Abstract
Oil-based calcium phosphate cement (Paste-CPC) shows not only prolonged shelf life and injection times, but also improved cohesion and reproducibility during application, while retaining the advantages of fast setting, mechanical strength, and biocompatibility. In addition, poly(L-lactide-co-glycolide) (PLGA) fiber reinforcement may decrease the risk for local extrusion. Bone defects (diameter 5 mm; depth 15 mm) generated ex vivo in lumbar (L) spines of female Merino sheep (2–4 years) were augmented using: (i) water-based CPC with 10% PLGA fiber reinforcement (L3); (ii) Paste-CPC (L4); or (iii) clinically established polymethylmethacrylate (PMMA) bone cement (L5). Untouched (L1) and empty vertebrae (L2) served as controls. Cement performance was analyzed using micro-computed tomography, histology, and biomechanical testing. Extrusion was comparable for Paste-CPC(-PLGA) and PMMA, but significantly lower for CPC + PLGA. Compressive strength and Young’s modulus were similar for Paste-CPC and PMMA, but significantly higher compared to those for empty defects and/or CPC + PLGA. Expectedly, all experimental groups showed significantly or numerically lower compressive strength and Young’s modulus than those of untouched controls. Ready-to-use Paste-CPC demonstrates a performance similar to that of PMMA, but improved biomechanics compared to those of water-based CPC + PLGA, expanding the therapeutic arsenal for bone defects. O, significantly lower extrusion of CPC + PLGA fibers into adjacent lumbar spongiosa may help to reduce the risk of local extrusion in spinal surgery.
Highlights
Bone cements are widely used in different applications of orthopedic surgery due to their injectability, especially for minimally invasive surgical techniques, such as vertebroplasty (VP) or kyphoplasty (KP; [1,2,3])
This was confirmed by quantitation of the cement extrusion, which noticeably decreased for all bone cements with increasing distance from the injection channel
HowThis was confirmed by quantitation of the cement extrusion, which noticeably deever, the values for the calcium phosphate cements (CPC) + poly(L-lactic-co-glycolic acid) (PLGA) were significantly lower compared to both Pastecreased for all bone cements with increasing distance from the injection channel
Summary
Bone cements are widely used in different applications of orthopedic surgery due to their injectability, especially for minimally invasive surgical techniques, such as vertebroplasty (VP) or kyphoplasty (KP; [1,2,3]). PMMA presents some potential drawbacks, including non-biodegradability, monomer toxicity, heat generation during exothermic polymerization (up to 60 ◦ C), and higher stiffness than that of cancellous bone, all of which possibly contribute to fractures of adjacent vertebrae after VP [5,6,7] To overcome these disadvantages, biodegradable calcium phosphate cements (CPC) were recently developed, which show excellent osteoconductivity, resorbability, and a setting reaction at body temperature. A delay in the application of the cement or a prolongation of the operation time, for example, may lead to contamination of the material and increased risk of infections [14] To overcome such drawbacks, so-called ready-to-use (pre-mixed) cements were developed [15,16]. The combination of a waterimmiscible carrier liquid (e.g., synthetic short-chain triglyceride) with surfactants was shown to facilitate a discontinuous liquid exchange in the CPC, leading to an improvement in the shelf life of the pre-mixed paste and a higher reproducibility during application and setting reaction [16]
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