[Resorbable osteosynthesis rods. An experimental study of the biomechanics and degradation of various rods of polyglycolide and poly (-L-lactide)].

Six different polyglycolide and poly(-L-lactide) rods were tested biomechanically: native, in vitro and in vivo. They were Biofix-C and Biofix-CG rods and 4 poly(-L-lactide) rods with a molecular weight between 70,000 and 700,000. Their flexual strength and elasticity module were determined by the 3-point flexion test. A total of 70 pins were implanted in the soft tissue and intramedullary to splint tibial osteotomies of 30 rabbits. The Biofix rods' flexural strength was high. There was no difference due to coating (346 to 402 N/mm2). In vitro experiments showed a rapid loss strength by 75 and 90%, equivalent to 2 to 3 weeks' implantation. The initial strength of the lactide pins was about 60% lower than that of the polyglycolid rods. The stability of the former after implantation decreased at a lower rate, with 25% of the initial strength being retained after 14 weeks. The histological findings were commensurate with the loss of flexural strength.