Field of the Invention

The present invention relates to a hip joint prosthesis, with associated cohesive means in accordance with the claims.

Background of the Invention and Prior Art

At present, a large number of hip joint operations are performed in Sweden, of which 11.9 % (2016) have to be redone (reoperated). In these hip joint surgeries, the existing hip joint is replaced by an artificial hip joint. The main reason for replacing a hip joint with an artificial hip joint is osteoarthritis or some other type of degenerative joint disease. The replacement of the existing hip joint with a hip joint prosthesis may also be caused by congenital defects in the hip joint or complications following femoral neck fractures.

With reference to Figure 1 A, a hip joint 30 is shown in principle prior to surgery. The hip joint 30 consists of a femur head 31, which is articulated in the acetabulum 32 in the pelvic bone 33. The acetabulum 32 is a part of the pelvic bone 33. The femur head 31 connects via the femoral neck 34 to the femur (femur) 35. The hip joint also includes a ligament that holds the ball joint and the joint cavity. The ligament prevents the parts of the hip from separating.

Figure IB shows in principle an artificial hip joint (hip joint prosthesis) 1 consisting of a femoral component (joint head) 2 and joint cavity (cup, capsule) 3 implanted in a human. The femoral component (joint head), which is usually made of metal is connected with cement, or some other suitable method for the femur. The joint cavity 3 is usually connected to the pelvic bone by screwing or cementing it.

One problem with surgical hip replacement is that the joint head can be dislocated (luxated) from the joint after it is implanted. The luxation causes the patient to be immobilized.

Luxations are usually painful and uncomfortable, partly because the joint head after dislocation damages (crushes) muscle tissue, which results in a long rehabilitation time. In order to restore the hip joint after a luxation, medical care is required and sometimes a hip surgery must be performed with associated costs. The risk of luxation increases substantially after reoperation, that is, after a new hip joint surgery is performed. The fact that the risk of luxation increases after a reoperation is particularly problematic given that the patients in whom reoperation becomes relevant usually have a high age. This high age means that the patient usually recovers more slowly after the operation and that the patient does not uncommonly have other illnesses, which impairs the patient’s ability to recover after the operation.

A number of methods and devices for preventing the luxation of artificial hip joints are already known. It is thus known to retain the joint head in the joint cavity (cup) by adding material to the edge of the joint cavity (cup) after the ball-shaped part of the joint head is inserted into the joint cavity. The procedure causes the hip joint operation to take a longer time, which in turn increases the risk of infections in connection with the procedure.

A number of patented devices and methods have been developed over the years to reduce the problems of luxation of hip joints. For example, US5951605 discloses a method and apparatus for reducing the risk of luxation of a hip joint. The hip joint prosthesis according to the patent comprises an elongated holding member which holds together the femoral part of the hip joint and the joint cavity. Therefore, the design differs substantially from the design of the present patent application.

In US37233995 a variant of a hip joint prosthesis is described. The design includes a joint cavity and a femur component which are held together by a locking device. The locking device differs substantially from the design of the present patent application.

US7780739 discloses a variant of a hip joint prosthesis. The design comprises a joint cavity which consists of a first part and a second part which are locked together with a locking ring. The design differs substantially from the design in accordance with the present patent application.

In US3683421 a variant of a hip joint design for prostheses and the like is described. The design comprises a ball joint with a joint cavity and a femur component with a ball-shaped part. The ball-shaped part is prevented from being dislocated from the joint cavity by means of a locking device. The locking device partially encloses the ball-shaped part. The design is otherwise substantially different from the design in accordance with the present patent application.

Interational Patent Application W02004063107 discloses a number of variants of nitride glass. Its description does not describe applications for the material such as in a joint cavity and a cohesive means. Brief Description of the Figures

In the following detailed description of the present invention, references and references to the following figures will be made. These figures are briefly described in the following figure list. The hip joint prostheses shown in the figures constitute exemplifying embodiments of the hip joint prosthesis in accordance with the present patent application. The exemplifying embodiments of the hip joint prosthesis does not limit the scope of protection of the present patent application. Note that the figures are schematic and that details may have been omitted in the figures.

Figure 1 A schematically shows a hip joint before surgery.

Figure 1B schematically shows a hip joint after surgery.

Figure 2 schematically shows a cross-section of a hip joint prosthesis in accordance with a first embodiment.

Figures 3A and 3B show a first embodiment of the cohesive means.

Figure 4A shows the joint cavity in perspective.

Figures 4B and 4C show two additional views of the joint cavity.

