## 4 Applications of PMMA Bone Cement in Orthopedics  
From the 1970s onward, a significant amount of research was conducted for a better understanding of the thermal properties of PMMA bone cement and how to mitigate its destructive effects on the surrounding bone tissue. In the early 1970s, studies showed that during polymerization, bone cement can exceed temperatures of 70 \({}^{\circ}\)C, leading to thermal necrosis. Studies conducted by [PERSON] and [PERSON] utilized computation models to analyze the temperature distribution in the surrounding bone, as well as the effects of the residual monomers present after the end of the polymerization reaction. Their research revealed that, in small regions of bone, temperatures can exceed 70 \({}^{\circ}\)C, even if for a small amount of time [21]. Another venue for research was the optimization of preparation procedures, different mixing techniques, and cement mantle thickness, as well as the starting temperature of the metallic components, and the cement itself has an effect on the maximum temperature value and polymerization time. These were demonstrated by [PERSON] et al., who concluded that optimal conditions and handling of the cement reduce the peak temperature of the polymerization process and thus lower the risk of thermal necrosis [22]. Recent advancements made in the field of developing composite PMMA bone cement to mitigate the exothermic value of the polymerization process have yielded results. [PERSON] et al. have utilized phase-change materials (PCMs) like paraffin that act as a heat sink in the cement, thereby reducing the maximum temperature values of the exothermic reaction [23] (Figure 3). Certain attempts to incorporate other elements or particles and alternative monomers have been made. [PERSON] and [PERSON] found that utilizing alternative monomers like glycidyl methacrylate (GMA) and adding magnesium oxide nanoparticles has a significant effect on lowering the exothermic temperature of PMMA polymerization, thus lowering the risk of thermal necrosis in the surrounding tissues [24]. Figure 2: The chemical composition of PMMA bone cement. [PERSON] et al. have found that different brands of PMMA bone cement have different thermal properties. Some brands have a temperature peak that exceeds the thermal necrosis threshold of bone cells, while others remain below it but have a higher exposure time. This research suggests that a careful selection of the PMMA bone cement utilized in the procedure can further mitigate the risk of thermal damage to the surrounding bone [25]. There are several cases in which the high temperatures reached during PMMA polymerization actually have the desired effect. During limb-salvage surgery it is used for filling out voids left after tumor excision and offering additional structural support. The mechanical properties of the bone cement allow it to stabilize the skeletal structure, enabling early mobilization and weight-bearing, leading to faster functional recovery [26; 27]. PMMA bone cement is also used for securing endoprosthetic implants in limb-salvage procedures. This is due to the fact that it creates a resilient bond between implants and the bone's surface, this being essential for the longevity and functionality of the prosthesis [27]. Figure 3: A brief timeline of the discovery and innovations of PMMA bone cement. During spinal surgery, in verteboplasty and kyrophoplasty, PMMA is used to stabilize vertebral fractures caused by tumor lesions, be it metastatic or primary spinal tumors. These procedures offer the patients significant pain relief and prevent further aggravation of their symptoms due to the fact that they prevent further vertebral collapse by reinforcing the structural integrity of the affected segment [18; 28]. After curettage of benign or low-grade malignant bone tumors, PMMA can be used as a bone substitute to fill the remaining cavity.