Compressible knitted adjuncts with surface features

A stapling assembly for use with a surgical stapler, comprising:

• a cartridge extending from a top surface to a bottom surface that is opposite the top surface, the top surface being a tissue-facing surface with a plurality of extension features projecting therefrom;
• a plurality of staples disposed within the cartridge, the plurality of staples being configured to be deployed into tissue;
• and
• a knitted adjunct configured to be releasably retained on the cartridge such that the adjunct can be attached to tissue by the plurality of staples in the cartridge, the adjunct comprising first and second knitted outer layers formed of fibers, and spacer fibers intertwined with and extending between the first and second knitted outer layers to thereby connect the layers together, the second knitted outer layer having a plurality of preformed recesses defined therein, each recess being configured to receive and engage at least a portion of at least one extension feature of the plurality of extension features to thereby retain the adjunct on the cartridge prior to staple deployment;
• wherein at least one recess of the plurality of preformed recesses has a perimeter defined by a melted portion of the fibers of the second knitted outer layer prior to engagement with the at least a portion of the at least one extension feature of the cartridge.

A stapling assembly for use with a surgical stapler, comprising:

• a cartridge with a plurality of conically shaped projections coupled to and extending outward therefrom and a plurality of recesses formed between adjacent conically shaped projections, each recess having a first maximum diameter;
• a knitted adjunct configured to be releasably retained on the cartridge such that the adjunct can be attached to tissue by a plurality of staples disposed within the cartridge, the knitted adjunct comprising
• a first knitted layer having first fibers, the first knitted layer extending from a first top surface to a first bottom surface with the first top surface defining at least a portion of a tissue-contacting surface of the adjunct,
• a second knitted layer having second fibers, the second knitted layer extending from a second top surface to a second bottom surface with the second top surface defining at least a portion of a cartridge-contacting surface of the adjunct, and
• spacer fibers intertwined with the first and second fibers to connect the first knitted layer with the second knitted layer, wherein portions of the spacer fibers extend between the first and second layers in a generally columnar configuration,
• a plurality of conically shaped recesses extending into and defined within the second knitted layer, each conically shaped recess being configured to receive and engage at least a portion of at least one conically shaped projection of the plurality of conically shaped projections to thereby retain the adjunct on the cartridge prior to staple deployment, and
• a plurality of projections formed between adjacent conically shaped recesses defined within the second knitted layer, each projection being configured to engage at least a portion of one recess of the plurality of recesses of the cartridge, each projection having a second maximum diameter that is greater than the first maximum diameter prior to engagement such that at least a portion of the second fibers at a respective perimeter of the conically shaped recesses are pushed further towards and against a respective conically shaped projection when the adjunct is releasably retained on the cartridge.