably or pivotally receive a portion of the convex element thereon.

(8) In FIG. 1, the bearing surface 12 can have an outer surface 20 that serves to bear against the humeral head (or the humeral head implant). The outer surface 12 can be a polymeric or elastomeric material, such as TEFLON. As such, the humeral head or the humeral head implant can bear against the surface 20 in a natural and conventional manner. The bearing surface 12 has a side 22 extending outwardly of the surface 20. As such, the side 22 provides support for the surface 20. The mounting base 14 is affixed to the bearing surface 12 at the side opposite to surface 20. As such, the mounting base 14 can provide strong structural support for the bearing surface 12. The beam ring 16 includes a central ring 24 with a plurality of arms 26, 28 and 30 radiating outwardly therefrom. As such, the central ring 24 will be interposed between the housing 18 and the mounting base 14. The arms 26, 28 and 30 radiate outwardly so as to provide support for the outer periphery of the mounting base 14 and the attached bearing surface 12. The housing 14 includes a first housing element 32 and a second housing element 34. These housing elements 32 and 34 are fitted together, adhesively secured together, or screwed together, so as to enclose the receptacle and the convex element therein as will be described hereinafter.

(9) FIG. 2 shows a cross-sectional view of the shock-absorbing implant 10. In particular, it can be seen that the bearing surface 12 includes a concavity 40 therein. As stated hereinbefore, this concavity will conform to the humeral head or to the humeral head implant. The mounting base 14 is secured to the side of the bearing surface 12 opposite the concavity 40. It can be seen that there is a convex element 42 that includes a partially spherical element 44 and a stem 46. There is a junction 48 between this partially spherical surface 44 and the stem 46. The junction 48 has a diameter that is less than the maximum diameter of either the stem 46 or the partially spherical element 44. The stem 46 of the convex element 42 is affixed within a receptacle 50 formed into the mounting base 14. As a result, the convex element 42 will extend outwardly from the mounting base 14 opposite to the bearing surface 12.

(10) A receptacle 52 is provided so as to have a concave surface 54 thereon. As can be seen, the partially spherical element 44 of convex element 42 resides within the concavity 54. Concavity 54 allows the convex element 42 to pivot therein and/or to slidably move therein.

(11) The receptacle 52 includes a first portion 56 and a second portion 58. The second portion 58 extends from the first portion 56 in a direction away from the convex element 42. A resilient member 60 is positioned within the housing 18 so as to bear against the first portion 56. The resilient element 60 is in the nature of a spring that can wrap around an annular portion 62 of the receptacle 52. The resilient element 60 will urge the receptacle 52 in a direction toward the convex element 42 such that the partially spherical element 44 of convex element 42 will bear against the surface of the concavity 54.

(12) In FIG. 2, the housing 18 includes a first portion 32 and a second portion 34. The second portion 34 is fitted over the first portion 32 so as to enclose the receptacle 52 within the first portion of housing 18. Suitable fasteners 66 and 68 can be used so as to secure the beam ring 16 to the mounting base 14.

(13) FIG. 3 is an exploded view of the shock-absorbing implant of the present invention. In particular, FIG. 3 shows the bearing surface 12, the mounting base 14, the beam ring 16, the convex element 42, the receptacle 52, the first housing element 32, the second housing element 34, and the resilient element 60.

(14) The bearing surface 12 includes a protrusion 70 that is adapted to be snap-fit within a receptacle 72 formed on the adjacent surface of the mounting base 14. Alternatively, and within the concept of the present invention, the mounting base 14 can be directly formed with or integrally attached to the bearing surface 12. As such, the bearing surface 12 is securely fixed to the mounting base 14.

(15) The mounting base 14 includes holes 74 and 76 therethrough. Holes 74 and 76 are configured so as to allow respective fasteners 78 and 80 to extend through the holes 74 and 76 so as to be fitted within the respective holes 82 and 84 of the beam ring 16. Additionally, the ends of the fastener 78 and 80 can threadedly engaged with holes 86 and 88 of the second housing element 34. In this manner, the beam ring 16 can be securely sandwiched between the mounting base 14 and the second housing element 34.

