抄録
The purpose of this study was to investigate the histological change in a bone tunnel after anterior cruciate ligament (ACL) reconstruction using the bone-patellar tendon-bone graft in a dog model. Eighteen adult mongrel dogs were used. After excision of the ACL, the graft was routed through the bone tunnels and the bone plugs of both ends were fixed with interference fit screws. Four dogs were sacrificed at each of the 4 time periods (one, 3, 6 and 12 weeks) and 2 other unoperated dogs were used to examine the normal insertion sites of the ACL and the patellar tendon. In the histological examination, bone blocks containing the bone tunnels were isolated and decalcified, then, longitudinal sections in line with the bone tunnel were made. The sections were stained with hematoxylin and eosin and safranine-o and observed under light microscopy. Moreover, 4 operated knees (one knee at each of the time periods) and 2 unoperated knees were examined immunohistochemically to clarify the localization of collagen types I and II at the tendon insertion. At the bone-bone interface, incorporation of the bone plug with the host bone was completed at 12 weeks. Structure of the tendon insertion of the grafted patellar tendon, consisting of 4 zones (tendon, uncalcified fibrocartilage, calcified fibrocartilage, and bone), were observed without apparent necrotic or degenerative change for up to 12 weeks.At this original insertion site, presence of cartilaginous matrix and type II collagen was observed throughout the period. Between the tendon and the bone tun-nel, a layer of hypercellular fibrous tissue gradually became mature over time. The dead space in the bone tunnel close to the joint was filled with rather hypocellular fibrous tissue at one week, and the intervening tissue became dense at 12 weeks. The tendon in the bone tunnel underwent the same process of remodeling as its intra-articular portion. Firm incorporation of the bone plug with original insertion and longitudinal fiber orientation of the tendon observed in this study may imply the reestablishment of attachment similar to that of the native ACL. These results suggest a potential advantage of the bone-tendon-bone graft over the tendon graft in terms of graft anchoring in the bone tunnel.
