Magnetic locking mechanism (MLM) for joint arthroplasty

A method of implanting a joint prosthesis assembly for joint arthroplasty using a coupling mechanism is disclosed. The method includes exposing a joint of a patient, resecting a portion of the joint, inserting a second prosthesis of the joint prosthesis assembly into a medullary canal, and inserting a first prosthesis of the joint prosthesis assembly from a lateral side of the joint. The joint prosthesis assembly includes a magnet. The magnet is configured to lock the first prosthesis of the joint prosthesis assembly to the second prosthesis of the joint prosthesis assembly. The first prosthesis of the joint prosthesis assembly includes a recess. The second prosthesis of the joint prosthesis assembly includes a protrusion. The recess is configured to house the protrusion. Alternatively, the first prosthesis and the second prosthesis may be assembled in a direct line using the magnet for secure coupling of the components.

FIELD OF THE DISCLOSURE

The present disclosure is generally related to an implantable joint prosthesis assembly for joint arthroplasty, e.g., a magnetic locking mechanism for joint arthroplasty modular components.

BACKGROUND

A number of mechanisms may be used for coupling head and stem components in joint arthroplasty procedures, the most common being the Morse taper mechanism, which typically requires a wide exposure of a subject joint to allow for a direct line for tamping of the head onto the stem. However, this kind of wide exposure is not always possible. For example, in the case of radial head arthroplasty, the capitellum may interfere with a direct line access to the radial head. In revision surgery with extensive scar tissue, this can become even more challenging. In addition, the direct impaction of the head onto the stem may have inherent risk of iatrogenic fracture in the patient or damage to the prosthesis, and there is no mechanism for assessing the locking of the head to the stem. Furthermore, if the articulation of the prosthesis is off or loosens or dislodges, progressive loosening may occur with ultimate complete disarticulation. Alternatively, the Morse taper assembly may be performed outside the joint, but doing so requires the surgeon to then insert the entire assembly as one large component. The Morse taper mechanism fails to meet certain needs of the industry as it is not appropriate for minimally invasive joint arthroplasty.

SUMMARY

In at least one example embodiment, an implantable joint prosthesis assembly for joint arthroplasty includes a first prosthesis having a recess, a second prosthesis having a protrusion, and a magnetic prosthesis configured to connect the first prosthesis to the second prosthesis. The recess is configured to house the protrusion. The magnetic prosthesis is disposed between the first prosthesis of the joint prosthesis assembly and the second prosthesis of the joint prosthesis assembly.

In at least one other example embodiment, a method of implanting a joint prosthesis assembly for joint arthroplasty includes exposing a joint of a patient, resecting a portion (e.g., head) of the joint, inserting a second prosthesis of the joint prosthesis assembly into a medullary canal, and inserting a first prosthesis of the joint prosthesis assembly from a lateral side of the joint. In accordance with such example embodiment, the joint prosthesis assembly includes a magnet that is configured to lock the first prosthesis to the second prosthesis. Further, the first prosthesis includes a recess, the second prosthesis includes a protrusion, and the recess is configured to house the protrusion.

Embodiments disclosed herein provide reliable and reproducible locking of two modular components of a joint prosthesis assembly in joint arthroplasty. The embodiments allow for two modular components of a joint prosthesis assembly to be locked in a small anatomic space, thus providing a joint prosthesis assembly to be biocompatible and safely inserted and utilized inside a patient's anatomy. Also embodiments disclosed herein provide a joint prosthesis assembly that is easy to apply while avoiding human error when coupling prosthetic components of the joint prosthesis assembly. Accordingly, at least some of the embodiments disclosed herein advantageously fill industrial needs by providing an implant coupling mechanism that is strong, durable, easy to use, and reproducible in a surgeon's hands.

DETAILED DESCRIPTION

FIG. 1shows an implantable joint prosthesis assembly100for joint arthroplasty having a first prosthesis101with a recess102and a second prosthesis105with a protrusion106, according to at least one example embodiment described herein. In at least one embodiment, the first prosthesis101may be a radial head prosthesis that includes a recess102. The recess102may be of any suitable size to fit within the first prosthesis101and/or any shape suitable (square, rectangle, circle, ellipse, triangle, cube, cuboid, spherical, half-spherical, prism, etc.) to match the shape of the protrusion106of the second prosthesis105. As shown in the example embodiment ofFIG. 1, the recess102is a pillar shape with a square opening. The first prosthesis101also includes a marker103for alignment with the second prosthesis105. The first prosthesis101may include any durable and/or composite materials such as chrome, pyrocarbon, cobalt-chrome alloy, other metal alloy, etc., suitable to extend the lifespan of the implantable.

