Prosthetic assembly

A prosthetic assembly comprising: a body portion; first and second flanges provided on a rim of the body portion; the first and second flanges being provided with first and second openings respectively; and a bridging member connectable to the first and second flanges such that the member spans between the first and second flanges, the member being provided with a third opening; wherein the first, second and third openings are suitable for receiving first, second and third bone attachment members respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Stage of International Application No. PCT/GB2010/051236, filed Jul. 28, 2010. This application claims priority to Great Britain Patent Application No. GB-0913137.6, filed Jul. 28, 2009. The disclosures of the above applications are incorporated herein by reference.

FIELD

This invention relates to a prosthetic assembly and particularly but not exclusively relates to a prosthetic assembly with one or more openings, which are adapted to receive attachment members for attaching the prosthesis to bone.

BACKGROUND

A natural hip joint may undergo degenerative changes due to a variety of etiologies. When these degenerative changes become far advanced and irreversible, it may ultimately become necessary to replace a natural hip joint with a prosthetic hip. When implantation of such a hip joint prosthesis becomes necessary, the head of the femur, the acetabular, or both may need to be replaced. The head of the natural femur is first resected and a cavity is created within the intramedullary canal of the host femur for accepting the hip prosthesis. The hip prosthesis may be inserted and supported within the host femur by cementing the hip prosthesis within the host femur. Alternatively, the hip prosthesis may be impacted into the host femur so that it is a snug fit and supported by the host femur. In a further alternative, the femur may also be resurfaced, in which case the head is not resected. If the acetabulum also needs repair, all remnants of articular cartilage are generally removed from the acetabulum and an acetabular prosthesis which will accommodate the head or ball of the hip prosthesis is affixed to the acetabulum. The acetabular prosthesis is affixed to the acetabulum by means of cement, screws, an uncemented press fit or other appropriate fixation means.

Due to any number of reasons, however, a small portion of patients that undergo such orthopaedic surgical procedures may require subsequent revision surgery to replace the prosthetic device with a new prosthetic device generally referred to as a revision prosthesis.

In this regard, a revision acetabular prosthesis will generally include additional mounting points, such as integral extension members or hooks that provide additional stability for the revision acetabular prosthesis. These additional mounting points are generally required due to additional bone loss or defects exhibited at the acetabulum, such as collar/rim defects or pelvic discontinuity defects.

Various types of revision acetabular prostheses are currently available and different surgeons prefer different types of revision acetabular prostheses. Some surgeons prefer to use what is known as an Ilium flange that is formed integral with the acetabular prosthesis and enables further securement of the acetabular prosthesis in the Ilium region of the pelvis. Other surgeons prefer to use what is known as an obturator hook that is able to provide inferior fixation of the acetabular prosthesis by engaging the obturator foramen which is a large aperture adjacent the acetabulum. Because of this, a hospital must maintain a large inventory of different revision acetabular cups to meet the various surgeons' preferences. Moreover, the surgeon generally requires several revision acetabular cups available during surgery to account for any type of condition that may arise during the surgical procedure. Furthermore, as it may be desirable to have asymmetric securement to the acetabulum, left and right-handed revision acetabular cups may also be required.

This increased inventory of prosthetic devices increases the overall hospital costs and inventory control. Furthermore, by requiring the multiple revision acetabular cups to be available during the surgical procedure, multiple tools for the prosthetic devices may be required and these must be sterilized prior to the surgical procedure, thereby increasing the surgical time, cost and complexity. The present embodiments therefore seek to address these issues.

SUMMARY

According to a first aspect, there is provided a prosthetic assembly comprising: a body portion; first and second flanges provided on a rim of the body portion; the first and second flanges being provided with first and second openings respectively; and a bridging member connectable to the first and second flanges such that the member spans between the first and second flanges, the member being provided with a third opening; wherein the first, second and third openings are suitable for receiving first, second and third bone attachment members respectively.

The first opening may be disposed such that the first bone attachment means, once received in the first opening, may be orientated in a first plane containing a centreline of the body portion. The second opening may be disposed such that the second bone attachment member, once received in the second opening, may be orientated in a second plane containing a centreline of the body portion.

The first and/or second openings may be disposed such that the axes of the first and/or second openings may be angled in the range of substantially +60 to substantially −60 degrees with respect to the centreline of the body portion. The first and/or second openings may be disposed such that the axes of the first and/or second openings may be angled at substantially +20 or −20 degrees with respect to the centreline of the body portion.

The third opening may be disposed such that the third bone attachment member, once received in the third opening, may be oblique to a third plane containing a centreline of the body portion and the third opening. In addition to the third, fourth and fifth openings, the bridging member may comprise further openings for receiving further bone attachment members.

