The hip joint may undergo various degenerative changes due to a variety of etiologies, such as arthritis, or may be injured through a traumatic event. Any one of these conditions of the hip joint may necessitate an orthopedic procedure to correct the underlying cause of the patient's morbidities. Orthopedic procedures for the hip joint are various and typically include replacing the natural joint with an artificial joint. This generally involves the replacement of a natural acetabulum with an acetabular shell and corresponding articular liner, and the replacement of an articular surface of a natural femoral head with an artificial articular surface.
The replacement of the femoral head articular surface may involve the complete removal of the natural femoral head and its substitution with an artificial ball that sits atop a stem that is inserted into an intramedullary canal of the femur, as in the case of total hip arthroplasty (“THA”). However, in a hip resurfacing procedure, underlying bone of the natural femoral head is preserved so that only its exterior is resurfaced with a prosthesis. In either type of procedure, i.e., THA or resurfacing, the femoral head, whether entirely or partially artificial, is ordinarily received within and articulates with the liner. However, some THA prostheses have a dual mobility function in that articulation can also take place between the articular liner and acetabular shell which can help reduce component wear.
Hip resurfacing has been a popular alternative to THA due to many perceived advantages, such as increased range of motion, decreased dislocation, improved biomechanics, decreased wear, improved function, as well as less complicated revisions in connection with periprosthetic fractures. However, because of the minimal space between the bones afforded by a resurfacing procedure, hip resurfacing implants have typically utilized metal on metal articulation as polyethylene inserts adapted for resurfacing have been considered too thin to have sufficient durability over a patient's lifetime. For similar reasons, dual mobility has also never been implemented in a resurfacing prosthesis. Due to adverse local tissue reaction associated with resurfacing systems utilizing metal on metal articulating surfaces, many hip surfacing replacements were removed from the marketplace. Therefore, further improvements are desirable.
In various embodiments, a system is disclosed herein that includes an acetabular component having a concave, articulating surface and a femoral head component having a convex articulating surface. Moreover, embodiments of the system disclosed herein include a dual mobility liner compatible with the articulating surface of the acetabular component and the femoral component, the liner may be composed of a cross-linked ultra-high-molecular-weight polyethylene material. The dual mobility liner may have a plurality of openings extending therethrough from the inner surface of the liner to the outer surface of the liner, which may thereby reduce contact area, increase fluid transport, and consequently reduce wear between the components. The dual mobility liner allows for movement between the inner articulating surface of the acetabular component and the outer surface of the liner as well as between the outer articulating surface of the femoral head and the inner surface of the liner. This movement allows the femoral head component the ability to swivel, rotate and tilt within the acetabular component, which itself can also swivel, rotate and tilt within the acetabular insert.
Further embodiments of the system disclosed herein include a dual mobility liner with an edge extending between the inner and outer surface of said liner. Moreover, the head of the femoral component may include an extension extending from the head from between the inner surface and convex outer articulating surface of the head, the extension engaging the edge of the dual mobility liner in deep angles of articulation to prevent impingement on a femoral neck by the liner. The head of the femoral component may include one or more grooves extending into and along the outer surface, reducing the contact area and wear.
Further embodiments of the system disclosed herein include a liner that contacts the femoral head below the center of rotation to limit the ability of the femoral head to disengage with the liner and shell.
