Bioabsorbable bone fixation plates for X‐ray imaging diagnosis by a radiopaque layer of barium sulfate and poly(lactic‐co‐glycolic acid)

Abstract

Bone fixation systems made of biodegradable polymers are radiolucent, making post‐operative diagnosis with X‐ray imaging a challenge. In this study, to allow X‐ray visibility, we separately prepared a radiopaque layer and attached it to a bioabsorbable bone plate approved for clinical use (Inion, Finland). We employed barium sulfate as a radiopaque material due to the high X‐ray attenuation coefficient of barium (2.196 cm2/g). The radiopaque layer was composed of a fine powder of barium sulfate bound to a biodegradable material, poly(lactic‐co‐glycolic acid) (PLGA), to allow layer degradation similar to the original Inion bone plate. In this study, we varied the mass ratio of barium sulfate and PLGA in the layer between 3:1 w/w and 10:1 w/w to modulate the degree and longevity of X‐ray visibility. All radiopaque plates herein were visible via X‐ray, both in vitro and in vivo, for up to 40 days. For all layer types, the radio‐opacity decreased with time due to the swelling and degradation of PLGA, and the change in the layer shape was more apparent for layers with a higher PLGA content. The radiopaque plates released, at most, 0.5 mg of barium sulfate every 2 days in a simulated in vitro environment, which did not appear to affect the cytotoxicity. The radiopaque plates also exhibited good biocompatibility, similar to that of the Inion plate. Therefore, we concluded that the barium sulfate‐based, biodegradable plate prepared in this work has the potential to be used as a fixation device with both X‐ray visibility and biocompatibility. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B:596–607, 2015.

Investigation on the environmental‐friendly poly(lactic acid) composites based on precipitated barium sulfate: Mechanical, thermal properties, and kinetic study of thermal degradation

“…The composites of PLA with inorganic fillers have been proved very useful to enhance the impact toughness and thermal properties without significant deteriorated strength and stiffness, of which barium sulfate (BaSO 4 ) must be the most promising candidate . BaSO 4 is a well‐known bioinert filler and usually considered as the gold standard in clinical applications for the x‐ray photography and gamma‐ray absorber, because it is nonharmful to humans and possessed of characteristic radiopacity and biocompatibility . So, it is very suitable for such inorganic filler to design and fabricate the PLA composites with high biosafety.…”

Recent Advances in Polyesters for Biomedical Imaging

“…Typically, encapsulated imaging contrast agents will remain intact for hours to days, while blended contrast agents remain for longer periods of time. A study conducted by Choi et al demonstrated the ability to blend barium sulfate with the polyester poly(lactic‐ co ‐glycolic acid) (PLGA) to form a radio‐opaque surface layer for bioresorbable bone plates . The blend allowed for visualization for up to 56 days in vivo, until the surface layer fully degraded, after which time further monitoring of the remaining bioresorbable bone plate was unattainable.…”

Theranostic Bioabsorbable Bone Fixation Plate with Drug‐Layered Double Hydroxide Nanohybrids

“…To successfully treat a fractured bone, adequate positioning of the fixation devices is important to minimize gap formation within the bone fracture, which must be monitored after implantation to avoid retarded healing and infection. This can be achieved noninvasively by conventional X‐ray imaging for metallic devices; however, this is not possible for a bioabsorbable polymer device because of its inherent radiolucent property . Proper bone regeneration in gaps and voids at the injured sites must also be considered.…”

“…For these reasons, a bioabsorbable fixation device can be more advantageous when enabled with both diagnostic and therapeutic functionalities, i.e., X‐ray visibility and the delivery of a bone‐forming agent, respectively. Previously, polymeric bone cements, plates, or dental resins have been combined with radiopaque materials, such as iodine, bismuth, and biocompatible ceramics . To aid bone healing, therapeutic agents, such as bisphosphonate drugs and bone morphogenetic proteins, have been incorporated with implantable polymer devices .…”