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Sadeghpour A, Mahdipour S, Ghanjpour Sales J, Aslani H, Moharrami MR, Alizadeh H. Non-cannulated versus cannulated cancellous screws for the internal fixation of femoral neck fractures in osteoporotic patients: A single-blind randomized clinical trial. J Orthop 2024; 51:32-38. [PMID: 38299065 PMCID: PMC10825919 DOI: 10.1016/j.jor.2023.11.074] [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: 07/11/2023] [Revised: 11/26/2023] [Accepted: 11/28/2023] [Indexed: 02/02/2024] Open
Abstract
Background The incidence of femoral neck fractures in osteoporotic patients is rising worldwide and is associated with significant increases in healthcare and social costs, as well as dependency. Improving minimally invasive treatment strategies, including internal fixation with screws, can result in favorable clinical outcomes and lesser incidence of complications, while preserving the hip. This study compared the outcomes of using non-cannulated cancellous screws (NCS) and cannulated cancellous screws (CS) in the internal fixation of undisplaced intracapsular femoral neck fractures (UIFNF) of osteoporotic patients of Iranian descent. Methods This randomized clinical trial was conducted on the patients referring to an institutional tertiary hospital in northwestern Iran between March 2020 and June 2021. The patients' preoperative, perioperative, and postoperative characteristics were evaluated for at least two years. Primary endpoints were defined as the incidence of hip-related complications, while secondary endpoints were assessed based on the patients' hip function using Harris Hip Score (HHS). Results Fifty-seven patients with osteoporosis and UIFNF were included in the final analysis, with 27 patients in the NCS group and 30 patients in the CS group. The surgical duration, the amount of intraoperative blood loss, and the frequency of C-arm were considerably lower in the CS group (p < 0.05). The incidence of implant failure was higher in the NCS group (p = 0.04). Screw migration occurred more frequently in the CS group (p = 0.03). The HHS values were significantly higher for the NCS group than those of the CS group at both the 1-year and 2-years of follow-up assessments (1 year, p = 0.007; 2 years, p = 0.001). Conclusion Fixation using CS was accompanied by enhanced perioperative outcomes and lower implant failure rates compared to the NCS group. However, patients in the NCS group posed a reduced risk of complications, including screw migration, and experienced a long-term improvement in HHS scores.
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Affiliation(s)
- Alireza Sadeghpour
- Department of Orthopedic Surgery, Shohada Educational Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Shahab Mahdipour
- Department of Orthopedic Surgery, Shohada Educational Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Jafar Ghanjpour Sales
- Department of Orthopedic Surgery, Shohada Educational Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Hossein Aslani
- Department of Orthopedic Surgery, Shohada Educational Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mohammad Reza Moharrami
- Department of Orthopedic Surgery, Shohada Educational Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Hadi Alizadeh
- Department of Orthopedic Surgery, Shohada Educational Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
- Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
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Müller JU, Nowak S, Matthes M, Pillich DT, Schroeder HWS, Müller J. Biomechanical comparison of two different compression screws for the treatment of odontoid fractures in human dens axis specimen. Clin Biomech (Bristol, Avon) 2024; 111:106162. [PMID: 38159327 DOI: 10.1016/j.clinbiomech.2023.106162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 12/13/2023] [Accepted: 12/21/2023] [Indexed: 01/03/2024]
Abstract
BACKGROUND Lag screw osteosynthesis for odontoid fractures has a high rate of pseudoarthrosis, especially in elderly patients. Besides biomechanical properties of the different screw types, insufficient fragment compression or unnoticed screw stripping may be the main causing factors for this adverse event. The aim of the study was to compare two screws in clinical use with different design principles in terms of compression force and stability against screw stripping. METHODS Twelve human cadaveric C2 vertebral bodies were considered. Bone density was determined. The specimens were matched according to bone density and randomly assigned to two experimental groups. An odontoid fracture was induced, which were fixed either with a 3.5 mm standard compression screw or with a 5 mm sleeve nut screw. Both screws are certified for the treatment of odontoid fractures. The bone samples were fixed in a measuring device. The screwdriver was driven mechanically. The tests were analyzed for peak interfragmentary compression and screw-in torque with a frequency of 20 Hz. FINDINGS The maximum fragment compression was significantly higher with screw with sleeve nut at 346.13(SD ±72.35) N compared with classic compression screw at 162.68(SD ±114.13) N (p = 0.025). Screw stripping occurred significantly earlier in classic compression screw at 255.5(SD ±192.0)° rotation after reaching maximum compression than in screw with sleeve nut at 1005.2(SD ±341.1)° (p = 0.0039). INTERPRETATION Screw with sleeve nut achieves greater fragment compression and is more robust to screw stripping compared to classic compression screw. Whether the better biomechanical properties lead to a reduction of pseudoarthrosis has to be proven in clinical studies.
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Affiliation(s)
- Jan-Uwe Müller
- Department of Neurosurgery, University Medicine, Greifswald, Germany.
| | - Stephan Nowak
- Department of Neurosurgery, University Medicine, Greifswald, Germany
| | - Marc Matthes
- Department of Neurosurgery, University Medicine, Greifswald, Germany
| | | | | | - Jonas Müller
- Department of Neurosurgery, University Medicine, Greifswald, Germany
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Liu YY, Xiao J, He L, Yin X, Song L, Zhou R, Zeng J, Liu P, Dai F. Risk factor analysis of bone cement leakage for polymethylmethacrylate-augmented cannulated pedicle screw fixation in spinal disorders. Heliyon 2023; 9:e15167. [PMID: 37089395 PMCID: PMC10113860 DOI: 10.1016/j.heliyon.2023.e15167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 03/25/2023] [Accepted: 03/28/2023] [Indexed: 04/05/2023] Open
Abstract
Objective To investigate the risk factors of cement leakage (CL) for polymethylmethacrylate-augmented cannulated pedicle screw (CPS) in spinal degenerative diseases and provided technical guidance for clinical surgery. Methods This study enrolled 276 patients with spinal degenerative disease and osteoporosis who were augmented using CPSs (835 screws in total) from May 2011 to June 2018 in our hospital. The patients' age, sex, bone mineral density (BMD), diagnosis, augmented positions, number of CPS implanted, and CL during surgery were recorded. CL was observed by postoperative computed tomography (CT) and was classified by Yeom typing. Results A total of 74 (74/835, 8.9%) CPSs in 64 patients leaked (64/276, 23.2%). CL was significantly correlated with the number and position of screws (P < 0.05), but not with sex, age, and BMD (P > 0.05). The position, number of CPSs, fracture, degenerative scoliosis, ankylosing spondylitis, and revision surgery were risk factors for CL (P < 0.05). Augmentation of the thoracic vertebral body, fracture, and ankylosing spondylitis were independent risk factors for Type S. Augmentation of the lumbar vertebral body, lumbar disc herniation, and lumbar spondylolisthesis were independent risk factors for Type B (P < 0.05). Conclusions CL has a high incidence in clinical practice. High-risk factors for leakage should be addressed to avoid serious complications. Particularly, it is necessary to develop alternative solutions once CPSs can't be used in surgery caused by CL.
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Affiliation(s)
- Yao-yao Liu
- Department of Spine Surgery, Daping Hospital, Army Medical Center of PLA, Chongqing, 400042, PR China
| | - Jun Xiao
- Guangzhou Rocket Force Special Service Convalescent Center, Guangzhou, 510515, PR China
| | - Lei He
- Department of Orthopedics, Southwest Hospital of Army Medical University, PLA, Chongqing, 400038, PR China
| | - Xiang Yin
- Department of Spine Surgery, Daping Hospital, Army Medical Center of PLA, Chongqing, 400042, PR China
| | - Lei Song
- Department of Orthopedics, Southwest Hospital of Army Medical University, PLA, Chongqing, 400038, PR China
| | - Rui Zhou
- Department of Orthopedics, Southwest Hospital of Army Medical University, PLA, Chongqing, 400038, PR China
| | - Jing Zeng
- Guangzhou Rocket Force Special Service Convalescent Center, Guangzhou, 510515, PR China
| | - Peng Liu
- Department of Spine Surgery, Daping Hospital, Army Medical Center of PLA, Chongqing, 400042, PR China
- Corresponding author. Department of Spine surgery, Daping Hospital, Army Medical Center of PLA, No. 10 Changjiang Road, Yuzhong District, Chongqing, 400042, PR China.
| | - Fei Dai
- Department of Orthopedics, Southwest Hospital of Army Medical University, PLA, Chongqing, 400038, PR China
- Corresponding author. Department of Orthopedics, Southwest Hospital of Army Medical University, PLA, No. 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, PR China.
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Feng X, Zhang S, Luo Z, Liang H, Chen B, Leung F. Development and initial validation of a novel thread design for nonlocking cancellous screws. J Orthop Res 2022; 40:2813-2821. [PMID: 35267202 DOI: 10.1002/jor.25305] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/20/2022] [Accepted: 02/21/2022] [Indexed: 02/04/2023]
Abstract
High failure rates have been associated with nonlocking cancellous screws with a typical buttress thread in patients with osteoporotic bone. This study aimed to develop a novel thread design and compare its fixation stability with that of a typical buttress thread. Nonlocking cancellous screws with a novel thread design (proximal flank angle of 120 degrees, a flat crest feature, a tip-facing undercut feature) and nonlocking cancellous screws with a typical buttress thread were manufactured using stainless steel. Fixation stabilities were evaluated individually by the axial pullout and lateral migration tests, and they were evaluated in pairs together with a dynamic compression plate in an osteoporotic bone substitute (10 PCF polyurethane foam per ASTM F1839) under cyclic craniocaudal and torsional loadings. Pullout strength and lateral migration resistance for the individual screw test and the force, torque, and number of cycles required to achieve specific displacement and torsion for the multi-screw test were comparatively analyzed between both screw types. A finite element analysis model was constructed to analyze the stress distributions in the bone tissue adjacent to the threads. The biomechanical test revealed the novel undercut thread had superior axial pullout strength, lateral migration resistance, and superior fixation stability when applied to a dynamic compression plate under cyclic craniocaudal loading and torsional loading than those in the typical buttress thread. The finite element analysis simulation revealed that the novel thread can distribute stress more evenly without high-stress concentration at the adjacent bone tissue when compared to that of a typical buttress thread.
