A multilayer ingrowth matrix is constructed within well-defined porosity
of a prosthetic material. The matrix consists of either proteinaceous or
synthetic layers or gradients, or a combination of proteinaceous and
synthetic layers or gradients. Each layer within the matrix is designed
to achieve a specific function, such as facilitation of ingrowth of a
particular cell type or release of a particular growth factor. The
well-defined porosity is in the form of either helically oriented,
interconnected transmural ingrowth channels, or a porous wall structure
containing uniformly shaped pores (i.e. voids) in a very narrow size
range, or a combination of channels and pores. This invention allows for
uninterrupted ingrowth of connective tissue into walls of a synthetic
graft prosthesis made from the prosthetic material. Furthermore, this
invention can produce small diameter prostheses having an internal
diameter of 6 mm or less.