Stemless convertible humeral shoulder prosthesis

Abstract

In some aspects, a shoulder implant with improved joint mobility includes a backing component, a neutral non-tilted bearing component, and a peg. The neutral non-tilted bearing component is positioned on a concave side of the backing component. The bearing component is made of a different material than the backing component and is configured to touch a glenosphere having a center of rotation, the bearing component being substantially radially symmetric. The peg extends from the backing component and is configured to connect to a humeral stem. A longitudinal axis of the peg of the backing component is offset from the center of rotation of the glenosphere, and a longitudinal axis of the backing component is aligned with the center of rotation of the glenosphere.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 322,201, filed March 21, 2022, which is expressly incorporated by reference in its entirety. [Background technology]

[0002] Shoulder replacement is a medical procedure commonly performed for the treatment of osteoarthritis, rheumatoid arthritis, and certain deformities associated with oncological conditions and trauma. There are two main types of joints available to the surgeon for treatment: anatomical and reverse. In the anatomical, the surgeon replaces the articular surface with engineered materials so that the articular surface has substantially the same shape as the natural anatomy. The stem can generally be fixed inside the canal of the humerus, and a metallic articular head can be rigidly fixed on its proximal side, the articular head having a convex articular surface adapted to articulate with a glenoid implant. The glenoid implant can include, at its posterior (medial) side, a specific peg or post or fin adapted to be rigidly fixed in the glenoid cavity of the scapula, and at its anterior side, a concave or flat articular surface adapted to articulate with the humeral head of the humeral implant.

[0003] When a reverse prosthesis is used, the articular surfaces are reversed in that a metallic ball is rigidly fixed in the glenoid cavity of the scapula and a concave articular surface is rigidly fixed to the humerus, thereby reversing the articulation pattern of the prosthesis.

[0004] The surgeon chooses between the two types of prosthesis by assessing several patient conditions, including the level of pain, the activity level of the patient, the degree of deformity or severity of bone deterioration, the strength of the surrounding soft tissue, and the presence or absence of previous surgery, as well as the health and strength of the rotator cuff muscles and tendons, among others. Rotator cuff disease is common among patients with shoulder arthritis. In this situation, it is commonly observed that the absence of rotator cuff dysfunction results in a condition in which an anatomical shoulder replacement prosthesis is not adequately stabilized by the surrounding soft tissue. In this case, due to the higher natural stability of the joint, a reverse shoulder replacement prosthesis may be preferred in some cases. In addition, reverse prostheses can advantageously utilize the remaining muscles in a manner in which they may be more effective in the absence of other soft tissue structures, by adjusting the position of the articular surfaces within the joint.

[0005] It is not uncommon for surgeons to choose to use an anatomical prosthesis and provide the patient with effective treatment through shoulder replacement surgery. However, over time and during the use of the prosthesis, the patient's rotator cuff complex may become insufficient, tear, or generally become diseased such that it can no longer perform its functions associated with normal joint kinematics. In this case, the surgeon may choose to perform a second surgery to remove the anatomical prosthesis and replace it with a reverse-type prosthesis.

[0006] Several attempts have been made to address the need to transform the articular surface without interrupting fixation. Primarily, these have been produced using a two (or more) system, where there is a metallic fixation component rigidly fixed to the glenoid cavity, and a polyethylene (PE) articular component that is secondarily fixed to the metallic component and provides a concave articular surface adapted to articulate with a humeral prosthesis. Although referred to herein as a PE component, some embodiments do not require the use of polyethylene and can be made from other biocompatible materials depending on the desired clinical outcome. The PE component is typically secured to the metallic fixation component by conventional industrial techniques such as snap-fit ​​mechanisms, snap rings, compression pins, overmolding of PE, and other such means.

[0007] The challenge with this particular joint in some cases is that the glenoid cavity is relatively small and the presence of bone in arthritic patients is generally significantly reduced. In this context, the surgeon has limited positioning and bone to work with in order to fit into the patient. In addition, the surgeon must be careful not to overstuff the joint, meaning an implant component that moves the new articular surface far from its original position so that the soft tissue is unnaturally tensioned, which can result in instability, accelerated where, soft tissue breakage, pain, reduced range of motion, or fracturing of the prosthesis and surrounding bone. When faced with these conditions, the prosthesis typically needs to be designed to remain relatively thin (generally one piece, where a PE glenoid implant typically has a 4mm thick articular surface). To design these modular components, little additional packaging space may be provided to fit the necessary attachment mechanisms for use without adversely affecting the performance of the overall joint replacement procedure. Thus, typically these designs result in "over-optimization" of the fixation and articulation parts to provide an adequate attachment mechanism, such that either the PE is too thin and not strong enough and the metal components are too small to provide adequate fixation, or the overall mechanism is insufficiently rigid, causing secondary wear surfaces to exist and resulting in the generation of wear particles that lead to PE disease.

[0008] A problem that may exist is that if a surgeon wishes to change the prosthesis type, anatomical prostheses are generally well fixed and adapted to the patient's body, and removal of the prosthesis may be very disruptive, leaving behind natural bone that is perhaps insufficient to support fixation of a reverse-type prosthesis. What is needed is a prosthetic system that provides a means by which the articular surface of the implant may be exchanged, such that the anatomical surface may be converted to a reverse-type surface, without changing the fixation components.

[0009] What is also needed is a simple means by which a surgeon can implant an inset anatomical glenoid implant, thereby allowing the surgeon to later remove the anatomical glenoid surface and replace it with a reverse-type glenoid surface, such that the primary means of fixation remains well fixed in the glenoid cavity at the moment of joint replacement.

[0010] Moreover, conventional systems are capable of changing the humeral inclination angle by providing increasingly inclined bearing components (e.g., polyethylene inserts), thus medializing the glenosphere's center of rotation and overstuffing the joint. A system is needed that can change the humeral inclination angle without changing the glenosphere's center of rotation and / or overstuffing the joint to provide increased range of motion. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Pat. No. 8,007,538 Summary of the Invention [Means for solving the problem]

[0012] In some aspects, techniques described herein relate to a shoulder implant with improved joint mobility, the shoulder implant including a backing component, a neutral, non-tilted bearing component on a concave side of the backing component, the bearing component made from a different material than the backing component and configured to touch a glenosphere having a center of rotation, the bearing component being substantially radially symmetric, and a peg extending from the backing component and configured to be connected to a humeral stem, the longitudinal axis of the peg of the backing component being offset from the center of rotation of the glenosphere, and the longitudinal axis of the backing component being aligned with the center of rotation of the glenosphere.

