Patent ID: 12239539

DETAILED DESCRIPTION

This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. The drawing figures are not necessarily to scale, and certain features may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. When only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses, if used, are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures.

The structures of the joint replacement prosthesis of the present disclosure will now be described using an example embodiment that is configured as a tibia baseplate in an ankle replacement whose stem(s) can be inserted into the prepared distal end of a tibia. However, the structures of the joint replacement prosthesis described herein can be implemented in other joint replacement applications as well. For example, as a tibia baseplate in knee joint replacement, a glenoid baseplate in a shoulder joint replacement, and for fixation of a talar implant.

The distal end of a tibia can be prepared in a similar manner as done in connection with existing tibia implant portion of total ankle replacement systems and the tibia canal can be prepared for the modular stem from the proximal direction without having to go through the patient's foot. The tibia base of the present disclosure can also comprise other beneficial features that enhance the stability of the tibia base in the tibia; including but not limited to fins, keels, ridges, posts, roughened surfaces, tapers, threads, screws, and expanding structures.

Referring toFIGS.1A-3C, the present disclosure provides an example embodiment of a joint replacement prosthesis10that utilizes a base component100and one or more modular stems200that engages the base component100.FIG.1Ais an illustration of an example of the base component100according to an embodiment. The base component100comprises a bone-facing surface120on which are provided one or more stem connectors160configured to receive and form connections with the one or more modular tibia stems200inserted from the bone-facing surface side. The base component100also includes side surfaces150and155.

Referring toFIG.1F, in some embodiments, each of the one or more modular stems200comprises a shaft portion210and a connecting portion220. The connecting portion forms the connection with one of the stem connectors160.

In some embodiments, the connecting portion220of the modular stems200can be configured with a male-type tapered surface, and each of the stem connectors160is configured as a recess having a female-type tapered sidewall surface that forms a friction lock connection with the connecting portion220. As shown, the stem connector160comprises a blind hole162that has a complementary tapered sidewall surface forming the female-type tapered sidewall surface that engage with the male-type tapered surface of the connecting portion220.

In some embodiments, the assignment of the male-type tapered surfaces and the female-type tapered surfaces can be reversed. For example, each of the stem connectors160can be configured as a post with a male-type tapered surface, and the connecting portion220of each of the one or more modular stems200can be configured as a recess having a female-type tapered sidewall surface that form the friction lock connection with one of the stem connectors160.

In some embodiments, the male-type tapered surfaces and the female-type tapered surfaces referenced herein are configured as Morse taper surfaces forming the friction lock connections. Friction lock connections have proven to be highly reliable, and that the two locking surfaces can be configured to form a very tight joint with typically smaller than 1 micron gap. Compared to connection systems that are joined by screws, tapered friction lock connections are more robust in withstanding stress and can better prevent loosening.

In the embodiments where the connecting portion220and the stem connector160form friction lock connections via cooperation of the above-mentioned tapered surfaces, for purposes of later revision or removal, the female-type tapered sidewall surface can be configured with one or more holes and the male-type tapered surface can be configured with a ramp-like structure for each of the one or more holes that are configured to enable disconnecting the friction lock connection.FIG.5Cshows a schematic example of a close up view of such structures. As an example, the annular sidewall of an embodiment of the stem connector160that has the female-type tapered surface that is connected to a male-type tapered surface of a stem200is shown. A hole H provided on the annular sidewall of the stem connector160is illustrated. The ramp-like structure provided on the stem200comprises a slanted surface S. When the friction lock connection is formed, each of the ramp-like structure would be aligned with each of the one or more holes in the female-type tapered sidewall.FIG.5Cshows a schematic close up view of the ramp-like structure aligned with the hole H provided on the annular sidewall of the stem connector160. The slanted surface S of the ramp-like structure is oriented such that when a wedge W is driven into the hole H in the direction of the arrow A, the slanted surface WS of the wedge W operates on the slanted surface S of the ramp and pushes the stem200in the direction of the arrow B. This cooperation of the wedge W and the slanted surface S of the ramp-like structure pushes the two friction locked structures160and200apart and disconnect the friction lock connection.