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Affiliation(s)
- Xiaoreng Feng
- Department of Orthopaedics and Traumatology, Yangjiang People's Hospital, Yangjiang, China.,Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Guangzhou, China
| | - Sheng Zhang
- Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Guangzhou, China
| | - Zhaopei Luo
- Department of Orthopaedics and Traumatology, Yangjiang People's Hospital, Yangjiang, China
| | - Hongfeng Liang
- Department of Orthopaedics and Traumatology, Yangjiang People's Hospital, Yangjiang, China
| | - Bin Chen
- Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Guangzhou, China
| | - Frankie Leung
- Department of Orthopaedics and Traumatology, Queen Mary Hospital, The University of Hong Kong, Pok Fu Lam, Hong Kong
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Song L, Xiao J, Zhou R, Li CC, Zheng TT, Dai F. Clinical evaluation of the efficacy of a new bone cement-injectable cannulated pedicle screw in the treatment of spondylolysis-type lumbar spondylolisthesis with osteoporosis: a retrospective study. BMC Musculoskelet Disord 2022; 23:951. [PMID: 36329431 PMCID: PMC9632048 DOI: 10.1186/s12891-022-05904-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 10/21/2022] [Indexed: 11/06/2022] Open
Abstract
Purpose To investigate the clinical efficacy and safety of a bone cement-injectable cannulated pedicle screw (CICPS) in the treatment of spondylolysis-type lumbar spondylolisthesis with osteoporosis. Methods A retrospective study was conducted on 37 patients (Dual-energy X-ray bone density detection showed different degrees of osteoporosis) with spondylolysis-type lumbar spondylolisthesis who underwent lumbar spondylolisthesis reduction and fusion using a new type of injectable bone cement screw from May 2011 to March 2015. Postoperative clinical efficacy was evaluated by the Visual Analogue Scale (VAS) scores and the Oswestry Disability Index (ODI). Imaging indexes were used to evaluate the stability of internal fixation of the devices 1, 3, 6, and 12 months after surgery and annually thereafter. The safety of the CICPS was assessed by the prevalence of intraoperative and postoperative complications. Results A total of 124 CICPS were implanted intraoperatively. Bone cement leakage occurred in 3 screws (2.42%), and no clinical discomfort was found in any patients. All 37 patients were followed up with an average follow-up time of 26.6 ± 13.4 months (12–58 months). In the evaluation of the clinical effects of the operation, the average postoperative VAS score of the patients decreased from 4.30 ± 1.58 before surgery to 0.30 ± 0.70 after surgery (P < 0.001), and the ODI decreased from 47.27% ± 16.97% before surgery to 3.36% ± 5.70% after surgery (P < 0.001). No screw was loose, broken or pulled out. Conclusion CICPS is safe and effective in the treatment of spondylolysis-type lumbar spondylolisthesis complicated by osteoporosis.
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Affiliation(s)
- Lei Song
- Department of Orthopaedics, First Affiliated Hospital, Army Medical University, Chongqing, 400038, People's Republic of China
| | - Jun Xiao
- Department of Special Service Physiological Training, Guangzhou Special Service Recuperation Center of PLA Rocket Force, Guangzhou, 515515, People's Republic of China
| | - Rui Zhou
- Department of Orthopaedics, First Affiliated Hospital, Army Medical University, Chongqing, 400038, People's Republic of China
| | - Cong-Can Li
- Department of Orthopaedics, First Affiliated Hospital, Army Medical University, Chongqing, 400038, People's Republic of China
| | - Ting-Ting Zheng
- Department of Orthopaedics, First Affiliated Hospital, Army Medical University, Chongqing, 400038, People's Republic of China.
| | - Fei Dai
- Department of Orthopaedics, First Affiliated Hospital, Army Medical University, Chongqing, 400038, People's Republic of China.
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Weidling M, Heilemann M, Schoenfelder S, Heyde CE. Influence of thread design on anchorage of pedicle screws in cancellous bone: an experimental and analytical analysis. Sci Rep 2022; 12:8051. [PMID: 35577852 PMCID: PMC9110386 DOI: 10.1038/s41598-022-11824-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 04/28/2022] [Indexed: 11/12/2022] Open
Abstract
Threads of modern pedicle screws can vary greatly in design. It is difficult to assess which interplay of design features is particularly advantageous for screw anchorage. This study aims to increase the understanding of the anchorage behaviour between screw and cancellous bone. Pull-out tests of six pedicle screws in two sizes each were performed on three densities of biomechanical test material. More general screw characteristics were derived from the screw design and evaluated using the test data. Selected screws were tested on body donor material. Some screw characteristics, such as compacting, are well suited to compare the different thread designs of screws with tapered core. The combination of two characteristics, one representing bone compacting and one representing thread flank area, appears to be particularly advantageous for assessing anchorage behaviour. With an equation derived from these characteristics, the pull-out strength could be calculated very accurately (mean deviation 1%). Furthermore, findings are corroborated by tests on donor material. For screws with tapered core, the design demands for good anchorage against pull-out from cancellous bone change with material density. With sufficient bone quality, screws with a high compacting effect are advantageous, while with low bone density a high thread flank area also appears necessary for better screw anchorage.
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Recommendations for standardised screw pull-out from polyurethane foam - The influence of density variations of the test foam and the insertion method. Med Eng Phys 2022; 100:103750. [DOI: 10.1016/j.medengphy.2022.103750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 12/07/2021] [Accepted: 01/01/2022] [Indexed: 12/18/2022]
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8
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Zhan S, Jiang D, Ling M, Ding J, Yang K, Duan L, Tsai TY, Feng Y, van Trigt B, Jia W, Zhang C, Hu H. Fixation effects of different types of cannulated screws on vertical femoral neck fracture: A finite element analysis and experimental study. Med Eng Phys 2021; 97:32-39. [PMID: 34756336 DOI: 10.1016/j.medengphy.2021.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 12/21/2022]
Abstract
Femoral neck fractures (FNFs) in young patients usually result from high-energy violence, and the vertical transcervical type is typically challenging for its instability. FNFs are commonly treated with three cannulated screws (CS), but the role of screws type on fixation effects (FE) is unclear. The purpose of this study was to evaluate the FE of ten types of CS with different diameters, lengths, depths, and pitches of thread via finite element analysis which was validated by a biomechanical test. Ten vertical FNF models were grouped, fixed by ten types of CS, respectively, all in a parallel, inverted triangular configuration. Their FE were scored comprehensively from six aspects via an entropy evaluation method, as higher scores showed better results. For partial-thread screws, thread length and thread shape factor (TSF) are determinative factors on stability of FNF only if thread depth is not too thick, and they have less cut-out risk, better compression effects and better detached resistance of fracture than full-thread screws, whereas full-thread screws appear to have better shear and shortening resistance. A combination of two superior partial-thread screws and one inferior full-thread screw for vertical FNF may get optimal biomechanical outcomes. The type of cannulated screw is important to consider when treating vertical FNF.
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Affiliation(s)
- Shi Zhan
- Biomechanical Laboratory of Orthopedic Surgery Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China
| | - Dajun Jiang
- Biomechanical Laboratory of Orthopedic Surgery Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China
| | - Ming Ling
- Biomechanical Laboratory of Orthopedic Surgery Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China
| | - Jian Ding
- Department of Orthopedic Surgery, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China
| | - Kai Yang
- Radiology Department, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China
| | - Lei Duan
- State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean & Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China
| | - Tsung-Yuan Tsai
- Engineering Research Center of Clinical Translational Digital Medicine, Ministry of Education of P.R. China, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200030, PR China
| | - Yong Feng
- Biomechanical Laboratory of Orthopedic Surgery Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China
| | - Bart van Trigt
- Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 4, 2628 CD Delft, the Netherlands
| | - Weitao Jia
- Department of Orthopedic Surgery, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China.
| | - Changqing Zhang
- Biomechanical Laboratory of Orthopedic Surgery Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China.
| | - Hai Hu
- Biomechanical Laboratory of Orthopedic Surgery Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China.
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Sayyed-Hosseinian SH, Bagheri F, Ebrahimzadeh MH, Moradi A, Golshan S. Comparison of Partially Threaded and Fully Threaded 4mm Cancellous Screws in Fixation of Medial Malleolar Fractures. THE ARCHIVES OF BONE AND JOINT SURGERY 2020; 8:710-715. [PMID: 33313352 DOI: 10.22038/abjs.2020.46112.2263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background Several devices have been described for fixation of displaced medial malleolar fractures. Fully threaded cancellous screws engaging the bone may provide advantages compared to partially threaded screws. This study was designed to compare the clinical results of fully and partially threaded 4 millimeter cancellous screws in fixation of medial malleolar fractures. Methods In a randomized clinical trial study 44 patients with displaced closed medial malleolar fractures were randomly divided into two groups. Two fully threaded four millimeter cancellous screws were used for fracture stabilization (FT group) in the first group, while, the second group was operated by use of two partially threaded four millimeter cancellous screws (PT group). The clinical outcomes and complications were compared in two groups at one year follow up. Results Nineteen patients in FT group and 21 in PT group were present at final follow up. Nonunion was not developed in either group but two cases (9%) of delayed union occurred in PT group. The rate of postoperative infection and symptomatic hardware were not statistically different. Functional assessment using AOFAS, MOXFQ and VAS scores showed no significant difference between the two groups. Conclusion Both fully and partially threaded 4 mm cancellous screws can be considered as acceptable devices for the fixation of medial malleolar fractures with good and comparable clinical results.
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Affiliation(s)
| | - Farshid Bagheri
- Orthopedic Research Center, Shahid Kamyab Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
| | | | - Ali Moradi
- Orthopedic Research Center Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Sogol Golshan
- Orthopedic Research Center, Shahid Kamyab Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
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Müller JU, Müller J, Marx S, Matthes M, Nowak S, Schroeder HWS, Pillich DT. Biomechanical comparison of three different compression screws for treatment of odontoid fractures evaluation of a new screw design. Clin Biomech (Bristol, Avon) 2020; 77:105049. [PMID: 32497928 DOI: 10.1016/j.clinbiomech.2020.105049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/12/2020] [Accepted: 05/15/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND Lag screw osteosynthesis in odontoid fractures shows a high rate of pseudarthrosis. Biomechanical properties may play a role with insufficient fragment compression or unnoticed screw stripping. A biomechanical comparison of different constructed lag-screws was carried out and the biomechanical properties determined. METHODS Two identical compression screws with different pilot holes (1.25 and 2.5 mm), a double-threaded screw and one sleeve-nut-screw were tested on artificial bone (Sawbone, densities 10-30pcf). Fragment compression and torque were continuously measured using thin-film force sensors (Flexiforce A201, Tekscan) and torque sensors (PCE-TM 80, PCE GmbH). FINDINGS The lowest compression reached the double-threaded screw. Compression and sleeve-nut-screw achieved 214-298% and 325-546%, respectively, of the compression force of double-threaded-screw, depending on the test material. The pilot hole optimization led to a significant improvement in compression only in the densest test material. Screw stripping took place significantly later with increasing density of the test material on all screws. In compression screws this was done at a screw rotation of 180-270°, in sleeve nut screw at 270-720° and in double-threaded screws at 300-600° after reaching the maximum compression. INTERPRETATION Double-threaded screw is robust against screw stripping, but achieves only low fragment compression. The classic compression screws achieve better compression, but are sensitive to screw stripping. Sleeve-nut screw is superior in compression and as robust as double-threaded screw against screw stripping. Whether the better biomechanical properties lead to a reduction in pseudarthrosis must be proven in clinical trials.
