biodegradable , porous , polymeric implant material provides substantially continuous release of bioactive agent during in vivo use . bioactive agent is initially released in amounts that are less than degradation rate of polymer , thereby promoting migration of cells into material . later larger amounts of bioactive agent are released , thereby promoting differentiation of cells . method of making material includes steps of applying vacuum temperature and consession to form pores . implant material may be adapted for one phase implant or for two phase layered implant .