In some embodiments, the connecting portion220has a diameter not greater than the diameter of the shaft portion210. As will be discussed below in connection withFIGS.2G-2I, because the modular stem200is inserted through a hole H drilled into a long bone, with the connecting portion220leading, to reach the receiving stem connector160in the base component100that is attached to the terminal end (can be proximal end or a distal end depending on the particular long bone of a joint involved) of the long bone, limiting the diameter of the connecting portion220to be not greater than the diameter of the shaft portion210, allows the hole H drilled into the long bone to be kept substantially the same size as the diameter of the shaft portion210of the stem200. This produces minimum space between the shaft portion210and the sidewall of the hole H so that once the stem200is situated inside the hole H, the stem200is snuggly fit within the long bone. This snug fit would be beneficial for securely joining the base component100to the long bone. The arrow D inFIG.21shows the inserting direction of the modular stem200in the hole H in the long bone.

In some embodiments, the diameter of the shaft portion210can vary throughout its length if desired. In some embodiments, the shaft portion210can have a constant diameter.

Referring toFIG.1I, in some embodiments, the connecting portion220of the modular stem200can be configured with a male-type screw thread and each of the stem connectors160is configured as a recess or a blind hole162having a corresponding female-type screw thread that forms a threaded connection with the connecting portion220.

In some embodiments, the shaft portion210can be fully or partially configured with a male-type screw thread. The male-type screw thread on the shaft portion210can be a cortical-style bone screw thread or a cancellous-style bone screw thread. The provision of bone screw threads at the bone/stem interface could enhance the fixation of the implant in the surrounding bone. Bone threads can also allow for applying a compression of the tibia base component to the resected tibia bone.

In some embodiments, each of the stem connectors160can be configured as a post with a male-type screw thread, and the connecting portion220of each of the one or more modular stems200can be configured as a recess having a corresponding female-type screw thread that forms a threaded connection with one of the stem connectors160.

The male-type screw threads and the female-type screw threads mentioned above would be tapered screw threads where the corresponding structures involved have tapered surfaces. Otherwise, the screw threads can be straight (non-tapered) screw threads.

In some embodiments, each of the one or more modular stems200has a longitudinal axis L and each of the one or more stem connectors160has a longitudinal axis LL, and when the connection is formed between one of the one or more modular stems200and one of the one or more stem connectors160, the longitudinal axis L of the one modular stem and the longitudinal axis LL of the corresponding stem connector160coaxially align. Where the stem connector160is configured as a recess structure with an annular wall that extends from the bone-facing surface120, the cylindrical shape of the annular wall defines the longitudinal axis LL of the stem connector160.

In some embodiments, the one or more stem connectors160are independently oriented so that their respective longitudinal axes LL are oriented at different angles with respect to the bone-facing surface120.

Referring toFIG.1G, each of the one or more modular stems200can optionally comprise an alignment feature230provided at an end of the shaft portion210that is away from the connecting portion220to assist in aligning a stem seating tool500with the stem200described in more detail in connection withFIGS.3A-3D. In some embodiments, the alignment feature230can be a dimple, a slot, a raised bump, etc. to facilitate alignment of the seating tool500. In some embodiments, the alignment feature230can be an elongated dimple or a hole and coaxially aligned with the longitudinal axis L of the modular stem200as shown inFIG.1Gto help align the seating tool500.

Referring toFIGS.1H,1I,4B, and5A, according to another aspect, the base component100comprises a lower surface130that is opposite the bone-facing surface120. A second alignment feature135can be provided on the lower surface130for each of the one or more stem connectors160. Similar to the alignment feature230, the second alignment feature135can be any feature that can facilitate locating and aligning the seating tool500. The second alignment feature135can be one or more recesses (i.e. dimples), grooves, raised bumps, etc. Preferably, the second alignment feature135is coaxially aligned with the longitudinal axis LL of the corresponding stem connector160to assist with aligning the longitudinal axis L of the stem200to the longitudinal axis LL of the corresponding stem connector160, using the stem seating tool500along the longitudinal axes LL. When the stem200and the corresponding stem connector160are aligned so that their longitudinal axes L and LL are coaxially aligned, the aligned longitudinal axes L and LL define an assembly axis for the pair of modular stem and the corresponding stem connector.

In some embodiments, the second alignment feature135can have a spherical recess conformation which can allow alignment of multiple modular stems200that may be colinear or nearly colinear with the centerpoint of the spherical recess such that the seating tool500can be located to one position, and aligned to multiple insertion angles for each of the modular stems200.

