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Álvarez-Blanco M, Infante-García D, Marco M, Giner E, Miguélez MH. Development of bone surrogates by material extrusion-based additive manufacturing to mimic flexural mechanical behaviour and fracture prediction via phase-field approach. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2024; 254:108287. [PMID: 38908222 DOI: 10.1016/j.cmpb.2024.108287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Revised: 06/04/2024] [Accepted: 06/14/2024] [Indexed: 06/24/2024]
Abstract
BACKGROUND AND OBJECTIVE The limited availability of human bone samples for investigation leads to the demand for alternatives. Bone surrogates are crucial in promoting research on the intricate mechanics of osseous tissue. However, solutions are restricted to commercial brands, which frequently fail to faithfully replicate the mechanical response of bone, or oversimplified customised simulants designed for a specific application. The manufacturing and assessment of reliable bone surrogates made of polylactic acid via material extrusion-based additive manufacturing are presented in this work. METHODS An experimental and numerical study with 3D-printed dog-bone and prismatic specimens was carried out to characterise the polymeric feedstock and analyse the influence of process parameters under three-point bending and quasi-static conditions. Besides, three porcine rib samples were considered as a reference for the development of the artificial bones. Bone surrogates were manufactured from the 3D-scanned real bone geometries. In order to reproduce the trabecular and cortical bone, a lattice structure for the infill and a compact shell surrounding the core were employed. Infill density and shell thickness were evaluated through different printing configurations. Additionally, a computational analysis based on the phase-field approach was conducted to simulate the experimental tests and predict fracture. The modelling considered homogenisation of the infill material. RESULTS Outcomes demonstrated the potential of the presented methodology. Maximum force and flexural stiffness were compared to real bone properties to find the optimal printing configuration, replicating the flexural mechanical behaviour of bone tissue. Certain configurations accurately reproduce the studied properties. Regarding the numerical model, strength and stiffness prediction was validated with experimental results. CONCLUSIONS The presented methodology enables the manufacturing of artificial bones with accurate geometries and tailored mechanical properties. Furthermore, the described modelling strategy offers a powerful tool for designing bone surrogates.
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Affiliation(s)
- Mario Álvarez-Blanco
- Department of Mechanical Engineering. Universidad Carlos III de Madrid, Avenida. de la Universidad 30, 28911 Leganés, Madrid, Spain
| | - Diego Infante-García
- Institute of Mechanical and Biomechanical Engineering - I2MB, Department of Mechanical Engineering and Materials, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Miguel Marco
- Department of Mechanical Engineering. Universidad Carlos III de Madrid, Avenida. de la Universidad 30, 28911 Leganés, Madrid, Spain.
| | - Eugenio Giner
- Institute of Mechanical and Biomechanical Engineering - I2MB, Department of Mechanical Engineering and Materials, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - M Henar Miguélez
- Department of Mechanical Engineering. Universidad Carlos III de Madrid, Avenida. de la Universidad 30, 28911 Leganés, Madrid, Spain
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Loha T, Bhattacharya R, Pal B, Amis AA. A novel design of hip-stem with reduced strain-shielding. Proc Inst Mech Eng H 2024; 238:471-482. [PMID: 38644528 DOI: 10.1177/09544119241244537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The use of uncemented stems in hip arthroplasty has been increasing, even in osteoporotic patients. The major concerns of uncemented hip-stems, however, are peri-prosthetic fracture, thigh pain, and proximal femoral stress-/strain-shielding. In this study, a novel design of uncemented hip-stem is proposed that will reduce such concerns, improve osseointegration, and benefit both osteoporotic and arthritic patients. The stem has a central titanium alloy core surrounded by a set of radial buttresses that are partly porous titanium, as is the stem tip. The aim of the study was to investigate the mechanical behaviour of the proposed partly-porous design, examining load transfer in the short-term, and comparing its strain-shielding behaviour with a solid metal implant. The long-term effect of implant-induced bone remodelling was also simulated. Computed tomography based three-dimensional finite element models of an intact proximal femur, and the same femur implanted with the proposed design, were developed. Peak hip contact and major muscle forces corresponding to level-walking and stair climbing were applied. The proposed partly-porous design had approximately 50% lower strain-shielding than the solid-metal counterpart. Results of bone remodelling simulation indicated that only 16% of the total bone volume is subjected to reduction of bone density. Strain concentrations were observed in the bone around the stem-tip for both solid and porous implants; however, it was less prominent for the porous design. Lower strain-shielding and reduced bone resorption are advantageous for long-term fixation, and the reduced strain concentration around the stem-tip indicates a lower risk of peri-prosthetic fracture.
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Affiliation(s)
- Tanmoy Loha
- Department of Mechanical Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, India
| | - Rounak Bhattacharya
- Department of Mechanical Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, India
| | - Bidyut Pal
- Department of Mechanical Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, India
- Department of Mechanical Engineering, Imperial College London, London, UK
| | - Andrew A Amis
- Department of Mechanical Engineering, Imperial College London, London, UK
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Freitas A, Lobo MDO, Alves GHD, Barbosa RFC, Blanco LGR, Shimano AC. In vitro mechanical analysis of X-shaped femoroplasty with polymethyl methacrylate boundary a fall on the greater trochanter . Injury 2023; 54 Suppl 6:110747. [PMID: 38143120 DOI: 10.1016/j.injury.2023.04.034] [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: 02/10/2023] [Revised: 04/10/2023] [Accepted: 04/14/2023] [Indexed: 12/26/2023]
Abstract
To evaluate with mechanical testing (MT) using synthetic femurs, an X-shaped femoroplasty technique with polymethyl methacrylate (PMMA), analyzing the results applied to the prophylaxis of proximal femur (PF) fractures caused by low-energy trauma. MT was performed simulating a fall on the greater trochanter, using fifteen Sawbones™ models. They were divided into three experimental groups (n = 5): control (DP) group, drilled without augmentation (DWA) group, and X-shaped augmentation (DX) group. Maximum load, stiffness, absorbed energy and displacement were analyzed primarily in all groups; and secondarily then, morphology and fracture type were verified in all groups while PMMA volume, temperature and time polymerization were analyzed only in the DX group. The MT results obtained for synthetic models respectively in the DP, DWA, and DX groups were: mean maximum load (5562.0 ± 464.8) N, (4798.0 ± 121.2) N, and (7132.0 ± 206.9) N; mean stiffness values (673 ± 64.34) N/mm, (636 ± 8.7) N/mm, and (738 ± 17.13) N/mm, and mean absorbed energy values (36,203 ± 3819) N.mm, (27,617 ± 3011) N.mm, (44,762 ± 3219) N.mm; mean displacement values (13.6 ± 1.45) N, (11.1 ± 0.5) N, and (13.2 ± 0.69) N. The mean volume, temperature reached during filling in the DX group were 9.8 mL, 42.54ºC with 1' 56" of polymerization. The fracture types were similar between the DP and DWA groups, affecting the trochanteric region, as distinctly to those in the DX group, which were restricted to the femoral neck. The values obtained in MT showed statistical significance when analyzed by one-way ANOVA (5%) for maximum load, stiffness, and absorbed energy between groups. In conclusion, X-shaped PMMA augmentation presents a protective biomechanical characteristic against PF fractures generated in synthetic models by boundary a fall on the greater trochanter.
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Affiliation(s)
- Anderson Freitas
- Hospital Ortopédico e Medicina Especializada (HOME), Orthopedic Trauma Service, Hospital Regional do Gama, Brasília, DF, Brazil.
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Inacio JV, Cristino DM, Hast MW, Dailey HL. An Adaptable Computed Tomography-Derived Three-Dimensional-Printed Alignment Fixture Minimizes Errors in Radius Biomechanical Testing. J Biomech Eng 2021; 143:111006. [PMID: 34114605 DOI: 10.1115/1.4051433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Indexed: 11/08/2022]
Abstract
Biomechanical testing of long bones can be susceptible to errors and uncertainty due to malalignment of specimens with respect to the mechanical axis of the test frame. To solve this problem, we designed a novel, customizable alignment and potting fixture for long bone testing. The fixture consists of three-dimensional-printed components modeled from specimen-specific computed tomography (CT) scans to achieve a predetermined specimen alignment. We demonstrated the functionality of this fixture by comparing benchtop torsional test results to specimen-matched finite element models and found a strong correlation (R2 = 0.95, p < 0.001). Additional computational models were used to estimate the impact of malalignment on mechanical behavior in both torsion and axial compression. Results confirmed that torsion testing is relatively robust to alignment artifacts, with absolute percent errors less than 8% in all malalignment scenarios. In contrast, axial testing was highly sensitive to setup errors, experiencing absolute percent errors up to 50% with off-center malalignment and up to 170% with angular malalignment. This suggests that whenever appropriate, torsion tests should be used preferentially as a summary mechanical measure. When more challenging modes of loading are required, pretest clinical-resolution CT scanning can be effectively used to create potting fixtures that allow for precise preplanned specimen alignment. This may be particularly important for more sensitive biomechanical tests (e.g., axial compressive tests) that may be needed for industrial applications, such as orthopedic implant design.
