Degradation characteristics of PLLA-PGA bone fixation devices

Parietal craniotomies of the mature rabbit skull were repositioned and fixed with resorbable plate and screws made of LactoSorb (Walter Lorenz Surgical, Jacksonville, FL) poly L-lactic acid (PLLA) and polyglycolic acid (PGA) in 20 mature rabbits. Changes in the resorbable devices as well as at the tissue-implant interface were evaluated at 2, 6, 9, and 12 months postoperatively. At 2 months, no change in the size of the implants was seen with a noninflammatory layer of surrounding fibrous tissue and intense birefringence of the screws. At 6 months, substantial loss of implant size had occurred, accompanied by fibrovascular and a macrophage cellular infiltrate. At 9 months, more than 95% of the implant was resorbed, with a small amount remaining in the screw hole. Other than macrophages within the remaining material, very few giant cells were seen. By 1 year, no evidence of birefringent macromolecular polymer debris could be found. No contraindications for the clinical use of this specific PLLA-PGA copolyer could be found when implanted on craniofacial bone surface.