[0013] In some embodiments, the techniques described herein relate to a shoulder implant in which the backing component is inclined at an angle between about 1.25 degrees and about 30 degrees relative to the corresponding mounting surface of the humeral head.

[0014] In some embodiments, the techniques described herein relate to a shoulder implant in which the backing component is inclined at an angle between about 2.5 degrees and about 12.5 degrees relative to the corresponding mounting surface of the humeral head.

[0015] In some aspects, the techniques described herein relate to a shoulder implant in which the glenoid implant does not change the center of rotation of the glenosphere when inserted into a patient.

[0016] In some aspects, the techniques described herein relate to a shoulder implant that is configured for anatomical positioning.

[0017] In some aspects, the techniques described herein relate to a shoulder implant that is configured for reverse positioning.

[0018] In some aspects, the techniques described herein relate to a shoulder implant, wherein the bearing component has a depth of less than about 5.5 mm.

[0019] In some aspects, the techniques described herein relate to a shoulder implant, wherein the bearing component has a depth of between about 3 mm and about 5 mm.

[0020] In some aspects, the techniques described herein relate to a shoulder implant, wherein the bearing component comprises a plastic material.

[0021] In some aspects, the techniques described herein relate to a shoulder implant, wherein the plastic material comprises polyethylene.

[0022] In some aspects, the techniques described herein relate to a shoulder implant wherein the backing component comprises a metallic material.

[0023] In some aspects, the techniques described herein relate to a shoulder implant wherein the peg comprises a Morse taper.

[0024] In some aspects, the techniques described herein relate to a shoulder implant where at least a portion of an inferior-facing surface of the backing component configured to contact the prepared humeral surface comprises an oval or elliptical cross-section, at least a portion of an inferior-facing surface of the bearing component comprises a circular cross-section, and at least a portion of a superior-facing surface of the backing component comprises a circular cross-section, and a portion of the inferior-facing surface of the bearing component and a portion of the superior-facing surface of the backing component are configured to snap or otherwise mate with one another.

[0025] In some embodiments, the techniques described herein relate to a kit, wherein the multiple implants include a first implant and a second implant, wherein the backing component of the first implant is tilted by a first angle and the backing component of the second implant is tilted by a second angle different from the first angle, and wherein the centers of rotation of the glenospheres of the first implant and the second implant are at the same location.

[0026] In some aspects, the techniques described herein relate to a method of implanting a shoulder implant, the method comprising the steps of reaming a cavity in a glenoid surface; sizing a first implant comprising a first angulation relative to a stem, the implant comprising a neutral bearing component and an angled backing component comprising a first inclination angle relative to a corresponding mounting surface of the humeral head; sizing a second glenoid implant comprising a second angulation relative to the stem, the glenoid implant comprising a neutral bearing component and an angled backing component comprising a second inclination angle relative to a corresponding mounting surface of the humeral head; and implanting the second glenoid implant in the glenoid cavity, wherein the center of rotation of the glenosphere does not change between the first and second glenoid implants, allowing adjustment of version and inclination without changing the center of rotation.

[0027] In some embodiments, the techniques described herein relate to a humeral prosthesis comprising a proximal end including at least three radially outwardly extending fins and a stem extending distally from the proximal end to a distal end, the proximal end including a proximal end diameter defined by a circle contacting the most radially outwardly extending proximal tip of the at least three radially outwardly extending fins, the distal end including a distal end diameter, the proximal end diameter being between about 30 mm and about 50 mm, the distal end diameter being between about 5 mm and about 6 mm, and a ratio of the proximal end diameter and the distal end diameter being between about 5 and about 9.

[0028] In some embodiments, the techniques described herein relate to humeral prostheses having a ratio between about 5.5 and about 8.5.

[0029] In some aspects, the techniques described herein relate to a humeral prosthesis in which the proximal end includes a bowl-shaped concave surface.

