Abstract
Calcium phosphate cements (CPCs) represent excellent bone substitute materials due to their biocompatibility and injectability. However, their poor degradability and lack of macroporosity limits bone regeneration. The addition of poly(d,l‐lactic‐co‐glycolic acid) (PLGA) particles improves macroporosity and therefore late stage material degradation. CPC degradation and hence, bone formation at an early stage remains challenging, due to the delayed onset of PLGA degradation (i.e., after 2–3 weeks). Consequently, we here explored multimodal porogen platforms based on sucrose porogens (for early pore formation) and PLGA porogens (for late pore formation) to enhance CPC degradation and analyzed mechanical properties, dynamic in vitro degradation and in vivo performance in a rat femoral bone defect model. Porogen addition to CPC showed to decrease compressive strength of all CPC formulations; transition of the crystal phase upon in vitro incubation increased compressive strength. Although dynamic in vitro degradation showed rapid sucrose dissolution within 1 week, no additional effects on CPC degradation or bone formation were observed upon in vivo implantation. © 2019 The Authors. journal Of Biomedical Materials Research Part A Published By Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1713–1722, 2019.
Highlights
Calcium phosphate (CaP)-based bone substitutes are the most widely used synthetic alternatives for autologous bone grafts in the field of bone regenerative surgery.[1]
For non-incubated samples, it was observed that pure CaP cements (CPCs) had a compressive strength of 12.2 Æ 1.8 MPa, while addition of sucrose porogens to CPC significantly decreased the compressive strength to 6.9 Æ 1.5 MPa (p < 0.05)
Addition of sucrose to CPC-PLGA significantly decreased the compressive strength to 3.7 Æ 0.9 MPa (p < 0.05)
Summary
Calcium phosphate (CaP)-based bone substitutes are the most widely used synthetic alternatives for autologous bone grafts in the field of bone regenerative surgery.[1] Clinically, CaP-based bone substitutes have advantages over autologous bone in terms of off-the-shelf availability, for which no restrictions in quantity apply and no extra surgical site to harvest donor bone is required. A cement form renders these CaP-based bone substitutes injectable, allowing such CaP cements (CPCs) to be applied via minimally invasive surgery and to be molded into the bone defect for optimal bone defect filling.[2,3] Depending on the end product of the setting reaction, CPCs can be roughly divided in two categories; apatite or brushite. PLGA porogens have a beneficial (hydrolytic) degradation profile, which generates porosity within the ceramic CPC matrix and simultaneously accelerates the degradation of this ceramic
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