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Xu C, Bai X, Ruan D, Zhang C. Comparative finite element analysis of posterior short segment fixation constructs with or without intermediate screws in the fractured vertebrae for the treatment of type a thoracolumbar fracture. Comput Methods Biomech Biomed Engin 2024; 27:1398-1409. [PMID: 37553841 DOI: 10.1080/10255842.2023.2243360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/18/2023] [Accepted: 07/27/2023] [Indexed: 08/10/2023]
Abstract
Six-screw short-segment posterior fixation for thoracolumbar fractures, which involves intermediate screws at the fractured vertebrae has been proposed to reduce the rates of kyphosis recurrence and implant failure. Yet, little is known about the mechanisms and biomechanical responses by which intermediate screws at the fracture vertebrae enhance fixation strength. The objective of this study was to investigate the biomechanical properties that are associated with the augmentation of intermediate screws in relation to the severity of type A thoracolumbar fracture using finite element analysis. Short-segment stabilization models with or without augmentation screws at fractured vertebrae were established based on finite element model of moderate compressive fractures, severe compressive fractures and burst fractures. The spinal stiffness, stresses at the implanted hardware, and axial displacement of the bony defect were measured and compared under mechanical loading conditions. All six-screw stabilization showed a decreased range of motion in extension, lateral bending, and axial rotation compared to the traditional four-screw fixation models. Burst thoracolumbar fracture benefited more from augmentation of intermediate screws at the fracture vertebrae. The stress of the rod in six-screw models increased while decreased that of pedicle screws. Our results suggested that patients with more unstable fractures might achieve greater benefits from augmentation of intermediate screws at the fracture vertebrae. Augmentation of intermediate screws at the fracture vertebrae is recommended for patients with higher wedge-shaped or burst fractures to reduce the risk of hardware failure and postoperative re-collapse of injured vertebrae.
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Affiliation(s)
- Cheng Xu
- Department of Orthopaedic Surgery, The Sixth Medical Center, General Hospital of PLA, Beijing, China
| | - Xuedong Bai
- Department of Orthopaedic Surgery, The Sixth Medical Center, General Hospital of PLA, Beijing, China
| | - Dike Ruan
- Department of Orthopaedic Surgery, The Sixth Medical Center, General Hospital of PLA, Beijing, China
| | - Chao Zhang
- Department of Orthopaedic Surgery, The Sixth Medical Center, General Hospital of PLA, Beijing, China
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Chen H, Kang Y, Yan Y, Wang H, Peng W, Liao Y, Zou M, Xu Z, Song X, Wang W, Wang C. Biomechanical analysis of the tandem spinal external fixation in a multiple-level noncontiguous lumbar fractures model: a finite element analysis. Front Bioeng Biotechnol 2024; 12:1395197. [PMID: 38962665 PMCID: PMC11219947 DOI: 10.3389/fbioe.2024.1395197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2024] [Accepted: 05/29/2024] [Indexed: 07/05/2024] Open
Abstract
Objective This study aimed to investigate the biomechanical characteristics of the tandem spinal external fixation (TSEF) for treating multilevel noncontiguous spinal fracture (MNSF) using finite element analysis and provide a theoretical basis for clinical application. Methods We constructed two models of L2 and L4 vertebral fractures that were fixed with the TSEF and the long-segment spinal inner fixation (LSIF). The range of motion (ROM), maximum stresses at L2 and L4 vertebrae, the screws and rods, and the intervertebral discs of the two models were recorded under load control. Subsequently, the required torque, the maximum stress at L2 and L4 vertebrae, the screws and rods, and the intervertebral discs were analyzed under displacement control. Results Under load control, the TSEF model reserved more ROM than the LSIF model. The maximum stresses of screws in the TSEF model were increased, while the maximum stresses of rods were reduced compared to the LSIF model. Moreover, the maximum stresses of L2 and L4 vertebrae and discs in the TSEF model were increased compared to the LSIF model. Under displacement control, the TSEF model required fewer moments (N·mm) than the LSIF model. Compared to the LSIF model, the maximum stresses of screws and rods in the TSEF model have decreased; the maximum stresses at L2 and L4 in the TSEF model were increased. In the flexion condition, the maximum stresses of discs in the TSEF model were less than the LSIF model, while the maximum stresses of discs in the TSEF model were higher in the extension condition. Conclusion Compared to LSIF, the TSEF has a better stress distribution with higher overall mobility. Theoretically, it reduces the stress concentration of the connecting rods and the stress shielding of the fractured vertebral bodies.
