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Xie S, Cui L, Liu J, Qing P, Li J. Impact of screw tip design on screw anchorage: mechanical testing and numerical simulation. J Orthop Surg Res 2024; 19:447. [PMID: 39080768 PMCID: PMC11287948 DOI: 10.1186/s13018-024-04841-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Accepted: 06/07/2024] [Indexed: 08/03/2024] Open
Abstract
BACKGROUND Screw loosening is a commonly reported issue following spinal screw fixation and can lead to various complications. The initial cause of screw loosening is biomechanical deterioration. Previous studies have demonstrated that modifications in screw design can impact the local biomechanical environment, specifically the stress distribution on bone-screw interfaces. There are several different designs of screw tips available for clinically used pedicle screws; however, it remains unclear whether these variations affect the local stress distribution and subsequent screw anchorage ability. METHODS This study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to investigate this topic. Models of pedicle screw-fixed osteoporotic polyurethane foam were created with two different clinically used screw tip designs (flat and steep) featuring varying tip lengths, taper angles, and diameters, as well as identical flank overlap areas and thread designs. The anchorage ability of the different models was assessed through toggle and pull-out test. Additionally, numerical mechanical models were utilized to compute the stress distributions at the screw and bone-screw interfaces in the different models. RESULTS Mechanical tests revealed superior anchorage ability in models utilizing flat-tipped screws. Furthermore, numerical modeling indicated improved anchorage ability and reduced stress concentration tendency in these models. CONCLUSION Changes in screw tip design can significantly impact the biomechanical anchoring capability of screws. Specifically, flatter tip pedicle screws may mitigate the risk of screw loosening by alleviating stress concentration on bone-screw interfaces.
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Affiliation(s)
- Shiming Xie
- Department of Spine surgery, Mianyang Orthopedic Hospital, Mianyang, Sichuan Province, 621052, P.R. China
| | - Liqiang Cui
- Department of Spine surgery, Mianyang Orthopedic Hospital, Mianyang, Sichuan Province, 621052, P.R. China
| | - Jinhui Liu
- Sichuan Provincial Laboratory of Orthopaedic Engineering, Department of Bone and Joint Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, PR China
| | - Peidong Qing
- Department of Spine surgery, Mianyang Orthopedic Hospital, Mianyang, Sichuan Province, 621052, P.R. China.
| | - Jingchi Li
- Department of Orthopedics, Luzhou Key Laboratory of Orthopedic Disorders, The Affiliated Traditional Chinese Medicine Hospital, Southwest Medical University, Luzhou, Sichuan Province, 646000, P.R. China.
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Zhan X, Gao F, Yang Y, Tsai T, Wan Z, Yu Y. Effect of Insertional Direction of Pedicle Screw on Screw Loosening: A Biomechanical Study on Synthetic Bone Vertebra under a Physiology-like Load. Orthop Surg 2024; 16:1461-1472. [PMID: 38714346 PMCID: PMC11144517 DOI: 10.1111/os.14080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/06/2024] [Accepted: 04/09/2024] [Indexed: 05/09/2024] Open
Abstract
OBJECTIVES It is now understood that pedicle screw loosening at the implant-bone interface can lead to poor screw-bone interface purchase and decreased fixation stability. Previous biomechanical tests used cadaveric vertebrae and pull-out or torque loads to assess the effect of the insertional direction of pedicle screws on screw loosening. However, these tests faced challenges in matching biomechanical differences among specimens and simulating in vivo loads applied on pedicle screws. This study aimed to evaluate the effect of the insertional direction of pedicle screws on screw loosening using tension-compression-bending loads and synthetic bone vertebrae. METHODS Polyaxial pedicle screws were inserted into nine synthetic bone vertebrae in three directions (three samples per group): cranial, parallel, and caudad (-10°, 0°, +10° of the pedicle screw rod to the upper plane of the vertebra, respectively). Pedicle screws in the vertebrae were loaded using a polyethylene block connected to a material testing machine. Tension-compression-bending loads (100N-250N) with 30,000 cycles were applied to the pedicle screws, and displacements were recorded and then cycle-displacement curve was drawn based on cycle number. Micro-CT scans were performed on the vertebrae after removing the pedicle screws to obtain images of the screw hole, and the screw hole volume was measured using imaging analysis software. Direct comparison of displacements was conducted via cycle-displacement curve. Screw hole volume was analyzed using analysis of variance. The correlation between the displacement, screw hole volume and the direction of pedicle screw was assessed by Spearman correlation analysis. RESULTS The smallest displacements were observed in the caudad group, followed by the parallel and cranial groups. The caudad group had the smallest screw hole volume (p < 0.001 and p = 0.009 compared to the cranial and parallel groups, respectively), while the volume in the parallel group was greater than that in the cranial group (p = 0.003). Correlation analysis revealed that the insertional direction of the pedicle screw was associated with the displacement (p = -0.949, p < 0.001) and screw hole volume (p = -0.944, p < 0.001). CONCLUSION Strong correlations were found between the insertional direction of the pedicle screw and relevant parameters, including displacement and screw hole volume. Pedicle screw insertion in the caudad direction resulted in the least pedicle screw loosening.
