Patent ID: 12193942

DETAILED DESCRIPTION

It should be understood that although the term “stemless implant” is used herein, the term does not indicate that a stemless implant fully lacks any anchor, but rather a stemless implant may include an anchor that is significantly smaller and/or shorter than stems of typical known stemmed implants. Further, the stemless implants of the present disclosure generally include a base member intended for coupling to an end of a first bone of a joint, such as a humerus or femur, and an articulating member intended to attach to the base member and to provide articulation with the second bone of the joint (or a corresponding prosthesis attached to the second bone). Further, as used herein, the term “proximal” refers to a location closer to an individual's heart, and the term “distal” refers to a location farther away from the individual's heart. When used in the context of an implant, the terms “proximal” and “distal” refer to locations on the implant closer to, or farther away from, the heart when the implant is implanted in an intended manner.

FIGS.1and2show a base100of a stemless implant according to a first aspect of the disclosure. Base100generally includes collar101and central anchor140coupled thereto. Collar101may be generally cylindrical or annular and includes a proximal end surface102, a distal bone-engaging surface103, and side flange surface104extending along the circumference of the collar. As shown inFIG.1, proximal end surface102may be flat, but it can also be inclined or sloped in some embodiments. As inFIG.1, side flange surface104may have a uniform height, measured from distal to proximal ends of side flange surface104, or the height may be varied along proximal surface102. Although shown as generally cylindrical or annular, collar101may have other shapes. Anchor140is coupled to collar101at a first end141and extends distally from the collar along a longitudinal axis135to a second end174. In the illustrated embodiment, anchor140is tapered along longitudinal axis135so that first end141has a relatively large diameter, with the diameter of the anchor generally narrowing toward second end174until the anchor terminates in distal tip175; however, in some situations it may be appropriate for anchor140to be of uniform size throughout and not tapered. Anchor140further includes outer wall142extending from first end141toward distal tip175.

As shown inFIGS.1and3, base100includes an annular rim119positioned within an interior cavity of collar101. Rim119defines an opening130which is adapted to receive an articulating component (not shown) of the stemless implant. In the illustrated example, base100may be adapted to couple to a proximal humerus of a patient, with a prosthetic humeral head adapted to couple to the base via opening130, the prosthetic humeral head intended to articulate with a native or prosthetic glenoid of the shoulder joint. Although rim119and opening130may have any shape that suitably mates with the corresponding portion of the prosthetic humeral head, in one example a taper such as a Morse taper may be used to lock the prosthetic humeral head to rim119. The proximal end of rim119may be substantially flush with the proximal surface102of collar101, although in some embodiments it may extend either proximally or distally of proximal surface102. In the illustrated embodiment, the opening130defined by rim119extends from proximal end surface102of collar101along longitudinal axis135to a proximal surface139of anchor140. From surface139to tip175, anchor140may be generally solid, with the exceptions noted below in connection with the flexible portions of outer wall142.

The space between the inner circumference of collar101and the outer circumference of rim119defines a circular or cylindrical recess115. Recess115extends from proximal surface102distally along longitudinal axis135to surface139. Rim119separates opening130and recess115. Prior to attaching a prosthetic humeral head to base100, or after removing a prosthetic humeral head from the base, tools such as insertion and extraction tools may be inserted into opening130and/or recess115, as discussed below.

FIG.4shows a side view of base100, including outer wall142of anchor140. As can be seen more clearly inFIG.4, outer wall142may have a serrated configuration in which the outer wall includes alternating peaks143and troughs144in the proximal-to-distal direction, with each peak transitioning into a trough and each trough transitioning into a peak. As shown inFIG.4, peaks143and troughs144may be disposed substantially circularly around outer wall142, with the outer surfaces of the peaks and the troughs together defining the outer wall. In other embodiments, peaks143and troughs144may be disposed helically around outer wall142in a screw-like configuration. As noted above, each trough144is positioned adjacent to at least one peak143, and preferably two peaks. Each peak143may extend farther radially outward from the longitudinal axis135than each adjacent trough144. The transition between the outer circumference of each peak143to a distally adjacent trough143forms a distal surface147that is shaped frustoconically.

Although the outer circumferential surface of each peak143may be angled along the general contour of anchor140, each peak may also include a generally curved surface, where a peak transitions into an adjacent trough144. With this configuration, the proximal surface of each peak forms a counter support to resist pull-out, torque out, and/or lever out of the base100after implantation. For example, in the illustrated embodiment, the transition between the outer circumference of each peak143to a proximally adjacent trough144forms a hook143a. Hook143amay extend radially outwardly from adjacent troughs144in a proximal-facing hook shape. Hooks143acan be advanced into the native bone to fix the anchor to the bone. Once hooks143aare engaged in the bone, motion is restricted due to the hooked shape of hooks143a.

FIG.4further illustrates a plurality of slots160formed in the outer wall142of anchor140. Slots160are designed to enable flexible portions165of outer wall142to flex and extend radially outwardly of static portions166. Each slot160may extend through outer wall142so that the slot fully extends from the outer surface of the anchor and into recess115. Although various methods may be used to create slots160, in the illustrated embodiment the slot extends from holes161and162distally to a bottom surface165of the slot. Bottom surface165may extend around a portion of a circumference of anchor140and may be positioned in a plane that is parallel to proximal surface102of collar101and is coextensive with a plane defined by surface139. Holes161and162may be positioned on proximal portions of outer wall142near first end141. Holes161and162may be adjacent to each other but do not overlap, such that a thin connection is maintained between flexible portion165and the remainder of outer wall142. Although the bottom surface165of slot160is shown as being disposed through outer wall142at an angle generally perpendicular to longitudinal axis135, the angle may be of varying degrees. As shown inFIG.5, base100may include four slots160that form four flexible portions165positioned at substantially equal intervals around the circumference of anchor140, but it should be understood that more or fewer slots and/or flexible portions may be provided as desired.