Figure 5A shows an alternative embodiment of the cohesive means seen externally in perspective.

Figure 5B shows an alternate embodiment of the cohesive means from an external view.

Figure 5C shows an alternative embodiment of the cohesive means from internal view.

Detailed Description of the Invention

With reference to the figures, a hip joint prosthesis 1 is shown which comprises a femoral component (thigh-bone component) 2 which is connected to a joint cavity 3 (cup). The present invention also includes at least one locking member (cohesive means) 4 which in use holds the femoral component 2 and the joint cavity 3 together.

The femoral component 2 is preferably of a shape and size (shapes and sizes) which is typical in the field of hip prostheses. The femoral component 2 comprises in the illustrated embodiment a ball portion 5, a neck portion 6 and a shaft portion (stem portion) 7. The ball portion 5 comprises a joint surface 8 which is preferably in the form of a partial sphere or a half sphere. In alternative embodiments, the joint surface may be of another shape suitable for the purpose. The ball portion 5 is attached to or formed integrally with the neck portion 6. The neck portion 6 is, in turn, attached to or formed by a shaft portion 7 included in the femoral component 2. Preferably, the femoral component 2 is made in one piece. In alternative embodiments, the femoral component may be of a different shape from that shown in the figures and/or consist of two or more parts.

The joint cavity 3 can also, for its basic design, consist of some type of joint cavity 3

(articulated capsule, cup) or the like. The joint cavity 3 includes a hollow 9 (shown in Figure 4A) which is interally spherical (part of a sphere). However, this does not rule out that the joint cavity 3 has a partially different shape suitable for the purpose. Specifically with the present invention, it comprises at least one locking member 4 with which the ball portion 5 is positioned relative to the joint cavity 3, which prevents the ball portion 5 of the femoral component 2 from being involuntarily dislocated from the joint cavity 3.

Referring to Figures 3A and 3B, an exemplifying first embodiment of the present cohesive means (locking member) 4 is shown. In the exemplifying embodiment the locking member consists of (or is comprised of) a collar 10 (disc-shaped design, alternatively a lip edge) with a through hole 11, recess bushing or similar. The material of the collar 10 encloses parts of the perimeter of the hole 11 in the radial, or substantially radial, direction of the hole. In the preferred embodiment, the collar encloses a portion of the perimeter of the hole 11 whereby an opening 12 is formed in the material around the hole 11. In the exemplifying embodiment, the opening 12 has a width 11 which is slightly wider than the maximum width of the neck of the femoral component. However, the width of the opening 12 has a width smaller than the diameter of the ball portion 5 of the femoral component 2.

The collar 10 comprises an inside 13 and an outside 14. By the inside 13 is meant the side of the collar 10 which is connected to the joint cavity 3. By the outside 14 is meant the opposite side to the inside of the collar 10.

The collar 10 further comprises at least one inner edge 15 located closer to the center in the radial direction than the outer edge 16 which is located further from the center in the radial direction.

In the first embodiment, the outer edge 16 of the collar 10 comprises at least one first segment (portion, section) 17 in the radial direction of the locking member 4 which, when held together by the locking member and joint cavity, is extended further in radial direction than the radial extent of the joint cavity. In the embodiment of the locking member 4 shown in the figures, its outer edge comprises at least one first segment 17, at least one second segment 18 and at least one third segment 19, which when the locking member 4 and the joint cavity 3 are connected extend further in the radial direction than the radial of the joint cavity 3. In alternative embodiments, the locking member 4 may comprise more or fewer segments than three.

In the embodiment of Figures 3A and 3B, the protruding segments each comprise at least one hole extending in the axial direction of the locking member. In the exemplifying embodiment, the locking member comprises at least one first hole, outer hole 20, and a second hole, inner hole 21. The first hole 20 has a greater radial distance from the axial center of the locking member 4 than the second hole 21, the inner hole. In alterative embodiments, the locking member may lack one or more inner holes 21.

The collar 10 comprises at least one recess (cutout) 22 of the inner edge 15 of the collar’s inside 13, in the direction of the ball portion 5 when the collar 10 is connected to the joint cavity 3. The recess 22 preferably has a radius shape. When the collar 10 is positioned, connected to the joint cavity, the surface 23 of the recess 22 constitutes a continuation of the internally spherical joint surface 8 of the joint cavity 3. The collar positions the ball portion 5 to the joint cavity 3 and prevents the ball portion 5 of the femoral component 2 from being involuntarily dislocated from the joint cavity 3. The collar 10 also includes at least a second recess 24 on the inner edge of the outside of the collar, in the direction of the neck portion 6 when the ball-shaped portion is connected to the joint cavity and the collar 10 is connected to the joint cavity. The second recess (bevel) 24 of the collar increases the mobility of the shaft relative to the collar and the joint cavity. For the user, this results in a higher degree of mobility than without the recess 24.

