Patent Description:
This document pertains generally, but not by way of limitation, to fitting a liner to an acetabular shell for hip replacement or revision surgery.

In a hip replacement or revision surgery, the acetabulum of the hip is reamed to provide a socket shaped mounting surface corresponding to the size and curvature of the femoral head of the natural or revised femur or femoral implant. After the prepared mounting surface is appropriately sized and shaped, an acetabular shell can be mounted to the mounting surface to provide a bearing surface for the femoral head. The acetabular shell can comprise a hemispherical shape to define a socket for receiving the femoral head. A liner can be inserted into the acetabular shell to fit the liner to an inner surface of the acetabular shell to cover mounting features or textures to provide a smooth bearing surface against which the femoral head can smoothly articulate.

The liner can often comprise a rigid or a resilient flexible material for withstanding the articulation of the femoral head, which requires the liner to be driven into the acetabular shell. If the liner is not properly aligned or centered with the acetabular shell prior to insertion, the liner can be improperly seated within the acetabular shell after insertion. A properly fitted liner is flush or nearly flush with the lip of the acetabular shell to avoid providing an edge or other protrusion that extends from the acetabular shell. The rigid or resilient flexible material of the liner requires the liner to be pried from the acetabular shell if improperly seated. The locking mechanism of the liner and the acetabular shell can make the liner difficult to pry from the acetabular shell. In addition, as the opening in the tissue to access the hip bone is usually minimally sized to reduce healing time, accessing the implanted acetabular shell and liner can be difficult causing discomfort or pain to the patient.

The inner surface of the acetabular shell can often have a curvature that corresponds to the outer surface of the acetabular shell. Acetabular shells commonly have a tapered region extending from the lip of the acetabular shell to the inner surface providing a thinner lip portion and corresponding to different bearing materials. While the tapered region provides an advantageous structure for the acetabular shell, the tapered region can make centering or aligning the liner more difficult and provide an angled surface that can cause the liner to shift or pivot as the liner is inserted into the acetabular shell.

<CIT> discloses an acetabular cup kit for use during hip replacement surgery which includes a polar component with a socket for receiving a femoral head of a femoral prosthesis. The disclosure of <CIT> differs from the present invention in that the fitting ring is implantable and does not include an engagement portion comprising an annular snap fit feature positioned on the interior surface of the fitting ring.

The present invention provides an acetabular implant system as defined in claim <NUM>.

Methods are described herein but the methods are not claimed.

The present inventors have recognized, among other things, that a problem to be solved can include the insertion of a liner into an acetabular shell at the proper alignment to avoid increasing the length of the surgical procedure or discomfort to the patient. In an example, the present subject matter can provide a solution to this problem, such as by attaching a fitting ring to an edge of a liner such that an alignment portion of the fitting ring extends radially outward from the liner. The alignment portion is shaped or configured to engage a lip portion of an acetabular shell as the liner is inserted into the acetabular shell. The engagement of the fitting ring to the lip portion of the acetabular shell centers the liner and corrects any pivoting of the liner relative to the acetabular shell. A driving force can be applied to the liner to drive the liner into the acetabular shell where the fitting ring guides the liner as the liner is inserted into the acetabular shell. Driving the liner into the acetabular shell can also cause the fitting ring to disengage from the liner.

For reference, a method for installing an acetabular implant can include reaming the acetabulum to prepare a curved mounting surface and fixing an outer surface of an acetabular shell to the mounting surface. The method can further include providing a liner and attaching a fitting ring to an edge portion of the liner such that an alignment feature of the fitting ring extends radially outward from the liner. The method can further include inserting the liner into an opening of the acetabular shell such that the liner is positioned adjacent to an inner surface of the acetabular shell. The insertion of the liner engages the alignment feature of the fitting ring to a lip portion of the acetabular shell defining the opening, where the fitting ring centers and corrects pivoting of the liner relative to the acetabular shell. The method can further include driving the liner into the acetabular shell such that the liner engages the inner surface of the acetabular shell and disengage the fitting ring from the liner.

It is not intended to provide an exclusive or exhaustive explanation of the present subject matter.

As depicted in <FIG> and <FIG>, an acetabular implant system <NUM>, according to an example of the present disclosure, includes an acetabular shell <NUM>, a liner <NUM>, and a fitting ring <NUM>. The acetabular shell <NUM> can be mounted to a prepared mounting surface on an acetabulum of the hip joint. The liner <NUM> can be fitted to the acetabular shell <NUM> to provide a bearing surface for a femoral head of a natural or resected femur or a femoral implant. The fitting ring <NUM> can be engaged to the liner <NUM> such that inserting the liner <NUM> into the acetabular shell <NUM> engages the fitting ring <NUM> to the acetabular shell <NUM> to center the liner <NUM> and correct any pivoting of the liner <NUM> with respect to the acetabular shell <NUM>.