Each flexible portion165, which may be thought of as the portions of outer wall142within a particular slot160, may be biased outwardly from adjacent surfaces of static portion166so that, in the absence of applied force, portions of each flexible member extend farther radially outward from longitudinal axis135compared to circumferentially adjacent areas of static portion166. With this configuration, a tool may be used to pull the flexible portions165radially inward to generally align with static portion166upon either insertion of base100into bone, or extraction of the base out of bone, such that the outer wall142of anchor140forms a substantially smooth surface. For example, an insertion and/or extraction tool (not shown) may be inserted into opening130and/or recess115to engage each flexible portion165to pull the flexible portions radially inward. This constrained or contracted condition may be referred to as the insertion and/or removal condition. During implantation of base100, for example into cancellous bone in a prepared proximal humerus, anchor140may be driven into the cancellous bone until collar101is substantially flush with the proximal humerus. Using a tool to transition base100to the insertion condition prior to implantation may provide a substantially smooth surface of the outer wall142of anchor140to ease the insertion of the base into the bone. Once base100is in the desired position in the proximal humerus, the tool may be disengaged from base100, allowing flexible portions165to flex radially outwardly into the bone in which the base is implanted. This condition may be referred to as the implanted or expanded condition. This additional radial force may further aid in achieving suitable fixation of the base100, despite the base being stemless. Further, during a revision procedure in which base100must be removed from the bone, merely pulling the base proximally out of the bone risks trauma due to the flexible portions165. Thus, a tool similar or identical to that described above may again be inserted into opening130and/or recess115and engage each of the flexible portions165to move them radially inwardly into the removal condition. This transition helps to create clearance between the proximal humerus and the outer wall142of anchor140, particularly at the locations of the flexible portions165. In some embodiments, in the absence of applied force, the flexible portions165may extend less than about 2 mm or about 3 mm compared to circumferentially aligned areas of static portion166. Although this amount of extension may seem small, the radial extension may enable the hooks143aassociated with the flexible portions165to further engage the bone for increased fixation. It should also be understood that the tool used to transition the base from the insertion condition or removal condition to the implanted or expanded condition may be the same tool that is used to hold the base100during implantation or explantation, although it may also be a separate tool with no additional function.

FIGS.6and7show a base200of a stemless implant according to a second embodiment of the disclosure. Base200generally includes collar201coupled with central anchor240. Collar201may be generally cylindrical or annular and includes a proximal end surface202, a distal bone engaging-surface203, and a side flange surface204. Proximal end surface202may be flat as shown, but in other embodiments it may be inclined or sloped. Side flange surface204may have a uniform height, the height measured from distal to proximal ends of side flange surface204, or the height may vary along proximal end surface202. Although shown as generally cylindrical or annular, collar201may have other shapes.

Base200includes central anchor240coupled to collar201at a first end241and extending distally from the collar along a longitudinal axis235to a second end274. In the illustrated embodiment, anchor240is tapered along longitudinal axis235so that first end241has a relatively large diameter, with the diameter of the anchor generally narrowing toward second end274until the anchor terminates in distal tip275; although, in some situations it may be appropriate for, anchor240to be of uniform size throughout and not tapered.

When used as part of a shoulder implant system, anchor240may be configured to be driven into the metaphyseal cancellous bone of the humerus and to facilitate engagement between base200and the bone for fixation. Anchor240may include a plurality of flutes255which may extend part or all of the longitudinal length of the anchor, for example from bone-engaging surface203to distal tip275. Each flute255may be positioned between two edges257, with the flute being recessed radially inwardly toward longitudinal axis235compared to the edges. Edges257may extend radially outwardly from longitudinal axis235to varying degrees depending on the position along the longitudinal axis. For example, edges257may have a minimum amount of radial extension from longitudinal axis235at or near distal tip275. The distance which the edges257extend radially outwardly from longitudinal axis235may then increase gradually in the proximal direction toward bone-engaging surface203. The edges257may reach their greatest amount of outward radial extension from longitudinal axis235at apex258. From apex258to bone-engaging surface203, the distance which edges257extend radially outward from longitudinal axis235may decrease until the edges connect to bone-engaging surface203. Flutes255are preferably concave between two adjacent edges257. Each flute255may include an enhanced fixation surface259in the region between bone-engaging surface203and a portion of the flute circumferentially aligned with apex258. The enhanced fixation surface259may take the form of a porous metal surface, such as porous titanium alloy, including Tritanium® by Howmedica Osteonics Corporation. As shown inFIG.8, fixation surface259may be in the general shape of a trough and may be convex. Fixation surfaces259may provide for enhanced in-growth of bone into anchor240, facilitating better fixation of base200following implantation. Fixation surfaces259may be rougher than the adjacent surfaces of anchor240, resulting in greater friction between the fixation surface259and the bone. This increased friction may help provide additional fixation by providing additional resistance against pull-out forces.

A fixation ring238may surround central anchor240, the fixation ring extending circumferentially around the central anchor at its connection with bone-engaging surface203. Fixation ring238may generally take the form of a recessed groove. As explained in greater detail below, upon implantation of base200into cancellous bone, the bone may flow into fixation ring238to help provide additional fixation. As shown inFIG.7, fixation surfaces259may extend into portions of fixation ring238to provide stronger fixation to the bone.

When implanting base200into a bone, such as the cancellous bone at the proximal end of the humerus, distal tip275of anchor240is driven into the bone. Because cancellous bone is relatively soft, the bone may effectively flow along anchor240, and in particular along the flutes255of the anchor. After the apex258of the edges257passes into the bone, some volume of bone may effectively “spring” back into the areas of flute255adjacent enhanced fixation surfaces259and also into fixation ring238. The positioning of the fixation ring238in the area of the flutes255proximal to the apex258results in stronger pull-out resistance for base200, with the resistance increasing further as bone grows into the pores of fixation surface259and fixation ring238.