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Affiliation(s)
- Jordan V Inacio
- Department of Mechanical Engineering & Mechanics, Packard Laboratory, Lehigh University, 19 Memorial Drive West, Bethlehem, PA 18015
| | - Danielle M Cristino
- Department of Orthopaedic Surgery, Biedermann Lab for Orthopaedic Research, University of Pennsylvania, 3737 Market Street, Tenth Floor Suite 1050, Philadelphia, PA 19104
| | - Michael W Hast
- Department of Orthopaedic Surgery, Biedermann Lab for Orthopaedic Research, University of Pennsylvania, 3737 Market Street, Tenth Floor Suite 1050, Philadelphia, PA 19104
| | - Hannah L Dailey
- Department of Mechanical Engineering & Mechanics, Packard Laboratory, Lehigh University, 19 Memorial Drive West, Bethlehem, PA 18015
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Lee WC, Chou SM, Tan CW, Chng LS, Yam GJM, Chua THI. Intertrochanteric fracture with distal extension: When is the short proximal femoral nail antirotation too short? Injury 2021; 52:926-932. [PMID: 33082031 DOI: 10.1016/j.injury.2020.10.059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 09/25/2020] [Accepted: 10/13/2020] [Indexed: 02/02/2023]
Abstract
INTRODUCTION The lesser trochanter (LT) fragment in the multifragmentary intertrochanteric femur fracture (AO 31A2.2) may extend distally. If the fragment extends too distally, fixation with a short proximal femoral nail antirotation (PFNA-II) device may not be sufficient. The exact length of distal extension that can be tolerated by the short PFNA-II is not known, therefore it is our objective to determine it. MATERIALS AND METHODS A finite element analysis was performed on AO 31A2.2 fracture fixed with a 200mm length size 10 PFNA-II. The construct was loaded vertically to clinical failure of 10mm displacement. This was repeated with the size of the LT fragment increasing distally at intervals, up to 120mm from the base of the LT. The process was also repeated with the bone properties substituted with osteoporotic properties. The stiffness, maximum vertical reaction force, and the plastic deformation area were investigated. RESULTS In both non-osteoporotic and osteoporotic model, the stiffness and the maximum vertical reaction force of the construct dropped significantly when the LT fragment is larger than 40mm. Beyond 40mm of LT fragment size, there was a rapid increase in the area of plastic deformation of the cortical bone distal to the intertrochanteric fracture, signifying structural failure of the construct. CONCLUSION A long PFNA-II should be considered when fixing a multifragmentary intertrochanteric fracture if the LT fragment extends 40mm distal to the distal base of the LT as the construct fails rapidly upon uniaxial load to failure. Clinically, this threshold may be smaller to account for the multi-axial and dynamic stresses.
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Affiliation(s)
- Wu Chean Lee
- Department of Orthopaedic Surgery, Annex 1 Level 2, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
| | - Siaw Meng Chou
- School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Chee Wei Tan
- Advanced Analysis, Advisian, Alexandra Technopark, 438B Alexandra Road #04-09, Singapore 119968, Singapore
| | - Li Sing Chng
- School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Gui Jie Michael Yam
- Department of Orthopaedic Surgery, Annex 1 Level 2, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore
| | - Tjun Huat Ivan Chua
- Department of Orthopaedic Surgery, Annex 1 Level 2, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore
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Biodegradable cement augmentation of gamma nail osteosynthesis reduces migration in pertrochanteric fractures, a biomechanical in vitro study. Clin Biomech (Bristol, Avon) 2021; 84:105327. [PMID: 33773169 DOI: 10.1016/j.clinbiomech.2021.105327] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Cut-out of gamma nail often results from poor primary bone stability, suboptimal reduction (varus) and excentric placement of the head element which may lead to "instability" and frequently requires revision. Various studies have shown that augmentation with polymethylmethacrylate cement increases the primary stability of osteosynthesis. However, it has not yet been widely used in fracture treatment due to certain disadvantages, e.g., the lack of osteointegration, the formation of an interface membrane or the presence of toxic monomers. Few studies show that biodegradable bone cements increase the stability of osteosynthesis in different anatomical regions and therefore could be an alternative to polymethylmethacrylate cement in the treatment of pertrochanteric fractures. METHODS Two biomechanical situations were simulated using 24 Sawbones (simple and multifragmentary pertrochanteric fractures; AO-classification 31-A1 and 31-A2. Both groups were stabilized using the Gamma3® nailing system with and without biodegradable bone cement. Sawbones underwent the same cyclic loading test, simulating 10.000 gait cycles loading the bones with three times body weight. Migration was determined by comparing computed tomography scans recorded before and after the mechanical testing. The three-dimensional migration of the lag screw was calculated, and the rotation of the head around the longitudinal axis was determined. FINDINGS Biodegradable cement reduced migration by approximately 35% in 31-A1 fractures (25.4% in 31-A2 fractures) and the rotation of the head around the lag screw by approximately 37% in 31-A1 fractures (17.8%, 31-A2). INTERPRETATION Use of biodegradable bone cement improved the primary stability of gamma nail osteosynthesis in the biomechanical model.
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Collins CJ, Yang B, Crenshaw TD, Ploeg HL. Evaluation of experimental, analytical, and computational methods to determine long-bone bending stiffness. J Mech Behav Biomed Mater 2020; 115:104253. [PMID: 33360160 DOI: 10.1016/j.jmbbm.2020.104253] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 11/08/2020] [Accepted: 12/06/2020] [Indexed: 12/15/2022]
Abstract
Methods used to evaluate bone mechanical properties vary widely depending on the motivation and environment of individual researchers, clinicians, and industries. Further, the innate complexity of bone makes validation of each method difficult. Thus, the purpose of the present research was to quantify methodological error of the most common methods used to predict long-bone bending stiffness, more specifically, flexural rigidity (EI). Functional testing of a bi-material porcine bone surrogate, developed in a previous study, was conducted under four-point bending test conditions. The bone surrogate was imaged using computed tomography (CT) with an isotropic voxel resolution of 0.625 mm. Digital image correlation (DIC) of the bone surrogate was used to quantify the methodological error between experimental, analytical, and computational methods used to calculate EI. These methods include the application of Euler Bernoulli beam theory to mechanical testing and DIC data; the product of the bone surrogate composite bending modulus and second area moment of inertia; and finite element analysis (FEA) using computer-aided design (CAD) and CT-based geometric models. The methodological errors of each method were then compared. The results of this study determined that CAD-based FEA was the most accurate determinant of bone EI, with less than five percent difference in EI to that of the DIC and consistent reproducibility of the measured displacements for each load increment. CT-based FEA was most accurate for axial strains. Analytical calculations overestimated EI and mechanical testing was the least accurate, grossly underestimating flexural rigidity of long-bones.
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Affiliation(s)
- Caitlyn J Collins
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Health Sciences and Technology, Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
| | - Baixuan Yang
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada
| | - Thomas D Crenshaw
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Heidi-Lynn Ploeg
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada
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Deng Y, Ouyang H, Xie P, Wang Y, Yang Y, Tan W, Zhao D, Zhong S, Huang W. Biomechanical assessment of screw safety between far cortical locking and locked plating constructs. Comput Methods Biomech Biomed Engin 2020; 24:663-672. [PMID: 33215954 DOI: 10.1080/10255842.2020.1844882] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
With the emerging concerns for more flexible and less stiff bridge constructs in the interest of stimulating bone healing, the technique of far cortical locking has been designed to reduce the stiffness of locked plating (LP) constructs while retaining construct strength. This study utilized simulation with diaphyseal bridge plating biomechanical models to investigate whether far cortical locking causes larger screw fracture risk than LP during rehabilitation. The fracture risk of the screws in the far cortical locking constructs increases in the non-osteoporotic and osteoporotic diaphysis compared with the screws in the LP constructs.
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Affiliation(s)
- Yuping Deng
- National Key Discipline of Human Anatomy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China.,Guangdong Provincial Medical Biomechanical Key Laboratory, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China
| | - Hanbin Ouyang
- Orthopaedic Center, Affiliated Hospital of Guangdong Medical University, Guangdong Medical University, Zhanjiang, P.R. China
| | - Pusheng Xie
- National Key Discipline of Human Anatomy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China.,Guangdong Provincial Medical Biomechanical Key Laboratory, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China
| | - Yanfang Wang
- National Key Discipline of Human Anatomy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China.,Guangdong Provincial Medical Biomechanical Key Laboratory, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China
| | - Yang Yang
- National Key Discipline of Human Anatomy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China.,Guangdong Provincial Medical Biomechanical Key Laboratory, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China
| | - Wenchang Tan
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing, China
| | - Dongliang Zhao
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing, China
| | - Shizhen Zhong
- National Key Discipline of Human Anatomy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China.,Guangdong Provincial Medical Biomechanical Key Laboratory, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China
| | - Wenhua Huang
- National Key Discipline of Human Anatomy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China.,Guangdong Provincial Medical Biomechanical Key Laboratory, School of Basic Medical Sciences, Southern Medical University, Guangzhou, P.R. China
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Optimal configuration for stability and magnetic resonance imaging quality in temporary external fixation of tibial plateau fractures. Orthop Traumatol Surg Res 2020; 106:1405-1412. [PMID: 32245692 DOI: 10.1016/j.otsr.2019.12.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 12/09/2019] [Accepted: 12/16/2019] [Indexed: 02/03/2023]
Abstract
INTRODUCTION Temporary external fixation has been widely utilized in the stabilization of plateau fractures while waiting for an optimization of the soft tissue conditions before subsequent permanent internal fixation. Simultaneously, MRI is beneficial in the assessment of concomitant damage to ligaments and menisci so that these injuries could be promptly identified, and surgical planning executed at the time of definitive fixation of the bony injury. Increasing numbers of side-bars and pins have been previously suggested to increase frame rigidity, but at the same time, several studies have indicated the presence of MRI artifacts which may obscure key anatomical structures, even when MRI-compatible fixation devices are used. This study aims to identify, among six potential configurations, the construct that maximizes stability while most minimizing the number of MRI artifacts generated among different configurations commonly used. HYPOTHESIS There is one or more configurations among the others that maximize stability while preserving a clinically acceptable level of MRI quality. MATERIAL AND METHODS Six constructs were recreated on cadaveric specimens and identified by the disposition of the bars: H, Anterior, Flash, Hashtag, Rhomboid, and Diamond. Stage one evaluated the amount of artifact produced during MRI on instrumented cadaveric legs, as well as the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) at five specific regions of interest. Stage two assessed the amount of compressional and torsional stiffness of the configurations on bone surrogate models. RESULTS Image artifacts were not detected within the knee joint for all considered constructs. In terms of SNR The H, Anterior, Hashtag, and Diamond configurations were not significantly different from their control (p>0.366) while the others were significantly different (p<0.03). The values of CNR found for the H and Hashtag configurations were not significantly different from their controls (p>0.07) while the remaining configurations were significantly different (p<0.03). In compression, the H and Diamond configurations had similar stiffness (p=0.468) of 35.78N/mm and 31.44N/mm, respectively, and were stiffer than the other configurations. In torsion, the constructs have shown different stiffness (p<0.001) with a minimum value of 0.66 Nm/deg for the Rhomboid configuration, which was significantly less stiff than the Anterior configuration (1.20 Nm/deg [p<0.001]). There was no difference between the Diamond and H configurations (p=0.177) or between them and the Hashtag configuration (p=0.215). DISCUSSION An external fixator construct directly bridging the femur and tibia without interconnections is the most stable and produces MRI scans without image artifacts that would interfere with diagnostic quality. LEVEL OF EVIDENCE V, basic science study, diagnostic imaging and mechanical testing.
