Finite Element Analysis of a Novel Fusion Strategy in Minimally Invasive Transforaminal Lumbar Interbody Fusion.

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.

The cell uptake properties and hyperthermia performance of Zn0.5Fe2.5O4/SiO2 nanoparticles as magnetic hyperthermia agents.

Zn0.5Fe2.5O4 nanoparticles (NPs) of 22 nm are synthesized by a one-pot approach and coated with silica for magnetic hyperthermia agents. The NPs exhibit superparamagnetic characteristics, high-specific absorption rate (SAR) (1083 wg-1, f = 430 kHz, H = 27 kAm-1), large saturation magnetization (M s = 85 emu g-1), excellent colloidal stability and low cytotoxicity. The cell uptake properties have been investigated by Prussian blue staining, transmission electron microscopy and the inductively coupled plasma-mass spectrometer, which resulted in time-dependent and concentration-dependent internalization. The internalization appeared between 0.5 and 2 h, the NPs were mainly located in the lysosomes and kept in good dispersion after incubation with human osteosarcoma MG-63 cells. Then, the relationship between cell uptake and magnetic hyperthermia performance was studied. Our results show that the hyperthermia efficiency was related to the amount of internalized NPs in the tumour cells, which was dependent on the concentration and incubation time. Interestingly, the NPs could still induce tumour cells to apoptosis/necrosis when extracellular NPs were rinsed, but the cell kill efficiency was lower than that of any rinse group, which indicated that local temperature rise was the main factor that induced tumour cells to death. Our findings suggest that this high SAR and biocompatible silica-coated Zn0.5Fe2.O4 NPs could serve as new agents for magnetic hyperthermia.

[Comparison of minimally invasive transforaminal lumbar interbody fusion between two approaches in treatment of single-segment lumbar spinal stenosis].

OBJECTIVE: To compare the effectiveness of minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) with bilateral decompression via unilateral approach and bilateral decompression via bilateral approaches in the treatment of single-segment lumbar spinal stenosis. METHODS: Between February 2015 and January 2017, 70 cases of single-segment lumbar spinal stenosis were treated with MIS-TLIF. The bilateral decompression via unilateral approach (group U) was performed in 36 cases and bilateral decompression via bilateral approaches (group B) in 34 cases. There was no significant difference in age, gender, body mass index, disease duration, distribution of responsibility segments, preoperative visual analogue scale (VAS) score of low back pain and leg pain and Oswestry disability index (ODI) score ( P>0.05). The operation time, intraoperative blood loss, hospitalization stay after operation, complications related to operation, incidence of asymptomatic lateral root symptoms, VAS scores of low back pain and leg pain, and ODI score before and after operation were compared between the two groups. X-ray film and CT scan at 12 months after operation were used to assessted the intervertebral bony fusion. RESULTS: The operation time and intraoperative blood loss in group U were significantly less than those in group B ( P<0.05). There was no significant difference in hospitalization stay after operation between the two groups ( t=-0.311, P=0.757). During the operation, 1 case in group U and 2 cases in group B had dural tear. No screw placement related nerve injury or asymptomatic lateral root symptoms occurred after operation. The patients were followed up 24 to 38 months, with an average of 32.8 months in group U and 35.5 months in group B. The VAS scores of low back pain and leg pain at 2 days, 3, 6, and 12 months after operation were significantly lower than that before operation in the two groups ( P<0.05), and there was no significant difference between the two groups ( P>0.05). The ODI scores at 3, 6 and 12 months after operation were significantly lower than that before operation in the two groups ( P<0.05), and there was no significant difference between the two groups ( P>0.05). Radiographic examination showed interbody fusion at 12 months after operation in the two groups. CONCLUSION: MIS-TLIF is safe and effective in the treatment of single-segment lumbar spinal stenosis with bilateral decompression via unilateral approach and bilateral decompression via bilateral approaches. Bilateral decompression via unilateral approach takes less operation time and has less intraoperative blood loss.