As shown inFIGS.8and9, collar201defines a plurality of holes211and213extending from proximal end surface202to bone-engaging surface203and includes a plurality of peripheral anchors or pegs210extending distally from bone-engaging surface203to distal tips220. Pegs210aid in the fixation of base200to the bone, and may particularly assist in initial fixation. While there can be any number of pegs210on collar201, preferably there are four pegs positioned at substantially equal circumferential intervals around the collar. As shown best inFIG.9, pegs210may be located radially outward of holes213, although other relative spacing between pegs210and holes213may be appropriate. The use of at least four pegs210may provide for enhanced feedback, especially compared to the use of three or fewer pegs, while seating base200into the prepared bone during insertion. For example, upon initial contact of pegs210with a prepared flat bone surface, the surgeon may be able to easily determine if each of the pegs is simultaneously in contact with the bone. In particular, if all four pegs210are in contact with the proximal surface of the bone, the base200should not experience any significant amount of rocking or tilting. If the surgeon notices rocking of the base200, it should be clear that all four pegs210are not simultaneously in contact with the bone. If base200included three pegs, on the other hand, this rocking motion would not be expected despite a mismatch between a plane defined by the tips of the pegs and a plane of the prepared proximal bone.

As shown inFIG.8, pegs210extend distally from bone-engaging surface203to distal tips220. Pegs210may also include flutes215. Each flute215is positioned between two edges217, and flutes215may be generally concave between the two edges217. Each peg210may have a substantially identical structure to central anchor240but scaled to a smaller size. Those structures may provide substantially the same effect as the corresponding features on central anchor240, although the effects may be less dramatic due to the smaller sizes of the pegs compared to the central anchor. However, in other embodiments, the pegs210do not need to have identical but scaled down features as the central anchor240.

As shown inFIGS.7-9, holes211and213extend from proximal surface202to bone-engaging surface203. Holes211and213may be in any shape, round, oval, oblong, etc. Alternatively, holes211may be openings extending from proximal surface202to bone-engaging surface203near side wall204, such that side wall204includes curved recesses in the side wall. In the illustrated embodiment, holes211are oblong and a major axis of each hole extends from a point near central anchor240radially outwardly toward a point near side flange204of collar201. Holes213, may also be oblong, and slightly curved so that a major axis of each hole extends in the circumferential direction around central anchor240. Holes211and213may have various uses. For example, holes211and213may be used for passing one or more sutures through to aid in fixation of an object to the base200. Still further, holes211and213may be used to engage insertion and/or extraction instrumentation. In the illustrated embodiment, there are four holes211and four holes213, but there may be more or fewer of each of hole211and213. Further, there is no requirement that the number of holes211equal the number of holes213.

In addition to the uses described above, holes213may be sized and positioned to facilitate a revision procedure after the base200has been implanted into a patient for an amount of time. In the embodiment illustrated inFIG.8, holes213are positioned adjacent fixation surfaces259of flutes255and fixation ring238. With this positioning of holes213, a surgeon may insert a tool through holes213in order to chisel, ream, or otherwise cut away at bone that is adjacent to fixation surface259and/or fixation ring238. Strategically cutting away these areas of bone allows for easier removal of base200so that a new device may be implanted in its place.

Each hole211may be spaced generally midway between two adjacent pegs210. However, in some embodiments each hole211may be positioned adjacent a corresponding peg210. In such an embodiment, each hole211is preferably disposed adjacent a same side of the associated peg210. In other words, each hole211may be disposed on the right side adjacent to each peg210, or each hole211may be disposed on the left side adjacent to each peg. With each hole211adjacent the same side of an associated peg210, a tool inserted through the holes211may be used to ream or cut bone adjacent pegs210, such that the base200may be rotated to move the pegs into the bone cavity adjacent the holes211. This process may allow for easier removal of base200during a revision surgery. Rather than having one hole associated with each peg210, each peg may include two holes on either side of the peg so that the base200may be rotated in either direction to facilitate extraction of the base.

As with base100, base200may further define an opening230. Opening230may extend distally along longitudinal axis235from proximal surface202of collar201. Opening230may extend partially or fully through anchor240along longitudinal axis235or it may be shallow and extend only into collar201. A humeral head component (not shown) may be placed within opening230and attached thereto, for example by a taper lock such as a Morse taper. The humeral head component may be attached by any known securement means including screw or friction fit.

It should be understood that bases100and200may be formed of any suitable prosthetic grade material, including, for example, titanium alloys and/or other biocompatible metals and metal alloys. In some embodiments of base200, the porous portions of the base, such as fixation surface259and fixation ring238, may be provided via additive manufacturing over a base material such as titanium alloy. Further, although holes211and213are only described in connection with base200, similar or identical holes may be provided in base100. Still further, base100may include surfaces similar to fixation surfaces259and fixation ring238, for substantially the same purpose of increased fixation.

FIGS.10-13show base300of a stemless implant according to another aspect of the disclosure. Base300generally includes collar301coupled with central anchor340. Collar301may be generally cylindrical or annular and includes a proximal end surface302, a distal bone engaging-surface303, and a side flange surface304. Proximal end surface302may be flat as shown, but in other embodiments it may be inclined or sloped. Side flange surface304may have a uniform height, the height measured from distal to proximal ends of side flange surface304, or the height may vary along proximal end surface302. Although shown as generally cylindrical or annular, collar301may have other shapes.

Base300includes central anchor340coupled to collar301at a first end341and extending distally from the collar along a longitudinal axis335to a second end374. In the illustrated embodiment, anchor340is slightly tapered along longitudinal axis335so that first end341has a relatively larger diameter, with the diameter of the anchor slightly narrowing toward second end374; although, in some embodiments, anchor340may be of uniform size and not tapered.

As shown inFIGS.10and11, base300includes a socket, which in the illustrated embodiment is a hex member319, positioned within an interior cavity of collar301. Hex member319defines an opening330which is adapted to receive an articulating component (not shown) of the stemless implant. In the illustrated embodiment, opening330extends from proximal end surface302of collar301along longitudinal axis335to annular proximal surface339of anchor340, where the diameter of the opening decreases. With the decreased diameter, opening330then extends from annular proximal surface339of anchor340along longitudinal axis335to second end374. Thus, anchor340of base300may be cannulated. In this way, base300may be inserted through a pilot wire, such as a K-wire, to help provide more accurate placement of base member300within a prepared portion of the bone. As illustrated, hex member319has a hexagonal shape. The proximal end of hex member319may be substantially flush with the proximal surface302of collar301, although in some embodiments it may extend either proximally or distally of proximal surface302. A driver (not shown) having a mating internal hex member may engage hex member319. This may cause rotation of hex member319and base300which may provide torque for fixation of base member300in the bone. It should be understood that although the socket is illustrated as having a hexagonal shape, any shape suitable for transmitting torque from a correspondingly shaped driver tool may be suitable.

