Cross-linked hyaluronic acid enriched with amino acids used for bone filler defect: a histological and histomorphometry study in rabbit tibiae

Background: Today we have numerous bone substitutes with different chemical and physical properties and with different sizes, quantities and porosity. The biomaterials are available in particles, gel, blocks, and cement pastes. The aim of this study is to evaluate the influence of hyaluronic acid gel enriched with amino acids on bone healing in a rabbit artificial bone defect. Methods: Six rabbits were used in this study, for each tibia, a 3 mm bilateral non critical-size circular defect was produced. The drilling was performed on cortical bone with no invasion of the medullary component. The bone defect was filled with Hyaluronic acid enriched with amino acid while the second defect was used as empty control. The HA filling enriched with amino acid was positioned into the bone defect with no pushing into the medullary space. No covering membranes were applied on top of the bone defect. The rabbits were euthanized by an intravenous pentobarbital overdose after 4 weeks and a total of 36 biopsies (6 for each group) were retrieved. The samples were processed to obtain histological sections. Results: In the control sites, newly formed tissues in the defects were characterized by 25 ± 3 % of lamellar bone, 25 ± 1 % of woven bone and 50 ± 3 % of medullary spaces. The osteoblast count in the bone defect was 15±3 and 1 ± 2 vessel. In the test sites the morphometry findings were characterized by 28 ± 3 % of lamellar bone, 73 ± 1 % of woven bone and 0 % of marrow spaces. The osteoblast and vessel count was 87±3 and 6 ± 2 vessels per field. Statistical differences were found for the number of osteoblasts, vessels and new bone. (p < 0.05). Conclusions: The efficacy of the present investigation revealed that HA increases the new vessel and bone formation and induces a more rapid healing in rabbit bone defects if compared to the control.