Degradation of Polymeric Material used for Osteosynthesis and Comparison of Fracture Toughness between Test and FEA

Bijoy Paul, Salahaddin Sanusei, Gary Barber, J. David Schall, Keyu Li, Peng Qu

Abstract


Biodegradable polymers such as PLA, PGA, PLGA etc., inside the human body often pose a tough challenge for the orthopedic doctors and material scientists. Unlike metallic or ceramic implants, where deterioration of the mechanical properties has never been an issue, biodegradable polymeric implants, used for Osteosynthesis, deteriorate while the fractured bone is subjected to kinesiological stress during healing process. To understand how biodegradable materials lose its mechanical properties, an investigation into the influence of degradation process on Mode-I fracture toughness of poly (lactide-co-glycolide), PLGA 85:15 material was initiated. The objective of this study was to build an improved understanding of the deterioration of biodegradable polymers mechanical properties during in-vitro degradation and how this change may affect long term in-vivo performance of the implants. A simple mathematical relationship was established to understand the change in the Young’s modulus during the degradation process. Compact tension specimens were designed and molded for mode-I fracture criterion and then put in 3% concentrated Hydrogen peroxide (H2O2) to study the degradation process. FEA (Finite Element Analysis) was used to study the change in mechanical properties and then the results were compared with the physical test. Mode-I fracture toughness, KIC was measured and the behavior of the polymer was also identified. It was seen that the fracture toughness, KIC of PLGA 85:15 decreased with the progression of degradation. Finally, it was concluded that an increase in the Young’s modulus made PLGA 85:15 very brittle and hence resulted in reduced fracture toughness.

Keywords


Biodegradable polymeric implants; PLGA 85:15; Osteosynthesis; in-vitro degradation; Hydrogen peroxide; Mode-I fracture; Young’s modulus; FEA; xFEM (Extended Finite Element Method); Fracture toughness; KIC

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