During rotator cuff repair surgery, fixation and incorporation of ruptured rotator cuff tendon into the bone is a major concern. The repair usually fails at the tendon-bone interface, especially in cases where the tear is massive. The periosteum contains multipotent stem cells that have the potential to differentiate into osteogenic and chondrogenic tissues, which may restore the original structure at the tendon-bone interface, fibrocartilage. In this study, we investigated the effect of periosteum on the healing of the infraspinatus tendon and bone using a clinically relevant rabbit model of rotator cuff tear. We used 36 skeletally mature New Zealand white rabbits in the study. The infraspinatus tendon at right limb was detached from greater tuberosity, and a periosteal flap taken from the proximal tibia was sutured onto the torn end of tendon. The contralateral limb, which was used as a control, received the same treatment without a periosteum. The rabbits were sacrificed at 4, 8, and 12 weeks, and the tendon-bone interface was put to histological exam and the biomechanical testing to assess strength of tendon-bone interface. Histological analysis of the tendon-bone interface revealed that the periosteum formed a fibrous layer over the interface between tendon and bone. At 4 weeks, fibrotic tissue showed progressive integration over the interface between cuff tendon and bone. At 8 weeks, progressive formation of fibrovascular tissue and fibrocartilage was observed between tendon and bone. At 12 weeks, extensive formation of fibrocartilage and bone was noted in the interface. The significant increase of failure load with time indicated a progressive increase in the tendon-bone incorporation strength. At 4 weeks after operation, the attachment strength of the limbs with the periosteum treated was higher than that of the control limbs; however, this difference was not statistically significant. At 8 and 12 weeks, a statistically significant increase was noted in the attachment strength of the limb treated with the periosteum. Most specimens failed at the tendon-bone interface (18/20). In the treatment of a torn rotator cuff in rabbit model, improved healing process with greater attachment strength could be achieved by suturing the periosteum between the end of tendon and the bone trough. Histological examination revealed that the cambium layer of the periosteum could serve as a potent interface layer and become progressively mature and organized during the healing process, resulting in fibrocartilage formation and the subsequent integration of the disrupted tendon into the bone. Biomechanical testing revealed a progressive increase in the attachment strength with time indicating the progressive tendon-bone incorporation. When performing rotator cuff repair in a large or massive tear, a periosteal flap can be sutured onto the torn end of tendon to enhance tendon-bone healing.
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