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Wei Zheng - One of the best experts on this subject based on the ideXlab platform.
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biomechanical comparative study of the stability of injectable pedicle screws with different lateral holes augmented with different volumes of polymethylmethacrylate in osteoporotic Lumbar Vertebrae
The Spine Journal, 2018Co-Authors: Da Liu, Jiangjun Zhou, Jun Sheng, Yang Luo, Chen Huang, Xiaojun Zhang, Wei ZhengAbstract:Abstract Background Context Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Until now, there had been no studies of the relationship between screw stability and the distribution and volume of PMMA. Purpose The objective of this study was to analyze the relationship between screw stability and the distribution pattern and injected volume of PMMA. Study Design This is a biomechanical comparison of injectable pedicle screws with different lateral holes augmented with different volumes of PMMA in cadaveric osteoporotic Lumbar Vertebrae. Methods Forty-eight osteoporotic Lumbar Vertebrae were randomly divided into Groups A, B, and C with different pedicle screws (16 Vertebrae in each group), and then each group was randomly divided into Subgroups 0, 1, 2, and 3 with different volumes of PMMA (four vertebra with eight pedicles in each subgroup). A pilot hole was prepared in advance using the same method in all samples. Type A and type B pedicle screws were directly inserted into Vertebrae in Groups A and B, respectively, and then different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL) were injected through the screws and into Vertebrae in Subgroups 0, 1, 2, and 3. The pilot holes were filled with different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL), and then the screws were inserted in Groups C0, C1, C2, and C3. Screw position and distribution of PMMA were evaluated radiographically, and axial pullout tests were performed to measure maximum axial pullout strength (Fmax). Results Polymethylmethacrylate surrounded the anterior one-third of screws in the vertebral body in Groups A1, A2, and A3; the middle one-third of screws in the junction area of the vertebral body and the pedicle in Groups B1, B2, and B3; and the full length of screws evenly in both the vertebral body and the pedicle in Groups C1, C2, and C3. There was no malpositioning of screws or leakage of PMMA in any sample. Two-way analysis of variance revealed that two factors—distribution and volume of PMMA—significantly influenced Fmax (p Conclusions Polymethylmethacrylate can significantly enhance the stability of different injectable pedicle screws in osteoporotic Lumbar Vertebrae, and screw stability is significantly correlated with the distribution pattern and the injected volume of PMMA. The closer the PMMA to the pedicle and the greater the quantity of injected PMMA, the greater is the pedicle screw stability. Injection of 2.0 mL of PMMA through screws with four lateral 180° holes or of 1.0 mL of PMMA through screws with six lateral 180° holes increases the stability of pedicle screws.
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biomechanical comparison of pedicle screw augmented with different volumes of polymethylmethacrylate in osteoporotic and severely osteoporotic cadaveric Lumbar Vertebrae an experimental study
The Spine Journal, 2016Co-Authors: Da Liu, Bo Zhang, Qingyun Xie, Xia Kang, Jiangjun Zhou, Cairu Wang, Wei Lei, Wei ZhengAbstract:Abstract Background Context Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Intriguingly, there have been no biomechanical comparisons of the stability of pedicle screws augmented with different volumes of PMMA or studies of the relationship between screw stability and volume of PMMA, especially in different degrees of osteoporosis. Purpose The purposes of the study reported here were to compare screw stability by different volumes of PMMA augmentation, to analyze the relationship between screw stability and PMMA volume, and to make a preliminary determination of the optimum volume of PMMA augmentation for different degrees of osteoporosis. Study Design This study is a biomechanical comparison of pedicle screws augmented with various volumes of PMMA in cadaveric Lumbar Vertebrae. Methods Thirty-six pedicles from 18 osteoporotic Lumbar Vertebrae were randomly divided into groups A0 through A5, and 36 pedicles from 18 severely osteoporotic Lumbar Vertebrae were randomly