ENHANCEMENT OF BONE-FORMATION BY DRAWN POLY(L-LACTIDE)

Poly(L-lactide) (PLLA) was molded into films and rods, and drawn in th e longitudinal direction to endow them with piezoelectricity. The piez oelectric constants of PLLA films increased with the draw ratio and, a fter passing a maximum at a draw ratio around 5, decreased. PLLA sampl es with a draw ratio 5 underwent fibrilization. The PLLA rods were int ramedullarily implanted in the cut tibiae of cats for internal fixatio n up to 8 weeks. Fracture healing was clearly promoted with increased callus formation as the draw ratio of the PLLA rod increased, whereas the undrawn PLLA as well as a polyethylene control rod had no effect o n callus formation, or rather, retarded it. This finding strongly sugg ests that the promotion of fracture healing by fixation with drawn PLL A can be ascribed to the piezoelectric current generated by the strain s accompanying leg movement. (C) 1996 John Wiley & Sons, Inc.