Biologic Remodeling after Anterior Cruciate Ligament Reconstruction Using a Collagen Matrix Derived from Demineralized Bone: An Experimental Study in the Goat Model

A matrix of demineralized cortical bone was used to reconstruct the anterior cruciate ligament in the goat model. This graft underwent considerable site-specific remodeling and transformation from a Haversian sys tem at time zero into a ligament-like structure at 1 year. This transformation included new bone formation filling the osseous tunnels and replacing the demineralized matrix, development of a ligament-like transition zone within the graft, and ligamentous collagen orientation with crimp in the intraarticular portion of the graft. One year after surgery, the mean anterior-posterior trans lation in the reconstructed stifle joints at 30 N of tibial loading was 2.1 ± 0.4 mm (±SEM). The mean ultimate force to failure for the reconstructed ligament at 1 year was 474 ± 146 N compared with the time-zero (initial) strength of the matrix of 73 ± 9 N. The cellular repopu lation of the graft had no associated inflammatory cells. The potential clinical significance of these findings in cludes 1) replacement of a collagen matrix with bone within the osseous tunnels, 2) establishment of a more physiologic fibrocartilage transition at the graft inser tion site, 3) the time-zero structural properties of a collagen matrix increasing to more desired values with biologic remodeling, and 4) a sterile biologic allograft with essentially no long-term inflammatory response.