WO2012048362A1

WO2012048362A1 - Acetabular cup alignment guide

Info

Publication number: WO2012048362A1
Application number: PCT/AU2010/001725
Authority: WO
Inventors: Satish Shejale
Original assignee: Satish Shejale
Priority date: 2010-10-11
Filing date: 2010-12-22
Publication date: 2012-04-19

Abstract

An acetabular cup alignment guide and alignment apparatus is provided. The alignment guide (10) includes a guide body (11) configured to at least partially locate in or over an acetabulum of a patient, and a connection (12, 13) for connecting the guide body to an alignment member (20) such as to place the alignment member at a fixed orientation relative to the guide body. When the guide body is located at least partially in or over the acetabulum, the orientation of the alignment member is indicative of an alignment axis for implantation of an acetabular cup in the acetabulum during hip surgery. The orientation of the alignment axis can be captured by an alignment surface (313, 323) that can be brought into contact with the alignment member.

Description

"Acetabular Cup Alignment Guide"

Cross-Reference to Related Applications

The present application claims priority from Australian Provisional Patent Application No 2010904520 filed on 1 1 October 2010, and Australian Provisional Patent Application No 2010904884 filed on 2 November 2010, the contents of which are incorporated herein by reference.

Field

The present invention relates to an alignment guide and apparatus for use in hip surgery, such as total hip replacement surgery.

Background

Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant. The prosthetic implant can consist of different parts, including an acetabular cup designed to locate in the acetabulum (hip socket). To ensure that an acetabular cup functions correctly, and does not wear significantly or cause damage to a patient, it is important that the cup is positioned correctly in the acetabulum.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. Summary

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

According to a first aspect, the present invention provides an alignment guide configured to at least partially locate in or over the acetabulum of a patient and interact with an alignment means to place the alignment means at a desired orientation relative to the guide.

According to a second aspect, the present invention provides an acetabular cup alignment guide comprising: a guide body configured to at least partially locate in or over an acetabulum of a patient; and

a connection for connecting the guide body to an alignment member such as to place the alignment member at a fixed orientation relative to the guide body.

According to a third aspect, the present invention provides an acetabular cup alignment apparatus comprising:

an alignment guide according to the second aspect;

an alignment member connected to, or connectable to, the alignment guide by the connection at a fixed orientation relative to the guide body; and

an aligner configurable to capture the orientation of the alignment member.

According to a fourth aspect, the present invention provides a method of using the guide οτ apparatus of any one of the first to third aspects.

The alignment guide, and apparatus comprising the alignment guide, may be operable to determine, and capture, an alignment axis for an acetabular cup during hip surgery. The alignment member is preferably an elongate member such as a rod, tube or bar etc., although it may take other forms. The apparatus may be configured such that the alignment axis corresponds to the elongation direction of the alignment member and/or to a direction of extension of a surface of the alignment member, when the alignment member is connected to the alignment guide, and when the alignment guide is located at least partially in or over the acetabulum of the patient. The acetabulum may be a reamed acetabulum or an unreamed acetabulum. The alignment axis may be an axis along which it is desirable to insert, and/or orientate an axis of, an acetabular cup during hip surgery. For example, the alignment guide and apparatus may be used to determine and capture an alignment axis that has an angle of substantially 45 degrees inclination and 15 degrees anteversion from the centre of the reamed or unreamed acetabulum. Alternatively the alignment axis may correspond to other angles of inclination and anteversion from the centre of the acetabulum or from one or more other reference points of the acetabulum. In one embodiment, the alignment axis may be between 40 to 50 degrees inclination and 10 to 20 degrees anteversion from the centre of the reamed or unreamed acetabulum. In general, however, the guide and apparatus may be configured for any orientation of alignment axis.

The guide body may comprise one or more markers to align the body to one or more reference points of the acetabulum to ensure that the alignment guide is correctly located at the acetabulum. The guide body may comprise one or more lines as markers. For example, the guide body may comprise two perpendicular lines (when seen from above, for example). When the guide body is inserted into the correct position, one of the lines may be configured to extend from the superior pole to the inferior pole of the acetabulum, and the other of the lines may be configured to extend from the anterior pole to the posterior pole of the rim of the acetabulum. The lines may intersect at the centre of the guide body. Lines acting as markers may provide a grid-like pattern on the guide body. To aid insertion of the guide body, one or more reference points on the acetabulum may be marked by the surgeon. For example, the surgeon may mark the superior pole or the inferior margin of the acetabular notch (IMAN) or other landmarks of the acetabulum. Corresponding marks may be located on the guide body. Reference points of the acetabulum that may be marked include a superior alignment point indicative of the exact superior pole of the rim of the acetabulum at a landmark, the acetabular fovea or the superior margin of the rim of the acetabulum or the IMAN. The marks on the guide body or the acetabulum may be triangular marks or arrows, for example, which provide an indication of both a reference position and a direction.

