Circular stapling instruments

1. A cartridge assembly for a circular stapler, the cartridge assembly comprising:

a housing;

a staple cartridge supported on the housing and including a plurality of staples arranged in an annular array;

a pusher assembly operably disposed within the housing and configured to eject the staples from the staple cartridge; and

a knife assembly operably disposed within the housing, the knife assembly including a knife pusher and a knife, the knife being selectively fixed relative to the knife pusher and the pusher assembly, wherein the knife pusher and the pusher assembly are mounted for independent movement relative to the knife, the knife pusher being disposed outward of the knife during a first actuation of the cartridge assembly such that the knife pusher moves over the knife, and the knife pusher engaging the knife during a second actuation of the cartridge assembly.

2. The cartridge assembly of claim 1 , wherein the knife pusher is advanced a first distance during the first actuation and retracted a second distance following the first actuation, the second distance being greater than the first distance.

3. The cartridge assembly of claim 1 , wherein the pusher assembly includes a pusher having a ridge formed about an inner surface thereof configured to engage the knife pusher.

4. The cartridge assembly of claim 1 , wherein the knife pusher includes a plurality of distally extending fingers.

5. The cartridge assembly of claim 4 , wherein each distally extending finger of the plurality of distally extending fingers includes a radially inward extending distal portion.

6. The cartridge assembly of claim 5 , wherein the radially inward projecting distal portion of each of the distally extending fingers of the plurality of distally extending fingers is configured to selectively engage the knife.

7. The cartridge assembly of claim 6 , further comprising a knife ring having a groove configured to receive the radially inward projecting distal end of each of the distally extending fingers of the plurality of distally extending fingers during the second actuation of the cartridge assembly.

8. The cartridge assembly of claim 7 , wherein the radially inward projecting distal portion of each of the distally extending fingers of the plurality of distally extending fingers is disposed distal of the groove in the knife ring when the handle assembly is in a first or initial condition.

9. The cartridge assembly of claim 4 , wherein the knife is attached to a knife ring having an outwardly flared proximal portion.

10. The cartridge assembly of claim 9 , wherein the distally extending fingers of the plurality of distally extending fingers slide over the proximal portion of the knife ring during the first actuation.

11. The cartridge assembly of claim 10 , wherein the proximal portion of the knife ring defines a groove for receiving the fingers.

12. The cartridge assembly of claim 1 , wherein during the first actuation the pusher assembly is advanced independently of the knife.

13. The cartridge assembly of claim 1 , wherein the housing includes an outer cylindrical portion and an inner cylindrical portion.

14. The cartridge assembly of claim 13 , wherein the pusher assembly and the knife are selectively received between the inner and outer cylindrical portions of the housing.

15. The cartridge assembly of claim 14 , wherein the inner cylindrical portion includes a detent configured to engage the knife assembly and prevent movement of the knife.

16. The cartridge assembly of claim 15 , wherein the knife is attached to a knife carrier having a movable protrusion to allow the knife carrier to move past the detent.

17. The cartridge assembly of claim 1 , wherein the pusher assembly and the knife are substantially cylindrical.