[0030] In some aspects, the techniques described herein relate to a humeral prosthesis that includes a central aperture at a proximal end that is configured to mate with a reverse-type component. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 illustrates a side perspective view of an embodiment of a convertible humeral prosthesis according to some embodiments of the present invention. [Diagram 2] FIG. 2 is a bottom perspective view of the embodiment shown in FIG. 1. [Diagram 3] FIG. 2 is a top view of the embodiment shown in FIG. 1, also showing an aperture in the center of the upwardly facing surface of the neck of the prosthesis, which in some cases is configured to be utilized as a reverse-type adapter to facilitate placement or removal of a spherical ball onto the humeral head. [Figure 4] FIG. 2 is a side view of the embodiment shown in FIG. [Diagram 5] FIG. 2 is another side view of the embodiment shown in FIG. 1, also illustrating that the channel of the reverse adapter aperture extends into the neck and stem. [Figure 6] FIG. 13 is an inverted perspective view that also illustrates internal grooves along the neck and stem of the prosthesis. [Figure 7] FIG. 2 is another perspective view of the prosthesis shown in FIG. 1. [Figure 7A] 13 is a side perspective view of another embodiment of a convertible humeral prosthesis according to some embodiments of the present invention. FIG. [Figure 7B] FIG. 7B is a bottom perspective view of the embodiment shown in FIG. 7A. [Figure 7C]FIG. 7B is a top view of the embodiment shown in FIG. 7A, also showing an aperture in the center of the upwardly facing surface of the neck of the prosthesis, which in some cases is configured to be utilized as a reverse-type adapter to facilitate placement or removal of a spherical ball onto the humeral head. [Figure 7D] FIG. 7B is a side view of the embodiment shown in FIG. 7A. [Figure 7E] FIG. 7B is another side view of the embodiment shown in FIG. 7A, also illustrating that the channel of the reverse adapter aperture extends into the neck and stem. [Figure 7F] FIG. 13 is an inverted perspective view that also illustrates internal grooves along the neck and stem of the prosthesis. [Figure 7G] FIG. 7F is another perspective view of the prosthesis shown in FIG. 7F. [Figure 8] 11A-11D are various views of another embodiment of a humerus replacement prosthesis. [Figure 9] 11A-11D are various views of another embodiment of a humerus replacement prosthesis. [Figure 10] 11A-11D are various views of another embodiment of a humerus replacement prosthesis. [Figure 11] 11A-11D are various views of another embodiment of a humerus replacement prosthesis. [Figure 12] FIG. 1 is an illustration of one potential embodiment of the present invention depicting a conventional glenoid implant with an offset bearing component. [Figure 13] FIG. 13 is an illustration of one embodiment of an offset backing component that allows for 2.5 degrees tilt. [Figure 14] FIG. 13 is an illustration of one embodiment of an offset backing component that allows for 7.5 degrees of tilt. [Figure 15] FIG. 13 illustrates the use of one embodiment of an offset backing component that allows for 12.5 degree tilt. [Figure 16A]FIG. 1 illustrates one embodiment of a stemmed humeral implant. [Figure 16B] FIG. 1 illustrates one embodiment of a stemless humeral implant. [Figure 17A] FIG. 16B is a side view of the stemmed humeral implant of FIG. 16A. [Figure 17B] FIG. 16C is a side view of the stemless humeral implant of FIG. 16B. [Figure 18A] FIG. 16B is a cross-sectional side view of the stemmed humeral implant of FIG. 16A. [Figure 18B] FIG. 16C is a cross-sectional side view of the stemless humeral implant of FIG. 16B. [Figure 19A] FIG. 16B illustrates the stemmed humeral implant of FIG. 16A with a mounting base attached to the stemmed humeral implant. [Figure 19B] FIG. 16C illustrates the stemless humeral implant of FIG. 16B with a glenosphere, with the mounting base attached to the stemless humeral implant. [Figure 19C] FIG. 19B illustrates the stemmed humeral implant of FIG. 19A with a glenosphere attached to the mounting base of the stemmed implant. [Figure 19D] FIG. 19C illustrates the stemless humeral implant of FIG. 19B without a glenosphere and with a mounting base attached to the stemless humeral implant. [Figure 20A] FIG. 16C is a perspective view of the stemless implant of FIG. 16B. [Figure 20B] FIG. 20B is a side view of the stemless implant of FIG. 20A. [Figure 20C] FIG. 20C is a top view of the stemless implant of FIG. 20B. [Figure 20D] FIG. 20D is a cross-sectional side view of the stemless implant of FIG. 20C taken along line AA. [Figure 20E] FIG. 20E is a detailed view of a portion of the view of FIG. 20D. [Figure 20F] FIG. 20C is another side view of the stemless implant of FIG. 20B. [Figure 20G] FIG. 20D is a side view of the stemless implant of FIG. 20C taken along line DD. [Figure 20H] FIG. 20D is a cross-sectional side view of the stemless implant of FIG. 20C taken along line CC. [Figure 21] FIG. 2 is a side view of a broach used to prepare the humerus to receive one of the stemmed or stemless implants described herein. [Figure 22] FIG. 22 is another side view of the broach of FIG. 21 being used to prepare the humerus to receive one of the stemmed or stemless implants described herein. [Diagram 23] FIG. 23 is a perspective view of the humerus of FIG. 22 after it has been prepared to receive one of the stemmed or stemless implants described herein. [Figure 24] FIG. 24 is a side view of the humerus of FIG. 23 with a stemmed humeral implant implanted therein. [Diagram 25] FIG. 25 is a cross-sectional view of the humerus and stemmed humeral implant of FIG. 24. [Figure 26] FIG. 24 is a side view of the humerus and stemmed humeral implant of FIG. 23 with a glenosphere attached to the stemmed humeral implant. [Figure 27] FIG. 24 is a side view of the humerus of FIG. 23 with a stemless humeral implant implanted therein. [Figure 28] FIG. 28 is a side view of the humerus and stemless humeral implant of FIG. 27 with a glenosphere attached to the stemless humeral implant. [Figure 29] FIG. 24 is a side view of the humerus of FIG. 23 showing both stemmed and stemless implants implanted therein for comparison purposes. [Diagram 30] 1A-1D illustrate a method of implanting a stemless humeral implant. [Diagram 31]FIG. 1 illustrates one embodiment of a stemmed humeral implant system. [Figure 32A] FIG. 13 is an exploded view of another embodiment of a stemmed humeral implant system. [Figure 32B] FIG. 1 illustrates an exploded view of one embodiment of a stemless humeral implant system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] In particular, some embodiments of the present invention are focused on utilizing a convertible humeral prosthesis to advantageously exchange the glenoid articular surface from a concave shape to a convex shape without removing any components or interfaces associated with fixation of the implant within the glenoid cavity.

[0033] In some embodiments, embodiments of the present invention may be used with or modified by the particular advantages of using an inset glenoid fixation technique in anatomic shoulder arthroplasty, such as that described in U.S. Patent No. 5,399,363 to Gunther, which is incorporated herein by reference in its entirety. In some embodiments, the inset method includes identifying a patient having a glenoid surface, reaming a cavity into the glenoid surface, and inserting a glenoid implant into the cavity, the glenoid implant having a body portion and a single radially symmetric central peg oriented along a central axis of the implant, the body portion having a bearing surface on its peripheral edge, at least a portion of the peripheral edge of the body portion being inset with respect to the cavity so as to underlie an adjacent glenoid surface, such that the portion underlie the adjacent glenoid surface is circumferentially surrounded by cortical bone of the glenoid.

[0034] Further described is a method by which a surgeon can realize the use of the inset glenoid technique with an anatomical joint, while not requiring the removal of the rigid fixation between the inset fixation and the scapula after having the ability to convert the technique to a reverse type joint (in other words, allowing the rigid fixation support between the inset fixation and the scapula to remain in place during conversion from an anatomical prosthesis to a reverse type prosthesis).

[0035] 1-7 illustrate various views of a humerus replacement prosthesis 100 according to some embodiments of the present invention. Prosthesis 100 may optionally include a proximal ring element 102, such as a collar (which may be configured to be attached to a spherical ball head portion (not shown)) with a peripheral edge 103, which may be annular, such as circular as shown, and has an inferior-facing surface, which may optionally be concave (including a convex or flat bowl-like shape) and may include a cavity (or in-line, in other embodiments). The humeral prosthesis 100 can include an upwardly facing surface 114 of the proximal end 106, which can be concave and bowl shaped as shown, with the base and deepest portion of the bowl proximate the center of the upwardly facing surface 114 of the proximal end 106, such that there is a space 113 between the downwardly facing surface of the humeral head portion (not shown) and the upwardly facing surface 114 of the proximal end 106 of the prosthesis 100. In some embodiments, the depth of the bowl at the center of the concave curvature is between about 3 mm and about 7 mm, such as between about 4 mm and about 6 mm deep, such as about 5 mm deep. The proximal end 106 of the prosthesis 100 can include spaced flanges 107 (e.g., three equally spaced flanges 107, etc.), with apexes 111 of the flanges 107 narrowing and extending radially outward from the center of the proximal end 106 of the prosthesis 100. In some cases, the tri-flange design can provide improved stability and anti-rotation, among other advantages. Extending distally from the proximal end 106 at an angle relative to the longitudinal axis of the proximal end / neck 106 are the stem 110 and distal end 108 of the prosthesis 100.

