Patent Description:
Over time and through repeated use, bones and joints can become damaged or worn. For example, repetitive strain on bones and joints (e.g., through athletic activity), traumatic events, and certain diseases (e.g., arthritis) can cause cartilage in joint areas, for example, which normally provides a cushioning effect, to wear down. When the cartilage wears down, fluid can accumulate in the joint areas, resulting in pain, stiffness, and decreased mobility. The same can happen in cases where tendons in a joint become lax or soft tissues in or adjacent the joint become damaged or worn.

Arthroplasty procedures can be used to repair such damaged joints. During a typical arthroplasty procedure, an arthritic or otherwise dysfunctional joint can be remodeled or realigned. A prosthesis or prostheses can be implanted to repair the damaged region(s). Arthroplasty procedures may take place in any of a number of different regions of the body, such as the knees, hips, shoulders, or elbows, for example. One type of arthroplasty procedure is a shoulder arthroplasty, in which a damaged shoulder joint may be replaced with prosthetic implants. The shoulder joint may have been damaged by, for example, arthritis (e.g., severe osteoarthritis or degenerative arthritis), trauma, or a rare destructive joint disease.

Prostheses that are implanted into a damaged region may provide support and structure to the damaged region, and may help to restore the damaged region, thereby enhancing its functionality. Prior to implantation of a prosthesis in a damaged region, the damaged region may be prepared to receive the prosthesis. In the case of a shoulder arthroplasty procedure, one or more of the bones in the shoulder area, such as the humerus and/or glenoid, may be treated (e.g., cut, drilled, reamed, and/or resurfaced) to provide one or more surfaces that can align with the implant and thereby accommodate the implant.

Document <CIT> discloses a glenoid implant having a trapezoidal keel stabilising the implant in the bone.

In a typical shoulder arthroplasty procedure, the native humeral head is replaced with a prosthetic humeral head, and a native glenoid is replaced with a prosthetic glenoid, with the prosthetic humeral head configured to articulate with respect to the prosthetic glenoid. However, it should be understood that, in some procedures, only one prosthetic component may be implanted into the joint, with the remaining native humeral head (or glenoid) configured to articulate with respect to the implant.

When implanting a prosthetic glenoid, as is typical with prosthetic joint implants, it is important that the implant is securely fixed to the anatomy. In order to securely fix a prosthetic glenoid component to the glenoid vault, one possible solution is to include fixation structures that extend deep into the glenoid vault for enhanced fixation. However, this may be difficult to accomplish because there is a wide variety of shapes of glenoid vaults among the population. Further, implanting fixation components deep into the glenoid vault may be problematic from the standpoint of revision procedures. In other words, if a second glenoid implant must be implanted during a second joint replacement procedure after the first joint replacement procedure, the first glenoid implant needs to be removed prior to implanting the second glenoid implant. If the first glenoid implant has fixation structures extending deep into the glenoid vault, a significant amount of native bone may need to be removed while in order to remove the first glenoid implant, which may make it difficult to effectively secure the second glenoid implant into the native anatomy.

According to one aspect of the disclosure, a prosthetic glenoid implant is for replacing a native glenoid. A bearing component has a first articulating surface adapted to articulate with a native or prosthetic humeral head, and a second surface opposite the first surface, the bearing component being formed of a polymer, the second surface including a first mating feature. A base component has a first surface and a bone-contacting surface, the first surface of the base component having a second mating feature adapted to engage the first mating feature in an assembled condition of the prosthetic glenoid implant, the bone-contacting surface adapted to contact the native glenoid, the base component being formed of metal and defining a plurality of apertures extending from the first surface of the base component to the bone-contacting surface of the base component. A plurality of fixation members each have a head and a threaded shaft, the threaded shaft of each fixation member adapted to pass through a corresponding one of the plurality of apertures, the head of each fixation member adapted to be positioned within a recess defined between the base component and the bearing component in an assembled condition of the prosthetic glenoid implant.

The bone-contacting surface of the base component may include an augment portion extending away from the bearing component in the assembled condition of the prosthetic glenoid implant, the augment portion having a convexity adapted to contact a concave neoglenoid portion of the native glenoid. At least one of the plurality of apertures may be positioned within the augment component.

