Circular surgical stapler with mating anvil and shell assembly

1. A surgical fastener applying apparatus comprising:

an elongated body portion having a proximal portion and a distal portion;

an anvil retainer extending from the distal portion of the elongated body portion; and

a head portion disposed adjacent the distal portion of the elongated body portion, the head portion including:

a shell assembly including a boss, a fastener guide, and a plurality of surgical fasteners, the fastener guide including a first tissue contact surface defining a plurality of slots, each of the plurality of surgical fasteners being received in a respective one of the plurality of slots of the fastener guide; and

an anvil assembly movable in relation to the shell assembly between a spaced apart position and an approximated position, the anvil assembly including an anvil head, a second tissue contacting surface, and a center rod extending proximally from the anvil head, the center rod including a proximal portion, a distal portion, and a central portion interposed between the proximal portion and the distal portion, the center rod including an annular protrusion positioned and configured to releasably engage the anvil retainer, an interference rib positioned and configured to engage the boss of the shell assembly to enhance frictional engagement of the center rod with the shell assembly, and a plurality of splines interposed between the interference rib and the annular protrusion.

2. The surgical fastener applying apparatus according to claim 1 , wherein the proximal portion of the center rod includes a tapered blunt end.

3. The surgical fastener applying apparatus according to claim 1 , wherein the annular protrusion of the center rod of the anvil assembly defines an outer transverse dimension and the anvil retainer defines an inner transverse dimension, the outer transverse dimension of the annular protrusion of the center rod of the anvil assembly being greater than the inner transverse dimension of the anvil retainer.

4. The surgical fastener applying apparatus according to claim 1 , wherein the center rod defines a plurality of apertures, each of the plurality of apertures being dimensioned to receive a suture.

5. The surgical fastener applying apparatus according to claim 4 , wherein the plurality of apertures are arranged longitudinally along the center rod.

6. The surgical fastener applying apparatus according to claim 4 , wherein the center rod includes a marker between adjacent apertures of the plurality of apertures.

7. The surgical fastener applying apparatus according to claim 4 , wherein the interference rib of the center rod is disposed proximal of the plurality of apertures of the center rod.

8. The surgical fastener applying apparatus according to claim 1 , wherein the anvil assembly includes a plurality of projections extending proximally from the anvil head, the plurality of projections engageable with the shell assembly.

9. The surgical fastener applying apparatus according to claim 8 , wherein the shell assembly defines a plurality of openings, each of the plurality of openings being positioned and configured to receive a respective one of the plurality of projections of the anvil head to facilitate alignment between the anvil assembly and the shell assembly.

10. The surgical fastener applying apparatus according to claim 8 , wherein each projection of the plurality of projections of the anvil assembly has a tapered end.

11. The surgical fastener applying apparatus according to claim 1 , wherein the second tissue contacting surface of the anvil assembly defines a plurality of pockets, each of the plurality of surgical fasteners being received in a respective one of the plurality of pockets to facilitate formation of the plurality of surgical fasteners.

12. The surgical fastener applying apparatus according to claim 1 , wherein the anvil retainer includes a tubular member, the tubular member of the anvil retainer including at least one flexible finger that is expandable radially outward to receive the annular protrusion of the center rod.

13. The surgical fastener applying apparatus according to claim 1 , wherein the anvil retainer defines an annular recess that is configured to receive the annular protrusion of the center rod.