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Visualization of multiphase pulsatile blood over single phase blood flow in a patient specific stenosed left coronary artery using image processing technique

Athani A, Ghazali NNN, Anjum Badruddin I, Kamangar S, Salman Ahmed NJ, Honnutagi A

Biomed Mater Eng, 2023;34(1):13-35.
PMID: 36278331 DOI: 10.3233/BME-211333

BACKGROUND: Coronary arteries disease has been reported as one of the principal roots of deaths worldwide.
OBJECTIVE: The aim of this study is to analyze the multiphase pulsatile blood flow in the left coronary artery tree with stenosis.
METHODS: The 3D left coronary artery model was reconstructed using 2D computerized tomography (CT) scan images. The Red Blood Cell (RBC) and varying hemodynamic parameters for single and multiphase blood flow conditions were analyzed.
RESULTS: Results asserted that the multiphase blood flow modeling has a maximum velocity of 1.017 m/s and1.339 m/s at the stenosed region during the systolic and diastolic phases respectively. The increase in Wall Shear Stress (WSS) observed at the stenosed region during the diastole phase as compared during the systolic phase. It was also observed that the highest Oscillatory Shear Index (OSI) regions are found in the downstream area of stenosis and across the bifurcations. The increase in RBCs velocity from 0.45 m/s to 0.6 m/s across the stenosis was also noticed.
CONCLUSION: The computational multiphase blood flow analysis improves the understanding and accuracy of the complex flow conditions of blood elements (RBC and Plasma) and provides the progression of the disease development in the coronary arteries. This study helps to enhance the diagnosis of the blocked (stenosed) arteries more precisely compared to the single-phase blood flow modeling.

Matched MeSH terms: Stress, Mechanical
Fulltext Morphological study of the newly designed cementless femoral stem

Baharuddin MY, Salleh ShH, Zulkifly AH, Lee MH, Mohd Noor A

Biomed Res Int, 2014;2014:692328.
PMID: 25025068 DOI: 10.1155/2014/692328

A morphology study was essential to the development of the cementless femoral stem because accurate dimensions for both the periosteal and endosteal canal ensure primary fixation stability for the stem, bone interface, and prevent stress shielding at the calcar region. This paper focused on a three-dimensional femoral model for Asian patients that applied preoperative planning and femoral stem design. We measured various femoral parameters such as the femoral head offset, collodiaphyseal angle, bowing angle, anteversion, and medullary canal diameters from the osteotomy level to 150 mm below the osteotomy level to determine the position of the isthmus. Other indices and ratios for the endosteal canal, metaphyseal, and flares were computed and examined. The results showed that Asian femurs are smaller than Western femurs, except in the metaphyseal region. The canal flare index (CFI) was poorly correlated (r < 0.50) to the metaphyseal canal flare index (MCFI), but correlated well (r = 0.66) with the corticomedullary index (CMI). The diversity of the femoral size, particularly in the metaphyseal region, allows for proper femoral stem design for Asian patients, improves osseointegration, and prolongs the life of the implant.

Matched MeSH terms: Stress, Mechanical
Fulltext Biomechanical Stress in Obturator Prostheses: A Systematic Review of Finite Element Studies

Mousa MA, Abdullah JY, Jamayet NB, Alam MK, Husein A

Biomed Res Int, 2021;2021:6419774.
PMID: 34447852 DOI: 10.1155/2021/6419774

Aim: This systematic review is aimed at investigating the biomechanical stress that develops in the maxillofacial prostheses (MFP) and supporting structures and methods to optimize it. Design and Methods. A literature survey was conducted for full-text English articles which used FEA to examine the stress developed in conventional and implant-assisted MFPs from January 2010 to December 2020.
Results: 87 articles were screened to get an update on the desired information. 74 were excluded based on a complete screening, and finally, 13 articles were recruited for complete reviewing. Discussion. The MFP is subjected to stress, which is reflected in the form of compressive and tensile strengths. The stress is mainly concentrated the resection line and around the apices of roots of teeth next to the defect. Diversity of designs and techniques were introduced to optimize the stress distribution, such as modification of the clasp design, using materials with different mechanical properties for dentures base and retainer, use of dental (DI) and/or zygomatic implants (ZI), and free flap reconstruction before prosthetic rehabilitation.
Conclusion: Using ZI in the defective side of the dentulous maxillary defect and defective and nondefective side of the edentulous maxillary defect was found more advantageous, in terms of compression and tensile stress and retention, when compared with DI and free flap reconstruction.

