A bone graft substitute includes a porous matrix at least partially covered by a reinforcing outer layer. The porous matrix may be a collagen-ceramic composite, and the reinforcing outer layer may be formed from highly cross-linked collagen. The implant may also include one or more reinforcement ribs, which may be made from calcium phosphate or dense collagen. In addition, the bone graft substitute preferably includes an effective amount of a bioactive agent, such as BMP-2, rhBMP-2, or functional fragments thereof. The bioactive agent is preferably disposed within the porous matrix.