Asymmetric hip stem
AssigneeStryker Technlogies Corporation
InventorsPhilip C. Noble, Anthony K. Hedley, Michael J. Schulzki, William J. Kelly, Jr.
Life of this patent
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Abstract
An improved asymmetric femoral hip stem component for use in cementless hip replacement procedures is described. The stem comprises a proximal region having a novel three-dimensional configuration to allow for better fit and stability of the stem within the femoral intramedullary canal with minimal removal of strong bone therefrom. The stem further includes a twist isolated in the mid-stem region to improve fit while minimizing enlargement of the femoral canal. A distal end comprising a rotated internal slot is also described, wherein the slot reduces bending stiffness of the stem in both the coronal and sagittal planes.
Claims9
A prosthetic femoral hip stem comprising posterior, anterior, medial, and lateral faces, said stem further including:
- (a) a longitudinal axis;
- (b) a distal region having a distal tip, wherein cross-sections taken perpendicular to said longitudinal axis each include a distal region center;
- (c) a proximal region,;
- wherein cross sections taken perpendicular to said longitudinal axis through said proximal region each have a medial-most point and a center, such that a line taken from said proximal region center to said medial-most point is in parallel alignment with a line of each adjacent and superjacent cross-section of said proximal region;
- and
- (d) a mid-stem region disposed between said distal and proximal regions, said stem further including a twist extending about the longitudinal axis of the stem throughout said mid-stem region, said twist generally beginning at a distal boundary of the mid-stem region and ending at a proximal boundary of the mid-stem region, such that cross-sections taken perpendicular to said longitudinal axis through said mid-stem region each have a medial-most point and a center, such that a line taken from said mid-stem region center to said mid-stem medial-most point is in non-parallel alignment with a line of each adjacent and superjacent cross-section of said mid-stem region due to said twist.
A prosthetic femoral hip stem comprising posterior, anterior, medial, and lateral faces, said stem further including:
- (a) a longitudinal axis;
- (b) a distal region having a distal tip, wherein cross-sections taken perpendicular to said longitudinal axis each include a distal region center, said distal region further including an internal slot extending proximally from a distal tip and along said longitudinal axis, said longitudinal axis further intersecting said distal center;
- (c) a proximal region, wherein cross sections taken perpendicular to said longitudinal axis through said proximal region each have a medial-most point and a center, such that a line taken from said proximal region center to said medial-most point is in parallel alignment with a line of each adjacent and superjacent cross-section of said proximal region;
- and
- (d) a mid-stem region disposed between said distal and proximal regions, said stem further including a twist extending about the longitudinal axis of the stem throughout said mid-stem region, said twist generally beginning at a distal boundary of the mid-stem region and ending at a proximal boundary of the mid-stem region, such that cross-sections taken perpendicular to said longitudinal axis through said mid-stem region each have a medial-most point and a center, such that a line taken from said mid-stem region center to said mid-stem medial-most point is in non-parallel alignment with a line of each adjacent and superjacent cross-section of said mid-stem region due to said twist.
A prosthetic femoral hip stem comprising posterior, anterior, medial, and lateral faces, said stem further including:
- (a) a longitudinal axis;
- (b) a distal region, wherein cross sections taken perpendicular to said longitudinal axis each include a distal region center;
- (c) a proximal region, wherein cross sections taken perpendicular to said longitudinal axis through said proximal region each have a medial-most point and a center, such that a line taken from said proximal region center to said medial-most point is in parallel alignment with a line of each adjacent and superjacent cross-section of said proximal region;
- and
- (d) a mid-stem region positioned between said distal and proximal regions;
- wherein said stem further includes a twist extending about the longitudinal axis of the stem, said twist generally beginning at a distal boundary of the mid-stem region and ending at a proximal boundary of the mid-stem region, such that cross-sections taken perpendicular to said longitudinal axis through said mid-stem region each have a medial-most point and a center, such that a line taken from said mid-stem region center to said mid-stem medial-most point is in non-parallel alignment with a line of each adjacent and superjacent cross-section of said mid-stem region due to said twist, and wherein at least one cross-section taken perpendicular to said longitudinal axis through said proximal region includes:
- (e) a substantially arcuate anterior side having a varying radius of curvature;
- (f) a posterior side having a concavity;
- (g) a substantially arcuate medial side having a radius of curvature;
- and
- (h) a substantially arcuate lateral side that slopes anteriorly to define an acute angle of declination.
Dependencies are inferred from the claim text.