(16) FIG. 3 shows that there is an opening 90 formed on a side of the mounting base 14 opposite the bearing surface 12. This opening 90 will serve to receive the stem 46 of the convex element 42. The stem 46 can extend through an opening 92 in the beam ring 16 such so as to fix the position of the convex element 42 therein. The junction portion of the convex element 42 can be in snap-fit relationship with the sides of the opening 92 of beam ring 16.

(17) The partially spherical element 44 of the convex element 42 will extend through a hole formed in the top surface of the second housing element 34 so as to extend downwardly and fit within the concavity 54 of the receptacle 52. The resilient element 60 is adapted so as to bear against the surface 56 of the receptacle 52 and against a surface 96 of the first housing element 32. The receptacle 52 also includes a second portion 98 that is adapted to be received within a second portion 100 of a well 102 formed in the interior of the first housing element 32. As such, the second portion 98 of the receptacle 52 can securely nest within the well 102 of the housing 18. In this manner, the resilient element 60 can resiliently bear against the receptacle 52 in a secure manner.

(18) FIG. 4 is an isolated view of the beam ring 16. The beam ring 16 includes a central ring 106 having a hole 108 formed centrally thereof. A plurality of arms 26, 28, 30 and 110 radiate outwardly in circumferentially spaced relationship from the central ring 106. Bolt holes 82, 84, 112 and 114 are formed through the thickness of the central ring 106.

(19) Importantly, in FIG. 4, it can be seen that each of the arms 26, 28, 30 and 110 has a width that decreases from the central ring 106 to an opposite end of each of the arms. Similarly, each of the arms 26, 28, 30 and 110 has a thickness that decreases from the central ring 106 to the outer end of each of the arms. As such, each of the arms is configured to have greater flexibility at the periphery of the beam ring 16 than adjacent to the central portion of the beam ring.

(20) Importantly, the present invention offers unique advantages as a shock-absorbing implant. In particular, a rotation of the convex element 42 with respect to the concavity 54 is allowed. Additionally, since the concavity 54 has a radius that is greater than the radius of the convexity of the convex element 42, a gliding effect is also allowed, along with a small translation relative to these elements. It should be noted that the convex element 42 can swing from side-to-side within the concavity 54 and also slide from side-to-side within the concavity 54. However, because of the large radius of the concavity 54 and the upward turned ends of the concavity 54, greater resistance is afforded to the sliding of the convex element 42 as it reaches the outer edges of the concavity. As such, this effectively restricts the movement of the convex element 42.

(21) If any impact were to occur to the surface 20 of the bearing surface 12, the shock-absorbing implant 10 of the present invention is able to diffuse such an impact by having small displacements on several elements. In particular, the arms 26, 28, 30 and 110 of the beam ring 16 will flex individually and/or at the same time. The gliding joint mechanism provided between the convex element 42 and the concavity 54 of receptacle 52 will redirect the impact toward a single degree of freedom (i.e. translation along a single axis). Additionally, and furthermore, the resilient element 60 (i.e. a spring) will collect the impact energy and restore the system to the original position afterward.

(22) If a shearing action is applied to the implant 10, then the present invention includes built-in security in order to secure the preservation of the bone to which the implant is attached. In particular, the gliding joint mechanism provided between the convex element 42 and the concavity 54 of receptacle 52 has a reduced cross-sectional area at the element connecting the base plate to the mechanism. This reduction of areas intended to break under shear. This maximizes the potential for bone preservation. Additionally, each or any of the beams 26, 28, 30 and 110 could also bend or break in order to avoid damage to the connected bone. In the event that any of the elements associated with the implant 10 were to fail, the replacement would not compromise the bone that is used to fixate the system.