In order to capture the orientation of the alignment member, the aligner may comprise an alignment surface which can be aligned with the alignment member and therefore the alignment axis, or which can be placed in a fixed orientation relative to the alignment member and alignment axis. For example, the alignment surface may be placeable in contact with an outer surface of the alignment member, e.g. an outer surface of an alignment rod, such as to orient the alignment surface along the elongation direction, or other direction of the alignment member. The alignment surface of the aligner may provide a guide surface for an acetabular cup inserter. The inserter may be a rod or an introducer handle, for example, which is connected to an acetabular cup, and which can rest against the alignment surface whilst it forces the acetabular cup into position at the acetabulum. The inserter may conform or fit snugly to the alignment surface. The alignment surface, or at least an element of the aligner comprising the alignment surface, may be changeable to conform or fit snugly to different types of introducer. The aligner, particularly the alignment surface of the aligner, may be configurable between a first state, where it is moveable relative to the patient and/or support surface on which the patient rests, and a second state, where it is fixed relative to the patient and or support surface.

As an alternative to having an alignment surface to physically capture the alignment axis, it is conceivable that the aligner may take other forms. For example, the aligner may comprise remote sensors to sense the orientation of the alignment member and it may capture the alignment in electronic form (e.g. in a computer memory). In this instance, the aligner may be configured to provide, for example, a visual or audible notification when an inserter is aligned in accordance with the sensed orientation of the alignment member.

The guide body may be configured to fit partially or entirely within the reamed or unreamed acetabulum, whereupon substantially all or part of its outer surface may be in contact with the surface of the acetabulum, which surface may include the lunate surface of the acetabulum, for example. The guide body may comprise a cup, e.g., a cup with a similar configuration to an acetabular cup. However, since the guide body need not perform the function of an acetabular cup, it may take other configurations. For example, it may comprise a solid body instead of a cup, or a plate or disc configured to extend across the acetabulum. As another alternative, the guide body may comprise a substantially dome-shaped portion, e.g. a hemispherical dome. The plate, disc or dome may extend at least partially in and/or over the reamed or unreamed acetabulum, between locations at or adjacent the rim of the acetabulum or otherwise. In general, a guide body having any shape may be utilised to the extent that the guide body can be placed at a fixed position relative to the acetabulum and can cooperate with the alignment member, e.g. alignment rod, to place the alignment member at an appropriate angle relative to the acetabulum.

A plurality of different guide bodies, each having different shapes and/or sizes may be provided, e.g., as part of a kit, so that an appropriate guide body can be selected dependent on the patient. For example, a smaller guide body may be selected for a child patient than for an adult patient. The plurality of guide bodies may be a plurality of e.g., hemispherical cups, having outer diameters sizes varying from 44 mm to 64mm, with progressive increments of 0.5mm, 1mm or 2mm, for example.

The connection may be integral with the guide body, or may be a connector that is itself connected to the guide body, for example. The connection may comprise an orifice for receiving a part of the alignment member, e.g., an end region of the alignment member, in order to releasably connect to the alignment member in a manner that places the alignment member in the desired orientation relative to the guide body. The orifice may take any shape or size in order to conform to the size and shape of the alignment member. Alternatively, the connection may comprise a rod-like projection, for example, that is configured to be inserted into an orifice in the alignment member. Other types of connection arrangement are conceivable. For example, the alignment member can be permanently connected to the guide body via the connection.

The connection may comprise a tube, e.g., a cylindrical tube. The tube may project from a wall of the guide body, such as an inner wall of the guide body.

Alternatively, the connection may comprise a bore in a wall of the guide body, such as a cylindrical bore. The bore may have an opening at a surface of a wall of the guide body. The tube or bore may be arranged to receive at least a portion of the alignment member with conforming shape, such as a cylindrical portion of the alignment member. The alignment member may be a straight elongate member, e.g. a straight rod.

Alternatively, the alignment member may be bent, e.g., bent twice, to avoid or navigate an obstacle such as the rim of the acetabulum, for example. The alignment member may be partially or entirely cylindrical. The alignment member may be a one-piece element or otherwise. In general, the alignment member may have any shape or configuration as long as it comprises a portion, e.g., a surface, that can extend at a fixed orientation relative to the guide body.