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Affiliation(s)
- Xuqiang Zhan
- Department of Spine SurgeryTongji Hospital, School of Medicine, Tongji UniversityShanghaiChina
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration, Ministry of Education, Department of Spine SurgeryTongji Hospital, School of Medicine, Tongji UniversityShanghaiChina
| | - Feng Gao
- Department of Spine SurgeryTongji Hospital, School of Medicine, Tongji UniversityShanghaiChina
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration, Ministry of Education, Department of Spine SurgeryTongji Hospital, School of Medicine, Tongji UniversityShanghaiChina
- Yuyao Maternity and Child Health Care Hospital (Yuyao Second People's Hospital)ZhejiangChina
| | - Yangyang Yang
- School of Biomedical Engineering & Med‐X Research Institute, Shanghai Jiao Tong UniversityShanghaiChina
| | - Tsung‐Yuan Tsai
- School of Biomedical Engineering & Med‐X Research Institute, Shanghai Jiao Tong UniversityShanghaiChina
| | - Zongmiao Wan
- The First Affiliated Hospital of NanChang UniversityNanchangChina
| | - Yan Yu
- Department of Spine SurgeryTongji Hospital, School of Medicine, Tongji UniversityShanghaiChina
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration, Ministry of Education, Department of Spine SurgeryTongji Hospital, School of Medicine, Tongji UniversityShanghaiChina
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Yang JX, Luo L, Liu JH, Wang N, Xi ZP, Li JC. Incomplete insertion of pedicle screws triggers a higher biomechanical risk of screw loosening: mechanical tests and corresponding numerical simulations. Front Bioeng Biotechnol 2024; 11:1282512. [PMID: 38260754 PMCID: PMC10800439 DOI: 10.3389/fbioe.2023.1282512] [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: 08/24/2023] [Accepted: 12/11/2023] [Indexed: 01/24/2024] Open
Abstract
Screw loosening is a widely reported issue after spinal screw fixation and triggers several complications. Biomechanical deterioration initially causes screw loosening. Studies have shown that incomplete insertion of pedicle screws increases the risk of screw breakage by deteriorating the local mechanical environment. However, whether this change has a biomechanical effect on the risk of screw loosening has not been determined. This study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to verify this topic. Pedicle screw-fixed polyurethane foam models with screws with four different insertion depths were constructed, and the screw anchoring ability of different models was verified by toggle tests with alternating and constant loads. Moreover, the stress distribution of screw and bone-screw interfaces in different models was computed in corresponding numerical mechanical models. Mechanical tests presented better screw anchoring ability with deeper screw insertion, but parameters presented no significant difference between groups with complete thread insertion. Correspondingly, higher stress values can be recorded in the model without complete thread insertion; the difference in stress values between models with complete thread insertion was relatively slight. Therefore, incomplete thread insertion triggers local stress concentration and the corresponding risk of screw loosening; completely inserting threads could effectively alleviate local stress concentration and result in the prevention of screw loosening.
