Hip joint implant

Abstract

A hip implant for use in total hip replacement surgery. The hip implant consists of a femoral stem body designed to be fixed on two surfaces, the AP and lateral surfaces. The curvature of the implant is designed to mirror the shape of the femur, thereby increasing contact points with the inner surface of the medullary canal. The curvature of the lateral surface aligns with the inner surface associated with the medullary canal. The hip implant is designed to increase or maximize contact with the interior of the bone, i.e., the femur, while simultaneously reducing or minimizing stress risers or stress points, thereby reducing patient pain and the likelihood of implant failure.

Description

Technical Field

[0001] The present invention relates to medical devices and implant devices, and more particularly to hip joint prostheses or hip joint implants and their use in hip joint replacement methods.

Background Art

[0002] Hip joint implants or hip joint prostheses are typically used to assist individuals who require restoration of mobility, and reduce pain associated with various medical conditions such as hip joint diseases or injuries, or pain as a result of arthritis. Generally, hip joint replacement surgery involves replacing various anatomical structures of an individual hip joint with artificial components designed to function like normal anatomical features. Typically, an artificial acetabular cup is implanted in place of the individual acetabulum. Further, a femoral prosthesis is implanted within the patient's femur. While many hip joint replacement procedures have been successfully performed, long-term patient success often depends on how well the implant conforms within the femur.

Summary of the Invention

[0003] The present invention relates to a hip joint implant for use in hip joint replacement surgical procedures. The hip joint implant includes a femoral stem body designed to be fixed to two surfaces, namely the anterior-posterior [also referred to as AP] surface and the lateral surface. The curvature of the implant is designed to reflect the geometric shape of the femur, thus providing more contact points with the inner surface of the medullary cavity. The outer surface curvature cooperates with the inner surface associated with the medullary cavity. The hip joint implant is designed to provide increased or maximum contact within the bone, i.e., the femur, while reducing or minimizing stress risers or stress points, and thus reducing the likelihood of patient pain and / or implant failure.

[0004] Accordingly, it is an object of the present invention to provide an improved hip joint implant for use in hip joint replacement surgical procedures.

[0005] A further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures designed to be fixed within the AP plane.

[0006] A still further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures designed to be fixed within the lateral plane.

[0007] A still further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures designed to be fixed to two planes, the AP plane and the lateral plane.

[0008] A further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures having a curvature in two different planes.

[0009] A still further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures having a curvature in the AP plane and the lateral plane.

[0010] A still further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures having a curvature that reflects the curvature of the inner surface of the medullary cavity.

[0011] A further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures configured to maintain sufficient surface contact with the inner surface of the medullary cavity to reduce stress risers.

[0012] A still further object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures configured to distribute stress loads more evenly.

[0013] Yet another object of the present invention is to provide an improved hip joint implant for use in hip joint replacement surgical procedures configured to provide a plurality of contact points when inserted into the femur.

[0014] Other objects and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate some embodiments of the present invention. Any drawings included herein form part of the present specification, include exemplary embodiments of the present invention, and illustrate various objects and their features.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention enables various forms of embodiments. Hereinafter, the presently preferred ones shown in the drawings will be described. It should be understood that the present disclosure is to be regarded as an exemplification of the present invention and is not intended to limit the present invention to the specific embodiments illustrated, but rather the present disclosure should be understood as an exemplification of the present invention.

[0017] Referring to FIGS. 1-4, an exemplary example of a hip joint implant device used in hip joint replacement surgical procedures is shown. The geometric shape and / or curvature associated with the geometric shape of the implant 10 is designed to have the longest load-bearing surface or to reduce stress points when maximum contact with the bone is inserted. The longer the formed support surface, the more contact spots are provided compared to a single contact spot with the bone. The hip joint implant 10 has a proximal end 12, a proximal surface 14, a distal tip 16, and a body 18 also referred to as a stem 18. The proximal end 12 is a neck portion 20. The stem 18 or the hip joint implant 10 may be designed to have or maintain an elliptical shape in cross-section. This shape provides pressure to the bone in a hoop shape. The neck portion 20 terminates here in a femoral head engaging member 22 shown as a locking taper. The locking taper may be, for example, a jarno locking taper or a Brown & Sharp locking taper. The femoral head engaging member 22 has a size and shape such that it engages the implant acetabular liner and / or the implant femoral head to engage the acetabular socket. The proximal surface 14 can include a threaded opening 24 sized and shaped to receive a fixing member such as a screw.