Matched MeSH terms: Stress, Mechanical
Fulltext Numerical Solution of Blood Flow and Mass Transport in an Elastic Tube with Multiple Stenoses

Alsemiry RD, Sarifuddin, Mandal PK, Sayed HM, Amin N

Biomed Res Int, 2020;2020:7609562.
PMID: 32090110 DOI: 10.1155/2020/7609562

The simultaneous effect of flexible wall and multiple stenoses on the flow and mass transfer of blood is investigated through numerical computation and simulations. The solution is obtained using the Marker and Cell technique on an axisymmetric model of Newtonian blood flow. The results compare favorably with physical observations where the pulsatile boundary condition and double stenoses result in a higher pressure drop across the stenoses. The streamlines, the iso-concentration lines, the Sherwood number, and the mass concentration variations along the entire wall segment provide a comprehensive analysis of the mass transport characteristics. The double stenoses and pulsatile inlet conditions increase the number of recirculation regions and effect a higher mass transfer rate at the throat, whereby more mass is expected to accumulate and cause further stenosis.

Matched MeSH terms: Stress, Mechanical
The mechanisms of fibroblast-mediated compaction of collagen gels and the mechanical niche around individual fibroblasts

Feng Z, Wagatsuma Y, Kikuchi M, Kosawada T, Nakamura T, Sato D, et al.

Biomaterials, 2014 Sep;35(28):8078-91.
PMID: 24976242 DOI: 10.1016/j.biomaterials.2014.05.072

Fibroblast-mediated compaction of collagen gels attracts extensive attention in studies of wound healing, cellular fate processes, and regenerative medicine. However, the underlying mechanism and the cellular mechanical niche still remain obscure. This study examines the mechanical behaviour of collagen fibrils during the process of compaction from an alternative perspective on the primary mechanical interaction, providing a new viewpoint on the behaviour of populated fibroblasts. We classify the collagen fibrils into three types - bent, stretched, and adherent - and deduce the respective equations governing the mechanical behaviour of each type; in particular, from a putative principle based on the stationary state of the instantaneous Hamiltonian of the mechanotransduction system, we originally quantify the stretching force exerted on each stretched fibrils. Via careful verification of a structural elementary model based on this classification, we demonstrate a clear physical picture of the compaction process, quantitatively elucidate the panorama of the micro mechanical niche and reveal an intrinsic biphasic relationship between cellular traction force and matrix elasticity. Our results also infer the underlying mechanism of tensional homoeostasis and stress shielding of fibroblasts. With this study, and sequel investigations on the putative principle proposed herein, we anticipate a refocus of the research on cellular mechanobiology, in vitro and in vivo.

Matched MeSH terms: Stress, Mechanical
A fibril-based structural constitutive theory reveals the dominant role of network characteristics on the mechanical behavior of fibroblast-compacted collagen gels

Feng Z, Ishiguro Y, Fujita K, Kosawada T, Nakamura T, Sato D, et al.

Biomaterials, 2015 Oct;67:365-81.
PMID: 26247391 DOI: 10.1016/j.biomaterials.2015.07.038

