Fabrication of injectable and expandable PMMA/PAAS f bone cements

Abstract The volume of polymethyl methacrylate (PMMA) bone cement shrank by 3.82%–7.08% during solidification. Such volume shrinkage generated a residual stress that induces minor cracking in bone–cement interface and affected the long-term stability and mechanical property of vertebral body. In this study, injectable and expandable PMMA/sodium polyacrylate short fiber (PAAS f ) composite bone cements were fabricated, and water absorption and swelling properties of PAAS f were taken into account. Effects of PAAS f volume fraction in PMMA/PAAS f bone cements on absorption ratios of simulated body fluid (SBF) and volume expansion ratios were investigated. When the volume fraction of PAAS f was lower than 30%, PMMA/PAAS f bone cements were stable and did not fall apart after expansion in SBF, and the maximum volume expansion ratio was 33.4%. When PAAS f content increased from 10 vol% to 30 vol%, solidification time of PMMA/PAAS f bone cements increased and their injection and mechanical properties decreased, although the PMMA/PAAS f bone cements (9:1) still satisfy the requirements for clinical application. The absorption expansion mechanism of PMMA/PAAS f bone cements in SBF in the first stage of expansion (global expansion before solidification) and in the second stage of expansion (local surface expansion after solidification) was analyzed through micro-computed tomography and SEM. Cytotoxicity of PMMA bone cement and PMMA/PAAS f bone cements were compared, and results suggested that their cytotoxicity did not significantly vary. These findings indicated that injectable and expandable PMMA/PAAS f bone cements can be used in clinical treatments.