Introduction Recent clinical and biomechanical studies have demonstrated better results with double-bundle anterior cruciate ligament (ACL) reconstruction compared to single-bundle reconstruction. Little is known about the healing process after double bundle ACL reconstruction and nothing in case of failure. The purpose of this study was to analyze ACL double bundle graft remodeling process by evaluation of cell population and quantification of collagen fibril profiles in four traumatic failed grafts. These morphological appearances were then correlated to normal tendon allograft and ACL. The hypothesis of the study was that a different maturation process occurs between the two bundles. Materials and Methods Four ruptured ACL reconstructed remnants were obtained from 4 patients undergoing revision of the ACL surgery. In all cases the graft used for the primary reconstruction was tibialis anterior allograft. In 2 cases, both bundles were torn, with only the AM bundle in the remaining 2 cases. The average time between the primary surgery and the second trauma was 11 (9-14) months. Three intact ligaments (positive control group) was obtained from 3 patients (average age 64.3 years; 62-66) undergoing total knee arthroplasty. Biopsy specimens of 3 tibialis anterior tendon allografts were used as negative control group. Each biopsy was sheared longitudinally in two identical parts. The first sample was stained with Masson Trichrome and the cellular density of each specimen was estimated with light microscopy by counting the number of cells per mm2. The second sample was analyzed using transmission electron microscopy to measure the diameter of the collagen fibrils, the density (number of collagen fibrils per square micrometer), and the percentage area of collagen fibrils (% area occupied by total collagen fibrils relative to the cross-sectional area). Results There was a statistical difference between AM and PL groups and AM and allografts groups for all the variables analyzed (p