Use of a Magnesium-Based Bone Adhesive for Flexor Tendon-to-Bone Healing

Purpose: Our previous studies in a canine animal model demonstrated that the flexor tendon-to-bone insertion site has a poor capacity to heal. Magnesium-based adhesives have the potential to improve tendon-to-bone healing. Therefore, we hypothesized that magnesium-based bone adhesive (MBA) will improve the tendon-to-bone biomechanical properties initially and in the early period after repair. Methods: Flexor digitorum profundus tendons were injured and repaired into bone tunnels in the distal phalanges of dogs. The bone tunnels were either filled with MBA before completing the repair or left empty (control [CTL]). Histologic appearance, tensile properties, range of motion, and bone density were examined at time zero and 21 days after the repair. Results: There was no histologic evidence of acute inflammation. There appeared to be more mast cells in the MBA group than in the CTL group. Chronic inflammatory infiltrate and fibrosis was slightly higher in the MBA group compared with the CTL group. Tensile properties at time zero were significantly higher in the MBA group compared with the CTL group. However, tensile properties were significantly lower in the MBA group compared with the CTL group at 21 days. Range of motion and bone density were significantly lower in the MBA and CTL groups compared with normal (ie, uninjured) at 21 days; no differences were seen when comparing MBA with CTL. Conclusions: We found that the initial biomechanical properties of flexor tendon-to-bone repairs can be improved with MBA. However, MBA use in vivo led to a decrease in the biomechanical properties of the repair. There was no effect of MBA on bone density or range of motion in the early period after repair. Our histologic analysis suggests that the poor healing in the MBA group may have been due to an allergic response or to increased chronic inflammation resulting from the foreign material.