Patent Description:
It is not uncommon for the exterior surface of the humeral head to be damaged or defective. Conventionally, a variety of humeral head resurfacing implants exist for repairing humeral head surfaces. While conventional humeral head resurfacing implants are suitable for their intended uses, such implants are subject to improvement.

Conventional humeral implants fail to accommodate patients having inadequate skeletal structure during an impact situation. Specifically, conventional implants do not permit relative movement between the components or the absorption of impact energy. These impacts are often off axis and have complex loading parameters.

To overcome these deficiencies, reverse shoulders using a glenosphere have been used. These reverse shoulders may be susceptible to impacts when a patient inadvertently falls, impacting the prosthetic. Thus, there is a need for a humeral implant that permits proper articulation dynamics, while accepting impact loads.

<CIT> discloses a hip prosthesis including a femoral implant and a socket implant. The femoral implant is configured to be implanted into a resected femur and further comprises a ball surface as well as an opposed bearing mounting surface. An annular spring member is disposed between the femoral implant and the femoral head member. The annular spring member functions to absorb impacts or forces applied to the femoral head member.

<CIT> discloses inverse prosthesis of the shoulder for the articulation of a humerus in a scapula of a shoulder comprising a glenoid cavity. The prosthesis includes an at least partly convex articulation element, including elements for support and attachment to the glenoid cavity, and able to articulate with an at least partly concave mating articulation element, associated with the top of the humerus.

Various aspects of the teachings provide a modular humeral implant and associated kit and method for implantation into a shoulder joint that includes a natural humeral shaft and a natural humeral head and glenoid. The present invention provides a shoulder prosthetic, as defined in claim <NUM>. Further optional features of the invention are defined in the dependent claims. Methods are described herein but the methods are not claimed.

A modular reverse shoulder prosthetic is taught. The reverse shoulder prosthetic can have a glenoid tray configured to be implanted into a resected glenoid. The tray can have an opposed bearing mounting surface defining a coupling taper therein. A bearing coupling member is provided which is configured to engage the bearing mounting surface. A depending spring member is provided that is configured to be disposed radially about the bearing coupling member. The spring is coupled to a glenosphere bearing and the tray or the coupling member.

According to alternate teachings, the shoulder prosthetic can have a glenoid tray configured to be implanted into the resected glenoid. The tray can have a glenoid interface surface with a depending coupling stem and an opposed bearing mounting surface. The bearing mounting surface defines a coupling aperture having a coupling taper. A spring member is first disposed within a cavity defined by the glenoid tray, and is coupled to a glenosphere and defines an aperture which can annularly accept a bearing coupling member. The bearing coupling member is disposed within the spring member aperture.

According to alternate teachings, the glenoid tray can define a glenoid tray spring coupling ledge configured to annularly support the spring member when the bearing coupling member is engaged with the spring and the glenoid tray. The glenosphere head member is translatable with respect to the bearing coupling member.

<FIG> represents a cross-sectional view of the shoulder system <NUM> not forming part of the present invention. The system <NUM> utilizes the glenoid coupling member or glenoid tray <NUM> to couple a shoulder bearing <NUM> to the prepared glenoid. Disposed within the glenoid tray <NUM> is the shoulder bearing <NUM> having a mounting interface surface <NUM> and concave bearing surface <NUM>. The concave bearing surface <NUM> is configured to interface with the articulating surface of a humeral prosthetic <NUM>. The mounting interface surface <NUM> can have an intermediate depending piston <NUM>. The intermediate depending piston <NUM> can be fixed to mounting interface surface <NUM> or, as described below, to the glenoid tray <NUM>.

Operably disposed between the shoulder bearing <NUM> and the glenoid tray <NUM> is an annular spring member <NUM>. The spring member <NUM> functions to couple the bearing <NUM> to the glenoid tray <NUM>. In this regard, the spring member <NUM> functions to limit or constrain movement of the shoulder bearing <NUM> with respect to the glenoid tray <NUM>. Additionally, the spring member <NUM> functions to absorb impacts or forces applied onto the bearing surface <NUM>. The annular spring member <NUM> has a first end fixably coupled to an aperture <NUM> formed within the glenoid tray <NUM>. At its second end, the spring member <NUM> is fixably coupled to an aperture <NUM> formed on the interface side of the bearing <NUM>.

It is envisioned the intermediate depending piston <NUM> fixed to the mounting interface surface <NUM> can be slidably accepted by the cylindrical aperture <NUM> defined within the glenoid tray <NUM>. The intermediate depending piston <NUM> and cylindrical aperture <NUM> can be sized and toleranced so that the interface between the intermediate depending piston <NUM> and aperture <NUM> functions as a fluid damper. The aperture <NUM> can be formed in a tray coupling stem <NUM>.

