BACKGROUND OF THE INVENTION

In many instances following an initial surgery to repair a joint, a revision surgery is required, which generally involves implantation of new prostheses. Revision surgery may be required due to underlying maladies such as infection or dislocation, or simply because of the wear of the initially implanted prostheses.

When revision surgery involves reconstruction of the hip joint, and the reconstruction only requires the removal of an inner acetabular liner and not an outer shell secured to the acetabulum, such as circumstances where the implants are part of a modular dual mobility system, such a task is often very difficult and time consuming to perform intra-operatively. Indeed, it is a labor intensive and potentially damaging exercise. For example, in an intra-operative setting, conventional tools such as osteotomes or drills are often used to chip away exposed cement mantle between an outer acetabular shell and an inner liner to remove the liner. This process is time consuming and may result in damage to the acetabular shell and/or the bone underneath it. In other types of implant configurations where the acetabular shell is press-fit to the acetabulum without screws, an acetabular extraction device may be used to remove the acetabular shell, cement mantle and the inner liner. In the latter circumstance, the significant forces applied to the cement mantle between the acetabular elements as part of the process may still pose a high risk of damage to bone or even bone loss may occur during the extraction process. This is particularly so as the cement must be removed one small fragment at a time. Moreover, due to the hemispherical geometry of the cement mantle in between the acetabular shell and the inner liner, it is difficult to access the cement toward the polar regions of the acetabular elements with conventional tools.

Thus, a need exists for improved devices, systems and methods relating to hip implants that are also adapted for revision surgery.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the present disclosure relates to an assembly with an inner hemispherical construct, also referred to as an acetabular liner, and a sleeve mechanically fixed to a surface of the inner hemispherical construct. In use, the assembly is fitted into an outer acetabular construct such as an acetabular shell in a mammalian body and secured thereto with cement.

In some embodiments, the sleeve is a partial hollow hemisphere with an inner surfaces having protrusions thereon. The protrusions may include two separate sets, each at a different depth of the sleeve and spaced equally from one another within one set but out of phase with each other between sets. The sleeve is sized to fit over the liner in a flush manner and is further arranged to lock to the liner via the protrusions. In particular, the liner includes a plurality of perimeter grooves extending circumferentially around the liner and a plurality of polar grooves extending between equatorial and polar regions of the liner. The sleeve is locked to the liner through a snap fit between each protrusion and one of the perimeter grooves.

In some embodiments where the assembly is fitted into an outer hemispherical construct, the sleeve is made of a polymer while the inner hemispherical construct and the outer hemispherical construct are metallic. In this manner, the structure of the assembly is such that when the assembly is in place within an outer hemispherical construct, the polymer sleeve insulates cement between the metallic outer hemispherical construct and the metallic inner hemispherical construct so that the cement is only exposed to metal on one side in the equatorial region.

In one embodiment, the present disclosure relates to an acetabular implant system that includes an acetabular cup, a liner and a sleeve. The liner includes a convex outer surface shaped to correspond to the acetabular cup and has an equatorial region and a polar region. The convex outer surface of the liner includes a plurality of liner engagement features thereon. The sleeve includes an inner surface with a plurality of sleeve engagement features thereon and is sized to be flush with the convex outer surface of the liner. When the sleeve is engaged with the liner, the liner engagement features engage the sleeve engagement features.

In some embodiments, when the sleeve is engaged with the liner, the sleeve may cover a first portion of the polar region of the convex outer surface of the liner without covering a second portion of the polar region. In other embodiments, the plurality of liner engagement features may include a circumferentially extending recess parallel to a rim of the liner. In still further embodiments, the plurality of sleeve engagement features may be protrusions shaped to fit within the circumferentially extending recess on the convex outer surface of the liner. In still further embodiments, the plurality of liner engagement features may include a second circumferentially extending recess parallel to the rim of the liner. Additionally, the protrusions on the inner surface of the sleeve may include a first protrusion at a first distance from a rim of the sleeve and a second protrusion at a second distance from the rim of the sleeve. The protrusions may be positioned such that the first protrusion fits within the circumferentially extending recess and the second protrusion fits within the second circumferentially extending recess. In some embodiments, the sleeve may include an outer surface with a second plurality of sleeve engagement features thereon. In some embodiments, the plurality of liner engagement features may include a plurality of recesses extending from a pole of the liner to a rim of the liner. Similarly, the second plurality of sleeve engagement features may include a plurality of recesses aligned with the plurality of recesses on the convex outer surface of the liner when the sleeve is engaged with the liner. In other embodiments, the plurality of liner engagement features may be one of recesses and protrusions and the plurality of sleeve engagement features may be the other of recesses and protrusions. In some embodiments, the sleeve may be a polymeric material and the liner may be a metallic material.