divided into groups B0 through B5. A different volume of PMMA was injected into each one of groups A0 through A5 (0, 0.5, 1.0, 1.5, 2.0, and 2.5 mL, respectively) and into each one of groups B0 through B5 (0, 1.0, 1.5, 2.0, 2.5, and 3.0 mL, respectively), and then pedicle screws were inserted in all Vertebrae. After complete solidification of the PMMA, we examined pedicle X-rays, performed axial pullout tests, and determined the maximum axial pullout strength (F max ) for all samples. Results No PMMA was found around the screws in groups A0 and B0. In groups A1 to A5 and B1 to B5, screws were wrapped by gradually increasing amounts of PMMA. There was no PMMA leakage or screw malpositioning in any samples. The F max in groups A1 through A5 increased by 32.40%, 64.42%, 116.02%, 174.07%, and 207.42%, respectively, compared with that in group A0. There were no significant differences in F max between groups A0 and A1, A1 and A2, A2 and A3, A3 and A4, and A4 and A5 (p>.05), but there were significant differences in F max between any other two groups (p max in groups B1 through B5 increased by 23.48%, 48.40%, 106.60%, 134.73%, and 210.04%, respectively, compared with that in group B0. There were no significant differences in F max between groups B0 and B1, B0 and B2, B1 and B2, B2 and B3, B3 and B4 (p>.05), but there were significant differences in F max between any other two groups (p max and volume of PMMA in both osteoporotic and severely osteoporotic Lumbar Vertebrae (p Conclusions Polymethylmethacrylate can significantly enhance stability of pedicle screws in both osteoporotic and severely osteoporotic Lumbar Vertebrae. There is a significant positive correlation between screw stability and volume of PMMA. Within a certain range, nevertheless, increasing the volume of PMMA does not significantly improve screw stability. We suggest that 1.5 and 3 mL, respectively, are the volumes of injected PMMA that will optimize pedicle screw stability in osteoporotic and severely osteoporotic Lumbar Vertebrae.
Roland Chapurlat - One of the best experts on this subject based on the ideXlab platform.
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the predictive value of trabecular bone score tbs on whole Lumbar Vertebrae mechanics an ex vivo study
Osteoporosis International, 2013Co-Authors: Jeanpaul Roux, Julien Wegrzyn, Stephanie Boutroy, Mary L Bouxsein, Didier Hans, Roland ChapurlatAbstract:We investigated the association of trabecular bone score (TBS) with microarchitecture and mechanical behavior of human Lumbar Vertebrae. We found that TBS reflects vertebral trabecular microarchitecture and is an independent predictor of vertebral mechanics. However, the addition of TBS to areal BMD (aBMD) did not significantly improve prediction of vertebral strength. The trabecular bone score (TBS) is a gray-level measure of texture using a modified experimental variogram which can be extracted from dual-energy X-ray absorptiometry (DXA) images. The current study aimed to confirm whether TBS is associated with trabecular microarchitecture and mechanics of human Lumbar Vertebrae, and if its combination with BMD improves prediction of fracture risk. Lumbar Vertebrae (L3) were harvested fresh from 16 donors. The anteroposterior and lateral bone mineral content (BMC) and areal BMD (aBMD) of the vertebral body were measured using DXA; then, the TBS was extracted using TBS iNsight software (Medimaps SA, France). The trabecular bone volume (Tb.BV/tissue volume, TV), trabecular thickness (Tb.Th), degree of anisotropy, and structure model index (SMI) were measured using microcomputed tomography. Quasi-static uniaxial compressive testing was performed on L3 vertebral bodies to assess failure load and stiffness. The TBS was significantly correlated to Tb.BV/TV and SMI (r = 0.58 and −0.62; p = 0.02, 0.01), but not related to BMC and BMD. TBS was significantly correlated with stiffness (r = 0.64; p = 0.007), independently of bone mass. Using stepwise multiple regression models, we failed to demonstrate that the combination of BMD and TBS was better at explaining mechanical behavior than either variable alone. However, the combination TBS, Tb.Th, and BMC did perform better than each parameter alone, explaining 79 % of the variability in stiffness. In our study, TBS was associated with microarchitecture parameters and with vertebral mechanical behavior, but TBS did not improve prediction of vertebral biomechanical properties in addition to aBMD.