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Affiliation(s)
- Jan-Uwe Müller
- Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany.
| | - Jonas Müller
- Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
| | - Sascha Marx
- Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
| | - Marc Matthes
- Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
| | - Stephan Nowak
- Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
| | | | - Dirk Thomas Pillich
- Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
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A novel parameter for the prediction of pedicle screw fixation in cancellous bone - A biomechanical study on synthetic foam. Med Eng Phys 2020; 79:44-51. [DOI: 10.1016/j.medengphy.2020.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 01/17/2020] [Accepted: 03/01/2020] [Indexed: 11/21/2022]
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12
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Choi YY, Rhee SJ, Jeong JY. Transient retrograde interfragmentary compression technique in AO/OTA type 33-C distal femur fractures: A surgical technique and short-term radiographic follow up results. Injury 2018; 49:1617-1622. [PMID: 29884320 DOI: 10.1016/j.injury.2018.06.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 06/02/2018] [Indexed: 02/02/2023]
Abstract
Surgical treatment of AO/OTA type 33-C fractures is a therapeutic challenge despite advances in surgical instruments and techniques. We introduce a novel surgical technique named transient retrograde interfragmentary compression (TRIC) to help intraarticular fragment reduction in AO/OTA type 33-C fracture. We inserted a partial threaded 7.0-cannulated screw with a washer along the transepicondylar axis from the medial femoral epicondyle during the articular block reduction process of AO/OTA type 33-C fractures to strengthen the compressive force between the condylar fragments and to enhance the handling of the articular block fragment in the alignmental correction stage. Following the provisional reduction and fixation using lateral distal femur locking compression plate, TRIC screw was removed. Fifteen AO/OTA type 33-C distal femoral intraarticular fractures of thirteen patients were surgically treated using the TRIC technique. We analyzed the radiographic result of the patients by measuring the horizontal gap and vertical step-off in the postoperative radiographs. Mean horizontal fracture gap was 0.34 mm and mean vertical step-off between bicondylar fragments was 0.63 mm. The median value of the horizontal fracture gap and vertical step off was 0 and 0.46 mm, respectively. Mean time to union in the bicondylar fracture fragment was 9 week. TRIC is considered to be a valuable surgical reduction technique in the treatment of the AO/OTA 33-C type fractures.
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Affiliation(s)
- Yoon Young Choi
- Department of Diagnostic Radiology, Pusan National University Yangsan Hospital, Yangsan, Republic of Korea
| | - Seung Joon Rhee
- Department of Orthopedic Surgery, Biomedical Research Institute, Pusan National University Hospital, Busan, Republic of Korea.
| | - Jae Yoon Jeong
- Department of Orthopedic Surgery, Biomedical Research Institute, Pusan National University Hospital, Busan, Republic of Korea
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13
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van Arkel RJ, Ghouse S, Milner PE, Jeffers JRT. Additive manufactured push-fit implant fixation with screw-strength pull out. J Orthop Res 2018; 36:1508-1518. [PMID: 29023901 PMCID: PMC6175131 DOI: 10.1002/jor.23771] [Citation(s) in RCA: 17] [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: 06/05/2017] [Accepted: 10/01/2017] [Indexed: 02/04/2023]
Abstract
Additive manufacturing offers exciting new possibilities for improving long-term metallic implant fixation in bone through enabling open porous structures for bony ingrowth. The aim of this research was to investigate how the technology could also improve initial fixation, a precursor to successful long-term fixation. A new barbed fixation mechanism, relying on flexible struts was proposed and manufactured as a push-fit peg. The technology was optimized using a synthetic bone model and compared with conventional press-fit peg controls tested over a range of interference fits. Optimum designs, achieving maximum pull-out force, were subsequently tested in a cadaveric femoral condyle model. The barbed fixation surface provided more than double the pull-out force for less than a third of the insertion force compared to the best performing conventional press-fit peg (p < 0.001). Indeed, it provided screw-strength pull out from a push-fit device (1,124 ± 146 N). This step change in implant fixation potential offers new capabilities for low profile, minimally invasive implant design, while providing new options to simplify surgery, allowing for one-piece push-fit components with high levels of initial stability. © 2017 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 36:1508-1518, 2018.
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Affiliation(s)
- Richard J. van Arkel
- Department of Mechanical EngineeringImperial College LondonLondonSW7 2AZUnited Kingdom
| | - Shaaz Ghouse
- Department of Mechanical EngineeringImperial College LondonLondonSW7 2AZUnited Kingdom
| | - Piers E. Milner
- Department of Mechanical EngineeringImperial College LondonLondonSW7 2AZUnited Kingdom
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Shih KS, Hou SM, Lin SC. Theoretical prediction of pullout strengths for dental and orthopaedic screws with conical profile and buttress threads. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2017; 152:159-164. [PMID: 29054257 DOI: 10.1016/j.cmpb.2017.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 06/19/2017] [Accepted: 08/07/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND AND OBJECTIVE The pullout strength of a screw is an indicator of how secure bone fragments are being held in place. Such bone-purchasing ability is sensitive to bone quality, thread design, and the pilot hole, and is often evaluated by experimental and numerical methods. Historically, there are some mathematical formulae to simulate the screw withdrawal from the synthetic bone. There are great variations in screw specifications. However, extensive investigation of the correlation between experimental and analytical results has not been reported in literature. METHODS Referring to the literature formulae, this study aims to evaluate the differences in the calculated pullout strengths. The pullout tests of the surgical screws are measured and the sawbone is used as the testing block. The absolute errors and correlation coefficients of the experimental and analytical results are calculated as the comparison baselines of the formulae. RESULTS The absolute error of the dental, traumatic, and spinal groups are 21.7%, 95.5%, and 37.0%, respectively. For the screws with a conical profile and/or tiny threads, the calculated and measured results are not well correlated. The formulae are not accurate indicators of the pullout strengths of the screws where the design parameters are slightly varied. However, the experimental and numerical results are highly correlated for the cylindrical screws. The pullout strength of a conical screw is higher than that of its counterpart, but all formulae consistently predict the opposite results. In general, the bony purchase of the buttress threads is securer than that of the symmetric thread. CONCLUSIONS An absolute error of up to 51.4% indicates the theoretical results cannot predict the actual value of the pullout strength. Only thread diameter, pitch, and depth are considered in the investigated formulae. The thread profile and shape should be formulated to modify the slippage mechanism at the bone-screw interfaces and simulate the strength change in the squeezed bones, especially for the conical screw.
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Affiliation(s)
- Kao-Shang Shih
- Department of Orthopedic Surgery, Shin Kong Wu Ho-Su Memorial Hospital, Taipei 111, Taiwan, ROC; College of Medicine, Fu Jen Catholic University, Taipei 242, Taiwan, ROC; School of Medicine, Taipei Medical University, Taipei 110, Taiwan, ROC
| | - Sheng-Mou Hou
- Department of Orthopedic Surgery, Shin Kong Wu Ho-Su Memorial Hospital, Taipei 111, Taiwan, ROC
| | - Shang-Chih Lin
- Graduate Institute of Biomedical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC.
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Asnis S, Mullen J, Asnis PD, Sgaglione N, LaPorta T, Grande DA, Chahine NO. Biomechanical analysis of an interference screw and a novel twist lock screw design for bone graft fixation. Clin Biomech (Bristol, Avon) 2017; 50:99-104. [PMID: 29055245 DOI: 10.1016/j.clinbiomech.2017.10.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2017] [Revised: 10/03/2017] [Accepted: 10/06/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND Malpositioning of an anterior cruciate ligament graft during reconstruction can occur during screw fixation. The purpose of this study is to compare the fixation biomechanics of a conventional interference screw with a novel Twist Lock Screw, a rectangular shaped locking screw that is designed to address limitations of graft positioning and tensioning. METHODS Synthetic bone (10, 15, 20lb per cubic foot) were used simulating soft, moderate, and dense cancellous bone. Screw push-out and graft push-out tests were performed using conventional and twist lock screws. Maximum load and torque of insertion were measured. FINDINGS Max load measured in screw push out with twist lock screw was 64%, 60%, 57% of that measured with conventional screw in soft, moderate and dense material, respectively. Twist lock max load was 78% and 82% of that with conventional screw in soft and moderate densities. In the highest bone density, max loads were comparable in the two systems. Torque of insertion with twist lock was significantly lower than with conventional interference screw. INTERPRETATION Based on geometric consideration, the twist lock screw is expected to have 35% the holding power of a cylindrical screw. Yet, results indicate that holding power was greater than theoretical consideration, possibly due to lower friction and lower preloaded force. During graft push out in the densest material, comparable max loads were achieved with both systems, suggesting that fixation of higher density bone, which is observed in young athletes that require reconstruction, can be achieved with the twist lock screw.
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Affiliation(s)
- S Asnis
- Department of Orthopaedic Surgery, LIJ Medical Center, Northwell Health, New Hyde Park, NY, USA; Department of Orthopaedic Surgery, Hofstra Northwell School of Medicine, Hempstead, NY, USA.
| | - J Mullen
- Department of Orthopaedic Surgery, LIJ Medical Center, Northwell Health, New Hyde Park, NY, USA
| | - P D Asnis
- Division of Sports Orthopaedic Surgery, Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA, USA
| | - N Sgaglione
- Department of Orthopaedic Surgery, LIJ Medical Center, Northwell Health, New Hyde Park, NY, USA; Department of Orthopaedic Surgery, Hofstra Northwell School of Medicine, Hempstead, NY, USA
| | - T LaPorta
- Department of Orthopaedic Surgery, LIJ Medical Center, Northwell Health, New Hyde Park, NY, USA
| | - D A Grande
- Department of Orthopaedic Surgery, LIJ Medical Center, Northwell Health, New Hyde Park, NY, USA; Department of Orthopaedic Surgery, Hofstra Northwell School of Medicine, Hempstead, NY, USA; Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY, USA
| | - N O Chahine
- Department of Orthopedic Surgery and Biomedical Engineering, Columbia University, New York, NY, USA
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Albanese K, Ordway NR, Albanese SA, Lavelle WF. Effect of Pedicle Fill on Axial Pullout Strength in Spinal Fixation After Rod Reduction. Orthopedics 2017; 40:e990-e995. [PMID: 28968476 DOI: 10.3928/01477447-20170925-02] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 08/08/2017] [Indexed: 02/03/2023]
Abstract
Rod reduction to pedicle screws is used for a variety of spinal fixation procedures; however, it can alter the integrity of the screw-bone interface. The authors investigated the effect of pedicle fill (ratio of pedicle screw diameter to pedicle diameter) on the strength of the screw-bone interface after simulated rod reduction on 17 vertebrae (3 thoracolumbar spine specimens). Pedicle diameter was measured with standard clinical computed tomography scan protocols. The authors determined the minimum pedicle diameter for each level. Polyaxial pedicle screws were surgically placed bilaterally with a freehand technique with standard clinical anatomic landmarks. The pedicle pairs were instrumented with pedicle screws of predetermined diameter, 1 with greater than 80% fill and 1 with less than 80% fill. A simulated reduction maneuver was performed with a 5-mm gap followed by an axial pullout test to assess screw interface strength. Comparison of insertion torque between less than 80% fill and greater than 80% fill did not show significant increases. A significant difference in pullout load (P=.043) occurred with greater than 80% fill (791±637 N) compared with less than 80% fill (636±492 N). No significant difference in stiffness was noted (P=.154) with pedicle fill of greater than 80% (427±134 N/mm) compared with less than 80% (376±178 N/mm). The current findings support the use of greater than 80% pedicle fill for optimal screw anchoring in pedicle screw-based constructs involving rod reduction. Surgeons should consider placing screws that can safely fill vertebral pedicles, especially at the apex of the curve and the proximal and distal levels of constructs, where excessive forces are imparted to the screws. [Orthopedics. 2017; 40(6):e990-e995.].