Two of the connections may be provided so that a single alignment guide may be used for the right hip or the left hip. Each connection may be substantially identical except for the orientation at which they are configured to position the alignment member relative to the guide. When the connections are provided by tubes or projections, they may be arranged in a "V"-shape at a centre of the guide body, for example. Alternatively, left and right markers may be provided at two different positions of the guide body respectively, which markers may be lined up with respective landmarks of the left and right acetabulum in order to locate the alignment member, when connected to the guide body, at the desired orientation relative to the left and right acetabulum.

The alignment guide and alignment apparatus may be formed of a variety of different materials, such as compressed plastics or surgical steel, which materials may be sterilized so that the guide and apparatus may be re-used. Brief Description of the Drawings

Examples of the invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic side view of an acetabular cup alignment apparatus according to an embodiment of the present invention;

Figs. 2a and 2b show top views of the alignment guide of the apparatus of Fig. i ;

Figs. 3a and 3b show oblique top views of the alignment guide of the apparatus of Fig. 1 ;

Figs. 4a and 4b show side views of an alignment guide according to another embodiment of the present invention; Figs. 5a and 5b show further side views of the alignment guide of Figs. 4a and

4b

Fig. 6 shows a top view of the alignment guide of Figs. 4a and 4b;

Fig. 7 shows a bottom oblique view of the alignment guide of Figs 4a and 4b; Fig. 8 shows a side view of an alignment guide according to another embodiment of the present invention;

Figs. 9a to 9c show schematic cross-sectional drawings of the alignment guides of Figs. 1 , 8 and 4a, respectively, in position at an acetabulum;

Figs. 10a and 10b show a top oblique view and a bottom oblique view, respectively, of an alignment guide according to another embodiment of the present invention;

Fig. 11 shows an oblique side view of acetabular cup alignment apparatus according to another embodiment of the present invention connected to a pelvis of a patient;

Figs. 12a and 12b show side views of alternative cross bar members that may be used in the apparatus of Fig. 11 ;

Figs. 13a and 13b show side views of alternative rod seats that may be used in the apparatus of Fig. i l ;

Fig 14 shows a side view of an alternative riser member that may be used in the apparatus of Fig. i l ;

Figs. 15a to 15c show side views of alternative stanchions that may be used in the apparatus of Fig. 1 1 ;

Fig. 16 shows a side cross-sectional view of an alignment guide according to another embodiment of the present invention;

Fig. 17 shows a side cross-sectional view of an alignment guide according to another embodiment of the present invention;

Fig. 18 shows a side cross-sectional view of an alignment guide according to another embodiment of the present invention; and

Fig. 19 shows a top view of an alignment guide according to another

embodiment of the present invention.

Detailed Description

An embodiment of an acetabular cup alignment apparatus is shown in Fig. 1. The apparatus comprises an alignment guide 10, an alignment rod 20 and an aligner 30. The alignment guide 10, also shown in Figs. 2a to 3b, comprises a hemispherical cup-shaped body 1 1 designed to locate in a patient's acetabulum (acetabular socket), and two alignment tubes 12, 13 projecting in a "V"-configuration from a central point of an inner curved surface of the body 1 1. The alignment tubes 12, 13 provide means for connecting the alignment rod 20 to the alignment guide 10 in a fixed orientation relative to the guide 10. Two alignment tubes 12, 13 are provided in this embodiment so that the alignment guide 10 can be used for both left and right hip surgery. In alternative embodiments, a hemispherical solid body may be used instead of a cup, and the tubes may be replaced by conduits extending through the solid body at the same orientation as the tubes.

The alignment rod 20 is provided as an alignment member. The alignment rod is substantially straight and comprises a cylindrical main body portion 21 and a ^" cylindrical connection portion 22 projecting from one end of the main body portion 21. The connection portion 22 has a smaller diameter than the main portion 21 , and the outer surfaces of the connection portion 22 are shaped to conform to the interior surfaces of the alignment tubes 12, 13, which also have a cylindrical form, so that the connection portion 22 can be inserted into the alignment tubes 12, 13 or vice versa, in a manner that releasably connects the rod 20 to the guide 10. A secure releasable connection is achieved in this embodiment through frictional engagement. However, in alternative embodiments, fixations means such as a screw or clip may be used. A releasable connection allows the rod to be inserted into each of the alignment tubes 12, 13, dependent on whether the left or right hip is undergoing surgery, and for the same rod to be used in alignment guides of different sizes, for example. However, it is conceivable that the rod may be permanently connected to an alignment guide in alternative embodiments or only one alignment tube may be provided, in which case the alignment guide may be configured for use with only one of the left and right hips, for example.

