USE OF A FIBRILLAR POLYLACTIC ACID HOMOPOLYMER IN SHEEP CRANIAL DEFECTS

Guided tissue regeneration has been shown to permit osteoconduction in otherwise nonhealing cranial defects. The relative importance of prev enting the prolapse of soft tissue versus the infiltration of individu al connective tissue cells has not been determined. A fibrillar form o f polylactic acid (PLA) was tested in 13-mm-diameter defects in the pa rietal bones of 12 sheep. The polymer was hypothesized to prevent the prolapse of dura and periosteum but allow entrance of individual cells . Control defects in the same sheep were either filed with autogenous bone shavings or left unfilled. The animals were killed at times rangi ng from 6 to 25 weeks and the defects examined grossly, radiologically , and histologically. The autogenous bone-filled defects were spanned by trabeculated bone by 6 weeks. The unfilled defects demonstrated pro lapse of soft tissues into the defect; however, progressive centripeta l bone growth was evident The fibrillar PLA-filled defects were occupi ed by a full-thickness mixture of fibrous tissue interspersed with PLA . After 19 weeks, small ''fingers'' of bone were seen to minimally inf iltrate the fibrous tissue. Although separation of the dura and perios teum was maintained by the fibrillar PLA, invasion of fibrous tissue r estricted osteoconduction.