Objective To investigate and compare the difference between two implants of reconstructing anterior cruciate l igament (ACL) for the early heal ing of implants tunnel interface in terms of biological mechanism. Methods Fiftyfive adult New Zealand rabbits weighing 2.0-2.8 kg were selected. Patellar l igament with tibia-bone block was obtained fromthe left knee joint serving as donor site, right knee joint served as the recipient site of autograft for ACL reconstruction. Thebone block end of implant was bone-bone interface heal ing model, while the l igament end was tendon-bone interface heal ing model. The general condition of rabbits was observed after operation, the gross observation and histology observation were conducted at 2, 4 and 8 weeks after operation (n=5), and biomechanics examination was conducted at 4 and 8 weeks after operation (n=20). Results Rabbits behaved normally after operation. The gross observation indicated that ACL had complete continuity and moderate tension during experiment. Histology observation: most part of bone-bone interface was connected by fibrous tissue, while the tendon-bone interface was mainly filled by granulation tissue 2 weeks after operation; most part of bone-bone interface was bone union, and there were osteogenesis reaction and large quantity of fibroblasts in the tendonbone interface 4 weeks after operation; complete bone union was evident in bone-bone interface, and the appearance of Sharpey fibers and the formation of indirect insertion occured in part of tendon-bone interface 8 weeks after operation. Biomechanics observation: the pull-out rate for tendon-bone interface and bone-bone interface 4 weeks after operation was 85% and 15%, respectively; while it was 95% and 5% 8 weeks after operation, respectively; indicating there was a significant difference between two groups (P lt; 0.001). Conclusion In the early stage after ACL reconstruction, bone-bone interface is better than tendonbone interface in terms of intensity and speed of heal ing.
Objective To explore the situation of tendon-bone heal ing when allogenic tendon graft is wrapped with autologous periosteum around the tendon in rabbits. Methods Twenty healthy New Zealand white rabbits with the age of 4-5 months were used in the experiment, weighing 2.5-3.0 kg. One-side posterior l imb was selected randomly as the test, and thecontralateral l imb was served as the control at the same time. The allogenic tendon graft was designed as a tendon-bone model in the proximal tibial metaphysis of rabbits. The portion of tendon in the bone tunnel was wrapped with autologous periosteal graft in which the cambium layer was facing the bone tunnel in the experimental group, while the portion of tendon in the bone tunnel was not wrapped with autologous periosteal graft in the control group. The histologic examination of the tendon-bone interface (n=2) and the biomechanical test for maximal pullout load (n=8) were conducted 4 and 8 weeks after operation, respec tively. Results All specimens were observed with naked eyes 4 and 8 weeks after the operation. Many new bones around bone tunnel outlet were seen in the experimental group, while a few or few new bones were seen in the control group. Four weeks after operation, histological observation showed there were a lot of prol iferative mesenchymal cells in the periosteal germinal layer in the experimental group and conspicuous membrane bone formation was obvious. The arrangement of massive osteoblasts around newborn bone trabecula was similar to pal isade. The newborn bone trabecula was l inked with the periosteum. Some loose connective tissues and few newborn bones between the tendon graft and the bone tunnel were seen in the control group, and the connection of them was loose. Eight weeks after operation, the connection between the tendon graft and the bone tunnel was tight and no gap existed in the experimental group. The number of newborn bones was large and their arrangement was relatively regular. The tidemark l ine was seen between the tendon graft and the bone tunnel, which was similar to normal tendon-bone interface. The prol iferation of fibroblast was active in the periosteum, and there were many fibrous joints betweenthe periosteum and the tendon graft. Partial bone formation was seen between the tendon graft and the bone tunnel in thecontrol group, with disorderly arrangement, and there were many collagen fibrous joints between the tendon graft and the bone tunnel. Four and 8 weeks after operation, the pullout or pull and break loads of the experimental group were (35.03 ± 1.21) N/ cm and (42.36 ± 1.31) N/cm, respectively, and those of the control group were (26.14 ± 6.13) N/cm and (31.63 ± 6.87) N/ cm, respectively. There was significant difference between the two groups (P lt; 0.05). Conclusion The transplantation of autologous periosteum graft wrapping around allogenic tendon graft may shorten the time of osteochondral ossification between the tendon graft and the bone tunnel, improve heal ing strength and promote tendon-bone heal ing in the bone tunnel in rabbits.