In at least one example embodiment, the second prosthesis105may be a prosthetic stem and/or a radial stem that includes a stem portion107and a protrusion106. The second prosthesis105may include, e.g., a rough grit-blast material. It will be appreciated that grit-blast material promotes bony on-growth and facilitates osseous integration. The second prosthesis105may have a plasma coating or may be a polished smooth stem. Further, the stem portion107of the second prosthesis105may be of any suitable shape (straight, fluted, curved, etc.) and may be of any suitable/varying lengths and/or any sizes suitable to match the shape/length/size of the canal of the joint where the stem portion107may be inserted. The protrusion106may be a collar and/or a peg. The protrusion106may include any suitable ferromagnetic metal(s).

The joint prosthesis assembly100may also include a magnetic prosthesis104that may be or include rare-earth magnet(s). It will be appreciated that rare-earth elements are metals that are ferromagnetic and may be magnetized to become permanent magnets; that rare-earth magnets refer to strong permanent magnets made from alloys of rare-earth elements; and that rare-earth magnets may be the strongest type of permanent magnets, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets. For example, a magnetic field typically produced by rare-earth magnets may exceed 1.4 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. The magnetic prosthesis104may include at least one of the two types of rare-earth magnets: neodymium magnets and samarium-cobalt magnets. Stronger rare-earth magnets may allow smaller magnets to be incorporated into existing prosthetic joint designs. Larger sizes would be necessary with traditional magnets, limiting their incorporation into prosthetic joint designs. The neodyminum, specifically N-52, is the strongest commercially available magnet.

Rare-earth magnets may be extremely brittle and also vulnerable to corrosion, so they are typically plated or coated to prevent breaking, chipping, or crumbling into powder. For use in a joint prosthesis assembly, rare-earth magnets are utilized in at least some of the example embodiments described herein to promote bony on-growth.

The magnetic prosthesis104may be inserted inside the first prosthesis101. That is, the magnetic prosthesis104may be inserted into any head of a prosthesis with suitable shape and/or size. In at least one example embodiment, the magnetic prosthesis104is inserted in the recess102. In at least one other example embodiment, the magnetic prosthesis104is inserted in the first prosthesis101and the recess102is formed in the magnetic prosthesis104(see e.g.,FIG. 2C). The recess102may be disposed at any location (e.g., in the middle) on the first prosthesis101or on the magnetic prosthesis104suitable to match the location of the protrusion106of the second prosthesis105relative to the joint prosthesis assembly100.

The protrusion106may be shaped to couple the recess102of the first prosthesis104. For example, the magnetic prosthesis104may be inserted in the recess102, or the recess102may be formed in the magnetic prosthesis104. The shape and/or size of the protrusion106may match the shape and/or size of the recess102to facilitate, e.g., the magnetic prosthesis104being inserted in the recess102or the recess102being formed in the magnetic prosthesis104. The first prosthesis101and the second prosthesis105are connected by the polarity of the rare-earth magnet pulling the ferromagnetic metal into the recess102. The protrusion106(e.g., a collar and/or a peg) of the second prosthesis105may articulate with the first prosthesis101.

In an operation, once the protrusion106is engaged into the recess102, with the magnetic prosthesis104being inserted in the recess102or the recess102being formed in the magnetic prosthesis104, a magnetic bond may be formed and the protrusion106may be pulled into the recess102by the magnetic forces. In another embodiment, the magnetic prosthesis104may be disposed on the protrusion106and coupled into the recess102of the first prosthesis101. In such embodiment, the first prosthesis101may include ferromagnetic metal(s) to create a magnetic bond between the protrusion106(where the magnetic prosthesis104is disposed) and the first prosthesis101.