In this paper, we present a general, fibril-based structural constitutive theory which accounts for three material aspects of crosslinked filamentous materials: the single fibrillar force response, the fibrillar network model, and the effects of alterations to the fibrillar network. In the case of the single fibrillar response, we develop a formula that covers the entropic and enthalpic deformation regions, and introduce the relaxation phase to explain the observed force decay after crosslink breakage. For the filamentous network model, we characterize the constituent element of the fibrillar network in terms its end-to-end distance vector and its contour length, then decompose the vector orientation into an isotropic random term and a specific alignment, paving the way for an expanded formalism from principal deformation to general 3D deformation; and, more important, we define a critical core quantity over which macroscale mechanical characteristics can be integrated: the ratio of the initial end-to-end distance to the contour length (and its probability function). For network alterations, we quantitatively treat changes in constituent elements and relate these changes to the alteration of network characteristics. Singular in its physical rigor and clarity, this constitutive theory can reproduce and predict a wide range of nonlinear mechanical behavior in materials composed of a crosslinked filamentous network, including: stress relaxation (with dual relaxation coefficients as typically observed in soft tissues); hysteresis with decreasing maximum stress under serial cyclic loading; strain-stiffening under uniaxial tension; the rupture point of the structure as a whole; various effects of biaxial tensile loading; strain-stiffening under simple shearing; the so-called "negative normal stress" phenomenon; and enthalpic elastic behaviors of the constituent element. Applied to compacted collagen gels, the theory demonstrates that collagen fibrils behave as enthalpic elasticas with linear elasticity within the gels, and that the macroscale nonlinearity of the gels originates from the curved fibrillar network. Meanwhile, the underlying factors that determine the mechanical properties of the gels are clarified. Finally, the implications of this study on the enhancement of the mechanical properties of compacted collagen gels and on the cellular mechanics with this model tissue are discussed.

Matched MeSH terms: Stress, Mechanical
Mechanical behaviour of in-situ chondrocytes subjected to different loading rates: a finite element study

Moo EK, Herzog W, Han SK, Abu Osman NA, Pingguan-Murphy B, Federico S

Biomech Model Mechanobiol, 2012 Sep;11(7):983-93.
PMID: 22234779 DOI: 10.1007/s10237-011-0367-2

Experimental findings indicate that in-situ chondrocytes die readily following impact loading, but remain essentially unaffected at low (non-impact) strain rates. This study was aimed at identifying possible causes for cell death in impact loading by quantifying chondrocyte mechanics when cartilage was subjected to a 5% nominal tissue strain at different strain rates. Multi-scale modelling techniques were used to simulate cartilage tissue and the corresponding chondrocytes residing in the tissue. Chondrocytes were modelled by accounting for the cell membrane, pericellular matrix and pericellular capsule. The results suggest that cell deformations, cell fluid pressures and fluid flow velocity through cells are highest at the highest (impact) strain rate, but they do not reach damaging levels. Tangential strain rates of the cell membrane were highest at the highest strain rate and were observed primarily in superficial tissue cells. Since cell death following impact loading occurs primarily in superficial zone cells, we speculate that cell death in impact loading is caused by the high tangential strain rates in the membrane of superficial zone cells causing membrane rupture and loss of cell content and integrity.

Matched MeSH terms: Stress, Mechanical
Fluid-structure interaction (FSI) modeling of bone marrow through trabecular bone structure under compression

Rabiatul AAR, Fatihhi SJ, Md Saad AP, Zakaria Z, Harun MN, Kadir MRA, et al.

Biomech Model Mechanobiol, 2021 Jun;20(3):957-968.
PMID: 33547975 DOI: 10.1007/s10237-021-01423-x

The present study has sought to investigate the fluid characteristic and mechanical properties of trabecular bone using fluid-structure interaction (FSI) approach under different trabecular bone orientations. This method imposed on trabecular bone structure at both longitudinal and transverse orientations to identify effects on shear stress, permeability, stiffness and stress regarded to the trabeculae. Sixteen FSI models were performed on different range trabecular cubes of 27 mm3 with eight models developed for each longitudinal and transverse direction. Results show that there was a moderate correlation between permeability and porosity, and surface area in the longitudinal and transverse orientations. For the longitudinal orientation, the permeability values varied between 3.66 × 10-8 and 1.9 × 10-7 and the sheer stress values varied between 0.05 and 1.8 Pa, whilst for the transverse orientation, the permeability values varied between 5.95 × 10-10 and 1.78 × 10-8 and the shear stress values varied between 0.04 and 3.1 Pa. Here, transverse orientation limits the fluid flow from passing through the trabeculae due to high shear stress disturbance generated within the trabecular bone region. Compared to physiological loading direction (longitudinal orientation), permeability is higher within the range known to trigger a response in bone cells. Additionally, shear stresses also increase with bone surface area. This study suggests the shear stress within bone marrow in real trabecular architecture could provide the mechanical signal to marrow cells that leads to bone anabolism and can depend on trabecular orientation.