[0018] In an exemplary embodiment, the hip joint implant 10 may be designed to have a neck length 21 of 34-44 mm. The hip joint implant 10 may include an offset 23. The stem may further be defined by an inner stern length 25 and a transverse stern length 27. To assist in fixing the hip joint implant 10 to the femur, a portion of the stem 18 can include a porous coating such as a titanium plasma spray [200 micrometer porosity] with a hydroxyapatite coating. Another portion of the hip joint implant 10 can include a roughened portion with a hydroxyapatite coating. Preferably, the hip joint implant 10 allows bone growth in the upper 2 / 3 of the hip joint implant 10. The distal tip 16 is preferably designed to prevent bonding to the bone when inserted.

[0019] The hip joint implant 10 is designed to optimize a proper fit when inserted into the femur, particularly when reflecting the shape of the inner surface of the medullary cavity. The hip joint implant stem 18 is designed to fix to two surfaces, namely, the AP surface and the lateral surface. Such fixation is achieved through the curvature of the hip joint implant 10 along the AP surface and the lateral surface. Further, the outer surface curvature is designed to cooperate with the inner surface related to the medullary cavity. Due to the geometric shapes resulting from these curvatures, the hip joint implant 10 can achieve more contact points with the inner surface of the medullary cavity.

[0020] FIG. 5 is a top view of the hip joint implant 10 facing downward toward the distal tip 16. FIG. 5 shows two surfaces, where the AP surface 26 moves downward along the length of the stem 18, the lateral surface 28 moves downward along the length of the stem 18, and moves outwardly toward the observer. FIG. 6 shows the hip joint implant 10 in the AP view showing the AP surface 26. FIG. 7 shows the hip joint implant 10 in the lateral view showing the lateral surface 28. FIG. 8 shows the intersection of the AP surface 26 and the lateral surface 28 along the length of the hip joint implant 10. Both surfaces represent the curvature of the geometric shape associated with the surfaces related to these surfaces. Thus, the surface 30 has a curvature along the length of the implant 10 indicated by the AP surface 26. The surface 32 has a curvature along the length of the implant 10 indicated by the lateral surface 28. The longitudinal axis 34 is defined by the intersection line of the two surfaces, the AP surface 26 and the lateral surface 28, along the length of the hip joint implant 10 [see also FIG. 9 where the hip joint implant 10 is removed for the purpose of explaining this axis]. From this longitudinal axis 34, the size of the hip joint implant device 10 can be defined as a length that extends preferably to a sufficient distance in all directions from the longitudinal axis 34 such that at least a part of the outer surface of the hip joint implant 10 contacts the inner surface of the medullary canal.

[0021] Figures 10 to 13 show embodiments of the femur 100 with a medullary cavity 102. Figure 10 is a top view of the femur 100 showing both the AP plane 104 of the femur and the outer surface 106 of the femur. Figure 11 shows the AP plane 104 of the femur having a longitudinal axis 108 in the AP view of the femur. Figure 12 shows the outer surface 106 of the femur having a longitudinal axis 110 in the lateral view of the femur. Figure 13 provides an alternative perspective view of the femur 100, showing the intersection of the AP plane 104 of the femur and the outer surface 1063 of the femur. The hip joint implant 10 is configured to reflect the anatomical features of the femur, so the geometric shape of the hip joint implant 10, particularly the curvature, is designed to provide anatomical conformity to maximize surface contact with the inner surfaces 112, 114 of the medullary cavity 102.

[0022] Referring to Figures 14 to 18, the hip joint implant 10 is shown inserted into the femur 100 and stationary within the medullary cavity 102. When inserted into the femur, based on the geometric shape and / or curvature of the hip joint implant 10, the implant device 10 makes maximum contact with the inner surfaces 112, 114 of the medullary cavity 102. Referring particularly to Figure 18, multiple contact points 116 are shown.

[0023] In a preferred embodiment, the distal tip portion 16 has a rounded or blunt shape. Further, the distal tip 16 may have a secondary curvature, preferably curving towards the central portion. This secondary curvature and blunt tip help reduce the likelihood of pain on the patient's side when the hip joint implant 10 is inserted into the medullary cavity 102. The secondary curvature must be sufficient so that the distal tip 16 does not contact or wear out any part of the femur.