In one embodiment of the disclosure, an acetabular implant includes an acetabular cup, a liner and a sleeve. The acetabular cup is adapted to seat within an acetabulum of a mammal, the liner is disposed in the acetabular cup, and the sleeve is engaged to a portion of an outer surface of the liner such that the sleeve is disposed in between the acetabular cup and the liner. With the sleeve engaged to the liner, the liner is cemented to the acetabular cup.

In some embodiments, the sleeve may be a segment of a hollow sphere between two parallel planes where one of the two parallel planes bisects the hollow sphere. In some embodiments, the liner may include an equatorial region and a polar region such that the sleeve separates the liner from the acetabular cup solely in the equatorial region. In some embodiments, the cement for engagement of the liner with the sleeve is disposed between the liner and the acetabular cup over an entirety of both the equatorial region and the polar region of the liner. In some embodiments, the sleeve may include an inner surface with protrusions thereon. The protrusions may be engaged to corresponding recesses on an outer surface of the liner. In some embodiments, the recesses on the outer surface of the liner may extend circumferentially and in parallel to a rim of the liner.

In another aspect, the present disclosure relates to an acetabular implant system with a liner and a sleeve. In one embodiment, the liner includes a convex outer surface shaped to correspond to an interior of an acetabular cup and has an equatorial region and a polar region. The convex outer surface of the liner includes a plurality of liner engagement features thereon. The sleeve includes an inner surface with a plurality of sleeve engagement features thereon and is sized to be flush with the convex outer surface of the liner. When the sleeve is engaged with the liner, the liner engagement features engage the sleeve engagement features.

In some embodiments, when the sleeve is engaged with the liner, the sleeve may cover a first portion of the polar region of the convex outer surface of the liner without covering a second portion of the polar region. In other embodiments, the plurality of liner engagement features may include a circumferentially extending recess parallel to a rim of the liner. In still further embodiments, the plurality of sleeve engagement features may be protrusions shaped to fit within the circumferentially extending recess on the convex outer surface of the liner. In still further embodiments, the plurality of liner engagement features may include a second circumferentially extending recess parallel to the rim of the liner. Additionally, the protrusions on the inner surface of the sleeve may include a first protrusion at a first distance from a rim of the sleeve and a second protrusion at a second distance from the rim of the sleeve. The protrusions may be positioned such that the first protrusion fits within the circumferentially extending recess and the second protrusion fits within the second circumferentially extending recess.

In some embodiments, the sleeve may include an outer surface with a second plurality of sleeve engagement features thereon. In some embodiments, the plurality of liner engagement features may include a plurality of recesses extending from a location proximal to a pole of the liner to a rim of the liner. Similarly, the second plurality of sleeve engagement features may include a plurality of recesses aligned with the plurality of recesses on the convex outer surface of the liner when the sleeve is engaged with the liner. In other embodiments, the plurality of liner engagement features may be one of recesses and protrusions and the plurality of sleeve engagement features may be the other of recesses and protrusions. In some embodiments, the sleeve may be a polymeric material and the liner may be a metallic material. In some embodiments, the system may include the acetabular cup.

In another aspect, the present disclosure relates to a method of removal of an assembly from within an existing outer acetabular construct of a hip implant. In some embodiments, a conventional tool is used to remove the sleeve of the assembly from the inner acetabular construct of the assembly so that a void is created between the outer construct and the inner construct in the equatorial region. In particular, the tool may be used to cut or chisel the sleeve and adjacent cement, and also to pull the protrusions of the sleeve from the grooves in the inner acetabular construct. Through the void created, the tool may be inserted deep toward a polar region of the inner acetabular construct to pry it out from the remaining cement engagement between the inner acetabular construct and the outer acetabular construct in the polar region.

In one embodiment, the present disclosure relates to a method of removing a liner from an acetabular cup secured to an acetabulum. The method of removal includes the following steps: ensuring that the acetabular cup with the liner cemented therein is accessible to an extent sufficient to remove the liner; causing a sleeve engaged to an outer surface of the liner to become disengaged from the liner; removing the sleeve such that the liner remains at least partially cemented to the acetabular cup in a polar region of the liner; and after removing the sleeve, removing the liner from the acetabular cup such that the acetabular cup remains secured to the acetabulum.

In some embodiments, removing the sleeve may include removing a portion of the cement immediately in between the sleeve and the acetabular cup. In some embodiments, removing the sleeve may leave no more than 60% of an outer surface of the liner covered by cement that secures the liner to the acetabular cup. In some embodiments, causing the sleeve to become disengaged from the liner may include prying a tab on an inside surface of the sleeve from a groove on an outside surface of the liner. In some embodiments, removing the liner may involve rotating the liner relative to the acetabular cup.