Anchor340includes outer wall342extending from first end341toward second end374. When used as part of a shoulder implant system, anchor340may be configured to be driven into the metaphyseal cancellous bone of the humerus and to facilitate engagement between base300and the bone for fixation. Threads345extend around outer wall342of anchor340and may be disposed helically in a screw-like configuration. When the driver (not shown) engages hex member319and causes rotation of base300, threads345may engage the bone and may provide greater fixation of the base to the bone.

FIGS.14-17show base400of a stemless implant according to another aspect of the disclosure. Base400generally includes collar401coupled with central anchor440. Collar401may be generally cylindrical or annular and includes a proximal end surface402, a distal bone engaging-surface403, and a side flange surface404. Proximal end surface402may be flat as shown, but in other embodiments it may be inclined or sloped. Side flange surface404may have a uniform height, the height measured from distal to proximal ends of side flange surface404, or the height may vary along proximal end surface402. Collar401may have other shapes, such as generally oblong and may include additional holes for use with insertion/extraction tools and/or for accepting sutures, similar to holes described in embodiments above.

Base400includes central anchor440coupled to collar401at a first end441and extending distally from the collar along a longitudinal axis435to a second end474. As illustrated, anchor440may include flanges451extending from bone-engaging surface403, substantially parallel to longitudinal axis435, to second end474of the anchor. As shown inFIGS.15and16, flanges451may include outer surfaces452and inner surfaces453. Inner surfaces453may be slightly concave along at least a portion of the inner surfaces. Inner surfaces453may include internal threads along at least a portion thereof. Flanges451may include a straight portion480and a tapered portion481. Straight portion480may extend generally parallel to longitudinal axis435, whereas tapered portion481may taper radially inwardly from the distal end of straight portion480to second end474of anchor440such that inner surfaces453nearer second end474may be radially closer to longitudinal axis435than a point on inner surface nearer straight portion480. Likewise, outer surfaces452nearer second end474may be radially closer to longitudinal axis435than a point on the outer surface nearer straight portion480. However, the degree of the taper of the outer surfaces452and inner surfaces453of flanges451may be different. For example, the taper of outer surfaces452may be less than the taper of the inner surfaces.

Anchor440includes support472, which may be a cylinder, extending from bone-engaging surface403of collar401along longitudinal axis435to a distal end surface471of the cylinder. Support472may be positioned generally centrally on bone-engaging surface403.

Base400includes opening430extending from proximal end surface402of collar401along longitudinal axis435to a distal end surface471of support472. The diameter of opening430may decrease near the distal end of support472. In the illustrated example, base400may be adapted to couple to a proximal humerus of a patient, with a prosthetic humeral head adapted to couple to the base via opening430, the prosthetic humeral head intended to articulate with a native or prosthetic glenoid of the shoulder joint. Although opening430may have any shape that suitably mates with the corresponding portion of the prosthetic humeral head, in one example a taper such as a Morse taper may be used to lock the prosthetic humeral head within opening430.

As shown inFIGS.17and18, anchor440may include screw nut450. Nut450may include a proximal end surface456, a side flange surface457, an angled surface458, and a distal end surface459. Nut450may be generally cylindrical. In the illustrated embodiment, nut450includes angle surface458; however, in other embodiments side flange surface457may connect with proximal end surface456and there may not be an angled surface. Nut450may include two openings470extending along longitudinal axis435from respective proximal and distal end surfaces456and459. Openings470may not connect and may remain two distinct openings. Openings470may have a hexagonal shape to matingly engage with a driver for rotation of the nut and movement in a distal direction, although any shape for transmitting torque from a correspondingly shaped driver may be suitable. Distal opening470may be used for manufacturing assembly. A tool (not shown) may couple with distal opening470to insert nut450into anchor440. Nut450may include external threads on the outer circumference of side flange surface457. The threads may be adapted to matingly engage the threads on inner surfaces453of flanges451. Nut450may maintain contact with at least a portion of inner surfaces453of the flanges.

Flanges451of anchor440may be expandable. The diameter of nut450across side flange surface457may be greater than the diameter across the inner surfaces453of tapered portion481of the flanges. During an implantation procedure, base400may be implanted into a bone, such as a proximal humerus, with nut450positioned in contact with or adjacent to support472. In this position, flanges451are in an insertion condition (which may also be referred to as a removal condition) in which the diameter of anchor440is in a constrained or contracted condition. After implanting anchor440into the proximal humerus, for example in cancellous bone, a driver may be passed through opening430, with an end of the driver engaging the opening470of nut450. The surgeon may manually or otherwise rotate the driver to cause corresponding rotation of nut450, while the remainder of base400remains stationary with respect to the bone. Rotation of nut450results in external threads of the nut engaging internal threads of the flanges451so that the nut translates distally toward tapered portion481of flanges451. As the nut450is driven distally, it engages tapered portion481of flanges451. Because the nut450has a larger diameter than the internal diameter of flange451when the flanges451are in the implanted condition, the nut forces the flanges to expand outwardly into an expanded or implanted condition. This expansion of flanges451into the cancellous bone may provide for enhanced fixation between base400and the bone, for example by increasing the force required for the base to be pulled out of the bone.

At least one flange451may include a stop (not shown) near the distal end of the flanges. The stop is designed to limit the distance nut450can translate distally. In another example, a driver (not shown) having a positive stop may be used to translate the nut while preventing translation beyond the intended position. The driver may be used alone or in conjunction with a stop on the flanges. In this way, the nut450will translate distally only to an intended location.