Referring toFIGS.1A-1E,1H,1I, and5B, for example, in some embodiments, the base component100can further comprise one or more additional fixation features140such as fins, pegs, bosses, bars, etc. protruding from the bone-facing surface120. In the illustrated example, the additional fixation features140are fins. The additional fixation features140are configured to engage a bone surface and enhance the stability of interface between the base component100and the bone surface when the base component100is seated against the bone surface. The bone surface would usually be a prepared surface. For example, in embodiments where the bone-facing surface120of the base component100is engaging a tibia, the bone surface can be a resected tibia surface.

The example base component100shown inFIG.1Ais configured to receive two modular stems200and the stems are angled such that when the base component100is applied to a resected surface of the distal end of a tibia, the modular stems200allow for some proximal stabilization within the metaphysis of the tibia. The angle of the stems200determine how much cortical bone would need to be removed when drilling holes in the tibia for the modular stems200. If the angle of the holes is more vertical, the holes through the cortex become elongated ellipses, thus sacrificing additional bone material. If the angle is shallower, however, that would result in a shorter stem, and therefore less stabilization in the bone.

The angle of the modular stems200in the axial (top-down) view also determines where the stem holes should be located in the long bone, such as a tibia. The two stems200shown inFIG.1Aare largely angled in the anterior direction, but they can be configured to be angled toward the medial direction, posterior direction, or lateral direction.

In the example where the base component100is being applied to the distal end of a tibia, the cross-section of the tibia in the region where the modular stems would enter to reach the tibia base component100is roughly triangular with a vertex of the triangle in the anterior direction. Therefore, splaying the two modular stems200to the sides (medial and lateral) can avoid the anterior ridge of the tibia cortex.

Referring toFIGS.1C and1D, when the modular stems200are connected to the respective stem connectors160, the longitudinal axis L of the stems are coaxial with the longitudinal axis LL of the stem connectors. As the modular stems200are to engage the stem connectors160from the medial direction, the modular stems200will be introduced into the medullary canal of the tibia via holes H drilled into a side of the tibia at an angle as will be discussed below in connection withFIGS.2G-2I. The angle of the holes H drilled into side of the tibia is best defined with respect to the resected distal surface DS (seeFIGS.2C and2D) at the distal end of the tibia because the bone-facing surface120of the base component100will contact the resected distal surface DS and the angular orientation of the stem connectors160are defined with respect to the bone-facing surface120.

The angular orientation, i.e., the tilt angle, of a stem connector160is defined by the longitudinal axis LL of the stem connector160. This tilt angle will be referred to as β. When the modular stem200is properly engaged with the stem connector160, the longitudinal axis L of the modular stem200will be coaxial with the longitudinal axis LL of the stem connector160and, thus, the tilt angle of the installed tibia modular stem200with respect to the bone-facing surface120will also be the tilt angle β. In the implanted position, the bone-facing surface120of the base component100is intended to be in contact with the resected distal surface DS of the tibia. Therefore the angle of the holes H drilled into the side of the tibia for the modular stems200would match the tilt angle β with respect to the resected distal surface DS.

Referring toFIGS.1C and1D, the angular orientation of the stem connector160tilted by the tilt angle β, which will be the same tilt of the modular stem200that engages the stem connector160, can also be described by two angular components, βA-Pidentified inFIG.1Cand βM-Lidentified inFIG.1D. The angular component βA-Pis the angle with respect to the bone-facing surface120in the anterior-posterior direction and will be referred to herein as the A-P angle βA-P. The angular component βM-Lis the angle with respect to the bone-facing surface120in the medial-lateral direction and will be referred to herein as the M-L angle βM-L.

Referring toFIGS.2A-2F, before the base component100can be implanted into the tibia, the distal end of the tibia is resected with the help of an appropriate guide instrument to prepare a joint space50. Then, a reamer60can be used to form appropriately located recesses R in the resected distal surface DS of the tibia in the joint space50to accommodate the stem connectors160that protrude from the bone-facing surface120of the base component100.

Next, referring toFIGS.2G-2I, holes H are drilled into the tibia from the proximal side for inserting the modular stems200. Each hole H is oriented so that the hole is coaxial with the longitudinal axis LL of the corresponding stem connector160. The drill bit may be aligned using an external fixture and guide system which also sets the tibial resection cuts in the joint space50for fitting the base component100. In an alternative embodiment, the drill bit may be aligned with patient bone scan registration, robotic arms, and/or computer process assisted surgery with visual guidance. Depending on the needs of the patient, the surgeon would determine the number, length, and orientation of the modular stems200that would be required to appropriately secure the base component100to the tibia. The base component100can be offered with a variety of configurations to choose from. The variable features being the number of stem connectors, and the orientation of each of the stem connectors160. The orientation of the stem connectors would be defined by the A-P angle βA-Pand the M-L angle βM-L.