In one aspect, the present disclosure relates to a dual mobility hip resurfacing implant with an acetabular component having a first cavity and may include a liner having an outer surface configured to be received within the cavity and articulable therein relative to the inner surface of the acetabular component. The embodiment may further include a femoral component having a head and a stem, the head having a convex outer surface and a concave inner surface, the stem extending from the inner surface of the head and being configured to be received within an opening of a femoral head of a femur. Further, the outer surface of the femoral component may be configured to be received within a cavity of the liner and articulable therein relative to the inner surface of the liner. In further embodiments of the system disclosed herein, the liner may include an edge extending between the inner and outer surfaces, and the head of the femoral component may include an extension extending from the head from between the inner and outer surface of the head, the extension engaging the edge of the liner at least one angle of articulation between the head and the liner. In a further variation, the edge of the liner may be obliquely angled relative to the inner and outer surfaces of the liner, and the extension may include a planar surface configured to engage the edge. In one aspect of the system, the liner may be made from a cross-linked ultra-high-molecular-weight polyethylene material. In further aspects, the liner may be composed of, but not limited to, polyetheretherketone (PEEK), or polyurethane. The liner may further include a plurality of openings extending therethrough from the inner surface to the outer surface. The head of the femoral component may further include a groove extending into and along the outer surface thereof. Further, one or more of the grooves may extend in a medial to lateral direction when implanted in a mammalian subject. Further, one of more of the grooves may contain angled ridges extending transverse to a longitudinal direction of the groove. In further embodiments, the surface of the acetabular component may contain multiple radii of curvature. In particular, one embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is greater than a difference between the third and the fourth radii of curvature. Further, another embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is less than a difference between the third and the fourth radii of curvature. Further, another embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is equal to a difference between the third and the fourth radii of curvature.
In one aspect, the present disclosure relates to dual mobility hip implant with an acetabular component having a cavity and may include a liner having an outer surface configured to be received within the cavity of the acetabular component. The liner may further be configured to form a cavity to receive a femoral head. Further, the liner may include a plurality of openings extending through the liner. The embodiment may include a femoral component having a head with an outer surface configured to be received within the cavity of the inner surface of the liner. In further embodiments of the system disclosed herein, the liner may include an edge extending between the inner and outer surfaces, and the head of the femoral component may include an extension extending from the head from between the inner and outer surface of the head, the extension engaging the edge of the liner at least one angle of articulation between the head and the liner. In a further variation, the edge of the liner may be obliquely angled relative to the inner and outer surfaces of the liner, and the extension may include a planar surface configured to engage the edge. In one aspect of the system, the liner may be made from a cross-linked ultra-high-molecular-weight polyethylene material. In further aspects, the liner may be composed of, but not limited to, polyetheretherketone (PEEK), or polyurethane. The head of the femoral component may include a groove extending into and along the outer surface thereof. One or more of the grooves may extend in a medial to lateral direction when implanted in a mammalian subject. Further, one of more of the grooves may contain angled ridges extending transverse to a longitudinal direction of the groove. In further embodiments, the surface of the acetabular component may contain multiple radii of curvature. In particular, one embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is greater than a difference between the third and the fourth radii of curvature. Further, another embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is less than a difference between the third and the fourth radii of curvature. Further, another embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is equal to a difference between the third and the fourth radii of curvature.
In one aspect, the present disclosure relates to dual mobility hip implant with an acetabular component having a cavity and may include a liner having an outer surface configured to be received within the cavity of the acetabular component. The liner may further be configured to include a cavity to receive a femoral head. The embodiment may include a femoral component having a head having an outer surface configured to be received within the cavity of the inner surface of the liner. In further embodiments of the system disclosed herein, the head of the femoral component may include a groove extending into and along the outer surface thereof. In further embodiments, the surface of the acetabular component may contain multiple radii of curvature. In particular, one embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is less than a difference between the third and the fourth radii of curvature.
In one aspect, the present disclosure related to a dual mobility hip resurfacing implant with an acetabular component having a first cavity and a liner configured to be received within the first cavity and articulable therein, the liner additionally having a cavity configured to receive a femoral head component. Further, the femoral component may be configured to be received on a femoral head of a femur bone. In further variations, inner surface of the liner may include a first circumferential ledge complementary to a second circumferential ledge on the third outer surface of the femoral head component. In a further embodiment, the first and second circumferential ledges may be positioned between a plane through a center of rotation of the implant that is parallel to an end surface of the liner and a second plane parallel to the first plane and through an apex of the liner.