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Gluek C, Zdero R, Quenneville CE. Evaluating the mechanical response of novel synthetic femurs for representing osteoporotic bone. J Biomech 2020; 111:110018. [PMID: 32891014 DOI: 10.1016/j.jbiomech.2020.110018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 08/16/2020] [Accepted: 08/18/2020] [Indexed: 11/27/2022]
Abstract
Osteoporosis is a disease prevalent in older adults, characterized by high porosity in bone and subsequent decrease in fracture resistance. This demographic is also the population that most frequently receives devices such as hip implants. However, high porosity complicates surgery and reduces the fixation and effectiveness of orthopaedic devices, which are typically designed using cadaveric specimens from the general population. Synthetic bones are also used in the design of such devices but need to represent the properties of the patient population. Thus, the mechanical response of two iterations of novel synthetic femurs were evaluated for their ability to represent osteoporotic cadaveric specimens and were tested and compared against cadaveric specimens across four loading modes. The first iteration had reduced density and wall thickness compared to standard models and was typically too rigid or too stiff to be a feasible alternative to cadaveric specimens. The second iteration, with similarly reduced wall thickness and further reduced density, was quite representative, with no statistical differences identified against the cadaveric specimens in any loading mode, except in screw pullout. Such a model can provide a foundation for the development of orthopaedic devices better suited to osteoporotic bone, potentially improving surgical outcomes, reducing medical expense, and improving quality of life for patients.
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Affiliation(s)
- Cooper Gluek
- Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
| | - Radovan Zdero
- Department of Mechanical and Materials Engineering, Western University, 1151 Richmond Street, London, Ontario N6A 3K7, Canada; Department of Surgery (Division of Orthopaedic Surgery), Western University, 1151 Richmond Street, London, Ontario N6A 3K7, Canada
| | - Cheryl E Quenneville
- Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada; School of Biomedical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada.
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Ceynowa M, Zerdzicki K, Klosowski P, Pankowski R, Rocławski M, Mazurek T. The early failure of the gamma nail and the dynamic hip screw in femurs with a wide medullary canal. A biomechanical study of intertrochanteric fractures. Clin Biomech (Bristol, Avon) 2020; 71:201-207. [PMID: 31775090 DOI: 10.1016/j.clinbiomech.2019.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 10/28/2019] [Accepted: 11/11/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND Intertrochanteric fractures may occur in a bone with a wide medullary canal that may lead to significant mobility of a intramedullary nail, contrary to an extramedullary device. This study evaluates the Dynamic Hip Screw and the gamma nail in AO 31.A2.1 fractures in these circumstances. METHODS Synthetic femora with canals drilled to 18 mm were used. Five fixation types were examined: a 2 - hole and a 4 - hole Dynamic Hip Screw with a 2 - hole plate, a standard gamma nail with dynamic and static distal locking and a long gamma nail. The specimens were tested with cyclic axial loading, from 500 N increasing of 50 N increments in each cycle. Force at failure, overall stiffness, stiffness at the fracture site, location and mode of failure were recorded. FINDINGS The short gamma nails dislocated into varus under preload because the nail migrated laterally. The Dynamic Hip Screw was initially stable, but some specimens rotated around the lag screw. The gamma nail was rotationally stable. Both implants failed through femur fracture. The long gamma nailed failed by screw cut - out at forces lower than the ultimate force of the short gamma nail. INTERPRETATION This study shows that the gamma nail is unstable in a large medullary canal but offers better rotational stability of the proximal fragment. A modification of the nail design or the operative technique may be considered.
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Affiliation(s)
- Marcin Ceynowa
- Department of Orthopedic Surgery, Medical University of Gdańsk, ul. Nowe Ogrody 1-6, 80-803 Gdańsk, Poland.
| | - Krzysztof Zerdzicki
- Faculty of Civil and Environmental Engineering, Gdansk University of Technology, Gabriela Narutowicza 11/12, 80-233 Gdańsk, Poland.
| | - Pawel Klosowski
- Faculty of Civil and Environmental Engineering, Gdansk University of Technology, Gabriela Narutowicza 11/12, 80-233 Gdańsk, Poland.
| | - Rafał Pankowski
- Department of Orthopedic Surgery, Medical University of Gdańsk, ul. Nowe Ogrody 1-6, 80-803 Gdańsk, Poland
| | - Marek Rocławski
- Department of Orthopedic Surgery, Medical University of Gdańsk, ul. Nowe Ogrody 1-6, 80-803 Gdańsk, Poland
| | - Tomasz Mazurek
- Department of Orthopedic Surgery, Medical University of Gdańsk, ul. Nowe Ogrody 1-6, 80-803 Gdańsk, Poland
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Abstract
OBJECTIVES To investigate the biomechanical properties of a lateral locked plate alone or in combination with a supplemental medial plate or an intramedullary nail (IMN). METHODS Intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C) were simulated with a standardized model in 28 synthetic femora and divided into 4 groups. Group I was instrumented with a 4.5-mm lateral locked distal femoral plate alone, group II with a lateral locked plate plus a low-profile precontoured 3.5-mm medial distal tibial plate, group III with a lateral locked plate plus a medial 3.5-mm reconstruction plate, and group IV with a lateral locked plate plus a retrograde IMN. Specimens were then axially loaded and cycled to failure or runout. Outcomes of interest were baseline stiffness, survivability, and cycles to failure. RESULTS Groups III and IV have a significantly higher baseline stiffness (P < 0.001) when compared with groups I and II. Furthermore, groups III and IV had a higher max load to failure (P < 0.01) when compared with groups I and II. The survivability in groups III and IV was 71% and 100%, respectively, while no specimens in group I or II survived maximum loading. There was no significant difference between group III and IV regarding stiffness, survivability, and cycles to failure. CONCLUSION When considering fixation for intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C), we found that supplementation of a lateral locked plate with a medial plate or an IMN to be biomechanically superior to lateral locked plating alone regarding stiffness, survivability, and cycles to failure. A low-profile precontoured plate did not add significantly to the construct stiffness in this study.
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Rog D, Grigsby P, Hill Z, Pinette W, Inceoglu S, Zuckerman L. A biomechanical comparison of the two- and four-hole side-plate dynamic hip screw in an osteoporotic composite femur model. J Orthop Surg (Hong Kong) 2018; 25:2309499017717199. [PMID: 28664768 DOI: 10.1177/2309499017717199] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVES The objectives of this study were (1) to compare the axial and torsional stiffness of a dynamic hip screw with a two- and four-hole side-plate in a synthetic model of a healed and stable intertrochanteric femur fracture and (2) to evaluate the load to failure, as well as propensity to peri-implant fracture. METHODS Fourth-generation synthetic composite femur models, simulating osteoporotic bone, were implanted with 135° dynamic hip screws (DHS) with either a two- or four-hole side-plate with or without a stable intertrochanteric fracture. Specimens were cyclically loaded up to a nondestructive load to determine the axial and torsional stiffness. Constructs were then loaded to failure in axial compression emulating physiologic forces. Failure load and location of the peri-implant fractures were recorded. RESULTS Axial and torsional stiffness did not differ significantly between the two- and four-hole constructs in either model. Likewise, there was no significant difference in the load to failure. In the intact femurs, failure occurred either at the end of the plate at the distal screw or through the lag screw hole. CONCLUSION The results of this study demonstrate that DHS constructs with a two- or four-hole side-plate are biomechanically comparable with regard to axial and torsional stiffness and load to failure in an osteoporotic composite femur model. In a healed intertrochanteric fracture model, a two-hole construct did not appear to be more prone to peri-implant fracture. To date, a biomechanical comparison of these two implants with regard to torsional forces has not been reported.