The bridging member may comprise fourth and fifth openings. The fourth opening may be disposed so as to overlap the first opening of the first flange and the fifth opening may be disposed so as to overlap the second opening of the second flange. The fourth and fifth openings may be disposed such that the first bone attachment member, once received in the first opening, may pass through the fourth and first openings and the second bone attachment member, once received in the second opening, may pass through the fifth and second openings. The first and second bone attachment members may be capable of securing the bridging member to the first and second flanges. Alternatively, the bridging member may be secured to the first and second flanges by first and second securing members, for example screws, which pass through the fourth and fifth openings respectively. The first and second securing members may pass into the first and second openings respectively. The first and second securing members may not pass into the bone.

The body portion may comprise a recess to receive an auxiliary bone engaging component. The auxiliary bone engaging component may comprise at least one of a compression screw, an Iliac plate, an Ischial blade, an Obturator hook and an augment.

The body portion may comprise an acetabular cup. The body portion may be a monoblock. The body portion may comprise a bearing surface, and as such the body portion may form a first bearing component, which may be configured to receive and cooperate with a second bearing component, for example the head of a femur.

Alternatively, the body portion may comprise a fixation element which may be fixedly attached to another element, for example as part of a shoulder, knee or spinal prosthetic. The body portion may not require a separate liner for engagement with the second bearing component. Nevertheless, a liner may be inserted between the body portion and the second bearing component Furthermore, the body portion and/or second bearing component may comprise a coating, for example a ceramic or diamond coating.

At least one of the first and second flanges may be angled with respect to the rim of the body portion. At least one of the first and second flanges may be provided with securing members for securing a drill guide to the first and/or second flange. The bridging member may be provided with further securing members for securing a further drill guide to the bridging member.

According to a second aspect there is provided a kit of parts for a prosthesis, the kit of parts comprising: a body portion; first and second flanges provided on a rim of the body portion; the first and second flanges being provided with first and second openings respectively; and a first bridging member connectable to the first and second flanges such that the first bridging member spans between the first and second flanges, the first bridging member being provided with a third opening; wherein the first, second and third openings are suitable for receiving first, second and third bone attachment members respectively.

The third opening may be disposed such that the third bone attachment member, once received in the third opening, may be oblique to a third plane containing a centreline of the body portion and the third opening.

The kit of parts may further comprise a second bridging member connectable to the first and second flanges such that the second bridging member may span between the first and second flanges. The second bridging member may be provided with a sixth opening suitable for receiving the third bone attachment member. The sixth opening may be disposed such that the third bone attachment member, once received in the sixth opening, may be oblique to the third plane in a direction opposite to that of the third opening of the first bridging member. In other words, the first and second bridging members may correspond to left- and right-handed bridging members, which are the mirror image of one another.

The kit of parts may further comprise at least one of a compression screw, a locking screw, a screw plate (e.g. an Iliac plate), a fixation blade (e.g. an Ischial blade), a hook (e.g. an Obturator hook) and an augment. The kit of parts may further comprise at least one drill guide for attachment to at least one of the first flange, second flange, first bridging member and second bridging member.

According to a third aspect there is provided a method of installing a prosthetic assembly, the method comprising: providing a body portion with first and second flanges provided on a rim of the body portion; the first and second flanges being provided with first and second openings respectively; connecting a first bridging member to the first and second flanges such that the first bridging member spans between the first and second flanges, the first bridging member being provided with a third opening; and affixing the prosthetic assembly to a bone by passing a third bone attachment member through the third opening. The method may further comprise affixing the prosthetic assembly to the bone by passing one or more of first and second bone attachment members through the first and second openings respectively.

According to a fourth aspect here is provided a hook for a prosthetic acetabular cup, wherein the hook comprises one or more gripping elements adapted to grip a portion of the pelvic obturator. The gripping elements may comprise a saw-tooth arrangement, for example with a repeating right-angled triangular cross-section, which may engage with the obturator.

The hook may comprise a first hole for receiving a screw to secure the hook to the prosthesis. The hook may be shaped so as to curve back on itself like a fish hook and may comprise a curved back portion. The hook may comprise a second hole which may be located on the curved back portion. The second hole may be opposite the first hole. Accordingly, the second hole may permit a tool to pass through the curved back portion so as to be able to access the screw which may be received in the first hole.

