HK1183429B - Acetabular cup prosthesis - Google Patents

Description

Acetabular cup prosthesis

Technical Field

The present application relates to hip implant devices and in particular to acetabular cup assemblies for use in hip surgery.

Background

Total hip replacement surgery typically entails removal and replacement of the femoral head and acetabulum. An acetabular cup assembly for replacing an acetabulum may include a shell portion and a liner insert that may be positioned within the shell.

In fact, surgeons implanting the shell and insert often have difficulty aligning these two components. Such difficulties may arise from the relatively small working space available to the surgeon during the hip replacement procedure, which may block the full view of the replacement components.

Disclosure of Invention

Provided are acetabular cup implants including a shell and a liner. An exemplary housing may have: an outer shell surface adapted for placement in a pelvic bone of a subject; the surface of the inner shell; a housing opening; and a rim positioned at a periphery of the housing opening and having a wave shape. The waveform shape has at least one peak and at least one valley.

The liner is adapted for insertion into the shell. An exemplary liner has: an outer liner surface; an inner liner surface; a liner opening; and a rim positioned about the liner opening and having a wave shape. The wavy shape of the liner has at least one peak and at least one valley. When the liner is inserted into the shell, at least a portion of the liner rim rests on at least a portion of the shell rim.

The at least one liner wave peak may rest within the at least one shell wave valley when the liner is inserted into the shell. Also, the at least one liner wave peak may rest on the at least one shell wave peak when the liner is inserted into the shell. Further, the at least one liner wave peak may rest on the shell rim wave shape at a location between the at least one shell wave peak and the at least one shell wave valley.

The liner may be rotated relative to the shell when inserted in a position where the liner peaks do not seat within the shell valleys. For example, the liner may be rotated relative to the shell such that the liner wave peak moves from a position where it rests on the shell wave peak or from a position where it rests between the shell wave peak and the shell wave valley into a position where the liner wave peak rests within the shell wave valley. Thus, the liner and shell may be rotated until the liner waveform shape and shell waveform shape are integrated, with one or more peaks of the liner and shell being seated in one or more valleys of the shell or liner, respectively. In this position, the wave geometry of the shell and liner are substantially congruent.

The shell rim and liner rim waveform shapes may each include a plurality of peaks and valleys. Each shell peak and shell valley may be equally spaced about the shell rim from each adjacent shell peak or shell valley. In some examples, the shell may have 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more shell peaks.

On the shell rim, each shell peak is separated from its adjacent shell peak by an angle that can be measured with respect to a shell axis perpendicular to the shell opening. Optionally, the angle, and thus the separation between peaks, is about 180 degrees, 120 degrees, 90 degrees, 72 degrees, 60 degrees, 51.4 degrees, 45 degrees, 40 degrees, or 36 degrees.

Example housings can also have 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more housing valleys. On the housing rim, each housing valley is separated from its adjacent housing valley by an angle that can be measured with respect to a housing axis perpendicular to the housing opening. Optionally, the angle, and thus the separation between peaks, is about 180 degrees, 120 degrees, 90 degrees, 72 degrees, 60 degrees, 51.4 degrees, 45 degrees, 40 degrees, or 36 degrees.

Similar to the shell peaks and valleys, each liner peak and each liner valley may be equally spaced about the liner rim from each adjacent liner peak or liner valley. Optionally, there are 2, 3, 4, 5, 6, 7, 8, 9, 10 or more liner peaks. Further, each liner peak is separated from its adjacent liner peak on the liner rim by an angle that can be measured relative to an axis of the liner perpendicular to the liner opening. Optionally, the angle, and thus the separation between peaks, is about 180 degrees, 120 degrees, 90 degrees, 72 degrees, 60 degrees, 51.4 degrees, 45 degrees, 40 degrees, or 36 degrees.

Example liners can also have 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more liner valleys. On the liner rim, each liner valley is separated from its adjacent liner valley by an angle that can be measured with respect to the liner axis perpendicular to the shell opening. Optionally, the angle is about 180 degrees, 120 degrees, 90 degrees, 72 degrees, 60 degrees, 51.4 degrees, 45 degrees, 40 degrees, or 36 degrees.

The described acetabular cup insert may further include a locking mechanism that is engageable when the liner and shell are placed in a position in which one or more liner peaks ride within one or more shell valleys. Engagement of the locking mechanism may secure the liner in the shell. Optionally, the locking mechanism is not engageable when the liner peak rests on the shell peak or when the liner peak rests between the shell peak and the shell valley.

