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Bahreinizad H, Chowdhury SK. Implant Design and Cervical Spinal Biomechanics and Neurorehabilitation: A Finite Element Investigation. Mil Med 2024; 189:791-799. [PMID: 39160809 DOI: 10.1093/milmed/usae279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 03/15/2024] [Accepted: 05/10/2024] [Indexed: 08/21/2024] Open
Abstract
INTRODUCTION The cervical spine, pivotal for mobility and overall body function, can be affected by cervical spondylosis, a major contributor to neural disorders. Prevalent in both general and military populations, especially among pilots, cervical spondylosis induces pain and limits spinal capabilities. Anterior Cervical Discectomy and Fusion (ACDF) surgery, proposed by Cloward in the 1950s, is a promising solution for restoring natural cervical curvature. The study objective was to investigate the impacts of ACDF implant design on postsurgical cervical biomechanics and neurorehabilitation outcomes by utilizing a biofield head-neck finite element (FE) platform that can facilitate scenario-specific perturbations of neck muscle activations. This study addresses the critical need to enhance computational models, specifically FE modeling, for ACDF implant design. MATERIALS AND METHODS We utilized a validated head-neck FE model to investigate spine-implant biomechanical interactions. An S-shaped dynamic cage incorporating titanium (Ti) and polyetheretherketone (PEEK) materials was modeled at the C4/C5 level. The loading conditions were carefully designed to mimic helmet-to-helmet impact in American football, providing a realistic and challenging scenario. The analysis included intervertebral joint motion, disk pressure, and implant von Mises stress. RESULTS The PEEK implant demonstrated an increased motion in flexion and lateral bending at the contiguous spinal (C4/C5) level. In flexion, the Ti implant showed a modest 5% difference under 0% activation conditions, while PEEK exhibited a more substantial 14% difference. In bending, PEEK showed a 24% difference under 0% activation conditions, contrasting with Ti's 17%. The inclusion of the head resulted in an average increase of 18% in neck angle and 14% in C4/C5 angle. Disk pressure was influenced by implant material, muscle activation level, and the presence of the head. Polyetheretherketone exhibited lower stress values at all intervertebral disc levels, with a significant effect at the C6/C7 levels. Muscle activation level significantly influenced disk stress at all levels, with higher activation yielding higher stress. Titanium implant consistently showed higher disk stress values than PEEK, with an orders-of-magnitude difference in von Mises stress. Excluding the head significantly affected disk and implant stress, emphasizing its importance in accurate implant performance simulation. CONCLUSIONS This study emphasized the use of a biofidelic head-neck model to assess ACDF implant designs. Our results indicated that including neck muscles and head structures improves biomechanical outcome measures. Furthermore, unlike Ti implants, our findings showed that PEEK implants maintain neck motion at the affected level and reduce disk stresses. Practitioners can use this information to enhance postsurgery outcomes and reduce the likelihood of secondary surgeries. Therefore, this study makes an important contribution to computational biomechanics and implant design domains by advancing computational modeling and theoretical knowledge on ACDF-spine interaction dynamics.