In Fig. 1 , the alignment rod 20 is shown releasably connected to the right alignment tube 12. The elongation direction of the right alignment tube 12, and therefore the connected rod 20, has an angle of 45 degrees inclination and 15 degrees anterversion from the centre of a reamed right acetabulum, when the guide 10 is located snugly therein. The elongation direction of the left alignment tube 13 is configured in a corresponding manner, but for a reamed left acetabulum.

As indicated, in this embodiment, the alignment tubes 12, 13 are configured to be orientated at 45 degree inclination and 15 degrees anteversion from the centre of the respective acetabulum, which orientation is conferred to at least a portion of the alignment member and corresponds to a commonly desired alignment axis for an acetabular cup in hip surgery. However, different orientations may be provided as desired. For example, different orientations in the range of between 40 to 50 degrees inclination and 10 to 20 degrees anteversion from the centre of a reamed or unreamed acetabulum may be provided for the connections, connectors and alignment members of the present or alternative embodiments. Although the guide body of this

embodiment is configured to locate in a reamed acetabulum, in alternative

embodiments described herein or otherwise, the guide body may be configured to locate in an unreamed acetabulum.

In this embodiment, the aligner 30 comprises first and second receptor arm assemblies 31 , 32. The first assembly 31 is arranged to be fixed at a bottom end 31 1 to the interior acetabular rim or margin of the patient, using a bone screw 312. In Fig. 1 , for simplicity the bottom end 31 1. is shown extending vertically; however, in practice, it may be configured to extend at an angle to the vertical to ensure that it can fix to the acetabular rim or margin. The second assembly 32 is arranged to be fixed at a bottom end 321 to a support surface e.g., to the side, or the draped metal side bar, of an operating table on which the patient may be lying, using a clamp 322.

At the top end of each assembly 31 , 32, a rod seat 313, 323 is provided. In this embodiment, each rod seat 313, 323 takes the form of a curved channel having a substantially semi-circular cross section.

The arm assemblies 31, 32 are designed so that the position and orientation of the rod seats 313, 323 relative to the patient and support surface is adjustable.

Adjustability is achieved at least partially through the provision, in each assembly in this embodiment, of two arms 314, 315, 324, 325. A bottom arm 314, 324 is fixed to the patient support surface, and a top arm 315, 325 is fixed to the rod seat 313, 323^' The bottom and top arms of each assembly 31, 32 are relatively rotatable about, and adjustable in length relative to, a joint member 316, 326. Furthermore, the orientation of each rod seat 313, 323 relative to the top arm 324, 325 is adjustable. The adjustability of the various components of the arm assemblies 31, 32 allows the - positioning and orientation of the rod seats 313, 323 to be adjusted precisely in three- dimensions. However, screw fixing mechanisms between the top arms 324, 325 and the rod seats 313, 323, and screw fixing mechanisms at the joint members 316, 326, are operable to fix the various components of the arm assemblies, and therefore the rod seats 313, 323, in position when desired.

In use, a plurality of alignment guides 10 of different sizes, e.g., of diameters from 44mm to 64mm size, in increments of 0.5mm, 1mm or 2mm, may be provided. Accordingly, a guide of an appropriate size may be selected depending on the patient undergoing hip surgery. Once the appropriate alignment guide 10 is selected, it is placed, prior to, or after, the rod 20 is connected to the guide 10, in a reamed acetabulum so that a snug fit in the socket is achieved and a superior triangular mark 14 on the guide body 11 is aligned to a fixed superior alignment mark, which alignment mark is to be created by the surgeon on the reamed acetabulum to indicate the superior pole of the acetabulum.