When the liner is inserted into a position within the shell in which the peaks of the waveform shape of the liner rim are not aligned with the valleys of the waveform shape of the shell rim, the liner may be rotated relative to the shell until the peaks of the liner rim waveform shape ride in the valleys of the shell rim waveform shape. Once rotated into this seated position, a locking mechanism may be used to secure the shell and liner together.

Also provided is a method of seating a liner of an acetabular prosthetic assembly in its complementary shell. An exemplary method includes providing an acetabular cup assembly. The assembly includes a liner and a shell. The housing may include: an outer shell surface adapted for placement in a pelvic bone of a subject; the surface of the inner shell; a housing opening; and a rim positioned at a periphery of the housing opening and having a wave shape. The waveform shape may have at least one peak and at least one valley.

The liner is adapted for insertion into the shell. The liner comprises: an outer liner surface; an inner liner surface; a liner opening; and a rim positioned about the liner opening and having a wave shape. The waveform shape has at least one peak and at least one valley. The liner may be inserted into the shell such that at least a portion of the liner rim rests on at least a portion of the shell rim.

For example, at least one liner wave peak may rest on at least one shell wave valley when the liner is inserted into the shell. In another example, at least one liner wave peak rests on at least one shell wave peak when the liner is inserted into the shell. Further, when the liner is inserted into the shell, the at least one liner wave peak may rest on the shell rim waveform at a location between the at least one shell wave peak and the at least one shell wave valley.

When the liner is inserted into the shell in a position where the liner peak is not seated within the shell valley, the liner can be rotated relative to the shell such that the liner wave peak moves from a position where it rests on the shell wave peak or from a position where it rests between the shell wave peak and the shell wave valley into a position where the liner wave peak rests within the shell wave valley. In this position, a locking mechanism may be engaged to secure the liner to the shell with the shell wave crests being located within the shell wave troughs. In this position, the wave geometry of the shell and liner are substantially congruent.

These and other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art when considered in the following detailed description and accompanying drawings, which describe preferred and alternative embodiments of the invention.

Drawings

Fig. 1A-1C are schematic illustrations of an example shell of an acetabular cup assembly.

Figure 2A is a schematic illustration of an example shell of an acetabular cup assembly.

Fig. 2B is a schematic illustration of the housing shown in fig. 2A taken on section 2B-2B.

Fig. 2C is a schematic illustration showing a portion of fig. 2B in more detail.

Figure 2D is a schematic illustration of an example shell of an acetabular cup assembly.

Figure 2E is a schematic illustration showing a portion of an example shell of an acetabular cup assembly.

Fig. 3A and 3B are schematic illustrations of an example liner of an acetabular cup assembly.

Figure 4A is a schematic illustration of an example liner of an acetabular cup assembly.

Fig. 4B is a schematic illustration of the liner shown in fig. 4A taken on section 4A-4A.

Fig. 4C is a schematic illustration showing a portion of fig. 4B in more detail.

Figure 4D is a schematic illustration showing a portion of an example shell of an acetabular cup assembly.

Fig. 5A is a schematic illustration showing an example liner seated in an example shell of an acetabular cup assembly in a non-aligned state.

Fig. 5B is a schematic illustration showing an example liner resting in an aligned state in an example shell of an acetabular cup assembly.

Fig. 6A-6I are schematic illustrations showing an example housing having a waveform shaped rim.

Fig. 7A-7I are schematic illustrations showing an example liner having a wave shaped rim.

Detailed Description

The present invention will now be described more fully hereinafter with reference to specific embodiments thereof. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

As used in the specification and in the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

The term "comprising" and variations thereof as used herein is used synonymously with the term "including" and variations thereof, and they are open, non-limiting terms.

Total hip replacement surgery typically entails removal and replacement of the femoral head and acetabulum. An acetabular cup assembly for replacing an acetabulum may include a shell portion and a liner insert that may be positioned within the shell.

In fact, surgeons implanting the shell and insert often have difficulty aligning these two components. Such difficulties may arise from the relatively small working space available to the surgeon during the hip replacement procedure, which may block the full view of the replacement components. An acetabular cup assembly that can be effectively inserted into a patient under these potentially difficult surgical conditions is desirable.

Provided are acetabular cup implant assemblies that may be used in hip replacement surgery. An exemplary assembly includes a shell and a liner. The liner may be positioned within the shell. Optionally, the liner can be rotated relative to the shell until the liner is seated in the shell in a position in which the liner and shell can be fixed to each other. The wave-shaped features of the shell and liner may guide the relative rotation of the liner and shell. Also provided is a method of seating a liner in a shell of an acetabular cup implant assembly.