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Interfragmentary compression and pull-out properties of 6.5-mm AO cancellous lag screws in a uniform synthetic material during tightening procedures. Med Eng Phys 2017; 42:116-120. [DOI: 10.1016/j.medengphy.2017.01.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 09/23/2016] [Accepted: 01/08/2017] [Indexed: 12/15/2022]
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Finding the right fit: studying the biomechanics of under-tapping with varying thread depths and pitches. Spine J 2017; 17:574-578. [PMID: 27916685 DOI: 10.1016/j.spinee.2016.11.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 11/16/2016] [Accepted: 11/29/2016] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Compromise of pedicle screw purchase is a concern in maintaining rigid spinal fixation, especially with osteoporosis. Little consistency exists among various tapping techniques. Pedicle screws are often prepared with taps of a smaller diameter, which can further exacerbate inconsistency. PURPOSE The objective of this study was to determine whether a mismatch between tap thread depth (D) and thread pitch (P) and screw D and P affects fixation when under-tapping in osteoporotic bone. STUDY DESIGN This study is a polyurethane foam block biomechanical analysis. MATERIALS AND METHODS A foam block osteoporotic bone model was used to compare pullout strength of pedicle screws with a 5.3 nominal diameter tap of varying D's and P's. Blocks were sorted into seven groups: (1) probe only; (2) 0.5-mm D, 1.5-mm P tap; (3) 0.5-mm D, 2.0-mm P tap; (4) 0.75-mm D, 2.0-mm P tap; (5) 0.75-mm D, 2.5-mm P tap; (6) 0.75-mm D, 3.0-mm P tap; and (7) 1.0-mm D, 2.5-mm P tap. A pedicle screw, 6.5 mm in diameter and 40 mm in length, was inserted to a depth of 40 mm. Axial pullout testing was performed at a rate of 5 mm/min on 10 blocks from each group. RESULTS No significant difference was noted between groups under axial pullout testing. The mode of failure in the probe-only group was block fracture, occurring in 50% of cases. Among the other six groups, only one screw failed because of block fracture. The other 59 failed because of screw pullout. CONCLUSIONS In an osteoporotic bone model, changing the D or P of the tap has no statistically significant effect on axial pullout. Osteoporotic bone might render tap features marginal. Our findings indicate that changing the characteristics of the tap D and P does not help with pullout strength in an osteoporotic model. The high rate of fracture in the probe-only group might imply the potential benefit of tapping to prevent catastrophic failure of bone.
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Varghese V, Ramu P, Krishnan V, Saravana Kumar G. Pull out strength calculator for pedicle screws using a surrogate ensemble approach. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2016; 137:11-22. [PMID: 28110717 DOI: 10.1016/j.cmpb.2016.08.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 08/16/2016] [Accepted: 08/29/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND AND OBJECTIVE Pedicle screw instrumentation is widely used in the treatment of spinal disorders and deformities. Currently, the surgeon decides the holding power of instrumentation based on the perioperative feeling which is subjective in nature. The objective of the paper is to develop a surrogate model which will predict the pullout strength of pedicle screw based on density, insertion angle, insertion depth and reinsertion. METHODS A Taguchi's orthogonal array was used to design an experiment to find the factors effecting pullout strength of pedicle screw. The pullout studies were carried using polyaxial pedicle screw on rigid polyurethane foam block according to American society for testing of materials (ASTM F543). Analysis of variance (ANOVA) and Tukey's honestly significant difference multiple comparison tests were done to find factor effect. Based on the experimental results, surrogate models based on Krigging, polynomial response surface and radial basis function were developed for predicting the pullout strength for different combination of factors. An ensemble of these surrogates based on weighted average surrogate model was also evaluated for prediction. RESULTS Density, insertion depth, insertion angle and reinsertion have a significant effect (p <0.05) on pullout strength of pedicle screw. Weighted average surrogate performed the best in predicting the pull out strength amongst the surrogate models considered in this study and acted as insurance against bad prediction. CONCLUSIONS A predictive model for pullout strength of pedicle screw was developed using experimental values and surrogate models. This can be used in pre-surgical planning and decision support system for spine surgeon.
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Affiliation(s)
- Vicky Varghese
- Department of Biotechnology, Indian Institute of Technology Madras, Chennai, Tamil Nadu, India
| | - Palaniappan Ramu
- Department of Engineering Design, Indian Institute of Technology Madras, Chennai, Tamil Nadu, India
| | - Venkatesh Krishnan
- Spinal Disorder Surgery Unit, Department of Orthopedics, Christian Medical College, Vellore, Tamil Nadu, India
| | - Gurunathan Saravana Kumar
- Department of Engineering Design, Indian Institute of Technology Madras, Chennai, Tamil Nadu, India.
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Salduz A, Birisik F, Polat G, Bekler B, Bozdag E, Kilicoglu O. The effect of screw thread length on initial stability of Schatzker type 1 tibial plateau fracture fixation: a biomechanical study. J Orthop Surg Res 2016; 11:146. [PMID: 27876042 PMCID: PMC5120498 DOI: 10.1186/s13018-016-0484-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 11/14/2016] [Indexed: 11/13/2022] Open
Abstract
Background This study compares the cyclic loading properties and failure loads of two screw combinations on a synthetic Schatzker type 1 tibia fracture model. Our hypothesis was that after adequate compression with first a partially threaded screw, addition of a fully threaded screw would provide more stability than an addition of a second partially threaded screw. Methods The Schatzker type 1 tibial plateau fracture model was created. Fixation was obtained in group A (n = 10) with two partially threaded screws and in group B (n = 10) with one fully threaded screw and one partially threaded screw. Load-displacement evaluation was made at each 1000-cycle interval up to 10,000 cycles. Failure load was identified as the load creating a 2-mm displacement. Two-factor (groups and periods) repeated measurement analysis of variance and independent sample t tests were used. Results According to the two-factor repeated analysis, there was no significant difference for periods (p = 0.29) and time-period interaction (p = 0.59) (Wilk’s Lambda F value, 1.507 and 0.871, respectively). In the test of between-subject effects, there was no significant difference between groups in terms of cyclic loadings (p = 0.06, F = 4.065). However, in the t test for each 1000-cycle interval, the value of mean displacement in group B was significantly lower than that in group A in the initial, 1000-, 2000-, and 3000-cycle intervals (p = 0.023, 0.031, 0.025, 0.043, respectively). The mean displacement and standard deviations increased with the number of cycles. The mean range of displacement initially was 0.66 mm for group A and 0.36 mm for group B. The mean range of displacement after 10,000 cycles was 0.79 mm for group A and 0.44 mm for group B. The mean failure load value was 682 ± 234 N for group A and 835 ± 245 N for group B. In independent sample t tests, there were no significant differences between the two groups in terms of failure load (p > 0.05). Conclusions Obtaining fixation with one partially and one fully threaded screw can minimize displacement at the fracture site at early cyclic loadings.
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Affiliation(s)
- Ahmet Salduz
- Department of Orthopedic and Traumatology, Istanbul Faculty of Medicine, Istanbul University, 34093, Istanbul, Turkey.
| | - Fevzi Birisik
- Department of Orthopedic and Traumatology, Istanbul Faculty of Medicine, Istanbul University, 34093, Istanbul, Turkey
| | - Gokhan Polat
- Department of Orthopedic and Traumatology, Istanbul Faculty of Medicine, Istanbul University, 34093, Istanbul, Turkey
| | - Bugra Bekler
- Laboratory of Biomechanics and Strength of Materials, Faculty of Mechanical Engineering, Istanbul Technical University, Istanbul, Turkey
| | - Ergun Bozdag
- Laboratory of Biomechanics and Strength of Materials, Faculty of Mechanical Engineering, Istanbul Technical University, Istanbul, Turkey
| | - Onder Kilicoglu
- Department of Orthopedic and Traumatology, Istanbul Faculty of Medicine, Istanbul University, 34093, Istanbul, Turkey
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Behrbalk E, Uri O, Folman Y, Rickert M, Kaiser R, Boszczyk BM. Staged Correction of Severe Thoracic Kyphosis in Patients with Multilevel Osteoporotic Vertebral Compression Fractures. Global Spine J 2016; 6:710-720. [PMID: 27781192 PMCID: PMC5077718 DOI: 10.1055/s-0035-1569460] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 10/05/2015] [Indexed: 12/12/2022] Open
Abstract
Study Design Technical report. Objective Multilevel osteoporotic vertebral compression fractures may lead to considerable thoracic deformity and sagittal imbalance, which may necessitate surgical intervention. Correction of advanced thoracic kyphosis in patients with severe osteoporosis remains challenging, with a high rate of failure. This study describes a surgical technique of staged vertebral augmentation with osteotomies for the treatment of advanced thoracic kyphosis in patients with osteoporotic multilevel vertebral compression fractures. Methods Five patients (average age 62 ± 6 years) with multilevel osteoporotic vertebral compression fractures and severe symptomatic thoracic kyphosis underwent staged vertebral augmentation and surgical correction of their sagittal deformity. Clinical and radiographic outcomes were assessed retrospectively at a mean postoperative follow-up of 34 months. Results Patients' self-reported back pain decreased from 7.2 ± 0.8 to 3.0 ± 0.7 (0 to 10 numerical scale; p < 0.001). Patients' back-related disability decreased from 60 ± 10% to 29 ± 10% (0 to 100% Oswestry Disability Index; p < 0.001). Thoracic kyphosis was corrected from 89 ± 5 degrees to 40 ± 4 degrees (p < 0.001), and the sagittal vertical axis was corrected from 112 ± 83 mm to 38 ± 23 mm (p = 0.058). One patient had cement leakage without subsequent neurologic deficit. Decreased blood pressure was observed in another patient during the cement injection. No correction loss, hardware failure, or neurologic deficiency was seen in the other patients. Conclusion The surgical technique described here, despite its complexity, may offer a safe and effective method for the treatment of advanced thoracic kyphosis in patients with osteoporotic multilevel vertebral compression fractures.