Once the guide 10 is inserted in the acetabulum, with the alignment rod 20 connected thereto, the alignment rod 20 can protrude out of the acetabulum along the alignment axis (e.g., 45 degrees inclination and 15 degrees anteversion in this embodiment). This orientation of the alignment rod 20 can be captured by the aligner 30. To achieve this, the arm assemblies 31 , 32 are manipulated to bring the inner curved surfaces of the rod seats 313, 323 into contact with the main body 21 of the alignment rod 20, seating the rod 20 on the two rod seats 313, 323. The rods seats are then fixed in position, which in turn fixes the direction of extension of the inner curved surfaces of the rod seats 323, 313 along the alignment axis. Since one rod seat 313 will be fixed to the patient, and the other rod seat^'323 fixed to the support surface, any slight movement of the patient relative to the support surface, due to environmental factors, etc., will not significantly affect the relative positioning and orientation of the rod seats and the alignment axis. Nonetheless, it is conceivable that, in alternative embodiments, the apparatus may comprise only one of the two arm assemblies 31 , 32.

After the rod seat positions are fixed, the alignment guide 10 and alignment rod 20 can be removed and an inserter, e.g., an insertion rod or introducer handle, can be seated on the rod seats 313, 323. In doing so, the inserter can be aligned with the alignment axis. The inserter can be connected to an acetabular cup and therefore, as the acetabular cup is forced into position by the inserter, the inserter, while resting against the rod seats, can remain aligned with alignment axis, leading to correct positioning of the cup in the acetabulum.

An alignment guide 100, according to another embodiment of the invention, is shown in Figs. 4a to 7. The guide comprises a circular disc 101 and a central rod 102 that extends through the centre of the disc 101 , substantially perpendicular to the plane of the disc 101. Like the embodiment of Fig. 1, two alignment tubes 103, 104 are ^' provided to connect the guide 100 to a connection rod. The alignment tubes 103, 104 project in a V-shaped configuration from the bottom end of the central rod 102. The guide 100 may be used with an alignment rod and an aligner that are the same or similar to the alignment rod 20 and the aligner 30 described with respect to the embodiment of Fig. 1, and the function of the guide 100, and its interaction with the alignment rod and aligner, may be substantially the same as described with respect to the embodiment of Fig. 1. A plurality of the guides 100 having discs with diameters ranging from 44mm to 64 mm, in 0.5mm, 1mm or 2mm increments, may be provided, so that a guide of an appropriate size may be selected depending on the patient undergoing surgery.

An alignment guide 1 10, according to yet another embodiment of the invention, is shown in Fig. 8. The guide comprises a substantially hemispherical dome 1 1 1 and a central rod 1 12 that extends through the centre of the dome 1 1 1. Like previous embodiments, two alignment tubes 1 13, 114 are provided to connect the guide 1 10 to a connection rod. The alignment tubes 1 13, 1 14 project in a V-shaped configuration from the bottom end of the central rod 112 up to the dome, top end openings 1 13a of each tube being contiguous with the dome's outer surface. The guide 1 10 may be used with an alignment rod and an aligner that are the same or similar to the alignment rod 20 and the aligner 30 described with respect to the embodiment of Fig. I , and the function of the guide 1 10, and its interaction with the alignment rod and aligner, may be substantially the same as described with respect to the embodiment of Fig. 1. A plurality of the guides 1 10 having domes with diameters ranging from 44mm to 64 mm, in 0.5mm, 1mm or 2mm increments, may be provided, so that a guide of an appropriate size may be selected depending on the patient undergoing surgery.

Figs. 9a to 9c show schematic cross-sectional drawings of alignment guides of the previous embodiments 10, 110, 100 in position at the acetabulum. With reference to Fig. 9a, the cup-shaped body 1 1 of the alignment guide 10 is configured to locate entirely within the acetabulum 4 whereupon substantially the entire outer surface of the cup-shaped body 1 1 contacts the surface of the acetabulum. With reference to Fig. 9b, the dome-shaped body 1 1 1 of the alignment 1 10 guide is configured to partially locate within the acetabulum 4, substantially at its rim. The rim of the body 1 1 1 contacts the acetabulum adjacent the acetabular rim, and the guide body 111 extends in an arc over the acetabulum. With reference to Fig. 9c, the disc-shaped body 101 of the alignment guide 100 contacts the acetabulum at substantially the same position as the dome- shaped alignment body 1 1 1 , but extends directly across the acetabulum between the contact points.

An alignment guide 120, according to yet another embodiment of the invention, is shown in Figs. 10a and 10b. The guide 120 comprises a substantially hemispherical solid body 121 , the body comprising two bores 122, 123 that extend from respective top openings that are separated along the rim 124 of the body 121 , and a common opening 125 at the centre of the hemispherical bottom surface 126 of the body 121. The two bores are arranged to receive a portion of an alignment member such as an alignment rod to connect the alignment member to the guide body 121. The bores 122, 123 extend in a V-shaped configuration within the body. The guide 120 may be used with an alignment rod and an aligner that are the same or similar to the alignment rod 20 and the aligner 30 described with respect to the embodiment of Fig. 1 , and the function of the guide 120, and its interaction with the alignment rod and aligner, may be substantially the same as described with respect to the embodiment of Fig. 1.

