Aim: The purpose of this paper was to describe the biological reaction imposed by a prosthetic ligament.

Materials-Methods: Polyester-carbon synthetic matrices were implanted into 29 rabbits. The implants were transected centrally and reconstructed with resorbable suture material. At regular intervals from 4th day to 29 weeks, tissue samples from the ingrown implants were obtained for histology and mechanical testing. Light microscopy, DNA cytometry, immunohistochemical analysis of the collagen types, transmission and scanning electron microscopy were carried out. Ultimate tensile strength (UTL), elongation to failure (EF) and structural stiffness (SS) were determined at intervals of 8, 16 and 29 weeks.

Results: The ingrowth of tissue into the scaffold provided a significant increase in tensile strength, which improved with time. The UTL significantly increased from 18.86 N ±14.69 at 8 weeks to 51.4 N ±14.64 at 29 weeks. Light microscopy showed no infl ammation or foreign body reaction. At 4th day the first fibroblast cells settled on the matrix. The DNA cytometry showed an increase of the number of the fibroblast cell mitoses up to 16 days. After 2 weeks a mesh of connective tissue was formed around the scaffold, but the number of fibroblast cells remained constant. At 4 weeks the connective tissue started to infiltrate in between the artificial fibres. Type I, III and V collagens were identified. Electron microscopically the collagen weave was irregular with a mean fibril diameter of 28.4 ± 5.2 nm of a monophasic distribution. Collagen type I accumulated progressively and more and more dense collagenous fascicles appeared in the mesh in the proximity of the artificial fibres.

Conclusion: The subcutaneous tissue may act as a bio-reactor and the skin fibroblast seeding of a synthetic matrix appears to be transformed a dense connective tissue during the first 4 weeks, providing tensile strength improvement to the tissue envelope with time.