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Affiliation(s)
- Eyal Behrbalk
- The Spine Unit, Hillel-Yaffe Medical Center, Hadera, Israel,Address for correspondence Dr. Eyal Behrbalk The Spine Unit, Hillel-Yaffe Medical CenterHa-Shalom Street, Hadera, 38100Israel
| | - Ofir Uri
- The Spine Unit, Hillel-Yaffe Medical Center, Hadera, Israel
| | - Yoram Folman
- The Spine Unit, Hillel-Yaffe Medical Center, Hadera, Israel
| | - Marcus Rickert
- The Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham, United Kingdom
| | - Radek Kaiser
- The Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham, United Kingdom
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Wang T, Boone C, Behn AW, Ledesma JB, Bishop JA. Cancellous Screws Are Biomechanically Superior to Cortical Screws in Metaphyseal Bone. Orthopedics 2016; 39:e828-32. [PMID: 27172369 DOI: 10.3928/01477447-20160509-01] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 03/18/2016] [Indexed: 02/03/2023]
Abstract
Cancellous screws are designed to optimize fixation in metaphyseal bone environments; however, certain clinical situations may require the substitution of cortical screws for use in cancellous bone, such as anatomic constraints, fragment size, or available instrumentation. This study compares the biomechanical properties of commercially available cortical and cancellous screw designs in a synthetic model representing various bone densities. Commercially available, fully threaded, 4.0-mm outer-diameter cortical and cancellous screws were tested in terms of pullout strength and maximum insertion torque in standard-density and osteoporotic cancellous bone models. Pullout strength and maximum insertion torque were both found to be greater for cancellous screws than cortical screws in all synthetic densities tested. The magnitude of difference in pullout strength between cortical and cancellous screws increased with decreasing synthetic bone density. Screw displacement prior to failure and total energy absorbed during pullout strength testing were also significantly greater for cancellous screws in osteoporotic models. Stiffness was greater for cancellous screws in standard and osteoporotic models. Cancellous screws have biomechanical advantages over cortical screws when used in metaphyseal bone, implying the ability to both achieve greater compression and resist displacement at the screw-plate interface. Surgeons should preferentially use cancellous over cortical screws in metaphyseal environments where cortical bone is insufficient for fixation. [Orthopedics.2016; 39(5):e828-e832.].
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Abstract
OBJECTIVES The objective of this study is to evaluate whether real-time torque feedback may reduce the occurrence of stripping when inserting nonlocking screws through fracture plates into synthetic cancellous bone. METHODS Five attending orthopaedic surgeons and 5 senior level orthopaedic residents inserted 8 screws in each phase. In phase I, screws were inserted without feedback simulating conventional techniques. In phase II, screws were driven with visual torque feedback. In phase III, screws were again inserted with conventional techniques. Comparison of these 3 phases with respect to screw insertion torque, surgeon rank, and perception of stripping was used to establish the effects of feedback. RESULTS Seventy-three of 239 screws resulted in stripping. During the first phase, no feedback was provided and the overall strip rate was 41.8%; this decreased to 15% with visual feedback (P < 0.001) and returned to 35% when repeated without feedback. With feedback, a lower average torque was applied over a narrower torque distribution. Residents stripped 40.8% of screws compared with 20.2% for attending surgeons. Surgeons were poor at perceiving whether they stripped. CONCLUSIONS Prevention and identification of stripping is influenced by surgeon perception of tactile sensation. This is significantly improved with utilization of real-time visual feedback of a torque versus roll curve. This concept of real-time feedback seems beneficial toward performance in synthetic cancellous bone and may lead to improved fixation in cancellous bone in a surgical setting.
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Tensmeyer DF, Gustafson PA, Jastifer JR, Patel B, Chess JL. The effect of load obliquity on the strength of locking and nonlocking constructs in synthetic osteoporotic bone. Med Eng Phys 2015; 37:1047-52. [DOI: 10.1016/j.medengphy.2015.08.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 08/04/2015] [Accepted: 08/12/2015] [Indexed: 11/26/2022]
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Bastian JD, Bergmann M, Schwyn R, Keel MJB, Benneker LM. Assessment of the Breakaway Torque at the Posterior Pelvic Ring in Human Cadavers. J INVEST SURG 2015; 28:328-33. [PMID: 26270866 PMCID: PMC4732422 DOI: 10.3109/08941939.2015.1016249] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Purpose: To enhance the diminished screw purchase in cancellous, osteoporotic bone following the fixation of posterior pelvic ring injuries by iliosacral screws an increased bone-implant contact area using modificated screws, techniques or bone cement may become necessary. The aim of the study was to identify sites within the pathway of iliosacral screws requiring modifications of the local bone or the design of instrumentations placed at this site. Materials and Methods: The breakaway torque was measured mechanically at the iliosacral joint (“ISJ”), the sacral lateral mass (“SLM”) and the center of the S1 (“CS1”), at a superior and an inferior site under fluoroscopic control on five human cadaveric specimens (3 female; mean age 87 years, range: 76–99) using the DensiProbe™Spine device. Results: The measured median (range) breakaway torque was 0.63 Nm (0.31–2.52) at the “iliosacral joint”, 0.14 Nm (0.05–1.22) at the “sacral lateral mass”, 0.57 Nm (0.05–1.42) at the “S1 center.” The “sacral lateral mass” breakaway torque was lower than compared to that at the “iliosacral joint” (p < .001) or “S1 center” (p < .001). The median (range) breakaway torque measured at all superior measurement points was 0.52 Nm (0.10–2.52), and 0.48 Nm (0.05–1.18) at all inferior sites. The observed difference was statistically significant (p < .05). Conclusions: The lateral mass of the sacrum provides the lowest bone quality for implant anchorage. Iliosacral screws should be placed as superior as safely possible, should bridge the iliosacral joint and may allow for cement application at the lateral mass of the sacrum through perforations.
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Affiliation(s)
| | | | | | | | - Lorin Michael Benneker
- a Department of Orthopaedic and Trauma Surgery, Inselspital , University of Bern , Switzerland
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Undertapping of Lumbar Pedicle Screws Can Result in Tapping With a Pitch That Differs From That of the Screw, Which Decreases Screw Pullout Force. Spine (Phila Pa 1976) 2015; 40:E729-34. [PMID: 25856261 DOI: 10.1097/brs.0000000000000922] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Survey of spine surgeons and biomechanical comparison of screw pullout forces. OBJECTIVE To investigate what may be a suboptimal practice regularly occurring in spine surgery. SUMMARY OF BACKGROUND DATA In order for a tap to function in its intended manner, the pitch of the tap should be the same as the pitch of the screw. Undertapping has been shown to increase the pullout force of pedicle screws compared with line-to-line tapping. However, given the way current commercial lumbar pedicle screw systems are designed, undertapping may result in a tap being used that has a different pitch from that of the screw (incongruent pitch). METHODS A survey asked participants questions to estimate the proportion of cases each participant performed in the prior year using various hole preparation techniques. Participant responses were interpreted in the context of manufacturing specifications of specific instrumentation systems. Screw pullout forces were compared between undertapping with incongruent pitch and undertapping with congruent pitch using 0.16 g/cm polyurethane foam block and 6.5-mm screws. RESULTS Of the 3679 cases in which participants reported tapping, participants reported line-to-line tapping in 209 cases (5%), undertapping with incongruent pitch in 1156 cases (32%), and undertapping with congruent pitch in 2314 cases (63%). The mean pullout force for undertapping with incongruent pitch was 56 N (8%) less than the mean pullout force for undertapping with congruent pitch. This is equivalent to 13 lb. CONCLUSION This study estimates that for about 1 out of every 3 surgical cases with tapping of lumbar pedicle screws in the United States, hole preparation is being performed by undertapping with incongruent pitch. This study also shows that undertapping with incongruent pitch results in a decrease in pullout force by 8% compared with undertapping with congruent pitch. Steps should be taken to correct this suboptimal practice. LEVEL OF EVIDENCE 3.
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Variability of the pullout strength of cancellous bone screws with cement augmentation. Clin Biomech (Bristol, Avon) 2015; 30:500-6. [PMID: 25794899 DOI: 10.1016/j.clinbiomech.2015.03.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 03/02/2015] [Accepted: 03/02/2015] [Indexed: 02/07/2023]
Abstract
BACKGROUND Orthopaedic surgeons often face clinical situations where improved screw holding power in cancellous bone is needed. Injectable calcium phosphate cements are one option to enhance fixation. METHODS Paired screw pullout tests were undertaken in which human cadaver bone was augmented with calcium phosphate cement. A finite element model was used to investigate sensitivity to screw positional placement. FINDINGS Statistical analysis of the data concluded that the pullout strength was generally increased by cement augmentation in the in vitro human cadaver tests. However, when comparing the individual paired samples there were surprising results with lower strength than anticipated after augmentation, in apparent contradiction to the generally expected conclusion. Investigation using the finite element model showed that these strength reductions could be accounted for by small screw positional changes. A change of 0.5mm might result in predicted pullout force changes of up to 28%. INTERPRETATION Small changes in screw position might lead to significant changes in pullout strength sufficient to explain the lower than expected individual pullout values in augmented cancellous bone. Consequently whilst the addition of cement at a position of low strength would increase the pullout strength at that point, it might not reach the pullout strength of the un-augmented paired test site. However, the overall effect of cement augmentation produces a significant improvement at whatever point in the bone the screw is placed. The use of polymeric bone-substitute materials for tests may not reveal the natural variation encountered in tests using real bone structures.
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Ueno M, Sakai R, Tanaka K, Inoue G, Uchida K, Imura T, Saito W, Nakazawa T, Takahira N, Mabuchi K, Takaso M. Should we use cortical bone screws for cortical bone trajectory? J Neurosurg Spine 2015; 22:416-21. [DOI: 10.3171/2014.9.spine1484] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
OBJECT
In 2009, Santoni et al. reported cortical bone trajectory (CBT) as a method of inserting pedicle screws to obtain more solid fixation, and proposed the use of cortical trajectory screws with a more closely placed thread (cortical screws) for CBT. Since the entry trajectory in CBT differs from that in the traditional trajectory, it is unclear whether the increased strength derives from the specific trajectory or the shape of the screw thread in contact with the cortical bone. Whether the use of cortical screws is always required with CBT thus remains unclear. The authors therefore investigated the relationship between screw entry trajectory and screw thread characteristics and pullout strength in animal experiments.
