Experimental surgery was performed on the dog to compare the behavior of fresh autografts with freeze-stored allografts of the anterior cruciate ligament (ACL). In both cases, drill holes were made at the ACL insertion sites with a cannulated bit and the ligament with a plug ofbone attached to each end was extracted with the aid of a guide wire. Prior to implantation, autografts were inmersed in a saline solution for a few minutes. Allografts deeply frozen to -80 °C with liquid nitrogen were quickly thawed before surgery. At implantation, the bone plugs at the ends of the ligament were firmly anchored with 6,5 mm. cancellous bone screws, so inmobilization of the animals was not necessary. Animals were killed at 3, 6, 12, 24 and 36 week after surgery. To study graft vascularity the tissue transparency technique developed by Spalteholz was employed. Both type of grafts underwent the same biological reconstruction process. Indifferentiated mesenchymal cells and capillar buds from the host tissues invaded the implant. Through a mechanism of creeping substitution induced by fibroblastic and osteoblastic differentiation, the grafts gradually took the apparence of normal, well-vascularized ACL. The remodeling process reached the innermost zones of the autografts in 12 weeks and the allografts in 24 weeks. Both type of groups showed a normal mature appearance 36 weeks after surgery. There were no signs of inmunological rejection. In our opinion, the ideal substitution for repair of ACL injurie could be an allograft of the same ligament, removed with bone attached to each end.

Experimental surgery was performed on the dog to compare the behavior of fresh autografts with freeze-stored allografts of the anterior cruciate ligament (ACL). In both cases, drill holes were made at the ACL insertion sites with a cannulated bit and the ligament with a plug ofbone attached to each end was extracted with the aid of a guide wire. Prior to implantation, autografts were inmersed in a saline solution for a few minutes. Allografts deeply frozen to -80 °C with liquid nitrogen were quickly thawed before surgery. At implantation, the bone plugs at the ends of the ligament were firmly anchored with 6,5 mm. cancellous bone screws, so inmobilization of the animals was not necessary. Animals were killed at 3, 6, 12, 24 and 36 week after surgery. To study graft vascularity the tissue transparency technique developed by Spalteholz was employed. Both type of grafts underwent the same biological reconstruction process. Indifferentiated mesenchymal cells and capillar buds from the host tissues invaded the implant. Through a mechanism of creeping substitution induced by fibroblastic and osteoblastic differentiation, the grafts gradually took the apparence of normal, well-vascularized ACL. The remodeling process reached the innermost zones of the autografts in 12 weeks and the allografts in 24 weeks. Both type of groups showed a normal mature appearance 36 weeks after surgery. There were no signs of inmunological rejection. In our opinion, the ideal substitution for repair of ACL injurie could be an allograft of the same ligament, removed with bone attached to each end.