After the holes H are drilled into the tibia, a desired modular stem200of appropriate length is inserted into the hole H from the proximal direction indicated by the arrow D inFIG.2Ito engage with a stem connector160in the base component100.

For the embodiment where the connecting portion220of the modular stems200and the blind hole162of the stem connectors160have complementary Morse tapered surfaces, the modular stem200can be tapped into the stem connector160using a punch as one does with a carpentry nail.

In some preferred embodiments, however, the engagement of the modular stem200to the stem connector160can be achieved using a stem seating tool500shown inFIGS.3A-3D. The seating tool500is similar to a channel lock style plier. The seating tool500comprises two handles510a,510bfor actuating the tool pivotally connected by a pivot joint520, and a clamping end530that clamps an assembly of a modular stem200and a base component100to press the two components together to form the friction lock connection. The clamping end530is formed by a pair of jaws, a first jaw531a, and a second jaw531bthat are configured to oppose each other so that they can capture a modular stem200/stem connector160assembly between the pair of jaws and axially compress the modular stem200and the stem connector160together in line with the assembly axis (i.e., the longitudinal axes L and LL in alignment) to form the friction lock connection. As mentioned above, the alignment feature230that can be provided on the modular stem200and the second alignment feature135that can be provided on the lower surface130of the base component100facilitate alignment of the seating tool500with the modular stem200.

As shown inFIGS.3A(inset),3B, and3D, the pair of jaws531a,531bare configured to clamp the modular stem200/stem connector160assembly from the two ends of the assembly and axially compress them until the connecting end220of the modular stem200and the blind hole162are properly engaged to form a friction lock connection. The first jaw531ais provided with a bump or a protrusion532athat is sized to fit into the alignment feature230of the modular stem200. The second jaw531bis provided with a bump or a protrusion532bthat is sized to fit into the second alignment feature135on the lower surface130of the base component100. The protrusions532aand532bcan be simply spherical bumps or they can be elongated protrusions. In embodiments where the protrusions532aand532bare elongated protrusions, their extensions are oriented along an axis LLL so that they are axially aligned along the axis LLL as shown inFIG.3A. That alignment facilitates axially clamping the modular stem200/stem connector160assembly.

Because the tool500needs to engage the base100that is situated within the joint space50and the modular stem200that is inside a hole H in the tibia, the two opposing protrusions532a,532bare oriented so that the axis LLL defining their alignment is at an angle β′ with respect to the plane P2that represents the plate of the bone-facing surface120of the base component100. Preferably, the angle β′ matches the tilt angle β of the modular stem200as it engages the stem connector160. As described above in connection withFIGS.1C and1D, the tilt angle β is defined by the longitudinal axis LL of the stem connector160. This relationship is illustrated inFIG.3AandFIG.3D. It should be noted that the working end of the jaw531ahaving the protrusion532ais shown partially sectioned along with the modular stem200.

The lengths of the protrusions532a,532bcan be provided to be any desired length. Particularly, the protrusion532aprovided on the first jaw531a, which is intended to engage the alignment feature230on a modular stem200after the modular stem200is inserted into the hole H in the long bone, is configured to have a length long enough to reach the end of the modular stem200that may be at some depth into the hole H. In some embodiments, the tip portion of the first jaw531awhere the protrusion532ais provided can be made to be modular so that a tip portion having a desired length protrusion532acan be selected from a variety of sizes.

In some embodiments, the end of the shaft portion of the modular stem200may not be equipped with any recessed alignment feature230. The end of the modular stem200can be a stub and the tip of the first jaw531acan be configured with a concave cap-like structure that engages the stub end of the modular stem200to exert a compression force.

In some embodiments, the friction lock connection forming structures of the modular stem200and the base100can be reversed. In other words, the male-type tapered component can be provided on the base100and the connecting portion220of the modular stem200can be provided with a corresponding female-type tapered structure.

