Periosteum-Enveloping of the Tendon to Enhance Tendon-Bone Healing in the Bone Tunnel-Histologic Studies in Three Experimental Rabbit Models

Successful ligament reconstruction with tendon graft requires solid healing of the tendon graft in the bone tunnels. Periosteum contains multipotent mesodermal cells and has the capacity to form osteogenic tissue. In this study, we will present the effect of periosteum-enveloping tendon on the tendon-bone healing in 3 different experimental models in rabbits: 1) wrapping on a tendon surface; 2) inserted within an extra-articular tibial bone tunnel, and 3) reconstructed in the intra-articular femoral and tibial bone tunnels. Histology for the tendon-periosteum and tendon-bone interfaces were evaluated at 4, 8, 12 weeks after operation. In tendon surface groups, new bone formation was found on the tendon surface by passing through a cartilage state from transplanted periosteum. In extraarticular groups, an interface fibrous layer formed by periosteum between the tendon and the bone became progressive integrated during the healing process. The cancellous bone lining in the bone tunnel had been interdigitated with the fibrous interface tissue. Collagen fiber-bone anchorage and organization with fibrocartilage formation developed between tendon and bone. In intra-articular groups, a fibrovascular interface tissue formed by periosteum tissue between the tendon and bone with progressive mineralization and maturation. The interface fibrous layer became integrated and mixed together with tendon and bone lining and unable to identify the margin. Progressive collagen fiber growing into bone through fibrocartilage formation appeared at later period. Our results showed that where the cambium layer of periosteum was present, there was a definite tendency towards the neoformation of fibrocartilage and bone. Periosteum had the ability to augment bone ingrowth into tendon and to induce ossification, fibrocartilage and bone formation not only in the free tendon but also in the extra-articular and intra-articular bone tunnels.