Weak link of tendon-bone healing and a control experiment to promote healing.

Objective: This study aims to observe the mechanical weak point and histological features of tendon-bone interface after anterior cruciate ligament reconstructive surgery and to explore the tendon-bone healing effects of the platelet-rich gel (PRG) + deproteinized bone (DPB) compound.

Methods: A total of 48 New Zealand white rabbits were randomly divided into normal group, model (without embedding), experimental (embedded with the PRG + DPB compound), and control (embedded with DPB) groups. The rabbits were executed at 2, 4, 8, and 12 weeks after the operation. Then, micro-computed tomography scan and uniaxial tensile test were conducted. The fractured specimens were subjected to histological observation.

Results: At 4, 8, and 12 weeks after the operation, the bone density of the tendon-bone bound section of the experimental group was higher than that of the other groups (P < 0.05). At 4 and 8 weeks, the maximum tensile load of the experimental group was obviously higher than that of the control and model groups (P < 0.05). Histological observation indicated that the tendon-bone interface in the experimental group had more cartilage and bone tissue growing toward the internal tendon, but the fracture layer mainly occurred in the non-ankylosed part.

Conclusion: The mechanical weak point of the early tendon-bone interface was in the immature fibrous tissue. The PRG + DPB compound can effectively trigger tendon-bone healing by promoting the maturation and ossification of the tendon-bone tissue. This compound improved the tensile strength of the healing interface and reduced bone tunnel enlargement.