Matched MeSH terms: Stress, Mechanical
Fulltext Prospects of implant with locking plate in fixation of subtrochanteric fracture: experimental demonstration of its potential benefits on synthetic femur model with supportive hierarchical nonlinear hyperelastic finite element analysis

Latifi MH, Ganthel K, Rukmanikanthan S, Mansor A, Kamarul T, Bilgen M

Biomed Eng Online, 2012;11:23.
PMID: 22545650 DOI: 10.1186/1475-925X-11-23

Effective fixation of fracture requires careful selection of a suitable implant to provide stability and durability. Implant with a feature of locking plate (LP) has been used widely for treating distal fractures in femur because of its favourable clinical outcome, but its potential in fixing proximal fractures in the subtrochancteric region has yet to be explored. Therefore, this comparative study was undertaken to demonstrate the merits of the LP implant in treating the subtrochancteric fracture by comparing its performance limits against those obtained with the more traditional implants; angle blade plate (ABP) and dynamic condylar screw plate (DCSP).

Matched MeSH terms: Stress, Mechanical
Fulltext Which is the best method of sterilization of tumour bone for reimplantation? A biomechanical and histopathological study

Singh VA, Nagalingam J, Saad M, Pailoor J

Biomed Eng Online, 2010;9:48.
PMID: 20831801 DOI: 10.1186/1475-925X-9-48

Sterilization and re-usage of tumour bone for reconstruction after tumour resection is now gaining popularity in the East. This recycle tumour bone needs to be sterilized in order to eradicate the tumour cells before re-implantation for limb salvage procedures. The effect of some of these treatments on the integrity and sterility of the bone after treatment has been published but there has yet been a direct comparison between the various methods of sterilization to determine the one method that gives the best tumour kill without compromising the bone's structural integrity.

Matched MeSH terms: Stress, Mechanical
Compression and tension behavior of the prosthetic foam materials polyurethane, EVA, Pelite™ and a combination of polyurethane and EVA: a preliminary study

Lutfi SNN, Abd Razak NA, Ali S, Gholizadeh H

Biomed Tech (Berl), 2021 Jun 25;66(3):317-322.
PMID: 34062632 DOI: 10.1515/bmt-2019-0110

Materials with low-strength and low-impedance properties, such as elastomers and polymeric foams are major contributors to prosthetic liner design. Polyethylene-Light (Pelite™) is a foam liner that is the most frequently used in prosthetics but it does not cater to all amputees' limb and skin conditions. The study aims to investigate the newly modified Foam Liner, a combination of two different types of foams (EVA + PU + EVA) as the newly modified Foam Liner in terms of compressive and tensile properties in comparison to Pelite™, polyurethane (PU) foam, and ethylene-vinyl acetate (EVA) foam. Universal testing machine (AGS-X, Shimadzu, Kyoto, Japan) has been used to measure the tensile and compressive stress. Pelite™ had the highest compressive stress at 566.63 kPa and tensile stress at 1145 kPa. Foam Liner fell between EVA and Pelite™ with 551.83 kPa at compression and 715.40 kPa at tension. PU foam had the lowest compressive stress at 2.80 kPa and tensile stress at 33.93 kPa. Foam Liner has intermediate compressive elasticity but has high tensile elasticity compared to EVA and Pelite™. Pelite™ remains the highest in compressive and tensile stiffness. Although it is good for amputees with bony prominence, constant pressure might result in skin breakdown or ulcer. Foam Liner would be the best for amputees with soft tissues on the residual limbs to accommodate movement.

Matched MeSH terms: Stress, Mechanical
Fulltext The properties of chondrocyte membrane reservoirs and their role in impact-induced cell death

Moo EK, Amrein M, Epstein M, Duvall M, Abu Osman NA, Pingguan-Murphy B, et al.