The acetabular shell <NUM> comprises an outer surface <NUM> and an inner surface <NUM>. The outer surface <NUM> can be textured, shaped, perforated or include mounting features for receiving fasteners, cement, and/or bone in-growth material to fix the acetabular shell <NUM> to the acetabulum of the hip. The acetabular shell <NUM> can comprise a generally hemispherical shape such that the inner surface <NUM> is curved to an apex <NUM> to define a socket space for receiving a femoral head of a femur or a femoral implant. The acetabular shell <NUM> includes a lip portion <NUM> (see <FIG>) defining a generally circular opening for accessing the socket space defined by the inner surface <NUM>. In an example, the acetabular shell <NUM> can include a tapered portion <NUM> extending from the lip portion <NUM> to the inner surface <NUM> and can have a different curvature from the inner surface <NUM>. The inner surface <NUM> can have a curvature corresponding to the curvature of the outer surface <NUM>. The tapered portion <NUM> can have a different curvature from the inner surface <NUM>. In an example, the acetabular shells can have a diameter from about <NUM> to about <NUM>.

The liner <NUM> comprises a bearing surface <NUM> and an edge portion <NUM> extending around the bearing surface <NUM>. The liner <NUM> can comprise a generally hemispherical shape such that the bearing surface <NUM> is curved to define a socket space for receiving the femoral head. The liner <NUM> can be shaped to correspond to the curvature of the inner surface <NUM> of the acetabular shell <NUM>. The liner <NUM> can comprise a rigid material, a resilient flexible material, or combinations thereof. In an example, the liner <NUM> can comprise a polymer, a ceramic, a metal, a composite, or combinations thereof.

As depicted in <FIG>, the fitting ring <NUM> includes an engagement portion <NUM> and an alignment portion <NUM>. The engagement portion <NUM> is positioned on an interior surface <NUM> of the fitting ring <NUM>. According to the invention, the engagement portion <NUM> includes a snap fit feature engageable to an edge portion <NUM> of the liner <NUM>. The fitting ring <NUM> can comprise a resilient flexible material including, but not limited to a flexible polymer, a rubber or combinations thereof. In this configuration, the fitting ring <NUM> can flex to engage the engagement portion <NUM> to the edge portion <NUM> of the liner <NUM>. Similarly, the fitting ring <NUM> can be flexed to disengage the engagement portion <NUM> from the edge portion <NUM> of the liner <NUM>. The alignment portion <NUM> can be positioned on an exterior surface <NUM> of the fitting ring <NUM>. The alignment portion <NUM> can be sized such that the alignment portion <NUM> corresponds to the lip portion <NUM> of the acetabular shell <NUM>. The fitting ring <NUM> can have an inner diameter of from about <NUM> to about <NUM> to correspond to the outer diameter of the acetabular shell <NUM>.

In operation, the engagement portion <NUM> of the fitting ring <NUM> can be attached to the edge portion <NUM>. The fitting ring <NUM> can be flexed to engage the engagement portion <NUM> to the liner <NUM>. As depicted in <FIG> and <FIG>, the engagement portion <NUM> can extend circumferentially around the interior surface <NUM> of the fitting ring <NUM> to evenly engage the entirety of the edge portion <NUM> of the liner <NUM>. As depicted, the engagement portion <NUM> is positioned on the fitting ring <NUM>, but it is contemplated, although not within the scope of the present invention, that the engagement portion <NUM> can be positioned on the edge portion <NUM> of the liner <NUM> to engage the interior surface <NUM>.

As depicted in <FIG>, the liner <NUM> can be inserted through the opening defining the lip portion <NUM>. The alignment portion <NUM> engages the lip portion <NUM> as the liner <NUM> is inserted to maintain the liner <NUM> at a predetermined distance from the inner surface <NUM> of the acetabular shell <NUM>. The liner <NUM> and the alignment portion <NUM> cooperate to center the liner <NUM> within the opening of the acetabular shell <NUM>. The alignment portion <NUM> engages the circumference of the lip portion <NUM> to correct any pivoting of the liner <NUM> relative acetabular shell <NUM>.

As depicted in <FIG>, a driving force can be applied to the liner <NUM> along an axis A-A traversing the apex <NUM> of the acetabular shell <NUM>. The fitting ring <NUM> can be sized and structured to guide the liner <NUM> as the liner <NUM> is inserted to avoid pivoting of the liner <NUM>. In an example, the fitting ring <NUM> flexes as the liner <NUM> is inserted to disengage the fitting ring <NUM> from the liner <NUM>.

As depicted in <FIG> and <FIG>, a method <NUM> can comprise site preparation <NUM>, acetabular shell mounting <NUM>, fitting ring attachment <NUM>, liner alignment <NUM>, and liner mounting <NUM>.

In the site preparation step <NUM>, if necessary, a reamer is applied to the acetabulum of a hip at the mounting site to ream the bone. Increasingly sized reamers can be used to enlarge the mounting site and form an acetabular cavity. In an example, the bone can be reamed until bleeding subchondral bone is exposed. The acetabular orientation of the mounting site can be about <NUM> degrees inclination and about <NUM> degrees of anteversion, but depends on patient anatomy and the femoral implant and can be varied slightly.