[0036] In some embodiments, the stem 110 and distal end 108 of the prosthesis have a reduced thickness, e.g., tapered in the width dimension to about 6 mm or less, 5.5 mm or less, 5 mm or less, 4.5 mm or less, 4 mm or less, or less, such as between about 5.5 mm and about 6 mm, and inclusive of any two of the foregoing values, advantageously reducing the amount of natural humerus bone that needs to be removed, allowing for a stem 110 that is 3 mm to 4 mm or longer than conventional stems 110, and allowing the majority of fixation to occur in the proximal portion of the prosthesis (e.g., neck portion 106). FIG. 1 is a side perspective view of an embodiment of a prosthesis, FIG. 2 is a bottom perspective view of the embodiment shown in FIG. 1, and FIG. 3 is a top view of the embodiment shown in FIG. 1, also showing an aperture 120 in the center of the upwardly facing surface 114 of the neck 106 of the prosthesis, which in some cases is configured to be utilized as a reverse adapter to facilitate placement or removal of a spherical ball onto the humeral head. FIG. 4 is a side view of the embodiment shown in FIG. 1, and FIG. 5 is another side view of the embodiment shown in FIG. 1, also illustrating that the channel 124 of the reverse adapter aperture 120 extends into the neck 106 and stem 110. FIG. 6 is an inverted perspective view, also illustrating an internal groove 126 along the neck 106 and stem 110 of the prosthesis 100. FIG. 7 is another perspective view of the prosthesis shown in FIG. 1.

[0037] 7A-7G illustrate views of another embodiment of a humerus replacement prosthesis, which may be somewhat similar to, for example, Figures 1-7 and may incorporate any number of the features shown in, for example, Figures 1-7. Figure 7A illustrates a perspective view of a prosthesis 700 including an optional proximal ring element 702 (e.g., a collar, etc.) with a peripheral edge 703, which may be annular, such as circular as shown, and has an inferior-facing surface, which may optionally be concave (including a convex or flat bowl-like shape) and may include a cavity (or in-line, in other embodiments). The humeral prosthesis 700 may include an upwardly facing surface 714 of the proximal end 706, which may be concave and bowl shaped as shown, with the base and deepest portion of the bowl proximate the center of the upwardly facing surface 714 of the proximal end 706 such that a space 713 exists between the downwardly facing surface of the humeral head portion (not shown) and the upwardly facing surface 714 of the proximal end 706 of the prosthesis 700. The proximal end 706 of the prosthesis 700 may include spaced flanges 707 (e.g., three equally spaced flanges 707, etc.) with apexes 711 of the flanges 707 extending radially outward in a narrowing manner from the center of the proximal end 706 of the prosthesis 700. Extending distally from the proximal end 706 at an angle relative to the longitudinal axis of the proximal end / neck 706 are the stem 710 and distal end 708 of the prosthesis 700. Also shown is a transition zone 747, proximal to which the prosthesis 700 includes a porous coating, and distal to which the prosthesis 700 does not include a porous coating. The coating can include, for example, plasma spray, porous metal, hydroxyapatite, or other components that can promote cementless fixation to bone. However, in some embodiments, cement fixation can be utilized.

[0038] FIG. 7A is a side perspective view of an embodiment of a prosthesis, FIG. 7B is a bottom perspective view of the embodiment shown in FIG. 7A, and FIG. 7C is a top view of the embodiment shown in FIG. 7A, also showing an aperture 120 in the center of the upwardly facing surface 114 of the neck 106 of the prosthesis, which in some cases is configured to be utilized as a reverse adapter to facilitate placement or removal of a spherical ball onto the humeral head. FIG. 7D is a side view of the embodiment shown in FIG. 7A, and FIG. 7E is another side view of the embodiment shown in FIG. 7A, also illustrating that the channel 124 of the reverse adapter aperture 120 extends into the neck 106 and stem 110. FIG. 7F is an inverted perspective view, also illustrating an internal groove 126 along the neck 106 and stem 110 of the prosthesis 100. FIG. 7G is another perspective view of the prosthesis shown in FIG. 7F.

[0039] 8-11 illustrate various views of another embodiment of a humeral replacement prosthesis. FIG. 8 illustrates a humeral prosthesis, as may be described elsewhere herein, configured to be connected to a humeral head 801. FIG. 9 illustrates a perspective view of a humeral prosthesis 800 including a stem 810, a flange 807, and an adapter aperture 820 at a proximal end 806, as well as a distal end 808. FIG. 10 illustrates a side view of the humeral prosthesis 800. FIG. 11 illustrates a humeral head prosthesis 801 configured to be connected to an adapter aperture 820 of the humeral prosthesis 800 via a protrusion 899, such as, for example, via a press fit, threads, adhesive, or other technique.

[0040] As shown, some potential advantages of the humeral implant configuration as described herein include that fixation is focused proximally to preserve natural bone. The prosthesis can be cemented or cementless in some embodiments. The geometry of the prosthesis allows for ease of use, minimized surgical steps, and robustness since errors can be easily accommodated. The prosthesis can also be convertible to a reverse mold, which increases the chances of success and prevents or minimizes overstuffing. The prosthesis can also be advantageously inexpensive, logistically simple, and have minimal inventory requirements, since the diameter at or near the distal end of the stem can be constant, while the diameter at or near the proximal end of the stem can vary. For example, an operator can select a small number of humeral stem implants having proximal diameters (which can be measured as the smallest circle that can enclose the most proximal radially outward end element of the fin), e.g., 34 mm, 38 mm, and 44 mm, all of which have the same distal-most diameter, e.g., about 5.5 mm or about 6 mm, or about 7 mm or less, 6.5 mm or less, 6 mm or less, 5.5 mm or less, 5 mm or less, or less, or a range including any two of the foregoing values, etc. In some embodiments, the proximal-most diameter can be between about 25 mm and about 50 mm, e.g., about 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, or a range including any two of the foregoing values, etc.In some embodiments, the humeral stem implant can have a ratio of the most proximal diameter to the most distal diameter of the humeral stem of between about 5 to about 9, between about 5.5 to about 8.5, about 4.5, 4.75, 5, 5.25, 5.5, 5.75, 6, 6.25, 6.5, 6.75, 7, 7.25, 7.5, 7.75, 8, 8.25, 8.5, 8.75, 9, 9.25, 9.5, 9.75, 10, or a range inclusive of any two of the foregoing values. The ability to provide a set or array of humeral stem implants from which a physician can choose having a variety of proximal-most diameters (each having the same or substantially the same smaller distal-most diameter) can be contrasted with conventional humeral stem prostheses, in which within a set of different humeral stem sizes, as the proximal-most diameter increases, the distal-most diameter also typically increases. In some embodiments, the prosthesis is collarless. In some embodiments, the prosthesis has a total length of about 50mm, 51mm, 52mm, 53mm, 54mm, 55mm, 56mm, 57mm, 58mm, 59mm, 60mm, 65mm, 70mm, or more, or at least about 50mm, 51mm, 52mm, 53mm, 54mm, 55mm, 56mm, 57mm, 58mm, 59mm, 60mm, 65mm, 70mm, or more, or a range including any two of the above values.

