Patent Description:
The shoulder joint is a ball-and-socket-joint. A shoulder joint may be replaced or repaired if it suffers from chronic rotator cuff defect or other maladies, such as arthrosis or fracture. An inverse shoulder prosthesis may be configured to form a fixed center of rotation for the glenohumeral joint in order to restore the mobility of the shoulder if the glenohumeral joint can no longer be centered for pathological reasons. This can be the case with large defects of the rotator cuff. With inverse shoulder prostheses, the original biomechanics are reversed. Hence in contrary to an anatomical shoulder prosthesis, the joint ball, the glenosphere, may be placed on the glenoid side and the artificial prosthesis socket on the humeral head side. Thus, the glenosphere with its spherical joint head and the prosthetic socket may be rotating around the glenosphere, which represents a spherical hinge joint.

<CIT> discloses arthroplasty implants and methods for orienting joint prostheses.

<CIT> discloses an inverse shoulder prosthesis having an adapter anchored in the bone and a spherical hemisphere head, the glenosphere attached to it and a prosthesis socket with polyethylene (PE) inlay embedded in the upper arm shaft. The prosthesis socket and the associated PE inlay have an almost identical radius to the glenosphere. It may be fitting with a spherical glenosphere and identical concavity of the corresponding prosthesis cup (metaphyseal cup). It comprises a pure ball and socket joint that only allows rotation but no translation. Therefore, the patient is limited in the movement in the transverse plane, since the inverse shoulder prosthesis mechanically blocks further movement.

The problem to be solved by the invention is to provide an inverse shoulder prosthesis which can be easily implanted, and which improves the range of motion.

The dependent claims relate to further improvements of the invention.

The inverse shoulder prosthesis has a glenoid implant and a humerus implant. The glenoid implant includes a glenoid body which has a dome shaped articulating surface. A dome has a surface that curves in two directions, and which has a base. The articulating surface may have the shape of a half ellipsoid and preferably of a half three-axial ellipsoid. The base may be circular, it may have an ellipsoid shape, or it may have any other geometrical shape. A dome with a circular base may be known as circular dome. An embodiment relates to a non-circular dome. Opposing to the articulating surface the glenoid implant may include an attachment section. The attachment section may have protrusion which may further have a conical shape which may have a larger size oriented to the base of the dome. The attachment section may be one part with the dome or a separate part. An adapter may fit to the attachment section and may be configured to be mounted to a bone. The adapter may be cup shaped. It may further include a material with good ingrowth properties.

The articulating surface may define a first right hand Cartesian coordinate system with a first x-axis, a first y-axis, a first z-axis and a first point of origin. The first coordinate system may be a Cartesian coordinate system. The point of origin may be the point of the coordinate system where the axes of the coordinate system intersect. The articulating surface extends into the directions of the first x-axis, the first y-axis, and the direction of the first z-axis. The first z-axis may be the center axis of the glenoid body. With respect to a human body, the z-axis may be oriented towards the humerus, while the x-axis may be oriented in an anterior-posterior direction. The y-axis may be oriented in a lateral-medial direction. The articulating surface extends into the positive direction of the first z-axis, in positive and negative directions of the first x-axis, and in positive and negative directions of the first y-axis.

The glenoid body may have a half-spherical cross-sectional area in a plane defined by the first y-axis and the first z-axis. With respect to the human body, this plane may be the sagittal. The glenoid body may have a half-ellipsoidal cross-sectional area in a plane defined by the first x-axis and the first z-axis. With respect to the human body, this plane may be the frontal plane. The base of the dome may be located in a plane defined by the first x-axis and the first y-axis. With respect to the human body, this plane may be the transversal plane. The base of the dome may be largest along the y-axis.