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Affiliation(s)
| | - Suman K Chowdhury
- Department of Industrial, Manufacturing, and Systems Engineering, Texas Tech University, Lubbock, TX 79409-3061, USA
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Liang W, Yang Y, Han B, Sun D, Yin P, Hai Y. Biomechanical Analysis of Hybrid Artificial Discs or Zero-Profile Devices for Treating 1-Level Adjacent Segment Degeneration in ACDF Revision Surgery. Neurospine 2024; 21:606-619. [PMID: 38955532 PMCID: PMC11224737 DOI: 10.14245/ns.2347330.665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 02/17/2024] [Accepted: 02/17/2024] [Indexed: 07/04/2024] Open
Abstract
OBJECTIVE Cervical hybrid surgery optimizes the use of cervical disc arthroplasty (CDA) and zero-profile (ZOP) devices in anterior cervical discectomy and fusion (ACDF) but lacks uniform combination and biomechanical standards, especially in revision surgery (RS). This study aimed to investigate the biomechanical characteristics of adjacent segments of the different hybrid RS constructs in ACDF RS. METHODS An intact 3-dimensional finite element model generated a normal cervical spine (C2-T1). This model was modified to the primary C5-6 ACDF model. Three RS models were created to treat C4-5 adjacent segment degeneration through implanting cages plus plates (Cage-Cage), ZOP devices (ZOP-Cage), or Bryan discs (CDA-Cage). A 1.0-Nm moment was applied to the primary C5-6 ACDF model to generate total C2-T1 range of motions (ROMs). Subsequently, a displacement load was applied to all RS models to match the total C2-T1 ROMs of the primary ACDF model. RESULTS The ZOP-Cage model showed lower biomechanical responses including ROM, intradiscal pressure, maximum von Mises stress in discs, and facet joint force in adjacent segments compared to the Cage-Cage model. The CDA-Cage model exhibited the lowest biomechanical responses and ROM ratio at adjacent segments among all RS models, closely approached or lower than those in the primary ACDF model in most motion directions. Additionally, the maximum von Mises stress on the C3-4 and C6-7 discs increased in the Cage-Cage and ZOP-Cage models but decreased in the CDA-Cage model when compared to the primary ACDF model. CONCLUSION The CDA-Cage construct had the lowest biomechanical responses with minimal kinematic change of adjacent segments. ZOP-Cage is the next best choice, especially if CDA is not suitable. This study provides a biomechanical reference for clinical hybrid RS decision-making to reduce the risk of ASD recurrence.
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Affiliation(s)
- Weishi Liang
- Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
- Joint Laboratory for Research and Treatment of Spinal Cord Injury in Spinal Deformity, Laboratory for Clinical Medicine, Capital Medical University, Beijing, China
- Center for Spinal Deformity, Capital Medical University, Beijing, China
| | - Yihan Yang
- Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
- Joint Laboratory for Research and Treatment of Spinal Cord Injury in Spinal Deformity, Laboratory for Clinical Medicine, Capital Medical University, Beijing, China
- Center for Spinal Deformity, Capital Medical University, Beijing, China
| | - Bo Han
- Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
- Joint Laboratory for Research and Treatment of Spinal Cord Injury in Spinal Deformity, Laboratory for Clinical Medicine, Capital Medical University, Beijing, China
- Center for Spinal Deformity, Capital Medical University, Beijing, China
| | - Duan Sun
- Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
- Joint Laboratory for Research and Treatment of Spinal Cord Injury in Spinal Deformity, Laboratory for Clinical Medicine, Capital Medical University, Beijing, China
- Center for Spinal Deformity, Capital Medical University, Beijing, China
| | - Peng Yin
- Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
- Joint Laboratory for Research and Treatment of Spinal Cord Injury in Spinal Deformity, Laboratory for Clinical Medicine, Capital Medical University, Beijing, China
- Center for Spinal Deformity, Capital Medical University, Beijing, China
| | - Yong Hai
- Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
- Joint Laboratory for Research and Treatment of Spinal Cord Injury in Spinal Deformity, Laboratory for Clinical Medicine, Capital Medical University, Beijing, China
- Center for Spinal Deformity, Capital Medical University, Beijing, China
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Lin M, Paul R, Dhar UK, Doulgeris J, O’Connor TE, Tsai CT, Vrionis FD. A Review of Finite Element Modeling for Anterior Cervical Discectomy and Fusion. Asian Spine J 2023; 17:949-963. [PMID: 37408489 PMCID: PMC10622829 DOI: 10.31616/asj.2022.0295] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 11/13/2022] [Accepted: 11/14/2022] [Indexed: 07/07/2023] Open
Abstract
The cervical spine poses many complex challenges that require complex solutions. Anterior cervical discectomy and fusion (ACDF) has been one such technique often employed to address such issues. In order to address the problems with ACDF and assess the modifications that have been made to the technique over time, finite element analyses (FEA) have proven to be an effective tool. The variations of cervical spine FEA models that have been produced over the past couple of decades, particularly more recent representations of more complex geometries, have not yet been identified and characterized in any literature. Our objective was to present material property models and cervical spine models for various simulation purposes. The outlining and refinement of the FEA process will yield more reliable outcomes and provide a stable basis for the modeling protocols of the cervical spine.
