Displaying publications 21 - 40 of 139 in total

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  1. Fulltext The HUKM Spinal Instrumentation System for adolescent idiopathic scoliosis. A biomechanical comparison study using finite element analysis
    Azlan AM, Mohammad AR, Ariffin AK
    Med J Malaysia, 2005 Jul;60 Suppl C:30-4.
    PMID: 16381280 MyJurnal
    This finite element analysis is aimed at comparing relative stiffness of three different posterior instrumentation constructs: the Hospital Universiti Kebangsaan Malaysia Spinal Instrumentation System (HUKM-SIS), the Cotrell-Dubousset Instrumentation (CDI) and Harrington Instrumentation System (HIS), used in the treatment of adolescent idiopathic scoliosis (AIS). The constructs were tested under various loads using MSC Patran 2001 r2a. Under increasing flexion loads, there was a linearly corresponding increase in deflection magnitudes for all constructs on the load-deflection curve. The CDI was the stiffest construct under axial, forward flexion and extension loads, followed by the HUKM-SIS and HIS. Under lateral bending loads, the HUKM-SIS construct was the stiffest followed by CDI and HIS. The HUKM-SIS construct was stiffer than HIS under torsional loads. We conclude that multiple pedicle screws increase the stiffness of posterior instrumentation constructs under all loads and inter-segmental spinous processes wiring increase the stiffness against lateral bending.
    Matched MeSH terms: Finite Element Analysis
  2. Fulltext Design process of cementless femoral stem using a nonlinear three dimensional finite element analysis
    Baharuddin MY, Salleh ShH, Zulkifly AH, Lee MH, Noor AM, A Harris AR, et al.
    BMC Musculoskelet Disord, 2014;15:30.
    PMID: 24484753 DOI: 10.1186/1471-2474-15-30
    Minimal available information concerning hip morphology is the motivation for several researchers to study the difference between Asian and Western populations. Current use of a universal hip stem of variable size is not the best option for all femur types. This present study proposed a new design process of the cementless femoral stem using a three dimensional model which provided more information and accurate analysis compared to conventional methods.
    Matched MeSH terms: Finite Element Analysis*
  3. Fabrication of low-cost, cementless femoral stem 316L stainless steel using investment casting technique
    Baharuddin MY, Salleh ShH, Suhasril AA, Zulkifly AH, Lee MH, Omar MA, et al.
    Artif Organs, 2014 Jul;38(7):603-8.
    PMID: 24404766 DOI: 10.1111/aor.12222
    Total hip arthroplasty is a flourishing orthopedic surgery, generating billions of dollars of revenue. The cost associated with the fabrication of implants has been increasing year by year, and this phenomenon has burdened the patient with extra charges. Consequently, this study will focus on designing an accurate implant via implementing the reverse engineering of three-dimensional morphological study based on a particular population. By using finite element analysis, this study will assist to predict the outcome and could become a useful tool for preclinical testing of newly designed implants. A prototype is then fabricated using 316L stainless steel by applying investment casting techniques that reduce manufacturing cost without jeopardizing implant quality. The finite element analysis showed that the maximum von Mises stress was 66.88 MPa proximally with a safety factor of 2.39 against endosteal fracture, and micromotion was 4.73 μm, which promotes osseointegration. This method offers a fabrication process of cementless femoral stems with lower cost, subsequently helping patients, particularly those from nondeveloped countries.
    Matched MeSH terms: Finite Element Analysis
  4. Biomechanical analysis of the wrist arthroplasty in rheumatoid arthritis: a finite element analysis
    Bajuri MN, Abdul Kadir MR, Murali MR, Kamarul T
    Med Biol Eng Comput, 2013 Feb;51(1-2):175-86.
    PMID: 23124814 DOI: 10.1007/s11517-012-0982-9
    The total replacement of wrists affected by rheumatoid arthritis (RA) has had mixed outcomes in terms of failure rates. This study was therefore conducted to analyse the biomechanics of wrist arthroplasty using recently reported implants that have shown encouraging results with the aim of providing some insights for the future development of wrist implants. A model of a healthy wrist was developed using computed tomography images from a healthy volunteer. An RA model was simulated based on all ten general characteristics of the disease. The ReMotion ™ total wrist system was then modelled to simulate total wrist arthroplasty (TWA). Finite element analysis was performed with loads simulating the static hand grip action. The results show that the RA model produced distorted patterns of stress distribution with tenfold higher contact pressure than the healthy model. For the TWA model, contact pressure was found to be approximately fivefold lower than the RA model. Compared to the healthy model, significant improvements were observed for the TWA model with minor variations in the stress distribution. In conclusion, the modelled TWA reduced contact pressure between bones but did not restore the stress distribution to the normal healthy condition.