[0041] Figures 12-15 illustrate various views of several embodiments of components of a glenohumeral replacement prosthesis. Figure 12 can be used to compare the effectiveness of several different embodiments of the invention as depicted in Figures 13-15.

[0042] FIG. 12 illustrates a conventional shoulder implant component that is implanted, for example, into a fossa of the scapula 201 (e.g., glenoid, etc.) or into a fossa of the humerus. FIG. 12 illustrates an implant with an inclined offset bearing component 204 (referring to the central axis of the bearing component being offset from the central axis of the backing component) with a backing component 205 that is aligned with a center of rotation 208. The prosthesis is implanted on or in a bone cavity 203 and includes a bearing surface 204 that is embedded on a backing component (e.g., a concave tray) 205. The bearing surface 204 lines the backing component 205 and can be made of any suitable material, such as a non-metallic, biologically compatible material (e.g., polyethylene). The backing component connects to an elongated stem 207 that is implanted into the bone 202. The backing component 205 connects to the elongated stem 207 by a peg or keel (e.g., Morse taper) 206. 12, the stem has a neck shaft angle α of approximately 132.5 degrees, which is the angle created by the intersection of the axis 209 through the elongated stem and the center of rotation 208. The backing component 205 is aligned with the axis 210 of the fossa. The bearing component 204 is offset so that the center of rotation 208 of the glenosphere 214 is medialized.

[0043] 13 illustrates a different embodiment, where the inclination angle of the humerus angle can be exclusively controlled by the offset backing component 211, while the bearing component is not offset. Due to the offset, the peg 206 of the backing component 211 is positioned such that a first distance from the peg 206 to a first end of the offset backing component 211 is not equal to a second distance from the peg 206 to a second end of the offset backing component 211. In some embodiments, the first distance is at least about 5%, 10%, 15%, 20%, 25%, or more, about 5%, 10%, 15%, 20%, 25%, or more, or about 5%, 10%, 15%, 20%, 25%, or more, or less than the second distance, or in a range including any two of the foregoing values. This is in clear contrast to FIG. 12, where the bearing component (e.g., polyethylene) is offset relative to the central axis of the backing component. FIG. 13 illustrates the effect of reverse articulation at 135 degrees using a backing component that provides 2.5 degrees of tilt when attached to an elongated stem 207. Rotation β1 represents 2.5 degrees of rotation about the axis 210 of the glenoid cavity. When added to the angle α, a 135 degree reverse articulation is achieved. Because the bearing component is not offset as in FIG. 12, the center of rotation of the glenosphere 215 remains constant and is not medialized (or lateralized) away from the center of rotation 208. Also, the central axis 290 of the backing component 211 is offset from the central axis 208 of the peg.

[0044] FIG. 14 is similar to FIG. 13 except that the angle of inclination of the backing component is different. FIG. 14 shows a desired 140 degree angle with the backing component providing a 7.5 degree inclination when attached to the elongated stem 207. Rotation β2 represents 7.5 degrees of rotation about the axis 210 of the glenoid fossa. When added to the angle α, a 140 degree reverse type articulation is achieved. Because the bearing components are not offset as in FIG. 12, the center of rotation of the glenosphere 215 has not been medialized away from the center of rotation 208 and remains in the same position as it was in FIG. 13.

[0045] FIG. 15 illustrates a 145 degree angle with the backing component providing a 12.5 degree cant when attached to the elongated stem 207. Rotation β3 represents 12.5 degrees of rotation about the axis of the glenoid fossa. When added to the angle α, a 145 degree reverse articulation is achieved. Because the bearing components are not offset as in FIG. 12, the center of rotation of the glenosphere 215 has not been medialized away from the center of rotation 208 and remains in the same position as it was in FIGS. 13 and 14.

[0046] In some embodiments of the invention, the tilt angle created by the backing component above the neck shaft angle of the elongate stem can be in the range of about 1.25 degrees, 2.5 degrees, 3.75 degrees, 5 degrees, 7.5 degrees, 10 degrees, 12.5 degrees, 15 degrees, 17.5 degrees, 20 degrees, 22.5 degrees, 25 degrees, 27.5 degrees, 30 degrees, 32.5 degrees, 35 degrees, or in a range including any two of the above values.

[0047] The natural prepared surface of the humerus against which the downwardly facing surface of the backing component abuts after installation generally has an oval or elliptical cross-section. In some embodiments, the downwardly facing surface of the backing component also has an oval or elliptical cross-section that substantially matches the cross-section of the surface of the humerus. In some embodiments, at least a portion of the downwardly facing surface of the bearing component (e.g., in some cases a polyethylene component) has a circular cross-section and is configured to snap into or otherwise mate with a complementary portion of the upwardly facing surface of the backing component (which may also have a circular cross-section).

[0048] Non-limiting potential advantages of the embodiment of Figures 13-15 are observed by way of example when comparing Figures 12 to 14. The depth of the backing component in Figures 13-15 can be about 5 mm, compared to about 7.5 mm for the embodiment of Figure 12, where the bearing component is offset relative to the center of rotation of the glenosphere as well as the central axis of the backing component. In some embodiments, the depth of the backing component is less than about 6 mm, less than 5.5 mm, less than 5 mm, less than 4.5 mm, less than 4 mm, less than 3.5 mm, less than 3 mm, or less, or in a range including any two of the aforementioned values. Varying the backing component angle in Figures 13-15 results in an additional amount of space, such as about 2.5 mm or more, or less than the space created in the bowl for the rotation of the glenosphere, as opposed to varying the amount of polyethylene plastic or other material in the bearing component. Thus, in some of the presented embodiments, the joint is less "stuffed" and not overstuffed, and can potentially have a greater range of motion. Moreover, the physician can choose between a range of different backing components with various inclination angles, while the bearing component is neutral (e.g., not inclined). As such, the inclination angle of the humerus can be controlled only by selecting the appropriate backing component, and the center of rotation of the glenosphere remains constant, regardless of the potentially different inclination angles of the backing components.