[0024] The geometric shape of the hip joint implant 10 can be determined by reference values aggregated using characteristic three-dimensional curves. FIG. 19A shows a table 118 representing an example of the aggregated reference [curve] values. Based on the aggregated values, a parametrically defined 2D curve is generated that conforms to the general anatomical shape of the proximal femur 100 in an outside view (see FIGS. 19B and 19C). FIG. 19B shows the hip joint graft outside view curve 120. In FIG. 19C, the femur structure 100 is shown superimposed on the image shown in FIG. 19B. Based on the aggregated values, a parametrically defined 2D curve that conforms to the general anatomical shape of the proximal femur 100 can also be generated in an anterior-posterior [AP] view (see FIGS. 19D and 19E). FIG. 19D shows the hip joint implant stem AP view curve 122. In FIG. 19E, the thigh anatomical structure 100 is shown superimposed on the image shown in FIG. 19D.

[0025] The characteristic 3D curve 124 of the hip implant 10 results from the projection of 2D curves [120, 122] created in orthogonal planes (see FIGS. 19B and 19D). The characteristic 3D curve 124 can be defined as the intersection line of surfaces [AP surface 104 and outer surface 106] generated by linearly transforming both 2D curves perpendicularly to their respective planes (see FIGS. 20A and 20B). Three intermediate reference points 126 [PT2], 128 [PT3], and 130 [PT4] on the resulting curve 124 are positioned by the parametric arc length dimensions aggregated with respect to one end and are selected to create a biaxial alternating three-point contact of the implant stem within the femur cavity / socket / hole (see FIGS. 21A and 21B). Cross-sectional planes 132, 134, and 136 perpendicular to the 3D curve 124 are created at each of the three intermediate reference points 126, 128, and 130 (see FIGS. 22A and 22B). Cross-sectional shapes 140, 142, and 144 can be generated on each of the cross-sectional planes 132, 134, and 136 having intersecting local surfaces to guide the formation of various cross-sections of the hip implant stem 18 (see FIG. 23A). FIG. 23B shows the cross-sectional shape shown in FIG. 23A with the illustrated hip implant 10. The outer surface of the hip implant 10 can be designed by interpolating cross-sections modified along the length of the 3D curve 124.

[0026] All patents and publications described herein are indicative of the level of those skilled in the art to which the present invention pertains. All patents and publications are incorporated herein by reference as if each individual publication was specifically and individually indicated to be incorporated by reference.

[0027] Although certain forms of the invention are illustrated, it should be understood that the invention is not limited to the specific forms or configurations herein. It will be apparent to those skilled in the art that various changes can be made without departing from the scope of the invention, and the invention is not limited to what is contained and described herein.

[0028] Those skilled in the art will readily understand that the present invention is adapted to carry out the above object and obtain the above-described ends and advantages and the inherent advantages thereof. The embodiments, methods, procedures and techniques described herein are presently representative of preferred embodiments, are exemplary, and are not intended to limit the scope of the present invention. Changes and other uses will occur to those skilled in the art that are within the spirit of the present invention and defined by the appended claims. Although the present invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.

Claims

1. A hip joint implant for use in hip joint replacement surgery, comprising a femoral stem body extending along a three-dimensional curve from a proximal end designed to be fixed to the femur to a distal tip, The three-dimensional curve results from the intersection of a first two-dimensional curve extending toward the distal tip as viewed from the front and rear views and a second two-dimensional curve extending toward the distal tip as viewed from the lateral view orthogonal to the front and rear views, The first two-dimensional curve is along a first center line extending toward the distal tip while maintaining an equal distance from the opposing outer surface portions of the femoral stem body as viewed from the front and rear views, The second two-dimensional curve is along a second center line extending toward the distal tip while maintaining an equal distance from the opposing outer surface portions of the femoral stem body as viewed from the lateral view orthogonal to the front and rear views, The first two-dimensional curve, the second two-dimensional curve, or both the first two-dimensional curve and the second two-dimensional curve each include an inflection point where the respective curve changes from concave to convex, and the inflection point is closer to the distal tip than to the proximal end, a hip joint implant.

2. Each of the first two-dimensional curve and the second two-dimensional curve is linearly moved vertically in the respective front and rear views and lateral views to form the intersection, a hip joint implant for use in the surgical procedure of hip joint replacement according to Claim 1.

3. The hip joint implant for use in the surgical procedure of hip joint replacement according to Claim 1, wherein the three-dimensional curve reflects the curvature of the inner surface of the medullary cavity.

4. The femoral stem body includes an outer surface having a curvature, and the curvature of the outer surface includes an inflection point where the curvature changes from concave to convex, The hip joint implant for use in the surgical procedure of hip joint replacement according to Claim 3, wherein the curvature of the outer surface is configured to cooperate with the inner surface related to the medullary cavity.

