The “Magnesium Sacrifice” Strategy Enables PMMA Bone Cement Partial Biodegradability and Osseointegration Potential

Abstract

Poly (methyl methacrylate) (PMMA)-based bone cements are the most commonly used injectable orthopedic materials due to their excellent injectability and mechanical properties. However, their poor biocompatibility and excessive stiffness may cause complications such as aseptic implant loosening and stress shielding. In this study, we aimed to develop a new type of partially biodegradable composite bone cement by incorporating magnesium (Mg) microspheres, known as “Mg sacrifices” (MgSs), in the PMMA matrix. Being sensitive to the physiological environment, the MgSs in PMMA could gradually degrade to produce bioactive Mg ions and, meanwhile, result in an interconnected macroporous structure within the cement matrix. The mechanical properties, solidification, and biocompatibility, both in vitro and in vivo, of PMMA–Mg bone cement were characterized. Interestingly, the incorporation of Mg microspheres did not markedly affect the mechanical strength of bone cement. However, the maximum temperature upon setting of bone cement decreased. This partially biodegradable composite bone cement showed good biocompatibility in vitro. In the in vivo study, considerable bony ingrowth occurred in the pores upon MgS degradation. Together, the findings from this study indicate that such partially biodegradable PMMA–Mg composite may be ideal bone cement for minimally invasive orthopedic surgeries such as vertebroplasty and kyphoplasty.

Multifunctional Coating to Simultaneously Encapsulate Drug and Prevent Infection of Radiopaque Agent

“…It was reported that the addition of additives into PMMA bone cements would decrease the mechanical property [32,33]. In our group’s previous study, the compressive strength also decreased with addition of magnesium balls [33]. This study shows the same results with previous reports.…”

Layered Double Hydroxide Modified Bone Cement Promoting Osseointegration via Multiple Osteogenic Signal Pathways

“…Therefore, the addition of COL-I or LDH may alleviate stress-shielding osteolysis and indirectly promote osseointegration. 9,42 The Evaluation of Biocompatibility In Vivo and In Vitro. On the basis of the superior physical-chemical properties, the biocompatibility of the PMMA, PMMA&COL-I, PMMA&LDH, and PMMA&COL-I&LDH groups in vitro was further studied using human bone marrow-derived mesenchymal stem cells (hBMSCs).…”

“…Moreover, fluorescent labeling (Figure 5e,f) and acid fuchsin stain assays (Figure 5g,h) were utilized to analyze the degree of bone growing into the implants, and the results are similar to that of micro-CT. All the results indicate that LDH and COL-I&LDH-modified PMMA can be used as effective biomaterials to enhance the osseointegration of the interface between the bone and bone cement, and possibly prevent the occurrence of aseptic loosening. 9…”

“…Since then, it has been applied in clinical use, and its safety and clinical effects have been widely recognized. However, the PMMA bone cement has a few shortcomings: (i) the biological inertness, undegradability, and potential cytotoxic properties hinder the bone formation into PMMA; (ii) the high polymerization temperature will cause the death of surrounding osteoblast-related cells, and the subsequent formation of a fibrotic film will hinder the osseointegration of PMMA bone cement and bone; (iii) the excessive elastic modulus can lead to stress-shielding osteolysis. , Thus, PMMA cannot form biological osseointegration at the implantation site because of the above shortcomings, and leads to aseptic loosening of bone cement, which has become the dominant factor for more than 75% of failures of total hip/knee replacement. − It has proven that aseptic loosening mainly occurs at the interface of the bone cement and bone. , Therefore, how to regulate and modify PMMA bone cement with improved osteogenic activity, decreased polymerization temperature, and reduce elastic modulus so as to promote osseointegration has been a big challenge.…”

Resorbable Mg2+-Containing Phosphates for Bone Tissue Repair

“…Magnesium phosphate-based bone cements have a wide range of medical applications as synthetic bone substitutes because of remarkable properties, such as self-aligning ability, high initial strength, biocompatibility, excellent adhesion, and degradability [58,66,67]. Besides, other researchers have emphasized that these materials are promising for bone replacement, in accordance with the degradability and ability to regenerate bone in orthopedic sheep implant models [68].…”