Circular stapling device with alignment splines

1. An anvil assembly comprising:

an anvil shaft defining a longitudinal axis, the anvil shaft supporting a first spline, a second spline and a third spline, each of the first, second, and third splines including a pair of tapered camming surfaces that meet at a proximal end of the respective spline to define an apex, the apex of the first spline being positioned on the anvil shaft at a location proximal of the apex of the second spline, and the apex of the second spline being positioned on the anvil shaft at a location proximal of the apex of the third spline; and

an anvil head assembly supported on a distal end portion of the anvil shaft, the anvil head assembly supporting an anvil that defines a plurality of staple deforming recesses.

2. The anvil assembly of claim 1 , wherein the apex of the first spline is positioned on the anvil shaft proximally of the apex of the second spline a distance B, and the apex of the second spline is positioned on the anvil shaft proximally of the apex of the third spline a distance C, wherein B is from about 0.15 mm to about 0.2 mm, and C is from about 0.15 mm to about 0.2 mm.

3. The anvil assembly of claim 2 , wherein B is about 0.175 mm.

4. The anvil assembly of claim 1 , wherein each of the first, second, and third splines defines a longitudinal axis that is parallel to the longitudinal axis of the anvil shaft, wherein the apex of the first spline is aligned with the longitudinal axis of the first spline.

5. The anvil assembly of claim 4 , wherein the apex of the second spline is laterally offset from the longitudinal axis of the second spline a distance D and the apex of the third spline is laterally offset from the longitudinal axis of the third spline a distance E.

6. The anvil assembly of claim 5 , wherein the distance E is greater than the distance D.

7. The anvil assembly of claim 6 , wherein D is from about 0.15 mm to about 0.2 mm, and E is from about 0.3 mm to about 0.4 mm.

8. A tool assembly comprising:

an anvil assembly including:

an anvil shaft defining a longitudinal axis, the anvil shaft supporting a first spline, a second spline and a third spline, each of the first, second, and third splines including a pair of tapered camming surfaces that meet at a proximal end of the respective spline to define an apex, the apex of the first spline being positioned on the anvil shaft at a location proximal of the apex of the second spline, and the apex of the second spline being positioned on the anvil shaft at a location proximal of the apex of the third spline; and

an anvil head assembly supported on a distal end portion of the anvil shaft, the anvil head assembly supporting an anvil that defines a plurality of staple deforming recesses; and

a shell assembly having a staple cartridge supporting a plurality of staples, and a shell housing having an inner housing portion defining a plurality of housing splines, wherein adjacent splines of the plurality of housing splines define channels, the channels being dimensioned to receive the first, second, and third splines of the anvil shaft.

9. The tool assembly of claim 8 , wherein the apex of the first spline of the anvil shaft is positioned proximally of the apex of the second spline of the anvil shaft a distance B, and the apex of the second spline of the anvil shaft is positioned proximally of the apex of the third spline a distance C, wherein B is from about 0.15 mm to about 0.2 mm, and C is from about 0.15 mm to about 0.2 mm.

10. The tool assembly of claim 9 , wherein B and C are about 0.175 mm.

11. The tool assembly of claim 8 , wherein each of the first, second, and third splines defines a longitudinal axis that is parallel to the longitudinal axis of the anvil shaft, wherein the apex of the first spline is aligned with the longitudinal axis of the first spline.

12. The tool assembly of claim 11 , wherein the apex of the second spline is laterally offset from the longitudinal axis of the second spline a distance D and the apex of the third spline is laterally offset from the longitudinal axis of the third spline a distance E.

13. The tool assembly of claim 12 , wherein the distance E is greater than the distance D.

14. The tool assembly of claim 13 , wherein the distance D is from about 0.15 mm to about 0.2 mm, and the distance E is from about 0.3 mm to about 0.4.

15. An anvil assembly comprising:

an anvil shaft defining a longitudinal axis, the anvil shaft supporting a plurality of splines including a first spline and a second spline, each of the plurality of splines including a pair of tapered camming surfaces that meet at a proximal end of the respective spline to define an apex, wherein each of the first and second splines defines a longitudinal axis that is parallel to the longitudinal axis of the anvil shaft, the apex of the first spline being aligned with the longitudinal axis of the first spline and the apex of the second spline being laterally offset from the longitudinal axis of the second spline; and

an anvil head assembly supported on a distal end portion of the anvil shaft, the anvil head assembly supporting an anvil that defines a plurality of staple deforming recesses.

16. The anvil assembly of claim 15 , wherein the plurality of splines includes a third spline, the apex of the second spline being laterally offset from the longitudinal axis of the second spline a distance D and the apex of the third spline being laterally offset from the longitudinal axis of the third spline a distance E.

17. The anvil assembly of claim 16 , wherein E is greater than D.

18. The anvil assembly of claim 17 , wherein the apex of the first spline is positioned proximally of the second spline and the apex of the second spline is positioned proximally of the apex of the third spline.

19. The anvil assembly of claim 15 , wherein the apex of the first spline is positioned proximally of apex of the second spline.