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the predictive value of trabecular bone score tbs on whole Lumbar Vertebrae mechanics an ex vivo study
Osteoporosis International, 2013Co-Authors: Jeanpaul Roux, Julien Wegrzyn, Stephanie Boutroy, Mary L Bouxsein, Didier Hans, Roland ChapurlatAbstract:Summary We investigated the association of trabecular bone score (TBS) with microarchitecture and mechanical behavior of human Lumbar Vertebrae. We found that TBS reflects vertebral trabecular microarchitecture and is an in- dependent predictor of vertebral mechanics. However, the addition of TBS to areal BMD (aBMD) did not significantly improve prediction of vertebral strength. Introduction The trabecular bone score (TBS) is a gray- level measure of texture using a modified experimental variogram which can be extracted from dual-energy X-ray absorptiometry (DXA) images. The current study aimed to confirm whether TBS is associated with trabecular microarchitecture and mechanics of human Lumbar verte- brae, and if its combination with BMD improves prediction of fracture risk. Methods Lumbar Vertebrae (L3) were harvested fresh from 16 donors. The anteroposterior and lateral bone mineral content (BMC) and areal BMD (aBMD) of the vertebral body were measured using DXA; then, the TBS was extracted using TBS iNsight software (Medimaps SA, France). The trabecular bone volume (Tb.BV/tissue volume, TV), trabecular thickness (Tb.Th), degree of anisotropy, and structure model index (SMI) were measured using microcomputed tomography. Quasi-static uniaxial compres- sive testing was performed on L3 vertebral bodies to assess failure load and stiffness. Results The TBS was significantly correlated to Tb.BV/TV and SMI (r=0.58 and −0.62; p=0.02, 0.01), but not related to BMC and BMD. TBS was significantly correlated with stiffness (r=0.64; p=0.007), independently of bone mass. Using stepwise multiple regression models, we failed to demonstrate that the combination of BMD and TBS was better at explaining mechanical behavior than either variable alone. However, the combination TBS, Tb.Th, and BMC did perform better than each parameter alone, explaining 79 % of the variability in stiffness. Conclusions In our study, TBS was associated with microarchitecture parameters and with vertebral mechanical behavior, but TBS did not improve prediction of vertebral biomechanical properties in addition to aBMD.
Da Liu - One of the best experts on this subject based on the ideXlab platform.
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biomechanical comparative study of the stability of injectable pedicle screws with different lateral holes augmented with different volumes of polymethylmethacrylate in osteoporotic Lumbar Vertebrae
The Spine Journal, 2018Co-Authors: Da Liu, Jiangjun Zhou, Jun Sheng, Yang Luo, Chen Huang, Xiaojun Zhang, Wei ZhengAbstract:Abstract Background Context Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Until now, there had been no studies of the relationship between screw stability and the distribution and volume of PMMA. Purpose The objective of this study was to analyze the relationship between screw stability and the distribution pattern and injected volume of PMMA. Study Design This is a biomechanical comparison of injectable pedicle screws with different lateral holes augmented with different volumes of PMMA in cadaveric osteoporotic Lumbar Vertebrae. Methods Forty-eight osteoporotic Lumbar Vertebrae were randomly divided into Groups A, B, and C with different pedicle screws (16 Vertebrae in each group), and then each group was randomly divided into Subgroups 0, 1, 2, and 3 with different volumes of PMMA (four vertebra with eight pedicles in each subgroup). A pilot hole was prepared in advance using the same method in all samples. Type A and type B pedicle screws were directly inserted into Vertebrae in Groups A and B, respectively, and then different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL) were injected through the screws and into Vertebrae in Subgroups 0, 1, 2, and 3. The pilot holes were filled with different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL), and then the screws were inserted in Groups C0, C1, C2, and C3. Screw position and distribution of PMMA were evaluated radiographically, and axial pullout tests were performed to measure maximum axial pullout strength (Fmax). Results Polymethylmethacrylate surrounded the anterior one-third of screws in the vertebral body in Groups A1, A2, and A3; the middle one-third of screws in the junction area of the vertebral body and the pedicle in Groups B1, B2, and B3; and the full length of screws evenly in both the vertebral body and the pedicle in Groups C1, C2, and C3. There was no malpositioning of screws or leakage of PMMA in any sample. Two-way analysis of variance revealed that two factors—distribution and volume of PMMA—significantly influenced Fmax (p Conclusions Polymethylmethacrylate can significantly enhance the stability of different injectable pedicle screws in osteoporotic Lumbar Vertebrae, and screw stability is significantly correlated with the distribution pattern and the injected volume of PMMA. The closer the PMMA to the pedicle and the greater the quantity of injected PMMA, the greater is the pedicle screw stability. Injection of 2.0 mL of PMMA through screws with four lateral 180° holes or of 1.0 mL of PMMA through screws with six lateral 180° holes increases the stability of pedicle screws.