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Affiliation(s)
- Huarong Chen
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Central People’s Hospital of Zhanjiang, Zhanjiang, Guangdong, China
| | - Yu Kang
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- The Third Affiliated Hospital of Sun Yat-sen University, Department of Spine Surgery, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Yiguo Yan
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Hu Wang
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Wen Peng
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Yijia Liao
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Luoyang Orthopedic-Traumatological Hospital of Henan Province (Henan Provincial Orthopedic Hospital), Luoyang, Henan, China
| | - Mingxiang Zou
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Zhun Xu
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Xizheng Song
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Wenjun Wang
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Cheng Wang
- The First Affiliated Hospital, Department of Spine Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan, China
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Liao Y, Yan Y, Kang Y, Wang W, Song X, Peng W, Fu H, Chen H, Wang C. Biomechanical Analysis of the External Fixation in a Lumbar Fracture Model: A Finite Element Study. J Med Biol Eng 2022. [DOI: 10.1007/s40846-022-00727-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Abstract
Purpose
This study aimed to investigate the biomechanical characteristics of the external spinal fixation for treating lumbar fracture through finite element analysis (FEA) and provide a theoretical basis for its further application.
Methods
Two different models of L3 fracture fixed with the external spinal fixation and the internal fixation system respectively were constructed. The ROM, maximum stresses at L3, and the screws of the two models were measured under load control. Subsequently, the applied torque, the maximum stressed at L3, L1/2, L2/3, L3/4, L4/5 discs and the screws were analyzed under displacement control.
Results
Under load control, the external fixation model reserved more ROM than the internal fixation model (40.4–48.0% vs 30.5–41.0%). Compared to the internal fixation model, the maximum stresses at L3 and screws in the external fixation model were increased. Under displacement control, the external fixation model required fewer moments (N·mm) than the internal fixation model (flexion: 7500 vs 12,294; extension: 7500 vs 9027). Further, the maximum stresses at L3 and the screws in the external fixation model were greater than those of the internal fixation model, while the maximum stresses at the upper and lower adjacent discs of fixed segments were less than the internal fixation model.
Conclusion
Compared to the internal fixation system, the external fixation has a better stress distribution with the greater overall mobility. It theoretically reduces the stress concentration of the adjacent discs and the stress shielding of the fractured vertebral body.
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Xia C, Yang S, Liu J, Lu J, Shang D, Fu D, Zhao Z, Wang X. Finite element study on whether posterior upper wall fracture is a risk factor for the failure of short-segment pedicle screw fixation in the treatment of L1 burst fracture. Injury 2021; 52:3253-3260. [PMID: 34521540 DOI: 10.1016/j.injury.2021.08.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 08/04/2021] [Accepted: 08/13/2021] [Indexed: 02/02/2023]
Abstract
PURPOSE To establish the finite element model of T12 and L2 (T12-L2) pedicle screw fixation for severe L1 burst fracture, and quantitatively simulate and analyze the screw stress and vertebral displacement in different degrees of L1 posterior upper wall fracture (PUWF), and evaluate whether PUWF degree is a risk factor for fixation failure. METHODS The data of 6 healthy volunteers were used to establish a finite element model of T12-L2 pedicle screw fixation for type A severe burst fractures. The stress and displacement of the conventional and Schanz pedicle screws for the different degrees of PUWF (including the anterior upper wall of the vertebral canal and the bipedicle) were evaluated. RESULTS The maximum stress and L1 displacement of conventional and Schanz pedicle screws were positively correlated with the severity of the PUWF (P<0.05). During anterior flexion, the maximum stress of conventional pedicle screws for 70% type I were 538.3±59.75MPa and the maximum stress of Schanz pedicle screws for 90% type Ⅱ, 90% type Ⅲ and 70% type IV fractures were close to the fatigue threshold. The maximum stress during anterior flexion were significantly higher than those during posterior extension, bending and rotation (P<0.05). CONCLUSION The posterior upper wall fracture of vertebral body (VB) of type A burst fracture is not an independent risk factor for the failure of short-segment pedicle screw fixation (SSPSF). Anterior flexion of type A fractures combined with severe PUWF of VB was a risk factor for the failure of SSPSF.
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Affiliation(s)
- Chunyang Xia
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China.
| | - Sheng Yang
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China.
| | - Jifeng Liu
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China; Department of Orthopaedics, Yantai Hospital of Shandong Wendeng Orthrpaedics & Traumatology, Shanhai South Road, Laishan district, Yantai 264003, Shandong Province, China.
| | - Jianmin Lu
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China.
| | - Depeng Shang
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China.
| | - Dapeng Fu
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China.
| | - Zhenhua Zhao
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China.
| | - Xiahua Wang
- Department of Orthopedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Dalian, Liaoning 116001, China.
