Variable geometry rim surface acetabular shell liner

• US 7,682,398 B2
• Filed: 11/28/2006
• Issued: 03/23/2010
• Est. Priority Date: 03/14/2000
• Status: Expired due to Fees

• Current Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Original Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Inventors: McKinnon, Brian W., Croxton, Michael A.
• Primary Examiner(s): McDermott; Corrine M
• Assistant Examiner(s): WOLF, MEGAN YARNALL
• Application Number:
  US11/605,921
• Publication Number:
  US 20070106389A1
• Time in Patent Office: 1,211 Days
• Field of Search: 623 2215- 2219, 623/22.21, 623/22.39, 623/23.43
• US Class Current: 623/22.24
• CPC Class Codes: A61B 17/86 Pins or screws or threaded wires; nuts therefor A61B17/72 take precedence
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2/30942 for designing or making customized prostheses, e.g. using templates, CT or NMR scans, finite-element analysis or CAD-CAM techniques
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/34 Acetabular cups
• CPC Class Codes: A61F 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/4637 for connecting or disconnecting two parts of a prosthesis
• CPC Class Codes: A61F 2002/30112 Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30324 differing in thickness
• CPC Class Codes: A61F 2002/30332 Conically- or frustoconically-shaped protrusion and recess
• CPC Class Codes: A61F 2002/30367 with additional means for preventing said rotation
• CPC Class Codes: A61F 2002/30403 Longitudinally-oriented cooperating ribs and grooves on mating lateral surfaces of a mainly longitudinal connection
• CPC Class Codes: A61F 2002/30487 Circumferential cooperating grooves and beads on cooperating lateral surfaces of a mainly longitudinal connection
• CPC Class Codes: A61F 2002/30495 using a locking ring
• CPC Class Codes: A61F 2002/305 Snap connection
• CPC Class Codes: A61F 2002/3054 about a connection axis or implantation axis for selecting any one of a plurality of radial orientations between two modular parts, e.g. Morse taper connections, at discrete positions, angular positions or continuous positions
• CPC Class Codes: A61F 2002/30616 Sets comprising a plurality of prosthetic parts of different sizes or orientations
• CPC Class Codes: A61F 2002/30787 inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30952 : using CAD-CAM techniques or NC-techniques
• CPC Class Codes: A61F 2002/30975 : made of two halves
• CPC Class Codes: A61F 2002/3233 : having anti-luxation means for preventing complete dislocation of the femoral head from the acetabular cup
• CPC Class Codes: A61F 2002/3401 : with radial apertures, e.g. radial bores for receiving fixation screws
• CPC Class Codes: A61F 2002/344 : the inner shell having an inner hip femoral head-receiving cavity offset from its centre line
• CPC Class Codes: A61F 2002/3441 : the outer shell having an outer surface and an inner insert receiving cavity being angularly inclined with respect to the longitudinal axis of the outer surface
• CPC Class Codes: A61F 2002/3443 : with an anti-luxation elevated rim portion, e.g. on the inner shell
• CPC Class Codes: A61F 2002/3611 : Heads or epiphyseal parts of femur
• CPC Class Codes: A61F 2002/3625 : Necks
• CPC Class Codes: A61F 2002/365 : Connections of heads to necks
• CPC Class Codes: A61F 2002/4631 : the prosthesis being specially adapted for being cemented
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0033 : made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2230/0004 : Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2250/0036 : differing in thickness
• CPC Class Codes: A61F 2310/00011 : Metals or alloys
• CPC Class Codes: A61F 2310/00179 : Ceramics or ceramic-like structures

Abstract

There is provided an acetabular shell liner, and particularly a constrained liner, having a variable rim surface geometry to improve the range of motion of a femoral component within the liner and decrease the incidence of dislocation and subluxation. There are also provided methods of making and using the acetabular shell liner. Prosthetic devices, and particularly hip joint prostheses, containing the acetabular shell liner having a variable rim surface geometry are also provided.

Claims

1. A constrained liner having a central axis, comprising:

(a) an internal concave surface of the constrained liner having an opening adapted to receive a head of a femoral component, wherein the internal concave surface provides greater than hemispherical coverage of the head at a constraining portion of the constrained liner;

(b) an external surface positioned on an opposing side of the internal concave surface; and

(c) a rim located at the opening of the internal concave surface, the rim comprising a variable angle chamfer surface separate from the constraining portion, the variable angle chamfer surface forming at least a portion of the rim that varies angularly with respect to the central axis of the constrained liner around the rim.

2. The constrained liner of claim 1, wherein the variable angle chamfer surface is defined at least in part by, given a desired angular position of the liner in a patient,

one or more angles, each angle defined by a point on the rim at an outer limit of the range of motion, of at least one femoral component whose head is adapted to be received in the internal concave surface of the liner measured relative to the central axis of the constrained liner;

wherein the one or more angles of the variable angle chamfer surface vary around the rim of the liner in a manner corresponding to the cross-sectional shape of the portion of the at least one femoral component that is in an impingement condition with the liner.

3. The constrained liner of claim 1, wherein the liner is anteverted, neutral, or offset.

4. The constrained liner of claim 1, wherein the variable angle chamfer surface comprises a plurality of variable angles.

5. The constrained liner of claim 1, wherein the variable angle chamfer surface comprises a face having a series of various angles that change substantially continuously along the rim surface.

