Alternative Radiopacifiers for Poly(Methyl Methacrylate) Bone Cement for Use in Cemented Arthroplasty and Augmentation of Osteoporotic Vertebral Compression Fracture

Background: Poly (methyl methacrylate) bone cement (or, simply, bone cement) is used in diverse applications, such as total arthroplasty, treatment/management of osteoporotic vertebral compression fractures, and bone filling. Micron-sized BaSO₄ or ZrO₂ particles (one of the powder constituents of the cement) act as the radiopacifying agent. One of the shortcomings of bone cement is that there are many undesirable effects of these particles, such as depreciation of the mechanical properties of the cement. Although there is a substantial body of literature in which this shortcoming is addressed by using alternative radiopacifiers, a review of it is lacking. Purpose: This was to conduct a comprehensive critical review of the literature on studies that focus on the synthesis of alternative radiopacifiers, the determination of radiopacity of cement specimens, and the determination of the influence of alternative radiopacifiers on various cement properties. Methodology: Using relevant keywords, an extensive search was conducted of applicable databases, such as Google Scholar, Scopus, and Web of Science, to identify relevant articles. After that, inclusion and exclusion criteria were applied to make a final selection of the articles. Each article was critically reviewed from the perspectives of the methods used to prepare test specimens and the determination of radiopacity. Findings: The final selection comprised 35 articles that covered studies on 38 different alternative radiopacifiers. In the vast majority of the studies, the experimental bone cement formulation was one in which an alternative radiopacifier was blended with the powder and x-radiography was used to determine radiopacity. Examples of alternative radiopacifiers are nano-sized BaSO₄ particles and iodine-containing methacrylate. Using a subset of radiopacity results, an index of effectiveness of an alternative radiopacifier was determined as the increase of R (determined relative to the radiopacity of a radiopaque control cement specimen) (IEAR). IEAR ranged from 3% to 187%, with a Weibull median of 18%. Twelve shortcomings of the literature and associated suggestions for future studies are presented. Summary: The literature on studies on alternative radiopacifiers for bone cement is uneven in that, for example, some aspects of the topic are well covered whereas many others have attracted scant research attention, if any. This observation led to suggestions of twelve areas for future study.