InFIG. 1, the square shape of the recess102and the square shape of the protrusion106may prevent radial rotation of the first prosthesis101relative to the second prosthesis105in clinical situations. The marker103on the first prosthesis101and the marker108on the second prosthesis105are provided to, e.g., ensure proper alignment during an implant procedure. For example, during the implant procedure, when the first prosthesis101and the second prosthesis105are assembled, e.g., when the protrusion106is inserted into the recess102and/or the magnetic prosthesis104locks the first prosthesis101and the second prosthesis105, if the marker103and the marker108are on a same line in a axial direction, the first prosthesis101is aligned with the second prosthesis105. If the marker103and the marker108are not on a same line in the axial direction, adjustments need to be made (e.g., via an alignment tool (not shown)) to ensure the first prosthesis101is aligned with the second prosthesis105.

In accordance with the magnetic locking mechanism disclosed herein, loosening may not occur as magnets have an average lifespan of about 100 years. Any temporary minor separation of the magnet from the ferromagnetic metal would immediately lock back in place from the pull of the magnet against the ferromagnetic metal.

In at least one example embodiment, the magnetic locking mechanism in the implantable joint prosthesis assembly100for joint arthroplasty may include the magnetic prosthesis104(e.g., magnet(s) such as rare-earth magnet(s)) that may be coupled to the first prosthesis101(e.g., ferromagnetic metal(s)), and/or the second prosthesis105(e.g., ferromagnetic metal(s)) used in joint arthroplasty.

In at least one other example embodiment, the magnetic prosthesis104may be disposed/inserted in the first prosthesis101(e.g., a radial head) or the second prosthesis105(e.g., a radial stem) or the protrusion106(e.g., collar and/or peg, etc.) of the second prosthesis105.

In at least one other example embodiment, the magnetic prosthesis104may be connected to the first prosthesis101(e.g., a ferromagnetic metal head) and/or the second prosthesis105(e.g., a ferromagnetic metal stem) by its polarity, and/or may be directly welded into the first prosthesis101or the second prosthesis105.

In the example embodiment ofFIG. 1, the magnetic prosthesis104is welded into the first prosthesis101(e.g., a radial head). The composite radial head (first prosthesis101in which the magnetic prosthesis104is welded) may then be coupled to the second prosthesis105(e.g., a radial stem having a ferromagnetic metal collar and/or peg (of the protrusion106)). By providing a recess102in the first prosthesis101(e.g., a radial head), the protrusion106(e.g., a metal collar and/or peg) may articulate tightly into the recess102in the first prosthesis101(e.g., a radial head) and form a magnetic bond with the magnetic prosthesis104. The square shape of the recess102also allows for exact orientation of the first prosthesis101(e.g., a radial head) relative to the second prosthesis105(e.g., a radial stem).

In accordance with at least one example embodiment, the magnetic locking mechanism may include a magnet (e.g., a rare-earth magnet) inserted into a hollowed head prosthesis including a ferromagnetic metal. The composite head (head with magnet inserted) may articulate with a stem prosthesis (that includes a ferromagnetic metal). The magnet may be welded into the head prosthesis and then articulated with the stem prosthesis together.

In another example embodiment, the magnet may be part of the stem prosthesis either by a magnetic bond or welding. The composite magnetic stem (stem with magnet bond/welded) may then be articulated with a ferromagnetic metal head.

In yet another example embodiment, a magnetic collar and/or peg (of a protrusion including rare-earth magnet material) may be disposed on a prosthetic stem, and an augment (not shown) may be added to the collar and/or the peg that is ferromagnetic. For example, the augment may be a layer of coating. Embodiments disclosed herein may be used for radial head arthroplasty. However, it will be appreciated that the magnetic locking mechanism disclosed herein may also be used in other joints including total shoulder arthroplasty, wrist arthroplasty, ankle arthroplasty, small joint arthroplasty in the hands and feet, as well as knee and hip arthroplasty, etc. The magnet locking mechanism disclosed herein allows for any components of implant devices to be coupled easily with a secure and lasting bond and allows for ease of increasing modularity of current joint prosthetic designs as adding head, collar, peg, and/or stem components would be easier without complex design features (e.g., screw fixation).

FIGS. 2A-2Cshow implantable joint prosthesis assemblies200,210, and220for joint arthroplasty, according to some example embodiments. As shown inFIG. 2A, the joint prosthesis assembly200includes a first prosthesis201and a second prosthesis205. The first prosthesis201includes a recess202and a marker203.