    Matched MeSH terms: Finite Element Analysis*
  5. A hyperelastic fibre-reinforced continuum model of healing tendons with distributed collagen fibre orientations
    Bajuri MN, Isaksson H, Eliasson P, Thompson MS
    Biomech Model Mechanobiol, 2016 12;15(6):1457-1466.
    PMID: 26951049
    The healing process of ruptured tendons is problematic due to scar tissue formation and deteriorated material properties, and in some cases, it may take nearly a year to complete. Mechanical loading has been shown to positively influence tendon healing; however, the mechanisms remain unclear. Computational mechanobiology methods employed extensively to model bone healing have achieved high fidelity. This study aimed to investigate whether an established hyperelastic fibre-reinforced continuum model introduced by Gasser, Ogden and Holzapfel (GOH) can be used to capture the mechanical behaviour of the Achilles tendon under loading during discrete timepoints of the healing process and to assess the model's sensitivity to its microstructural parameters. Curve fitting of the GOH model against experimental tensile testing data of rat Achilles tendons at four timepoints during the tendon repair was used and achieved excellent fits ([Formula: see text]). A parametric sensitivity study using a three-level central composite design, which is a fractional factorial design method, showed that the collagen-fibre-related parameters in the GOH model-[Formula: see text] and [Formula: see text]-had almost equal influence on the fitting. This study demonstrates that the GOH hyperelastic fibre-reinforced model is capable of describing the mechanical behaviour of healing tendons and that further experiments should focus on establishing the structural and material parameters of collagen fibres in the healing tissue.
    Matched MeSH terms: Finite Element Analysis
  6. Mechanical and functional assessment of the wrist affected by rheumatoid arthritis: A finite element analysis
    Bajuri MN, Kadir MR, Raman MM, Kamarul T
    Med Eng Phys, 2012 Nov;34(9):1294-302.
    PMID: 22277308 DOI: 10.1016/j.medengphy.2011.12.020
    Understanding the pathomechanics involved in rheumatoid arthritis (RA) of the wrist provides valuable information, which will invariably allow various therapeutic possibilities to be explored. The computational modelling of this disease permits the appropriate simulation to be conducted seamlessly. A study that underpins the fundamental concept that produces the biomechanical changes in a rheumatoid wrist was thus conducted through the use of finite element method. The RA model was constructed from computed tomography datasets, taking into account three major characteristics: synovial proliferation, cartilage destruction and ligamentous laxity. As control, a healthy wrist joint model was developed in parallel and compared. Cartilage was modelled based on the shape of the articulation while the ligaments were modelled with linear spring elements. A load-controlled analysis was performed simulating physiological hand grip loading conditions. The results demonstrated that the diseased model produced abnormal wrist extension and stress distribution as compared to the healthy wrist model. Due to the weakening of the ligaments, destruction of the cartilage and lower bone density, the altered biomechanical stresses were particularly evident at the radioscaphoid and capitolunate articulations which correlate to clinical findings. These results demonstrate the robust finding of the developed RA wrist model, which accurately predicted the pathological process.
    Matched MeSH terms: Finite Element Analysis*
  7. Assessment of 3-D nasal airway morphology in Southeast Asian adults with obstructive sleep apnea using acoustic rhinometry
    Banabilh SM, Suzina AH, Mohamad H, Dinsuhaimi S, Samsudin AR, Singh GD
    Clin Oral Investig, 2010 Oct;14(5):491-8.
