Augmentation of tendon-to-bone healing with a magnesium-based bone adhesive

Background: Healing of an anterior cruciate ligament graft in a bone tunnel occurs by formation of fibrous scar tissue, which is weaker than the normal fibrocartilaginous insertion. Hypothesis: We hypothesized that a magnesium-based bone adhesive would improve tendon-to-bone healing in a rabbit anterior cruciate ligament reconstruction model. Study Design: Controlled laboratory study. Methods: Thirty-five New Zealand White rabbits underwent bilateral anterior cruciate ligament reconstructions with semitendinosus autografts. A total of 12.5 g of bone adhesive was placed in the intraosseous tunnel around the graft in one limb, while the tunnels in the contralateral limb received no implant. Sixteen animals each were sacrificed at 3 weeks and at 6 weeks (12 biomechanical testing/4 histology). Outcomes included semiquantitative histologic analyses for new cartilage formation and fibrous tissue formation in the tendon-bone interface, microcomputed tomography to quantify new bone formation along the bone tunnel, and biomechanical testing of load-to-failure and stiffness. Three animals were sacrificed at time 0 to confirm adequate tunnel fill with the bone adhesive on microcomputed tomography. Results: All specimens had adequate tunnel fill with the bone adhesive at time 0. Application of the bone adhesive resulted in more cartilage formation and less fibrous tissue formation at the tendon-bone interface at 6 weeks compared with controls (P <.05). There was significantly more bone formation in the tibia of the treated limbs at 6 weeks (P =.01). The load-to-failure was significantly higher in the treated group at 6 weeks (71.8 ± 31.8 N vs 43.4 ± 14.8 N; P =.04). There were no differences in stiffness at either time point, and there were no differences at 3 weeks in any outcome variable. Conclusion: The magnesium-based bone adhesive improves tendon-to-bone healing based on histologic and biomechanical testing at 6 weeks in a rabbit model of anterior cruciate ligament reconstruction. Clinical Relevance: Further studies are needed to investigate the clinical potential of this bone adhesive to enhance healing and decrease recovery time in soft-tissue ligament reconstruction.