a vertebroplastic cementitious composition includes a solid phase including portland cement and a biocompatible additive which is a plasticizer and a hardening accelerant , wherein the amount of additive is between about 1 % and about 15 % by weight relative to the portland cement ; and an aqueous liquid phase , wherein the ratio of the solid phase to the liquid phase is between about 3 g / ml and about 6 g / ml . methods of forming such compositions , treatment methods using such compositions and cementitious implants including such compositions are also described .