However, the solid nature of the body 121 may contribute to the guide 120 having a greater weight than the guide bodies of the previous embodiments, at least when formed of the same or similar material, e.g. surgical steel or compressed plastics material, for example. By having a greater weight, the guide body may locate in the acetabulum more securely. Furthermore, the solid nature of the guide body 121 may lead to the guide 120 being more robust.

A plurality of the guides 120 having hemispherical bodies with diameters ranging from 44mm to 64mm, in 0.5mm, 1mm or 2mm increments, may be provided, so that a guide of an appropriate size may be selected depending on the patient undergoing surgery.

An aligner 40 according to another embodiment of the present invention, for use with the alignment guide 120 or other alignment guides described herein, is shown in Fig. 1 1. The aligner 40 includes a stanchion 41, a riser member 42, a cross-bar 43 and a rod seat 44. The stanchion 41 has a foot plate 410 at its bottom end configured to abut against the pelvic girdle of a patient. A bone screw 41 1 is provided to extend through a hole in the foot plate 410 and fix the foot plate 410 to the pelvic girdle. In particular, in this embodiment, the foot plate 410 is configured to be fixed to the body or surface of the ischium bone, immediately outside of the acetabular rim or margin 5. The bone screw may 411 be of a design, size, thickness and/or length, etc., that is commonly used in orthopaedics surgery. However, the length of the screw is preferably such that it does not protrude underneath the ischium bone when the foot plate 410 is firmly attached thereto. This prevents any possible damage to internal structures underneath the ischium bone.

The riser member 42 comprises a first hole at one end to receive the stanchion 41 in order to slidably connect the riser member to the stanchion 41 , such that the riser member 42 can translate along the stanchion 41 towards and away from the pelvis or ischium bone and rotate relative to the stanchion 41 about its connection with the stanchion 41. Once a desired position has been reached, the riser member 42 can be fixed in position relative to the stanchion 41 via a fixing screw 421.

At the opposite end of the riser member 42 a second hole is provided, to receive one end of a cross-bar 43 in order to slidably connect the cross-bar 43 to the riser member 42. The rod seat 44 is mounted adjacent one end of the cross bar and is configured to receive an alignment rod 20. Through the slidable connection between cross bar 43 and the riser member 42, the rod seat 44 can move towards and away from the riser member 42. Furthermore, through the same connection between the riser member 42 and the cross bar 43, the cross bar, and thus the rod seat 44, can be rotated about the longitudinal axis of the cross bar 43. Once a desired position for the cross bar • 43 relative to the riser member 42 has been reached, the cross bar 43 can be fixed in position relative to the riser member 42 via a fixing screw 422.

Referring additionally to Fig. 12a, the rod seat 44 is mounted adjacent one end of the cross bar 43 by means of a threaded rod 441 extending from the rear of the rod seat 44, through a hole in the cross bar 43. The rod seat 44 is rotatable relative to the cross bar 43 about the longitudinal axis of the threaded rod 441. Once a desired position for the rod seat 44 relative to the cross bar 43 has been reached, the rod seat 44 can be fixed in position relative to the cross bar 43 via a wing nut 442 connected to the threaded rod 441.

In general, as a result of the connections between the stanchion 41 , riser member

42, cross bar 43 and rod seat 44 as discussed, the rod seat 44 can be moved to any desired position/orientation (subject to the dimensions of the apparatus) in order to bring the rod seat 44 into appropriate alignment with the alignment rod. Once this alignment has been reached, the rod seat 44 can be easily fixed in position through tightening of the screws 421 , 422 and the wing nut 442.

The aligner 40 may be modified in various different ways. The cross bar 43 may not be a straight bar, for example. Referring to Fig. 12b, a cross bar 43a that is bent may be used, which may allow the rod seat 44 to take up a different position relative to the riser member 42, than it would in combination with a straight cross bar 43 as shown in Fig. 12a.