In some embodiments, the surface of the modular stems200can be prepared as rough, porous for promoting bone on-growth, splined, threaded or smooth. In the illustrated examples, t shaft portion210of the stems200are cylindrical, but in some embodiments, they can be configured to have non-circular cross-section to achieve selective press-fit.

In some embodiments, the stems200can be structured more like fins rather than cylinders to spare more bone in the long bone.

In some embodiments, the stems200can have a crucifix cross-section. In some embodiments, the stems200can be non-symmetric about the drill axis, such as square, or triangular/prismatic. In some embodiments, the stems200can be hollow with perforations in the cortex to allow for injecting bone cement or bone graft substitute material outward from the core of the stem.

In some embodiments, the stems can be shorter than the length of the holes H drilled into the long bone so that the proximal end of the stems200are recessed from the exterior cortex surface of the long bone when installed into the base component100. In other embodiments, the stems can be selected to have a length so that their proximal ends are flush with the exterior cortex surface of the long bone. Pegs interacting with the cortex could provide greater robustness to the stability. In other embodiments, the proximal ends of the stems can be proud of the exterior cortex surface of the long bone. In some embodiments, the proud portion of the stem can have a washer or a head feature. The head feature can be a threaded screw head so that they can provide compression to the distally located base component100. If the pegs were flush or proud of the cortical bone, this could also facilitate later revision, removal, etc.

Accordingly, a method for implanting the base component100for a joint replacement prosthesis onto an end of a long bone can comprise: preparing the end of the long bone in a joint to receive the base component100; drilling one or more holes H into the long bone from a side, wherein each hole H is oriented so that the hole H is coaxial with the longitudinal axis LL of one of the one or more stem connectors; inserting a modular stem200into one of the one or more holes H to engage with one of the one or more stem connectors160in the base component100; and axially compressing the modular stem200and the stem connector160together to form a connection between the modular stem200and the stem connector160. Preferably, the connection between the modular stem200and the stem connector160is a friction lock connection.

Referring toFIG.1K, for the embodiments where the connecting portion220of the modular stem200aand the blind hole162of the stem connector160are configured with screw threads for threaded engagement. The modular stem200acan be threaded into the stem connector160. To turn the modular stem200afor threading, the alignment feature230provided at the end of the modular stem200aopposite from its connecting portion220can be configured to receive a screw driver. In the example shown inFIG.1K, the alignment feature230is configured as a hexagonal shaped recess to receive a male type hex driver but the alignment feature230can be configured for any of the known drive mechanism, such as, star-shaped drive, hexalobe drive, philips or crosshead drive, square drive, slotted drive, etc. For accommodating a revision procedure, the threaded connection between the modular stem200and the base component100might be favored. For this embodiment, after the modular stem200ais inserted into the hole H in the long bone, the screw driver would be inserted into the hole H from the side of the long bone to reach the modular stem200aand turn the modular stem200afor threadedly engaging the corresponding stem connector160in the base component100.

FIG.4Ais an illustration showing a sectioned view of a base component100and modular stem200assembly in an as-implanted state. The modular stem200is engaged with the stem connector160of the base component100.FIGS.4B-4Care illustrations of various examples of base/modular stem configurations that can be implemented to the distal end of a tibia according to some embodiments.

FIGS.4D-4Fare illustrations showing a variation in the configuration of the hole H drilled into a long bone. In the example illustrated here, the hole H does not have a constant diameter throughout its length. Rather, the hole H has two portions each having a different diameter. As shown, the portion of the hole H that receives a stem200has one diameter that can accommodate the diameter of the stem200. The portion of the hole H that exits through the cortical bone along a side of the long bone, however, can have a smaller diameter so that the opening in the cortical bone of the long bone is small. This may be desired depending on the condition of the cortical bone along the side of the long bone or where preserving the cortical bone as much as possible is desired.

In this embodiment, unlike in the embodiment shown inFIG.2I, because the opening for the hole H in the long bone is too small to insert the stem200, the stem200is inserted from the opposite end of the hole H first, before the base component100is brought in position. Then, the stem seating tool500can be used in the same manner as shown inFIG.3Bto coaxially compress the stem/base assembly.

In some other embodiments, the structural configurations that enable the modular stems to connect with the base component can be reverse of those of the embodiments described above. For example, referring toFIGS.5A-5B, in these embodiments, a base component100A can comprise one or more tapered posts160A provided on its bone-facing surface120A, where the tapered posts160A are configured to receive and form connections with the one or more modular stems200A introduced from the bone-facing surface side120A. Correspondingly, each of the one or more modular stems200A is configured to form the connection with one of the tapered posts160A. The base component100A also includes side surfaces150A and155A.

