Adjustable hip joint endoprosthesis

• US 5,336,268 A
• Filed: 12/15/1992
• Issued: 08/09/1994
• Est. Priority Date: 12/17/1991
• Status: Expired due to Fees

• Current Assignee: Dr. Ing. H.C.F. Porsche Ag
• Original Assignee: Dr. Ing. H.C.F. Porsche Ag
• Inventors: Rispeter, Siegfried
• Primary Examiner(s): ISABELLA, DAVID J
• Application Number:
  US07/991,347
• Time in Patent Office: 602 Days
• Field of Search: 623/16, 623/18, 623/22, 623/23
• US Class Current: 623/22.4
• CPC Class Codes: A61F 2/3609 Femoral heads or necks; Connections of endoprosthetic heads or necks to endoprosthetic femoral shafts A61F2/3601 takes precedence
• CPC Class Codes: A61F 2002/30143 hexagonal
• CPC Class Codes: A61F 2002/30332 Conically- or frustoconically-shaped protrusion and recess
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30485 plastically deformable
• CPC Class Codes: A61F 2002/30494 Cooperating protrusions and recesses, e.g. radial serrations, located on abutting end surfaces of a longitudinal connection
• CPC Class Codes: A61F 2002/30558 Force-limiting means
• CPC Class Codes: A61F 2002/30561 breakable or frangible
• CPC Class Codes: A61F 2002/30795 Blind bores, e.g. of circular cross-section
• CPC Class Codes: A61F 2002/30822 Circumferential grooves
• CPC Class Codes: A61F 2002/365 Connections of heads to necks
• CPC Class Codes: A61F 2002/3652 Connections of necks to shafts
• 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 2220/0041 using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2230/0017 Angular shapes
• CPC Class Codes: A61F 2250/0073 Force-limiting means

Abstract

An adjustable hip joint endoprosthesis has an adjustable prosthesis head, which is connected with a stem that can be fixed in the femur. To absorb overloads, which would result in damage to the prosthesis part implanted into the femur and therefore in another implantation, a limiting element is provided. This limiting element is arranged in the prosthesis head and absorbs the overload by deformation, fracture or, in the case of a frictionally engaged connection, by sliding. After the occurrence of an overload, the limiting element must be replaced or re-adjusted.

Claims

1. A hip joint endoprosthesis comprising:

a stem fixable to a femur;

a prosthesis head connected to the stem, the prosthesis head including an adjusting device, locking devices coupled to the adjusting device that fix the adjusting device, a stationary link area coupled to at least one of the locking devices and a link element guided in the stationary link area;

an intermediate plate on the stationary link area;

a joint head, having a supporting body, which is held on the link element and the intermediate plate and is adjustable in a medial lateral direction with respect to the link area through the intermediate plate;

a tension element which penetrates the adjusting device and fixes the locking devices with respect to one another; and

a force limiting device in the prosthesis head, said force limiting device limiting to a maximum value a force to be transmitted by the hip joint endoprosthesis, wherein at least one of the stationary link area, the adjusting devices, the link element, the locking devices, the intermediate plate and the tension element have material cross-sections situated so as to be in a flux of force from the joint head to the stem, and wherein the force limiting device has a material cross-section with a strength of material that is exhausted earlier than all other material cross-sections situated in the flux of force from the joint head to the stem.

2. A hip joint endoprosthesis according to claim 1, wherein the force limiting device comprises a reduced material cross-section of the prosthesis head which forms a predetermined breaking point when the maximum value of the force is reached.

3. A hip joint endoprosthesis according to claim 1, wherein the force limiting device comprises a reduced material cross-section of the prosthesis head which forms a desired-deformation point when the maximum value of force is reached.

4. A hip joint endoprosthesis according to claim 1, wherein the force limiting device is provided between the prosthesis head and a cone and consists of a notch.

5. A hip joint endoprosthesis comprising:

a stem;

an adjustable prosthesis head which is connected with the stem;

a link area having an undercut groove extending in a direction of a medial-lateral displacement and provided with a first linear spur toothing on a surface and perpendicularly to said groove;

a link element guided in the groove, having cylindrical pin that has a bore with an internal thread;

an intermediate plate resting on the link area, a bore receiving the cylindrical pin, and a second linear spur toothing meshing with the first spur toothing of the link area;

a first radial spur toothing opposite the second spur toothing, the first radial spur toothing being on the top side of the plate radially with respect to the center point of the bore and is bounded by a circular-segment-shaped area;

a supporting body that rests on the intermediate plate, a pocket bore receiving the cylindrical pin of the link element and a second radial spur toothing being arranged on the supporting body in such a manner that it meshes with the first radial spur toothing of the plate, and a shaft projecting diagonally radially with respect to the bore carrying a cone for receiving a joint head, the joint head being provided with a conical recess corresponding to the cone, a pressing-in depth of this conical recess being pre-set by manufacture;

a single threaded pin, by means of a bore in the supporting body which extends approximately perpendicularly with respect to the direction of the medial-lateral displacement, is connected with the internal thread of the pin and, in a tensioned state, holds the link area, the intermediate plate and the supporting body and also the meshing locking devices in tension with respect to one another; and

a force limiting device provided on a diagonally radially projecting shaft on a starting piece of the cone of the supporting body, the force limiting device comprising a surrounding notch which, when a maximum force is reached which is below the maximum forces of all other elements, allows the shaft to be separated from the cone.