The articulating surface may have at least one first radius located in a plane defined by the first z-axis and the first y-axis. The at least one first radius may be defined by the distance from the first point of origin to the articulating surface. In other words, the at least one first radius may be defined by the length of a straight line starting from the point of origin to the piercing point of the first articulating surface. An intersecting point may be the intersection of a straight line with a surface. The first z-axis and the first radius may form a first angle. Said first angle may be largest if z = <NUM> and smallest when y = <NUM>. Z = <NUM> may be the extension of the second radius along the y- axis. The first angle may be <NUM>° when y = <NUM> and <NUM>° when z = <NUM>. The first angle may have a range of <NUM>°. The first angle may have a range of at least <NUM>°. The first angle may be <NUM>° when y = <NUM> and <NUM>° or <NUM>° when z = <NUM>. The first angle may be <NUM>° when y =<NUM> and <NUM>° or at least <NUM>° when z = <NUM>. The at least one first radius may be constant. The distance from the point of origin to the articulating surface may stay the same in the plane defined by the first z-axis and the first y-axis.

The articulating surface may have at least one second radius located in a plane defined by the first z-axis and the first x-axis. The at least one second radius may be defined by the distance from the first point of origin to the articulating surface. The at least one second radius may be defined by the length of a straight line starting from the point of origin to the piercing point of the first articulating surface in a plane defined by the first z-axis and the first x-axis. The first z-axis and the at least one second radius may form a second angle. The second angle of the at least one second radius may be smallest if z = <NUM> and largest when x = <NUM>. Z = <NUM> may be the extension of the second radius along the x- axis. Said angle may be <NUM>° when x=<NUM> and <NUM>° when z = <NUM>. The second angle may have a range of <NUM>°. The second angle may have a range of at least <NUM>°. The second angle may be <NUM>° when x = <NUM> and <NUM>° or <NUM>° when z = <NUM>. The second angle may be <NUM>° when x = <NUM> and <NUM>° or at least <NUM>° when z = <NUM>. The at least one second radius may increase when the second angle approaches <NUM>°. If the second angle is <NUM>° the at least one second radius may be largest. If the second angle is <NUM>° the at least one second radius may correspond to the at least one first radius. If the second angle is <NUM>° the at least one second radius may correspond to extension of the glenoid body along the first z-axis. The distance from the point of origin to the articulating surface may increase along the articulating surface starting from the first x-axis towards the first z-axis.

The second radius at an angle of <NUM>° and <NUM>° or <NUM>° and at least <NUM>° may be smaller than the first radius at an angle of <NUM>° and <NUM>° or and at least <NUM>°. When z = <NUM>, the at least one second radius may be smaller than the at least one first radius. The extension of the at least one first radius along the x-axis may be smaller than the extension of the at least one second radius along the y-axis. In the direction of the first x-axis the extension of the at least one second radius may be in a range of <NUM> to <NUM> of the extension of the at least one first radius. The at least one second radius may be in a range of <NUM> to <NUM> times of the at least one first radius. In the direction of the first x-axis the extension of the second radius may be in a range of <NUM> - <NUM> of the extension of the first radius. The at least one second radius may be in a range of <NUM> to <NUM> times of the at least one first radius. Therefore, the extension of the glenoid body may be largest along the first y-axis and the extension along the first x-axis may be smaller than the extension along the first y-axis. The at least one first radius may correspond the extension of the glenoid body along the first z-axis. In other words, the at least one first radius and the extension of the glenoid body along the first z-axis may be the same. Since the articulating surface is the surface of the glenoid body, the at least one first radius and the at least one second radius of the articulating surface may be the first radius and second radius of the glenoid body.

The humerus implant has a humeral body and an inlay having a concave shape. The inlay having a concave shape may also be referred to as concave inlay. The humeral body may further include a prosthesis stem and/or a prosthesis cup. The inlay may be located inside the prosthesis cup. The inlay may be connected to the prosthesis cup by a loose or fixed connection. The prosthesis cup may be connected to the prosthesis stem by a loose or a fixed connection. The prosthesis cup and the prosthesis stem may be one part or separate parts. The concave inlay may have a second articulating surface, which may include a low friction material. It may include at least one of a polyethylene, polytetrafluorethylene. The concave inlay has a second coordinate system with a second x-axis, a second y-axis, a second z-axis and a second point of origin. The second coordinate system may be a Cartesian coordinate system. The concave inlay may extend into the directions of the second x-axis, the second y-axis, and the second z-axis. With respect to a human body, z-axis may be oriented towards the glenoid of a shoulder, while the x-axis may be oriented in an anterior-posterior direction. The y-axis may be oriented in a craniocaudally direction. The second z-axis may be the center axis of the inlay. The inlay may extend into a negative direction of the second z-axis. The inlay includes at least one inner radius. The center of origin of the at least one inner radius may be the point of origin of the second coordinate system. The at least one inner radius may extend from the second point of origin to the second articulating surface of the inlay. The inlay may have at least an inner first radius and a second inner radius. The first inner radius may be located in a plane defined by the second x-axis and the second z-axis. The second inner radius may be located in a plane defined by the second y-axis and the second z-axis. The second inner radius may be smaller than the first inner radius.