5. The hip joint implant for use in the surgical procedure of hip joint replacement according to Claim 1, wherein the cross-section of the femoral stem body is elliptical.

6. The hip joint implant for use in hip joint replacement surgery according to Claim 1, wherein the femoral stem body includes a neck portion.

7. The hip joint implant for use in hip joint replacement surgery according to Claim 6, wherein the neck portion terminates in a femoral head engaging member configured to engage with an implant acetabular liner and / or an implant femoral head so as to engage with the acetabular socket. ​

8. The femoral head engaging member is a hip joint implant for use in hip joint replacement surgery according to claim 7, which is a locking taper.

9. The hip joint implant for use in the surgical procedure of hip joint replacement according to claim 1, wherein a part of the femoral stem body may include a porous coating.

10. The hip joint implant for use in the surgical procedure of hip joint replacement according to claim 9, wherein the porous coating includes a titanium plasma spray with a hydroxyapatite coating.

11. The hip joint implant for use in hip joint replacement surgery according to claim 1, wherein the cross-sectional shape of the femoral stem body tapers from the proximal end to the distal tip.

12. The hip joint implant for use in hip joint replacement surgery according to claim 11, wherein the distal tip has a rounded or blunt shape.

13. The hip joint implant for use in hip joint replacement surgery according to claim 11, wherein the distal tip extends from the inflection point to the end of the femoral stem body.

14. The hip joint implant for use in hip joint replacement surgery according to claim 13, wherein the distal tip extends along a secondary curvature of a length sufficient to prevent the distal tip from contacting or abutting any part of the femur.

15. The hip joint implant for use in hip joint replacement surgery according to claim 2, wherein the femoral stem body has a longitudinal axis defined by the three-dimensional curvature, and the longitudinal axis extends along the length of the femoral stem body.

16. The hip joint implant for use in the surgical procedure of hip joint replacement according to claim 15, wherein the femoral stem body has a cross-sectional shape that extends to a sufficient distance from the longitudinal axis such that at least a part of the outer surface of the femoral stem body contacts the inner surface of the medullary canal.

17. The hip joint implant for use in hip joint replacement surgery according to claim 1, wherein the femoral stem body includes an outer surface having a curvature corresponding to the three-dimensional curvature.

18. The first two-dimensional curvature is along a first center line extending toward the distal tip while maintaining an equal distance from the opposing outer surface portions of the femoral stem body in the anterior-posterior view, and the second two-dimensional curvature is along a second center line extending toward the distal tip while maintaining an equal distance from the opposing outer surface portions of the femoral stem body in the lateral view orthogonal to the anterior-posterior view. The hip joint implant for use in hip joint replacement surgery according to claim 17.

19. A hip joint implant for use in total hip arthroplasty, designed to be fixed to the femur and having a proximal end, a distal tip, and a body between the proximal end and the distal tip, including a femoral stem body having an outer surface that extends along a longitudinal axis passing through the proximal end, the distal tip, and the body and has a curvature along the longitudinal axis, a neck portion extending from the proximal end, wherein the longitudinal axis is along a three-dimensional curvature formed by the intersection of a two-dimensional curvature extending toward the distal tip while maintaining an equal distance from the opposing outer surface portions of the body in the anterior-posterior view and the two-dimensional curvature extending toward the distal tip while maintaining an equal distance from the opposing outer surface portions of the body in the lateral view orthogonal to the anterior-posterior view. The two-dimensional curvature includes an inflection point that changes from a concave surface to a convex surface in the anterior-posterior view, and the inflection point is located at a position closer to the distal tip than the inflection point from the neck portion. The hip joint implant.

20. further comprising a fastener receiving hole penetrating an opening formed at the proximal end of the femoral stem body, wherein the fastener receiving hole is offset with respect to the longitudinal axis so that the longitudinal axis does not pass through the opening. The hip joint implant for use in hip joint replacement surgery according to claim 19.

21. The three-dimensional curvature is selected to generate a biaxial alternating three-point contact in the femoral canal in which the femoral stem body is implanted. The hip joint implant for use in hip joint replacement surgery according to claim 19.

22. The distal tip has a rounded or blunt shape. The hip joint implant for use in hip joint replacement surgery according to claim 19.

23. The curvature of the outer surface has an inflection point, and at the inflection point, the curvature of the outer surface changes from a concave surface to a convex surface. The hip joint implant for use in hip joint replacement surgery according to claim 19.

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