An example housing may have: an outer shell surface adapted for placement in a pelvic bone of a subject; the surface of the inner shell; a housing opening; and a rim positioned at a periphery of the housing opening and having a wave shape. The waveform shape has at least one peak and at least one valley. The peak or peaks are the point or points of the waveform nearest the opening of the housing. Similarly, the trough or troughs are the point or points of the waveform furthest from the opening of the housing.

The liner is adapted for insertion into the shell. An exemplary liner has: an outer liner surface; an inner liner surface; a liner opening; and a rim positioned about the liner opening and having a wave shape. The wavy shape of the liner has at least one peak and at least one valley. The peak or peaks are the point or points of the waveform nearest the liner opening. Similarly, the valley or valleys are the point or points of the waveform furthest from the liner opening. When the liner is inserted into the shell, at least a portion of the liner rim rests on at least a portion of the shell rim.

The at least one liner wave peak may rest within the at least one shell wave valley when the liner is inserted into the shell. Optionally, the shell and liner waveforms include the same number of peaks and valleys. Optionally, the angle between the peaks of the shell and liner waveforms is the same. The at least one liner wave peak may also rest on the at least one shell wave peak when the liner is inserted into the shell. Further, the at least one liner wave peak may rest on the shell rim wave shape at a location between the at least one shell wave peak and the at least one shell wave valley.

The liner may be rotated relative to the shell when inserted in a position where the liner peaks do not seat within the shell valleys. For example, the liner may be rotated relative to the shell such that the liner wave peak moves from a position where it rests on the shell wave peak or from a position where it rests between the shell wave peak and the shell wave valley into a position where the liner wave peak rests within the shell wave valley. Thus, the liner and shell may be rotated until the liner waveform shape and the shell waveform shape are integrated such that one or more peaks of the liner and shell are seated in one or more valleys of the shell or liner, respectively.

Referring to fig. 1A-1C, an example shell 100 of an acetabular cup assembly is illustrated. The shell 100 is sized and shaped to be positioned in a surgically prepared acetabular site. The housing 100 may comprise a metal or metal alloy, such as titanium or a titanium alloy. Optionally, the housing is machined from a metal or metal alloy as a single piece. Optionally, the housing may comprise separate pieces of the metal or metal alloy assembly.

The shell 100 has an outer surface 102 that can be placed and secured in an acetabular surgical site. The outer surface 102 is convex so that it may approximate the shape of the surgical site when properly seated. Optionally, the outer surface 102 is coated with a porous material that enhances the bonding of the shell to the pelvic bone at the surgical site. The porous material coating may comprise titanium or a titanium alloy. The shell 100 may also be engaged into an acetabular surgical site using a suitable surgical or bone cement.

The housing may further include a plurality of holes 106 that allow one or more fixation devices, such as screws, to be advanced through the housing and into the pelvic bone. By obtaining a fulcrum in the pelvic bone, the fixation devices can help to fix the housing in a desired position in the pelvis. In some example shells, the combination of fixation devices, cement, and bone growth (bonein-growth) into a porous material coated on the shell may secure the shell in the pelvis.

The housing 100 may also include one or more spikes 128. Spikes 128 extend from the outer surface 102 of the housing. The spikes 128 may penetrate the pelvic bone to provide fixation of the housing to the pelvis. Optionally, as shown in fig. 1C, the holes 106 are not used with a housing that includes spikes 128.

The inner surface 104 of the shell 100 is concave and may be sized and shaped for seating a liner insert 300. The liner insert is also referred to herein as a liner. An exemplary liner 300 is shown in fig. 3A, 3B, 4A-4D, and 7A-7I. The inner surface 104 of the housing 100 may be made of the same material as the outer surface 102. Optionally, the housing 100 may be machined from a single piece of metal comprising titanium or a titanium alloy. As previously discussed, the outer surface 102 may be coated with a porous coating, which may also comprise titanium or a titanium alloy.

The housing 100 may further include an inner rim 108 and an outer rim 114. The inner rim 108 and the outer rim 114 may each be arcuate or annular. In this manner, the rim may frame the primary opening 113 that will receive the shell liner 300. As with the inner and outer surfaces (102 and 104, respectively), the rim portions (108 and 114) of the shell may be titanium or an alloy containing titanium. The outer rim 114 may include a wave shape having peaks 118 and valleys 122. The waveform may have a varying number of peaks and troughs as described in more detail below with respect to fig. 6A-6I.