The coiled spring member <NUM> can define a central through bore <NUM> which annularly surrounds the intermediate depending piston <NUM>. It is envisioned that the spring member <NUM> can be positioned within a cavity defined by a fixation edge <NUM> of the glenoid tray <NUM>. Alternatively, the spring member <NUM> may be incorporated into a cavity (not shown) defined by the bearing <NUM> mounting interface surface <NUM>. In addition, the spring member <NUM> may be sized and configured to be located within the cylindrical aperture <NUM> in order to impart force upon the intermediate depending piston <NUM>.

As shown in <FIG>, a glenosphere head <NUM> is coupled to the glenoid tray <NUM> using a bearing coupling member or intermediary coupling member <NUM>. Disposed about the intermediary coupling member <NUM> is a spring member <NUM>, which is coupled between the intermediary coupling member <NUM> and the head <NUM>. The coupling member <NUM> is non-rotatably, but floatably disposed within the glenoid tray <NUM> using the coupling taper <NUM>. In this regard, the coupling taper <NUM> is inserted into a bore defined within the glenoid tray or support structure <NUM>.

The head <NUM> is configured to be coupled to a cup member bearing <NUM> fixed to the stem <NUM>. As further described below, the head <NUM> is coupled directly to the glenoid tray <NUM> or to the glenoid tray <NUM> through the intermediary coupling member <NUM> using the spring member <NUM>. The spring member <NUM> is fixably or rotatably coupled to the head <NUM> and the intermediary coupling member <NUM>. The taper <NUM> is configured to loosely couple to a taper in the head <NUM>. In this regard, the taper <NUM> can be a non-locking taper.

<FIG> represents an exploded cross-sectional view of shoulder components not forming part of the present invention. <FIG> depicts the components shown in <FIG>. As shown, the spring coupling apertures defined by the bearing <NUM> or the glenoid tray <NUM> can be generally parallel to the interface surfaces of both the bearing <NUM> and the glenoid tray <NUM>.

<FIG> represent reverse shoulder components having an intermediary coupling member <NUM> according to the present invention. The intermediary coupling member <NUM> has a head bearing surface <NUM> which is translationally coupled to a corresponding surface <NUM> defined within the head. The head bearing surface <NUM> is configured to transfer applied loads onto the head bearing surface <NUM> through the coupling member <NUM> and into the glenoid tray <NUM>. The head bearing surface <NUM> can be a non-locking taper <NUM> or a spherical bearing surface <NUM>.

The spring coupling member <NUM> has an exterior surface <NUM> having a generally fixed radius of curvature about the centerline defining the coupling member <NUM>. The spring coupling member <NUM> generally can present one and a half rotations which has a cross-sectional area smaller than the cross-sectional area of the head. As shown in <FIG>, the ledge portion <NUM> of the head <NUM> is configured to annularly enclose the spring member <NUM>.

<FIG> represent cross-sectional views of the implantation of the shoulder components shown in <FIG>. After the resection of the glenoid, an aperture <NUM> can be formed within the glenoid to accept a tray coupling stem <NUM>. After coupling the glenoid tray <NUM> to the resected glenoid, the spring member <NUM> can be coupled to the glenoid tray <NUM> or the coupling member <NUM>.

After coupling the spring member <NUM> to the glenoid tray <NUM> or the coupling member <NUM>, the coupling member <NUM> (if used) can be coupled to a coupling taper defined in the glenoid tray <NUM>. The second end <NUM> of the spring member <NUM> can then be coupled into the spring coupling aperture <NUM> formed in the mating surface of the head <NUM>.

As shown in <FIG>, the glenoid tray <NUM> can be flexibly coupled to the head <NUM>. In this regard, the coupling member <NUM> can be fixably coupled to the head <NUM> by the coupling surface <NUM>. The coupling member <NUM> has a flat surface <NUM> which slidably interfaces with a planar interface surface <NUM>. The floating head <NUM> and coupling member <NUM> are movably fixed to the glenoid tray <NUM> through the spring member <NUM>. As with all of the examples, the head can be moveable with respect to the glenoid tray, the bearing coupling member, or a portion of the spring when the head is subjected to forces.

As seen in <FIG>, the head <NUM> can be coupled directly to the glenoid tray <NUM> using only the coupling spring member <NUM>. As described above, the coupling spring can be fixably coupled at the coupling apertures.

Claim 1:
A shoulder prosthetic comprising:
a glenosphere head member (<NUM>);
a glenoid coupling member (<NUM>) configured to be implanted into a resected glenoid, the glenoid coupling member having a glenoid interface surface and an opposed bearing mounting surface;
an annular spring member (<NUM>) disposed between the glenoid coupling member (<NUM>) and the glenosphere head member (<NUM>); and
an intermediary coupling member (<NUM>), the intermediary coupling member (<NUM>) configured to engage the bearing mounting surface, wherein the intermediary coupling member (<NUM>) is coupled to a coupling taper defined in the glenoid coupling member (<NUM>), wherein
the annular spring member is fixably or rotatably coupled to the glenosphere head member (<NUM>) and the intermediary coupling member (<NUM>) and the annular spring member functions to absorb impacts or forces applied to the glenosphere head member (<NUM>).