Tissue thickness compensator comprising tissue ingrowth features

A staple cartridge for stapling the tissue of a patient, comprising:

• a cartridge body, wherein a plurality of staple cavities are defined in the cartridge body;
• a plurality of staples removably positioned in the staple cavities;
• and
• a compressible tissue thickness compensator releasably secured relative to the cartridge body, wherein the tissue thickness compensator is configured to adapt in thickness in response to the thickness of the tissue and adaptively apply different pressures to the tissue based on the thickness of the tissue captured within the staples, wherein the compressible tissue thickness compensator comprises a plurality of fibers, and wherein the plurality of fibers comprises:
• a first group of fibers oriented in a first direction, wherein the first group of fibers comprises a first set of material properties comprising a first medicament;
• a second group of fibers oriented in a second direction, wherein the second group of fibers comprises a second set of material properties comprising a second medicament that is different than the first medicament, and wherein the second direction is different than the first direction;
• and
• a plurality of non-uniform voids defined between adjacent fibers in the compressible tissue thickness compensator, wherein the plurality of non-uniform voids promotes tissue and cellular ingrowth between the first and second groups of fibers.

An end effector, comprising:

• a staple cartridge comprising a plurality of formable staples;
• an anvil comprising a staple-forming surface;
• and
• a compressible tissue thickness compensator secured intermediate the staple cartridge and the anvil, wherein the tissue thickness compensator is configured to adapt in thickness in response to the thickness of the tissue of a patient and adaptively apply different pressures to the tissue based on the thickness of the tissue captured within the staples, wherein the compressible tissue thickness compensator comprises:
• a first matrix of fibers oriented in a first direction, wherein the first matrix of fibers comprises a first medicament;
• and
• a second matrix of fibers oriented in a second direction, wherein the second matrix of fibers comprises a second medicament that is different than the first medicament, wherein the second direction is different than the first direction, wherein a network of interstices is defined intermediate and among the first matrix and the second matrix, wherein the network of interstices comprises a plurality of pockets, and wherein the plurality of pockets within the network of interstices promotes tissue and cellular ingrowth within the first and second matrices of fibers.