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Polylactide degradation processes after its implantation into the subcutaneous fat of rats were studied by microscopy. After implantation polylactide was encapsulated in connective tissue. If a fragment of polylactide had sharp edges, injuring the tissue, a thick capsule formed with pronounced inflammatory infiltration and sclerosis of adjacent tissues. If the implant had no sharp edges, the capsule was thin and the level of inflammation the minimum. Foreign body giant cells were found in the capsule and near it in all cases. The activity of the inflammatory process gradually reduced over 6 months. The intensity of inflammation sharply increased by the 12th month after implantation, when activity of phagocyte enzyme and deformation by the capsule led to fragmentation or liquefaction of polylactide.

Tissue reactions, accompanying the degradation processes of polylactide (PLA) implants after their placement into the subcutaneous tissue, were studied by the methods of light microscopy in 6 month-old Wag rats (n=24) weighing 180-200 g. It was found that PLA implants became encapsulated by connective tissue. If the implant or its fragment had sharp margins that damaged the tissues, a thick capsule was formed with a distinct inflammatory infiltration and the sclerosis of the surrounding tissues. If the implant had no sharp margins, the capsule was thin, and the activity of inflammation was minimal. In all cases, the giant cells of foreign body type were present in the capsule and next to it. Gradually, during 6 months, the activity of inflammatory process subsided. Inflammation sharply increased 12 months after the implantation, when, as a result of effect of enzymes released by phagocytes and deformation by a capsule, PLA implants were either fragmented or is liquified. PLA-based materials are not totally biodegradable, and may persist in the body for a long time.