The glenoid body may be placed in the inlay. The glenoid implant may contact the humerus implant. The glenoid body may contact the inlay of the humerus implant. The first articulating surface may contact the second articulating surface. The convex glenoid body and the concave inlay may form a bearing. The first articulating surface and the second articulating surface may form a bearing. The humerus implant and the glenoid implant may move relative to each other. It may be a constrained joint in the x-axis (coronal plane).

The at least one second radius may be smaller than the at least one inner radius of the inlay. The at least one second radius may be smaller than the inner radii of the inlay. This may result in a mismatch of the radii of the articulating surface and the inlay in the x-z plane and hence may result in a gap between the first articulating surface and the second articulating surface in the x-z plane. The at least one second radius may be <NUM> -<NUM> smaller than the inner radius, preferably the at least one second radius may be <NUM> - <NUM> smaller than the inner radius. This may result in a mismatch of the radii may in a range of <NUM> - <NUM>, preferably in a range of <NUM> - <NUM>. There may be no mismatch of the first radius and the inner radius in the y-z plane. In an embodiment, the articulating surface may have a second radius of <NUM>,<NUM> in the z-x plane and the inlay may have a <NUM> radius which may result in a semi-constrained joint in the y-axis (sagittal plane). The mismatch may enable a translational movement of the humerus implant along the x-axes, resulting in a roll and glide movement of the inverse shoulder prosthesis. This mismatch may further enable an anatomically correct external and internal rotation of the inverse shoulder prosthesis. Furthermore, the mismatch may improve the axial rotation of the humerus implant. Due to the morphology of the glenoid body, a combined roll-slide mechanism may occur in the glenohumeral joint during rotation, while a roll-mechanism may occur during arm elevation due to the spherical shape of the glenoid body in the y-z plane.

The glenoid body may be made of metal. The metal may be an alloy. The metal may be stainless steel, a chrome-cobalt alloy, a titanium-based alloy or a nickel-titanium allay. Of course, any other material suitable for a glenoid implant may be also possible. The inlay may be made of plastic, such as polyethylene or polytetrafluorethylene. The glenoid body and the inlay may form a metal-polyethylene bearing coupling. The choice of material can also be changed so that the glenoid component can be made of plastic (and its derivatives) and the humeral inlay can be made of metal or its derivatives.