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Affiliation(s)
- Jie-Xiang Yang
- Department of Orthopedics, The Affiliated Traditional Chinese Medicine Hospital, Southwest Medical University, Luzhou, China
- Luzhou Key Laboratory of Orthopedic Disorders, Southwest Medical University, Luzhou, Sichuan, China
| | - Lin Luo
- Department of Orthopedics, The Affiliated Traditional Chinese Medicine Hospital, Southwest Medical University, Luzhou, China
- Luzhou Key Laboratory of Orthopedic Disorders, Southwest Medical University, Luzhou, Sichuan, China
| | - Jin-Hui Liu
- Sichuan Provincial Laboratory of Orthopaedic Engineering, Department of Bone and Joint Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China
| | - Nan Wang
- Department of Orthopedics, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Zhi-Peng Xi
- Department of Orthopedics, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Jing-Chi Li
- Department of Orthopedics, The Affiliated Traditional Chinese Medicine Hospital, Southwest Medical University, Luzhou, China
- Luzhou Key Laboratory of Orthopedic Disorders, Southwest Medical University, Luzhou, Sichuan, China
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Li JC, Yang ZQ, Xie TH, Song ZT, Song YM, Zeng JC. Deterioration of the fixation segment's stress distribution and the strength reduction of screw holding position together cause screw loosening in ALSR fixed OLIF patients with poor BMD. Front Bioeng Biotechnol 2022; 10:922848. [PMID: 36110315 PMCID: PMC9468878 DOI: 10.3389/fbioe.2022.922848] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/29/2022] [Indexed: 11/16/2022] Open
Abstract
The vertebral body's Hounsfield unit (HU) value can credibly reflect patients' bone mineral density (BMD). Given that poor bone-screw integration initially triggers screw loosening and regional differences in BMD and strength in the vertebral body exist, HU in screw holding planes should better predict screw loosening. According to the stress shielding effect, the stress distribution changes in the fixation segment with BMD reduction should be related to screw loosening, but this has not been identified. We retrospectively collected the radiographic and demographic data of 56 patients treated by single-level oblique lumbar interbody fusion (OLIF) with anterior lateral single rod (ALSR) screw fixation. BMD was identified by measuring HU values in vertebral bodies and screw holding planes. Regression analyses identified independent risk factors for cranial and caudal screw loosening separately. Meanwhile, OLIF with ALSR fixation was numerically simulated; the elastic modulus of bony structures was adjusted to simulate different grades of BMD reduction. Stress distribution changes were judged by computing stress distribution in screws, bone-screw interfaces, and cancellous bones in the fixation segment. The results showed that HU reduction in vertebral bodies and screw holding planes were independent risk factors for screw loosening. The predictive performance of screw holding plane HU is better than the mean HU of vertebral bodies. Cranial screws suffer a higher risk of screw loosening, but HU was not significantly different between cranial and caudal sides. The poor BMD led to stress concentrations on both the screw and bone-screw interfaces. Biomechanical deterioration was more severe in the cranial screws than in the caudal screws. Additionally, lower stress can also be observed in fixation segments' cancellous bone. Therefore, a higher proportion of ALSR load transmission triggers stress concentration on the screw and bone-screw interfaces in patients with poor BMD. This, together with decreased bony strength in the screw holding position, contributes to screw loosening in osteoporotic patients biomechanically. The trajectory optimization of ALSR screws based on preoperative HU measurement and regular anti-osteoporosis therapy may effectively reduce the risk of screw loosening.
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Affiliation(s)
- Jing-Chi Li
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital/West China School of Medicine for Sichuan University, Chengdu, China
| | - Zhi-Qiang Yang
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital/West China School of Medicine for Sichuan University, Chengdu, China
| | - Tian-Hang Xie
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital/West China School of Medicine for Sichuan University, Chengdu, China
| | - Zhe-Tao Song
- Department of Imaging, West China Hospital, Chengdu, China
| | - Yue-Ming Song
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital/West China School of Medicine for Sichuan University, Chengdu, China
| | - Jian-Cheng Zeng
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital/West China School of Medicine for Sichuan University, Chengdu, China
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Enhancement of the bone-implant interface by applying a plasma-sprayed titanium coating on nanohydroxyapatite/polyamide66 implants in a rabbit model. Sci Rep 2021; 11:19971. [PMID: 34620967 PMCID: PMC8497622 DOI: 10.1038/s41598-021-99494-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 09/27/2021] [Indexed: 12/05/2022] Open
Abstract
Solid fusion at the bone-implant interface (BII) is considered one of the indicators of a satisfactory clinical outcome for spine surgery. Although the mechanical and physical properties of nanohydroxyapatite/polyamide66 (n-HA/PA66) offers many advantages, the results of long-term follow-up for BIIs remain limited. This study aimed to improve the BII of n-HA/PA66 by applying plasma-sprayed titanium (PST) and assessing the mechanical and histological properties. After the PST coating was applied to n-HA/PA66 implants, the coating had uneven, porous surfaces. The compression results were not significantly different between the two groups. The micro-CT results demonstrated that at 6 weeks and 12 weeks, the bone volume (BV), BV/tissue volume (TV) and trabecular number (Tb.N) values of the n-HA/PA66-PST group were significantly higher than those of the n-HA/PA66 group. The results of undecalcified bone slicing showed that more new bone appeared to form around n-HA/PA66-PST implant than around n-HA/PA66 implant. The bone-implant contact (BIC) and push-out test results of the n-HA/PA66-PST group were better than those of the n-HA/PA66 group. In conclusion, after PST coating, direct and additional new bone-to-implant bonding could be achieved, improving the BII of n-HA/PA66 implants. The n-HA/PA66-PST implants could be promising for repair purposes.
