Repair of Cranial Defects in Rabbits with 3D-Printed Hydroxyapatite/Polylactic Acid Composites

Abstract

Objective. The safety and efficacy of three-dimensional- (3D-) printed hydroxyapatite/polylactic acid (HA-PLA) composites in repairing cranial defects were evaluated in a rabbit experimental model. Methods. Twelve New Zealand rabbits were selected as experimental subjects. Two holes (A and B), each with a diameter of approximately 1 cm, were made in the cranium of each rabbit. Hole A served as the experimental manipulation, and hole B served as the control manipulation. A 3D-printed HA-PLA composite was used for placement onto hole A, whereas autologous bone powder was used for placement onto hole B. Samples from the experimental holes and the control holes were collected at 30 and 90 days after surgery. The obtained materials were examined in terms of their morphologies and histopathologies and were also subjected to simultaneous hardness tests. Results. Both the 3D-printed HA-PLA composite and autologous bone powder were able to repair and fill the cranial defects at 30 days and 90 days after surgery. At 30 days after surgery, the microhardness of the area repaired by the HA-PLA composite was lower than that of the area repaired by autogenous bone powder ( $p<0.01$ ), but neither of these treatments reached the hardness of normal bone at this time ( $p<0.01$ ). At 90 days after surgery, there was no statistically significant difference in the microhardness of the repaired area from the 3D-printed HA-PLA composite compared with that of the repaired area from autologous bone powder ( $p>0.05$ ), and there was no statistically significant difference in the hardness of the two repaired areas compared with that of the normal bone ( $p>0.05$ ). Hematoxylin-eosin staining showed that bone cells in the HA-PLA material in the experimental group grew and were arranged in an orderly manner. Bone trabeculae and marrow cavities were formed on the pore surface and inside of the HA-PLA scaffold, and the arrangement of bone trabeculae was regular. Conclusion. 3D-printed HA-PLA composites can induce bone regeneration, are biocompatible, have the same strength as autologous bone powder, are able to degrade, and are ultimately safe and effective for repairing cranial defects in rabbits. However, further research is needed to determine the feasibility of 3D-printed HA-PLA composites in human cranioplasty.