Biophys J, 2013 Oct 1;105(7):1590-600.
PMID: 24094400 DOI: 10.1016/j.bpj.2013.08.035

Impact loading of articular cartilage causes extensive chondrocyte death. Cell membranes have a limited elastic range of 3-4% strain but are protected from direct stretch during physiological loading by their membrane reservoir, an intricate pattern of membrane folds. Using a finite-element model, we suggested previously that access to the membrane reservoir is strain-rate-dependent and that during impact loading, the accessible membrane reservoir is drastically decreased, so that strains applied to chondrocytes are directly transferred to cell membranes, which fail when strains exceed 3-4%. However, experimental support for this proposal is lacking. The purpose of this study was to measure the accessible membrane reservoir size for different membrane strain rates using membrane tethering techniques with atomic force microscopy. We conducted atomic force spectroscopy on isolated chondrocytes (n = 87). A micron-sized cantilever was used to extract membrane tethers from cell surfaces at constant pulling rates. Membrane tethers could be identified as force plateaus in the resulting force-displacement curves. Six pulling rates were tested (1, 5, 10, 20, 40, and 80 μm/s). The size of the membrane reservoir, represented by the membrane tether surface areas, decreased exponentially with increasing pulling rates. The current results support our theoretical findings that chondrocytes exposed to impact loading die because of membrane ruptures caused by high tensile membrane strain rates.

Matched MeSH terms: Stress, Mechanical*
The formation and characterisation of an asymmetric nanofiltration membrane for ammonia-nitrogen removal: effect of shear rate

Ali N, Halim NS, Jusoh A, Endut A

Bioresour Technol, 2010 Mar;101(5):1459-65.
PMID: 19786347 DOI: 10.1016/j.biortech.2009.08.070

The focus of this research is to study the potential of nanofiltration membrane technology in removing ammonia-nitrogen from the aquaculture system. One of the major fabrication parameters that directly affect the separation performance is shear rate or casting rate during membrane fabrication. In this study, asymmetric polyethersulfone (PES) nanofiltration membranes were prepared at five different shear rates within the range of 67-400 s(-1). Membrane productivity and separation performance were assessed via pure water, salt and ammonia-nitrogen permeation experiments, and their structural properties were determined by employing the combination of the irreversible thermodynamic (IT) model, solution diffusion model, steric hindrance pore (SHP) model and Teorell-Meyers (TMS) model. The study reveals that the alteration of shear rate enormously affects the membrane morphology and structural parameters, hence subsequently significantly influencing the membrane performance. It was found that, membrane produced at the shear rate 200 s(-1) or equivalent to 10s of casting speed during membrane fabrications managed to remove about 68% of ammonia-nitrogen, in which its separation performance is the most favourable by means of highest flux and rejection ability towards unwanted solutes. Besides, from the research findings, nano-membrane technology is a potential candidate for the treatment of aquaculture wastewater.

Matched MeSH terms: Stress, Mechanical*
Development of a novel liquid crystal based cell traction force transducer system

Soon CF, Youseffi M, Berends RF, Blagden N, Denyer MC

Biosens Bioelectron, 2013 Jan 15;39(1):14-20.
PMID: 22809522 DOI: 10.1016/j.bios.2012.06.032

Keratinocyte traction forces play a crucial role in wound healing. The aim of this study was to develop a novel cell traction force (CTF) transducer system based on cholesteryl ester liquid crystals (LC). Keratinocytes cultured on LC induced linear and isolated deformation lines in the LC surface. As suggested by the fluorescence staining, the deformation lines appeared to correlate with the forces generated by the contraction of circumferential actin filaments which were transmitted to the LC surface via the focal adhesions. Due to the linear viscoelastic behavior of the LC, Hooke's equation was used to quantify the CTFs by associating Young's modulus of LC to the cell induced stresses and biaxial strain in forming the LC deformation. Young's modulus of the LC was profiled by using spherical indentation and determined at approximately 87.1±17.2kPa. A new technique involving cytochalasin-B treatment was used to disrupt the intracellular force generating actin fibers, and consequently the biaxial strain in the LC induced by the cells was determined. Due to the improved sensitivity and spatial resolution (∼1μm) of the LC based CTF transducer, a wide range of CTFs was determined (10-120nN). These were found to be linearly proportional to the length of the deformations. The linear relationship of CTF-deformations was then applied in a bespoke CTF mapping software to estimate CTFs and to map CTF fields. The generated CTF map highlighted distinct distributions and different magnitude of CTFs were revealed for polarized and non-polarized keratinocytes.