In further variations, the femoral component may include a first convex surface portion, a second convex surface portion, and a third convex surface portion. In certain embodiments, at least one of the first convex surface portion and the second convex surface portion may include interruptions such that when the first convex surface portion is interrupted, the first convex surface portion includes a first plurality of interruptions at a first plurality of locations on the second outer surface, and when the second convex surface portion is interrupted, the second convex surface portion includes a second plurality of interruptions at a second plurality of locations on the third outer surface. In further variations, the first plurality of interruptions of the first convex surface portion may be a plurality of openings extending through the liner from the second inner surface to the second outer surface thereof. Further, the second plurality of interruptions of the second convex surface portion may be a plurality of grooves on the third outer surface. In further embodiments, the plurality of grooves may include a plurality of angled ridges distributed along at least a portion of a length of the groove, each of the plurality of angled ridges extending transverse to a longitudinal direction of the groove. In further variations, the first convex surface portion may include the first plurality of interruptions and the second convex surface portion may include the second plurality of interruptions. Further embodiments may include a stem extending from the third inner surface, the stem being configured to be received within an opening of the femoral head. In further variations, the second outer surface and the second inner surface may be separated by a liner end surface and the femoral head component may include an extension extending to an open end of the femoral head component such that the extension is remote from an apex of the femoral head component relative to other parts of the femoral head component. Further, the extension may include a blocking surface configured to prevent over rotation of the liner end surface by limiting an extent of rotation of the liner end surface.
In one aspect, the present disclosure related to a dual mobility hip implant system may include an acetabular shell having a first cavity and a liner having a second cavity, and a plurality of openings extending through the liner from a second outer surface to a second inner surface, the second outer surface being configured to be received within the first cavity of the shell and being articulable relative to the inner surface of the acetabular component when disposed therein. Further, the liner may be configured to be received on a femoral head implant. In further embodiments, each of the plurality of openings of the liner may be circular in shape. In further embodiments, each of the plurality of openings of the liner may be positioned equidistant from each other along the surface of the liner. Further, variations may include a plurality of openings that may be arranged in parallel concentric rings along the surface of the liner. In further embodiments, the surface of the acetabular component may contain multiple radii of curvature. In particular, one embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is greater than a difference between the third and the fourth radii of curvature. Further, another embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is less than a difference between the third and the fourth radii of curvature. Further, another embodiment may contain four radii of curvatures, where the difference between the first and second radii of curvature is equal to a difference between the third and the fourth radii of curvature.
In one aspect, the present disclosure related to a dual mobility implant system may include a liner with an outer surface configured to be received within an acetabular shell and an inner surface defining a first cavity configured to engage with a femoral implant. Further, the inner surface of the liner may include a first circumferential ledge. In further embodiments, the system may include a femoral implant including a head configured to be received within the first cavity, the head having a second circumferential ledge in operative communication with the first circumferential ledge. The structure of the liner and the femoral implant may be such that an extent of rotation of the femoral implant relative to the liner when the femoral implant is disposed in the liner is limited by the first circumferential ledge. In further embodiments, the first circumferential ledge may be positioned between a first plane through a center of rotation of the liner and parallel to an end surface of the liner and a second plane parallel to the first plane and through an apex of the liner. Variations may include varying angles, where an axis though the center of rotation and the first circumferential ledge may be within a range of about 5 to 20 degrees relative to the first plane. Further, the thickness of the first circumferential ledge may vary in thickness, in that the thickness may range from about 10% to about 50% of a maximum thickness of the liner.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
As also shown in
Femoral head component 120 is configured to resurface a native femoral head. In this regard, femoral head component 120 includes a concave inner surface 124 that defines a cavity 126 configured to receive native bone of a patient's femoral head and/or femoral neck. Inner surface 124 is comprised of a plurality of intersecting flat surfaces configured to mate with corresponding resected planar surfaces of the underlying native bone. However, in other embodiments, inner surface 124 may be curved, such as spherically curved, for example. Additionally, a stem 128 extends from inner surface 124 and is configured to be received within an opening in the native femoral head and/or femoral neck. Thus, femoral head component can resurface a native femoral head without the need to completely remove the femoral head and/or neck of the patient.