(23) It should be noted that the clearance provided between the bottom of the surface 56 of receptacle 52 and the shoulder 96 of the housing 18 allows for a single axis translational motion of the spring. This clearance could be filled with an elastomer, a silicone, or similar materials, in order to enhance the shock-absorption capabilities of the system. This clearance could also be used so as to allow for a fluid to fill it so as to provide a natural damper. The filling liquid could be blood, synovial fluid, or a combination of both.

(24) In the embodiment shown in FIGS. 1-3, the shock-absorbing implant 10 is intended for use as a glenoid implant. In order to properly secure the glenoid implant, the housing 18 can be properly secured by nails or screws within the bone tissue provided at the glenoid. As such, the surface 20 of the bearing surface 12 can face outwardly in the direction toward the humeral head. In certain circumstances, it may be desirable to use the shock-absorbing implant of the present invention in association with such a humeral head. FIGS. 5 and 6 illustrate such a configuration.

(25) In FIG. 5, there shown the shock-absorbing implant 200 in accordance with the teachings of the present invention. Shock-absorbing implant 200 has a configuration similar to that shown in the previous embodiment except for the fact that the bearing surface 12 is actually a convex surface 202. Convex surface 202 will mimic the surface of the humeral head. As such, there is a smooth contoured surface 202 that can bear against the glenoid or the glenoid implant. A mounting base 204 is secured to the convex bearing surface 202 in the manner described herein previously. A beam ring 206 is affixed to the surface of the mounting base 204 opposite the convex bearing surface 202. The convex element 208 is secured so as to extend to a receptacle 210. Receptacle 210 is received within a housing 212.

(26) Unlike the previous embodiment of the present invention, it can be seen that the receptacle 210 includes a first portion 214 and a second portion 216. The resilient element 218 is received in the well 220 of the housing 212 so as to extend around the second portion 216 and to bear against the first portion 214. In contrast to the previous embodiment, it can be seen that the spring 218 is received within the smaller inner diameter portion of the well 220 rather than in the larger inner diameter portion of the well. Within the concept of the shock-absorbing implant 200, as shown in FIG. 5, it is also possible that the configuration of spring and surfaces of the receptacle could be similar to that shown in the previous embodiment.

(27) FIG. 6 illustrates an exploded view of the shock-absorbing humeral head implant 200 in accordance with this alternative embodiment of the present invention. In particular, it can be seen that the convex bearing surface 202 can be affixed to the mounting plate 204 by virtue of the protrusion 206 that is received within the receptacle 208 formed on the mounting base 204. Fasteners 210 extend through the mounting base 204 and through holes in the beam ring 212 so as to engage with the second housing element 214. The convex element 216 is affixed within the opening 218 of the mounting base 204, extends through the beam ring 212, and has a convex surface bearing against a concavity 220 of the receptacle 222. The first housing element 224 receives the spring 226 within a lower well 228 such that the spring 226 can bear against the shoulder of the receptacle 222. The second housing element 214 can be fitted over the male end of the first housing element 224 so as to enclose the receptacle 220 and the spring 226 therein.

(28) In the embodiments of FIGS. 5 and 6, the housing 220 can be affixed, in a conventional fashion, at the humeral head of a humerus. As such, the convex bearing surface 202 can extend outwardly at a conventional angle toward the glenoid. The humeral head implant 200 can be used in conjunction with an existing glenoid or with the shock-absorbing glenoid implant 10 of FIGS. 1-3.

(29) Within the present invention, is important to note that the bearing surface of the shock-absorbing implant can be easily exchanged. If it is desired to be used as a glenoid implant, then the bearing surface 12 of FIGS. 1-3 can be used. Alternatively, if the shock-absorbing implant is intended as a humeral head implant, then the convex bearing surface 202 of FIGS. 5 and 6 can be utilized. As such, it is easy to adapt the shock-absorbing implant for different purposes. The present invention can also be used as a regular shoulder joint replacement or as a reverse shoulder joint replacement. The entire shock-absorbing system is intended to be positioned as near as possible to the joint. However, it should not be limited to this since it can be actuated by other methods as well.

(30) The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made within the scope of the present claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.