One or more slots 116 for disengaging the liner 300 from the shell 100 may be positioned around the rim of the shell. The slot 116 may extend through the outer rim 114 or through both the outer rim 114 and the inner rim 108. The slots 116 may prevent the outer rim 114 from completing the full circular path. Thus, the outer rim may include two or more arcuate segments depending on the number of slots 116.

The slot 116 has an opening defined by the outer surface 102 of the housing. For example, if the slot is rectangular or square, the bottom and sides of the slot opening may be defined by the outer surface 102 of the housing. The top of the opening may be defined by a portion of the liner when the liner is seated within the shell. For example, as shown in FIG. 5B, the slots may be defined by other shell surfaces 102 and the wave shape of the liner 300.

Similarly, the inner rim 108 may be interrupted by one or more slots 116. The slots 116 may prevent the inner rim 108 from completing the full annular path. Thus, the outer rim may also include two or more arcuate segments depending on the number of slots 116.

The slot 116 may be sized and shaped to allow insertion of a tool or instrument that may provide leverage for separating the liner 300 from the shell 100. For example, when the liner 300 is seated within the shell 100, a tool having a flattened portion may be inserted into the slot 116 and under the backside of the liner 300. The tool may then be manipulated by an operator to cause or facilitate separation of the installed liner from the shell.

The inner rim 108 may also include a locking mechanism 110. The locking mechanism 110 extends from the horizontal plane of the inner rim 108. The locking mechanism 110 may be arcuate or annular. For example, if the inner rim 108 (including the locking mechanism 110) is interrupted by one or more slots 116, the locking mechanism 110 may include two or more arcuate segments.

The cross-sectional shape of the locking mechanism may vary. In the illustrated example, the locking mechanism 110 has a hump cross-sectional shape. For example, as shown in fig. 2C, the cross-sectional shape of the locking mechanism 110 is a hump extending from the inner rim 108. More specifically, the cross-sectional shape of the locking mechanism 110 may be part circular, with the center 230 of the circular portion being located above the level of the inner rim 108.

By having a center 230 of a circular portion above the inner rim plane, a complementary portion of the liner 300 can be locked onto the locking mechanism 110. For example, the locking mechanism 110 of the shell may mate with the groove 326 of the liner 300. The groove 326 is shown, for example, in fig. 4B-4D.

The groove 326 may include a circular cross-sectional void that is complementary to the hump shape of the locking mechanism 110. The center of the circular cross-section of the groove 326 may have a center 327 that is offset from the plane P shown in FIG. 4C₁-P₁In (1). When the groove 326 and the locking mechanism 110 include complementary shapes with offset centers, lips are created on the inner and outer edges of the groove opening that can mate with indents created at the junction of the locking mechanism 110 and the inner rim 108. These complementary shapes help lock the liner 300 to the shell 100 when the liner 300 is seated in the shell 100 for use.

Referring again to fig. 1A-1C, the outer rim 114 has a wave shape. The waveform shape includes peaks 118 and valleys 122. The angle between successive peaks 118 or valleys 122 may be determined with reference to the central axis a-a of the housing shown in fig. 1C and in fig. 6A-6I.

Referring particularly to fig. 6A-6I, spokes B drawn perpendicular to axis a-a intersect the apex of each peak. The angle (α) represents the angle between peaks. For example, in fig. 6A, two peaks 118 are shown, each with an angle (α) of 180 ° between them. In fig. 6B, a third peak is added, with an angle (α) of 120 ° between the peaks. In each successive example shown in fig. 6C to 6I, additional peaks are shown. The angle (α) between the peaks can be determined by dividing 360 ° by the total number of peaks. Thus, by way of example, fig. 6G shows an example housing having eight peaks. By dividing 360 ° by the total number of peaks (eight), the angle (α) between the peaks was determined to be 45 °.

The number of peaks may vary. Optionally, two or more peaks may be present. For example, there may be 2, 3, 4, 5, 6, 7, 8, 9, 10, or more peaks, and the angle between these peaks may be about 180, 120, 90, 72, 60, 51.4, 45, 40, or 36 degrees. Further, these peaks are not necessarily uniformly distributed as shown in fig. 1A to 1C and in fig. 6. In this regard, the angle between the peaks may vary. Thus, the shell may comprise a wave form having a plurality of peaks, wherein the angle between one or more peaks is the same or different. In the example of angle variation, the angle between peaks may vary from less than one degree to greater than 359 degrees. When the angles between the peaks and valleys are the same, the peaks and valleys are uniformly distributed in the shell as shown in fig. 1A to 1C and in fig. 6A to 6I, and are uniformly distributed in the liner as shown in fig. 3A and 3B and in fig. 7A to 7I. In these aspects, positioning options are increased in which the liner waveform is substantially congruent with the shell waveform.