As mentioned above, acetabular liner 110 is received within acetabular cup 100 and is free to articulate with acetabular cup in at least one degree of freedom. Also, femoral head component 120 is received within acetabular liner 110 and is free to articulate with acetabular liner 110 in at least one degree of freedom but preferably more than one degree of freedom so that femoral head component 120 is able to swivel, rotate and tilt within liner 110. As such, the system that includes acetabular component 100, acetabular liner 110, and femoral component 120 is a dual mobility and femoral head resurfacing prosthesis system.
In the embodiment depicted, femoral head 220 includes four grooves 225. However, in other embodiments more or less grooves may be provided. Each groove 225 may be configured to include angled ridges 227 to induce fluid flow along said groove 225. Angled ridges 227 may extend across each ridge in a helical pattern so that each ridge is angled relative to a longitudinal axis of groove 225. In other words, each ridge has a component extending in a transverse direction and a component extending in a longitudinal direction of groove 225. The interaction between acetabular liner 110 and angled ridges 227 during hip motion may influence fluid flow between each ridge 227. In other words, the movement of the acetabular liner 110 across the groove 225 may induce fluid to move from a high-pressure area H to a low-pressure area L, as best shown in
Although femoral head 220 with grooves 225 is depicted and described as a femoral head resurfacing component, such grooves may be implemented in a THA femoral prosthesis to help minimize wear between components.
Femoral stem component 340 includes a trunnion 342 and a stem body 344. Trunnion 340 is configured to be received within opening 329 of femoral head component and therefore may be tapered for a taper-lock connection. Stem body 344 is configured to be received within an intramedullary canal of a femur so that when stem body 344 is received within such femur, stem body 344 is positioned within at least the metaphysis or the metaphysis and diaphysis of the bone. Stem body 344 may be configured for cemented implantation or press-fit implantation. Where stem body 344 is configured for press-fit implantation, stem body 344 may include a porous outer surface for bony ingrowth.
A dual mobility acetabular liner, like acetabular liner 110, has the ability to move in an unconstrained manner between an acetabular shell, such as shell 100, and a femoral head component, such as component 120. Movement between these components can be controlled by implementing differential radii in order to facilitate wear reduction. As shown in
In any of the embodiments of the system described herein, clearances between the articulating surfaces 404, 422 of the acetabular cup 400 and femoral component 420 and the articulating inner and outer surfaces 412, 414 of the dual mobility liner 410 may be adjusted such that there is a lower, higher, or equal coefficient of friction between outer surface 412 of liner 410 and inner surface 404 of acetabular shell 400 relative to inner surface 414 of liner 410 and outer surface 422 femoral head 420. This may be done by adjusting the differences between the radii of such articular surfaces.
Where it is desirable for the articular interface between acetabular cup 400 and acetabular liner 410 to have less friction than the articular interface between acetabular liner 410 and femoral head 420, the difference between R2 and R1 is greater than the difference between R3 and R4. In other words, where articular motion is primarily between cup 400 and liner 410, then R1-R2>R3-R4. Such differential creates a larger gap 430 at the edges of cup 400 and liner 410 than at the edges of liner 410 and head 423. In this regard, there is less overall contact between cup 400 and liner 410 than between liner 410 and head 423 and therefore less friction. In one specific example, R1 is 27.0 mm, R2 is 26.6 mm, R3 is 25.0 mm, R4 is 24.9 mm. Thus, the difference between R2 and R1 is results in a radial clearance of 0.4 mm between the acetabular shell 400 and dual mobility liner 510. In comparison, the difference between R3 and R4 results in a smaller clearance, specifically, a radial clearance of 0.1 mm, between dual mobility liner 510 and femoral head 420. This will result in a preferential motion at the interface between acetabular shell 400 and dual mobility liner 410 due to the smaller contact area and lower coefficient of friction relative to the interface between the dual mobility liner 410 and the femoral head 420. This configuration may be implemented in embodiments involving acetabular liner 110 with openings 111.