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Fleury RBC, Shimano AC, Matos TD, Teixeira KDO, Romero V, Defino HLA. The Role of Pedicle Screw Surface on Insertion Torque and Pullout Strength. Rev Bras Ortop 2020; 55:695-701. [PMID: 33364646 PMCID: PMC7748926 DOI: 10.1055/s-0040-1710072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Accepted: 02/20/2020] [Indexed: 10/31/2022] Open
Abstract
Objective Compare by mechanical tests the pullout resistance and the insertion torque of rough and smooth pedicle screws. Methods Pedicle screws with rough surface and smooth surface, with diameters of 4.8; 5.5 and 6.5 mm, were inserted in polyurethane blocks with density of 10 PCF (0.16 g/cm3). Insertion torque and pullout strength were assessed. Results The pullout strength of the rough surface and smooth surface screws did not differ, except in the group of 4.8 mm diameter screws. In this group, the rough surface screws showed greater resistance to pullout. Conclusion Pedicle screws with a rough surface did not show increased pullout resistance in the acute phase of their insertion in polyurethane blocks compared to smooth surface screws. The rough surface screws had a higher insertion torque than the smooth surface screws, depending on the diameter of the screw and the preparation of the pilot hole.
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Affiliation(s)
- Rodrigo Barra Caiado Fleury
- Curso de Pós-Graduação, Departamento de Biomecânica, Medicina e Reabilitação do Aparelho Locomotor, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - Antônio Carlos Shimano
- Departamento de Biomecânica, Medicina e Reabilitação do Aparelho Locomotor, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - Thiago Dantas Matos
- Curso de Pós-Graduação, Departamento de Biomecânica, Medicina e Reabilitação do Aparelho Locomotor, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - Kelsen de Oliveira Teixeira
- Curso de Pós-Graduação, Departamento de Biomecânica, Medicina e Reabilitação do Aparelho Locomotor, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - Valéria Romero
- Departamento de Clínica Médica, Faculdade de Ciências Médicas da Universidade Estadual de Campinas, Campinas, SP, Brasil
| | - Helton Luiz Aparecido Defino
- Departamento de Biomecânica, Medicina e Reabilitação do Aparelho Locomotor da Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, São Paulo, SP, Brasil
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Novel augmentation technique of percutaneous pedicle screw fixation using hydroxyapatite granules in the osteoporotic lumbar spine: a cadaveric biomechanical analysis. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2020; 30:71-78. [PMID: 32424638 DOI: 10.1007/s00586-020-06451-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 04/05/2020] [Accepted: 05/05/2020] [Indexed: 10/24/2022]
Abstract
PURPOSE Percutaneous pedicle screw (PPS) fixation has been commonly used for various spine surgeries. Rigid PPS fixation is necessary to decrease the incidence of screw loosening in osteoporotic spine. Recently, we have reported biomechanical advantages of augmentation technique using hydroxyapatite (HA) granules for PPS fixation in synthetic bone. However, its biomechanical performance in augmenting PPS fixation for osteoporotic spine has not been fully elucidated. The aim of the present study is to perform a cadaveric biomechanical analysis of PPS fixation augmented with HA granules. METHODS Thirty osteoporotic lumbar vertebrae (L1-L5) were obtained from 6 cadavers (3 men and 3 women; age 80 ± 9 years; bone mineral density 73 ± 9 mg/cm3). The maximal pullout strength and maximal insertion torque were compared between the screws inserted into the vertebrae with and without augmentation. In toggle testing, the number of craniocaudal toggle cycles and maximal load required to achieve the 2-mm screw head displacement were also compared. RESULTS The maximal pullout strength in the screws augmented with HA granules was significantly greater compared to those without augmentation (p < 0.05). The augmentation significantly increased the maximal insertion torque of the screws (p < 0.05). Moreover, the number of toggle cycles and the maximal load required to reach 2 mm of displacement were significantly higher in the augmented screws (p < 0.05). CONCLUSION The PPS fixation was significantly enhanced by the augmentation with HA granules in the osteoporotic lumbar spine. The PPS fixation augmented with HA granules might decrease the incidence of screw loosening and implant failure in patients with osteoporotic spine.
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