Fig. 2A-2D are schematic illustrations showing portions of an example housing in greater detail. Fig. 2B is a schematic cross-sectional view taken on the plane B-B of fig. 2A. Fig. 2B shows a hole 220, which may be threaded, positioned through the wall of the housing 100 on the bottom of the concave inner surface 104 of the housing. If the aperture 220 is threaded, it may be used to accept a tool having a complementary thread pattern for assisting in inserting the housing into the surgical site.

Fig. 2C is a detailed illustration of the circled portion from fig. 2B, showing a cross-section of the locking mechanism 110 with a center 230. Fig. 2D is a schematic perspective view of the example housing 100, showing the inner surface 104, the outer surface 102, an outer rim 114 comprising a wave form having a plurality of peaks 118 and valleys 122, and the inner rim 108 having a locking mechanism 110 that extends from the location of the inner rim 108. Fig. 2D further illustrates three slots 116 for inserting a tool and disengaging the mating shell and liner. In this configuration, the slots 116 divide the inner rim 108 and the outer rim 114 into three sections. Each segment includes an arcuate locking mechanism 110. The number of slots 116, peaks 118, valleys 122, segments, locking mechanisms 110 may vary.

Referring now to fig. 3A and 3B, an example liner is illustrated. Referring to fig. 3A, the liner 300 is sized and shaped for placement within the shell 100. The liner includes an outer surface 310 and an inner surface 308. When the liner 300 is seated within the shell, portions of the outer surface 310 contact the inner surface 104 of the shell. Optionally, the outer surface 310 is highly congruent with the inner surface 104 during use to evenly distribute stresses between the shell 100 and liner 300 components.

The inner surface 308 is also configured to articulate with a portion of a femoral head of a femur or with a femoral portion of a stem implant for hip replacement. The liner component may comprise polyethylene. For example, the liner component may be made of ultra high molecular weight polyethylene. Ultra-high molecular weight polyethylene is commonly used in hip replacement prostheses and typically comprises polyethylene that has been at least partially cross-linked.

The outer diameter of the liner may also vary. For example, the outer diameter of the liner may vary from about 32 millimeters (mm) to about 50.5 mm. The landmarks of the liner inner and outer diameters are shown in FIG. 4D. Referring to fig. 4D, in some examples, the liner outer rim 313 has a thickness (D). Optionally, the thickness may be about or between 1mm or 2 mm. For example (D) may optionally be 1.3 mm. The thickness (C) of the liner inner rim 325 may be between about or 1mm or 2 mm. Optionally, the thickness of the inner and outer rims is constant over all sizes of liner inner and outer diameters of the liner.

The varying sizes of the liner 300 may be matched to various shell 100 sizes. Landmarks of the inner and outer diameters of the exemplary housing are shown in fig. 2E. Referring to fig. 2E, in some examples, the housing outer rim 114 has a thickness (x). Optionally, the thickness may be about or between 1mm or 2 mm. For example, (x) may optionally be 1.3 mm. The thickness (C) of the housing inner rim 108 may be about or between 1mm or 2 mm. Optionally, the thickness of the inner and outer rims is constant over all sizes of the liner inner and outer diameters of the shell.

The Inner Diameter (ID) of the housing 100 may vary, for example, from about 32mm to about 50.5 mm. The Outer Diameter (OD) of the housing 100 may vary, for example, from about 40mm to about 60 mm. The liner 300 may have an Inner Diameter (ID) from about 22mm to about 32 mm. Optionally, the inner diameter may be 22, 28, 32 or 36 mm. The Outer Diameter (OD) of the liner may vary from about 32 to 50 mm.

Table 1 shows exemplary, non-limiting combinations of the sizes (in millimeters) of the liner 100 and the corresponding shell 300 based on the inner and outer diameters. Other size combinations of liners and shells and liner/shell combinations beyond those described in table 1 may be used. For example, it may be desirable to use larger liner and/or shell Inner Diameters (IDs) with larger femoral head components. Appropriate liner and shell sizes may be selected from those listed in table 1 or from other sizes based on various medical/surgical considerations. For example, a surgeon or other medical professional may determine the appropriate shell and liner sizes and combinations thereof by evaluating the medical conditions in which the devices will be used.