The plurality of apertures may include a first group of peripheral apertures positioned adjacent an outer perimeter of the base component, and a central aperture substantially centered with respect to the outer perimeter of the base component. The central aperture may be positioned within a collet member extending away from the bone-contacting surface of the base component, the collet member adapted to expand upon receiving a collet screw therein.

The first mating feature may be a peripheral recess and the second mating feature may be a peripheral rim adapted to be received within the peripheral recess. Alternately, the first mating feature may be a peripheral rim and the second mating feature may be a peripheral recess, the peripheral rim being adapted to be received within the peripheral recess.

The base component may include a keel extending away from the bone-contacting surface, the keel being generally trapezoidal. The keel may have a length in a length direction extending away from the bone-contacting surface, and a width in a direction transverse the length direction, the width being smaller than the length. The keel may include a window defining a recess. The recess may be generally trapezoidal. The recess may include an array of circular openings. The base component may include a first slot extending from the first surface of the base component to the bone-contacting surface of the base component, the first slot being positioned adjacent the keel on a first side of the keel. The base component may include a second slot extending from the first surface of the base component to the bone-contacting surface of the base component, the second slot being positioned adjacent the keel on a second side of the keel opposite the first side of the keel.

The second surface of the bearing component may include a substantially circular extension member, the extension member having a plurality of recesses interrupting the circular extension member to define a plurality of individual extension members. Each of the individual extension members may include an anti-rotation protrusion extending in a direction radially away from a center of the circular extension member. The first surface of the base component may include a substantially circular member interrupted by a plurality of notches, each anti-rotation protrusion adapted to be received within a corresponding one of the plurality of notches in an assembled condition of the prosthetic glenoid implant.

As used herein, the term "proximal" means closer to the patient's heart, and the term "distal" means farther away from the patient's heart, when used in reference to a glenoid implant, when the glenoid implant is implanted in an intended orientation. Similarly, the term "anterior" means closer to the front of the patient, while the term "posterior" means closer to the rear of the patient. The term "superior" means closer to the patient's head, while the term "inferior" means closer to the patient's feet. The term "medial" means closer to the mid-line of the patient, while the term "lateral" means farther away from the mid-line of the patient. In the figures, like numbers refer to similar or identical parts. As used herein, the terms "substantially," "generally," "approximately," and "about" are intended to mean that slight deviations from absolute, for example plus or minus <NUM>%, are included within the scope of the term so modified. When ranges of values are described herein, those ranges are intended to include sub-ranges. For example, a recited range of <NUM> to <NUM> includes <NUM>, <NUM>, <NUM>, and other single values, as well as all sub ranges within the range, such as <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, and others.

<FIG> illustrate various views of a prosthetic glenoid implant <NUM> according to a first aspect of the disclosure. Referring to <FIG>, implant <NUM> generally includes a bearing component <NUM>, a base component <NUM>, and one or more fixation components <NUM>, although it should be understood that portions of base component <NUM> may also serve to provide an amount of fixation of the implant <NUM>. <FIG> illustrates a section of implant <NUM> taken along the section line <NUM>-<NUM> of <FIG>. Glenoid implant <NUM> may be symmetrical so that it is capable of being implanted on the glenoid of a left or right shoulder joint, although in some embodiments the implant <NUM> may be specific to the left or right shoulder joint.

As best seen in <FIG>, bearing component <NUM> includes a lateral bearing surface <NUM> and a medial bone-contacting surface <NUM> opposite the bearing surface. Bearing component may be formed of any suitable biocompatible material, including a polymer, such as polyethylene, including ultra-high-molecular-weight polyethylene (UHMWPE). Bearing surface <NUM> may have a concave surface and a shape that generally matches the shape and concavity of a healthy glenoid. After implantation, the bearing surface <NUM> functions to allow a prosthetic or native humeral head to articulate against the bearing surface. In the view of <FIG>, the top of bearing component <NUM> is the superior side, while the bottom of the bearing component is the inferior side.