METHODS
Lumbar vertebrae (L1–L4) from 4-month-old female pigs were randomly assigned to one of 4 groups, with cancellous screws or cortical screws inserted via the traditional trajectory or CBT. For pullout strength testing, the screw was pulled out vertically against the direction of insertion. Rod pullout testing (toggle testing) was also performed, and the peak breaking strength was measured.
RESULTS
The maximum pullout strength was significantly greater for CBT using cortical screws than for the traditional trajectory using cancellous screws. Pullout strength tended to be higher when cortical screws were used in both CBT and the traditional trajectory, although the difference was not significant. Toggle testing showed no significant differences among the 4 groups.
CONCLUSIONS
The specific unconventional trajectory seemed to have a major impact on the increased strength obtained with CBT.
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Affiliation(s)
- Masaki Ueno
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
| | - Rina Sakai
- Departments of 2Biomedical Engineering and
| | | | - Gen Inoue
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
| | - Kentaro Uchida
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
| | - Takayuki Imura
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
| | - Wataru Saito
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
| | - Toshiyuki Nakazawa
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
| | - Naonobu Takahira
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
- 3Rehabilitation, Kitasato University School of Allied Health Sciences, Sagamihara, Kanagawa, Japan
| | | | - Masashi Takaso
- 1Department of Orthopaedic Surgery, Kitasato University School of Medicine; and
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A comparison of conventional compression plates and locking compression plates using cantilever bending in an ilial fracture model. Vet Comp Orthop Traumatol 2014; 27:430-5. [PMID: 25345445 DOI: 10.3415/vcot-14-01-0001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 08/15/2014] [Indexed: 11/17/2022]
Abstract
OBJECTIVES The purpose of this study was to compare the stiffness, yield load, ultimate load at failure, displacement at failure, and mode of failure in cantilever bending of locking compression plates (LCP) and dynamic compression plates (DCP) in an acute failure ilial fracture model. Our hypothesis was that the LCP would be superior to the DCP for all of these biomechanical properties. METHODS Ten pelves were harvested from healthy dogs euthanatized for reasons unrelated to this study and divided into two groups. A transverse osteotomy was performed and stabilized with either a 6-hole DCP applied in compression or a 6-hole LCP. Pelves were tested in cantilever bending at 20 mm/min to failure and construct stiffness, yield load, ultimate load at failure, displacement at failure, and mode of failure were compared. RESULTS The mean stiffness of DCP constructs (193 N/mm [95% CI 121 - 264]) and of LCP constructs (224 N/mm [95% CI 152 - 295]) was not significantly different. Mean yield load of DCP constructs (900 N [95% CI 649 -1151]) and of LCP constructs (984 N [95% CI 733 -1235]) was not significantly different. No significant differences were found between the DCP and LCP constructs with respect to mode of failure, displacement at failure, or ultimate load at failure. CLINICAL SIGNIFICANCE Our study did not demonstrate any differences between DCP and LCP construct performance in acute failure testing in vitro.
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The effect of increasing pedicle screw size on thoracic spinal canal dimensions: an anatomic study. Spine (Phila Pa 1976) 2014; 39:E1195-200. [PMID: 25010092 DOI: 10.1097/brs.0000000000000514] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Anatomic study. OBJECTIVE To determine whether the thoracic spinal canal diameter decreases when the pedicle is allowed to expand with increasing screw diameter. To observe whether osseous breach occurs medially or laterally. SUMMARY OF BACKGROUND DATA Insertion of a pedicle screw that is larger in diameter than that of the native pedicle has been shown to expand the pedicle and increase biomechanical fixation strength. With this technique, there is concern for medial expansion of the pedicle causing decrease in spinal canal diameter, especially in the concavity of scoliosis, resulting in spinal cord compression. Also, large pedicle screws that are inserted correctly may still cause undetected medial bony breach during surgery. METHODS A total of 162 pedicles from 81 thoracic vertebrae (T1-T12) of 7 fresh-frozen adult cadavers were analyzed. After undertapping the pedicle by 1 mm, pedicle screws were inserted in increasing diameter (range, 4.0-9.5 mm) bilaterally until there was an osseous breach in the pedicle. A total of 938 screws were used. Transverse spinal canal diameter and pedicle circumference were measured (in millimeters) before and after each pedicle screw placement. Photographs and fluoroscopic images of representative specimens were obtained for visual assessment. RESULTS The average transverse spinal canal diameter was 17.7 mm. The average transverse canal diameter with the largest screw inserted before bony breach was detected was 17.6 mm (P = 0.92). The average diameter of the largest screw inserted before breach was 6.9 mm. Pedicle circumference increased from 41.8 mm before screw placement to 43.4 mm at maximal expansion before bony breach with the next sized screw. Twenty-eight pedicles did not break with 9.5-mm-diameter screws. There were 133 lateral and 1 medial breaches. CONCLUSION Increasing pedicle screw size caused pedicle expansion laterally but did not significantly alter transverse spinal canal dimensions. When there was an osseous breach, most were lateral (99.3%). LEVEL OF EVIDENCE N/A.
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Hughes CM, Bordush A, Robioneck B, Procter P, Brown CJ. Bone Anchors—A Preliminary Finite Element Study of Some Factors Affecting Pullout. J Med Device 2014. [DOI: 10.1115/1.4026901] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Bone anchors (or suture anchors) are used to provide attachment points for sutures to connect tissue such as tendons or ligaments to bone, and work by engaging a threaded portion—sometimes tapered—to the cancellous and/or cortical bone. Such repair is often needed after trauma, or as part of reconstructive surgery. This paper uses the finite element method to compare the pullout characteristics of one common type of bone anchor in different cancellous bone structures. Finite element models are created by using computed tomography (CT) scans of cancellous bone and building computer-aided design (CAD) models to define the cancellous bone geometry. Orthopedic surgeons will sometimes remove parts of the cortical shell and this paper also examines the mechanical effects of decortication. Furthermore, the importance of the connection between anchor and cortical layer is examined. One of the key outcomes from the model is that the coefficient of friction between bone and anchor determines potential mechanisms of pullout. The stiffness of anchors and the effect of the cortical layer are presented for different pullout angles to obtain the theoretical response. The results show the detailed modeling that includes the micro-architecture of the cancellous bone is necessary to capture the large variations that can exist.
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Affiliation(s)
- C. M. Hughes
- School of Engineering and Design, Brunel University, Uxbridge UB8 3PH, UK e-mail:
| | - A. Bordush
- Stryker Osteosynthesis, Schönkirchen 24232, Germany e-mail:
| | - B. Robioneck
- Stryker Osteosynthesis, Schönkirchen 24232, Germany e-mail:
| | - P. Procter
- Stryker Osteosynthesis, Schönkirchen 24232, Germany e-mail:
| | - C. J. Brown
- School of Engineering and Design, Brunel University, Uxbridge UB8 3PH, UK e-mail:
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Kiene J, Bogun J, Brockhaus N, Waizner K, Schulz AP, Wendlandt R. Biomechanical testing of a novel osteosynthesis plate for the ulnar coronoid process. Shoulder Elbow 2014; 6:191-9. [PMID: 27582936 PMCID: PMC4935064 DOI: 10.1177/1758573214532794] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 04/02/2014] [Indexed: 12/14/2022]
Abstract
BACKGROUND The present study aimed to biomechanically evaluate a novel locking plate intended for osteosynthesis of coronoid fracture compared to mini L-plates and cannulated screws. METHODS Biomechanical tests were performed on a fracture model in synthetic bones. Three groups, each with eight implant-bone-constructs, were analyzed in quasi-static and dynamic tests. Finally, samples were tested destructively for maximum strength. RESULTS The mean (SD) highest stiffness was measured for the novel plate [693 (18) N/mm], followed by the mini L-plate [646 (37) N/mm] and the cannulated screws [249 (113) N/mm]. During the cycling testing of the novel plate and the mini L-plate, no failures occurred, although three of the eight samples of cannulated screws failed during the test. The mean (SD) maximum strength during the destructive testing was 1333 (234) N for the novel plate, 1338 (227) N for the mini-L-plate and 459 (56) N for the cannulated screws. No statistical differences were found during the destructive testing between the two plates (p = 0.999), although statistical differences were found between both plates and the cannulated screws (p = 0.000 each). CONCLUSIONS Osteosynthesis of the coronoid process using the novel plate is mechanically similar to the mini L-plate. Both plates were superior to osteosynthesis with cannulated screws.
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Affiliation(s)
- Johannes Kiene
- J. Kiene, University Medical Center
Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, Lübeck, 23538, Germany. Tel.:
+49 451 500 6355. Fax: +49 451 500 3647
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Chatzistergos PE, Magnissalis EA, Kourkoulis SK. Numerical simulation of bone screw induced pretension: The cases of under-tapping and conical profile. Med Eng Phys 2014; 36:378-86. [DOI: 10.1016/j.medengphy.2013.12.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 11/25/2013] [Accepted: 12/08/2013] [Indexed: 10/25/2022]
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Abstract
OBJECTIVES The ability of surgeons to optimize screw insertion torque in nonlocking fixation constructs is important for stability, particularly in osteoporotic and cancellous bone. This study evaluated screw torque applied by surgeons during synthetic cancellous fixation. It evaluated the frequency with which screws were stripped by surgeons, factors associated with screw stripping, and ability of surgeons to recognize it. METHODS Ten surgeons assembled screw and plate fixation constructs into 3 densities of synthetic cancellous bone while screw insertion torque and axial force were measured. For each screw, the surgeon recorded a subjective rating as to whether or not the screw had been stripped. Screws were then advanced past stripping, and stripped screws were identified by comparing the insertion torque applied by the surgeon to the measured stripping torque. RESULTS Surgeons stripped 109 (45.4%) of 240 screws and did not recognize stripping 90.8% of the time when it occurred. The tendency to strip screws was highly variable among individual surgeons (stripping ranging from 16.7% to 83.3%, P < 0.0001) and did not correlate with synthetic bone density in the range tested (P = 0.186) nor with the ranking of surgeons as resident or attending surgeon (P = 0.437). Screws that were correctly recognized as stripped retained a mean 55.0% of maximum torque, less than when stripping was not recognized (79.6%, P = 0.005). CONCLUSIONS Surgeon perception is not reliable at preventing and detecting screw stripping at clinical torque levels in synthetic cancellous bone. Less aggressive insertion or standardized methods of insertion may improve the stability of nonlocking screw and plate constructs.