Matched MeSH terms: Stress, Mechanical
Mechanistic investigation of phytochemicals involved in green synthesis of gold nanoparticles using aqueous Elaeis guineensis leaves extract: Role of phenolic compounds and flavonoids

Ahmad T, Bustam MA, Irfan M, Moniruzzaman M, Asghar HMA, Bhattacharjee S

Biotechnol Appl Biochem, 2019 Jul;66(4):698-708.
PMID: 31172593 DOI: 10.1002/bab.1787

Phytosynthesis of gold nanoparticles (AuNPs) has achieved an indispensable significance due to the diverse roles played by biomolecules in directing the physiochemical characteristics of biosynthesized nanoparticles. Therefore, the precise identification of key bioactive compounds involved in producing AuNPs is vital to control their tunable characteristics for potential applications. Herein, qualitative and quantitative determination of key biocompounds contributing to the formation of AuNPs using aqueous Elaeis guineensis leaves extract is reported. Moreover, roles of phenolic compounds and flavonoids in reduction of Au3+ and stabilization of AuNPs have been elucidated by establishing a reaction mechanism. Fourier-transform infrared spectroscopy (FTIR) showed shifting of O─H stretching vibrations toward longer wavenumbers and C═O toward shorter wavenumbers due to involvement of polyphenolic compounds in biosynthesis and oxidation of polyphenolic into carboxylic compounds, respectively, which cape nanoparticles to inhibit the aggregation. Congruently, pyrolysis-gas chromatography-mass spectrometry revealed the major contribution of polyphenolic compounds in the synthesis of AuNPs, which was further endorsed by reduction of total phenolic and total flavonoids contents from 48.08 ± 1.98 to 9.59 ± 0.92 mg GAE/g and 32.02 ± 1.31 to 13.8 ± 0.97 mg CE/g within 60 Min, respectively. Based on experimental results, reaction mechanism explained the roles of phenolic compounds and flavonoids in producing spherical-shaped AuNPs.

Matched MeSH terms: Stress, Mechanical
Synthesis of kenaf cellulose carbamate and its smart electric stimuli-response

Gan S, Piao SH, Choi HJ, Zakaria S, Chia CH

Carbohydr Polym, 2016 Feb 10;137:693-700.
PMID: 26686181 DOI: 10.1016/j.carbpol.2015.11.035

Cellulose carbamate (CC) was produced from kenaf core pulp (KCP) via a microwave reactor-assisted method. The formation of CC was confirmed by Fourier transform infrared spectroscopy and nitrogen content analysis. The degree of substitution, zeta potential and size distribution of CC were also determined. The CC was characterized with scanning electron microscopy, X-ray diffraction and thermogravimetry analysis. The CC particles were then dispersed in silicone oil to prepare CC-based anhydrous electric stimuli-responsive electrorheological (ER) fluids. Rhelogical measurement was carried out using rotational rheometer with a high voltage generator in both steady and oscillatory shear modes to examine the effect of electric field strength on the ER characteristics. The results showed that the increase in electric field strength has enhanced the ER properties of CC-based ER fluid due to the chain formation induced by electric polarization among the particles.

Matched MeSH terms: Stress, Mechanical
Transtibial prosthetic socket pistoning: static evaluation of Seal-In(®) X5 and Dermo(®) Liner using motion analysis system

Gholizadeh H, Osman NA, Kamyab M, Eshraghi A, Abas WA, Azam MN

Clin Biomech (Bristol, Avon), 2012 Jan;27(1):34-9.
PMID: 21794965 DOI: 10.1016/j.clinbiomech.2011.07.004

The method of attachment of prosthesis to the residual limb (suspension) and socket fitting is a critical issue in the process of providing an amputee with prosthesis. Different suspension methods try to minimize the pistoning movement inside the socket. The Seal-In(®) X5 and Dermo(®) Liner by Ossur are new suspension liners that intend to reduce pistoning between the socket and liner. Since the effects of these new liners on suspension are unclear, the objective of this study was to compare the pistoning effect of Seal-In(®) X5 and Dermo(®) Liner by using Vicon Motion System.