FIG.19illustrates base400′ that is identical to base400in most respects. For example, anchor440′ of base400′ may be completely identical to anchor440, and may include a screw nut identical to screw nut450. Thus, those components are not described again. However, collar401′ of base400′ may have an alternate shape. Whereas collar401of base400is illustrated as being cylindrical, collar401′ may be oblong with two substantially straight portions on the anterior and posterior sides of the collar, with two substantially rounded portions on the medial and lateral sides of the collar. The width of collar between the anterior and posterior ends may gradually increase from the medial rounded portion toward the lateral rounded portion, which may better correspond to the native anatomy of the proximal humerus. In addition to opening430′, which may be identical in form and function to opening430, collar401′ may include additional openings431′ that may be used to mate with an insertion or extraction tool (not shown) or for other suitable purposes, such as for receiving sutures, etc.

It should be understood that bases300and400may be formed of any suitable surgical grade material, including, for example, titanium alloys and/or other biocompatible metals, metal alloys, and/or plastics. Further, although holes211and213are only described in connection with base200, similar or identical holes may be provided in bases300and400for similar purposes.

For each base described above, if being used in a shoulder joint application for coupling to a prosthetic humeral head, the proximal humerus is generally prepared to have a substantially planar surface prior to implantation of the base. As noted earlier, each base described herein may be referred to as a stemless base. The collar of each base, however, may have a perimeter that is substantially similar to, or fits within, the perimeter of the proximal end of a typical stemmed base (not shown) for a more traditional shoulder implant. With this configuration, if a surgeon begins preparing a patient's proximal humerus to accept any of the bases described herein, and it is determined that a stemless implant will ultimately not be suitable for use in the patient, the surgeon may instead use a traditional stem in the patient, even though the proximal humerus was prepared for a stemless implant. In other words, the geometries of the bases described herein, and in particular the collars of the bases, allow a surgeon a contingency plan of switching to a traditional stemmed shoulder implant mid-procedure, if such a contingency plan is deemed preferable and/or necessary.

FIGS.20-23show base500of a stemless implant according to another aspect of the disclosure. Base500generally includes collar501coupled with central anchor540. Collar501may have a generally rounded cruciform shape, although in other examples, the collar may have other shapes including oblong or annular. Collar501includes a proximal end surface502, a distal bone engaging-surface503, and a side flange surface504. Proximal end surface502may be flat as shown, but in other embodiments it may be inclined or sloped. Side flange surface504may have a uniform height, the height measured from distal to proximal ends of side flange surface504, or the height may vary along proximal end surface502. Distal bone-engaging surface503may include a porous surface, for example porous titanium alloy, across all or a portion of its surface to provide better fixation of the implanted base with the bone.

Collar501includes at least one hole525extending from proximal end surface502to distal bone-engaging surface503. The holes525are each adapted to receive a screw. In the illustrated embodiment, there are four holes525and four screws, although there can be more or fewer holes and/or screws. The screws may be variable angle locking screws capable of being inserted through holes525at variable angles, with the heads of the screws having locking threads to mate with corresponding locking threads in the holes. The screws may engage the bone to provide fixation of base500in the bone. As shown inFIGS.21-23, the screws may have varying lengths to accommodate bone purchase to help with fixation, although any combination of screw lengths may be appropriate. In the illustrated embodiment, the medial screw has a length that is greater than the length of central anchor540.

Base500includes central anchor540coupled to collar501at a first end541and extending distally from the collar along a longitudinal axis535to a second end574. In the illustrated embodiment, anchor540has a straight portion536, which may be cylindrical, and a tapered portion537, which may be conical or frustoconical. Tapered portion537is tapered along longitudinal axis535so that the proximal end of the tapered portion has a relatively large diameter, with the diameter of the anchor generally narrowing toward second end574until the anchor terminates in distal tip575.

As with previous embodiments of the bases, base500may further define an opening530. Opening530may extend distally along longitudinal axis535from proximal surface502of collar501. Opening530may extend partially or fully through anchor540along longitudinal axis535or it may be shallow and extend only into collar501. A humeral head component (not shown) may be placed within opening530and attached thereto, for example by a taper lock such as a Morse taper. The humeral head component may be attached by any known securement means including screw or friction fit. Base500may include additional holes for use with insertion/extraction tools and/or for accepting sutures, similar to holes described in embodiments above.

FIG.22shows base500implanted within a humeral bone with variable angle locking screws. The benefit of using screws of different lengths is particularly well illustrated inFIG.22. For example, a screw that engages a hole525on the medial side of collar501may be longer than the other screws, as there may be a greater depth of bone available in this area.

FIG.23illustrates base500implanted into a humeral bone, similar toFIG.22. However,FIG.23also illustrates the expected implant profile of a traditional stem590of a stemmed shoulder implant. As can be seen by the superimposition of base500with the profile of a traditional stem590, the base500may be designed so that much or all of the portion of the base implanted into the humerus would occupy space that would also be occupied by a traditional stem590, if a traditional stem590were implanted into the humerus. As a result, if a humerus is prepared to accept base500, and it is determined that a more traditional shoulder implant with stem590would be desirable, the surgeon may choose to use traditional stem590instead. It should be understood that this concept may apply to each of the other bases described herein, so that a surgeon may prepare a proximal humerus to accept any of the bases described above or below (e.g. bases,100,200,300,400,600,600′,600″,900, etc.) and may choose mid-procedure to switch to a tapered stem590without having unnecessarily removed any bone. Such a change in procedure may become desirable, for example, if the surgeon determines that the stemless base would not be able to achieve suitable fixation with the humerus, for example because the bone quality is low.

FIGS.24-28show base600similar to bases200in many respects, the similar or identical features of which will not be described again here. In the illustrated embodiment, base600has a collar601that is generally annular, and may be circular, although in other examples, the base can be any shape, such as triangular, trapezoidal, etc. Base600includes curved side wall604which extends between proximal surface602and bone-engaging surface603. The curve of side wall604may help to decrease the amount of bone removed during surgery. Proximal surface602may include opening630which is adapted to receive an articulating component (not shown) of the stemless implant.

