Bioabsorbable chitosan/hydroxyapatite composite rod prepared by in-situ precipitation for internal fixation of bone fracture

Chitosan (CS), an N-deacetylation product of chitin, consists of glucosamine and N-acetylglucosamine units linked through 1 ∼ 4 glycosidic bonds. CS rod is selected as a potential material for bone fracture internal fixation of human being due to its biodegradability and inherent wound healing. Incorporation of hydroxyapatite (HA), the mineral component of bone, could improve the bioactivity and the bone-bonding ability. A HA filled CS rod was prepared by in-situ precipitation. The mechanical properties were characterized and evaluated for suitability as a bone graft substitute. X-Ray Diffraction (XRD) was performed to determine the change of the structure of HA in the before and after processing. Scanning electron microscopy (SEM) was carried out to investigate the microstructure of CS/HA composite. Effect of HA content on the mechanical properties and water absorption of CS/HA composite were also investigated. It was observed that the mechanical properties of the composite in the dry condition improved as the percentage of CS content increased. Mechanical properties of such CS/HA composite rod are much better than that prepared via traditional method. Bending strength, bending modulus, double shear strength and compress strength of CS/HA composite are 67.8 MPa, 3.3 GPa, 21.2 MPa and 47.8 MPa, respectively. All of these material properties are twice or three times stronger compared with that of nature bone of human being, indicating that such a novel bioabsorbable CS/HA composite could be used as internal fixation of bone fracture. Furthermore, the water absorption of CS/HA composite decreased when addition of HA powders into CS matrix, which contributes to postponing the attenuation of mechanical properties of CS/HA composite under moisture condition.