The liner can be configured to articulate with a variety of femoral heads having different femoral head diameters. The thickness of the liner polyethylene may optionally be at least 6 mm. For example, the liner may be sized and shaped to articulate with a femoral head having a diameter from about 22 millimeters (mm) to 36 mm.

Optionally, the liner Outer Diameter (OD) is equal in size to the shell Inner Diameter (ID). The housing OD may be equal to housing ID +2 x C +2 x. The liner rim OD may be equal to liner OD + 2C +2 d.

TABLE 1

Referring again to fig. 3A and 3B, the liner 300 and the liner 302 may further include fillets 316 and chamfers 306 that transition the inner surface 308 to the liner rim 304. The combination of the rounded corners 316 and the chamfers 306 provide a smooth transition between the generally vertical wall portions of the inner surface 308 and the rim 304, while also allowing for increased range of motion of the femoral implant when articulated with the liner.

The rim 304 includes a wave pattern having peaks 312 and valleys 314. The liner rim wave shaped corrugations may complement the shell rim wave shaped corrugations. Optionally, the liner rim has the same number of corrugations as the shell rim. Further, the amplitude of the shell rim corrugations may be the same or similar to the liner rim corrugations.

As shown in fig. 3B, the liner 302 may further include a ridge 318. The ridges 318 help prevent the femoral implant component from becoming dislodged from the liner during use. The spine may be excellently positioned during surgery to limit movement of the femoral neck so that the head of the femoral component is less likely to be displaced from the liner socket.

The ridge 318 may have a transition region 320 on each side of the ridge 318 rising from the rim 304. The transition zone reduces sharp edges on the liner and thereby reduces the likelihood of soft tissue damage. Similarly, a rounded, radiused portion 324 is positioned on top of the ridge 318. The rounded, radiused portion 324 reduces sharp edges on the liner, thereby reducing the likelihood of soft tissue damage.

Referring now to fig. 4A-4C, portions of an example liner are schematically illustrated in more detail. Fig. 4B is a schematic cross-sectional view taken on the plane B-B of fig. 4A. Fig. 4B shows the rounded corners 316 and chamfers 306 of the inner surface 308 of the housing. Fig. 4C shows a detail of the circular portion C from fig. 4B. Fig. 4C shows a cross section of the groove 326 with a center 327. Center 327 lies in plane P₁-P₁Below.

Referring now to fig. 7A-7I, the number of peaks and valleys of the liner waveform may vary. Similar to the waveform of the shell, the liner waveform has a plurality of peaks separated by peak-to-peak angles (β) relative to an axis Y-Y extending through the center of the liner. Accordingly, the angle between the peaks 312 may be determined with reference to the central axis Y-Y of the housing shown in fig. 7A to 7I. Spokes drawn perpendicular to axis Y-Y intersect the peaks 312 of each liner corrugation. The angle (β) represents the angle between peaks. For example, in fig. 7A, two peaks 312 are shown, each with an angle (β) of 180 ° between them. In fig. 7B, a third peak is added, with an angle (β) of 120 ° between the peaks. In each successive example shown in fig. 7C to 7I, additional peaks 312 are shown, and the angle (β) between the peaks can be determined by dividing 360 ° by the total number of peaks.

Thus, by way of example, fig. 7G shows an example device having eight peaks. By dividing 360 ° by the total number of peaks (eight), the angle (β) between the peaks 312 is determined to be 45 °. The number of peaks may vary. Optionally, there may be two or more peaks 312. For example, there may be 2, 3, 4, 5, 6, 7, 8, 9, 10, or more peaks, and the angle between these peaks may be about 180, 120, 90, 72, 60, 51.4, 45, 40, or 36 degrees. Further, these peaks are not necessarily uniformly distributed as shown in fig. 7A to 7I. In this regard, the angle between the peaks 312 may vary. The liner may include a wave form having a plurality of peaks, wherein the angle between one or more peaks is the same or different. The angle between peaks may vary from less than one degree to greater than 359 degrees. As described above, when the angles between the peaks and valleys are the same, the peaks and valleys are uniformly distributed in the shell as shown in fig. 1A to 1C and 6A to 6I, and are uniformly distributed in the liner as shown in fig. 3A and 3B and 7A to 7I. In these aspects, positioning options are increased in which the liner waveform is substantially congruent with the shell waveform.