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Affiliation(s)
- Dominik Rog
- Department of Orthopaedic Surgery, School of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Phillip Grigsby
- Department of Orthopaedic Surgery, School of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Zachary Hill
- Department of Orthopaedic Surgery, School of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - William Pinette
- Department of Orthopaedic Surgery, School of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Serkan Inceoglu
- Department of Orthopaedic Surgery, School of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Lee Zuckerman
- Department of Orthopaedic Surgery, School of Medicine, Loma Linda University, Loma Linda, CA, USA
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Knežević J, Kodvanj J, Čukelj F, Pamuković F, Pavić A. A biomechanical comparison of four fixed-angle dorsal plates in a finite element model of dorsally-unstable radius fracture. Injury 2017; 48 Suppl 5:S41-S46. [PMID: 29122121 DOI: 10.1016/s0020-1383(17)30738-6] [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] [Indexed: 02/02/2023]
Abstract
PURPOSE To compare the finite element models of two different composite radius fracture patterns, reduced and stabilised with four different fixed-angle dorsal plates during axial, dorsal and volar loading conditions. METHODS Eight different plastic models representing four AO/ASIF type 23-A3 distal radius fractures and four AO/ASIF 23-C2 distal radius fractures were obtained and fixed each with 1 of 4 methods: a standard dorsal non-anatomical fixed angle T-plate (3.5mm Dorsal T-plate, Synthes), anatomical fixed-angle double plates (2.4mm LCP Dorsal Distal Radius, Synthes), anatomical fixed angle T-plate (2.4mm Acu-Loc Dorsal Plate, Acumed) or anatomical variable-angle dorsal T-plate (3.5mm, Dorsal Plate, Zrinski). Composite radius with plate and screws were scanned with a 3D optical scanner and later processed in Abaqus Software to generate the finite element model. All models were axially loaded at 3 points (centrally, volarly and dorsally) with 50 N forces to avoid the appearance of plastic deformations of the models. Total displacements at the end of the bone and the stresses in the bones and plates were determined and compared. RESULTS Maximal von Mises stress in bone for 3-part fracture models was very similar to that in 2-part fracture models. The biggest difference between models and the largest displacements were seen during volar loading. The stresses in all models were the highest above the fracture gap. The best performance in all parameters tested was with the Zrinski plate and the most modest results were with the Synthes T-plate. CONCLUSION There was no significant difference between 2-part (AO/ASIF type 23-A3) and 3-part (AO/ASIF 23-C2) fracture models. Maximal stresses in the plates appeared above the fracture gap; therefore, it is worth considering the development of plates without screw holes above the gap.
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Affiliation(s)
- Josip Knežević
- University Hospital Split, Department of Orthopaedic Trauma, Spinčićeva 1, 21000 Split, Croatia.
| | - Janoš Kodvanj
- Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000 Zagreb, Croatia
| | - Fabijan Čukelj
- Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000 Zagreb, Croatia
| | - Frane Pamuković
- Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000 Zagreb, Croatia
| | - Arsen Pavić
- University Hospital Split, Department of Orthopaedic Trauma, Spinčićeva 1, 21000 Split, Croatia
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Lopes VM, Neto MA, Amaro AM, Roseiro LM, Paulino M. FE and experimental study on how the cortex material properties of synthetic femurs affect strain levels. Med Eng Phys 2017. [DOI: 10.1016/j.medengphy.2017.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Biomechanical Comparison of Cadaveric and Commercially Available Synthetic Osteoporotic Bone Analogues in a Locked Plate Fracture Model Under Torsional Loading. J Orthop Trauma 2017; 31:e137-e142. [PMID: 28079730 DOI: 10.1097/bot.0000000000000782] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES Biomechanical studies of osteoporotic bone have used synthetic models rather than cadaveric samples because of decreased variability, increased availability, and overall ease of the use of synthetic models. We compared the torsional mechanical properties of cadaveric osteoporotic bone with those of currently available synthetic osteoporotic bone analogues. METHODS We tested 12 osteoporotic cadaveric humeri and 6 specimens each of 6 types of synthetic analogues. A 5-mm fracture gap model and posterior plating technique with 4.5-mm narrow 10-hole locking compression plate were used. Torque was applied to a peak of ±10 N·m for 1000 cycles at 0.3 Hz. Data were continuously collected during cyclical and ramped loading with a servohydraulic materials testing system. RESULTS Cadaveric bone had a 17% failure rate before completing 1000 cycles. Three osteoporotic bone models had 100% failure (P < 0.05), 2 had 17% failure, and 1 had 0% failure before 1000 cycles. Significant differences in the stiffness of the 3 types of synthetic bone models that survived cyclic loading were noted compared with the cadaveric bone model (P < 0.05). Osteoporotic bone analogues had torsional mechanical properties different from those of osteoporotic cadaveric specimens. CONCLUSIONS The differences between osteoporotic cadaveric humeri and synthetic osteoporotic bone analogues ranged from profound with complete catastrophic failure after a few cycles to subtler differences in stiffness and strain hardening. These findings suggest that different bone analogue models vary substantially in their torsional mechanical properties and might not be appropriate substitutes for cadaveric bone in biomechanical studies of osteoporotic bone.
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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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Walcher MG, Giesinger K, du Sart R, Day RE, Kuster MS. Plate Positioning in Periprosthetic or Interprosthetic Femur Fractures With Stable Implants-A Biomechanical Study. J Arthroplasty 2016; 31:2894-2899. [PMID: 27381372 DOI: 10.1016/j.arth.2016.05.060] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 05/17/2016] [Accepted: 05/25/2016] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Angular stable plate fixation is a widely accepted treatment option for interprosthetic or periprosthetic femoral fractures with stable implants. This biomechanical study tries to establish a safe distance of the plate from the tip of a femoral prosthesis. METHODS A total of 38 composite femurs were reamed to an inner diameter of 23 mm to create an osteoporotic bone model. A Weber hip stem was cemented into each and a distal femoral NCB plate applied with the distance to the stem varying from 8 cm apart to 6 cm overlap in 2-cm steps. Each specimen was tested in cyclic axial loading (400 N-1500 N) and then cyclic torsion (0.6 Nm-50 Nm). Peak strain on the femur around the tip of the plate was measured with a 3D image correlation system and averaged over 26 cycles (excluding the first 3 and the last cycles). Finally, each femur was axially loaded to failure. RESULTS Strain increased with decreasing overlap or gap. Seven specimens failed early between 2-cm overlap and 2-cm gap. Results were divided into a far group with a distance of >4 cm and a close group of <4 cm. Strain was significantly higher in the close group for axial (P < .001) and torsional (P < .001) loading. Failure load was significantly lower in the close group (P = .002). CONCLUSION A minimal gap and/or overlap of at least 6 cm is recommended in osteoporotic bone to avoid stress risers.
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Affiliation(s)
- Matthias G Walcher
- Department of Orthopaedic Surgery, Orthopädische Klinik König-Ludwig-Haus, University of Würzburg, Würzburg, Germany
| | - Karlmeinrad Giesinger
- Department of Orthopaedic Surgery, Kantonsspital St. Gallen, St. Gallen, Switzerland
| | - Ryan du Sart
- University of Western Australia, Royal Perth Hospital, Perth, Western Australia, Australia
| | - Robert E Day
- Department of Medical Engineering and Physics, Royal Perth Hospital, University of Western Australia, Perth, Western Australia, Australia
| | - Markus S Kuster
- The University of Western Australia, Perth Orthopaedic Sports Medicine Centre, West Perth, Australia
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Abstract
OBJECTIVES Locking screws often are used in the treatment of osteoporotic fractures. Studies show that locking screws can increase bone stresses at the plate end, which increases the possibility of peri-implant fracture. This study evaluates whether the technique used to insert the end screw is related to the fracture tolerance adjacent to the plate. METHODS Twelve groups of plate constructs were evaluated using a fibular diaphyseal surrogate with mechanical properties similar to osteoporotic bone. All inboard screws were nonlocked with only the end screw fixation differing among groups. The end screws were inserted either perpendicularly to the plate or at an angle of 30 degrees for 6- and 12-hole plates. For both orientations, the end screws were inserted nonlocked, locked, or by a locked overdrilling technique, resulting in 6 groups per plate length. The perpendicular nonlocked screws represented a control group. The constructs were tested to failure in 4-point bending to determine peak load, failure energy, and stiffness. RESULTS All constructs failed by peri-implant fracture along a plane through the 2 cortical holes of the end screw. Compared with the control group, an angulated locked screw at the plate end significantly increased the peak bending moment and energy required to produce a fracture for both plate lengths (6-hole, P = 0.008, P < 0.001; 12-hole, P = 0.006, P < 0.001). CONCLUSIONS The use of an angulated locked end screw may enhance the resistance of osteoporotic bone to peri-implant fractures caused by bending forces.
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Tsai S, Fitzpatrick DC, Madey SM, Bottlang M. Dynamic locking plates provide symmetric axial dynamization to stimulate fracture healing. J Orthop Res 2015; 33:1218-25. [PMID: 25721801 DOI: 10.1002/jor.22881] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/13/2015] [Indexed: 02/04/2023]
Abstract
Axial dynamization of an osteosynthesis construct can promote fracture healing. This biomechanical study evaluated a novel dynamic locking plate that derives symmetric axial dynamization by elastic suspension of locking holes within the plate. Standard locked and dynamic plating constructs were tested in a diaphyseal bridge-plating model of the femoral diaphysis to determine the amount and symmetry of interfragmentary motion under axial loading, and to assess construct stiffness under axial loading, torsion, and bending. Subsequently, constructs were loaded until failure to determine construct strength and failure modes. Finally, strength tests were repeated in osteoporotic bone surrogates. One body-weight axial loading of standard locked constructs produced asymmetric interfragmentary motion that was over three times smaller at the near cortex (0.1 ± 0.01 mm) than at the far cortex (0.32 ± 0.02 mm). Compared to standard locked constructs, dynamic plating constructs enhanced motion by 0.32 mm at the near cortex and by 0.33 mm at the far cortex and yielded a 77% lower axial stiffness (p < 0.001). Dynamic plating constructs were at least as strong as standard locked constructs under all test conditions. In conclusion, dynamic locking plates symmetrically enhance interfragmentary motion, deliver controlled axial dynamization, and are at least comparable in strength to standard locked constructs. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1218-1225, 2015.