Referring to <FIG>, the bone-contacting surface <NUM> of bearing component <NUM> may include superior and inferior contact platforms <NUM>. Superior and inferior contact platforms <NUM> may be generally semi-circular shaped and may present a substantially flat surface which corresponding surfaces of base <NUM> may contact in an assembled condition of the implant <NUM>. In addition, the heads <NUM> of superior and inferior fixation members <NUM> may similarly contact the substantially flat surfaces of the superior and inferior contact platforms <NUM>. It should be understood that the superior and inferior contact platforms <NUM> may be omitted, may have other shapes than shown, may be positioned other than shown, or may be provided in greater or fewer numbers than shown. The flat surfaces presented by the superior and inferior contact platforms <NUM> may be seen in <FIG>, and the positioning, size, and number of the platforms complements the structure of the base <NUM> and/or the heads <NUM> of fixation members <NUM>, described in greater detail below. Still further, the superior and inferior contact platforms <NUM> may assist in resisting rotation of bearing component <NUM> relative to base component <NUM>.

Still referring to <FIG>, a substantially circular rim <NUM> may extend from the bone-contacting surface <NUM> of bearing component <NUM>. In the illustrated embodiment, rim <NUM> is formed by a plurality of individual protrusions that are separated from one another by recesses <NUM>. As shown, rim <NUM> is formed of four semi-circular protrusions that are spaced about equally from one another, with each adjacent pair of semi-circular protrusions being separated by a void or recess <NUM>. However, it should be understood that more or fewer recesses (including no recesses) may be provided instead, and rim <NUM> need not lie along a perfect circle, as other shapes may be suitable. In the illustrated embodiment, rim <NUM> is positioned between the superior and inferior contact platforms <NUM>. In some embodiments, rim <NUM> may include mating features to assist in mating to base <NUM>. For example, in the illustrated embodiment, the radially outward-facing surfaces of the protrusions forming the rim <NUM> may include either a recess or a rib <NUM> extending along the outer circumference for engaging a complementary recess or rib of the base <NUM>, for example via a snap-fit, as will be explained in greater detail below.

<FIG> illustrate various views of base component <NUM>. In some embodiments, base component <NUM> is formed as a unitary or monolithic structure. Base component <NUM> may be thought of as including two main portions, including a keel portion adapted extend into the glenoid vault to provide better fixation of the implant within the glenoid, and a base portion configured to connect the keel portion to the bearing component <NUM>. Referring to <FIG> and <FIG>, keel <NUM> may extend medially from the remainder of the base component <NUM>, so that in an assembled condition of the implant <NUM>, the keel <NUM> extends away from the bone-contacting surface <NUM> of the bearing component <NUM>. In the illustrated embodiment, keel <NUM> includes a relatively long lateral portion where it joins the remainder of the base component <NUM>, a relatively short medial portion at the terminal end of the keel <NUM>, and angled superior and inferior portions connecting the medial and lateral portions. In other words, in the illustrated embodiment, keel <NUM> is substantially trapezoidal. The keel <NUM> may have a length in a length direction extending away from bearing component <NUM>, and a width in a direction transverse the length direction, the width being smaller than the length. Keel <NUM> may also include a recess, cut-out, or window <NUM> extending from the anterior surface of the keel <NUM> to the posterior surface of the keel <NUM>. In the illustrated embodiment, the window <NUM> is also substantially trapezoidal, although other shapes may be suitable. In one example, instead of a trapezoidal window <NUM>, keel <NUM> may include one or more circular through-holes, including for example, an array of circular through-holes. Examples of a circular array of through-holes are illustrated in <FIG>. <FIG> illustrates a base component <NUM>' that is identical to base component <NUM>, except that openings or windows <NUM>' are provided as an array of five similarly sized circular through-holes arranged in a column of three openings <NUM>' and a column of two openings <NUM>' positioned medially to the three openings. <FIG> illustrates another example of a base <NUM>" identical to base <NUM>, except that base <NUM>" includes three windows or openings <NUM>" in the form of similarly sized circular through-holes arranged in a generally triangular pattern. <FIG> illustrates a further example of a base <NUM>‴ identical to base <NUM>, except that base <NUM>‴ includes differently sized openings. In the example of <FIG>, base <NUM>‴ includes three relatively large circular through-holes <NUM>‴ arranged in a generally triangular pattern similar to <FIG>, but also includes a number of additional smaller circular through-holes <NUM>‴ positioned near the larger circular through-holes. It should be understood that <FIG> are merely exemplary of possible positioning of arrays of circular through-holes in a keel similar to keel <NUM>. The circular arrays of through-holes may allow bone ingrowth to be mechanically functional more quickly compared to a single larger individual window.