Referring to fig. 5A and 5B, a liner 300 may be positioned within the shell 100. As shown in fig. 5A, the liner 300 may be positioned in an misaligned position with the shell 100. As shown in fig. 5B, the liner 300 may be positioned in an aligned position with the shell 100. In the non-aligned position shown in fig. 5A, the peaks 312 of the liner rim 304 waveform do not ride in the valleys 122 of the waveform in the outer rim 114. Similarly, the peaks 118 of the shell outer rim 114 waveform do not rest in the valleys 314 of the liner rim 304.

In the non-aligned position, one or more gaps 602 are located between the articulating surfaces of the shell outer rim 114 and the liner rim 304. In this position, the liner 300 and the shell 100 may rotate relative to each other. Optionally, the liner 300 and the shell 100 may be rotated relative to each other such that the undulating surfaces of the outer rim 114 of the shell 100 and the rim 304 of the liner slide over each other until the one or more peaks 118 of the outer shell rim 114 ride within the one or more valleys 314 of the liner rim 304.

The corresponding undulations of the shell 100 and liner 300 allow the shell and liner to be initially positioned with one or more valleys and peaks out of alignment as shown in fig. 5A. The shell and liner may then be rotated into an aligned position for locking. When rotated into the aligned position shown in fig. 5B, the housing locking mechanism 110 may be positioned within the liner groove 326. The locking mechanism 110 and the groove 326 may be sized and shaped such that they snap together to form a secure connection, such as by a friction fit or by the groove 326 being twisted by the locking mechanism 110. Interference caused by peak-to-peak contact prevents planar alignment of the locking mechanism and the groove and prevents secure locking until the shell and liner are rotated into peak-to-valley alignment, respectively.

An operator of the device (e.g., a surgeon) can easily rotate, mate, and lock the shell and liner without looking at the shell and/or liner. The corresponding waveforms of the shell and liner may facilitate proper positioning of the shell and liner during a surgical procedure that limits or obstructs the field of view of the surgeon. Further, positioning the locking mechanism 110 into the groove 326 may create an audible sound for an operator to provide another indication that the liner 300 is locked in the shell 100. The distance that the liner and shell are rotated relative to each other prior to mating and locking may vary depending on the period of the respective waveforms of the shell and liner.

For example, a greater number of peaks and valleys with corresponding smaller angles or periods between peaks may require less rotation of the liner relative to the shell prior to alignment and locking. Similarly, a fewer number of peaks and valleys with corresponding larger angles or periods between the peaks may require more rotation of the liner relative to the shell prior to alignment and locking. Thus, shells and liners having different wave shapes may be selected depending on the desired rotational distance. After the liner is initially placed into the shell, if the surgeon wants little rotation of the shell and liner relative to each other, a shell and liner combination having a greater number of peaks and valleys relative to a shell and liner combination that wants more rotation before mating can be used. When a liner having ridges 318 is used, the greater number of peaks and valleys results in a greater number of options for rotationally positioning the ridges relative to the shell and the patient.

When positioned in the aligned position, the aligned shell and liner waveforms provide resistance to additional rotational movement. The locking mechanism 110, when positioned within the groove 326, also provides resistance to rotational movement. Thus, the acetabular cup assembly allows the shell and liner to be guided to a position in which the liner is secured in place by the aligned waveforms and the interaction of the locking mechanism 110 with the groove 326. The locked shell 100 and liner 300 may be separated by placing a tool into the slot 116 and leveraging the shell 100 and liner 300 apart.

Also provided is a method of seating a liner of an acetabular prosthetic assembly in its complementary shell. An exemplary method includes providing an acetabular cup assembly. The assembly includes a liner and a shell. The housing may include: an outer shell surface adapted for placement in a pelvic bone of a subject; the surface of the inner shell; a housing opening; and a rim positioned at a periphery of the housing opening and having a wave shape. The waveform shape may have at least one peak and at least one valley.

The liner is adapted for insertion into the shell. The liner comprises: an outer liner surface; an inner liner surface; a liner opening; and a rim positioned about the liner opening and having a wave shape. The waveform shape has at least one peak and at least one valley. The liner may be inserted into the shell such that at least a portion of the liner rim rests on at least a portion of the shell rim.

For example, at least one liner wave peak may rest on at least one shell wave valley when the liner is inserted into the shell. In another example, at least one liner wave peak rests on at least one shell wave peak when the liner is inserted into the shell. Further, when the liner is inserted into the shell, the at least one liner wave peak may rest on the shell rim waveform at a location between the at least one shell wave peak and the at least one shell wave valley.

