Medical device made of biomaterial, for implant-based breast reconstruction, having a flat original shape of plane geometry, with sections, which sutured together define the front part, lateral, upper and lower of a box element, at least one of the aforesaid sections having at least one appendix adapted to define the rear part of the box element, said box element being adapted to wrap and contain integrally a breast prosthesis, said box element being configured to be interposed between the subcutaneous layer and the pectoralis major muscle and being suturable to the latter.
