Neck-preserving-stem NPS
OwnerKlaus Draenert, Klaus Blaesiusinventors
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Abstract
The present invention essentially relates to a hip joint endoprosthesis stem for cement-free or cemented anchoring in bones that is anchored in the femural neck and in the proximal metaphysis and preserves the internal spongiosa and compact structures that reinforce the femur, that gives the design element axial access to the medullary canal, and possesses parabolically curved outer surfaces to optimize the transfer of force to the bone.
Claims15
Anatomical femur component of an artificial hip joint for cement-free and cemented implantation characterized by the following elements:
- the stem of the prosthesis has an indentation on the dorsal side that extends axially in a straight line into the tip of the prosthesis and on the proximal end of the dorsal side engages the bone structures of the femural neck from the transition to the greater trochanter;
- the dorsal concave indentation divides the stem proximally into two distinct portions:
- a medial portion that flares out proximally in a conical shape, and a lateral portion that is almost cylindrical axially along the length of the stem;
- the cross section of the stem has a basic “comma” shape on the proximal end.
The femur component of claim (1) characterized by the following elements:
- the stem of the prosthesis has an indentation on the dorsal side that extends axially in a straight line into the tip of the prosthesis and on the proximal end of the dorsal side engages the bone structures of the femural neck from the transition to the greater trochanter;
- the dorsal concave indentation divides the stem proximally into two distinct portions:
- a medial portion that flares out proximally in a conical shape, and a lateral portion that is almost cylindrical axially along the length of the stem;
- the prosthesis stem also has an indentation on the ventral side that extends axially in a nearly straight line into the tip of the prosthesis and divides the stem into a lateral, nearly cylindrical portion, and a medial portion that is conically flared on the proximal end.
The femur component of an artificial hip joint for cement-free or cemented implantation characterized by the following elements:
- the prosthesis stem has an anatomically configured, conical, right/left symmetrically opposite medial portion, and
- an axially oriented more-or-less cylindrical portion that is securely connected to said medial portion.
The femur component of claims (1) to (3), wherein the proximal cross section is comma shaped—concave on the dorsal side and having a punctiform bulge in the medial area—and it is symmetrically opposite to the right and left.
The femur component of claims (1) to (4), constructed in such a way that the femur stem axis coincides with the femur canal axis and in the frontal plane the collum-center axis describes an angle between 125° and 145°, generally 135°, with the diaphysis axis (CCD angle), and in the axial top view an angle of 5° to 15°, generally 7°, between the diaphysis and the neck axis—a so-called antetorsion angle—is defined.
The femur component of claims (1) to (5), constructed in such a way that the ventral surface is axially convex and on the ventral side it has concave curvature in such a way that the center of curvature is on the ventral side and the radius of curvature continuously decreases in the proximal direction (parabola).
The femur component of claims (1) to (6), constructed in such a way that the medial outer surface is axially convex and is concave along the medial contour, in such a way that the outer-surface center of curvature is medial and its radius decreases continuously in the proximal direction (parabola).
The femur component of claims (1) to (7), constructed in such a way that the dorsal outer surface of the stem is curved about the axis in a convex-concave-convex configuration from the lateral to the medial in the shape of a breaking wave or a rounded “3” having asymmetrical halves and a rounded transition.
The femur component of claims (1) to (8), constructed in such a way that the lateral outer surface is designed to be largely straight and cylindrical.
The femur component of claims (1) to (9), constructed in such a way that the ventral surface and/or medial surface and/or dorsal surface and/or lateral surface is/are structured by means of coaxially oriented longitudinal beads.
The femur component of claims (1) to (10), constructed in such a way that the stem makes a transition to the cone via a shoulder component (head/neck/stem transition), and, as a modular system, the cone can accept various heads, either centrically or eccentrically, and, to accept a tension anchor, the cone has a central hole and/or one or more holes in the shoulder.
The femur component of claims (1) to (11) constructed in such a way that the cone is oriented between 2° and 9°, generally 5°, the CCD angle does not change, and the offset also remains unchanged, the axis of the cone, however, is projected onto the laterodorsal circumference of the compact femur 2 cm-4 cm below the tuberculum innominatum.
The femur component of claims (1) to (12) constructed in such a way that the implant is made of titanium, tantalum, CoCrMo, or an alloy of titanium, tantalum, or stainless steel.
The femur component of claims (1) to (13) constructed in such a way that the surface of the proximal half has a roughness of 50-250 μm, preferably 80-100 μm.
Dependencies are inferred from the claim text.