Artificial hip joint stem, stem inserter, artificial hip joint system including them, and artificial hip joint

1. An artificial hip joint stem, comprising:

a concave part located in a shoulder part of a stem body, the concave part comprising:

an opening part that opens into the shoulder part, and

a wall part extending along a stem central axis of the stem body,

the wall part comprising:

an inner wall portion and an outer wall portion opposed to each other, and

a front wall portion and a rear wall portion opposed to each other,

wherein a distance between the inner wall portion and the outer wall portion decreases going toward a distal end of the concave part from the opening part in a sectional view that is parallel to the stem central axis and includes the inner wall portion and the outer wall portion, and the distance between the inner wall portion and the outer wall portion begins to decrease at a location closer to the opening part of the concave part than the distal end of the concave part, and

both the front wall portion and the rear wall portion have a planar region in a sectional view that is parallel to the stem central axis and includes the front wall portion and the rear wall portion, and

the front wall portion comprises a front groove extending along the stem central axis and the rear wall portion comprises a rear groove extending along the stem central axis.

2. The artificial hip joint stem according to claim 1 , wherein both the inner wall portion and the outer wall portion have an arc shape or tapered shape in the sectional view that is parallel to the stem central axis and includes the inner wall portion and the outer wall portion.

3. The artificial hip joint stem according to claim 1 , wherein both the front wall portion and the rear wall portion are parallel to each other in the sectional view that is parallel to the stem central axis and includes the front wall portion and the rear wall portion.

4. The artificial hip joint stem according to claim 1 , wherein the front wall portion comprises:

a front inner region and a front outer region spaced away from each other with the front groove interposed therebetween; and

the rear wall portion comprises:

a rear inner region and a rear outer region spaced away from each other with the rear groove interposed therebetween.

5. The artificial hip joint stem according to claim 4 , wherein the front groove is located in a central region of the front wall portion, and the rear groove is located in a central region of the rear wall portion.

6. The artificial hip joint stem according to claim 1 , wherein the concave part further comprises a chamfered portion formed by chamfering an edge portion of the wall part located closer to the opening part.

7. The artificial hip joint stem according to claim 1 , wherein the concave part is partially located on the stem central axis.

8. The artificial hip joint stem according to claim 1 , wherein the concave part further comprises a screw hole located closer to a distal end of the concave part.

9. The artificial hip joint stem according to claim 1 , further comprising: a neck part extending from a proximal end of the stem body.

10. An artificial hip joint system, comprising an artificial hip joint stem according to claim 1 and a stem inserter comprising:

a disk-shaped front end part having a planar first surface, a planar second surface, and a curved surface shaped side surface connected to each of the planar first surface and the planar second surface;

a column-shaped shaft; and

a connection part connected to each of the front end part and the shaft,

wherein an inserter central axis extending between the planar first surface and the planar second surface is vertical with respect to an inserter rotation axis extending along a longitudinal direction of the shaft, and

the stem inserter is housed in the concave part of the stem in a state that the planar first surface and the planar second surface of the front end part are respectively opposed to the front wall portion and the rear wall portion of the concave part of the stem, and in a state that the stem inserter is inclinable around the inserter central axis.

11. The artificial hip joint system according to claim 10 , wherein the stem inserter has an inclination angle of ±35 to 45° in a front view of the stem inserter.

12. An artificial hip joint, comprising an artificial hip joint stem according to claim 9 , an artificial bone head fitted into the neck part, and a socket for slidably housing the artificial bone head.

13. The artificial hip joint system according to claim 10 , wherein the front end part of the stem inserter further comprises a first chamfered portion formed by chamfering an intersection of the planar first surface and the side surface, and a second chamfered portion formed by chamfering an intersection of the planar second surface and the side surface.

14. The artificial hip joint system according to claim 10 , wherein the connection part of the stem inserter comprises a width and a thickness, each of the width of the connection part and the thickness of the connection part increases from the front end part to the shaft.

15. The artificial hip joint stem according to claim 1 , wherein the inner wall portion and the outer wall portion are non-threaded.

16. The artificial hip joint system according to claim 10 , wherein the inner wall portion and the outer wall portion are non-threaded.