DETAILED DESCRIPTION

With reference toFIG. 1, a prosthetic assembly10according to a first embodiment comprises a body portion12in the form of a substantially hemispherical acetabular cup and first and second flanges14,16provided on a rim18of the body portion12. The first and second flanges14,16are provided with first and second openings20,22respectively. The prosthetic assembly10further comprises a bridging member24connectable to the first and second flanges14,16such that the member24spans between the first and second flanges. The member24is provided with a third opening26. The first, second and third openings20,22,26are suitable for receiving first, second and third bone attachment members or means28,30,32respectively for securing the prosthetic assembly10to a bone, for example the acetabulum. The bone attachment members may for example comprise bone attachment pins or screws. The first, second and/or third openings may be threaded bores and may for example be threaded to receive a threaded bone screw.

The body portion12is substantially hemispherical and the rim18corresponds to a great circle of the hemisphere. In other words, the rim18is within a plane which cuts through the centre of the sphere that defines the hemisphere. The body portion12comprises a bearing surface34, and as such the body portion12may form a first bearing component, which is configured to receive and cooperate with a second bearing component (not shown), for example the head of a femur. Alternatively, the body portion12may comprise a fixation element which is fixedly attached to another element, for example as part of a shoulder, knee or spinal prosthetic. However, the body portion12of the present embodiment is a monoblock acetabular cup. As such the body portion12does not require a separate liner for engagement with the second bearing component. Nevertheless, a liner may be inserted between the body portion12and the second bearing component. Furthermore, the body portion and/or second bearing component may comprise a coating, for example a ceramic or diamond coating.

The first opening20is disposed such that an axis of the first opening is orientated in a first plane containing a centreline of the body portion12. The axis of the first opening is coincident with the longitudinal axis of the first bone attachment member in the case of a straight bone attachment member. Similarly, the second opening22is disposed such that an axis of the second opening is orientated in a second plane containing a centreline of the body portion. The axis of the second opening is coincident with the longitudinal axis of the second bone attachment member in the case of a straight bone attachment member.

One or more of the first and second openings20,22are configured such that one or more of the first and second bone attachment members28,30, once received in the first and/or second opening, are angled towards the centreline of the body portion12so as to intersect the centreline above or below the centre of the body portion. (Above and below relate to the orientation of the body portion shown inFIGS. 1 to 3.) The first and/or second openings may be disposed such that the axes of the first and/or second openings may be angled in the range of substantially +60 to substantially −60 degrees with respect to the centreline of the body portion. (Positive angles relate to an intersection of the axes with the centreline above the centre of the body portion, whilst negative angles relate to an intersection of the axes with the centreline below the centre of the body portion.) In particular, the first and/or second openings may be disposed such that the axes of the first and/or second openings may be angled at substantially +20 or substantially −20 degrees with respect to the centreline of the body portion. The first and second bone attachment members28,30may be at the same angle such that the centreline of the body portion12and the axes of the first and second bone attachment members28,30converge on a single point. Furthermore, the first and/or second openings may be disposed such that the axes of the first and/or second openings may be orientated cranially into the antero-superior part of the Ilium.

The outer faces of the first and/or second flanges14,16are angled with respect to the plane containing the rim18of the body portion12. (The outer face being the face of the first or second flange which does not face the bone.) The angle of the outer face may correspond to the angle of the bone attachment member with respect to the centreline of the body portion12. For example, the outer face of the first and/or second flange may be at 20 degrees with respect to the rim18. Furthermore, the outer faces of the first and/or second flanges may have features or shapes, which may interact with corresponding features or shapes in the bridging member. The features or shapes may provide additional fixation stability to the bridging member.

The third opening26is disposed such that the third bone attachment member32, once received in the third opening, is oblique to a third plane containing a centreline of the body portion12and the third opening26. Accordingly, the third bone attachment member32does not converge on the centreline of the body portion12and the third bone attachment means32diverges away from the first and second bone attachment members28,30. Alternatively, the third opening may be disposed such that the third bone attachment means may converge on the centreline of the body portion12. The third bone attachment member32therefore secures the prosthetic assembly to a different region of bone. The third bone attachment member32also secures the body portion12in a different direction. The body portion12is therefore prevented from coming loose due to the failure of bone in one region or a force in a particular direction.