As another example, the rod seat 44 may not be a substantially U-shaped , member as shown in Fig. 11. For example, referring to Fig. 13a, a rod seat 443 may comprise a hollow tube or annular member 444, which may surround a portion of the alignment rod. The inner surfaces of the hollow tube or annular member 444 may align with the outer surfaces of the alignment rod and thus the alignment axis, for example. Referring to Fig. 13b, as another alternative, a rod seat 445 may comprise two substantially semi-circular elements 446, at least one of which is mounted to a modified cross bar 43b. The semi-circular elements 446 may be^translatable towards each other by virtue of a screw arrangement 447, in order to clamp the elements 446 to the outer surfaces of the alignment rod. As yet another example, the riser member may not be box-shaped, as shown in Fig. 1 1. For example, referring to Fig. 14, the riser member 42a may have rounded ends.

As another example, the foot plate 410 of the stanchion 41 as shown in Fig. 11 may be modified or replaced. For example, referring to Fig. 15a, a curved foot plate 412 with two opposing foot-like elements may be provided, each with a hole for receiving a respective screw 413 to achieve more secure fixing of the stanchion 41 to the patient. Referring to Fig. 15b, the foot plate may be replaced with a horizontal clamping member with two opposed gripping elements 414, the gripping elements 414 moveable towards each other by virtue of a screw mechanism 415 to grip a portion of the patient, or a portion of an operating table (e.g. side bar) on which the patient is lying. Referring to Fig. 15c, the foot plate may also be replaced with a vertical clamping member with upper and lower gripping elements 416, 417, the gripping elements 416, 417 being moveable towards each other by virtue of a screw mechanism 418 to grip a portion of the patient or a portion of an operating table (e.g. side bar) on which the patient is lying.

Further embodiments of an alignment guide according to the present invention are shown in Figs 16 to 19. In the embodiment shown in Fig. 16, an alignment guide 130 is provided that includes an alignment member 131 that is permanently fixed and integral to a guide body 132. In the embodiment shown in Fig. 17, an alignment guide 140 includes a connector element 141 projecting from the guide body 142, which connector element 141 is arranged to be received in a recess 143 in the alignment member 1 4 in order to connect the alignment member 144 to the guide body. Two connector elements 141 can be provided to connect to the alignment member 144 at different positions and orientations relative to the guide body in order to perform left and right hip surgery. In the embodiment shown in Fig. 18, a relatively thick alignment member 151 is provided, which has a substantially uniform cross-section along its length and which is permanently fixed and integral to the guide body 152.

In the embodiment shown in Fig. 19, an alignment guide 160 includes a guide body with two relatively rotatable sections. The two sections include an inner section 161 and an outer section 162, which sections 161 , 162 form a guide body. To connect an alignment rod to the guide body, one of its ends is located through a hole 163 at a rim of the outer section 162 and into a central hole or receiving portion (not shown) provided in or on the inner section 161 at a centre of the guide body. By relatively rotating the inner and outer sections 161 , 162, the alignment rod, when connected, can be rotated about the centre point. In this embodiment, the guide body, when located in the acetabulum, is configured so that the alignment rod is always disposed at substantially 45 degrees inclination from the centre of the acetabulum (although other angles in the range of 40 to 50 degrees inclination or otherwise may be used).

However, by relatively rotating the two sections 161 , 162, the angle of anteversion can be changed (from 0 degrees to 30 degrees either side of a centre line 163 in this embodiment). Thus the angle of anteversion at which the guide body will place the alignment member when located in the acetabulum can be chosen depending on whether left or right hip surgery is taking place, or other surgical factors. Angle markers 164 are provided to indicate the selected angle of anteversion. Additional markers 165 are provided to indicate the direction of relative rotation appropriate to move the guide between configurations for left and right hip surgery. A ratchet mechanism may be included to ensure that the selected angle can remain substantially fixed, unless a reasonable force is applied to relatively rotate the two sections 161, 162.

As an alternative to providing to two connections or relatively rotatable sections, to allow use of the guide body in both left and right hip surgery, as described in previous embodiments, in alternative embodiments, left and right markers may be provided at two different positions of the guide body respectively, which markers may be lined up with respective landmarks of the left and right acetabulum in order to locate the alignment member, when connected to the guide body, at the desired orientation relative to the left and right acetabulum.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. An acetabular cup alignment guide comprising:

a guide body configured to at least partially locate in or. over an acetabulum of a patient; and

2. The guide of claim 1 , wherein, when the guide body is located at least partially in or over the acetabulum, the fixed orientation of the alignment member is indicative of an alignment axis for implantation of an acetabular cup in the acetabulum during hip surgery.

3. The guide of claim 2, wherein the alignment axis is an axis along which it is desirable to insert an acetabular cup into the acetabulum during hip replacement surgery.

