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ObjectiveThere is still controversy about which internal fixation method should be used in oblique lateral interbody fusion (OLIF). This paper aims to compare the biomechanical stability of OLIF with different internal fixation methods.MethodsA 31-year-old healthy male volunteer was selected to have a 64-slice spiral CT scan of his lumbar spine. Mimics 19.0, Geomagic Studio 2013, SolidWorks 2017 and other software were used to build a three-dimensional model of L3-L5, and OLIF surgery was simulated to build OLIF finite element models with five different fixation methods: pedicle screw (PS), lateral single rod screw (LSRS), lateral double rod screw (LDRS), lateral single rod screw+ipsilateral translaminar facet screw (LSRS+ITLFS), lateral single rod screw+contralateral translaminar facet screw (LSRS+CTLFS). After validating the validity of the model, the motion modes of spinal flexion, extension, lateral bending and rotation were simulated, and the fixed segment activity and stress distribution characteristics of each model were compared.ResultsIn terms of fixed segment activity, PS had the best fixation effect, and its range of motion (ROM) was the smallest in all 6 modes. The ROM of the vertebral body was maximized when the LSRS was fixed in all directions. LSRS+ITLFS, LSRS+CTLFS and PS had the similar ROM. In terms of maximum stress of cage, PS had the minimum one except in the left bending. LSRS+ITLFS had little stress in all directions except in flexion; LSRS+CTLFS had little stress in all directions except in extension. In terms of the maximum stress in internal fixation, PS had the least one in all directions; LSRS+CTLFS followed, and the maximum stress appeared in extension and right bending (123.05MPA and 91.74MPA, respectively).ConclusionIn OLIF surgery, PS has the best biomechanical effect. LSRS+CTLFS has the similar effect and its clinical operation is simple with relatively small surgical injury, thus providing a reference for clinical choice.
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BACKGROUND: Cement-augmented pedicle screw is an effective fixation for osteoporotic spine, and it is important to reduce the rate of cement leakage. OBJECTIVE: To evaluate the stability of cementing the apical and terminal pedicle screw applied in osteoporotic spine with lumbosacral degenerative disease by finite element analysis. METHODS: An intact finite element model of L2-5 segment was established by using CT scan data of one normal male volunteer. After verifying the validity of the intact model, the cementing apical and terminal pedicle screw and cement-augmented pedicle screw models of double/multi-level segment fixation were established, respectively. A 150 N vertical axial pre-load was imposed on the superior surface and a 10 N·m moment was applied on the superior surface along the radial direction to simulate six different physiological motions: flexion, extension, left bending, right bending, left rotation, and right rotation. The different of range of motion, cage stress, and pedicle screw stress on fixed segments were compared between models. RESULTS AND CONCLUSION: (1) The validity showed that the range of motion of the intact model was similar to cadaveric studies in all directions. (2) The range of motion of cementing the apical and terminal pedicle screw group was slightly larger than that of cement-augmented pedicle screw group and the difference between the two groups was less than 0.15°. The two fixation methods could maintain the similar stability of the operation segment. (3) The difference of the cage stress and instrument stress was also small between the two groups. (4) These results suggest that compare with cement-augmented pedicle screw, cementing the apical and terminal pedicle screw can increase the approximate stability in double-level and multi-level segment fusion. The cementing the apical and terminal pedicle screw procedure may reduce the risk of cement leakage and patient costs, and offer a useful alternative to the cement-augmented pedicle screw procedure.
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<p><b>OBJECTIVE</b>To establish osteoblast-osteoclast cell co-culture system in a Transwell chamber, and detect cell viability of osteoblasts and osteoclasts in system.</p><p><b>METHODS</b>Osteoblast MC3T3-E1 and mouse monocytes RAW264.7 were cultivated in vitro. RANKL-induced mouse RAW264.7 monocytes differentiated into mature osteoclasts, osteoblast-osteoclast cell co-culture system was established in Transwell chamber. Cell activity of osteoblasts and osteoclasts were detected by CCK-8 experimenting, Alizarin Red staining, TRAP staining. The expression of OPG, ALP, RANKL, TGF-b1 gene and RANKL protein in osteoblast MC3T3-E1 were detected by PCR, Western-Blot methods. Also, the expression of RANK, NF-κB in gene and protein level in osteoclast were measured through the same method respectively.</p><p><b>RESULTS</b>The co-culture system of Mouse MC3T3-E1 cells and RAW264.7 cell were established in Transwell chamber. Co-culture system affected cell division activities of osteoblasts and osteoclasts. Differentiation of osteoblasts were increased, while differentiation of osteoclast division were slight decreased under microscope observation. OPG (0.65±0.08) and ALP (0.16±0.01) gene expression of co-culture system were less than single culture OPG(1.00±0.08) and ALP (1.01±0.16); TGF-b1(4.42±0.21) and RANKL(4.12±1.04) of osteoblasts in co-culture system were higher than TGF-b1(1.00±0.10) and RANKL(1.00±0.09) under single culture. However, gene expression of RANK(0.63±0.06) and NF-κB(0.64±0.08) in co-culture system were decreased than RANK(1.00±0.08) and NF-κB(1.00±0.09), in single culture, and had significant differences. Similarly, protein expression of OPG(0.43±0.05) and NF-κB(0.59±0.05) of co-culture system were less than OPG(0.84±0.06) and NF-κB(1.13±0.03) of single culture. While RANKL protein expression (0.54±0.03)of co-culture system was more than single culture RANKL(0.31±0.03), and had statistically differences, which was in agreement of the trend of gene expression change.</p><p><b>CONCLUSIONS</b>Co-culture system of mouse MC3T3-E1 cells and RAW264.7 cell was viable in Transwell chamber, and the activity of osteoblasts is higher than osteoclasts in co-culture system.</p>