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Affiliation(s)
- Stanley Tsai
- Biomechanics Laboratory, Legacy Research & Technology Center, Portland, 97232, Oregon
| | | | - Steven M Madey
- Biomechanics Laboratory, Legacy Research & Technology Center, Portland, 97232, Oregon
| | - Michael Bottlang
- Biomechanics Laboratory, Legacy Research & Technology Center, Portland, 97232, Oregon
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Marmor M, Elliott IS, Marshall ST, Yacoubian SV, Yacoubian SV, Herfat ST. Biomechanical comparison of long, short, and extended-short nail construct for femoral intertrochanteric fractures. Injury 2015; 46:963-9. [PMID: 25818058 DOI: 10.1016/j.injury.2015.03.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Revised: 02/26/2015] [Accepted: 03/02/2015] [Indexed: 02/02/2023]
Abstract
OBJECTIVES Short and long cephalomedullary (CM) nails are commonly used construct for fixation of intertrochanteric (IT) fractures. Each of these constructs has its advantages and its shortcomings. The extended-short (ES) CM nail offers a hybrid between long and short nail design that aims to combine their respective benefits. The goals of this study were to (1) biomechanically evaluate and compare construct stiffness for the long, short and ES constructs in the fixation of IT fractures, and to (2) investigate the nature of periprosthetic fractures of constructs implanted with these various designs. METHODS Eighteen synthetic femora were used to evaluate three types of fracture fixation constructs. Axial compression, bending, and torsional stiffness were reported for both stable and comminuted IT fracture models. All comminuted fracture constructs were loaded to failure in axial compression to measure failure loads and evaluate periprosthetic fracture patterns. RESULTS Stiffness were similar among constructs with few exceptions. Axial stiffness was significantly higher for the short nail compared to the long nail for the comminuted model (p= 0.020). ES nail constructs exhibited a significantly higher failure load than short nail constructs (p = 0.039). Periprosthetic fractures occurred around the distal interlocking screw in all constructs. CONCLUSIONS Nail length and position of interlocking screw did not alter the biomechanical properties of the fixation construct in the presented IT fracture model. Periprosthetic fractures generated in this study had similar patterns to those seen clinically. This study also suggests that if a periprosthetic fracture is to occur, there is an increased probability of it happening around the site of the interlocking screw, regardless of nail design.
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Affiliation(s)
- Meir Marmor
- UCSF/SFGH Orthopaedic Trauma Institute, UCSF Department of Orthopaedic Surgery, 2550 23rd St, Bldg 9, 2nd floor, San Francisco, CA 94110, USA.
| | - Iain S Elliott
- UCSF/SFGH Orthopaedic Trauma Institute, UCSF Department of Orthopaedic Surgery, 2550 23rd St, Bldg 9, 2nd floor, San Francisco, CA 94110, USA
| | - Silas T Marshall
- UCSF/SFGH Orthopaedic Trauma Institute, UCSF Department of Orthopaedic Surgery, 2550 23rd St, Bldg 9, 2nd floor, San Francisco, CA 94110, USA
| | - Shahan V Yacoubian
- Department of Orthopaedic Surgery, Providence St. Joseph Medical Center, 501 S Buena Vista St, Burbank, CA 91505, USA
| | - Stephan V Yacoubian
- Department of Orthopaedic Surgery, Providence St. Joseph Medical Center, 501 S Buena Vista St, Burbank, CA 91505, USA
| | - Safa T Herfat
- UCSF/SFGH Orthopaedic Trauma Institute, UCSF Department of Orthopaedic Surgery, 2550 23rd St, Bldg 9, 2nd floor, San Francisco, CA 94110, USA
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Yánez A, Cuadrado A, Cabrera PJ, Martel O, Garcés G. Experimental analysis of the minimally invasive plate osteosynthesis technique applied with non-locking screws and screw locking elements. Med Eng Phys 2014; 36:1543-8. [PMID: 25183044 DOI: 10.1016/j.medengphy.2014.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 07/30/2014] [Accepted: 08/12/2014] [Indexed: 11/28/2022]
Abstract
Minimally invasive plate osteosynthesis (MIPO) is an effective surgical technique in the repair of humeral and tibial shaft fractures. There is some controversy as to the minimum number of screws required to ensure correct stability to promote healing, especially when dealing with low quality bones. This work compared different systems assembled on synthetic models simulating a comminuted fracture. Group 1 comprised a locking compression plate with four non-locking screws placed at the holes furthest from the fracture. Group 2 differed from group 1 only in the additional use of two screw locking elements (SLE). Group 3 had four rather than two SLE and, finally, Group 4 used 4 locking screws. The compression and torsion tests with static and cyclic loads showed that, in MIPO, two locking screws or two non-locking screws with SLE could be used per segment without any significant loss in stiffness after 1000 cycles, with system stability guaranteed in both cases. However, lower strength and significant loss of stiffness were observed when non-locking screws were used alone.
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Affiliation(s)
- A Yánez
- Department of Mechanical Engineering, Biomechanical Laboratory, Las Palmas de Gran Canaria University, Engineering Departmental Building, Campus de Tafira Baja, 35017 Las Palmas de Gran Canaria, Spain.
| | - A Cuadrado
- Department of Mechanical Engineering, Biomechanical Laboratory, Las Palmas de Gran Canaria University, Engineering Departmental Building, Campus de Tafira Baja, 35017 Las Palmas de Gran Canaria, Spain
| | - P J Cabrera
- Department of Mechanical Engineering, Biomechanical Laboratory, Las Palmas de Gran Canaria University, Engineering Departmental Building, Campus de Tafira Baja, 35017 Las Palmas de Gran Canaria, Spain
| | - O Martel
- Department of Mechanical Engineering, Biomechanical Laboratory, Las Palmas de Gran Canaria University, Engineering Departmental Building, Campus de Tafira Baja, 35017 Las Palmas de Gran Canaria, Spain
| | - G Garcés
- Hospital Perpetuo Socorro and Department of Medical and Surgical Science, Las Palmas de Gran Canaria University, Health Science Departmental Building, Campus de San Cristóbal, 35016 Las Palmas de Gran Canaria, Spain
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Goffin JM, Pankaj P, Simpson AH. A computational study on the effect of fracture intrusion distance in three- and four-part trochanteric fractures treated with Gamma nail and sliding hip screw. J Orthop Res 2014; 32:39-45. [PMID: 24123306 DOI: 10.1002/jor.22469] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Accepted: 07/22/2013] [Indexed: 02/04/2023]
Abstract
Using finite element analysis, the behaviors of the Gamma nail and the sliding hip screw (SHS) were compared in an osteoporotic bone model for the fixation of three- and four-part trochanteric fractures (31-A2 in the AO classification, types IV and V in Evans' classification). The size of the medial fragment was varied based on clinical data, and the case of a fractured greater trochanter was also considered. Our results showed that for Evans' type V stabilized with a Gamma nail and for Evans' types IV and V with the SHS, cancellous bone around the lag screw is susceptible to yielding, thus indicating a risk of cut-out. The volume of bone susceptible to yielding increases with an increase in size of the medial fragment. Conversely, Evans' type IV with a Gamma nail was not predicted to cut out. Our findings suggest that future clinical trials investigating fixation of unstable proximal fractures should include the size of the medial fragment and the integrity of the greater trochanter as covariables and be powered to evaluate whether intramedullary devices are superior to SHSs for Evans' type IV fractures and inferior/equivalent for type V.
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Affiliation(s)
- Jérôme M Goffin
- Department of Orthopaedic Surgery, The University of Edinburgh, Edinburgh, United Kingdom
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Cuadrado A, Yánez A, Carta J, Garcés G. Suitability of DCPs with Screw Locking Elements to allow sufficient interfragmentary motion to promote secondary bone healing of osteoporotic fractures. Med Eng Phys 2013; 35:852-9. [DOI: 10.1016/j.medengphy.2012.08.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 08/21/2012] [Accepted: 08/24/2012] [Indexed: 10/27/2022]
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Jung TG, Suh SW, Lee SJ, Kim B, Han DW, Yang JH. Biomechanical assessment of a novel bone lengthening plate system - a cadaveric study. Clin Biomech (Bristol, Avon) 2013; 28:232-8. [PMID: 23261017 DOI: 10.1016/j.clinbiomech.2012.11.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 10/18/2012] [Accepted: 11/21/2012] [Indexed: 02/07/2023]
Abstract
BACKGROUND Although many types of external fixators have been developed for distraction osteogenesis, all have some drawbacks. We recently developed a novel bone lengthening plate to overcome these problems. The purpose of this study is to conduct biomechanical analyses using cadavers to assess the stability of the bone lengthening plate in relation to distraction length and femoral bone mineral density. METHODS We used human cadaveric femurs (n=18) to assess the effects of distraction length and bone mineral density on the biomechanical stability of the bone lengthening plate. After establishing control (n=6, 0mm lengthening) and experimental groups (n=12, 30 mm lengthening), we measured biomechanical stability (structural stiffness, ultimate load, and displacement) under a compressive load. The experimental group was subdivided into a group with normal bone mineral density (n=6) and a group with osteoporosis (n=6), and the biomechanical stability of these groups was compared. FINDING Structural stiffness differed significantly between the control (417.6 N/mm) and combined experimental groups (185.6 N/mm, p=0.002). Ultimate load also differed significantly between the control (1327.8 N) and combined experimental (331.4 N, p=0.002) groups. Bone mineral density was unrelated to structural stiffness (p=0.204), ultimate load (0.876), or displacement (0.344). In all cases, failure of the bone lengthening plate occurred at the longitudinal connectors, such as the connecting columns between the upper and lower plates, and the lengthening shaft of the bone lengthening plate. INTERPRETATION The biomechanical stability of the bone lengthening plate was affected by the lengthening length but not by bone mineral density. In addition, biomechanical stability during lengthening was most strongly influenced by the longitudinal connectors.