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Affiliation(s)
- Maohua Lin
- Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL,
USA
| | - Rudy Paul
- Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL,
USA
| | - Utpal Kanti Dhar
- Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL,
USA
| | - James Doulgeris
- Department of Neurosurgery, Marcus Neuroscience Institute, Baptist Health South Florida, Boca Raton, FL,
USA
| | - Timothy E. O’Connor
- Department of Neurosurgery, Marcus Neuroscience Institute, Baptist Health South Florida, Boca Raton, FL,
USA
| | - Chi-Tay Tsai
- Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL,
USA
| | - Frank D. Vrionis
- Department of Neurosurgery, Marcus Neuroscience Institute, Baptist Health South Florida, Boca Raton, FL,
USA
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Suk KS, Jimenez KA, Jo JH, Kim HS, Lee HM, Moon SH, Lee BH. Anterior Plate-Screws and Lower Postoperative T1 Slope Affect Cervical Allospacer Failures in Multi-Level ACDF Surgery: Anterior Versus Posterior Fixation. Global Spine J 2023; 13:89-96. [PMID: 33648356 PMCID: PMC9837507 DOI: 10.1177/2192568221991515] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
STUDY DESIGN Prospective observational study. OBJECTIVE In ACDF, graft failure and subsidence are common complications of surgery. Depending on the cervical fixation, different biomechanical characteristics are applied on the grafts. This aims to describe the incidence of cervical spacer failure in patients with cervical degenerative condition according to the cervical fixation method and sagittal balance. METHOD From November 2011 to December 2015, 262 patients who underwent cervical spine surgery were enrolled prospectively. Patients were divided into 3 groups based on fixation method: anterior plate/screw (APS), posterior lateral mass screw (LMS), pedicle screw (PPS) groups. Serial X-rays and CT scans were utilized to evaluate radiologic outcomes. RESULTS Mean patient ages were 56.1 years in the APS group, 61.5 years in the LMS group, and 57.6 years in the PPS group (P = 0.002). Allospacer failure was most common in the APS group, compared to the LMS and PPS groups (chi-square, P = 0.038). Longer fusion level was associated with greater allospacer failure (Baseline 2 level surgery; Odds ratio (OR) 3.4 in 3 level, 15.2 in 4 level, P = 0.036,0.013). Higher T1 slope was correlated with less allospacer failure (OR 0.875, P = 0.001). ORs of allospacer failure in the LMS and PPS groups were 0.04 and 0.02, respectively, (P = 0.01, 0.01), compared with the APS group. CONCLUSION This study was able to show that allospacer failure in multi-level ACDF surgery is more common with a longer fusion length, less postoperative T1 slope, and an anterior plate-screws technique. Pedicle screws provided the best biomechanical stability among the 3 constructs.
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Affiliation(s)
- Kyung-Soo Suk
- Department of Orthopedic Surgery, Yonsei
University College of Medicine, Seoul, Korea
| | - Kathryn Anne Jimenez
- Department of Orthopedic Surgery, Yonsei
University College of Medicine, Seoul, Korea
| | - Je Hyung Jo
- Department of Orthopedic Surgery, Yonsei
University College of Medicine, Seoul, Korea
| | - Hak-Sun Kim
- Department of Orthopedic Surgery, Yonsei
University College of Medicine, Seoul, Korea
| | - Hwan-Mo Lee
- Department of Orthopedic Surgery, Yonsei
University College of Medicine, Seoul, Korea
| | - Seong-Hwan Moon
- Department of Orthopedic Surgery, Yonsei
University College of Medicine, Seoul, Korea
| | - Byung Ho Lee
- Department of Orthopedic Surgery, Yonsei
University College of Medicine, Seoul, Korea,Byung Ho Lee, Department of Orthopedic
Surgery, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu,
Seoul, 120-752, Korea.