Matched MeSH terms: Stress, Mechanical
Mechanical compression controls the biosynthesis of human osteoarthritic chondrocytes in vitro

Chong PP, Panjavarnam P, Ahmad WNHW, Chan CK, Abbas AA, Merican AM, et al.

Clin Biomech (Bristol, Avon), 2020 10;79:105178.
PMID: 32988676 DOI: 10.1016/j.clinbiomech.2020.105178

BACKGROUND: Cartilage damage, which can potentially lead to osteoarthritis, is a leading cause of morbidity in the elderly population. Chondrocytes are sensitive to mechanical stimuli and their matrix-protein synthesis may be altered when chondrocytes experience a variety of in vivo loadings. Therefore, a study was conducted to evaluate the biosynthesis of isolated osteoarthritic chondrocytes which subjected to compression with varying dynamic compressive strains and loading durations.
METHODS: The proximal tibia was resected as a single osteochondral unit during total knee replacement from patients (N = 10). The osteoarthritic chondrocytes were isolated from the osteochondral units, and characterized using reverse transcriptase-polymerase chain reaction. The isolated osteoarthritic chondrocytes were cultured and embedded in agarose, and then subjected to 10% and 20% uniaxial dynamic compression up to 8-days using a bioreactor. The morphological features and changes in the osteoarthritic chondrocytes upon compression were evaluated using scanning electron microscopy. Safranin O was used to detect the presence of cartilage matrix proteoglycan expression while quantitative analysis was conducted by measuring type VI collagen using an immunohistochemistry and fluorescence intensity assay.
FINDINGS: Gene expression analysis indicated that the isolated osteoarthritic chondrocytes expressed chondrocyte-specific markers, including BGN, CD90 and HSPG-2. Moreover, the compressed osteoarthritic chondrocytes showed a more intense and broader deposition of proteoglycan and type VI collagen than control. The expression of type VI collagen was directly proportional to the duration of compression in which 8-days compression was significantly higher than 4-days compression. The 20% compression showed significantly higher intensity compared to 10% compression in 4- and 8-days.
INTERPRETATION: The biosynthetic activity of human chondrocytes from osteoarthritic joints can be enhanced using selected compression regimes.

Matched MeSH terms: Stress, Mechanical
Fulltext Deep-Freezing Temperatures During Irradiation Preserves the Compressive Strength of Human Cortical Bone Allografts: A Cadaver Study

Yang Harmony TC, Yusof N, Ramalingam S, Baharin R, Syahrom A, Mansor A

Clin Orthop Relat Res, 2022 Feb 01;480(2):407-418.
PMID: 34491235 DOI: 10.1097/CORR.0000000000001968