In <FIG> a cross sectional view of an embodiment of a glenoid implant <NUM> is shown. <FIG> shows a view of a glenoid implant <NUM> in the y<NUM>-z<NUM> plane of an embodiment. The glenoid implant <NUM> may include a glenoid body <NUM>, a first articulating surface <NUM>, an attachment section <NUM> and an adapter <NUM>. The glenoid body <NUM> may be convex. The first articulating surface <NUM> may be convex and dome shaped. The first articulating surface may have a first coordinate system (x<NUM>,y<NUM>,z<NUM>). The first coordinate system may have a first x-axis x<NUM> <NUM>, a first y-axis y<NUM> <NUM>, a first z-axis z<NUM> <NUM> and a first point of origin <NUM>. The first articulating surface <NUM> may extend into the directions of the first x-axis x<NUM> <NUM>, the first y-axis y<NUM> <NUM>, and the first z-axis z<NUM> <NUM>. The extension of the articulating surface <NUM> and therefore of the glenoid body <NUM> along the first y-axis y<NUM> <NUM> may be greater than the extension of the articulating surface <NUM> and therefore of the glenoid body <NUM> along the first x-axis x<NUM> <NUM>. The glenoid body may be convex and may extend along the positive direction of the first z-axis z<NUM> <NUM>. The first z-axis z<NUM> <NUM> may the center axis of the glenoid body <NUM>. The first z-axis z<NUM> <NUM> may the center axis of the articulating surface <NUM>. The first z-axis z<NUM> <NUM> may the center axis of the glenoid implant <NUM>. The articulating surface <NUM> may have at least one first radius <NUM>. The at least one first radius <NUM> may not vary in the z<NUM> - y<NUM> plane. A first angle <NUM> may be located between the first z-axis z<NUM> <NUM> and the least one first radius <NUM>. The first angle <NUM> may be <NUM>° when z<NUM> <NUM> = <NUM> and <NUM>° when y<NUM> <NUM> = <NUM>. The first angle <NUM> may have a range of <NUM>°. The first angle <NUM> may have a range of at least <NUM>°. The first angle <NUM> may be <NUM>° when y<NUM> <NUM> = <NUM> and <NUM>° or <NUM>° when z<NUM> <NUM> = <NUM>. The first angle <NUM> may be <NUM>° when y<NUM> <NUM> = <NUM> and <NUM>° or at least <NUM>° when z<NUM> <NUM> = <NUM>. The glenoid body <NUM> may have a half spherical shape in the z<NUM>- y<NUM> plane. The first articulating surface <NUM> may be the outer surface of the glenoid body <NUM>. The glenoid implant <NUM> may have an attachment section <NUM> in the negative direction of the z-axis z<NUM> <NUM>. The attachment section <NUM> may be connected to the glenoid body <NUM>. Opposing to the first articulating surface <NUM> may be an attachment section <NUM> and an adapter <NUM>. The attachment section <NUM> may be in a recess, for example a conical recess, adapted to hold the attachment section <NUM>. The attachment section <NUM> may be connected to the glenoid body <NUM> by a loose or a fixed connection. The attachment section and the glenoid body may be monolithic, the attachment section may be part of the glenoid body. The adapter <NUM> may be connected to the glenoid body <NUM> opposing to the first articulating surface <NUM>. The adapter <NUM> may be connected to the glenoid body <NUM> by a loose or a fixed connection.

<FIG> shows a cross sectional view of the glenoid implant <NUM> of the embodiment of <FIG> in the x<NUM>-z<NUM> plane. The glenoid implant <NUM> may include a glenoid body <NUM>, a first articulating surface <NUM>, an attachment section <NUM> and an adapter <NUM>. The first articulating surface 120may have at least one second radius <NUM> in the x<NUM>-z<NUM> plane. A second angle <NUM> may be located between the first z-axis z<NUM> <NUM> and the least one second radius <NUM>. The second angle <NUM> may be <NUM>° when z<NUM> = <NUM> and <NUM>° when x<NUM> <NUM> = <NUM>. The second angle <NUM> may have a range of <NUM>°. The second angle <NUM> may have a range of at least <NUM>°. The second angle <NUM> may be <NUM>° when x<NUM> <NUM> = <NUM> and <NUM>° or <NUM>° when z<NUM> = <NUM>. The second angle <NUM> may be <NUM>° when x<NUM> <NUM><NUM> and <NUM>° or at least <NUM>° when z<NUM> = <NUM>. The at least one second radius <NUM> may vary depending on the second angle <NUM>. The at least one second radius <NUM> may be smallest, when the second angle <NUM> is <NUM>° (<NUM><NUM>) and may be largest when the second angle <NUM> is <NUM>° (<NUM>n). When <NUM> is <NUM>°, the at least one second radius <NUM> may correspond to the at least one first radius <NUM>. In other words, when <NUM> is <NUM>° the at least one second radius <NUM> and the at least one first radius <NUM> may be the same. The first articulating surface <NUM> may have the shape of a half ellipsoid and preferably of a half three-axial ellipsoid in the z<NUM> - x<NUM> plane. The glenoid body <NUM> may have a half-ellipsoid, preferably of a half three-axial ellipsoid, cross sectional area in a plane defined by the first x-axis and the first z-axis.

