Enveloping the tendon graft with periosteum to enhance tendon-bone healing in a bone tunnel: A biomechanical and histologic study in rabbits

Purpose: Fixing and incorporating the tendon graft within the bone tunnel is a major concern when using grafts for ligament reconstruction. The periosteum contains multipotent stem cells and has the potential to form osteogenic and chondrogenic tissues. This study uses histologic and biomechanical analyses to examine the effect of periosteum on tendon-bone healing within a bone tunnel. Type of Study: Experimental study in an animal model. Methods: In this study, 36 adult New Zealand White rabbits were used. The long digitorum extensor tendon was transplanted into a bone tunnel of the proximal tibia. The periosteum from the proximal tibia was sutured on the surface of the tendon portion. The tendon was pulled through a drill-hole in the proximal tibia and attached to the medial aspect of the tibia. Histologic examination of the tendon-bone interface and biomechanical test for maximal pullout load were evaluated at 4, 8, and 12 weeks after operation. Results: Histologic analysis of the tendon-bone interface showed a fibrous layer formed between the tendon and the bone by the periosteum. This layer became progressively integrated with the tendon and bone surface during the healing process. At 4 weeks, the cancellous bone lining in the bone tunnel was interdigitated with the fibrous interface tissue. At 8 weeks, progressive new bone grew into the interface fibrous layer. At 12 weeks, collagen fibers anchored to the bone and organization with fibrocartilage formation developed between the tendon and bone. Biomechanical testing revealed higher maximal pullout strength in the periosteum-enveloped group at all time points, with a statistically significant difference at 8 and 12 weeks. The periosteum-treated group had a higher interface strength-to-length ratio and significant increase at 8 weeks and 12 weeks. Conclusions: The histologic and biomechanical studies demonstrated that, if periosteum was sutured on the tendon that was transplanted within a bone tunnel, it resulted in a superior healing process and better healed strength. When doing ligament reconstruction with a tendon graft, the periosteum can be sutured to the graft to enhance tendon-bone healing.