Base600includes central anchor640extending distally from bone-engaging surface603to distal end675. Anchor640includes a plurality of ribs670, each rib projecting radially outward of distal end675and extending to bone-engaging surface603. Ribs670extend along bone-engaging surface603to a position in close proximity to or adjacent to side wall604. Each rib670includes two lateral side walls671and curved outer surface673between the two lateral side walls. Lateral side walls671may be flat, concave, and/or convex. The outer surface673is rounded which may provide more surface to create bone in-growth after implantation of the base600.

Referring toFIGS.25-26, base600may include four ribs670that form a general “X” shape. As shown inFIG.26, two pairs of adjacent ribs may be oriented about 60 degrees apart from one another, and two other pairs of adjacent ribs may be oriented about 120 degrees apart from one another. However, it should be understood that other angles between the pairs of adjacent ribs may be suitable.

Anchor640includes surfaces676extending from distal end675to bone-engaging surface603. In the illustrated embodiment, each surface676is positioned between two ribs670, although in other examples there may be more or fewer surfaces676. In the illustrated embodiment, surfaces676are rounded and include grooves or channels677positioned near the distal end675of the base and extending in a direction toward bone-engaging surface603. Channel677tapers inwardly as it extends in the direction toward distal end675. Channel677may help facilitate bone in-growth after base600is implanted.

Base600may include holes612extending from proximal surface602to bone-engaging surface603. In the illustrated embodiment, base600includes two holes612, each positioned between the ribs670that are spaced substantially 60 degrees apart from one another. In other examples, however, there may be more or fewer holes612on the base600. Additionally, holes612may have the same diameter, or as in the illustrated embodiment, the holes612may have different diameters. As shown inFIGS.26-28, superior hole612ahas a smaller diameter than inferior hole612b. Superior hole612ais configured to receive variable angle screw695, the threaded diameter of which can be from about 3 to about 6 millimeters (mm) and is preferably about 4.5 mm Additionally, variable angle screw695can have about a 15 degree pre-tilt angle. Inferior hole612bis configured to receive fixed angle screw697, the threaded diameter of which can be from about 5 to about 7 mm and is preferably about 6.5 mm. Variable angle screw695can have a longer shaft than fixed angle screw697. For example, variable angle screw695may have a threaded shaft of about 24 mm, and fixed angle screw may have a threaded shaft of about 20 mm.

When implanted, base600is preferably oriented such that superior hole612ais positioned superior to inferior hole612bin relation to the shoulder. The inferior hole having a larger diameter may allow for a greater degree of fixation in the better quality bone having greater density.

Base600includes pegs610extending distally from bone-engaging surface603. Pegs610may be shaped identically to pegs210of base200. In the illustrated embodiment, there are two pairs of pegs610positioned radially outward of lateral side walls671of ribs670. Each pair of pegs610is positioned between ribs670that are spaced about 120 degrees apart from one another. However, there may be more or fewer pegs610, which may be larger or smaller. In some examples, base600may not include any pegs.

Like base200, base600may include one or more enhanced fixation surfaces on portions of anchor640and bone engaging surface603. The enhanced fixation surface may also be positioned on portions of pegs610and may extend onto side walls604of the base member. Generally, the enhanced fixation surface is positioned on proximal portions of the anchor640and the pegs610. The enhanced fixation surface may be identical to enhanced fixation surface259of base200and may take the form of a porous metal surface, such as a porous titanium alloy, including Tritanium® by Howmedica Osteonics Corporation.

Base600includes continuous chisel slots613extending through bone-engaging surface603to proximal surface602. Chisel slots613are positioned near the connection of ribs670and surfaces676with bone-engaging surface603. Thus, in the illustrated embodiment, chisel slots613include elongated portions614that track near ribs670and substantially curved portions616that track near surfaces676. Elongated portions614may be substantially straight or may exhibit a curved shape. Each chisel slot613may form a substantially “M” shape with each chisel slot including two elongated portions614and one curved portion616in between the two elongated portions. Elongated portions614track adjacent rib670, and extend in a direction that is about 30 degrees from a central axis C of the base that extends through the center of both holes612. Each elongated portion614has a width W, and the curved portion616has a width Y, the widths W and Y may be substantially equal or they may be different. Additionally, in an alternative embodiment, the two elongated portions614of each chisel slot613may have different widths from each other.

Chisel slots613are sized and positioned to facilitate a revision procedure after base600has been implanted into a patient for an amount of time. In the illustrated embodiment, chisel slots613are positioned adjacent to pegs610, surfaces676and lateral side walls671of the ribs670. With this positioning of chisel slots613, a surgeon may insert a tool into each slot613in order to chisel, ream, or otherwise cut away at bone that is adjacent to pegs610, surfaces676, and lateral side walls671of the ribs670. This strategic positioning of the chisel slots613allows for loosening of the bone ingrowth on enhanced fixation surfaces, which provides for easier removal of the base600so that a new device may be implanted in its place. Additionally, the “M” shape of the chisel slots may provide more stability to a chisel tool as the shape of the chisel slot may require less bending of a correspondingly shaped tool.

Although not shown, base600may include a feature similar to fixation ring238of base200. This fixation portion may surround all or a part of anchor640and may take the form of a recessed groove. The recessed groove may include an enhanced fixation surface to provide for better fixation of the base in bone.

FIG.29shows base600′ that is similar or identical to base600in most respects, the similar features of which will not be described here again. Each chisel slot613′ of the base600′ additionally includes a central elongated portion614′ extending radially outward from curved portion616′ and positioned between a pair of adjacent pegs610′. Central elongated portion614′ may help during revision procedures, as further described below.

FIG.30shows base600″ that is similar in many respects to bases600,600′, the similar features of which will not be described again here. Base600″ includes anchor640″ having ribs670″. At least one rib670″ includes fish hook serrations672″ positioned on a portion of the curved outer surface673″. Serrations672″ are sharp slots positioned on the outer surface673″ of a rib670″ that create better bite into the bone during implantation of the base600″.