[0049] In some embodiments, a glenohumeral implant that allows for adjustable angles for anatomic or reverse arthroplasty is presented that includes a backing component, a bearing component on a concave side of the backing component, the bearing component being made from a different material than the backing component, and a peg extending from the backing component. Additionally, in some embodiments, the longitudinal axis of the backing component is offset from the center of rotation, but the center of rotation is not changed.

[0050] In some situations, it is desirable to avoid using stemmed humeral implants. Unlike stemmed humeral implants, stemless humeral implants have a shorter overall length such that no part of the implant enters the humeral canal when implanted. Instead, fixation occurs entirely within the cancellous portion of the bone. The stemless implant fins do not enter the bone canal and no direct bone marrow displacement occurs during implantation. Instead, fixation is limited to the metaphyseal portion of the bone (sometimes referred to as the proximal region of the humerus). A small portion of the distal end of the stemless humeral implant can enter the diaphyseal portion of the bone, but the implant never extends all the way to the intramedullary canal (where the bone marrow is located).

[0051] Stemless implants can advantageously provide at least equal fixation strength as stemmed implants, but with a less invasive procedure and less removal of natural bone structure, as discussed below. Stemless implants simplify implantation because there is no need to determine the diameter of the patient's humerus in order to properly size the implant stem (in terms of length or diameter). Instead, stemless implants are press fit into the proximal humerus region without destroying the remainder of the humerus.

[0052] 16A and 16B show perspective views of a stemmed humeral implant 1600 and a stemless humeral implant 1650, respectively. Each implant 1600, 1650 has a base portion (sometimes referred to as a backing component) 1602, 1652 that includes a number of fins (or flanges) 1604, 1606, 1654, 1656. The stemmed humeral implant 1600 includes a stem 1601. The illustrated embodiment includes one lateral fin 1604, 1654 and two medial fins 1606, 1656, respectively. The implants 1600, 1650 are symmetrical about a plane that bisects the lateral fins 1604, 1654 along their length (from the top or proximal end of the implant to the bottom or distal end of the implant). However, the fins 1604, 1606, 1654, 1656 need not be symmetrical about such a plane, and in fact may each have different dimensions and orientations.

[0053] Both implants 1600, 1650 include openings 1608, 1658 sized to receive and secure a base (not shown) (sometimes referred to as a non-tilted bearing component or a neutral non-tilted bearing component). The openings can include a slight taper (e.g., a Morse taper) to allow for a taper fit (or press fit) between the implants 1600, 1650 and the base. The base can include an articular surface (e.g., a glenosphere (for anatomical implantation) or a concave base (for reverse implantation), etc.). Any of the techniques described above for securing the base (sometimes referred to as a base portion) to the implants 1600, 1650 can be utilized.

[0054] FIG. 17A is a side view of the stemmed humeral implant 1600 of FIG. 16A, and FIG. 17B is a side view of the stemless humeral implant 1650 of FIG. 16B. The base portions 1602, 1652 can be covered with a bone growth promoting material (e.g., a porous coating, etc.) or any of the materials described herein. In one embodiment, the stemless implant 1650 does not include a bone growth material at its distal tip 1660. Providing an uncoated tip 1660 can facilitate implant 1650 removal, if required. The base portions 1600, 1650 can include any of the coatings described herein. For example, the coating can include, for example, plasma spray, porous metal, hydroxyapatite, or other components that can facilitate cementless fixation to bone. In other embodiments, the coating can include an osteoinductive or osteoconductive surface to promote bone ingrowth and fixation into the cavity. The surface can include, for example, cortical bone, cancellous bone, particulate matter, powder form, granules, chips, synthetic bone substitutes, growth factors and / or bone growth promoting proteins, or combinations thereof.

[0055] FIG. 18A is a cross-sectional view of the stemmed humeral implant 1600 of FIG. 16A, and FIG. 18B is a cross-sectional view of the stemless humeral implant 1650 of FIG. 16B. Each implant 1600, 1650 includes a tapered cavity 1612, 1662 and a threaded cavity 1614, 1664. The tapered cavity 1612, 1662 is sized and tapered to receive a base having either an anatomical or reverse-type articular surface attached thereto. The base (not shown) is tapered to provide a taper fit, Morse taper, and / or press fit fixation into the tapered cavity 1612, 1662 of the implant 1600, 1650. The threaded cavity 1614, 1664 can be used to secure an instrument for removing the base (not shown) if desired. For example, by using the threaded cavities 1614, 1664, the base can be removed to replace the anatomical base with a reverse-type base, as described in more detail above.

[0056] 19A-19D illustrate the interchangeability between the stemmed humeral implant 1600 and the stemless humeral implant 1650 by showing that the glenosphere 1700 attached to the base portion 1652 of the stemless humeral implant 1650 (as shown in FIG. 19B) is sized to be similarly attached to the base portion 1602 of the stemmed humeral implant 1600 (as shown in FIG. 19C). FIG. 19A illustrates the stemmed humeral implant 1600 without the glenosphere 1700, and FIG. 19C illustrates the stemmed humeral implant 1600 with the glenosphere 1700. FIG. 19B illustrates the stemless humeral implant 1650 with the glenosphere 1700, and FIG. 19D illustrates the stemless humeral implant 1650 without the glenosphere 1700.

[0057] 20A-20H show various views of one embodiment of a stemless implant 1650, as shown in FIG. 16B. The stemless implant 1650 includes multiple fins (e.g., three or more fins, etc.). The embodiment shown includes an outer fin 1654 and two inner fins 1656. Each fin 1654, 1656 has two sides and an outer edge. The sides 1670 of the outer fin 1654 can be flat and parallel to each other (see FIGS. 20C and 20F), and its outer edge 1672 has a convex curvature (see FIGS. 20A, 20B, 20D, 20E, and 20G). The inner fins 1656 (sometimes referred to as the anterior and posterior fins) have a concave surface 1674 and an opposing convex surface 1676, respectively (see FIGS. 20A and 20H). The convex surface 1676 of each medial fin 1656 is closest to and faces the outer fin 1654 (see FIGS. 20A, 20H). The outer edge 1678 of each medial fin 1656 has a convex curvature. In one embodiment, the curvature of the medial fin 1656 and the stemless implant body 1652 can be defined relative to a pivot or radius equally spaced from the medial fin 1656 that defines the overall radius of curvature of the stemless implant 1650. The portion 1680 of the implant body 1652 between the medial fins 1656 has a concave curvature (see FIG. 20D), and the portion 1682 of the implant body 1652 between the medial fin 1656 and the outer fin 1654 has a convex curvature (see FIGS. 20A, 20B, 20F, 20G, and 20H).