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Numerical Evaluation of Spinal Stability after Posterior Spinal Fusion with Various Fixation Segments and Screw Types in Patients with Osteoporotic Thoracolumbar Burst Fracture Using Finite Element Analysis. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11073243] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The aim of this study was to analyze the spinal stability and safety after posterior spinal fusion with various fixation segments and screw types in patients with an osteoporotic thoracolumbar burst fracture based on finite element analysis (FEA). To realize various osteoporotic vertebral fracture conditions on T12, seven cases of Young’s modulus, namely 0%, 1%, 5%, 10%, 25%, 50%, and 100% of the Young’s modulus, for vertebral bones under intact conditions were considered. Four types of fixation for thoracolumbar fracture on T12 (fixed with T11-L1, T10-T11-L1, T11-L1-L2, and T10-T11-L1-L2) were applied to the thoracolumbar fusion model. The following screw types were considered: pedicle screw (PS) and cortical screw (CS). Using FEA, four motions were performed on the fixed spine, and the stress applied to the screw, peri-implant bone (PIB), and intervertebral disc (IVD) and the range of motion (ROM) were calculated. The lowest ROM calculated corresponded to the T10-T11-L1-L2 model, while the closest to the intact situation was achieved in the T11-L1-L2 fixation model using PS. The lowest stress in the screw and PB was detected in the T10-T11-L1-L2 fixation model.
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Liu J, Yang S, Zhou F, Lu J, Xia C, Wang H, Chen C. The feasibility of short-segment Schanz screw implanted in an oblique downward direction for the treatment of lumbar 1 burst fracture: a finite element analysis. J Orthop Surg Res 2020; 15:537. [PMID: 33203406 PMCID: PMC7672871 DOI: 10.1186/s13018-020-02024-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 10/14/2020] [Indexed: 12/31/2022] Open
Abstract
Background To evaluate the biomechanical properties of short-segment Schanz screw implanted in an oblique downward direction for the treatment of lumbar 1 burst fracture using a finite element analysis. Methods The Universal Spine System (USS) fixation model for adjacent upper and lower vertebrae (T12 and L2) of lumbar 1 vertebra burst fracture was established. During flexion/extension, lateral bending, and rotation, the screw stress and the displacement of bone defect area of the injured vertebrae were evaluated when the downward inserted angle between the long axis of the screws and superior endplate of the adjacent vertebrae was set to 0° (group A), 5° (group B), 10° (group C), and 15°(group D). There were 6 models in each group. Results There were no significant differences in the maximum screw stress among all the groups during flexion/extension, lateral bending, and rotation (P > 0.05). There were no significant differences in the maximum displacement of the bone defect area of the injured vertebrae among all the groups during flexion/extension, lateral bending, and rotation (P > 0.05). Conclusion Short-segment Schanz screw implanted in an oblique downward direction with different angles (0°/parellel, 5°, 10°, and 15°) did not change the maximum stress of the screws, and there was a lower risk of screw breakage in all groups during flexion/extension, lateral bending, and rotation. In addition, the displacement of the injured vertebra defect area had no significant changes with the change of angles.
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Affiliation(s)
- Jifeng Liu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Zhongshan District, Dalian, 116001, Liaoning, China
| | - Sheng Yang
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Zhongshan District, Dalian, 116001, Liaoning, China.