When the liner is inserted into the shell in a position where the liner peak is not seated within the shell valley, the liner can be rotated relative to the shell such that the liner wave peak moves from a position where it rests on the shell wave peak or from a position where it rests between the shell wave peak and the shell wave valley into a position where the liner wave peak rests within the shell wave valley. In this position, a locking mechanism may be engaged to secure the liner to the shell with the shell wave crests being located within the shell wave troughs.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (21)

1. An acetabular cup implant, comprising:

a housing having: an outer shell surface adapted for placement in a pelvic bone of a subject; the surface of the inner shell; a housing opening; and a rim positioned about the housing opening and having a wave shape with at least one peak and at least one valley and a smooth articulating surface extending between the at least one peak and the at least one valley; and

a liner adapted for insertion into the shell, the liner having: an outer liner surface; an inner liner surface; a liner opening; and a rim positioned peripherally of the liner opening and having a wave shape with at least one peak and at least one valley and a smooth articulating surface extending therebetween;

wherein the smooth articulating surface of the shell and the smooth articulating surface of the liner are in contact with each other and guide relative movement of the shell and the liner from a first position to a second position: in the first position the peaks of the waveform of the rim of the shell are not located in the troughs of the waveform of the rim of the liner, in the second position the peaks of the waveform of the rim of the shell are located in the troughs of the waveform of the rim of the liner.

2. The acetabular cup implant of claim 1, wherein the shell rim and the liner rim waveform shapes each comprise a plurality of peaks and valleys.

3. The acetabular cup implant of claim 2, wherein each shell peak and shell valley are equally spaced about the shell rim from each adjacent shell peak or shell valley.

4. The acetabular cup implant of claim 3, wherein there are 2, 3, 4, 5, 6, 7, 8, 9, or 10 shell peaks.

5. The acetabular cup implant of claim 4, wherein each shell peak on the shell rim is separated from its adjacent shell peak by an angle measured relative to an axis of the shell perpendicular to the shell opening.

6. The acetabular cup implant of claim 5, wherein the angle is about 180, 120, 90, 72, 60, 51.4, 45, 40, or 36 degrees.

7. The acetabular cup implant of claim 3, wherein there are 2, 3, 4, 5, 6, 7, 8, 9, or 10 shell valleys.

8. The acetabular cup implant of claim 7, wherein each shell valley is separated from its adjacent shell valley on the shell rim by an angle measured relative to an axis of the shell perpendicular to the shell opening.

9. The acetabular cup implant of claim 2, wherein each liner peak and each liner valley are equally spaced about the liner rim from each adjacent liner peak or liner valley.

10. The acetabular cup implant of claim 2, wherein there are 2, 3, 4, 5, 6, 7, 8, 9, or 10 liner peaks.

11. The acetabular cup implant of claim 9, wherein each liner peak on the liner rim is separated from its adjacent liner peak by an angle measured relative to an axis of the liner perpendicular to the liner opening.

12. The acetabular cup implant of claim 11, wherein the angle is about 180, 120, 90, 72, 60, 51.4, 45, 40, or 36 degrees.

13. The acetabular cup implant of claim 2, wherein there are 2, 3, 4, 5, 6, 7, 8, 9, or 10 liner valleys.

14. The acetabular cup implant of claim 2, wherein each liner valley is separated from its adjacent liner valley on the liner rim by an angle relative to an axis of the liner perpendicular to the shell opening.

15. The acetabular cup implant of claim 14, wherein the angle is about 180, 120, 90, 72, 60, 51.4, 45, 40, or 36 degrees.

16. The acetabular cup implant of claim 1, further comprising a locking mechanism that is engageable when the liner and shell are placed in a position in which one or more liner peaks ride within one or more shell valleys.

17. The acetabular cup implant of claim 16, wherein engagement of the locking mechanism secures the liner in the shell.

18. The acetabular cup implant of claim 1, wherein the implant further comprises at least one slot having an opening defined by the outer shell surface and a portion of the liner.

19. The acetabular cup implant of claim 18, wherein the slot extends between the shell and liner toward an inner surface of the shell.

20. The acetabular cup implant of claim 19, wherein the slot is adapted to receive a tool to provide leverage for facilitating removal of the liner from the shell.

21. The acetabular cup implant of claim 18, wherein the portion of the liner defining the slot is a portion of the rim.