The effects of piezoelectric poly-L-lactic acid films in promoting ossification in vivo.

Uniaxially drawn poly-L-lactic acid (PLLA) films with piezoelectric properties were inserted onto the periosteum of rabbit tibiae, and the effect of the films in promoting ossification was investigated. We also evaluated the optimum method for PLLA film insertion to promote ossification, by comparing three different types of PLLA films which differed from each other in terms of the direction of their molecular orientation. Furthermore, the course of ossification following the film insertion was observed histologically. Drawn PLLA films promoted ossification to a greater extent than undrawn PLLA film. The effect of drawn PLLA films in promoting ossification was greatest when a shearing stress was applied at 45 degrees to the axis of orientation. The newly formed osteoid was observed at 1 week, and matured over 6 to 8 weeks following insertion. The insertion of piezoelectric PLLA films can promote ossification through their piezoelectric effect, and this seems to be clinically applicable.