Maximized specific loss power and intrinsic loss power approaching theoretical limits for alternating-current (AC) magnetic-field heating of nanoparticles are reported. This is achieved by engineering the effective magnetic anisotropy barrier of nanoparticles via alloying of hard and soft ferrites. 22 nm Co Mn Fe O /SiO nanoparticles reach a specific loss power value of 3417 W g at a field of 33 kA m and 380 kHz. Biocompatible Zn Fe O /SiO nanoparticles achieve specific loss power of 500 W g and intrinsic loss power of 26.8 nHm kg at field parameters of 7 kA m and 380 kHz, below the clinical safety limit. Magnetic bone cement achieves heating adequate for bone tumor hyperthermia, incorporating an ultralow dosage of just 1 wt% of nanoparticles. In cellular hyperthermia experiments, these nanoparticles demonstrate high cell death rate at low field parameters. Zn Fe O /SiO nanoparticles show cell viabilities above 97% at concentrations up to 500 µg mL within 48 h, suggesting toxicity lower than that of magnetite.
In this study, a novel 3D printed porous titanium cage (3D printed cage) with interconnected pores inside was designed and manufactured. Observations by scanning electron microscopy showed that the inside of the 3D printed cage had an octahedral porous structure, with the pores uniform in size and connected to each other. The mechanical properties analysis found that the Young's modulus and compressive strength of the porous structure were close to those of the bone structure, and the overall stiffness was slightly higher than that of the polyether ether ketone (PEEK) material, but was significantly lower than that of the titanium alloy solid module. Animal experiments indicated that the new 3D printed cage was equivalent to PEEK cage in fusion time. At 3 months, the new bone grew into the cage through the pores of the new 3D printed cage surface, which had a high bone contact rate. These results demonstrate that the 3D printed porous titanium cage has good biocompatibility and osseointegration, and has a potential clinical value as bone implants. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.
Purpose. To evaluate the biomechanics of a novel fusion strategy (hybrid internal fixation+horizontal cage position) in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). Methods. MIS-TLIF finite element models for three fusion strategies were created based on computed tomography images, namely, Model-A, hybrid internal fixation (ipsilateral pedicle screw and contralateral translaminar facet screw fixation)+horizontal cage position; Model-B, bilateral pedicle screw (BPS) fixation+horizontal cage position; and Model-C, BPS fixation+oblique 45° cage position. A preload of 500 N and a moment of 10 Nm were applied to the models to simulate lumbar motion, and the models’ range of motion (ROM), peak stress of the internal fixation system, and cage were assessed. Results. The ROM for Models A, B, and C were not different ( P > 0.05 ) but were significantly lower than the ROM of Model-INT ( P < 0.0001 ). Although there were subtle differences in the ROM ratio for Models A, B, and C, the trend was similar. The peak stress of the internal fixation system was significantly higher in Model-A than that of Models B and C, but only the difference between Models A and B was significant ( P < 0.05 ). The peak stress of the cage in Model-A was significantly lower than that of Models B and C ( P < 0.01 ). Conclusion. Hybrid internal fixation with horizontal single cage implantation can provide the same biomechanical stability as traditional fixation while reducing peak stress on the cage and vertebral endplate.
Magnesium potassium phosphate cement (MKPC) has attracted considerable attention as a bone regeneration material. However, there are only a few reports on its biomechanical properties. To evaluate the biomechanical properties of MKPC, we compared the mechanical parameters of pedicle screws enhanced with either MKPC or polymethyl methacrylate (PMMA) bone cement. The results show that the maximum pull-out force of the pedicle screws was 417.86 ± 55.57 and 444.43 ± 19.89 N after MKPC cement setting for 30 min and 12 h, respectively, which was better than that of the PMMA cement. In fatigue tests, the maximum pull-out force of the MKPC cement group was 435.20 ± 7.96 N, whereas that of the PMMA cement in the control group was 346.80 ± 7.66 N. Furthermore, the structural characterization analysis of the MKPC cement revealed that its microstructure after solidification was an irregular tightly packed crystal, which improved the mechanical strength of the cement. The maximum exothermic temperature of the MKPC reaction was 45.55 ± 1.35 °C, the coagulation time was 7.89 ± 0.37 min, and the compressive strength was 48.29 ± 4.76 MPa, all of which meet the requirements of clinical application. In addition, the MKPC cement did not significantly inhibit cell proliferation or increase apoptosis, thus indicating good biocompatibility. In summary, MKPC exhibited good biomechanical properties, high initial strength, good biocompatibility, and low exothermic reaction temperature, demonstrating an excellent application potential in the field of orthopedics.
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