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Zhang DX, Guo LX. Effect of different fixation methods on biomechanical property of cervical vertebral body replacement and fusion. Clin Biomech (Bristol, Avon) 2023; 101:105864. [PMID: 36563544 DOI: 10.1016/j.clinbiomech.2022.105864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 10/25/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
BACKGROUND The main purpose of this study was to examine the effect of different fixation methods (anterior fixation, self-stabilizing fixation and anterior-posterior fixation) on biomechanical property of vertebral body replacement and fusion. METHODS Three finite element models of cervical vertebral body replacement and fusion were established. The implanted models included artificial vertebral body and fixation system, and the loads imposed on the models included 75 N compression load and 1 Nm moment load. FINDINGS For anterior-posterior fixation, the cervical load was mainly transmitted by the posterior pedicle screw and rod (more than 50%), and the stress shielding problem was the most significant than the self-stabilizing and anterior fixation. Self-stabilizing fixation was more helpful to the fusion of implant and vertebrae, but the higher risk of vertebral body collapse was worthy of attention if the cervical spine with osteoporosis. The stress of bone was mainly concentrated around the screw hole. The maximum stress (20.03 MPa) was lower than the yield stress of cortical bone and the possibility of fracture around the fixation device of cervical spine was low. The anterior fixation could meet the requirement of vertebral body replacement and fusion, and the addition of posterior pedicle screws and rods might obtain better treatment in cases of severe spine injury or osteoporosis. INTERPRETATION The findings of this study may provide guidance on clinical treatments for choosing more appropriate fixation methods for different patients.
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Affiliation(s)
- Dong-Xiang Zhang
- School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China
| | - Li-Xin Guo
- School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China.
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Biomechanical Comparison of Multilevel Lumbar Instrumented Fusions in Adult Spinal Deformity According to the Upper and Lower Fusion Levels: A Finite Element Analysis. BIOMED RESEARCH INTERNATIONAL 2022; 2022:2534350. [PMID: 36506913 PMCID: PMC9729043 DOI: 10.1155/2022/2534350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 11/11/2022] [Accepted: 11/14/2022] [Indexed: 12/03/2022]
Abstract
Multilevel lumbar fusion with posterior pedicle screw fixation is a widely performed surgical procedure for the management of adult spinal deformity. However, there has not been a comprehensive biomechanical study on the different types of fusion levels in terms of stability and possible complications. We aimed to investigate the biomechanical properties of multilevel lumbar fusion according to different types of upper and lower fusion levels. Six different types of fusions were performed using three-dimensional finite element models. Type A and B referred to the group of which upper fusion level was L1 and T10, respectively. Subtype 1, 2, and 3 referred to the group of which lower fusion level was L5, S1, and ilium, respectively (A1, L1-L5; A2, L1-S1; A3, L1-ilium; B1, T10-L5; B2, T10-S1; B3, T10-ilium). Flexion, extension, axial rotation, and lateral bending moments were applied, and the risk of screw loosening and failure and adjacent segment degeneration (ASD) was analyzed. Stress at the bone-screw interface of type B3 was lowest in overall motions. The risk of screw failure showed increasing pattern as the upper and lower levels extended in all motions. Proximal range of motion (ROM) increased as the lower fusion level changed from L5 to S1 and the ilium. For axial rotation, type B3 showed higher proximal ROM (16.2°) than type A3 (11.8°). In multilevel lumbar fusion surgery for adult spinal deformity, adding iliac screws and increasing the fusion level to T10-ilium may lower the risk of screw loosening. In terms of screw failure and proximal ASD, however, T10-ilium fusion has a higher potential risk compared with other fusion types. These results will contribute for surgeons to provide adequate patient education regarding screw failure and proximal ASD, when performing multilevel lumbar fusion.