Where it is desirable for the articular interface between acetabular liner 410 and femoral head component 420 to have less friction and therefore exhibit primary articular motion, then R1-R2<R3-R4. In one specific example, R1 is 27 mm, R2 is 26.9 mm, R3 is 25.3 mm, and R4 is 24.9 mm. In such example, the difference between R1 and R2 is 0.1 mm, and the difference between R3 and R4 is 0.4 mm. This configuration may be implemented in embodiments involving femoral components 220 or 320 with a continuous acetabular liner (i.e., does not have openings 111). In this regard, primary articulation would be between the femoral head and acetabular liner to help take additional advantage of the wear reduction characteristics of grooves 225 and 325.
In instances where preferential motion at any one interface is not desirable, then R1-R2=R3-R4. In other words, the radial clearance between acetabular cup 400 and acetabular liner 410 is the substantially the same as that between acetabular liner 410 and femoral head component 420. This configuration may be implemented in embodiments involving acetabular liner 110 with openings 111 and either femoral component 220 or 320.
Thus, in general, inner surface 404 of the acetabular cup 400 may have a first radius of curvature R1, outer surface 412 of liner 410 may have a second radius of curvature R2, inner surface 414 of liner 410 may have a third radius of curvature R3, and outer surface 422 of head 420 may have a fourth radius of curvature R4. In one embodiment, the difference between the first and second radii of curvature R1, R2 may be greater than a difference between the third and the fourth radii of curvature R3, R4. In another embodiment, the difference between the first and second radii of curvature R1, R2 may be less than a difference between the third and the fourth radii of curvature R3, R4. In another embodiment, the difference between the first and second radii of curvature R1, R2 may be equal to a difference between the third and the fourth radii of curvature R3, R4.
In additional embodiments, the radius of curvature, such as R4, and articular coverage of the femoral head component 420 may be reduced relative to that of the native femoral head of the patient. This may be accomplished without limiting the total range of motion of the joint prosthesis system. In particular, although the decreased articular coverage may reduce the range of motion between the resurfacing femoral component 420 and the dual mobility liner 410, the total range of motion of the entire assembly 450 is maximized by the articulation of the outer surface 412 of the dual mobility liner 410 relative to the acetabular component 400. Thus, the patient will not experience a significant reduction in overall range of motion while obtaining certain benefits by the decreased articular coverage by femoral head 420. For example, such decreased articular coverage of the femoral head 420 allows the use of a steeper angle of resection, such as greater than 5 degrees, and a larger diameter taper cut on the native femoral head in preparation to receive femoral head 420 than if femoral head 420 were required to have the same range of motion as the natural femoral head. As a result, the likelihood of notching the native femoral neck and the risk of associated periprosthetic facture is reduced.
As shown in
In another embodiment, an implant system 500, such as that shown in
Femoral head 506 may include a porous inner lining 509 for interfacing with the femur. Further, an outer surface of the femoral head includes a first circumferential ledge 510 extending around the outer surface of the femoral head. The first circumferential ledge 510 is oriented such that it faces away from an opening of the femoral head, as shown in
In some examples, second circumferential ledge 516 may be located on the liner such that an axis through the second circumferential ledge 516 and a center of rotation 504 of the liner is at an angle of 1 to 20 degrees relative to a plane parallel to an end surface 518 of the liner and through the center of rotation 504. The end surface 518 of the liner separates the outer and inner surfaces of the liner. In the depicted example of the system, the angle between the referenced axis and the plane is within the range of the above referenced examples. In other specific examples, the angle may be 5 degrees, 10 degrees, 15 degrees or 20 degrees. In still further examples, the angle may be 1 degree, 2 degrees, 3 degrees or 4 degrees. While the above provides some illustrative examples of the arrangement of the liner circumferential ledge, such examples are not limiting and it is contemplated that arrangements other than those explicitly provided for are contemplated. Further, the thickness of the second circumferential ledge 516 may vary. In some examples, a width of the second circumferential ledge 516 may be from about 10% to about 50% of a thickness of the liner, where the thickness may be a maximum thickness of the liner. In certain other examples, the second circumferential ledge 516 may have a width as a percentage of the liner thickness that is less or more than the ratio of the above examples. A range of possible widths of the second circumferential ledge 516 may be determined based on a magnitude of the maximum liner thickness and/or materials used to form the liner, among other considerations. A width direction of the second circumferential ledge may be generally the same as a thickness direction of the liner adjacent to the second circumferential ledge.
