Dual mobility cup reverse shoulder prosthesis
A reverse shoulder prosthesis system is provided. The system can include a the convex surface of the glenosphere and the concave surface of the humeral socket. The convex surface, a humeral socket can have a concave surface, and a cup is positioned between cup can be moveable relative to the glenosphere and to the humeral socket.
1 . A reverse shoulder prosthesis system, the system comprising:
a baseplate having a coupling surface and an opposite mounting surface with a peripheral surface connecting the coupling surface and the mounting surface to define a thickness of the baseplate therebetween;
a glenosphere coupled to the baseplate, the glenosphere having a truncated spherical portion with a flat surface coupled to the coupling surface of the baseplate, the truncated spherical portion having an equator and a geometric center defined at the equator and located along a central axis of the glenosphere that is axially distanced from the mounting surface of the baseplate to define a total offset of the glenosphere, the truncated spherical portion including an exterior convex surface defining a radius from the geometric center of the glenosphere, the equator being disposed in a first plane and the flat surface being disposed in a second plane parallel to the first plane with each of the equator and the flat surface being centered about the central axis of the glenosphere with a perpendicular distance between the first and second planes defining a glenosphere center of rotation offset;
a humeral socket having an interior concave surface extending circumferentially about a central axis of the humeral socket and a peripheral edge extending circumferentially about the central axis of the socket, the peripheral edge being axially spaced from an intersection of the central axis of the socket and the interior concave surface to define a depth (D1) of the humeral socket; and
a cup positioned between the exterior convex surface of the glenosphere and the interior concave surface of the humeral socket, the cup being moveable relative to the glenosphere and to the humeral socket, the cup having a first cup surface and an opposing second cup surface defining a thickness of the cup therebetween, each of the first and second cup surfaces extending circumferentially about a central cup axis,
the first cup surface having a first radius (R1) along the central cup axis and forming an exterior convex surface of the cup in bearing engagement with the interior concave surface of the humeral socket,
the second cup surface having a second radius (R2) along the central cup axis and forming an interior concave surface of the cup in bearing contact engagement with the exterior convex surface of the glenosphere,
wherein a ratio of the depth (D1) of the humeral socket to the first radius (R1) of the first cup surface (D1:R1) is 0.45+40 percent.
2 . The system of claim 1 , further comprising a humeral stem coupled to the humeral socket, the humeral stem having an end surface engaged with the humeral socket, and a tip with a neck extending axially between the end surface and the tip,
wherein the cup articulates with respect to both the glenosphere and the humeral socket to define a total abduction range of motion of the system (ROM) between the tip and the baseplate that includes a ratio of humerus range of motion to scapula range of motion (ROM2:ROM1), wherein said ratio ROM2:ROM1 is 2:1±20 percent.
3 . The system of claim 1 , wherein the humeral socket is configured to be coupled to a humeral stem of a shoulder prosthesis system that has failed.
4 . The system of claim 1 , wherein the first radius (R1) is smaller than the second radius (R2).
5 . The system of claim 1 , wherein the flat surface of the truncated spherical portion of the glenosphere defines a diameter about the central axis of the glenosphere, the baseplate having a maximum width equal to the diameter of the truncated spherical portion, the baseplate being coupled to the truncated spherical portion such that the peripheral surface of the baseplate extends parallel to the central cup axis,
wherein the cup has a flange that extends circumferentially around a peripheral edge of the cup, the flange extending radially away from a central axis of the cup,
wherein at a maximum abduction position defining a humeral range of motion limit of the system, the peripheral edge of the cup contacts the peripheral surface of the baseplate and the flange situates the peripheral edge of the socket away from and out of contact with the baseplate.
6 . The system of claim 5 , wherein a gap is defined between a surface of the flange and an edge of the humeral socket, and
wherein as the humeral socket rotates in a first rotational direction, the gap is minimized until the edge of the humeral socket contacts the surface of the flange.
7 . The system of claim 6 , wherein the cup is configured such that when the edge of the humeral socket contacts the surface of the flange, further rotation of the humeral socket in the first rotational direction causes the cup to rotate in the first rotational direction relative to the glenosphere.
8 . The system of claim 5 , wherein the flange includes an exterior concave surface that extends circumferentially around the cup,
wherein the peripheral edge of the humeral socket defines an arcuate lip having an arcuate convex surface that extends circumferentially about the central axis of the humeral socket, and
wherein at the maximum abduction position defining the humeral range of motion limit of the system, the arcuate convex surface of the arcuate lip is seated at the exterior concave surface of the flange to have an exterior surface of the humeral socket be flush and aligned with an exterior surface of the flange.
9 . The system of claim 1 , wherein the humeral socket is configured to rotate together with the cup, and is configured to rotate relative to the cup.
10 . The system of claim 1 , wherein the opposing first and second surfaces of the cup are non-concentric,
wherein the thickness of the cup varies based on an offset between the opposing first and second cup surfaces, and
an axial distance from the mounting surface of the baseplate and the truncated spherical portion define a center of rotation offset shift.
11 . The system of claim 1 , wherein the glenosphere includes a stem positioned at an end of the glenosphere, and a bore directed through the stem, and
wherein the baseplate is sized to nest within the bore of the glenosphere.
12 . The system of claim 11 , wherein the stem is integrally formed with the glenosphere.
13 . The system of claim 1 , wherein the cup is snap-fitted onto the glenosphere.
14 . The system of claim 1 , wherein the flat surface of the truncated spherical portion of the glenosphere defines a diameter about the central axis of the glenosphere, the baseplate having a maximum width equal to the diameter of the truncated spherical portion, the baseplate being coupled to the truncated spherical portion such that the peripheral surface of the baseplate extends parallel to the central cup axis,
wherein the second cup surface and the first cup surface form a peripheral edge of the cup therebetween that extends circumferentially about the central cup axis to define an entrance plane of the cup, and
wherein at a maximum abduction position defining a humeral range of motion limit of the system, each of the peripheral edge of the cup and the peripheral edge of the humeral socket contacts the peripheral surface of the baseplate.
15 . The system of claim 1 , wherein the glenosphere center of rotation offset is between 20% and 70% from the geometric center of the glenosphere.
16 . The system of claim 15 , wherein the glenosphere center of rotation offset is 25% of the radius from the geometric center of the glenosphere.
17 . The system of claim 15 , wherein the glenosphere center of rotation offset is 55% of the radius from the geometric center of the glenosphere.
18 . The system of claim 1 , wherein the baseplate includes holes through the thickness of the baseplate to accommodate fasteners through the coupling surface and the mounting surface.
19 . The system of claim 18 , wherein the holes include a centrally located hole and a plurality of holes radially spaced from the centrally located hole.
20 . The system of claim 18 , wherein the holes extend through the thickness of the baseplate non-perpendicularly relative to the mounting surface.
21 . The system of claim 1 , wherein at a maximum abduction position defining a humeral range of motion limit of the system, the cup maintains contact with the glenosphere and the peripheral surface of the baseplate.
22 . The system of claim 1 , wherein the bearing contact engagement between the first cup surface and the interior concave surface of the from the geometric center socket enables more freedom of movement than that enabled by the bearing contact engagement between the second cup surface and the exterior convex surface of the glenosphere.
23 . The system of claim 1 , wherein the baseplate is fully exteriorly located relative to the glenosphere.