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biomechanical comparison of pedicle screw augmented with different volumes of polymethylmethacrylate in osteoporotic and severely osteoporotic cadaveric Lumbar Vertebrae an experimental study
The Spine Journal, 2016Co-Authors: Da Liu, Bo Zhang, Qingyun Xie, Xia Kang, Jiangjun Zhou, Cairu Wang, Wei Lei, Wei ZhengAbstract:Abstract Background Context Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Intriguingly, there have been no biomechanical comparisons of the stability of pedicle screws augmented with different volumes of PMMA or studies of the relationship between screw stability and volume of PMMA, especially in different degrees of osteoporosis. Purpose The purposes of the study reported here were to compare screw stability by different volumes of PMMA augmentation, to analyze the relationship between screw stability and PMMA volume, and to make a preliminary determination of the optimum volume of PMMA augmentation for different degrees of osteoporosis. Study Design This study is a biomechanical comparison of pedicle screws augmented with various volumes of PMMA in cadaveric Lumbar Vertebrae. Methods Thirty-six pedicles from 18 osteoporotic Lumbar Vertebrae were randomly divided into groups A0 through A5, and 36 pedicles from 18 severely osteoporotic Lumbar Vertebrae were randomly divided into groups B0 through B5. A different volume of PMMA was injected into each one of groups A0 through A5 (0, 0.5, 1.0, 1.5, 2.0, and 2.5 mL, respectively) and into each one of groups B0 through B5 (0, 1.0, 1.5, 2.0, 2.5, and 3.0 mL, respectively), and then pedicle screws were inserted in all Vertebrae. After complete solidification of the PMMA, we examined pedicle X-rays, performed axial pullout tests, and determined the maximum axial pullout strength (F max ) for all samples. Results No PMMA was found around the screws in groups A0 and B0. In groups A1 to A5 and B1 to B5, screws were wrapped by gradually increasing amounts of PMMA. There was no PMMA leakage or screw malpositioning in any samples. The F max in groups A1 through A5 increased by 32.40%, 64.42%, 116.02%, 174.07%, and 207.42%, respectively, compared with that in group A0. There were no significant differences in F max between groups A0 and A1, A1 and A2, A2 and A3, A3 and A4, and A4 and A5 (p>.05), but there were significant differences in F max between any other two groups (p max in groups B1 through B5 increased by 23.48%, 48.40%, 106.60%, 134.73%, and 210.04%, respectively, compared with that in group B0. There were no significant differences in F max between groups B0 and B1, B0 and B2, B1 and B2, B2 and B3, B3 and B4 (p>.05), but there were significant differences in F max between any other two groups (p max and volume of PMMA in both osteoporotic and severely osteoporotic Lumbar Vertebrae (p Conclusions Polymethylmethacrylate can significantly enhance stability of pedicle screws in both osteoporotic and severely osteoporotic Lumbar Vertebrae. There is a significant positive correlation between screw stability and volume of PMMA. Within a certain range, nevertheless, increasing the volume of PMMA does not significantly improve screw stability. We suggest that 1.5 and 3 mL, respectively, are the volumes of injected PMMA that will optimize pedicle screw stability in osteoporotic and severely osteoporotic Lumbar Vertebrae.
Kozo Sato - One of the best experts on this subject based on the ideXlab platform.
