β-TCP/PLA複合スクリューのせん断強度及びねじり強度に及ぼす分子配向の影響

抄録

Poly(lactic acid) (PLA) attracts much attention as a material of bone fixation device which is used for fracture treatment, because it degrades to nontoxic lactic acid through non-enzymatic hydrolytic degradation. However, the material has drawbacks, such as lower elastic modulus and no osteoconductivity. Therefore, a composite material of poly(lactic acid) (PLA) and bioactive ceramics powder which has higher stiffness and osteoconductivity has been investigated. Composite bone fixation device with hydroxyapatite (HA) which is a main inorganic constituent of bone has been developed. However, degradation rate of HA/PLA composite is too low. It was reported that this composite remained for 5 years in vivo. In addition, the strength in composite material of polymers and ceramics decreased by stress concentration around ceramic particles. In this study, PLA was compounded to β-tricalcium phosphate (β-TCP) and β-TCP/PLA composite was drawn to improve the strength. Past studies about self-reinforcing by drawing has been conducted to polymer. In the present study, effect of ceramic particles on mechanical properties and higher order structure of β-TCP/PLA composite was investigated. Screw was focused as the most general bone fixation device and formed from drawn β-TCP/PLA composites. The shear strength and orientation function were measured as mechanical properties and higher order structure, respectively.