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Affiliation(s)
- Tae Gon Jung
- Department of Nanomedical Engineering, College of Nanoscience & Nanotechnology, Pusan National University, Busan 609-735, Republic of Korea
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Högel F, Hoffmann S, Panzer S, Wimber J, Bühren V, Augat P. Biomechanical comparison of intramedullar versus extramedullar stabilization of intra-articular tibial plateau fractures. Arch Orthop Trauma Surg 2013; 133:59-64. [PMID: 23076657 DOI: 10.1007/s00402-012-1629-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Indexed: 12/01/2022]
Abstract
BACKGROUND Fractures of the proximal tibia occur very often and are a great challenge for trauma surgeons to stabilize. Although locked nails were developed to stabilize these fractures, this technique has not been sufficiently investigated. The purpose of this study was to biomechanically assess the stability of locked intramedullary nailing compared to locked plating. METHODS 16 fresh frozen human cadaveric tibiae were osteotomized in the meta-diaphyseal intersection with an osteotomy gap of 10 mm and a single osteotomy through the medial epicondyle to simulate a 41-C.2 fracture. Stabilization was performed with an angle stable locked Targon-TX nail (n = 8) and two additional canulated screws. The other testing group (n = 8) was treated with two canulated screws and a five-hole LCP-PLT. The bones were tested in a cyclic testing protocol with increasing loads under compression and a load sharing of 60 % through the medial tibial plateau and 40 % to the lateral side. Stiffness and fracture gap movement were measured and failure mode was assessed. RESULTS No significant differences were found between the two implants regarding load until failure. The stiffness of the intramedullary nailing group (927 N/mm) was statistically significantly higher than the stiffness of the plating group (564 N/mm). No differences were found for fracture gap movement in the z-axis. However, differences were found for dislocation of the proximal-lateral and proximal-medial fragments, with absolute values of 0.099 mm in the plate group and 0.66 mm in the nailing group at 800 N. Prior to failure, fracture gap movement was 0.22 mm for the plating group and 1.66 mm for the nailing group, a difference that was also statistically significantly different. The nailing group failed by screw cut-out while the plating group failed by screw breakage. CONCLUSION Nailing of proximal tibia fractures leads to a stiffer implant-bone construct than plating. Since no adverse effects were found after nailing it seems to be a good alternative to plating for intra-articular proximal tibia fractures, especially in patients with soft tissue problems.
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Affiliation(s)
- Florian Högel
- Institute for Biomechanics, BG Unfallklinik Murnau and PMU Salzburg., James Loeb Str. 7, 82418 Murnau, Germany.
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Abstract
Physical testing is commonly performed to answer important biomechanical questions in the treatment of patients with fractures and other orthopaedic conditions. However, a variety of mistakes that are made in performing such investigations can severely limit their impact. The goal of this article is to discuss important aspects of study design to consider when planning for biomechanical investigations so that the studies can provide maximal benefit to the field. The best mechanical investigations begin with a good research question, one that comes out of patient care experience, is clearly defined, and can be stated concisely. The first practical issue to be considered is often choosing the type of physical specimens to be tested to address the research question. A related issue involves determining how many specimens will be needed to answer the posed mechanical question. Cadavers are generally still the closest to the actual clinical situation, but they are limited by interspecimen variability, which often requires a matched pair design that can address only one question. Simulated bone specimens limit variability and can replicate normal and osteoporotic bone. In planning the physical testing, the critical mechanical variables involved in answering the research question must be identified and due consideration given to deciding how best to measure them. Another important issue that arises relates to whether or not single static loadings will suffice in the testing (eg, to study construct stiffness) or whether cyclic dynamic testing is necessary (eg, to study late failure likely attributable to fatigue). To summarize, experimental design should be carefully planned before initiating mechanical testing. Sample size calculations should be performed to ensure adequate power and that clinically relevant differences can be detected. This pregame analysis can save significant time and cost and greatly increase the likelihood that the results will advance knowledge.
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The protective effect of locking screw placement on nonlocking screw extraction torque in an osteoporotic supracondylar femur fracture model. J Orthop Trauma 2012; 26:523-7. [PMID: 22430520 DOI: 10.1097/bot.0b013e318238c086] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To examine the impact of number and position of locking screws in the diaphyseal portion of an osteoporotic distal femoral fracture model with hybrid fixation. METHODS Four groups containing 5 osteoporotic bone models were used with varying combinations of diaphyseal screw fixation: 4 nonlocking screws (control); 1 locking screw adjacent to the osteotomy and 3 nonlocking screws; 1 locking screw in the most proximal screw hole of the plate and 3 nonlocking screws; and 2 locking screws at opposite ends of the diaphyseal fixation with 2 nonlocking screws in between. Fixation in the distal articular segment was identical in all constructs. Testing was performed for 50,000 cycles at 2 Hz using simultaneous axial compression (700 N) and bidirectional torque (±5 Nm) applied along the long axis of the bone. All screws were inserted with 4 Nm of torque. RESULTS The extraction torque for nonlocking screws in those specimens that had a locking screw nearest the osteotomy was significantly greater than those that did not (P = 0.037). In addition, the 10 constructs with a locking screw nearest the osteotomy had no failures compared with 5 of 10 failures in those without a locking screw in this position (P = 0.033). CONCLUSIONS The placement of a locking screw adjacent to the osteotomy was more beneficial in protecting against failure and maintaining the extraction torque of neighboring proximal nonlocking screws. No benefit in adjacent screw extraction torque was seen with a locking screw proximal in the diaphysis. Two locking screws at opposite ends of the diaphyseal fixation were not superior to a single locking screw adjacent to the osteotomy in failure rates or screw extraction torque.
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Abstract
OBJECTIVE To determine whether locking plates offer an advantage in fixation of fractures in osteoporotic humeral bone. DESIGN Biomechanical testing of 18 matched pairs of osteoporotic human cadaver humeri plated posteriorly with either all locked or all nonlocked screws. An established protocol was used to test the constructs with torque applied to a peak of ±10 Nm for 1000 cycles at 0.3 Hz or until failure. Eighteen pairs were tested for failure, 11 pairs were tested for cycles survived, and 10 pairs were tested for stiffness. SETTING University biomechanical laboratory. MAIN OUTCOME MEASUREMENTS Percentage surviving testing, mean cycles survived, and stiffness. RESULTS We observed catastrophic failure of the constructs in 47% of the samples. Humeri plated with nonlocking plates failed at a higher rate than those with locking plates (67% nonlocking vs 28% locking, n = 18 pairs, P = 0.008). Locking constructs also outperformed nonlocking constructs in mean cycles survived (707 cycles locking, 345 cycles nonlocking, n = 11 pairs, P < 0.05) and stiffness at 10 cycles (0.853 Nm/degree locking vs 0.416 Nm/degree nonlocking, n = 10 pairs, P < 0.001). CONCLUSIONS Locking plates were shown to provide improved mechanical performance over nonlocking plates in torsional cyclic loading in a osteoporotic cadaveric fracture model. Our results confirm general conclusions of previous work that used a synthetic bone model of osteoporosis, but we found a high rate of catastrophic failure, questioning the validity of the previously published synthetic model of osteoporosis (overdrilling of synthetic bone) for this application.
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Yánez A, Cuadrado A, Carta JA, Garcés G. Screw locking elements: a means to modify the flexibility of osteoporotic fracture fixation with DCPs without compromising system strength or stability. Med Eng Phys 2011; 34:717-24. [PMID: 21982962 DOI: 10.1016/j.medengphy.2011.09.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 09/10/2011] [Accepted: 09/15/2011] [Indexed: 11/18/2022]
Abstract
This paper analyses whether it is possible to use dynamic compression plates (DCPs) and screw locking elements (SLEs) to vary the flexibility of osteoporotic fracture fixation without compromising the strength and stability of the construct. Compression, torsion and four-point bending static strength tests were conducted. Cyclic load tests of up to 10,000 load cycles were also carried out to determine stiffness performance. Four fixation systems were mounted onto polyurethane bone models. Group 1 consists of the DCP and six cortical screws. Group 2, idem, but with the addition of two SLEs. Group 3, idem, but with the addition of six SLEs. Group 4 used the locking compression plate (LCP) and locking screws. The results indicated no significant difference (p>0.05) in the strength of groups 2-4. It was also observed that the torsional stiffness of group 3 (0.30 Nm/°) was higher than that of group 2 (0.23 Nm/°) and similar to that of group 4 (0.28 Nm/°). Compression stiffness of group 4 (124 N/mm) was higher than that of group 2 (102 N/mm), but lower than that of group 3 (150 N/mm). No notable differences were observed for structural bending stiffness. It is concluded that by using the DCP with SLEs it is possible to modify the stiffness of the fixation construct for the repair of osteoporotic fractures and, in this way, facilitate the conditions suitable on secondary bone healing.