Keel <NUM> is shaped to extend relatively deeply into the glenoid vault, and the tapered superior and inferior surfaces of the keel may generally follow the contours of the native glenoid to allow for the keel to extend deep into the glenoid vault without compromising the outer cortical shell of the glenoid vault. The trapezoidal shape of keel <NUM> may also help resist rotation of the base component <NUM> after implantation, with the window <NUM> allowing for bone to enter the opening in the keel to further help stabilize the base component <NUM>, while simultaneously reducing the weight and overall bulk of the base component <NUM>. However, the weight and overall bulk of the base component <NUM> may not be a primary factor to take into consideration compared to the ability to achieve desired fixation. Preferably, base component <NUM> is formed of a biocompatible metal or metal alloy, such as titanium. Base component <NUM> may be provided with enhanced bone-ingrowth surfaces on all portions of the base component that are intended to contact bone, or otherwise at strategic locations only. For example, base component <NUM> may include a porous metal (such as porous titanium) surface to enhance bone growth into the base component <NUM> to enhance fixation over time. In one particular embodiment, the enhanced bone-ingrowth surfaces may be limited to the keel <NUM>, for example to the anterior and posterior surfaces of the keel <NUM>. This particular positioning may assist in a later revision procedure that utilizes cutting slots <NUM> in the base component <NUM>, described in greater detail below.

Referring to <FIG>, base component <NUM> includes a generally circular base portion <NUM> including a plurality of apertures <NUM> for receiving portions of fixation members <NUM> therethrough. The base portion <NUM> is partially circular, but includes superior and inferior extensions, which each include an aperture. These superior and inferior extensions may be configured to contact the superior and inferior contact platforms <NUM> of bearing component <NUM>. The positioning of the superior and inferior extensions of base portion <NUM> helps provide space for the keel <NUM> to have the desired position and size. As best shown in <FIG>, the base component <NUM> may include grooves <NUM> in the keel <NUM> where the superior and inferior extensions of the base portion <NUM> transition into the keel, with the grooves <NUM> contoured to provide clearance for superior and inferior fixation members <NUM> that extend through the superior and inferior apertures <NUM>.

Referring to <FIG>, the base portion <NUM> may include a substantially circular rim <NUM>, although rim <NUM> may also include superior and inferior extensions. The circular portion of rim <NUM> may be configured to couple to the circular rim <NUM> of the bearing component <NUM>, for example by a snap fit. To that end, rim <NUM> may include an interior lip or recess <NUM> for engaging with the rib <NUM> of rim <NUM>. When the base component <NUM> is coupled to the bearing component <NUM>, for example as shown in <FIG> and <FIG>, the superior and inferior apertures <NUM> of the base component <NUM> generally align with the superior and inferior voids or recesses <NUM> and/or the superior and inferior contact platforms <NUM> of bearing component <NUM>. Similarly, the medial and lateral apertures <NUM> of the base component <NUM> generally align with corresponding medial and lateral voids or recesses <NUM>. As a result, in the assembled condition of glenoid implant <NUM>, the heads <NUM> of fixation members <NUM> are at least partially positioned in corresponding voids of recesses <NUM> of the bearing component <NUM>, helping ensure that the bearing component <NUM> and the base component <NUM> cannot rotated with respect to one another. This is illustrated in <FIG>, which shows the assembled glenoid implant <NUM> with base component <NUM> omitted from the view to illustrate the position of the heads <NUM> of the fixation components <NUM>. It should be understood that, when the base component <NUM> is coupled to the bearing component <NUM>, a space is defined between the base component and the bearing component in which the heads <NUM> of the fixation components <NUM> are at least partially located. However, it may be preferable to include anti-rotation features other than, or in addition to, the position of the heads <NUM>, including for example the platforms <NUM> described above, or any of the anti-rotation features described elsewhere herein.