FIGS.31-33show chisel tool700that can be used with bases600,600′,600″, particularly during a revision surgery. Chisel700includes handle710at proximal portion702, cutting structure720at distal portion704, and shaft715extending between the handle and the cutting structure. Cutting structure720has a complementary shape to chisel slot613, such that the cutting structure is sized and configured to fit within the chisel slot. In the illustrated embodiment, cutting structure720has a substantially “M” shape and includes support722and two prongs724positioned on either side of the support. Support722includes opposing rounded surfaces sized and configured to fit within curved portion616of the chisel slot613, one surface is generally convex, and the other surface is generally concave. Each prong724includes opposing flat surfaces726that terminate at a distal surface726, which is a substantially straight, flat cutting edge. Although in other examples, the cutting edge may include serrations, teeth, barbs, or other cutting features. Prongs724are sized and configured to fit within elongated portions614of the chisel slot613and are offset from a longitudinal axis of the chisel. In the illustrated embodiment, prongs724extend further distally than support722, although in other examples, the support can extend the same distance as the prongs. Chisel tool700is designed such that cutting structure720can be inserted into and through chisel slots613to remove bone. The positioning of the chisel slots in close proximity or adjacent to ribs670and pegs610allows for removal of bone near the enhanced fixation surfaces, which enables disengagement of the ribs and the pegs for easier removal of the base component during a revision surgery.

FIG.33shows a system including chisel tool700in conjunction with base600. As illustrated, prongs724are inserted through elongated portions614of the chisel slot613and support722is inserted in curved portion616of the chisel slot.

FIGS.34-38show another embodiment of a chisel tool800for use with bases600,600′,600″. Chisel800includes handle810at proximal portion802, cutting structure820at distal portion804, and shaft815extending along a longitudinal axis and terminating at distal surface817. Handle810can be any structure that provides a support for a surgeon to hold, and in the illustrated embodiment, the handle is a “T” bar. Handle810may include an impaction feature, not shown for impacting the chisel into bone. Shaft815is generally cylindrical and has a diameter D that is less than the width Y of the curved portion616of the chisel slot613of the base600, as shown inFIG.37. Cutting structure820extends generally transverse to the longitudinal axis of the shaft and includes curved portion816extending outwardly from a distal end of the shaft815and elongated portion814connected to the curved portion. Cutting structure820is sized and configured to fit within chisel slot613of base600, such that elongated portion814and curved portion816each have a width that is less than the width of the chisel slot. Specifically, as shown inFIG.36, elongated portion814of the cutting structure820of the chisel800has a width Z that is less than the width W of the elongated portion614of the chisel slot613of the base600. In this manner, cutting structure820of the chisel800extends into and through the chisel slot613to remove the bone in-growth for easier removal of the base during a revision surgery.

Cutting structure820includes proximal surface827, distal surface826opposite the proximal surface, and side walls829extending between the proximal and distal surfaces. Proximal surface827, distal surface826and side walls829are substantially flat and may include a plurality of cutting members or teeth828projecting from each surface to aid in the cutting of bone during a revision surgery. Distal surface817of shaft815also includes teeth828projecting distally therefrom, and in some examples, a portion of the length or the entirety of the length of shaft815includes a cutting feature, such as teeth828. The cutting features included on the proximal and distal surfaces and the side walls may be the same or different. For example, the side walls may include ridges, and the distal surface may include protrusions.

During a revision surgery, chisel tool800is aligned with chisel slot613of a base, for example base600. For example, elongated portion814of chisel tool800is aligned with a first elongated portion614of a first chisel slot613. A surgeon impacts handle810to drive cutting structure820into bone for bone removal. With cutting structure820extended completely through chisel slot613, torque is applied to handle810to rotate the cutting structure to remove bone. The removal of the bone is facilitated and expedited by the sharp teeth828on the cutting structure820. After the bone under the first chisel slot613is removed, the chisel tool can be used in the same manner to remove the bone under the second chisel slot of the base.

In another embodiment, two chisel tools800may be used together with a center guide (not shown) inserted within opening630of the base600. The center guide may be impacted to remove the implant during revision surgery.

In another alternative embodiment of chisel tool800(not shown), the cutting structure may be symmetric about the central axis, such that the cutting structure mimics the shape of chisel slot613, and there is an identical curved portion and elongated portion of the cutting structure on an opposing side of the shaft. In this manner, both elongated portions614of a first chisel slot613can be removed at the same time.

FIG.39shows chisel tool800′ in conjunction with base600′, the chisel tool800′ is similar in most respects to chisel tool800, the similar features of which will not be described. Chisel tool800′ has a shape complementary to chisel slot613′ of base600′. Chisel tool800′ includes cutting structure820′ with curved portion816′ and elongated portion814′ on opposing sides of shaft815′. Cutting structure820′ also includes central elongated portion814′ projecting from curved portion816′ sized and configured to fit into central elongated portion614′ of the chisel slot613. Each of the elongated portions614′ and the curved portion616′ includes a cutting feature, similar to the plurality of teeth828of the chisel800. In this manner, chisel tool800′ can remove bone from the entirety of the chisel slot613′ at the same time. Additionally, central elongated portion814′ allows for greater access to the bone between pegs610′, which can help to remove the bone between the pegs more easily to disengage the pegs. This can facilitate an easier removal of the base600′ during revision surgery.

FIGS.40-43show base900according to yet another aspect of the present disclosure. Base900is similar to bases200and600, the similar components of which will not be described again. In the illustrated embodiment, base900includes collar901that is generally annularly shaped and includes rounded side wall904extending between bone-engaging surface903and proximal surface902. Proximal surface902may include an opening (not shown) with a connection portion, such as a thread or taper, e.g. Morse taper, for connection to an articulating prosthetic component, such as a prosthetic humeral head, and preferably also with an instrument to facilitate the removal of the base during a revision surgery, such as by pulling out the implant or using a slap hammer.

Base900includes central anchor940extending distally from bone-engaging surface903and terminating at a distal end or tip975. Distal tip975allows for entry of the implant into the bone, and the distal tip may be angled between about 60 degrees and about 85 degrees from a vertical axis of the central anchor940, and preferably about 75 degrees from the vertical axis.