In the acetabular shell mounting step <NUM>, the outer surface <NUM> of the acetabular shell <NUM> can be fitted to the mounting surface of the acetabulum. As depicted in <FIG>, a face impactor plate <NUM> of an impactor <NUM> can be fitted to the mounting surface of the acetabulum. The face impactor <NUM> can be shaped to correspond to the inner surface <NUM> of the acetabular shell <NUM>. The impactor <NUM> can be impacted with a hammer to drive the acetabular shell <NUM> into the mounting surface of the acetabulum. In an example, a cement, a fastener, or another mounting feature can be used to fix the acetabular shell <NUM> to the mounting surface of the acetabulum.

In the fitting ring attachment step <NUM>, the fitting ring <NUM> can be flexed to engage the engagement portion <NUM> to the liner <NUM> such that the alignment portion <NUM> of the liner <NUM> extends radially outward from the liner <NUM>.

As depicted in <FIG>, in the liner alignment step <NUM>, an inserter <NUM> can be fitted to the liner <NUM> and manipulated to insert the liner <NUM> through the opening of the acetabular shell <NUM>. The insertion of the liner <NUM> can engage the alignment portion <NUM> to the lip portion <NUM> of the acetabular shell <NUM>, which can center the liner <NUM> within the opening of the acetabular shell <NUM>. The engagement of the alignment portion <NUM> can also correct the pivoting of the liner <NUM> of the acetabular shell <NUM>.

As depicted in <FIG>, in the liner mounting step <NUM>, the inserter <NUM> can be manipulated to apply a driving force along an axis A-A transverse to the apex <NUM> of the acetabular shell <NUM> to push the liner <NUM> into the acetabular shell <NUM>. The liner <NUM> can guide the acetabular shell <NUM> as the liner <NUM> is driven into acetabular shell <NUM>. The driving force flexes the fitting ring <NUM> against the acetabular shell <NUM> to disengage the engagement portion <NUM> from the liner <NUM>.

For reference, described herein is a method of implanting an acetabular implant, comprising: fixing an acetabular shell to a mounting surface on an acetabulum, the acetabular shell having an inner surface and a lip portion defining an opening; coupling an engagement portion of a fitting ring to an edge portion of a liner such that an alignment portion of the fitting ring extends radially outward from the liner; and inserting the liner into the opening such that the alignment portion engages the lip portion of the acetabular shell; wherein engaging the alignment portion to the lip portion of the acetabular shell maintains the liner at a predetermined distance from the inner surface.

Optionally the method includes applying a driving force to the liner toward the acetabular shell to disengage the liner from the fitting ring and push the liner into engagement with the inner surface of the acetabular shell.

Optionally the method includes wherein the acetabular shell comprises a hemispherical shape and the inner surface is centered on an apex of the hemispherical shape; wherein the driving force is applied along an axis transverse to the apex.

Optionally the method includes wherein the fitting ring comprises a flexible material such that applying the driving force to the liner flexes the engagement portion to release the liner.

Further described herein is a fitting ring for inserting a liner into an acetabular shell, comprising: a fitting ring body including: an alignment portion on an exterior surface, the alignment portion defining extending circumferentially around the fitting ring, and an engagement portion on an interior surface defining an opening for receiving the liner; wherein the alignment portion is engageable to a lip portion of the acetabular shell to position the liner within the opening at a predetermined distance from the inner surface.

The drawings show, by way of illustration, specific embodiments in which the present subject matter can be practiced.

Claim 1:
An acetabular implant system (<NUM>), comprising:
an acetabular shell (<NUM>) including an inner surface (<NUM>) and a lip portion (<NUM>) defining an opening;
a liner (<NUM>) having an edge portion (<NUM>); and
a fitting ring (<NUM>), having an alignment portion (<NUM>) for correcting any pivoting of the liner (<NUM>) relative to the acetabular shell (<NUM>) and an engagement portion (<NUM>) engageable to the edge portion (<NUM>) of the liner (<NUM>) such that the alignment portion (<NUM>) extends radially outward from the liner (<NUM>);
wherein the alignment portion (<NUM>) is on an exterior surface of the fitting ring (<NUM>), the alignment portion (<NUM>) extending circumferentially around the fitting ring (<NUM>); wherein
the engagement portion (<NUM>) is on an interior surface (<NUM>) of the fitting ring (<NUM>) and defines an opening for receiving the liner (<NUM>), wherein
the alignment portion (<NUM>) is engageable to the circumference of the lip portion (<NUM>) of the acetabular shell (<NUM>) to position the liner (<NUM>) within the opening at a predetermined distance from the inner surface (<NUM>) of the acetabular shell; and
wherein the engagement portion (<NUM>) comprises an annular snap fit feature positioned on the interior surface (<NUM>) of the fitting ring (<NUM>).