Effects of various adjuvants (lactic acid, glycerol, and chitosan) on the injectability of a calcium phosphate cement

Calcium phosphate cements are well-known orthopedic materials for filling b one. Various formulations are proposed, The current challenge is to place t he material in the surgical site by methods as least invasive as possible. One approach consists of making the cement injectable by incorporation of v arious adjuvants. However, the requirement properties of the cement must be preserved: setting times suited to a convenient delay with surgical interv ention, limited disintegration in aqueous medium, and sufficient mechanical resistance. Various additives were studied: in particular, lactic acid, gl ycerol, chitosan, and sodium glycerophosphate. Injectability, setting time, disintegration, and toughness after 10 days were followed in vitro. Glycer ol greatly improved injectability and increased setting time, but decreased mechanical properties. Lactic acid reduced setting time, increased toughne ss of the material, but limited the dissolution rate. After injection, the cement did not present any disintegration. The effects lactic acid were cor related with the formation of calcium complex. Its association with sodium glycerophosphate is particularly interesting. Chitosan alone improved injec tability, increased setting time, and limited the evolution of the cement b y maintaining the OCP phase. Only slight disintegration was observed. These first results show that is possible to transform the cement into an inject able paste by addition of adjuvants without fundamentally modifying the che mical reactions occurring during setting and hardening. (Bone 25:31S-34S; 1 999) (C) 1999 by Elsevier Science Inc, All rights reserved.