    PMID: 19806371 DOI: 10.1007/s00784-009-0342-9
    The aim of the present study is to investigate nasal airway morphology in Asian adults with and without obstructive sleep apnea (OSA) using acoustic rhinometry (AR), principal components analysis (PCA), and 3-D finite-element analysis (FEA). One hundred eight adult Malays aged 18-65 years (mean ± SD, 33.2 ± 13.31) underwent clinical examination and limited channel polysomnography, providing 54 patients with OSA and 54 non-OSA controls. The mean minimal cross section area 1 (MCA1) and the mean minimal cross sectional area 2 (MCA2) were obtained from AR for all subjects and subjected to t tests. The OSA and control nasal airways were reconstructed in 3-D and subjected to PCA and FEA. The mean MCA1 and MCA2 using AR were found to be significantly smaller in the OSA group than in the control group (p < 0.001). Comparing the 3-D OSA and control nasal airways using PCA, the first two eigenvalues accounted for 94% of the total shape change, and statistical differences were found (p < 0.05). Similarly, comparing the nasal airways using FEA, the 3-D mean OSA nasal airway was significantly narrower in the OSA group compared to the control group. Specifically, decreases in size of approx. 10-22% were found in the nasal valve/head of inferior turbinate area. In conclusion, differences in nasal airway morphology are present when comparing patients with OSA to controls. These differences need to be recognized as they can improve our understanding of the etiological basis of obstructive sleep apnea and facilitate its subsequent management.
    Matched MeSH terms: Finite Element Analysis
  8. Dental arch morphology in south-east Asian adults with obstructive sleep apnoea: geometric morphometrics
    Banabilh SM, Suzina AH, Dinsuhaimi S, Samsudin AR, Singh GD
    J Oral Rehabil, 2009 Mar;36(3):184-92.
    PMID: 19207445 DOI: 10.1111/j.1365-2842.2008.01915.x
    The association between dental arch morphology and the aetiology of obstructive sleep apnoea (OSA) is not clear. To compare dental arch morphology in 108 Asian adults with and without ''OSA, overnight'' hospital polysomnography was performed, and sleep reports were obtained for all subjects. Standardized digital photographs were also taken of the subjects' upper and lower study models. Using 25 homologous landmarks, mean OSA and control dental arch configurations were computed, and subjected to finite-element morphometry (FEM), t-tests and principal components analysis (PCA). Mean upper and lower OSA dental arch morphologies were statistically different from respective Control upper and lower arch morphologies (P < 0.05). FEM of the upper arch indicated that the mean OSA configuration was 7-11% narrower in the transverse plane in the incisor and canine regions when compared with the control configuration, and inter-landmark analysis (ILA) confirmed this finding. FEM for the lower arch indicated that the mean OSA configuration was 10-11% narrower in the antero-posterior plane in the pre-molar and molar regions, and confirmed by ILA. Using PCA, significant differences were also found between the two groups in the lower arch using the first two eigenvalues, which accounted for 90% of the total shape change (P < 0.001). Supporting their role as aetiological factors, size and shape differences in dental arch morphology are found in patients with OSA.
    Matched MeSH terms: Finite Element Analysis
  9. Cranial base and airway morphology in adult malays with obstructive sleep apnoea
    Banabilh SM, Suzina AH, Dinsuhaimi S, Singh GD
    Aust Orthod J, 2007 Nov;23(2):89-95.
    PMID: 18200785
    Obstructive sleep apnoea (OSA) has been described as a public health problem comparable to smoking in its impacts upon society.
    Matched MeSH terms: Finite Element Analysis
  10. Facial soft tissue features assessed with finite element analysis
    Banabilh SM, Rajion ZA, Samsudin AR, Singh GD
    Int J Orthod Milwaukee, 2006;17(4):17-20.
    PMID: 17256439
    Facial soft tissues are a major determinant of treatment choice. When Class I and Class II malocclusions were compared using finite-element analysis, morphologic differences were localized and quantified. This study highlights the importance of determining the timing, magnitude and direction offacial growth prior to treatment to achieve stable results.
    Matched MeSH terms: Finite Element Analysis*
  11. Dental arch shape and size in Malay schoolchildren with Class II malocclusion
    Banabilh SM, Rajion ZA, Samsudin R, Singh GD
    Aust Orthod J, 2006 Nov;22(2):99-103.
    PMID: 17203572
    To quantify and localise differences in Class I and Class II dental arches in Malay schoolchildren.