The second prosthesis205includes a stem portion207and a protrusion206. The joint prosthesis assembly200includes a magnetic prosthesis204, which may be inserted or welded in the recess202. In another example embodiment, the magnetic prosthesis204may be inserted or welded in the first prosthesis201and the recess202may be formed in the magnetic prosthesis204(see e.g.,222and224). In yet another example embodiment, the magnetic prosthesis204may be disposed on the protrusion206and coupled into the recess202of the first prosthesis201. The marker203on the first prosthesis201and the marker208on the second prosthesis205may be utilized to ensure proper alignment during an implant procedure.

As shown inFIG. 2B, the assembled joint prosthesis assembly210includes a first prosthesis211and a second prosthesis215. The first prosthesis211includes a recess (not shown). The first prosthesis211also includes a marker213. The second prosthesis215includes a stem portion217and a protrusion (not shown). The joint prosthesis assembly210also includes a magnetic prosthesis (not shown). In at least one example embodiment, the magnetic prosthesis is inserted or welded in the recess. In another example embodiment, the magnetic prosthesis is inserted or welded in the first prosthesis211and the recess is formed in the magnetic prosthesis (see e.g.,222and224). In yet another example embodiment, the magnetic prosthesis may be disposed on the protrusion and coupled into the recess of the first prosthesis211. The marker213on the first prosthesis211and a marker (not shown) on the second prosthesis215may be utilized to ensure proper alignment during an implant procedure.

FIG. 2Cshows a cross-sectional view of the assembled joint prosthesis assembly220, which includes a first prosthesis221and a second prosthesis225. The first prosthesis221includes a recess222and a marker (not shown). The second prosthesis225includes a stem portion227and a protrusion226. The joint prosthesis assembly220also includes a magnetic prosthesis224, which may be inserted or welded in the first prosthesis221, and the recess222may be formed in the magnetic prosthesis224. The marker on the first prosthesis221and a marker (not shown) on the second prosthesis225may be utilized to ensure proper alignment during an implant procedure.

It will be appreciated thatFIGS. 2A-2Cpertains to embodiments similar to the embodiment ofFIG. 1. For example, the structure and function of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 2A-2Care the same or similar to those of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIG. 1. However, as shown inFIGS. 2A and 2C, the recesses202and222are cylinder-shaped with a circular opening. The protrusions206and226(e.g., collar or peg) are also cylinder-shaped with a circular top surface, and match the size and shape of the recesses202and222, respectively. The cylinder shape of the recesses/protrusions may facilitate radial rotation of the protrusions inside the recess. The stem portion207is a cylinder shape. The cylinder shape of the stem portion may facilitate radial rotation of the stem portion inside the canal of the joint where the stem portion is inserted. InFIGS. 2B and 2C, the stem portions217and227have a tapered (e.g., triangle-shaped) end. The tapered end may be made of e.g., titanium or any suitable material (that has low density and high strength and is resistant to corrosion), and may be used to aid insertion.

FIG. 3shows a cross-sectional view of the joint prosthesis assembly300for joint arthroplasty implanted in an elbow joint, according to at least one example embodiment. The joint prosthesis assembly300includes a first prosthesis301and a second prosthesis305. The first prosthesis301includes a recess302and a marker (not shown). The second prosthesis305includes a stem portion307and a protrusion306. The joint prosthesis assembly300also includes a magnetic prosthesis304. In at least one example embodiment, the magnetic prosthesis304is inserted or welded in the recess302. In another example embodiment, the magnetic prosthesis304is inserted or welded in the first prosthesis301and the recess302is formed in the magnetic prosthesis304. In yet another example embodiment, the magnetic prosthesis304may be disposed on the protrusion306and couple into the recess302of the first prosthesis301. The marker on the first prosthesis301and a marker (not shown) on the second prosthesis305may be utilized to ensure proper alignment during an implant procedure.

It will be appreciated thatFIG. 3pertains to embodiments similar to the embodiments ofFIGS. 1 and 2. For example, the structure and function of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIG. 3are the same or similar to those of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 1 and 2.

