It's essentially based off the purpose (as well as the guidelines). If you read the descriptions, you'll see the difference.
SuperCoder says:
15777 "Implantation of biologic implant (eg, acellular dermal matrix) for
soft tissue reinforcement (ie, breast, trunk) (List separately in addition to code for primary procedure)"
During a breast or trunk soft–tissue procedure, the provider attaches a biologic implant to reinforce the tissue.
Clinical Responsibility
At the same session as a breast or trunk soft tissue procedure, the provider prepares a biologic implant as required, e.g. hydration, shaping, etc. The provider positions the implant in the proper location and manner to produce a scaffolding effect for tissue reinforcement, and attaches the implant, e.g., by suturing. After the complete procedure is finished, the wound is closed and dressed in the usual manner."
49568 "Implantation of mesh or other prosthesis for open incisional or ventral hernia
repair or mesh for
closure of debridement for necrotizing soft tissue infection (List separately in addition to code for the incisional or ventral hernia repair)"
During the same session in which the provider performs a repair of an open incisional or ventral hernia, a hernia which occurs at the site of a previous surgical incision with protrusion of the intestinal contents. He implants surgical mesh to strengthen the repair of the hernia.
Clinical Responsibility
With the patient already prepped and anesthetized for an open incisional or ventral hernia repair, and after he performs the repair, he then proceeds with the implantation of the mesh. He places the mesh over the weak area of the abdomen. He sews the mesh to the area in a way that the weak area of the abdomen remains below it. He removes and places new mesh in the case of an infected ventral hernia. The provider checks for bleeding, removes any instruments, and finally closes the incision."
https://www.supercoder.com/coding-n...logic-implant-code-with-hernia-109674-article
"...New code +15777 was developed for areas where there's a defect from a tumor resection, or where there's a need for fascia support such as a breast situation -- it's not something you're going to use in conjunction with a hernia repair,"...