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Haase K, Rouhi G. Prediction of stress shielding around an orthopedic screw: Using stress and strain energy density as mechanical stimuli. Comput Biol Med 2013; 43:1748-57. [DOI: 10.1016/j.compbiomed.2013.07.032] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 07/13/2013] [Accepted: 07/29/2013] [Indexed: 10/26/2022]
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Brasiliense LBC, Lazaro BCR, Reyes PM, Newcomb AGUS, Turner JL, Crandall DG, Crawford NR. Characteristics of immediate and fatigue strength of a dual-threaded pedicle screw in cadaveric spines. Spine J 2013; 13:947-56. [PMID: 23602373 DOI: 10.1016/j.spinee.2013.03.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 10/13/2012] [Accepted: 03/07/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Novel dual-threaded screws are configured with overlapping (doubled) threads only in the proximal shaft to improve proximal cortical fixation. PURPOSE Tests were run to determine whether dual-threaded pedicle screws improve pullout resistance and increase fatigue endurance compared with standard pedicle screws. STUDY DESIGN/SETTING In vitro strength and fatigue tests were performed in human cadaveric vertebrae and in polyurethane foam test blocks. PATIENT SAMPLE Seventeen cadaveric lumbar vertebrae (14 pedicles) and 40 test sites in foam blocks were tested. OUTCOME MEASURES Measures for comparison between standard and dual-threaded screws were bone mineral density (BMD), screw insertion torque, ultimate pullout force, peak load at cyclic failure, and pedicular side of first cyclic failure. METHODS For each vertebral sample, dual-threaded screws were inserted in one pedicle and single-threaded screws were inserted in the opposite pedicle while recording insertion torque. In seven vertebrae, axial pullout tests were performed. In 10 vertebrae, orthogonal loads were cycled at increasing peak values until toggle exceeded threshold for failure. Insertion torque and pullout force were also recorded for screws placed in foam blocks representing healthy or osteoporotic bone porosity. RESULTS In bone, screw insertion torque was 183% greater with dual-threaded than with standard screws (p<.001). Standard screws pulled out at 93% of the force required to pull out dual-threaded screws (p=.42). Of 10 screws, five reached toggle failure first on the standard screw side, two screws failed first on the dual-threaded side, and three screws failed on both sides during the same round of cycling. In the high-porosity foam, screw insertion torque was 60% greater with the dual-threaded screw than with the standard screw (p=.005), but 14% less with the low-porosity foam (p=.07). Pullout force was 19% less with the dual-threaded screw than with the standard screw in the high-porosity foam (p=.115), but 6% greater with the dual-threaded screw in the low-porosity foam (p=.156). CONCLUSIONS Although dual-threaded screws required higher insertion torque than standard screws in bone and low density foam, dual-threaded and standard pedicle screws exhibited equivalent axial pullout and cyclic fatigue endurance. Unlike single-threaded screws, the mechanical performance of dual-threaded screws in bone was relatively independent of BMD. In foam, the mechanical performance of both types of screws was highly dependent on porosity.
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Affiliation(s)
- Leonardo B C Brasiliense
- Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd, Phoenix, AZ 85013, USA
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Er MS, Eroglu M, Altinel L. Comment on "compression screw fixation of the syndesmosis". Foot Ankle Int 2013; 34:612. [PMID: 23559619 DOI: 10.1177/1071100713483119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Antoniac I, Laptoiu D, Popescu D, Cotrut C, Parpala R. Development of Bioabsorbable Interference Screws: How Biomaterials Composition and Clinical and Retrieval Studies Influence the Innovative Screw Design and Manufacturing Processes. SPRINGER SERIES IN BIOMATERIALS SCIENCE AND ENGINEERING 2013. [DOI: 10.1007/978-1-4614-4328-5_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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A biomechanical comparison of short segment long bone fracture fixation techniques: single large fragment plate versus 2 small fragment plates. J Orthop Trauma 2012; 26:528-32. [PMID: 22377506 DOI: 10.1097/bot.0b013e318237c12d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES To determine whether using 2 small fragment plates (3.5 mm screw size) side by side is biomechanically superior to the use of 1 large fragment plate (4.5 mm screw size), in the fixation of "short segments" in long bone fractures. METHODS Fiber-filled epoxy bone surrogates were plated across 1-cm gaps with 3 different constructs. Six surrogates were fixed using 2 side-by-side 3.5-mm waisted compression plates and six 3.5-mm screws, 6 surrogates were fixed using one 4.5-mm waisted compression plate and two 4.5-mm screws, and 6 surrogates were fixed using one 3.5-mm waisted compression plate and three 3.5-mm screws. These constructs then underwent cyclic axial compression in 100-N increments until 500 N was reached. Then, they underwent cyclic cantilever bending at 2 Hz and at a 23.6 N·m moment until fatigue failure occurred. Also, a single load to failure test was performed in cantilever bending to evaluate plate strength. RESULTS The cumulative gap length change after 500 cycles of loading up to 500 N was 3.4% ± 0.4% for the 3.5 mm double plate construct, 9.5% ± 1.4% for the 4.5 mm single plate construct, and 14.4% ± 0.9% for the 3.5 mm single plate construct. In cantilever bending, the 3.5 mm double plate construct failed after 15,345 ± 2493 cycles, the 4.5 mm single plate construct failed after 2713 ± 1811 cycles, and the 3.5 mm single plate construct failed in its first cycle. In single load to failure testing, the load at offset yield was higher in the 3.5 mm double plate construct than the 4.5 mm single plate construct. CONCLUSIONS This study suggests that in situations where anatomy or other limitations limit the length of bone segments available for fixation, it may be preferable to use 2 small plates with more screws rather than 1 large plate with few screws.
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Gracco A, Giagnorio C, Incerti Parenti S, Alessandri Bonetti G, Siciliani G. Effects of thread shape on the pullout strength of miniscrews. Am J Orthod Dentofacial Orthop 2012; 142:186-90. [DOI: 10.1016/j.ajodo.2012.03.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 03/01/2012] [Accepted: 03/01/2012] [Indexed: 10/28/2022]
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Effect of mini-fragment fixation on the stabilization of medial malleolus fractures. J Trauma Acute Care Surg 2012; 72:948-53. [PMID: 22491610 DOI: 10.1097/ta.0b013e318249697d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Oblique fractures of the medial malleolus can arise from the application of axial force at various anatomic positions of the ankle, including supination-external rotation, pronation-external rotation, or pronation abduction. Although a variety of techniques exist to provide fixation of horizontal medial malleolus fractures, the optimal technique and pattern for internal fixation remains unclear. The aim of this study was to evaluate the mechanical properties of four different fixation methods for fractures of the medial malleolus. METHODS Identical oblique osteotomies were created in synthetic distal tibiae using a jig. The specimens were divided into four fixation groups: contoured 2.0 mm mini-fragment T-plate, figure-of-eight tension band wire, construct two parallel 4.0 mm cancellous screws, and two divergent 4.0 mm cancellous screws. The specimens were tested using offset axial tension at 10 mm/min until 2 mm of joint line displacement. RESULTS The average stiffness in tension and force at 2 mm of joint line displacement of the plate construct was significantly greater than any of the other constructs (p < 0.05), whereas the average stiffness in tension of the other three groups were not significantly different from each other (p > 0.05). CONCLUSION Using a contoured 2.0 mm mini-fragment T-plate as the method of fixation resulted in an at least 25% stiffer construct during tension and required at least 24% more force for 2 mm of joint line displacement when compared with more traditional methods of fixation in an osteotomy model of an oblique medial malleolus fracture.
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Grawe B, Le T, Williamson S, Archdeacon A, Zardiackas L. Fracture fixation with two locking screws versus three non-locking screws: A biomechanical comparison in a normal and an osteoporotic bone model. Bone Joint Res 2012; 1:118-24. [PMID: 23610681 PMCID: PMC3626198 DOI: 10.1302/2046-3758.16.2000078] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 05/18/2012] [Indexed: 11/09/2022] Open
Abstract
Objectives We aimed to further evaluate the biomechanical characteristics
of two locking screws versus three standard bicortical
screws in synthetic models of normal and osteoporotic bone. Methods Synthetic tubular bone models representing normal bone density
and osteoporotic bone density were used. Artificial fracture gaps
of 1 cm were created in each specimen before fixation with one of
two constructs: 1) two locking screws using a five-hole locking
compression plate (LCP) plate; or 2) three non-locking screws with
a seven-hole LCP plate across each side of the fracture gap. The
stiffness, maximum displacement, mode of failure and number of cycles
to failure were recorded under progressive cyclic torsional and
eccentric axial loading. Results Locking plates in normal bone survived 10% fewer cycles to failure
during cyclic axial loading, but there was no significant difference
in maximum displacement or failure load. Locking plates in osteoporotic
bone showed less displacement (p = 0.02), but no significant difference
in number of cycles to failure or failure load during cyclic axial loading
(p = 0.46 and p = 0.25, respectively). Locking plates in normal
bone had lower stiffness and torque during torsion testing (both
p = 0.03), but there was no significant difference in rotation (angular
displacement) (p = 0.84). Locking plates in osteoporotic bone showed
lower torque and rotation (p = 0.008), but there was no significant difference
in stiffness during torsion testing (p = 0.69). Conclusions The mechanical performance of locking plate constructs, using
only two screws, is comparable to three non-locking screw constructs
in osteoporotic bone. Normal bone loaded with either an axial or
torsional moment showed slightly better performance with the non-locking
construct.
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Affiliation(s)
- B Grawe
- University of Cincinnati College of Medicine, Department of Orthopaedic Surgery, PO Box 670212, 231 Albert Sabin Way, Cincinnati, Ohio 45267-0212, USA
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Mehta H, Santos E, Ledonio C, Sembrano J, Ellingson A, Pare P, Murrell B, Nuckley DJ. Biomechanical analysis of pedicle screw thread differential design in an osteoporotic cadaver model. Clin Biomech (Bristol, Avon) 2012; 27:234-40. [PMID: 22071427 DOI: 10.1016/j.clinbiomech.2011.10.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 10/03/2011] [Accepted: 10/04/2011] [Indexed: 02/07/2023]
Abstract
BACKGROUND Pedicle screw fixation, the standard surgical care for posterior stabilization in the thoraco-lumbar spine has a high rate of failure in osteoporotic individuals. Screw design factors and insertion techniques have been shown to influence the biomechanical performance of pedicle screws. Our objective was to investigate the biomechanical characteristics of pedicle screw fixation in osteoporotic bone by comparing standard screws with newly designed differential crest thickness dual lead screws. METHODS An in-vitro spinal-level paired factorial study design was used to examine thoraco-lumbar spine biomechanical outcomes for differential pedicle screw thread designs. Six cadaveric human spines (T8-L5) were tested for six groups (n=20) consisting of 2 different crest thickness and 3 different insertion techniques. Bone mineral density was assessed and peak insertion torque measured while placing one screw of new design and control on the contralateral side. Screw pullout properties were measured from classical American Society for Testing and Materials protocols. FINDINGS The screws designed specifically for osteoporotic bone showed significantly larger insertion torque compared with the standard screw design irrespective of insertion technique. Much of the variability in pullout failure and stiffness was explained by bone mineral density. The osteoporotic screws of different crest thickness were statistically similar to each other in all outcome measures. INTERPRETATION Compared with standard pedicle screws, the dual lead osteoporotic-specific pedicle screws demonstrated significantly larger insertion torques and similar pullout properties. Non-significant increased biomechanical strength was observed for thin crest compared to thick crest dual lead pedicle screws indicating their enhanced purchase in osteoporotic bone.