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Short Plate with Screw Angle over 20 Degrees Improves the Radiologic Outcome in ACDF: Clinical Study. J Clin Med 2021; 10:jcm10092034. [PMID: 34068531 PMCID: PMC8125967 DOI: 10.3390/jcm10092034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/29/2021] [Accepted: 05/05/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Anterior cervical discectomy and fusion surgery is a common procedure for degenerative cervical spine. This describes allospacer and implant-related outcomes, comparing medium plate-low screw angle and short plate-high screw angle techniques. METHODS From January 2016 to June 2019, 79 patients who underwent ACDF were prospectively enrolled. Patients were divided, depending on the plate-screw system used: medium plate-low screw angle (12.3 ± 2.5 to 13.2 ± 3.2 degrees), and short plate-high screw angle (22.8 ± 5.3 to 23.3 ± 4.7 degrees). Subsidence, ALOD, and sagittal cervical balance were analyzed using lateral cervical X-rays. NDI and VAS scores were also evaluated. RESULTS Age for medium plate-low-angled screw group is 58.0 ± 11.3 years, and 55.3 ± 12.0 in the short plate-high-angled screw group (p-value = 0.313). Groups were comparable in mean NDI (p-value = 0.347), VAS (p-value = 0.156), C2-C7 SVA, (p-value = 0.981), and lordosis angle (p-value = 0.836) at 1-year post-surgery. Subsidence was higher in the medium plate-low-angled screw than in the short plate-high-angled screw (25% and 8.5%, respectively, p-value = 0.045). ALOD is also more common in the medium plate group (p-value = 0.045). CONCLUSION Use of a short plate and insertion of high-angled screws (more than 20 degrees) has less chance of subsidence and occurrence of ALOD than the traditional technique of using medium plate and low angle.
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Cao F, Fu R, Wang W. Comparison of biomechanical performance of single-level triangular and quadrilateral profile anterior cervical plates. PLoS One 2021; 16:e0250270. [PMID: 33857243 PMCID: PMC8049474 DOI: 10.1371/journal.pone.0250270] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 04/02/2021] [Indexed: 11/18/2022] Open
Abstract
The quadrilateral anterior cervical plate (ACP) is used extensively in anterior cervical discectomy and fusion (ACDF) to reconstruct the stability of the cervical spine and prevent cage subsidence. However, there have been no comparison studies on the biomechanical performance of quadrilateral ACP and triangular ACP. The objective of this study is to investigate the functional outcomes of quadrilateral ACP and triangular ACP usage in ACDF surgery. In this study, a finite element model of intact C1-C7 segments was established and verified. Additionally, two implant systems were built; one using triangle anterior cervical plates (TACP) and another using quadrilateral orion anterior cervical plate (QACP). Both models were then compared in terms of their postoperative biomechanical performance, under normal and excessive motion. Compared to QACP, the peak stress of the TACP screws and plates occurred at 359.2 MPa and 97.2 MPa respectively and were the highest during over extension exercises. Alternately, compared to TACP, the endplate peak stress and the cage displacement of QACP were the largest at over extension, with values of 7.5 MPa and 1.2 mm, respectively. Finally, the average stress ratio of bone grafts in TACP was relatively high at 31.6%. In terms of biomechanical performance, TACP can share the load more flexibly and reduce the risks of cage subsidence and slippage but the screws have high peak stress value, thereby increasing the risk of screw slippage and fracture. This disadvantage must be considered when designing a TACP based implant for a potential patient.
