Purpose: Ultrastructural analysis of PT graft for ACL single bundle reconstruction.

Materials and methods: Arthroscopical biopsies for new meniscal lesions at 6-12-24mm-5-10 ys. All cases with IKDC normal/nearly normal and KT2000 excellent/good.

Samples prepared with Karnowsky fixing and urani-lacetate solution. Fibril diameter and transversal area measured by LEICA QUIN in 5 cuts randomly selected for each sample.

Results: 6 months biopsy showed severe P.T. modifications, with a decrease of larger fibrils, substituted with smaller one with plenty of extra cellular matrix. Oxitalan fibers, macrophagic cells and tenocytes were observed. At 12 months compact fascicles of small fibrils (50–60 nm) divided the larger one, similar to a normal tendon. At 24 months graft modifications were increased with wide compact fasciclesvariously oriented. At 5 and 10 years the modifications were similar to those observed at 2 years, with the graft not completely transformed in native ACL structure.

Discussion: The results showed that PT graft used for ACL single bundle reconstruction certainly undergoes a neoligamentization process up to two years. At longer follow-up the foresaw complete remodelling in a normal ACL was not observed. Heterogeneous fibrils presence suggests incomplete ligamentization or its impossible complete realization in single bundle ACL reconstructions.

Shape, surface composition and topography are key factors to achieve post surgery and long-term mechanical stability of endosseous dental titanium implants and to enhance implant osteointegration [1]. Among implant materials, titanium is particularly suitable for orthopaedic and endosseous dental implants on account of its good mechanical properties and biocompatibility [2].

Recent research has studied the morphology of implant surfaces [3,4,5] demonstrating that rough surfaces influence the osteointegration rate which is shorter when a surface is roughened by a sand-blasting technique.

Our in vitro research shows that sand-blasted surfaces positively influence osteoblast metabolic activity by modifying phenotype, surface adhesion levels and proliferation rate [6]. These findings were correlated with in vivo experiments on sheep femur and tibia with implants bearing the same surface characteristics. The implants and surrounding tissue were removed 2, 3 and 12 weeks later and processed for light, electron (scanning and transmission) microscopy study.

A few days after surgery, osteogenic activity was markedly enhanced in the sand-blasted implants which presented more new tissue closely adhering to the implant surface. Three months later there were no major differences in the three samples examined and all showed perfect osteointegration.

Our results suggest that the shorter osteointegration rate obtained with sand-blasted implant surfaces is not only the result of the increased surface area in contact with newly formed bone tissue, but is also correlated to the enhanced osteoblast osteogenesis induced by the concave surfaces geometric design.