Preparation And Performance Of Medical Polymer/Hydroxyapatite Composite And Its Rapid Manufacturing Used For Bone Implant

Hydroxyapatite(HA) has a good bone formation and bone conduction, The brittleness and the low loading tolerance,however, have largely limited its application in bone tissue engineering; Polymethyl methacrylate(PMMA) has good mechanical properties, but its low fatigue resistance could not go unnoticed; Poly lactic acid/glycolic acid copolymer(PLGA) with special biodegradation of matching, has good tensile properties. In order to get a kind of bone implant replacement material with good biocompatibility and mechanical strength, hybridization of these three raw materials was urgently needed which could effectively combined the advantages of them.PLGA was prepared through melt polymerization in the first step, In-situ polymerization and in-situ settling out processing was then carried out to realize the simultaneous synthesis of HA particles and the polymerization of polymer. The HA particles was modified by lecithin, grafted onto the polymer molecular chain by the surface chemical modification. As a result, HA/PLGA/PMMA composites with different HA content were obtained. Thermal stability, mechanical properties and biocompatibility of the as-prepared composites were then tested by characterization. Reconstruction of the 3d geometric model of the right proximal humerus was realized by importing the CT data into the Mimics medical image three-dimensional reconstruction software. Taking advantage of software compatibility between Mimics and ANSYS, the precise three-dimensional finite element mesh model of the right proximal humerus was created. Stress distribution and displacement distribution are simulated by setting constraints conditions and applied load. Finally, the right proximal humerus entity model was manufactured by the 3-D printer with the HA/PMMA/PLGA composite as its raw material.Experimental results showed that the characteristic peak of in situ settling out HA crystal was the same with pure HA. The HA interacted with PLGA/PMMA matrix by hydrogen bonding, which could make HA well dispersed in the composite. The PLGA/PMMA/HA composite showed excellent thermal stability, mechanical strength and biocompatibility. When the content of HA was set at 15 %, the tensile strength and impact strength of HA/PMMA/PLGA composites reached to 34.8 MPa and 0.81 J/cm2, respectively. The stability experiment showed that dissolution rate of Ca2+ ions and PO43- ions in the simulated body fluid achieved only 0.58×10-4 mol/g?L and 0.34×10-4 mol/g?L in 5 weeks, indicating a stable combination between HA and PMMA matrix and excellent stability of the composite in body fluids. The cell proliferation experiment showed that cells with normal appearances on the surface of the composite significantly increased and the OD value achieved 0.79, when MG-63 cells cultivated with the composite for 21 days. Indicating the good biocompatibility of the composite. The performance tests showed that the mechanical properties and biocompatibility of the composite could meet the demand of bone implants which laid the material foundation of the rapid manufacture. Reconstructed 3d geometric model of right proximal humeruthe was imported from Mimics into ANSYS. Simulation of the stress distribution was realized with a vertical downward pressure set on the top of the humerus. The result showed that there were two areas of stress concentration located in the top and bottom. The analysis results were consistent with the basic requirements of bone biomechanics and the results may lay a simulated foundation of the rapid manufacture.of the 3D entity models. Based on the results above, the process for the rapid manufacturing of the right proximal humerus with PLGA/PMMA/HA composite has been completed.The research improved the interface combination between the HA and polymer matrix, from the point of the synthetic methods. The composite could overcome the mismatch of the degradation rate of composite and the formation of bone fiber with the combination of PLGA. And the problem of implant bone mismatching the individual needs for model, size and mechanical characteristics will be solved through rebuilding the three-dimensional entity model of bone injured by scanning its CT data, and driving 3-D printer to implement the process for the rapid manufacturing of bone injured.