Referring back to <FIG>, base component <NUM> may include two cutting slots <NUM>. In the illustrated embodiment, base component <NUM> includes two elongated slots <NUM> that are define openings adjacent the anterior and posterior surfaces of keel <NUM>. The slots <NUM> may be used during a revision procedure to help cut bone. For example, a microtome, osteotome, or other cutting tool may be passed through the slots <NUM> during a revision procedure to cut the bone adjacent to the anterior and posterior portions of the keel <NUM>. As noted above, the anterior and posterior portions of the keel may include enhanced bone-ingrowth surfaces so that the fixation between the anterior and posterior portions of the keel and the native bone becomes particularly strong. As is described in greater detail below, these features may allow for the benefit of keel <NUM> to deeply penetrate into the glenoid vault for secure fixation, while still allowing for a revision procedure that minimizes the amount of bone that must be cut away to explant the glenoid implant <NUM>.

In an exemplary non-claimed method of use, the patient's glenoid may be prepared, for example by reaming, prior to implantation of glenoid implant <NUM>. Base component <NUM> may be implanted into the glenoid vault first. For example, a recess may be cut into the glenoid to receive the keel <NUM> in the desired orientation. Preferably, the recess is cut into the bone with a broach or a burr, with or without robotic assistance, although robotic assistance may be preferable. Although cement may be used to help fix the keel <NUM> into the glenoid, the fixation is preferably cementless. After advancing the base component <NUM> of, fixation members <NUM> may be inserted through the apertures <NUM> in the base component <NUM> and into the glenoid bone. In the illustrated embodiment, fixation members <NUM> are screws having a head <NUM> with a substantially flat proximal surface, and a threaded shaft for threading into the bone to further secure the base component <NUM> to the glenoid. Although various types of screws may be suitable for use as fixation members <NUM>, in one example, the fixation members <NUM> are screws with a diameter of about <NUM>. After the fixation members <NUM> have been inserted to secure the base component <NUM> to the glenoid, the bearing component <NUM> may be coupled to the base component <NUM>, for example via the snap-fit described above. The glenoid implant <NUM> may be configured as an "inlay" implant, as opposed to an "onlay" implant. As used herein, the term onlay refers to a baseplate or base component sitting on top of the prepared surface of the glenoid, whereas the term inlay refers to the baseplate or base component <NUM> being inset into the glenoid. In other words, according to one aspect of the disclosure, after being fully implanted, the base component <NUM> and fixation members may be positioned within the glenoid bone. <FIG> illustrates glenoid implant <NUM> in a final implanted position in the glenoid, with portions of the bone illustrated as transparent to show components of implant <NUM>.

If a revision procedure is desired, for example after glenoid implant <NUM> has been implanted for a length of time, the glenoid implant <NUM> may be explanted with a relatively small amount of bone needing to be removed given the amount of fixation structures provided on glenoid implant <NUM>. For example, during a revision procedure, the shoulder joint may be accessed and the bearing component <NUM> may be disconnected from the base component <NUM>, for example by pulling the bearing component to disengage the snap-fit (or other type) of connection between the two components. In other examples, a screw could be threaded into the bearing component <NUM> and the bearing component <NUM> could be levered out of the base component <NUM>. Still in other embodiments, a removal tool may include a screw tip which can be threaded into the bearing component <NUM> while pushing against the base component <NUM> to provide relative motion between the bearing component <NUM> and the base component <NUM> to disconnect the two components. With the bearing component <NUM> removed, access to the heads <NUM> of the fixation members <NUM> is provided. The fixation members <NUM> may be removed from the bone, for example by unscrewing the screws. Finally, the base component <NUM> will need to be cut out from the glenoid vault, at least because of bone ingrowth that has occurred over time to fix the keel <NUM> to the bone in the glenoid. As shown in <FIG>, a cutting tool such as a microtome or osteotome may be inserted through slots <NUM> to cut away bone adjacent the anterior and posterior surfaces of the keel <NUM>. As noted above, these surfaces may include an enhanced bone-ingrowth surface, and the connection between the bone and the keel adjacent these surfaces may be particularly strong. With the bone adjacent the anterior and posterior surfaces of the keel <NUM> being cut away, the base component <NUM> may be removed from the glenoid vault, and the revision implant may be implanted according to the particular procedure for the revision implant.