[0058] The curvature of the fins 1654, 1656 provides a greater lever out load than an implant having only straight fins or fins with flat sides. The curvature of the fins 1654, 1656 and body portion 1652 makes them much stronger and more difficult to remove from the bone, thereby providing much improved initial and long term fixation. The overall length of the implant 1650, as defined from the outermost proximal point of the stemless implant 1650 to the most distal point of the implant 1650, is 40 mm or less. Additionally, when viewed from above, the outermost edges of the fins 1654, 1656 can fall within or are surrounded by an oval or elliptical shape drawn to surround the implant 1650. In one embodiment, the outermost edges of the fins 1654, 1656 do not fall within or are not surrounded by a circular shape drawn to surround the implant 1650. The radial dimension of each fin 1654, 1656 similarly tapers from its proximal end to its distal end, the taper allowing the implant 1650 to be inserted into the bone without drilling the side of the bone.

[0059] FIG. 21 illustrates one embodiment of a broach 2100 that can be used to prepare a humerus 2102 to receive a stemmed or stemless humeral implant. An alignment post 2104 is positioned at a desired central location on the proximal surface of the humerus 2102. A hammering force is applied to an impact plate 2106, driving the cutting fins 2108 of the broach into the cancellous bone at the metaphysis of the humerus 2102, as shown in FIG. 22. When the broach 2100 is removed, the cancellous bone has a narrow slot 2110 configured to receive the fins of a stemmed or stemless implant and a circular and / or cylindrical opening 2112 configured to receive an implant body portion.

[0060] Figure 24 shows a stemmed implant 1600 implanted into a humerus 2102. The stem 1601 of the stemmed implant 1600 extends into a canal of the bone 2102. Figure 25 shows a cross-sectional view of the implant 1600 of Figure 24 implanted into the humerus 2102. Figure 26 shows the implant 1600 of Figure 24 with an articular surface (in this case a glenosphere cap 1700) attached to the stemmed implant 1600.

[0061] FIG 27 shows a stemless implant 1650 implanted into a humerus 2102. The stemless implant 1650 does not extend into the canal of the bone 2102. Instead, it is secured only to the metaphyseal portion of the humerus 2102. FIG 28 shows the stemless implant 1650 of FIG 27 with an articular surface (in this case, a glenosphere cap 1700) attached to the stemless implant 1650.

[0062] 29 shows what both a stemmed implant 1600 and a stemless implant 1650 would look like if inserted into the same humerus bone 2102. This illustration is provided for reference and comparison purposes only.

[0063] FIG. 30 is one embodiment of a method 3000 of implanting a stemless implant. Method 3000 begins at block 3002. The humerus is prepared to receive a stemless implant at block 3004. For example, a broach can be used to cut a slot and a cylindrical opening in the metaphysis of the humerus. The stemless implant is then secured to the humerus at block 3006. For example, the fins of the stemless implant can be inserted into the slots cut by the broach, and the body of the stemless implant can be inserted into the cylindrical opening created by the broach. Securement occurs only at the metaphysis because no portion of the implant is inserted into the medial humeral canal. Method 3000 ends at block 3008.

[0064] 31 illustrates one embodiment of a stemmed humeral implant system 3100. The stemmed humeral implant system 3100 includes a stemmed humeral implant 3102 and an articular surface, in this case a glenosphere 3104. The stemmed humeral implant 3102 includes a base portion 3106 and a stem 3108. The base portion 3106 includes one lateral fin 3110 and two medial fins 3112.

[0065] 32A and 32B show exploded views of a stemmed humeral implant system 3200 and a stemless humeral implant system 3250, respectively. The stemmed humeral implant system 3200 includes a stemmed humeral implant 3202. The stemmed humeral implant 3202 includes a base portion 3204 (sometimes referred to as a backing component) and a stem 3206. The stemless humeral implant system 3250 includes a stemless humeral implant 3252. The stemless humeral implant 3252 includes a base portion 3254 (sometimes referred to as a backing component).

[0066] Both the stemmed humeral implant system 3200 and the stemless humeral implant system 3250 include a base 3270 (sometimes referred to as a non-tilted bearing component or a neutral non-tilted bearing component) that is removably attachable to its respective base portion 3204, 3254. The non-tilted bearing component can be positioned on the concave side of the backing component and can be made from a different material than the backing component. The base 3270 is configured to receive an articular surface 3275 (e.g., a concave articular surface (as shown) or a glenosphere, etc.). The articular surface 3275 is configured to interface with a mating articular surface (e.g., a glenosphere 3280, etc.). A fixing member 3285 is provided to attach the mating articular surface (e.g., in the illustrated example, the glenosphere 3280) to the scapular structure.

[0067] Naturally, various other modifications, adaptations, and alternative designs are possible in light of the above teachings. Thus, it should be understood at this point that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. It is contemplated that various combinations or subcombinations of the specific features and aspects of the above-disclosed embodiments may be made and still fall within one or more of the present inventions. Furthermore, any particular feature, aspect, method, property, attribute, quality, attribute, or element disclosed herein in connection with an embodiment may be used in all other embodiments described herein. Thus, it should be understood that various features and aspects of the disclosed embodiments may be combined with or substituted for one another to form various modes of the disclosed invention. Thus, it is intended that the scope of the invention disclosed herein should not be limited by the specific disclosed embodiments described above. Moreover, the invention is susceptible to various modifications and alternative forms, specific examples of which have been shown in the drawings and are described in detail herein. However, the invention should not be limited to the particular forms or methods disclosed; on the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the various described embodiments and the appended claims. Any method disclosed herein need not be performed in the order described. The methods disclosed herein include specific acts performed by a practitioner. However, they may also include any third-party instructions of those acts, either explicitly or implicitly. For example, an act such as "inserting an implant into a glenoid cavity" includes "instructing to insert an implant into a glenoid cavity."Ranges disclosed herein also encompass any and all overlaps, partial ranges, and combinations thereof. Language such as "up to," "at least," "greater than," "less than," and "between," "between," and the like, includes the recited numbers. Numbers preceded by terms such as "approximately," "about," and "substantially," as used herein, include the recited numbers (e.g., about 10%=10%) and represent an amount close to the recited amount that still performs the desired function or achieves the desired result. For example, the terms "approximately," "about," and "substantially" can refer to an amount that is within less than 10%, less than 5%, less than 1%, less than 0.1%, and less than 0.01% of the recited amount. [Explanation of symbols]