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Affiliation(s)
- H Mehta
- Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
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Brown CJ, Sinclair RA, Day A, Hess B, Procter P. An approximate model for cancellous bone screw fixation. Comput Methods Biomech Biomed Engin 2011; 16:443-50. [PMID: 22149043 DOI: 10.1080/10255842.2011.624516] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
This paper presents a finite element (FE) model to identify parameters that affect the performance of an improved cancellous bone screw fixation technique, and hence potentially improve fracture treatment. In cancellous bone of low apparent density, it can be difficult to achieve adequate screw fixation and hence provide stable fracture fixation that enables bone healing. Data from predictive FE models indicate that cements can have a significant potential to improve screw holding power in cancellous bone. These FE models are used to demonstrate the key parameters that determine pull-out strength in a variety of screw, bone and cement set-ups, and to compare the effectiveness of different configurations. The paper concludes that significant advantages, up to an order of magnitude, in screw pull-out strength in cancellous bone might be gained by the appropriate use of a currently approved calcium phosphate cement.
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Affiliation(s)
- C J Brown
- School of Engineering and Design, Brunel University, Uxbridge, UB8 3PH, UK.
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Optimising implant anchorage (augmentation) during fixation of osteoporotic fractures: is there a role for bone-graft substitutes? Injury 2011; 42 Suppl 2:S72-6. [PMID: 21839441 DOI: 10.1016/j.injury.2011.06.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
When stabilising a fracture the contact between the screw and the surrounding bone is crucial for mechanical strength. Through development of screws with new thread designs, as well as optimisation of other properties, improved screw purchase has been gained. Other alternatives to improve screw fixation in osteoporotic bone, as well as normal bone if needed, includes the use of various coatings on the screw that will induce a bonding between the implant surface and the bone implant, as well as application of drugs such as bisphosphonates locally in the screw hole to induce improved screw anchorage through their anticatabolic effect on the bone tissue. As failure of internal fixation of fractures in osteoporotic bone typically occurs through breakage of the bone that surrounds the implant, rather than the implant itself, an alternative strategy in osteoporotic bone can include augmentation of the bone around the screw. This is useful when screws alone are being used for fixation, as it will increase pull-out resistance, but also when conventional plates and screws are used. In angularly stable plate-screw systems, screw back-out is not a problem if the locking mechanism between the screws and the plate works. However, augmentation that will strengthen the bone around the screws can also be useful in conjunction with angle-stable plate-screw systems, as the augmentation will provide valuable support when subjected to loading that might cause cut-out. For many years conventional bone cement, polymethylmethacrylate (PMMA), has been used for augmentation, but due to side effects--including great difficulties if removal becomes necessary--the use of PMMA has never gained wide acceptance. With the introduction of bone substitutes, such as calcium phosphate cement, it has been shown that augmentation around screws can be achieved without the drawbacks seen with PMMA. When dealing with fixation of fractures in osteoporotic bone where screw stability might be inadequate, it therefore seems an attractive option to include bone substitutes for augmentation around screws as part of the armamentarium. Clinical studies now are needed to determine the indications in which bone augmentation with bone-graft substitutes (BGSs) would merit clinical usage.
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Patel PSD, Shepherd DET, Hukins DWL. The effect of screw insertion angle and thread type on the pullout strength of bone screws in normal and osteoporotic cancellous bone models. Med Eng Phys 2010; 32:822-8. [PMID: 20558097 DOI: 10.1016/j.medengphy.2010.05.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2009] [Revised: 05/10/2010] [Accepted: 05/12/2010] [Indexed: 11/24/2022]
Abstract
Screw fixation can be extremely difficult to achieve in osteoporotic (OP) bone because of its low strength. This study determined how pullout strength is affected by placing different bone screws at varying angles in normal and OP bone models. Pullout tests of screws placed axially, and at angles to the pullout axis (ranging from 10° to 40°), were performed in 0.09 g cm(-3), 0.16 g cm(-3) and 0.32 g cm(-3) polyurethane (PU) foam. Two different titanium alloy bone screws were used to test for any effect of thread type (i.e. cancellous or cortical) on the screw pullout strength. The cancellous screw required a significantly higher pullout force than the cortical screw (p<0.05). For both screws, pullout strength significantly increased with increasing PU foam density (p<0.05). For screws placed axially, and sometimes at 10°, the observed mechanism of failure was stripping of the internal screw threads generated within the PU foam by screw insertion. For screws inserted at 10°, 20°, 30° and 40°, the resistance to pullout force was observed to be by compression of the PU foam material above the angled screw; clinically, this suggests that compressed OP bone is stronger than unloaded OP bone.
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Affiliation(s)
- Purvi S D Patel
- School of Mechanical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, West Midlands, UK.
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Mechanical evaluation of a 4-mm cancellous "rescue" screw in osteoporotic cortical bone: a cadaveric study. J Orthop Trauma 2010; 24:379-82. [PMID: 20502222 DOI: 10.1097/bot.0b013e3181c29bde] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES Obtaining sufficient fracture fixation in osteoporotic bone is challenging. The purposes of the current study were (1) to compare the pullout strength of a 4-mm cancellous screw (cancellous screw group) with that of a 3.5-mm cortical screw (cortical screw group), and (2) to measure the pullout strength of a 4-mm cancellous screw placed as a rescue screw (rescue screw group) in a stripped 3.5-mm cortical screw (stripped screw group) hole while controlling for bone density and cortical thickness. METHODS We inserted 4 screws, one from each experimental group, into 11 osteoporotic cadaveric radii, while recording the insertion torque. Radii were mounted on a servohydraulic testing machine, and each screw was pulled out at a rate of 5 mm/min. Pullout strength was recorded. The effects of cortical thickness (near, far, and total), bone density, insertion torque, and the experimental screw group (cortical, cancellous, stripped, and rescue screw groups) on pullout strength were analyzed using multiple linear regression with random effects. Statistical significance was set at P < 0.05. RESULTS There was no significant difference in pullout strength between the cortical and cancellous screw groups. The rescue screw group had significantly less pullout strength than did the cortical and cancellous screws, and only partly increased pullout strength compared with stripped screws. Bone density significantly affected pullout strength, but insertion torque and cortical thickness were not significant covariates. CONCLUSIONS There seems to be no advantage in using a cancellous screw over a cortical screw in bicortical fixation in osteoporotic bone. Although the rescue screw provided greater pullout strength than the stripped screw, it is unknown if the purchase it provides is clinically sufficient.
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Abstract
UNLABELLED STUDY DESIGN.: Biomechanical testing of vertebral body screw pullout resistance with relevance to top screw pullout in thoracoscopic anterior scoliosis constructs. OBJECTIVE To analyze the effect of screw positioning and angulation on pullout resistance of vertebral body screws, where the pullout takes place along a curved path as occurs in anterior scoliosis constructs. SUMMARY OF BACKGROUND DATA Top screw pullout is a significant clinical problem in thoracoscopic anterior scoliosis surgery, with rates of up to18% reported in the literature. METHODS A custom-designed biomechanical test rig was used to perform pullout tests of Medtronic anterior vertebral screws where the pullout occurred along an arc of known radius. Using synthetic bone blocks, a range of pullout radiuses and screw angulations were tested, in order to determine an "optimal" configuration. The optimal configuration was then compared with standard screw positioning using a series of tests on ovine vertebrae (n=29). RESULTS Screw angulation has a small but significant effect on pullout resistance, with maximum strength being achieved at 10-degree cephalad angulation. Combining 10-degree cephalad angulation with maximal spacing between the top 2 screws (maximum pullout radius) increased the pullout resistance by 88% compared with "standard" screw positioning (screws inserted perpendicular to rod at midbody height). CONCLUSION The positioning of the top screw in anterior scoliosis constructs can significantly alter its pullout resistance.
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Pollard JD, Deyhim A, Rigby RB, Dau N, King C, Fallat LM, Bir C. Comparison of pullout strength between 3.5-mm fully threaded, bicortical screws and 4.0-mm partially threaded, cancellous screws in the fixation of medial malleolar fractures. J Foot Ankle Surg 2010; 49:248-52. [PMID: 20362467 DOI: 10.1053/j.jfas.2010.02.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Indexed: 02/03/2023]
Abstract
Displaced medial malleolus fractures are considered unstable and typically require open reduction and internal fixation for anatomic reduction and early joint range of motion. These fractures are usually fixated with either compression lag screws or tension band wiring depending on the fracture pattern, size of the distal fragment, and bone quality. When fracture fixation fails, it is typically in pullout strength. Failure of primary bone healing can result in nonunion, malunion, and need for revision surgery. The current study wished to explore a potentially stronger fixation technique in regard to pullout strength for medial malleolar fractures compared with traditional cancellous screws. This was a comparative study of the relative pullout strength of 2 fully threaded 3.5-mm bicortical screws versus 2 partially threaded 4.0-mm cancellous screws for the fixation of medial malleolar fractures. Ten fresh-frozen limbs from 5 cadavers, mean age 79 years (range of 65-97 years), were tested using the Instron 8500 Plus system. The median force recorded at 2 mm of distraction using unicortical partially threaded cancellous screws was 116.2 N (range 70.2 to 355.5N) compared with 327.6 N (range 117.5 to 804.3 N) in the fully threaded bicortical screw (P = .04). The unicortical screw fixation displayed only 64.53% of the median strength noted with the bicortical screw fixation at clinical failure. The current study demonstrated statistically significantly greater pullout strength for 3.5-mm bicortical screws when compared with 4.0-mm partially threaded cancellous screws used to fixate medial malleolar fractures in a cadaveric model.
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Affiliation(s)
- Jason D Pollard
- Kaiser San Francisco Bay Area Foot and Ankle Residency Program, Department of Orthopaedics and Podiatry, Kaiser Foundation Hospital, Oakland, CA, USA.
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Chatzistergos PE, Magnissalis EA, Kourkoulis SK. A parametric study of cylindrical pedicle screw design implications on the pullout performance using an experimentally validated finite-element model. Med Eng Phys 2010; 32:145-54. [DOI: 10.1016/j.medengphy.2009.11.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Revised: 09/14/2009] [Accepted: 11/02/2009] [Indexed: 11/28/2022]
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