    Matched MeSH terms: Finite Element Analysis
  12. Fulltext Thermo-mechanical contact problems and elastic behaviour of single and double sides functionally graded brake disks with temperature-dependent material properties
    Bayat M, Alarifi IM, Khalili AA, El-Bagory TMAA, Nguyen HM, Asadi A
    Sci Rep, 2019 Oct 25;9(1):15317.
    PMID: 31653877 DOI: 10.1038/s41598-019-51450-z
    A thermo-elastic contact problem of functionally graded materials (FGMs) rotating brake disk with different pure brake pad areas under temperature dependent material properties is solved by Finite Element Method (FEM). The properties of brake disk change gradually from metal to ceramic by power-law distribution along the radial direction from the inner to the outer surface. Areas of the pure pad are changing while the vertical force is constant. The ratio of brake pad thickness to FGMs brake disk thickness is assumed 0.66. Two sources of thermal loads are considered: (1) Heat generation between the pad and brake disk due to contact friction, and (2) External thermal load due to a constant temperature at inner and outer surfaces. Mechanical responses of FGMs disk are compared with several pad contact areas. The results for temperature-dependent and temperature-independent material properties are investigated and presented. The results show that the absolute value of the shear stress in temperature-dependent material can be greater than that for temperature-independent material. The radial stress for some specific grading index (n = 1.5) is compressive near the inner surface for double contact while it is tensile for a single contact. It is concluded that the radial strain for some specific value of grading index (n = 1) is lower than other FGMs and pure double side contact brake disks.
    Matched MeSH terms: Finite Element Analysis
  13. Fulltext Systematic mechanical evaluation of electrospun gelatin meshes
    Butcher AL, Koh CT, Oyen ML
    J Mech Behav Biomed Mater, 2017 May;69:412-419.
    PMID: 28208112 DOI: 10.1016/j.jmbbm.2017.02.007
    Electrospinning is a simple and efficient process for producing sub-micron fibres. However, the process has many variables, and their effects on the non-woven mesh of fibres is complex. In particular, the effects on the mechanical properties of the fibre meshes are poorly understood. This paper conducts a parametric study, where the concentration and bloom strength of the gelatin solutions are varied, while all electrospinning process parameters are held constant. The effects on the fibrous meshes are monitored using scanning electron microscopy and mechanical testing under uniaxial tension. Mesh mechanical properties are relatively consistent, despite changes to the solutions, demonstrating the robustness of electrospinning. The gel strength of the solution is shown to have a statistically significant effect on the morphology, stiffness and strength of the meshes, while the fibre diameter has surprisingly little influence on the stiffness of the meshes. This experimental finding is supported by finite element analysis, demonstrating that the stiffness of the meshes is controlled by the volume fraction, rather than fibre diameter. Our results demonstrate the importance of understanding how electrospinning parameters influence the pore size of the meshes, as controlling fibre diameter alone is insufficient for consistent mechanical properties.
    Matched MeSH terms: Finite Element Analysis
  14. A comparative study on complete and implant retained denture treatments: a biomechanics perspective
    Chen J, Ahmad R, Suenaga H, Li W, Swain M, Li Q
    J Biomech, 2015 Feb 5;48(3):512-9.
    PMID: 25560272 DOI: 10.1016/j.jbiomech.2014.11.043
    Although implant-retained overdenture allows edentulous patients to take higher occlusal forces than the conventional complete dentures, the biomechanical influences have not been explored yet. Clinically, there is limited knowledge and means for predicting localized bone remodelling after denture treatment with and without implant support. By using finite element (FE) analysis, this article provides an in-silico approach to exploring the treatment effects on the oral mucosa and potential resorption of residual ridge under three different denture configurations in a patient-specific manner. Based on cone beam computerized tomography (CBCT) scans, a 3D heterogeneous FE model was created; and the supportive tissue, mucosa, was characterized as a hyperelastic material. A measured occlusal load (63N) was applied onto three virtual models, namely complete denture, two and four implant-retained overdentures. Clinically, the bone resorption was measured after one year in the two implant-retained overdenture treatment. Despite the improved stability and enhanced masticatory function, the implant-retained overdentures demonstrated higher hydrostatic stress in mucosa (43.6kPa and 39.9kPa for two and four implants) at the posterior ends of the mandible due to the cantilever effect, than the complete denture (33.4kPa). Hydrostatic pressure in the mucosa signifies a critical indicator and can be correlated with clinically measured bone resorption, pointing to severer mandibular ridge resorption posteriorly with implant-retained overdentures. This study provides a biomechanical basis for denture treatment planning to improve long-term outcomes with minimal residual ridge resorption.