BACKGROUND: Gamma irradiation, which minimizes the risk of infectious disease transmission when human bone allograft is used, has been found to negatively affect its biomechanical properties. However, in those studies, the deep-freezing temperature during irradiation was not necessarily maintained during transportation and sterilization, which may have affected the findings. Prior reports have also suggested that controlled deep freezing may mitigate the detrimental effects of irradiation on the mechanical properties of bone allograft.
QUESTION/PURPOSE: Does a controlled deep-freezing temperature during irradiation help preserve the compressive mechanical properties of human femoral cortical bone allografts?
METHODS: Cortical bone cube samples, each measuring 64 mm3, were cut from the mid-diaphyseal midshaft of five fresh-frozen cadaver femurs (four male donors, mean [range] age at procurement 42 years [42 to 43]) and were allocated via block randomization into one of three experimental groups (with equal numbers of samples from each donor allocated into each group). Each experimental group consisted of 20 bone cube samples. Samples irradiated in dry ice were subjected to irradiation doses ranging from 26.7 kGy to 27.1 kGy (mean 26.9 kGy) at a deep-freezing temperature below -40°C (the recommended long-term storage temperature for allografts). Samples irradiated in gel ice underwent irradiation doses ranging from 26.2 kGy and 26.4 kGy (mean 26.3 kGy) in a freezing temperature range between -40°C and 0°C. Acting as controls, samples in a third group were not subjected to gamma irradiation. The mechanical properties (0.2% offset yield stress, ultimate compression stress, toughness, and the Young modulus) of samples from each group were subsequently evaluated via axial compression loading to failure along the long axis of the bone. The investigators were blinded to sample group during compression testing.
RESULTS: The mean ultimate compression stress (84 ± 27 MPa versus 119 ± 31 MPa, mean difference 35 [95% CI 9 to 60]; p = 0.005) and toughness (3622 ± 1720 kJ/m3 versus 5854 ± 2900 kJ/m3, mean difference 2232 [95% CI 70 to 4394]; p = 0.009) of samples irradiated at a higher temperature range (-40°C to 0°C) were lower than in those irradiated at deep-freezing temperatures (below -40°C). The mean 0.2% offset yield stress (73 ± 28 MPa versus 109 ± 38 MPa, mean difference 36 [95% CI 11 to 60]; p = 0.002) and ultimate compression stress (84 ± 27 MPa versus 128 ± 40 MPa, mean difference 44 [95% CI 17 to 69]; p < 0.001) of samples irradiated at a higher temperature range (-40°C to 0°C) were lower than the nonirradiated control group samples. The mean 0.2% offset yield stress (73 ± 28 MPa versus 101 ± 28 MPa, mean difference 28 [95% CI 3 to 52]; p = 0.02; effect size = 1.0 [95% CI 0.8 to 1.2]) of samples irradiated at higher temperature range (-40°C to 0°C) were no different with the numbers available to those irradiated at deep-freezing temperature. The mean toughness (3622 ± 1720 kJ/m3 versus 6231 ± 3410 kJ/m3, mean difference 2609 [95% CI 447 to 4771]; p = 0.02; effect size = 1.0 [95% CI 0.8 to 1.2]) of samples irradiated at higher temperature range (-40°C to 0°C) were no different with the numbers available to the non-irradiated control group samples. The mean 0.2% offset yield stress, ultimate compression stress, and toughness of samples irradiated in deep-freezing temperatures (below -40°C) were not different with the numbers available to the non-irradiated control group samples. The Young modulus was not different with the numbers available among the three groups.
CONCLUSION: In this study, maintenance of a deep-freezing temperature below -40°C, using dry ice as a cooling agent, consistently mitigated the adverse effects of irradiation on the monotonic-compression mechanical properties of human cortical bone tissue. Preserving the mechanical properties of a cortical allograft, when irradiated in a deep-freezing temperature, may have resulted from attenuation of the deleterious, indirect effects of gamma radiation on its collagen architecture in a frozen state. Immobilization of water molecules in this state prevents radiolysis and the subsequent generation of free radicals. This hypothesis was supported by an apparent loss of the protective effect when a range of higher freezing temperatures was used during irradiation.
CLINICAL RELEVANCE: Deep-freezing temperatures below -40°C during gamma irradiation may be a promising approach to better retain the native mechanical properties of cortical bone allografts. A further study of the effect of deep-freezing during gamma radiation sterilization on sterility and other important biomechanical properties of cortical bone (such as, tensile strength, fracture toughness, and fatigue) is needed to confirm these findings.

Matched MeSH terms: Stress, Mechanical
Fulltext Preliminary analysis of knee stress in full extension landing

Makinejad MD, Abu Osman NA, Abu Bakar Wan Abas W, Bayat M

Clinics (Sao Paulo), 2013 Sep;68(9):1180-8.
PMID: 24141832 DOI: 10.6061/clinics/2013(09)02

This study provides an experimental and finite element analysis of knee-joint structure during extended-knee landing based on the extracted impact force, and it numerically identifies the contact pressure, stress distribution and possibility of bone-to-bone contact when a subject lands from a safe height.

Matched MeSH terms: Stress, Mechanical

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