In <FIG> a cross sectional view of an embodiment of a humerus implant <NUM> is shown. <FIG> shows a view of a humerus implant <NUM> in the y<NUM>-z<NUM> plane of an embodiment. The humerus implant <NUM> may include prosthesis cup <NUM>, an inlay <NUM> and a prosthesis stem <NUM>. The inlay <NUM> may have a second articulating surface <NUM>. The inlay <NUM> may have a concave shape. The inlay <NUM> may be located inside the prosthesis cup <NUM>. The inlay <NUM> may be connected to the prosthesis cup <NUM> be a loose or fixed connection. The prosthesis cup <NUM> may be connected to the prosthesis stem <NUM>. The prosthesis cup <NUM> may be connected to the prosthesis stem <NUM> by a loose or a fixed connection. The prosthesis cup <NUM> and the prosthesis stem <NUM> may be monolithic. The inlay <NUM> may have a second coordinate system (x<NUM>, y<NUM>, z<NUM>) with a second x-axis x<NUM> <NUM>, a second y-axis y<NUM> <NUM>, a second z-axis z<NUM> <NUM> and a second point of origin <NUM>. The inlay <NUM> may extend into the directions of the second x-axis x<NUM> <NUM>, the second y-axis y<NUM> <NUM>, and the second z-axis z<NUM> <NUM>. The second z-axis z<NUM> <NUM> may be the center axis of the inlay <NUM>. The inlay <NUM> may extend into the negative direction of the second z-axis z<NUM> <NUM>. The inlay <NUM> may have a second articulating surface <NUM>. The inlay <NUM> may have at least one inner radius <NUM>. The center of origin of the at least one inner radius <NUM> may be the point of origin of the second coordinate system. The at least one inner radius <NUM> may extend from the second point of origin to the second articulating surface <NUM>. The inlay <NUM> may have at least a first inner radius and a second inner radius. The first inner radius may be located in a plane defined by the second x-axis x<NUM> <NUM> and the second z-axis z<NUM> <NUM>. The second inner radius may be located in a plane defined by the second y-axis y1 <NUM> and the second z-axis. The second inner radius may be smaller than the first inner radius.

In <FIG> a cross sectional view of another embodiment of a humerus implant <NUM> is shown. <FIG> shows a view of a humerus implant <NUM> in the x<NUM>-z<NUM> plane. The humerus implant <NUM> may include prosthesis cup <NUM> and an inlay <NUM>. The prosthesis cup <NUM> may be connected to prosthesis stem (not shown). The inlay <NUM> may have a second articulating surface <NUM>. The inlay of this embodiment may correspond to the inlay of the embodiment of <FIG> in the x<NUM>-z<NUM> plane.

<FIG> shows a cross sectional view of embodiment of an inverse shoulder prosthesis <NUM> in the y<NUM>-z<NUM> (frontal plane). The inverse shoulder prosthesis <NUM> may include a glenoid implant <NUM> and a humerus implant <NUM>. The glenoid implant <NUM> may include a glenoid body <NUM>, a first articulating surface <NUM>, an attachment section <NUM>, at least one first radius <NUM>, an adapter <NUM>. The humerus implant <NUM> may include a prosthesis cup <NUM>, an inlay <NUM>, a second articulating surface <NUM>, at least one inner radius <NUM> and a prosthesis stem <NUM>. The glenoid body may have a half spherical cross section. The at least one first radius <NUM> may be a spherical radius. The at least one first radius <NUM> may match the inner radius <NUM>. The first articulating surface <NUM> and the second articulating surface <NUM> may form a bearing. The matching radii may accomplish an angular rolling-movement in the y<NUM>-z<NUM> plane. In an embodiment, the inner radius <NUM> may be <NUM> and the at least one first radius <NUM> may be <NUM>. The y<NUM>-z<NUM> plane may be the frontal plane of the inverse shoulder prosthesis <NUM>.

