Nanomaterials: The Next Step in Injectable Bone Cements

Abstract

Injectable bone cements (IBCs) are biocompatible materials that can be used as bone defect fillers in maxillofacial surgeries and in orthopedic fracture treatment in order to augment weakened bone due to osteoporosis. Current clinically available IBCs, such as polymethylmethacrylate and calcium phosphate cement, have certain advantages; however, they possess several drawbacks that prevent them from gaining universal acceptance. New gel-based injectable materials have also been developed, but these are too mechanically weak for load-bearing applications. Recent research has focused on improving various injectable materials using nanomaterials in order to render them suitable for bone tissue regeneration. This article outlines the requirements of IBCs, the advantages and limitations of currently available IBCs and the state-of-the-art developments that have demonstrated the effects of nanomaterials within injectable systems.

Nanotechnology for treating osteoporotic vertebral fractures

“…During surgery, bone cement is formed into a paste by mixing the powder and the liquid, and the paste can then either be injected through a channel or molded by the surgeon into the sites of bone defects or voids. 39 After setting and hardening, the paste conforms to the shape of the defect or void, and solidifies to achieve enough strength to support the vertebra. The characteristics and properties of PMMA, CPC, and CSC for vertebroplasty and kyphoplasty are shown in Table 2.…”

“…55 Although adding nanofibers has a positive effect by enhancing the mechanical properties of CPC, identification of suitable nanofibers that are bioresorbable and bioactive while being able to provide sufficient strength and fracture toughness remains challenging. 39 Recent studies have demonstrated that carbon nanotubes (CNTs) may be a reasonable choice. In the study by Wang et al, incorporation of 0.2 wt% and 0.5 wt% as-received CNTs into CPC resulted in an increase in compressive strength by 24%, and biomineralized CNTs led to a 120% increase in the compressive strength of CPC.…”

“…39 This strategy also has the ability to provide a bioactive environment for enhancing bone cell recruitment, adhesion, proliferation, and differentiation. 39 Therefore, nanotechnology-enhanced bone cements are expected to be better for the treatment of OVF and thus should be further studied and developed.…”

“…43 Similarly, the increased nanometer surface roughness achieved by embedding TiO 2 nanoparticles (32 nm in diameter) in polymer matrix was demonstrated to increase osteoblast activity. 39 Based on these in vitro studies, it appears that the improved osteoblast activity of PMMA bone cements are due to the nanoscale surface roughness resulted from addition of oxide nanoparticles.…”

“…This high stiffness has a stress-shielding effect, weakening neighboring vertebrae and ultimately causing them to fracture. 39 Creating porous structures in the hardened PMMA bone cement is becoming an effective strategy to overcome the ultrahigh stiffness of PMMA. For example, the elastic modulus and yield strength of PMMA could be decreased when mixed with a 2% aqueous solution of sodium hyaluronate gel.…”