Studies on Bone Formation by Resorbable and Piezoelectric Polylactide

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Electromagnetic regenerators have been clinically used for enhancement of callus formation. In addition, metallic wires and plates have been used in orthopaedic surgery for fixation of fractured bones. The objective of this work was to accumulate scientific information for wider clinical applications of poly(L-lactide(PLLA) which can generate electricity upon being mechanically strained. PLLA is at the same time resorbed in the body when implanted.The following findings were obtained by this work. 1) Changes of synthetic conditions of PLLA produced PLLA sheet, plate, and fiber with a variety of mechanical properties and resorption kinetics. 2) Incorporation of cell growth factors such as bFGF and TGF-beta in resorbable carriers and subsequent implantation resulted in ectopic bone regeneration as well as in bone formation in native bone tissues. 3) Implantation of a magnetized metal block made from samarium cobalt in the rat femur promoted bone formation, in marked contrast with a non-magnetized samarium cobalt block of the same size. 4) Combination of PLLA fibers and resorbable poIy(epsilon-capro1actone) fibers could readily fix a fractured bone, similar to the conventional metal wire. The fixation of a fractured bone with the resorbable fiber combination could be carried out by heating the po1y(epsilon-capro1actone) fibers above the melting temperature. 5) PLLA fibers could generate electricity when they were twisted and then extended to the fiber direction. This indicates that the assemble of twisted PLLA fibers acquired a piezoelectric property in addition to resorbability in the body.