With the first hole, the hip joint prosthesis is connected to the pelvic bone. In the embodiment this is done by the screws not passing through the joint cavity 3. With the inner holes, the locking member 4 is connected to threaded holes in the joint cavity 3 with screw joints.

In the exemplifying embodiment, the collar 10 is connected to the joint cavity 3 with screw joints or similar connection means. The positioning of the collar 10, the locking member 4, relative to the joint cavity 3 can be accomplished by a variety of techniques. Preferably, the collar 10 and the joint cavity 3 are connected to each other by screw joints which are through the collar 10 and are connected to holes in the joint cavity 3. Referring to Figures 4A - 4C, an exemplifying embodiment of the joint cavity 3 is shown. The joint cavity 3 comprises at least one first hole 25 constituting a through hole or alteratively a bottom hole. In the exemplifying embodiment, the joint cavity comprises at least one first hole 25, constituting a first through hole, and at least one second hole 26, constituting a second bottom hole or second through hole. In the shown embodiment, the joint cavity and the collar 10 are connected to each other with at least one first screw, and at least one second screw. The collar 10 and the joint cavity are held together by the screws that are screwed into the pelvic bone.

In the exemplifying embodiment, the collar 10 includes holes 27 of corresponding pitch and number as the number of holes in the joint cavity 3. The holes 27 in the collar 10 are preferably bevelled on the side which, when joined together, is intended to be turned from the joint cavity 3.

The material in the collar 10 is thicker where the load on the collar is relatively higher than parts of the collar where the load is relatively lower and the material is relatively thinner. In a preferred embodiment of the present collar 10, in its upper portion 28 it is relatively thicker than in its lower portion 29. In preferred embodiments, the thickness of the collar 10 decreases successively from the upper portion 28 toward the lower portion 29 (the portion with the opening 12).

In alterative embodiments, the connection of the collar 10 to the joint cavity 3 may occur by other suitable technology for the purpose. The alternative technology may consist of quick- fasteners or the like.

In an alterative embodiment, the material of the joint cavity 3 and the collar 10 are comprised of materials comprising or consisting of ceramic material or a glass material. For example, the material may be a material consisting (or comprising) of nitride glass or the like. Nitride glass is described, for example, in patent W02004063107. By using nitride glass, a durable joint cavity and a hard-to-break design are created.

In alterative embodiments, the holes in the joint cavity may be separate channels (holes) relative to the holes to connect the collar 10 (disc-shaped design) to the joint cavity 3. The joint cavity can be screwed into the pelvic bone with screw joints which do not join the collar with the joint cavity. In this case, the joint cavity includes separate bottom holes which are provided with threads (at least one section) (not shown in figures). The collar is screwed after the joint cavity is connected to the pelvic bone, but with screw joints in said bottom hole.

The locking (fixation) of the collar 10 to the pelvic bone is preferably done with screw joints. However, this does not preclude the use of any other type of fastener, fixing device or the like. For example, the locking can be done with some type of quick-locking device such as a device which can be inserted into holes in one direction which is caused to expand if it is moved in the other direction.

In the detailed description of the present invention, structural details may be omitted which will be apparent to a person of ordinary skill in the art and the device to which it relates. Such obvious design details are included to the extent required for a proper function to be obtained for the present hip joint prosthesis.

Although certain preferred embodiments have been shown in more detail, variations and modifications of the method and device may be apparent to those skilled in the art within the scope of the invention. All such modifications and variations are considered to fall within the scope of the claims.

Advantages of the Invention

With the present hip joint prosthesis, a number of benefits are achieved. One advantage is that the hip joint prosthesis with associated cohesive means causes the range of motion to become close in relation to a natural hip joint. Another advantage of screwing (the collar and joint cavity is screwed directly into the pelvic bone) results in essentially no dislocation of the joint head from the joint cavity (no luxation). An even further advantage of the present design is that the need to use adhesives or other foreign matter is substantially reduced. A further advantage of the present design is that it does not entail any significant temporal change in the operative procedure. Furthermore, the design has essentially no sharp edges or the like at the transition between the joint cavity and the joint head. The design also has the advantage of providing the body with less foreign material in relation to certain previously known designs. In the alterative embodiment where nitride glass is used, a joint cavity with a high degree of abrasion resistance is created while being difficult to break.