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Affiliation(s)
- Fu Cao
- School of Mechanical Engineering, Xinjiang University, Urumqi, China
| | - Rongchang Fu
- School of Mechanical Engineering, Xinjiang University, Urumqi, China
| | - Wenyuan Wang
- School of Mechanical Engineering, Xinjiang University, Urumqi, China
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Biomechanical Analysis of Allograft Spacer Failure as a Function of Cortical-Cancellous Ratio in Anterior Cervical Discectomy/Fusion: Allograft Spacer Alone Model. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10186413] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The design and ratio of the cortico-cancellous composition of allograft spacers are associated with graft-related problems, including subsidence and allograft spacer failure. Methods: The study analyzed stress distribution and risk of subsidence according to three types (cortical only, cortical cancellous, cortical lateral walls with a cancellous center bone) and three lengths (11, 12, 14 mm) of allograft spacers under the condition of hybrid motion control, including flexion, extension, axial rotation, and lateral bending,. A detailed finite element model of a previously validated, three-dimensional, intact C3–7 segment, with C5–6 segmental fusion using allograft spacers without fixation, was used in the present study. Findings: Among the three types of cervical allograft spacers evaluated, cortical lateral walls with a cancellous center bone exhibited the highest stress on the cortical bone of spacers, as well as the endplate around the posterior margin of the spacers. The likelihood of allograft spacer failure was highest for 14 mm spacers composed of cortical lateral walls with a cancellous center bone upon flexion (PVMS, 270.0 MPa; 250.2%) and extension (PVMS: 371.40 MPa, 344.2%). The likelihood of allograft spacer subsidence was also highest for the same spacers upon flexion (PVMS, 4.58 MPa; 28.1%) and extension (PVMS: 12.71 MPa, 78.0%). Conclusion: Cervical spacers with a smaller cortical component and of longer length can be risk factors for allograft spacer failure and subsidence, especially in flexion and extension. However, further study of additional fixation methods, such as anterior plates/screws and posterior screws, in an actual clinical setting is necessary.
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Kwon JW, Bang SH, Park TH, Lee SJ, Lee HM, Lee SB, Lee BH, Moon SH. Biomechanical comparison of cervical discectomy/fusion model using allograft spacers between anterior and posterior fixation methods (lateral mass and pedicle screw). Clin Biomech (Bristol, Avon) 2020; 73:226-233. [PMID: 32062472 DOI: 10.1016/j.clinbiomech.2020.01.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 01/23/2020] [Accepted: 01/27/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND The purpose of this study is to investigate effects of different fixation methods on the physical stress on allospacers, endplate-vertebral body, and implants using finite element model analyses. METHODS Stress distribution and subsidence risk according to the fixation methods under the condition of hybrid motion control were analyzed. The detailed finite element model of a previously validated, three-dimensional, intact cervical spinal segment model, with C5-C6 segmental fusion using allospacer, was used to evaluate the biomechanical characteristics of different fixation combinations, such as anterior plate/screws, lateral mass screw, and posterior pedicle screw. FINDINGS The load sharing on allospacers increased in extension in order of posterior pedicle screws (21.4%), lateral mass screws (31.5%), and anterior plate/screws (56.6%). lateral mass screw demonstrated the highest load sharing (68.1%) on the allospacer in flexion. The Peak von Mises stress of the allospacer was the lowest in flexion and axial rotation but the highest in extension with anterior plate/screws. Allospacer subsidence risk was the lowest in extension, lateral bending, and axial rotation with posterior pedicle screws but the lowest in flexion with anterior plate/screws. The bone-screw loosening risk was the lowest in all modes with posterior pedicle screws but the highest with anterior plate/screws. INTERPRETATION Posterior pedicle screws demonstrated the best mechanical stability of allospacer failure-subsidence and the lowest risk of screw loosening. Different motion restrictions depending on the fixation method should be considered for implant and allospacer safety.
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Affiliation(s)
- Ji-Won Kwon
- Department of Orthopedic Surgery, National Health Insurance Service Ilsan Hospital, 100 Ilsan-ro, Goyang 10444, Republic of Korea
| | - Sun Hee Bang
- School of Biomedical Engineering, Inje University, 197 Inje-ro, Gimhae-si, Gyeongsangnam-do 50834, Republic of Korea
| | - Tae Hyun Park
- School of Biomedical Engineering, Inje University, 197 Inje-ro, Gimhae-si, Gyeongsangnam-do 50834, Republic of Korea
| | - Sung-Jae Lee
- School of Biomedical Engineering, Inje University, 197 Inje-ro, Gimhae-si, Gyeongsangnam-do 50834, Republic of Korea
| | - Hwan-Mo Lee
- Department of Orthopedic Surgery, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | - Soo-Bin Lee
- Department of Orthopedic Surgery, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | - Byung Ho Lee
- Department of Orthopedic Surgery, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.
| | - Seong-Hwan Moon
- Department of Orthopedic Surgery, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
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