    Matched MeSH terms: Finite Element Analysis
  15. Fulltext Thermal Delamination Modelling and Evaluation of Aluminium-Glass Fibre-Reinforced Polymer Hybrid
    Chow ZP, Ahmad Z, Wong KJ, Koloor SSR, Petrů M
    Polymers (Basel), 2021 Feb 04;13(4).
    PMID: 33557350 DOI: 10.3390/polym13040492
    This paper aims to propose a temperature-dependent cohesive model to predict the delamination of dissimilar metal-composite material hybrid under Mode-I and Mode-II delamination. Commercial nonlinear finite element (FE) code LS-DYNA was used to simulate the material and cohesive model of hybrid aluminium-glass fibre-reinforced polymer (GFRP) laminate. For an accurate representation of the Mode-I and Mode-II delamination between aluminium and GFRP laminates, cohesive zone modelling with bilinear traction separation law was implemented. Cohesive zone properties at different temperatures were obtained by applying trends of experimental results from double cantilever beam and end notched flexural tests. Results from experimental tests were compared with simulation results at 30, 70 and 110 °C to verify the validity of the model. Mode-I and Mode-II FE models compared to experimental tests show a good correlation of 5.73% and 7.26% discrepancy, respectively. Crack front stress distribution at 30 °C is characterised by a smooth gradual decrease in Mode-I stress from the centre to the edge of the specimen. At 70 °C, the entire crack front reaches the maximum Mode-I stress with the exception of much lower stress build-up at the specimen's edge. On the other hand, the Mode-II stress increases progressively from the centre to the edge at 30 °C. At 70 °C, uniform low stress is built up along the crack front with the exception of significantly higher stress concentrated only at the free edge. At 110 °C, the stress distribution for both modes transforms back to the similar profile, as observed in the 30 °C case.
    Matched MeSH terms: Finite Element Analysis
  16. Topology optimisation of spinal interbody cage for reducing stress shielding effect
    Chuah HG, Abd Rahim I, Yusof MI
    Comput Methods Biomech Biomed Engin, 2010 Jun;13(3):319-26.
    PMID: 19927241 DOI: 10.1080/10255840903208189
    The stress shielding effect is an event in which the replacement implant limits the load transferred to bone and the ineffective stress in the vertebrae causes bony growth to cease. In the present study, a 3D finite element L4-L5 model was developed and subjected to a 1200 N compression preload. Five groups of muscle forces were applied on L4 under flexion-extension, lateral bending and axial rotation. Topology optimisation was employed for reducing the stress shielding effect by removing the ineffective material from the design domain. The optimised design was designed with polyaryletheretherketone (PEEK) titanium and cortical materials to encounter the shielding response. The stress responses show that the new design increased the stress magnitude by at least 17.10, 18.11 and 18.43% in 4 Nm of flexion-extension, lateral bending and axial rotation, respectively. In conclusion, the material factor did not significantly alter the stress magnitude, but volume was the key factor in reducing the stress shielding effect.
    Matched MeSH terms: Finite Element Analysis
  17. Fulltext Seismic response of a light rail transit station equipped with braced viscous damper
    Fateh, A., Hejazi, F., Ramanathan, R.A., Jaffar, M.S.
    Pertanika Journal of Science & Technology, 2016;24(2):273-283.
    MyJurnal
    The use of the Light Rail Transit (LRT) system is currently preferred because LRT is sustainable,
    improves travel options and facilitates swift mobility in urban areas. Hence, the structural stability
    and safety of this public transportation system against seismic occurrences are indispensable. Given
    that these structures cannot be considered conventional frames because of their complex architectural
    design, focussing meticulously on reliable seismic design codes and structural rehabilitation techniques
    is vital for the design of the lateral resistance system. One Malaysian LRT station is considered in this
    study, and the seismic response of this train station when equipped with supplementary viscous damper
    devices is evaluated. Thus, the LRT station is modelled through finite element simulation. The methods
    of seismic analysis are limited to linear seismic analyses, namely, response spectrum and time history
    analyses. Results derived in this study show a significant improvement in structural response when the
    station is fitted with dampers; approximately 40% reduction in displacement is observed at the top joint
    of the roof. Furthermore, the lateral base shears decrease by approximately 70%.