[0068] 100 Humerus prosthesis 102 Proximal Ring Element 103 Peripheral edge 106 Proximal end, neck 107 Flange 108 Distal end 110 Stem 111 Vertex 113 Space 114 Upward Facing Surface 120 Aperture 124 channels 126 Inner groove 201 Scapula 202 Bones 203 Bone Cavity 204 Bearing surfaces, bearing components 205 Backing Component 206 Peg 207 Long and thin stem 208 Rotation Center 209 Axis passing through a slender stem 210 Axis of the Glenoid Fossa 211 Backing Components 214 Glenosphere 215 Glenosphere 290 Central axis of backing component 211 700 Humerus Prosthesis 702 Proximal Ring Element 703 Peripheral edge 706 Proximal end, neck 707 Flange 708 Distal end 710 Stem 711 Vertex 713 Space 714 Upward Facing Surface 747 Transition Zone 800 Humerus prosthesis 801 Humeral Head Prosthesis 806 Proximal end 807 Flange 808 Distal end 810 Stem 820 Adapter Aperture 899 Protrusion 1600 Stem Humerus Implant 1601 Stem 1602 Base part 1604 Outer fin 1606 Inner fin 1608 Opening 1612 Tapered Cavity 1614 Threaded Cavity 1650 Stemless Humerus Implant 1652 Base part 1654 Outer fin 1656 Inner fin 1658 Opening 1660 Distal tip 1662 Tapered Cavity 1664 Threaded Cavity 1670 Side of outer fin 1654 1672 outer edge 1674 concave surface 1676 Convex surface 1678 outer edge 1680: Portion of implant body portion 1652 between inner fins 1656 1682: Portion of implant body portion 1652 between inner fin 1656 and outer fin 1654 1700 Glenosphere 2100 Brooch 2102 Humerus 2104 Alignment Post 2106 Impact Plate 2108 Cutting Fin 2110 Slot 2112 Opening 3100 Stemmed Humeral Implant System 3102 Stem Humerus Implant 3104 Glenosphere 3106 Base part 3108 Stem 3110 Outer fin 3112 Inner fin 3200 Stemmed Humeral Implant System 3202 Stem Humerus Implant 3204 Base part 3206 Stem 3250 Stemless Humerus Implant System 3252 Stemless Humerus Implant 3254 Base part 3270-based 3275 Articular Surface 3280 Glenosphere 3285 Fixing parts α angle β1 rotation β2 rotation β3 rotation

Claims

1. 1. A shoulder implant having improved joint mobility, comprising: A backing component; a neutral, non-tilted bearing component on a concave side of the backing component, the bearing component being made from a different material than the backing component and configured to touch a glenosphere having a center of rotation, the bearing component being substantially radially symmetric; a peg extending from the backing component and configured to be connected to a humeral stem; Including, a longitudinal axis of the peg of the backing component is offset from the center of rotation of the glenosphere; The shoulder implant, wherein the longitudinal axis of the backing component is aligned with the center of rotation of the glenosphere.

2. The shoulder implant of claim 1 , wherein the backing component is inclined at an angle between about 1.25 degrees and about 30 degrees relative to a corresponding mounting surface of the humeral head.

3. The shoulder implant of claim 1 , wherein the backing component is inclined at an angle between about 2.5 degrees and about 12.5 degrees relative to a corresponding mounting surface of the humeral head.

4. The shoulder implant of claim 1 , wherein the glenoid implant does not change the center of rotation of the glenosphere when inserted into a patient.

5. The shoulder implant of claim 1 , configured for anatomical positioning.

6. The shoulder implant of claim 1 , configured for reverse positioning.

7. The shoulder implant of claim 1 , wherein the bearing component has a depth of less than about 5.5 mm.

8. The shoulder implant of claim 1 , wherein the bearing component has a depth of between about 3 mm and about 5 mm.

9. The shoulder implant of claim 1 , wherein the bearing component comprises a plastic material.

10. The shoulder implant of claim 9 , wherein the plastic material comprises polyethylene.

11. The shoulder implant of claim 1 , wherein the backing component comprises a metallic material.

12. The shoulder implant of claim 1 , wherein the peg comprises a Morse taper.

13. 2. The shoulder implant of claim 1, wherein at least a portion of an downwardly facing surface of the backing component configured to contact a prepared humeral surface comprises an oval or elliptical cross-section, at least a portion of the downwardly facing surface of the bearing component comprises a circular cross-section, and at least a portion of an upwardly facing surface of the backing component comprises a circular cross-section, and wherein the portion of the downwardly facing surface of the bearing component and the portion of the upwardly facing surface of the backing component are configured to snap or otherwise mate with one another.

14. 11. A shoulder implant kit, the kit comprising a plurality of implants according to claim 1, the plurality of implants comprising a first implant and a second implant, the backing component of the first implant being tilted by a first angle and the backing component of the second implant being tilted by a second angle different from the first angle, and the centers of rotation of the glenospheres of the first implant and the second implant being in the same location.

15. 1. A method of implanting a shoulder implant, comprising: reaming a cavity into the glenoid surface; Sizing a first implant including a first angulation relative to a stem, said implant including a neutral bearing component and an angled backing component including a first inclination angle relative to a corresponding mounting surface of the humeral head; sizing a second glenoid implant including a second angulation relative to the stem, the glenoid implant including a neutral bearing component and an angled backing component including a second inclination angle relative to a corresponding mounting surface of the humeral head; implanting the second glenoid implant into the glenoid cavity; Including, A method wherein the center of rotation of the glenosphere does not change between the first glenoid implant and the second glenoid implant, allowing adjustment of version and tilt without changing the center of rotation.

16. 1. A humerus prosthesis comprising: a proximal end including at least three radially outwardly extending fins; a stem extending distally from the proximal end to a distal end; Including, the proximal end includes a proximal end diameter defined by a circle contacting a proximal-most radially outwardly extending tip of the at least three radially outwardly extending fins; the distal end includes a distal end diameter; the proximal end diameter is between about 30 mm and about 50 mm; the distal end diameter is between about 5 mm and about 6 mm; A humeral prosthesis, wherein a ratio of said proximal end diameter to said distal end diameter is between about 5 and about 9.

17. The humeral prosthesis of claim 15, wherein the ratio is between about 5.5 and about 8.

5.

18. The humeral prosthesis of claim 15 , wherein the proximal end includes a bowl-shaped concave surface.

19. The humeral prosthesis of claim 15 , wherein the humeral prosthesis includes a central aperture at the proximal end configured to mate with a reverse-type component.

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