The burst phenomenon, an animal model simulating the long-term tissue response on PLLA interlocking nails.

In this in vivo study, low-molecular-weight as-polymerized PLLA powder was placed in the medullary cavity of a porcine femur in order to study the tissue reaction on predegradated PLLA. An attempt was made to simulate the long-term degradation of a large PLLA implant. This phase can be characterized by the release of PLLA particles and acid compounds from a heterogeneously degrading PLLA implant into the surrounding tissues. The clinical consequences and tissue response were studied. The clinical recovery of the experimental animals was favorable. No signs of clinical inflammation could be detected during the eight-week follow-up period. Histological analysis of the bone/PLLA interface showed signs of a mild inflammatory tissue response.