As should be understood from the description provided above, glenoid implant <NUM> may provide various benefits, particularly including enhanced fixation while maintaining the ability to effectively perform a revision procedure. While keeled glenoid implants have been used in the past, they have not gained popularity because of the difficulty in performing revision procedures - a problem that the current disclosure mitigates. Further, many prior art glenoid implants have an onlay design in which a baseplate, which may be conceptually similar to the base components described herein, sits on the prepared glenoid surface, which may result in the joint being overstuffed with implant structure, compared to the present disclosure in which the base component may have an inlay design that reduces the amount of implant structure extending into the joint space. Since baseplate or base component inlay designs are sunk into the bone, they may have more stability than onlay designs to resist eccentric loading of the component. The present disclosure combines an inlaid baseplate or base component with a bearing component that covers the superior and inferior extremes of the glenoid surface. The reduced stiffness of the bearing component may improve load sharing in these regions of the glenoid as compared with traditional full-coverage baseplate or base component designs. As should be also be understood, an inlaid baseplate or base component design may also increase the available joint space relative to an onlay design, reducing the above-noted overstuffing.

<FIG> illustrate components of a glenoid implant <NUM> according to another embodiment of the disclosure. It should be understood that glenoid implant <NUM> has many similar or identical features to glenoid implant <NUM>, and thus only the differences are described in connection with glenoid implant <NUM>. In other words, unless noted otherwise, the components of glenoid implant <NUM> are similar or the same as those described for glenoid implant <NUM>, including possible variations described in connection with glenoid implant <NUM>.

<FIG> are perspective views of glenoid implant <NUM>. Similar to glenoid implant <NUM>, implant <NUM> includes a bearing component <NUM>, a base component <NUM>, and fixation members <NUM>. A medial surface of bearing component <NUM> is illustrated in <FIG>. Similar to bearing component <NUM>, bearing component <NUM> includes a bone-contacting surface <NUM>, and a substantially circular rim <NUM> extending from the bone-contacting surface. Rim <NUM> is interrupted by recesses <NUM>, and may include a recess or rib <NUM> for engaging with base component <NUM>. The main difference between bearing components <NUM> and <NUM> is that bearing component <NUM> includes tabs <NUM> extending radially away from the center of rim <NUM>. As illustrated, each of the four portions of rim <NUM> includes a tab <NUM>, although in some embodiments less than all of the portions of rim <NUM> may include a corresponding tab <NUM>. As described below, tabs <NUM> may assist in the engagement of bearing component <NUM> to base component <NUM>, while simultaneously resisting the bearing component <NUM> from rotating with respect to the base component <NUM>.

<FIG> are perspective views of the base component <NUM> of glenoid implant <NUM>. Base component <NUM> may include a base portion <NUM> and a keel <NUM>. Keel <NUM>, including the opening <NUM> defined therein, may be substantially similar or identical to keel <NUM> and opening <NUM> of glenoid implant <NUM>. Base portion <NUM> may include a rim <NUM> and an internal rib or recess <NUM> to mate (for example via a snap-fit) with the recess or rib <NUM> of bearing component <NUM>. Rim <NUM> may be interrupted by a plurality of notches <NUM> around the circumference of the rim <NUM>, the notches <NUM> being sized, shaped, and positioned to receive a corresponding tab <NUM> therein. In addition to the notches <NUM>, the main differences between base component <NUM> compared to base component <NUM> are that base component <NUM> does not include slots, and does not include superior and inferior extensions similar to base component <NUM>. As with base component <NUM>, base component <NUM> may include grooves <NUM> in the keel <NUM> where the base portion <NUM> transitions into the keel <NUM>, with the grooves <NUM> contoured to provide clearance for fixation members <NUM> that extend through the corresponding apertures <NUM>. In order to facilitate a later revision procedure, apertures <NUM> may be utilized after the fixation members <NUM> are removed. In other words, a cutting tool may be passed through the apertures <NUM> on the anterior and posterior sides of the keel <NUM> to ream away bone that has grown into the implant <NUM>, for example including into enhanced bone-ingrowth surfaces on the anterior and posterior sides of the keel <NUM>. Otherwise, the implantation and revision procedures for glenoid implant <NUM> are substantially similar to those described above in connection with glenoid implant <NUM>.