FIGS. 4A and 4Bshow implantable joint prosthesis assemblies400and410for a total shoulder arthroplasty, according to at least some example embodiments. As shown inFIG. 4A, the assembled joint prosthesis assembly400(e.g., a total shoulder prosthesis) includes a first prosthesis401(e.g., a humeral head having a half-spherical shape) and a second prosthesis405(e.g., a humeral stem). The first prosthesis401includes a recess (not shown) and a marker (not shown). The second prosthesis405includes a stem portion407and a protrusion (not shown). The joint prosthesis assembly400also includes a magnetic prosthesis (not shown). In at least one example embodiment, the magnetic prosthesis is inserted or welded in the recess. In another example embodiment, the magnetic prosthesis is inserted or welded in the first prosthesis401, and the recess is formed in the magnetic prosthesis. In yet another example embodiment, the magnetic prosthesis may be disposed on the protrusion and couple into the recess of the first prosthesis401. The marker on the first prosthesis401and a marker (not shown) on the second prosthesis405may be utilized to ensure proper alignment during implant procedure. The joint prosthesis assembly400may also include a glenoid prosthesis409.

InFIG. 4B, the joint prosthesis assembly410includes a first prosthesis411and a second prosthesis415. The first prosthesis411includes a recess412and a marker (not shown). The second prosthesis415includes a stem portion417and a protrusion416. The joint prosthesis assembly410also includes a magnetic prosthesis414. In at least one example embodiment, the magnetic prosthesis414is inserted or welded in the recess412. In another example embodiment, the magnetic prosthesis414is inserted or welded in the first prosthesis411and the recess412is formed in the magnetic prosthesis414. In yet another example embodiment, the magnetic prosthesis414may be disposed on the protrusion416and coupled into the recess412of the first prosthesis411. The marker on the first prosthesis411and the marker (not shown) on the second prosthesis415may be utilized to ensure proper alignment during an implant procedure.

It will be appreciated thatFIGS. 4A and 4Bpertain to embodiments similar to the embodiments ofFIGS. 1-3. For example, the structure and function of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 4A and 4Bare the same or similar to those of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 1-3.

FIGS. 5A and 5Bshow implantable joint prosthesis assemblies500and510for ulnar arthroplasty, according to at least some example embodiments. As shown inFIG. 5A, the joint prosthesis assembly500(e.g., an ulnar prosthesis) includes a first prosthesis501(e.g., an ulnar head) and a second prosthesis505(e.g., an ulnar stem). The first prosthesis501includes a recess502and a marker (not shown). The second prosthesis505includes a stem portion507and a protrusion506. The joint prosthesis assembly500also includes a magnetic prosthesis504. In at least one example embodiment, the magnetic prosthesis504is inserted or welded in the recess502. In another example embodiment, the magnetic prosthesis504is inserted or welded in the first prosthesis501, and the recess502is formed in the magnetic prosthesis504. In yet another example embodiment, the magnetic prosthesis504may be disposed on the protrusion506and couple into the recess502of the first prosthesis501. The marker on the first prosthesis501and the marker (not shown) on the second prosthesis505may be utilized to ensure proper alignment during an implant procedure.

InFIG. 5B, the assembled joint prosthesis assembly510(e.g., an ulnar prosthesis) includes a first prosthesis511(e.g., an ulnar head) and a second prosthesis515(e.g., an ulnar stem). The first prosthesis511includes a recess (not shown) and a marker (not shown). The second prosthesis515includes a stem portion517and a protrusion (not shown). The joint prosthesis assembly510also includes a magnetic prosthesis (not shown). In at least one example embodiment, the magnetic prosthesis is inserted or welded in the recess. In another example embodiment, the magnetic prosthesis is inserted or welded in the first prosthesis511, and the recess is formed in the magnetic prosthesis. In yet another example embodiment, the magnetic prosthesis may be disposed on the protrusion and couple into the recess of the first prosthesis511. The marker on the first prosthesis511and the marker (not shown) on the second prosthesis515may be utilized to ensure proper alignment during an implant procedure.

It will be appreciated thatFIGS. 5A and 5Bpertain to embodiments similar to the embodiments ofFIGS. 1-4B. For example, the structure and function of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 5A and 5Bare the same or similar to those of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 1-4B.

FIGS. 6A-6Cshow implantable a joint prosthesis assembly600(in different view) for joint arthroplasty having a side loading mechanism with a screw locking mechanism, according to at least some example embodiments.

The joint prosthesis assembly600includes a first prosthesis601and a second prosthesis605. The first prosthesis601includes a recess602and a marker (not shown). The second prosthesis605includes a stem portion607and a protrusion606. The joint prosthesis assembly600also includes a magnetic prosthesis604. In at least one example embodiment, the magnetic prosthesis604is inserted or welded in the recess602. In another example embodiment, the magnetic prosthesis604is inserted or welded in the first prosthesis601, and the recess602is formed in the magnetic prosthesis604. In yet another example embodiment, the magnetic prosthesis604may be disposed on the protrusion606and couple into the recess602of the first prosthesis601. The marker on the first prosthesis601and the marker (not shown) on the second prosthesis605may be utilized to ensure proper alignment during an implant procedure.