In some embodiments, each of the one or more modular stems200A comprises a shaft portion210A and a connecting portion220A and the connecting portion220A includes a recess222A that forms the connection with one of the one or more tapered posts160A by receiving the tapered post therein. In some embodiments, the recess222A comprises a tapered sidewall surface that forms a friction lock engagement with one of the tapered posts160A. In some embodiments, the taper on the tapered posts160A and the taper on the tapered sidewall surface of the recess222A are Morse tapers.

In some embodiments, the connecting portion220A on each of the modular stems200A has a stem connector configured with a female-type screw thread and each of the tapered posts160A includes a corresponding male-type screw thread.

Similar to the base component100, in some embodiments, the base component100A can further comprise one or more additional fixation features140A such as fins, pegs, bosses, bars, etc. protruding from the bone-facing surface120A. In some embodiments, the connecting portion220A has a diameter not greater than the diameter of the shaft portion210A.

In some embodiments, each of the one or more tapered posts160A is independently oriented so that their respective longitudinal axes LLA are oriented at different angles with respect to the bone-facing surface120A.

The seating tool500can be used to seat the modular stems200A onto the tapered posts160A in the similar manner as used in conjunction with the base component100and the modular stems200as described herein.

According to some embodiments, the modular stems can be cannulated. For illustration purposes, the cannulation feature205A is shown in the example modular stem200A inFIG.5Abut the cannulation is not required to be present along with other features of the modular stem example200A, such as the recess222A. In other words, the modular stem example200shown inFIG.1Fcan be configured with a cannulation. Using such cannulated modular stems can facilitate a surgical technique where a guide pin such as Steinmann pins could be used to assist in establishing the trajectory of the modular stems and confirming the trajectory of the stem paths through the tibia to reach the base component100,100A. This can enhance the expectation of the convergence of the modular stems with the intended stem connectors.

The tubular sidewall of such cannulated stem may be perforated. The modular stem200A inFIG.5Ais shown with perforations206A along its tubular sidewall. The provision of the perforations206A allow bone cement or alternative material to be delivered through the cannulation205A of the stem and out through the perforations206A into the space around the stem200A in the patient's bone. This would allow bone cement to fill any gaps between the stem and the surrounding bone, filling voids within the bone. A flowable cement such as PMMA bone cement, or bone graft substitute, either biological or synthetic, or a combination thereof may be used. In some embodiments, a nozzle attachment feature207A can be provided at the end of the cannulated modular stem200A to attach a syringe or some other similar cement delivery vessel.

According to some embodiments, the tip of the modular stems200,200A on the end opposite from the connecting portion220,220A can be shaped to be more accommodating to the geometry of the bone. For example, the end of the modular stem can be configured to have a generous radius (fillet) along the edge to spread the load. An example of this edge208A is illustrated inFIG.5A. A more exaggerated broader shape such as a chamfer from one view, with a broad oblique surface matching the shape of the endosteum of the bone at that level could be an option for the design. This would broaden the surface contact between the tip of the modular stem200,200A and the endosteum of the bone cortex.

Additionally, when the joint replacement prosthesis of the present disclosure is implanted in the patient, the modular stems200,200A do not need to be completely contained within the endosteum space. The stems could be long enough to reach a level where they could interact with the cortical bone, or fill the void left in the cortex that resulted from the drill. The tip of the modular stem could even protrude from the surface of the cortex. The modular stem interacting with the cortex could provide greater robustness to the stability. If the modular stems were protruding from the cortex, this could also facilitate later revision, removal, procedures, etc.

According to another aspect of the present disclosure, in some embodiments of the base component100,100A, at least some portions of the surfaces of the base component100,100A that come in contact with bone can be coated with a coating that promotes bone in-growth. An example of such coating material is a porous metallic coating ADAPTIS™ by Wright Medical Technology. On the base component100, the surfaces such as the bone-facing surface120,120A, side surfaces150,155,150A,155A, the outer surfaces of the stem connectors160, the outer surfaces of the tapered posts160A, and the surfaces of the fins140,140A are examples of the surfaces that can come in contact with bone.

Although the subject matter has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art.