<FIG> are perspective views of glenoid implant <NUM>. Similar to glenoid implant <NUM>, implant <NUM> includes a bearing component <NUM>, a base component <NUM>, and fixation members <NUM>. Bearing component <NUM> may be similar or identical to bearing component <NUM>, and thus is not described in greater detail herein.

<FIG> are perspective views of base component <NUM>, which may be substantially similar to base component <NUM>, with certain exceptions described below. Most notably, base component <NUM> includes a collet anchor <NUM> instead of the type of keel <NUM> of base component <NUM>. Collet anchor <NUM> may extend medially from a point at substantially at the radial center of base component <NUM>. In the illustrated example, collet anchor <NUM> includes a plurality of splaying members <NUM> adapted to splay away from one another upon the application of force. In the particular illustrated embodiment, collet anchor <NUM> includes three splaying members <NUM> that each include frictional engagement features, for example ribs <NUM>. In <FIG> and <FIG>, collet anchor <NUM> is illustrated in a splayed condition. It should be understood that, prior to implantation and prior to application of force, the collet anchor2350 may be in a non-splayed condition. Preferably, collet anchor <NUM> is formed from a metal or metal alloy, such as titanium.

Referring to <FIG>, base component <NUM> may include a central aperture <NUM>, preferably including threads, which opens to an interior surface of collet anchor <NUM>. Referring to <FIG>, glenoid implant <NUM> may include a collet screw <NUM>. Collet screw <NUM> may include a threaded head portion a shaft portion. In use, the shaft portion of the collet screw <NUM> may be passed through the central aperture <NUM> and the collet screw <NUM> may be advanced until the threaded head of the collet screw <NUM> engages the corresponding threads in central aperture <NUM>. The collet screw <NUM> may be advanced via rotation, for example via a screw driver. As the collet screw <NUM> advances, the shaft of the collet screw advances and forces the splaying members <NUM> of the collet anchor <NUM> to splay radially outward away from each other.

In an exemplary non-claimed method of implantation of glenoid implant <NUM>, after preparing the native glenoid, the base component <NUM> of glenoid implant <NUM> may first be inserted into the glenoid vault while the collet anchor <NUM> is in the non-splayed condition. Then, fixation members <NUM> may be inserted through the peripheral apertures and into the bone to secure the base component <NUM> to the glenoid. Either before or after inserting the fixation members <NUM>, the collet screw <NUM> may be rotated to cause the splaying members <NUM> of the collet anchor <NUM> to splay outwardly, to further enhance the fixation of the base component <NUM> to the glenoid. With the base component <NUM> fixed in place, the remainder of the glenoid implant may be assembled in substantially the same fashion as described above in connection with glenoid implant <NUM>. Although either order is suitable, it may be preferable to place the fixation members <NUM> prior to activating the collet anchor <NUM> to limit the stresses on the collet anchor <NUM> after the collet is deployed.

During a revision procedure, after the bearing component <NUM> is removed from the base component <NUM>, the fixation members <NUM> may be removed, and the collet screw <NUM> removed to allow the collet anchor <NUM> to un-splay, at which point the collet anchor <NUM> may also be removed from the bone.

<FIG> is a perspective view of bearing component <NUM> coupled to base component <NUM>, with fixation members <NUM> and center anchor <NUM> omitted for purposes of illustration. <FIG> and <FIG> are perspective views of bearing component <NUM> isolated from other components of the system. Base component <NUM> may be substantially similar to base component <NUM>, with certain exceptions described below. Most notably, base member <NUM> includes an augment portion <NUM>, and includes a central aperture <NUM> for receiving a central anchor <NUM> instead of the keel <NUM> of base component <NUM>.