4. The guide of claim 2 or 3, wherein the alignment axis extends at an angle of about 40 to 50 degrees inclination from the centre of the acetabulum.

5. The guide of claim 4, wherein the alignment axis extends at an angle of about 45 degrees inclination from the centre of the acetabulum.

6. The guide of claim 4 or 5, wherein the alignment axis extends at an angle of 0 to 30 degrees anterversion from the centre of the acetabulum.

7. The guide of claim 6, wherein the alignment axis extends at an angle of about 10 to 20 degrees anterversion from the centre of the acetabulum.

8. The guide of claim 7, wherein the alignment axis extends at an angle of about 15 degrees anteversion from the centre of the acetabulum.

9. The guide of any one of claims 2 to 8, wherein the alignment member is an elongate member and wherein, at the fixed orientation relative to the guide body, the alignment member has its axis of elongation parallel to the alignment axis.

10. The guide of any one of claims 2 to 9, wherein, at the fixed orientation relative to the guide body, the alignment member comprises a surface that is parallel to the alignment axis.

11. The guide of claim 10, wherein the alignment member is a rod and the alignment surface is an outer surface of the rod.

12. The guide of any one of the preceding claims, wherein the connection comprises an orifice for receiving at least a portion of the alignment member to connect the alignment member to the guide body and place the alignment member at the fixed orientation.

13. The guide of any one of claims 1 to 1 1 , wherein the connection comprises a projection and the alignment member comprises an orifice for receiving at least a portion of the projection to connect the alignment member to the guide body and place the alignment member at the fixed orientation.

14. The guide of any one of any one of the preceding claims, wherein connection is configured to removably connect the alignment member to the guide body.

15. The guide of claim 14, wherein the guide comprises two of the connections, the two connections for interchangeably placing the alignment member at two different fixed orientations relative to the guide body, for use in left and right hip surgery, respectively.

16. The guide of any one of claims 1 to 1 1 , wherein the connection permanently connects the alignment member to the guide body.

17. The guide of claim 16, wherein the guide body, connection and alignment member are integrally formed.

18. The guide of any one of the preceding claims, wherein the guide body is a substantially hemispherical body or cup and is configured to locate at least partially in the acetabulum.

19. The guide of any one of claims 1 to 17, wherein the guide body is a plate configured to locate at least partially in and/or extend across the acetabulum.

20. The guide of any one of claims 1 to 17, wherein the guide body is a dome configured to locate at least partially over the acetabulum.

21. The guide of any one of the preceding claims, wherein the guide body comprises two relatively rotatable sections operable to alter the orientation of the alignment member relative to a portion of the guide body.

22. The guide of any one of the preceding claims comprising one or more markers to align the guide body to one or more reference points of the acetabulum.

23. An acetabular cup alignment guide kit, comprising a plurality of the acetabular cup alignment guides according to any one of the preceding claims, wherein the guide bodies of the guides have different diameters.

24. The kit of claim 23, wherein the diameters are between about 44mm to about 64mm.

25. The kit of claim 23, wherein the guides are two or more guides selected from a group of guides with guide bodies having respective diameters of from 44mm to

64mm in 0.5 mm increments.

26. Acetabular cup alignment apparatus comprising;

an alignment guide according to any one of claims 1 to 22;

an aligner configurable to capture the orientation of the alignment member.

27. The apparatus of claim 26, wherein the aligner is configured to be connected to the patient.

28. The apparatus of claim 27, wherein the aligner is configured to be connected at or adjacent the interior acetabular rim or margin of the patient.

29. The apparatus of claim 28, wherein the aligner is configured to be connected to the ischium bone.

30. The apparatus of any one of claims 26 to 29, wherein the aligner is configured to be connected to a surface on which the patient is lying during surgery.

31. The apparatus of any one of claims 26 to 30, wherein the aligner

' comprises an alignment surface alignable with at least a portion of the alignment member to capture the orientation of the alignment member.

32. The apparatus of claim 31 , wherein the aligner is configurable between a first state, in which the alignment surface is moveable relative to the patient, and a second state, in which the alignment surface is fixed relative to the patient.

33. The apparatus of claim 32, wherein, when the alignment surface is fixed relative to the patient, the alignment surface is configured to provide a guide surface for an inserter during insertion of an acetabular cup at the patient's acetabulum in hip replacement surgery.

34. The apparatus of claim 33, wherein the inserter is an insertion rod or introducer handle connected to the acetabular cup.