6. The constrained liner of claim 1, wherein the variable angle chamfer surface comprises a plurality of variable angles, each of the plurality of variable angles defined as an angle at any point on or near the rim of the liner at which the surface of the chamfer is positioned relative to the central axis of the opening of the internal diameter of the liner.

7. The constrained liner of claim 1, wherein the variable angle chamfer surface is defined at least in part by, at each of a plurality of locations around the rim, an angle determined using a group of impingement angles corresponding to a plurality of femoral components in an impingement condition with the constrained liner whose heads are adapted to be received in the internal concave surface of the liner.

8. The constrained liner of claim 1, wherein the variable angle chamfer surface varies around the rim of the liner and is symmetric about a plane.

9. The constrained liner of claim 1, wherein the constrained liner is a one-piece liner.

10. The constrained liner of claim 1, wherein the central axis is offset from a center of a surface in which the liner is adapted to be received.

11. The constrained liner of claim 1, wherein the center of the internal concave surface is shifted laterally by up to 10mm.

12. The constrained liner of claim 1, wherein the central axis is anteverted with respect to a surface in which the liner is adapted to be received.

13. The constrained liner of claim 1, wherein the variable angle chamfer surface defines an impingement angle at each of a plurality of radial locations around the rim of the liner that is specified by a computer simulation of a constrained liner and a femoral component, wherein the computer simulates rotation of the femoral component within the liner to define a radial location on the rim of the liner where the femoral component impinges on the rim, and determines the impingement angle and cross-sectional shape of the femoral component on the rim at that radial location.

14. The constrained liner of claim 1, wherein the variable angle chamfer surface defines an impingement angle at each of a plurality of radial locations around the rim of the liner that is specified by manually rotating the femoral component within a constrained liner to define a radial location on the rim of the liner where the femoral component impinges on the rim, and determining the impingement angle and cross-sectional shape of the femoral component on the rim at that radial location.

15. The constrained liner of claim 1, wherein the shape of the variable angle chamfer surface varies around the rim of the liner in a manner corresponding to a cross-sectional shape formed by a femoral component that is in an impingement condition with the rim of the constrained liner.

16. The constrained liner of claim 1, wherein the variable angle chamfer surface comprises a plurality of variable angle segments.

17. The constrained liner of claim 1, wherein the variable angle chamfer surface comprises a plurality of constant angle segments.

18. The constrained liner of claim 1, wherein the constrained liner provides more than hemispherical coverage and the variable angle chamfer surface allows the constrained liner to receive a head of a femoral component while also providing a greater range of motion than that provided by a constrained liner without a variable angle chamfer surface.

19. The constrained liner of claim 1, wherein the central axis is anteverted at about 15 degrees with respect to a surface in which the liner is adapted to be received.

20. The constrained liner of claim 1, wherein the variable angle chamfer surface comprises a plurality of variable angles, and wherein each of the plurality of variable angles range from about 100 degrees to about 200 degrees.

21. The constrained liner of claim 1, wherein the variable angle chamfer surface varies around the rim of the liner and is asymmetric about a plane.

22. The constrained liner of claim 1, wherein the liner further comprises a hood member.

23. A prosthetic device comprising:

(a) an acetabular shell comprising an internal concave surface adapted to receive a constrained liner and an external surface adapted to be received in an acetabulum; and

(b) a constrained liner having;

(i) an internal concave surface of the constrained liner having an opening adapted to receive a head of a femoral component, wherein the internal concave surface provides greater than hemispherical coverage of the head at a constraining portion of the constrained liner;

(ii) an external surface positioned on an opposing side of the internal concave surface; and

(iii) a rim located at the opening of the internal concave surface, the rim comprising a variable angle chamfer surface separate from the constraining portion, the variable angle chamfer surface forming at least a portion of the rim that varies angularly with respect to the central axis of the constrained liner around the rim.

24. The prosthetic device of claim 23, wherein the wherein the constrained liner provides more than hemispherical coverage and the variable angle chamfer surface allows the constrained liner to receive a head of a femoral component, while also providing a greater range of motion than that provided by a constrained liner without a variable angle chamfer surface.

26. The method of claim 23, wherein the constrained liner provides more than hemispherical coverage and the variable angle chamfer surface allows the constrained liner to receive a head of a femoral component, while also providing a greater range of motion than that provided by a constrained liner without a variable angle chamfer surface.

25. A method of replacing a hip joint in a patient comprising:

(a) providing a constrained liner having;

(i) an internal concave surface of the constrained liner having an opening adapted to receive a head of a femoral component, wherein the internal concave surface provides greater than hemispherical coverage of the head at a constraining portion of the constrained liner;

(ii) an external surface positioned on an opposing side of the internal concave surface; and

(iii) a rim located at the opening of the internal concave surface, the rim comprising a variable angle chamfer surface separate from the constraining portion, the variable angle chamfer surface forming at least a portion of the rim that varies angularly with respect to the central axis of the constrained liner around the rim,

(b) providing an acetabular shell comprising an internal concave surface adapted to receive the liner and an external surface adapted to be received in an acetabulum;

(c) surgically implanting and securing the shell in the acetabulum of a patient;

(d) securing the liner in the internal concave surface of the shell;

(e) providing a femoral component, comprising a head, neck and a stem, wherein the head is adapted to articulate within the internal concave surface of the liner;

(f) surgically implanting the stem of the femoral component into the femur of a patient; and

(g) installing the head of the femoral component into the internal concave surface of the liner.