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surface strain distribution on thoracic and Lumbar Vertebrae under axial compression the role in burst fractures
Spine, 1999Co-Authors: Michio Hongo, Eiji Abe, Yoichi Shimada, Hajime Murai, Noriyuki Ishikawa, Kozo SatoAbstract:STUDY DESIGN The surface strain distribution on the thoracic and Lumbar Vertebrae during axial compressive loading was examined. OBJECTIVES To examine the general mechanical behavior of the thoracic and Lumbar Vertebrae to evaluate their role in burst fractures. SUMMARY OF BACKGROUND DATA Burst fractures are generally characterized by injury to the middle column and fracturing of the superior endplate. However, results in previous biomechanical investigations have not shown how these fractures are initiated during compression. METHODS Twenty-one thoracic and Lumbar Vertebrae (5 T10, 10 L1, and 6 L4) with upper and lower Vertebrae were studied. Three-axis rosette strain gauges were cemented to 11 sites on the vertebral surface. An axial compressive load was applied, and the strain was measured in each specimen. The strain recorded by each rosette gauge was converted into a tensile, compressive, and shear component. RESULTS The highest tensile and compressive strain was recorded at the base of the pedicle. Shear strain in the vertebral body was significantly higher than that in the lamina at all three spinal levels. At L1 and L4, the tensile strain at the superior vertebral rim was higher than that at the inferior rim. CONCLUSIONS The high tensile and compressive strains found at the base of the pedicle of T10, L1, and L4 indicate that the base of the pedicle is the site of fracture initiation. The higher tensile strain at the superior vertebral rim of L1 and L4 supports the clinical observation of the thoracoLumbar burst fractures.
William C Hutton - One of the best experts on this subject based on the ideXlab platform.
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the effect of pedicle screw redirection after lateral wall breach a biomechanical study using human Lumbar Vertebrae
The Spine Journal, 2014Co-Authors: Michael P Stauff, Brett A Freedman, Jinhwan Kim, Takahiko Hamasaki, Tim S Yoon, William C HuttonAbstract:Abstract Background context Currently, pedicle screw segmental fixation of the spine is considered a standard of care for a number of conditions. Most surgeons employ a free-hand technique using various intraoperative modalities to improve pedicle screw accuracy. Despite continued improvements in technique, pedicle breach remains a frequent occurrence. Once a breach is detected intraoperatively, the most common corrective maneuver is to medially redirect the pedicle screw into the pedicle. To our knowledge, the biomechanical impact of medially redirecting a pedicle screw after a lateral pedicle breach has not been examined. Purpose To compare the fixation strength of perfectly placed pedicle screws to the fixation strength of pedicle screws that were correctly placed after having been redirected (RD) following a lateral pedicle breach. Study design/setting A biomechanical study using human Lumbar Vertebrae. Methods Ten fresh human Lumbar Vertebrae were isolated from five donors. Each vertebra was instrumented with a monoaxial pedicle screw into each pedicle using two different techniques. On one side, a perfect center-center (CC) screw path was created using direct visualization and fluoroscopy. A 6.0-mm-diameter cannulated tap and a pedicle probe were used to develop the pedicle for the 7.0-mm-diameter by 45-mm-long cannulated pedicle screw, which was placed using a digital torque driver. On the contralateral side, an intentional lateral pedicle wall breach was created at the pedicle-vertebral body junction using a guide wire, a 6.0-mm-diameter cannulated tap, and a pedicle probe. This path was then redirected into a CC position, developed, and instrumented with a 7.0-mm-diameter by 45-mm-long cannulated pedicle screw: the RD screw. For each pedicle screw, we assessed four outcome measures: maximal torque, seating torque, screw loosening, and post-loosening axial pullout. Screw loosening and axial pullout were assessed using an MTS machine. Results The biomechanical cost of a lateral pedicle breach and the requirement to redirect the pedicle screw are as follows: an overall drop of 28% (p Conclusions Compared with a CC Lumbar pedicle screw, an RD Lumbar pedicle screw placed after a lateral wall breach is significantly weaker in terms of maximal insertional torque, seating torque, screw loosening force, and axial pullout strength. These significant decreases in biomechanical properties are clearly important when RD pedicle screws are placed at the cephalad or caudal end of a long construct. In this situation, augmentation of the RD screw is an option.
