New insights on the degradation of bioresorbable polymeric devices based on lactic and glycolic acids.

This contribution recalls some recent advances in the understanding of the mechanisms of degradation of bioresorbable polymers of the poly(beta-hydroxy acid) type derived from lactic and glycolic acids, which are receiving increasing interest for their potential for osteosynthesis. First, the various polymers are introduced and the field of applications is delimited. It is confirmed that degradation proceeds faster in amorphous domains than in crystallites. It is also shown that degradation proceeds faster in the center than at the surface, although this feature is not predominant in the case of semicrystalline lactic acid stereocopolymers. Of special interest are the findings that quenched compounds can crystallize at body temperature during degradation and that highly crystalline degradation residues can remain in situ for several years. Data show that osteosynthesis with bioresorbable plastics might become a reality for reasonably loaded bones, provided the peculiarities of polymers are taken into account by surgeons.