In addition to the third opening26, the bridging member24further comprises fourth and fifth openings36,38. Once the bridging member24is installed, the fourth opening36is disposed so as to overlap the first opening20of the first flange14and the fifth opening38is disposed so as to overlap the second opening22of the second flange16. The fourth and fifth openings36,38are disposed such that the first bone attachment member28, once received in the first opening20, passes through the fourth and first openings. Similarly, the second bone attachment member30, once received in the second opening22, passes through the fifth and second openings. The first and second bone attachment members28,30may be capable of securing the bridging member24to the first and second flanges, for example by virtue of a head portion. The head portion may abut the fourth or fifth openings in the bridging member24and hold the bridging member24and first or second flange14,16between the head portion of the first or second bone attachment member and the bone. Alternatively, the head portion of the first or second bone attachment member may abut the first or second flange14,16. A head portion of the third bone attachment member32abuts the third openings26in the bridging member24and secures the bridging member24, and hence the prosthetic assembly10, to the bone. In a further alternative, the bridging member may be secured to the first and second flanges by first and second securing members or means, for example screws, which pass through the fourth and fifth openings respectively. The first and second securing members may pass into the first and second openings respectively. The first and second securing members may not pass into the bone.

The bridging member24is provided with further securing structures or means40in the form of bores for securing a drill guide to the bridging member. The bores may be blind bores and may also be threaded.

With reference toFIG. 2a prosthetic assembly10according to a second embodiment of the invention comprises a mirror image of the bridging member24of the first embodiment such that the third opening26is angled in the opposite direction to that of the first embodiment. The second embodiment is otherwise substantially the same as the first embodiment. In this way, the first and second embodiments cater for both sides of the patient. Alternatively, the bridging member may receive a pivoting bone attachment member in the third opening and as such the same bridging member may be suitable for both sides of the patient. Accordingly, the third opening may be orientated such that an axis of the third opening may converge on the centreline of the body portion12.

With reference toFIGS. 3(a)-(b), the body portion12of the first and second embodiments of the present invention comprises one or more recessed regions42to receive an auxiliary bone engaging component. The auxiliary bone engaging component may comprise a face shaped to cooperate with the shape of the recessed regions42. The recessed regions42further comprise a bore44and a slot46. The bore44may be threaded to receive a screw for securing the auxiliary bone engaging component to the body portion12. The slot46may receive a cooperating protrusion on the auxiliary bone engaging component. The slot46and cooperating protrusion are obround shaped (i.e. a rectangular with semicircles at either end). The slot46and cooperating protrusion may be any other shape which assists in limiting rotation and movement of the auxiliary bone engaging component with respect to the body portion12.

The body portion12further comprises fins47disposed about the bone facing surface of the body portion. The fins47may be substantially oblong and may be substantially orientated in a plane containing the centreline of the body portion12.

With reference toFIGS. 3(c)-(e), the auxiliary bone engaging component comprises at least one of a compression screw48, an Iliac plate50, an Ischial blade52and an Obturator hook54. The auxiliary bone engaging component may further comprise a locking screw. The outside of the first and/or second flanges14and16may be tapered, and the Iliac plate50may comprise one or more corresponding tapered recesses to fit the first and/or second flanges.

An example of an Obturator hook154is shown inFIG. 3(e). The Obturator hook154comprises a protruding part155which is adapted to fit inside slot46. The Obturator hook154further comprises a first hole153for receiving a screw to secure the

Obturator hook into bore44of the prosthetic assembly10. The Obturator hook is shaped so as to curve back on itself like a fish hook and accordingly comprises a curved back portion151. The Obturator hook comprises a second hole152which is located on the curved back portion151and opposite the first hole153. The second hole152permits a tool to pass through the curved back portion so as to be able to access the screw which is received in the first hole153.

The Obturator hook154further comprises one or more gripping elements150on the curved back portion151which are adapted to grip the Obturator portion of the acetabulum. In particular, the gripping elements150may be in the form of a saw tooth arrangement, for example with a repeating right-angled triangular cross-section, which engages with the Obturator. The gripping elements150may comprise a ramped portion149, which protrudes from the curved back portion151, and a straight portion148, which returns to the curved back portion151and is substantially perpendicular to the curved back portion. A sharp point is formed at the join between the ramped and straight portions149,148. The ramped and straight portions149,148are orientated such that the ramped portion may ride over the Obturator bone portion during installation and that the sharp point defined at the join between the straight portion and ramped portion locks the Obturator hook154into place.

With reference toFIGS. 4(a)-(e), the prosthetic assembly10may further comprise an augment56. The augment56may connect to the body portion12by virtue of the first and second flanges14,16. As such the bridging member24may be in the form of the augment56and the bridging member24may comprise the third, fourth and fifth openings26,36,38as described above. In other words the bridging member24may be in the shape of a bubble augment. The augment56may comprise one or more further openings in addition to the third, fourth and fifth openings26,36,38, such that the augment may be attached to the body portion12in multiple positions about the circumference of the body portion. The augment56may further comprise first and second recess portions58,60for receiving the first and second flanges14,16respectively. The augment56may also comprise one or more of first, second and third bores62,63,64, which may be oblique to the third, fourth and fifth openings and may also intersect the third, fourth and fifth openings. The first, second and third bores62,63,64may each comprise an abutment shoulder such that the augment56may be secured to the body portion12by virtue of screws.