In <FIG> a cross sectional view in the x<NUM>-z<NUM> plane (transversal plane) of another embodiment of an inverse shoulder prosthesis <NUM> is shown. The inverse shoulder prosthesis <NUM> may include a glenoid implant <NUM> and a humerus implant <NUM>. The glenoid implant <NUM> may include a glenoid body <NUM>, a first articulating surface <NUM>, an attachment section <NUM>, at least one second radius <NUM>, an adapter <NUM>. The humerus implant <NUM> may include a prosthesis cup <NUM>, an inlay <NUM>, a second articulating surface <NUM>, at least one inner radius <NUM> and a prosthesis stem <NUM> (not shown). The at least one second radius <NUM> may be smaller than the at least one inner radius <NUM>. There may be a mismatch between the at least one second radius <NUM> and the at least one inner radius <NUM> The mismatch may be in a range of <NUM> - <NUM>. The mismatch may be in the transversal plane of the inverse shoulder prosthesis <NUM>. This mismatch may allow an oscillation in the transversal plane. This oscillation may be a translational movement. The mismatch may enable a translational movement of the humerus implant <NUM> along the x-axes, resulting in a roll and glide movement of the inverse shoulder prosthesis <NUM>. This mismatch may further enable an anatomically correct external and internal rotation of the inverse shoulder prosthesis <NUM>. Furthermore, the mismatch may improve the axial rotation of the humerus implant <NUM>. Due to the morphology of the glenoid body <NUM>, a combined roll-slide mechanism may occur in the glenohumeral joint during rotation, while a roll-mechanism may occur during arm elevation due to the spherical shape of the glenoid body <NUM> in the y-z plane. In an embodiment, the inner radius <NUM> may be <NUM> and the at least one second radius <NUM> may be <NUM>.

Claim 1:
An inverse shoulder prosthesis (<NUM>) comprising a glenoid implant (<NUM>) and a humerus implant (<NUM>),
the glenoid implant (<NUM>) having a glenoid body (<NUM>), with an articulating surface (<NUM>) having a convex dome shape,
the articulating surface (<NUM>) defining a first right hand coordinate system having a first x-axis (<NUM>), a first y-axis (<NUM>), a first z-axis (<NUM>) and a first point of origin (<NUM>), the first z-axis (<NUM>) being a center axis of the glenoid body (<NUM>),
the articulating surface (<NUM>) extending into a positive direction of the first z-axis (<NUM>), in positive and negative directions of the first x-axis (<NUM>), and in positive and negative directions of the first y-axis (<NUM>), or the articulating surface (<NUM>) oriented towards a humerus and the articulating surface (<NUM>) having a base in an anterior-posterior and a lateral-medial direction, the articulating surface (<NUM>) having a first radius (<NUM>) in a plane defined by the first y-axis (<NUM>) and the first z-axis (<NUM>),and a second radius (<NUM>) in a plane defined by the first x-axis (<NUM>) and the first z-axis (<NUM>), or the articulating surface (<NUM>) having a first radius (<NUM>) in a sagittal plane, and a second radius (<NUM>) in a frontal plane, and
the humerus implant (<NUM>) having a humeral body (<NUM>, <NUM>) and an inlay (<NUM>), having a concave shape,
the inlay (<NUM>) having a second coordinate system having a second x-axis (<NUM>), a second y-axis (<NUM>), a second z-axis (<NUM>) and a second point of origin (<NUM>),
the second z-axis (<NUM>) being the center axis of the inlay (<NUM>),
the inlay (<NUM>) extending into a negative direction of the second z-axis (<NUM>), or the concave inlay (<NUM>) having a center axis oriented towards a glenoid of a shoulder, and the inlay (<NUM>) having a concave shape and a base in an anterior-posterior direction and a craniocaudally direction, the inlay (<NUM>) having an inner radius(<NUM>),
characterized in that
the second radius (<NUM>) is in a range of <NUM> to <NUM> times of the first radius (<NUM>) and the first radius (<NUM>) is smaller than the inner radius (<NUM>) of the inlay (<NUM>).