An implant for filling a cavity created by an excisional procedure includes first and second portions. The first portion may include a first collagenous matrix that defines a first selected crosslinking density and the second portion may include a second collagenous matrix that defines a second selected cross-linking density that is different than the first cross-linking density. The first and second cross-linking densities may be selected so as to cause the first and second portions to swell in such a manner that the implant swells into a size and a shape that is similar to the predetermined size and shape of the cavity when the implant is implanted. An aqueous solution may be added to the cavity if the cavity is not sufficiently aqueous to cause the implant to swell.