    Matched MeSH terms: Finite Element Analysis
  18. New head models extracted from thermal infrared (IR) images for dosimetry computations
    Gasmelseed A
    Comput Methods Biomech Biomed Engin, 2011 Jul;14(7):665-71.
    PMID: 21480080 DOI: 10.1080/10255842.2011.563738
    In electromagnetic dosimetry, anatomical human models are commonly obtained by segmentation of magnetic resonance imaging or computed tomography scans. In this paper, a human head model extracted from thermal infrared images is examined in terms of its applicability to specific absorption rate (SAR) calculations. Since thermal scans are two-dimensional (2D) representation of surface temperature, this allows researchers to overcome the extensive computational demand associated with 3D simulation. The numerical calculations are performed using the finite-difference time-domain method with mesh sizes of 2 mm at 900 MHz plane wave irradiation. The power density of the incident plane wave is assumed to be 10 W/m(2). Computations were compared with a realistic anatomical head model. The results show that although there were marked differences in the local SAR distribution in the various tissues in the two models, the 1 g peak SAR values are approximately similar in the two models.
    Matched MeSH terms: Finite Element Analysis
  19. Optimal approach for complete liver tumor ablation using radiofrequency ablation: a simulation study
    Givehchi S, Wong YH, Yeong CH, Abdullah BJJ
    Minim Invasive Ther Allied Technol, 2018 Apr;27(2):81-89.
    PMID: 28612670 DOI: 10.1080/13645706.2017.1330757
    PURPOSE: To investigate the effect of radiofrequency ablation (RFA) electrode trajectory on complete tumor ablation using computational simulation.

    MATERIAL AND METHODS: The RFA of a spherical tumor of 2.0 cm diameter along with 0.5 cm clinical safety margin was simulated using Finite Element Analysis software. A total of 86 points inside one-eighth of the tumor volume along the axial, sagittal and coronal planes were selected as the target sites for electrode-tip placement. The angle of the electrode insertion in both craniocaudal and orbital planes ranged from -90° to +90° with 30° increment. The RFA electrode was simulated to pass through the target site at different angles in combination of both craniocaudal and orbital planes before being advanced to the edge of the tumor.

    RESULTS: Complete tumor ablation was observed whenever the electrode-tip penetrated through the epicenter of the tumor regardless of the angles of electrode insertion in both craniocaudal and orbital planes. Complete tumor ablation can also be achieved by placing the electrode-tip at several optimal sites and angles.

    CONCLUSIONS: Identification of the tumor epicenter on the central slice of the axial images is essential to enhance the success rate of complete tumor ablation during RFA procedures.

    Matched MeSH terms: Finite Element Analysis
  20. Fulltext Surface Acoustic Wave (SAW) Sensors for Hip Implant: A Numerical and Computational Feasibility Investigation Using Finite Element Methods
    Hafizh M, Soliman MM, Qiblawey Y, Chowdhury MEH, Islam MT, Musharavati F, et al.
    Biosensors (Basel), 2023 Jan 02;13(1).
    PMID: 36671914 DOI: 10.3390/bios13010079
    In this paper, a surface acoustic wave (SAW) sensor for hip implant geometry was proposed for the application of total hip replacement. A two-port SAW device was numerically investigated for implementation with an operating frequency of 872 MHz that can be used in more common radio frequency interrogator units. A finite element analysis of the device was developed for a lithium niobate (LiNBO3) substrate with a Rayleigh velocity of 3488 m/s on COMSOL Multiphysics. The Multiphysics loading and frequency results highlighted a good uniformity with numerical results. Afterwards, a hip implant geometry was developed. The SAW sensor was mounted at two locations on the implant corresponding to two regions along the shaft of the femur bone. Three discrete conditions were studied for the feasibility of the implant with upper- and lower-body loading. The loading simulations highlighted that the stresses experienced do not exceed the yield strengths. The voltage output results indicated that the SAW sensor can be implanted in the hip implant for hip implant-loosening detection applications.
    Matched MeSH terms: Finite Element Analysis
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