Referring to <FIG>, base component <NUM> includes a central aperture <NUM> for receiving a center anchor <NUM>. Center anchor <NUM>, which is illustrated in <FIG>, may be a threaded screw similar to fixation members <NUM>. However, in some embodiments, center anchor <NUM> may be larger (e.g. have a larger diameter) than the other fixation members <NUM>. Functionally, the center anchor <NUM> may assist in securing the base component <NUM> to the glenoid, with the remaining fixation members <NUM> further helping in the initial securement of the implant <NUM>. Preferably, the center anchor <NUM> may be locked into the base component <NUM> to better assist in the overall long-term fixation of the implant <NUM>. As with the other fixation members <NUM>, center anchor <NUM> is preferably formed of a biocompatible metal or metal alloy.

Still referring to <FIG>, base component <NUM> may be mostly similar to base component <NUM>, for example including the plurality of apertures for receiving the fixation members <NUM>, as well as recesses and/or rims to allow for the base component <NUM> to couple to bearing component <NUM>, for example including via a snap-fit. In addition to central aperture <NUM>, the other main difference between base component <NUM> and base component <NUM> is the inclusion of the augment portion <NUM>. Augment portion <NUM> may be generally ramped and include a convex or partially-convex bone-contacting surface, at least a portion of which extends farther away from bearing component <NUM> than other portions of base component <NUM>. Augment portion <NUM> may be sized and shaped to be implanted on a concave neoglenoid portion of the glenoid that has experienced a partial wear pattern, such as that classified as B2 Walch type of glenoid wear. In the illustrated example, two of the apertures adapted to receive fixation members <NUM> are positioned within the augment portion <NUM> of the base component <NUM>, although more or fewer apertures may be positioned within the augment portion <NUM> in other embodiments.

Further examples of augmented glenoid designs that may be suitable for use with glenoid implant <NUM> are described in greater detail in <CIT>, titled "Augmented Glenoid Design. " Although one particular size of augmented portion <NUM> is illustrated in connection with glenoid implant <NUM>, it should be understood that a single bearing component <NUM> may be provided with a set of base components <NUM> that differ in the size of the augmented portion <NUM>, so that a user, such as a surgeon, may use a base component <NUM> having an augmented portion <NUM> that best matches the specific glenoid wear pattern of the patient being treated.

Claim 1:
A prosthetic glenoid implant (<NUM>) for replacing a native glenoid, the prosthetic glenoid implant comprising:
a bearing component (<NUM>) having a first articulating surface (<NUM>) adapted to articulate with a native or prosthetic humeral head, and a second surface (<NUM>) opposite the first surface, the bearing component being formed of a polymer, the second surface including a first mating feature;
a base component (<NUM>, <NUM>', <NUM>", <NUM>‴) having a first surface and a bone-contacting surface, the first surface of the base component having a second mating feature adapted to engage the first mating feature in an assembled condition of the prosthetic glenoid implant, the bone-contacting surface adapted to contact the native glenoid, the base component being formed of metal and defining a plurality of apertures (<NUM>) extending from the first surface of the base component to the bone-contacting surface of the base component, the base component including a keel (<NUM>) extending away from the bone-contacting surface, the keel being generally trapezoidal such that it has a length in a length direction extending away from the bone-contacting surface, and a width in a width direction transverse the length direction, the width being smaller than the length; and
a plurality of fixation members (<NUM>) each having a head (<NUM>) and a threaded shaft, the threaded shaft of each fixation member adapted to pass through a corresponding one of the plurality of apertures, the head of each fixation member adapted to be positioned within a recess defined between the base component and the bearing component in an assembled condition of the prosthetic glenoid implant;
characterised in that the base component includes a base portion (<NUM>) provided with superior and inferior extensions, which each includes an aperture (<NUM>), said apertures in the superior and inferior extensions forming superior and inferior apertures for superior and inferior fixation member (<NUM>) to extend therethrough, so that the superior and inferior extensions and fixation members are respectively positioned superior and inferior to the keel along a height direction transverse to the length and width directions.