In an alternative arrangement shown inFIG. 4(d), an augment156may comprise a channel157intersecting the third, fourth and fifth openings126,136,138and the optional further openings135and139. With the optional further openings, the augment may be attached to the body portion in multiple positions about the circumference of the body portion. In a further alternative arrangement shown inFIG. 4(e), an augment256may comprise a channel257with one or more shoulders261,262which permit one or more adapters259to be slidably located within the channel. The adapters259comprise a threaded bore260for receiving threaded screws which also pass through the first and/or second openings20,22of the first and second flanges14,16. As the screw is tightened, the adapter259engages the one or more shoulders261,262and secures the augment156to the body portion12. The augment156may be secured to the body portion in a range of orientations by sliding the one or more adapters259to a desired position within the channel257.

The augment may be attached to the body portion12by virtue of one or more of the recessed regions42and the associated bore44and slot46. The augment may not form the bridging member24and may be in addition to the bridging member. As such, the auxiliary bone engaging component may comprise an augment. There may be a plurality of recessed regions42such that the augment may be attached to the body portion12in multiple positions about the circumference of the body portion and in a range of orientations.

As shown inFIGS. 4(b)-(c), the augment56is attached to the body portion12in such a way that it leaves a gap66between the augment56and the body portion12. The gap56allows for bone cement to penetrate between the augment and the body portion and provides a better fixation of the prosthetic assembly to the bone. The gap may be approximately 2 mm in width.

With reference toFIGS. 5(a)-(c) at least one of the first and second flanges may be provided with securing structures or means68in the form of bores for securing drill guides70to the first and/or second flange14,16. The securing structure68may also secure other instruments or bone attachment members to the first and/or second flange14,16. The bores may be blind bores and may also be threaded.FIG. 5(b) show the drill guides70secured to the first and second flanges14,16. The drill guides70may comprise openings (not shown) for receiving screws to secure the drill guides to the first and/or second flange. The drill guides70assist in guiding a drill into the bone so that a hole may be accurately drilled in a direction consistent with the orientation of the first and second openings20,22.

With reference toFIG. 6(a) a first angled drill guide72may be provided for engagement with the bridging member24of the first embodiment. Similarly, as shown inFIG. 6(b) a second angled drill guide74may be provided for engagement with the bridging member24of the second embodiment. The second angled drill guide74is a mirror image of the first angled drill guide72. As for the drill guides70, the angled drill guides70may comprise openings (not shown) for receiving screws to secure the drill guides to the securing structure40of the bridging member24. The angled drill guides72assist in guiding a drill into the bone so that a hole may be accurately drilled in a direction consistent with the orientation of the third opening26.

In terms of installation, the prosthetic assembly10may be implanted by first attaching the drill guides70to the first and second flanges14,16and drilling holes into the bone. The drill guides70may be pre-attached to the first and second flanges14,16. The drill guides70are then removed and the appropriate bridging member24(depending on left or right hand side of patient) is lined up with the first and second flanges14,16such that the first and second openings20,22line up with the fourth and fifth openings36,38respectively. The first and second bone attachment members28,30(e.g. bone screws) are screwed through the first/fourth and second/fifth openings respectively and into the bone, thereby securing the bridging member24to the body portion12and the prosthetic assembly10to the bone. The appropriate angled drill guide72,74is then secured to the bridging member24by virtue of the securing structure40and a third hole is drilled into the bone. Again, the angled drill guide72,74may be pre-attached to the bridging member24. Once the third hole has been drilled the angled drill guide is removed and the third bone attachment member32(e.g. bone screw) is screwed through the third opening26and into the bone.

In addition to the above, one or more of the aforementioned auxiliary bone engaging components may be attached to the body portion12prior to implantation of the prosthetic assembly10.

The present invention minimizes the parts inventory by providing a universal body portion12which can be used on the left or right hand side of the patient. The body portion12can be subsequently configured for either side of the patient by the addition of left or right hand sided bridging members24.

While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the present teachings. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein so that one of ordinary skill in the art would appreciate from the present teachings that features, elements and/or functions of one example can be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications can be made to adapt a particular situation or material to the present teachings without departing from the essential scope thereof. Therefore, it is intended that the present teachings not be limited to the particular examples illustrated by the drawings and described in the specification, but that the scope of the present teachings will include any embodiments falling within the foregoing description.