For purposes of illustration,FIG.41has been labeled to show the anterior (“A”), posterior (“P”), medial (“M”), and lateral (“L”) positions of base900. Base900includes four ribs970, which each corresponds to a distinct position of the base. For example, rib970ais oriented toward the medial position, rib970bis oriented toward the lateral position, rib970cis oriented toward the posterior position, and rib970dis oriented toward the anterior position. Ribs970aand970b, extending in the medial-lateral direction are substantially in line with one another, and ribs970cand970d, extending in the anterior-posterior direction are also substantially in line with each other and are substantially perpendicular to ribs970aand970b. As such, the ribs970may be said to define four quadrants of the base. Ribs970aand970bextend closer to side wall904than do ribs970cand970d. As such, the span across ribs970aand970bis greater than the diameter or span across ribs970cand970d. As a result, the ribs970have a greater span in the medial-lateral direction than in the anterior-posterior direction, as best shown inFIG.41. Anchor940includes surfaces976extending from distal end or tip975to bone-engaging surface903and positioned between two adjacent ribs970. Surfaces976are rounded and, in the illustrated embodiment, are generally convex.

Each rib970includes two opposing lateral side walls971and outer surface973between the two lateral side walls971.FIG.42shows a side view of base900and more particularly shows the span of side walls971of the medial rib970aand the lateral rib970b. As shown in this view, distal tip975transitions into ribs970. As distal tip975transitions into medial and lateral ribs970aand970b, respectively, outer surface973is generally convex. The convex shape increases the amount of material for enhanced ingrowth surface and increases the rotational stability of the base.

FIG.43shows the span of the side walls971of the posterior rib970cand anterior rib970d. As shown in this view, as distal tip975transitions into posterior and anterior ribs970cand970d, respectively, outer surface973is generally concave, which helps to compress and accommodate bone during impaction.

Additionally, as seen inFIGS.42-43, the width of each outer surface973of the ribs970decreases in the proximal to distal direction. As such, the width of the outer surface973is wider nearer to bone-engaging surface903than to the distal tip975.

Collar901includes a plurality of continuous chisel slots913extending through bone-engaging surface903to proximal surface902. In the illustrated embodiment, there are four chisel slots913with each chisel slot positioned radially outward of a surface976and between two adjacent ribs970. Chisel slot913is positioned along a path that tracks adjacent to ribs970on collar901, and the portion of each chisel slot adjacent medial and lateral ribs970aand970bextend further radially outward toward side wall904than the portion of each chisel slot that extends adjacent posterior and anterior ribs970cand970d. As shown inFIG.41, each chisel slot913is asymmetric about at least two planes.

Collar901includes a plurality of peripheral anchors or pegs910extending distally from bone-engaging surface903to distal tips920. Pegs910are positioned radially outwardly of chisel slots913, and have substantially the same structure as pegs210described above with reference to base200. Pegs910are oriented such that when the base is implanted, the pegs are fixed within the bone near the cortical rim and within the cancellous bone. With placement of the pegs910within good quality bone, the pegs aid in the fixation of base900to the bone, and may particularly assist in initial fixation. While there can be any number of pegs910on collar901, preferably there are four pegs positioned at substantially equal circumferential intervals around the collar. As described in greater detail above, the use of four pegs aids in initial fixation of the implant component with bone during implantation.

Like chisel slots613of base600, chisel slots913are sized and positioned to facilitate removal of the base during a revision procedure. With chisel slots positioned between anchor940and pegs910, the chisel slots allow for loosening of the bone ingrowth on the enhanced fixation surfaces on ribs970and surfaces976as well as the bone fixed to the pegs. A chisel tool (not shown) may be similar to tool720but may have a correspondingly mating shape to fit within the chisel slots913, may be used to remove the bone from the base to detach the base therefrom. Additionally, more than one chisel slot may be used at the same time. As the bone is removed from more than one chisel slot it creates a form of plug to allow the base to be removed at once. In an alternative embodiment (not shown), the chisel slots913may be angled to allow a tool to track along a path that closely matches or is substantially parallel to the longitudinal axis of the anchor940. As such, the profile of the each chisel slot may be perpendicular to collar901.

Collar901includes a coating forming an enhanced fixation surface that may be a porous metal surface, such as porous titanium alloy. The fixation surface may facilitate bone ingrowth after impaction and may be rougher for greater friction between the enhanced surface and bone for additional fixation. Portions of base900may include at least one layer of an enhanced fixation surface. In the illustrated embodiment, a portion of each side wall971of ribs970includes an enhanced fixation surface, and a portion of each surface976of the anchor940includes an enhanced fixation surface. Specifically, the portions of anchor940having enhanced surfaces may include three materials. A first, inner surface may be formed of solid metal, such as titanium, the second surface may be formed of a porous metal, such as a porous titanium alloy, such as Tritanium®, and a third and outer surface may be formed of a modified or directional Tritanium®. The outer surface may be formed to increase friction with the bone and may help to increase initial stability. In the illustrated embodiment, between about 30 percent and about 60 percent, and preferably between about 40 percent and about 50 percent, of the total depth of anchor940is solid, the depth being measured from the proximal end of the anchor to the distal end. This solid portion is in line with the punched cavity and helps to maintain alignment of the base during impaction into the punched cavity. Of course, other portions of base900, including all or a portion of collar901may include one or more layers of coatings, alternatively, the entirety of the base may include surface coatings for bone ingrowth.

In another alternative embodiment, as shown inFIGS.44-46, anchor940of base900includes a distal portion of enhanced fixation surface on side walls971of ribs970that includes a porous metal, such as a porous titanium alloy, such as Tritanium®.FIG.46shows the distal portion979of the ribs having a coating surface995of a porous metal, such as porous titanium alloy, such as Tritanium® on a solid metal. The portion981proximal to distal portion979includes a first, inner surface992of solid metal, a second surface993of a porous metal, such as a porous titanium alloy, and the third, outer surface994of modified or directional porous metal. Although other arrangements of surface coatings are contemplated.

In yet another alternative embodiment, as shown inFIG.47, as distal tip975transitions into each of the ribs970, including medial and lateral ribs970aand970b, outer surface973is generally concave. The concavity of the outer surface973of the ribs970is designed to accommodate the bicipital groove and maintain a distance therefrom.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.