| | - Fei Zhou
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Zhongshan District, Dalian, 116001, Liaoning, China
| | - Jianmin Lu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Zhongshan District, Dalian, 116001, Liaoning, China
| | - Chunyang Xia
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Zhongshan District, Dalian, 116001, Liaoning, China
| | - Huanhuan Wang
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Zhongshan District, Dalian, 116001, Liaoning, China
| | - Chao Chen
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, 6 Jiefang Street, Zhongshan District, Dalian, 116001, Liaoning, China
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Wang TN, Wu BL, Duan RM, Yuan YS, Qu MJ, Zhang S, Huang W, Liu T, Yu XB. Treatment of Thoracolumbar Fractures Through Different Short Segment Pedicle Screw Fixation Techniques: A Finite Element Analysis. Orthop Surg 2020; 12:601-608. [PMID: 32124568 PMCID: PMC7189051 DOI: 10.1111/os.12643] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 11/30/2019] [Accepted: 02/05/2020] [Indexed: 01/11/2023] Open
Abstract
Objective To compare the von Mises stresses of the pedicle screw system and the displacement of injured vertebrae using 3‐D finite element analysis, and to evaluate the curative effect of the pedicle screw system. Methods Finite element methods were used for biomechanical comparison of four posterior short segment pedicle screw fixation techniques. The different pedicle screw models are traditional trajectory (TT), Universal Spine System (USS), cortical bone trajectory (CBT), and CBT at the cranial level and pedicle screw (PS) at the caudal level (UP‐CBT). The stress distribution of the screws and connecting rods under different working conditions and the displacement of the injured vertebrae were compared and analyzed. Results After the pedicle screw system was fixed, the stress under vertical compression was mainly concentrated at the proximal end of the screw, while the stress was mainly concentrated on the connecting rod during flexion, extension, lateral flexion, and rotation. The TT group had the greatest stress during the flexion, extension, and left and right rotation. The UP‐CBT group was most stressed when the left and right sides were flexed; the stress of the USS screw system was less than that of the other three models during flexion, lateral flexion, and rotation. The maximum von Mises stress values of pedicle screws in all exercise states were 556.2, 340.7, 458.1, and 533.4 MPa, respectively. In the USS group, the displacement of the injured vertebra was small in the flexion, and the left and right lateral flexion and the right rotation were higher than in the TT group and the CBT group. The maximum displacements of the injured vertebrae in all motion states were 1.679, 1.604, 1.752, and 1.777 mm, respectively. Conclusion Universal Spine System pedicle screws are relatively less stressed under different working conditions, the risk of breakage is small, and the model is relatively stable; CBT screws do not exhibit better mechanical properties than conventional pedicle screws and USS pedicle screws.
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Affiliation(s)
- Tie-Nan Wang
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Bao-Lin Wu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Rui-Meng Duan
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Ya-Shuai Yuan
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Ming-Jia Qu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Shuo Zhang
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Wei Huang
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Tao Liu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
| | - Xiao-Bing Yu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian, China
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Finite element analysis comparing short-segment instrumentation with conventional pedicle screws and the Schanz pedicle screw in lumbar 1 fractures. Neurosurg Rev 2019; 43:301-312. [DOI: 10.1007/s10143-019-01146-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 07/10/2019] [Accepted: 07/16/2019] [Indexed: 12/23/2022]
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Yang S, Shang DP, Lu JM, Liu JF, Fu DP, Zhou F, Cong Y, Lv ZZ. Modified Posterior Short-Segment Pedicle Screw Instrumentation for Lumbar Burst Fractures with Incomplete Neurological Deficit. World Neurosurg 2018; 119:e977-e985. [PMID: 30114542 DOI: 10.1016/j.wneu.2018.08.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 08/02/2018] [Accepted: 08/03/2018] [Indexed: 01/28/2023]
Abstract
PURPOSE We have introduced a method of modified posterior short-segment pedicle screw fixation and evaluated its clinical effects in treating lumbar burst fractures with incomplete neurological deficits. METHODS The data from 22 patients with lumbar burst fracture and incomplete neurological deficits who had undergone modified posterior short-segment instrumentation with Schanz screw fixation from January 2012 to February 2018 in our clinic were evaluated in the present retrospective study. All Schanz screws were implanted in an oblique downward direction into the vertebrae above and below the injured vertebra (insertion depth, 90%-100%). The implants were removed ∼1 year after surgery. Neurological function, back pain, anterior and posterior body height ratio, kyphosis angle, percentage of canal compromise, fracture severity, and treatment-related complications were evaluated. RESULTS Technical success was achieved in all 22 patients. No infection, instrument loosening or failure, or breakage was observed. Statistically significant improvements with regard to the anterior body height (P < 0.05) and posterior body height (P < 0.05) ratios, kyphosis angle, and percentage of canal compromise (P < 0.05) were observed at 1 week postoperatively or the final follow-up visit. No correction loss had occurred at the final follow-up examination. Postoperatively, all patients with neurological deficits had functional improvement equivalent to ≥1 grade on the American Spinal Injury Association impairment scale and fracture union. Back pain was greatly improved postoperatively. CONCLUSIONS Short-segment Schanz screw fixation implanted in an oblique downward direction seems to be a promising method for lumbar burst fractures with incomplete neurological deficits because it provided good clinical and radiographic outcomes.
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Affiliation(s)
- Sheng Yang
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China.
| | - De-Peng Shang
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China
| | - Jian-Min Lu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China
| | - Ji-Feng Liu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China
| | - Da-Peng Fu
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China
| | - Fei Zhou
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China
| | - Yang Cong
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China
| | - Zhong-Zhe Lv
- Department of Orthopaedics, Affiliated Zhongshan Hospital of Dalian University, Dalian People's Republic of China
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