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Affiliation(s)
- A Yánez
- Department of Mechanical Engineering, Biomechanical Laboratory, Las Palmas University, Las Palmas de Gran Canaria, Spain
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Denard PJ, Doornink J, Phelan D, Madey SM, Fitzpatrick DC, Bottlang M. Biplanar fixation of a locking plate in the diaphysis improves construct strength. Clin Biomech (Bristol, Avon) 2011; 26:484-90. [PMID: 21216509 DOI: 10.1016/j.clinbiomech.2010.12.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 12/07/2010] [Accepted: 12/07/2010] [Indexed: 02/07/2023]
Abstract
BACKGROUND Elevation of a locking plate over the bone surface not only supports biological fixation, but also decreases the torsional strength of the fixation construct. Biplanar fixation by means of a staggered screw hole arrangement may combat this decreased torsional strength caused by plate elevation. This biomechanical study evaluated the effect of biplanar fixation on the torsional strength of locking plate fixation in the femoral diaphysis. METHODS Custom titanium plates were manufactured with either a linear or staggered hole pattern to evaluate planar and biplanar fixation, respectively. Fixation strength under torsional loading was evaluated in surrogates of the femoral diaphysis representative of osteoporotic and non-osteoporotic bone. Furthermore, fixation strength was determined for plate fixation with unicortical or bicortical locking screws. Five specimens per configuration were loaded to failure in torsion to determine their strength, stiffness, and failure mode. FINDINGS In osteoporotic bone, biplanar fixation was 32% stronger (P=0.01) than planar fixation when unicortical screws were used and 9% stronger (P=0.02) when bicortical screws were used. In non-osteoporotic bone, biplanar fixation was 55% stronger (P<0.001) than planar fixation when unicortical screws were used and 42% (P<0.001) stronger when bicortical screws were used. INTERPRETATION A biplanar screw configuration improves the torsional strength of diaphyseal plate fixation relative to a planar configuration in both osteoporotic and normal bone. With biplanar fixation, unicortical screws provide the same fixation strength as bicortical screws in non-osteoporotic bone.
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Affiliation(s)
- Patrick J Denard
- Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, Portland, OR 97232, USA
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Sokol SC, Amanatullah DF, Curtiss S, Szabo RM. Biomechanical properties of volar hybrid and locked plate fixation in distal radius fractures. J Hand Surg Am 2011; 36:591-7. [PMID: 21463723 DOI: 10.1016/j.jhsa.2010.12.032] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 12/15/2010] [Accepted: 12/16/2010] [Indexed: 02/02/2023]
Abstract
PURPOSE We compare the biomechanical properties of a volar hybrid construct to an all-locking construct in an osteoporotic and normal comminuted distal radius fracture model. METHODS Groups of 28 normal, 28 osteoporotic, and 28 over-drilled osteoporotic left distal radius synthetic bones were used. The normal group consisted of synthetic bone with a standard foam core. The osteoporotic group consisted of synthetic bone with decreased foam core density. The over-drilled osteoporotic group consisted of synthetic bone with decreased foam core density and holes drilled with a 2.3 mm drill, instead of the standard 2.0 mm drill, to simulate the lack of purchase in osteoporotic bone. Within each group, 14 synthetic bones were plated with a volar locking plate using an all-locking screw construct, and 14 synthetic bones were plated with a volar locking plate using a hybrid screw construct (ie, both locking and nonlocking screws). A 1-cm dorsal wedge osteotomy was created with the apex 2 cm from the volar surface of the lunate facet. Each specimen was mounted to a materials testing machine, using a custom-built, standardized axial compression jig. Axial compression was delivered at 1 N/s over 3 cycles from 20 N to 100 N to establish stiffness. Each sample was stressed to failure at 1 mm/s until 5 mm of permanent deformation occurred. RESULTS Our results show no difference in construct stiffness and load at failure between the all-locking and hybrid constructs in the normal, osteoporotic, or over-drilled osteoporotic synthetic bone models. All specimens failed by plate bending at the osteotomy site with loss of height. CLINICAL RELEVANCE Although volar locking plates are commonly used for the treatment of distal radius fractures, the ideal screw configuration has not been determined. Hybrid fixation has comparable biomechanical properties to all locking constructs in the fixation of metaphyseal fractures about the knee and shoulder and might also have a role in the fixation of distal radius fractures.
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Affiliation(s)
- Shima C Sokol
- Department of Orthopaedic Surgery, University of California, Davis, Sacramento, CA, USA
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Lee CY, Chan SH, Lai HY, Lee ST. A method to develop an in vitro osteoporosis model of porcine vertebrae: histological and biomechanical study. J Neurosurg Spine 2011; 14:789-98. [PMID: 21395393 DOI: 10.3171/2010.12.spine10453] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The porcine spine is widely used as an alternative to the human spine for both in vivo and in vitro spinal biomechanical studies because of the limited availability and high cost of human specimens. The aim of this study was to develop a reproducible in vitro osteoporotic vertebral model for spinal implant investigations. METHODS Four mature domestic porcine lumbar spines (L1-5) were obtained. An in vitro decalcification method was used to decrease the mineral content of the porcine vertebrae, with Ca-chelating agents (0.5 M EDTA solution, pH 7.4) that altered the bone mineral density (BMD). Lumbar-spine area BMD was evaluated using dual-energy x-ray absorptiometry; spine volumetric BMD and spine geometry were assessed by central quantitative CT scanning to monitor the time it took the decalcification process to induce the WHO-defined standard of osteoporosis. Micro-computed topography provided information on the 3D microarchitecture of the lumbar vertebrae before and after decalcification with EDTA. Hematoxylin and eosin staining of lumbar vertebrae was performed. Both the control (5 specimens) and osteoporotic vertebrae (5 specimens) were biomechanically tested to measure compressive strength. RESULTS The differences in area BMD measurements before and after the demineralizing processes were statistically significant (p < 0.001). The results of the compression test before and after the demineralizing processes were also statistically significant (p < 0.001). CONCLUSIONS The data imply that the acid demineralizing process may be useful for producing a vertebra that has some biomechanical properties that are consistent with osteoporosis in humans.
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Affiliation(s)
- Ching-yi Lee
- Department of Neurosurgery, Chang Gung University & Chang Gung Memorial Hospital, Taoyuan, Taiwan
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Bottlang M, Doornink J, Lujan TJ, Fitzpatrick DC, Marsh JL, Augat P, von Rechenberg B, Lesser M, Madey SM. Effects of construct stiffness on healing of fractures stabilized with locking plates. J Bone Joint Surg Am 2010; 92 Suppl 2:12-22. [PMID: 21123589 PMCID: PMC2995582 DOI: 10.2106/jbjs.j.00780] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Michael Bottlang
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97232. E-mail address for M. Bottlang:
| | - Josef Doornink
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97232. E-mail address for M. Bottlang:
| | - Trevor J. Lujan
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97232. E-mail address for M. Bottlang:
| | - Daniel C. Fitzpatrick
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97232. E-mail address for M. Bottlang:
| | - J. Lawrence Marsh
- University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242
| | - Peter Augat
- Institute of Biomechanics, Prof. Kuentscher Strasse 8, 82418 Murnau, Germany
| | - Brigitte von Rechenberg
- Musculoskeletal Research Unit, Equine Department, Vetsuisse Faculty, University of Zürich, Winterthurerstrasse 260, CH 8057 Zürich, Switzerland
| | - Maren Lesser
- Musculoskeletal Research Unit, Equine Department, Vetsuisse Faculty, University of Zürich, Winterthurerstrasse 260, CH 8057 Zürich, Switzerland
| | - Steven M. Madey
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97232. E-mail address for M. Bottlang:
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Effects of Hybrid Plating With Locked and Nonlocked Screws on the Strength of Locked Plating Constructs in the Osteoporotic Diaphysis. ACTA ACUST UNITED AC 2010; 69:411-7. [DOI: 10.1097/ta.0b013e3181ec9417] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Less rigid stable fracture fixation in osteoporotic bone using locked plates with near cortical slots. Injury 2010; 41:652-6. [PMID: 20236642 DOI: 10.1016/j.injury.2010.02.022] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2009] [Revised: 01/22/2010] [Accepted: 02/15/2010] [Indexed: 02/02/2023]
Abstract
INTRODUCTION Locked plating leads to improved fixation in osteoporotic bone. In addition, experimental data suggest that overall construct stiffness is increased. Ideal stiffness may be significantly less than that achieved with these locked constructs, and overly stiff constructs may lead to impaired fracture healing and stress concentration at the ends of the plate. In osteoporotic bone, this stiffness mismatch can be even more pronounced. We hypothesized that substituting slots for holes in the near cortex under a locked plate would lead to predictably lower stiffness without diminishing implant stability. METHODS Osteoporotic bone substitute segments were used. Locking screws and plates were applied to each specimen using either standard holes or near cortical slots. The slots were designed to allow axial displacement of the screw in the near cortex only, while continuing to provide some torsional stability. Mechanical testing was performed using a progressive dynamic displacement load protocol to determine failure and stiffness. Next, cyclic axial loading was performed with a physiologic load for 10,000 cycles to determine change in stiffness with cycling. Outcomes were compared between groups using Mann-Whitney U tests. RESULTS In the dynamic displacement tests, the slotted specimens reached both maximum load and failure load at a significantly greater displacement than the non-slot group (p=0.008), indicating later failure. The magnitude of the maximum load achieved was no different between groups. In the cyclic loading tests, the axial stiffness in the slotted group was significantly lower (1199 N/mm) than the non-slotted group (3538 N/mm; p<0.05 at all cycles). Stiffness did not change significantly in either group over the course of cycling. DISCUSSION The ability to predictably adjust the axial stiffness of locked plating constructs is critical, particularly in osteoporotic bone. The use of near cortical slots decreases axial stiffness of locking plates, while maintaining fixation stability. This may allow the surgeon to more closely tailor the construct stiffness to the clinical situation to minimize stiffness mismatches and complications.