In operation, femoral head 506 is rotatable about liner 514 with a limit on relative rotation between the components dictated by the location of the second circumferential ledge 516 relative to a center of rotation 504 of femoral head. In some examples, the femoral head may rotate up to 20 degrees relative to a central liner axis 507 such that an axis through the center of rotation and an apex 503 of the liner may rotate up to 20 degrees relative to the central liner axis 507 in any radial direction from central liner axis 507. In this way, a system of these examples may be configured so that a location of circumferential ledge 516 is rotatable within a 40 degree range in any plane: 20 degrees in a first direction from a neutral orientation and 20 degrees in a second direction opposite from the first direction. In another specific example, the femoral head may rotate up to 10 degrees off the central liner axis. An extent of possible rotation may be controlled through modification of a location of the second circumferential ledge 516 relative to the end face on the liner and a location of the first circumferential ledge on a surface of the femoral head, with possible arrangements including, among others, those described above. One advantage of the incorporation of this feature into a hip implant system is that it reduces the likelihood of impingement during normal wear of the implant including movements within an expected range of motion. Additionally, the location of the second circumferential ledge 516 on the liner is such that it is closer to apex 503 of the liner than center of rotation 504 of the femoral head. In this manner, a risk of pullout of the femoral head from the liner is reduced.
Various biocompatible polymers, metals, and ceramics may be utilized in the foregoing systems and devices. For example, acetabular liners 110 and 410 may be composed of, but not limited to, ultra-high molecular-weight polyethylene (UHMWPE), polyetheretherketone (PEEK), or polyurethane.. Use of a polymer, such as cross-linked UHMWPE, may decrease the potential for device fracture due to minimization of stresses from the lack of a locking mechanism on the dual mobility liner. Wear rate of the liner is additionally minimized by utilization of cross-linking of the material as well as the various wear reduction features described herein such as openings 111, grooves 225 and 325, and differential radii. The other components may be made from metal and/or ceramics so as to avoid metal-on-metal articulation. In this regard, acetabular cups 100 and 400 and femoral components 120, 220, and 420, and femoral stem component 240 may be made from a variety of materials, including but not limited to stainless steel, titanium, niobium, cobalt-chromium, and alloys thereof. In addition, coatings of various materials, for example, titanium nitride, titanium niobium nitride, silicon nitride, titanium carbo-nitride, zirconium oxide, hydroxyapatite, and aluminum oxide, may be applied to various surfaces.
The features described herein can be implemented alone or in combination. For example, a dual mobility resurfacing prosthesis may include acetabular liner 110 with openings 111, femoral head component 220 with grooves 225, and/or the differential radii of prosthesis 450. Similarly, a dual mobility THA prosthesis may include acetabular liner 112 with openings 111, femoral head component 320 with grooves 325 and femoral stem component 340, and/or the differential radii of prosthesis 450. Additionally, fixed bearing femoral head resurfacing or THA prostheses that do not have a dual mobility function may implement femoral head components 220 and 320, respectively, to help reduce component wear.
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.
The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 63/392,693, filed Jul. 27, 2022, the disclosure of which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | |
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63392693 | Jul 2022 | US |