It will be appreciated thatFIGS. 6A-6Cdescribes embodiments similar to the embodiments ofFIGS. 1-5B. For example, the structure and function of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 6A-6Care the same or similar to those of the first prosthesis, the recess, the marker of the first prosthesis, the magnetic prosthesis, the second prosthesis, the protrusion, the stem portion, and the marker of the second prosthesis inFIGS. 1-5B.

The protrusion606includes a peg606aand a collar606b. As shown inFIGS. 6A-6C, the collar606bis a disc shape with a height (e.g., about 1 mm), and may be of any suitable shape (e.g., rod, etc., to match the shape of the recess602) and may have any suitable height to restore radial length. The first prosthesis601(e.g., a radial head) may be configured to be angled and smooth to improve contact with e.g., a radial notch. The first prosthesis601may be highly polished to maintain articulation. The height of the first prosthesis601may range from about 10 mm to about 11.5 mm (if including the collar606bheight which is about 1 mm, the total height would range from about 11 mm to about 12.5 mm). The height of the collar606bmay vary to restore radial length. The diameter (of a top surface) of the first prosthesis601may be about 18 mm. The protrusion606may have a contoured lateral surface to improve interface with e.g., the annular ligament. The stem portion607may be fluted for rotational stability. The stem portion607may have grit-blasted surface to promote bony on-growth. The stem portion607may have a length of about 25 mm, which may be long enough to provide stability against bending movement but short enough not to reach e.g., the bend in the proximal canal. The stem portion607may have a tapered (e.g., triangle-shaped) end to aid insertion.

The first prosthesis601includes a side opening690, which connects to the recess602and is configured to allow the peg606ato slide into the recess602. The peg606amay have notches694on two opposite sides. The side opening690is shaped corresponding to the notches694of the peg606ato facilitate the sliding of the peg606ainto the recess602and to prevent vertical movement of the peg606arelative to the first prosthesis601. On a side opposite to the side opening690, the first prosthesis601includes a hole691. The hole691connects to the recess602and is configured to allow a screw692to pass into the recess602.

The screw692may be a locking screw or a set screw to connect/couple the first prosthesis601with the peg606a. It will be appreciated that using the screw fixation/mechanism alone may not be reliable; pitfalls include accidental cross threading of the screw(s) into the prosthesis and eventual loosening of the screw(s) over time. The screw(s) may also strip from over tightening. Moreover, the screw head(s) may shear off the shaft. With the screw fixation/mechanism alone, loosening or cross threading of the screw(s) may be a concern. For example, if the articulation is off or loosens, progressive loosening may occur with ultimate complete disarticulation. The magnet locking mechanism disclosed herein may be used in conjunction with screw(s) to prevent loosening or backing out of joint articulations.

The peg606aincludes a screw-hole693. The screw-hole693is disposed at a side that is perpendicular to the sides of the notches694. In an operation, the side having the screw-hole693is facing the opening690, and the first prosthesis601is sliding toward the peg606aof the second prosthesis605. The peg606apasses through the opening690and is then housed in the recess602. This process is defined as side-loading (of the first prosthesis601onto the second prosthesis605).

It will be appreciated that the first prosthesis601may include engagement grooves (not shown) on the sides (e.g., the symmetric two sides that is typically perpendicular to the side where the opening690(or the hole691) is located) of the first prosthesis601, to engage with an alignment tool (not shown, to align the marker of the first prosthesis601with the marker of the second prosthesis605) that is used to control the position of the first prosthesis601.

When the first prosthesis601is side-loaded onto the second prosthesis605, the hole691may be aligned with the screw-hole693, and the magnetic prosthesis604may lock the first prosthesis601and the second prosthesis605in place (a click may be audible when the magnet attaches to the ferromagnetic metal). Bone holding forceps may be used in the procedures such as resecting a portion of the joint, preparing a medullary canal of the joint, and/or inserting a second prosthesis of the joint prosthesis assembly into the medullary canal, etc. to hold the bone/joint. After removing the bone holding forceps, the alignment tool may be secured to the first prosthesis601by engaging with the grooves of the first prosthesis601, and to control the position of the first prosthesis601so that the hole691is disposed laterally to allow easy access to the surgeon. The alignment tool may also be used to align the marker of the first prosthesis601with the marker of the second prosthesis605. The screw692may be screwed into the screw-hole693via the hole691and/or the recess602to lock the first prosthesis601into the peg606aof the second prosthesis605.