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Eberle S, Gerber C, von Oldenburg G, Högel F, Augat P. A Biomechanical Evaluation of Orthopaedic Implants for Hip Fractures by Finite Element Analysis and In-Vitro Tests. Proc Inst Mech Eng H 2010; 224:1141-52. [PMID: 21138232 DOI: 10.1243/09544119jeim799] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The aim of this study was to test the hypothesis that a reinforced gamma nail for the fixation of subtrochanteric fractures would experience less stress during loading compared with a common gamma nail. The issue of whether the use of the stronger implant would result in more stress shielding in the surrounding bone was also addressed. A finite element analysis (FEA) of a synthetic bone was employed to calculate the stress distribution in implant and bone for two fracture types (AO 31-A3.1 and AO 31-A3.3). The FEA was validated by mechanical tests on six synthetic femurs. To test the hypothesis in vitro, mechanical tests on six pairs of fresh-frozen human femurs were conducted. The femurs were supplied with a common or a reinforced gamma nail in a cross-over study design. Strains were measured on the nail shaft to quantify the loading of the nail. The FEA resulted in 3—51 per cent lower stresses for the reinforced gamma nail. No increase in stress shielding could be observed. In the in-vitro tests, the reinforced gamma nail experienced less strain during loading ( p < 0.016). The study demonstrated the benefit of a reinforced gamma nail in subtrochanteric fractures. It experienced less stress but did not result in more stress shielding.
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Affiliation(s)
- S Eberle
- Institute of Biomechanics, Trauma Center Murnau, Murnau, Germany
| | - C Gerber
- Stryker Osteosynthesis, Schoenkirchen/Kiel, Germany
| | | | - F Högel
- Institute of Biomechanics, Trauma Center Murnau, Murnau, Germany
| | - P Augat
- Institute of Biomechanics, Trauma Center Murnau, Murnau, Germany
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Bottlang M, Doornink J, Fitzpatrick DC, Madey SM. Far cortical locking can reduce stiffness of locked plating constructs while retaining construct strength. J Bone Joint Surg Am 2009; 91:1985-94. [PMID: 19651958 PMCID: PMC2714811 DOI: 10.2106/jbjs.h.01038] [Citation(s) in RCA: 158] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Several strategies to reduce construct stiffness have been proposed to promote secondary bone healing following fracture fixation with locked bridge plating constructs. However, stiffness reduction is typically gained at the cost of construct strength. In the present study, we tested whether a novel strategy for stiffness reduction, termed far cortical locking, can significantly reduce the stiffness of a locked plating construct while retaining its strength. METHODS Locked plating constructs and far cortical locking constructs were tested in a diaphyseal bridge plating model of the non-osteoporotic femoral diaphysis to determine construct stiffness in axial compression, torsion, and bending. Subsequently, constructs were dynamically loaded until failure in each loading mode to determine construct strength and failure modes. Finally, failure tests were repeated in a validated model of the osteoporotic femoral diaphysis to determine construct strength and failure modes in a worst-case scenario of bridge plating in osteoporotic bone. RESULTS Compared with the locked plating constructs, the initial stiffness of far cortical locking constructs was 88% lower in axial compression (p < 0.001), 58% lower in torsion (p < 0.001), and 29% lower in bending (p < 0.001). Compared with the locked plating constructs, the strength of far cortical locking constructs was 7% lower (p = 0.005) and 16% lower (p < 0.001) under axial compression in the non-osteoporotic and osteoporotic diaphysis, respectively. However, far cortical locking constructs were 54% stronger (p < 0.001) and 9% stronger (p = 0.04) under torsion and 21% stronger (p < 0.001) and 20% stronger (p = 0.02) under bending than locked plating constructs in the non-osteoporotic and osteoporotic diaphysis, respectively. Within the initial stiffness range, far cortical locking constructs generated nearly parallel interfragmentary motion. Locked plating constructs generated significantly less motion at the near cortex adjacent to the plate than at the far cortex (p < 0.01). CONCLUSIONS Far cortical locking significantly reduces the axial stiffness of a locked plating construct. This gain in flexibility causes only a modest reduction in axial strength and increased torsional and bending strength.
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Affiliation(s)
- Michael Bottlang
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97215
| | - Josef Doornink
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97215
| | | | - Steven M. Madey
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97215
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Bottlang M, Doornink J, Byrd GD, Fitzpatrick DC, Madey SM. A nonlocking end screw can decrease fracture risk caused by locked plating in the osteoporotic diaphysis. J Bone Joint Surg Am 2009; 91:620-7. [PMID: 19255222 DOI: 10.2106/jbjs.h.00408] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Locking plates transmit load through fixed-angle locking screws instead of relying on plate-to-bone compression. Therefore, locking screws may induce higher stress at the screw-bone interface than that seen with conventional nonlocked plating. This study investigated whether locked plating in osteoporotic diaphyseal bone causes a greater periprosthetic fracture risk than conventional plating because of stress concentrations at the plate end. It further investigated the effect of replacing the locked end screw with a conventional screw on the strength of the fixation construct. METHODS Three different bridge-plate constructs were applied to a validated surrogate of the osteoporotic femoral diaphysis. Constructs were tested dynamically to failure in bending, torsion, and axial loading to determine failure loads and failure modes. A locked plating construct was compared with a nonlocked conventional plating construct. Subsequently, the outermost locking screw in locked plating constructs was replaced with a conventional screw to reduce stress concentrations at the plate end. RESULTS Compared with the conventional plating construct, the locked plating construct was 22% weaker in bending (p = 0.013), comparably strong in torsion (p = 0.05), and 15% stronger in axial compression (p = 0.017). Substituting the locked end screw with a conventional screw increased the construct strength by 40% in bending (p = 0.001) but had no significant effect on construct strength under torsion (p = 0.22) and compressive loading (p = 0.53) compared with the locked plating construct. Under bending, all constructs failed by periprosthetic fracture. CONCLUSIONS Under bending loads, the focused load transfer of locking plates through fixed-angle screws can increase the periprosthetic fracture risk in the osteoporotic diaphysis compared with conventional plates. Replacing the outermost locking screw with a conventional screw reduced the stress concentration at the plate end and significantly increased the bending strength of the plating construct compared with an all-locked construct (p = 0.001).
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Affiliation(s)
- Michael Bottlang
- Legacy Biomechanics Laboratory, 1225 N.E. 2nd Avenue, Portland, OR 97215, USA
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Fitzpatrick DC, Doornink J, Madey SM, Bottlang M. Relative stability of conventional and locked plating fixation in a model of the osteoporotic femoral diaphysis. Clin Biomech (Bristol, Avon) 2009; 24:203-9. [PMID: 19070409 PMCID: PMC2653054 DOI: 10.1016/j.clinbiomech.2008.11.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Revised: 10/31/2008] [Accepted: 11/04/2008] [Indexed: 02/07/2023]
Abstract
BACKGROUND This study investigated the stiffness and strength of bridge plating with uni-cortical and bi-cortical locking plate constructs relative to a conventional, non-locked construct in the osteoporotic femoral diaphysis. METHODS Four bridge plating configurations were applied to a validated model of the osteoporotic femoral diaphysis. A non-locked conventional configuration served as baseline. Locked configurations included bi-cortical locked plating, uni-cortical locked plating and mix-mode locked plating, which combined uni and bi-cortical locking screws. For all configurations, an 11-hole plate was applied with 4.5-mm screws placed in the 1st, 3rd, and 5th plate hole. Five specimens of each configuration were dynamically loaded until failure in torsion, axial compression, and bending to determine construct stiffness, strength and failure modes. FINDINGS In torsion and bending, locked plating constructs provided a significantly lower stiffness and strength than the conventional construct. The uni-cortical locked construct was 69% weaker (P<0.001) in torsion than the conventional construct, but its torsional strength improved 73% (P<0.001) by adding one bi-cortical locked screw. In axial compression, construct stiffness varied by less than 10% between the four groups. However, the bi-cortical and mixed-mode locked constructs provided a significant increase in strength of 12% (P=0.001) and 11% (P=0.002), respectively, compared to the conventional construct. INTERPRETATIONS Locked plating in the osteoporotic diaphysis can improve fixation strength under axial loading, but may reduce fixation strength in bending and torsion compared to conventional plating. Adding one bi-cortical locked screw to an otherwise uni-cortical construct is recommended to improve torsional strength.
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Affiliation(s)
| | - Josef Doornink
- Biomechanics Laboratory, Legacy Research, Technology Center, Portland, OR 97232
| | - Steven M. Madey
- Biomechanics Laboratory, Legacy Research, Technology Center, Portland, OR 97232
| | - Michael Bottlang
- Biomechanics Laboratory, Legacy Research, Technology Center, Portland, OR 97232
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Patel PSD, Shepherd DET, Hukins DWL. Compressive properties of commercially available polyurethane foams as mechanical models for osteoporotic human cancellous bone. BMC Musculoskelet Disord 2008; 9:137. [PMID: 18844988 PMCID: PMC2575212 DOI: 10.1186/1471-2474-9-137] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 10/09/2008] [Indexed: 11/23/2022] Open
Abstract
Background Polyurethane (PU) foam is widely used as a model for cancellous bone. The higher density foams are used as standard biomechanical test materials, but none of the low density PU foams are universally accepted as models for osteoporotic (OP) bone. The aim of this study was to determine whether low density PU foam might be suitable for mimicking human OP cancellous bone. Methods Quasi-static compression tests were performed on PU foam cylinders of different lengths (3.9 and 7.7 mm) and of different densities (0.09, 0.16 and 0.32 g.cm-3), to determine the Young's modulus, yield strength and energy absorbed to yield. Results Young's modulus values were 0.08–0.93 MPa for the 0.09 g.cm-3 foam and from 15.1–151.4 MPa for the 0.16 and 0.32 g.cm-3 foam. Yield strength values were 0.01–0.07 MPa for the 0.09 g.cm-3 foam and from 0.9–4.5 MPa for the 0.16 and 0.32 g.cm-3 foam. The energy absorbed to yield was found to be negligible for all foam cylinders. Conclusion Based on these results, it is concluded that 0.16 g.cm-3 PU foam may prove to be suitable as an OP cancellous bone model when fracture stress, but not energy dissipation, is of concern.
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Affiliation(s)
- Purvi S D Patel
- School of Mechanical Engineering, University of Birmingham, Edgbaston, Birmingham, UK.
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