[Effects of autologous periosteum wrapping allogenic tendon graft on tendon-bone healing inside a bone tunnel in rabbits].

Objective: To explore the situation of tendon-bone healing 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 limb was selected randomly as the test, and the contralateral limb 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, respectively.

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 proliferative 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 palisade. The newborn bone trabecula was linked 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 line was seen between the tendon graft and the bone tunnel, which was similar to normal tendon-bone interface. The proliferation of fibroblast was active in the periosteum, and there were many fibrous joints between the periosteum and the tendon graft. Partial bone formation was seen between the tendon graft and the bone tunnel in the control 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 < 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 healing strength and promote tendon-bone healing in the bone tunnel in rabbits.