In a specific example embodiment, the implantable joint prosthesis assembly includes an anatomic radial head made of a durable material (cobalt-chrome and/or other metal alloys) with a rare-earth magnet inserted inside the hollowed radial head shell. The magnet has a recess in the middle that may be square, rectangular, circular, etc. in shape. A prosthetic/radial stem with its collar and/or peg that is a ferromagnetic metal of the same matching shape (as the recess) may couple into the magnet. The radial head, the prosthetic stem, and the magnet may be connected by the polarity of the rare-earth magnet pulling (e.g., about 90 newton to about 200 newton strength in a 3 cm diameter magnet disc/rod) the ferromagnetic metal into the recess for the prosthetic stem. The prosthetic stem may be a grit-blast material with plasma coating or a polished smooth stem. The collar and/or peg on the prosthetic stem may be articular with the radial head. The prosthetic stem may be straight or curved in shape with varying lengths. The magnet may be linked to the radial head or the prosthetic stem either by direct magnetic bond or welded to any one of them.

In at least one example embodiment, in performing joint arthroplasty (e.g., implanting the implantable joint prosthesis assembly disclosed herein), an exposure (e.g., cutting and/or opening the skin and the joint capsule) of the joint (e.g., a radiocapitellar joint) of a patient is performed. A portion of the joint (e.g., the radial head, which needs to be replaced) is resected. A medullary canal (e.g., of the proximal radius) is prepared. The second prosthesis (e.g., a radial stem) of the implantable joint prosthesis assembly is inserted into the medullary canal. After appropriate trialing of the size of the first prosthesis (e.g., a radial head) of the implantable joint prosthesis assembly with respect to the height and diameter of the first prosthesis (that matches the resected head of the joint), the first prosthesis is inserted/implanted. The first prosthesis may be inserted from a lateral side of the joint (e.g., the elbow). The magnetic pull (because of the magnet prosthesis of the implantable joint prosthesis assembly interacts with the ferromagnetic metal of the first/second prosthesis) may then allow for the first prosthesis and the second prosthesis to lock into place. The recess in the first prosthesis may allow for reproducible and strong connection between the first prosthesis and the second prosthesis. A surgeon may feel a definite click or lock to ensure that the coupling is complete. As the magnet may pull on the ferromagnetic metal of the first/second prosthesis, the coupling may automatically articulate to its tightest fit. The joint capsule and the skin may then be closed. It will be appreciated that coating of the first prosthesis and/or the second prosthesis of the joint prosthesis assembly with a ferromagnetic metal may be needed to achieve/strength the magnetic pull.

Embodiments disclosed herein may provide (1) secure magnetic bond between components of an implantable joint prosthesis assembly, (2) longevity of the bond, and (3) ease and reproducibility of use. Embodiments disclosed herein may also be used in minimally invasive joint arthroplasty as the articulation does not require impaction. The rare-earth magnets disclosed herein may be combined with, coupled or inserted into any existing metal joint prosthesis without significant alterations to the implant design. Magnets may retain their properties for more than 100 years that may outlast the patient's lifespan. In a magnetic locking or coupling mechanism disclosed herein, if there is slight shifting of the prosthesis from impaction, the magnet and ferromagnetic metal may seek to re-bond and articulate back in place without intervention.

Different features, variations and multiple different embodiments have been shown and described with various details. What has been described in this application at times in terms of specific embodiments is done for illustrative purposes only and without the intent to limit or suggest that what has been conceived is only one particular embodiment or specific embodiments. It is to be understood that this disclosure is not limited to any single specific embodiments or enumerated variations. Many modifications, variations and other embodiments will come to mind of those skilled in the art, and which are intended to be and are in fact covered by both this disclosure. It is indeed intended that the scope of this disclosure should be determined by a proper legal interpretation and construction of the disclosure, including equivalents, as understood by those of skill in the art relying upon the complete disclosure present at the time of filing.