Femoral hip-joint prosthesis with a logarithmically extending curvature

• US 6,383,228 B1
• Filed: 10/14/1999
• Issued: 05/07/2002
• Est. Priority Date: 02/11/1998
• Status: Expired due to Fees

• Current Assignee: Plus Endoprothetik AG
• Original Assignee: Plus Endoprothetik AG
• Inventors: Schmotzer, Hans F.
• Primary Examiner(s): Isabella, David J.
• Assistant Examiner(s): Chattopadhyay, Urmi
• Application Number:
  US09/381,852
• Time in Patent Office: 936 Days
• Field of Search: 623/23-5-, 623/23-2-, 623/23-4-, 623/23.35
• US Class Current: 623/23.35
• CPC Class Codes: A61F 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2/367 Proximal or metaphyseal parts of shafts trochanteric devices connected to said proximal parts A61F2/30739
• CPC Class Codes: A61F 2/3672 Intermediate parts of shafts
• CPC Class Codes: A61F 2/3676 Distal or diaphyseal parts of shafts
• CPC Class Codes: A61F 2002/30112 Rounded shapes, e.g. with rounded corners
• CPC Class Codes: A61F 2002/30113 circular
• CPC Class Codes: A61F 2002/30151 rhomboidal or parallelogram-shaped
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30154 square
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30291 spirally-coiled, i.e. having a 2D spiral cross-section
• CPC Class Codes: A61F 2002/30332 Conically- or frustoconically-shaped protrusion and recess
• CPC Class Codes: A61F 2002/30943 using mathematical models
• 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 2220/0033 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 2230/0006 circular
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0021 : square
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2230/0091 : helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium

Abstract

A femoral hip-joint prosthesis having a tapered stem for implantation by cement. The prosthesis has a collarless shoulder at a proximal end and a stem extending therefrom to a distal end in tapered fashion. A logarithmically extending curvature of anterior and posterior side faces of a first subsidiary section of the stem combine with straight converging lines of a second subsidiary section of the stem to uniformly distribute pressure in the prosthesis within the femoral hip bone.

Claims

1. A femoral hip-joint prosthesis for implantation by cement with a stem having a longitudinal axis, a proximal end, a distal end, a collarless shoulder, an anterior side face and a posterior side face, a first subsidiary section and a second subsidiary section, wherein the collarless shoulder is located in the region of said proximal end;

the stem has in at least one portion a quadrilateral cross section;

the stem extends along the longitudinal axis and tapers from the proximal end toward the distal end;

the first subsidiary section begins in the region of the proximal end and extends along the longitudinal axis;

the second subsidiary section is located distally of the first subsidiary section and extends along the longitudinal axis; and

the anterior side face and the posterior side face, in the direction of the longitudinal axis, have, in the first subsidiary section, a logarithmically extending curvature and thereafter, in the second subsidiary section, extend in a straight line and converge.

2. The femoral hip-joint prosthesis as claimed in claim 1, wherein the stem has medial and lateral side faces, the medial and lateral side faces each having, in the direction of extension of the stem, in a first subsidiary section beginning at the shoulder, a logarithmically extending curvature, and thereafter, in a second subsidiary section, extending in a straight line and converging.

3. The femoral hip-joint prosthesis as claimed in claim 1, wherein the second subsidiary section, starting from the distal end, extends along up to half of the stem.

4. The femoral hip-joint prosthesis as claimed in claim 1, wherein the quadrilateral cross section forms edges which are rounded.

5. The femoral hip-joint prosthesis as claimed in claim 4, wherein the rounded edges have a radius of between 1 and 3 mm.

6. The femoral hip-joint prosthesis as claimed in claim 1, wherein the quadrilateral cross section is selected from the group consisting of the trapezoidal, rectangular and square shapes, the cross section, from the proximal end to the distal end of the stem, being able to merge from one into another of these shapes.

7. The femoral hip-joint prosthesis as claimed in claim 1, wherein the stem has a third subsidiary section in the distal end section with a circular cross section.

8. The femoral hip-joint prosthesis as claimed in claim 1, wherein the side faces, starting from the distal end, extend to one another along a length of up to 5 mm.

9. The femoral hip-joint prosthesis as claimed in claim 1, wherein at least the side faces of the stem have a highly polished surface.

10. The femoral hip-joint prosthesis as claimed in claim 1, wherein the second subsidiary section, starting from the distal end, extends along a third subsidiary section of the stem.