Helmets have evolved through improvements in shell and suspension materials, and better designs that can absorb ballistic and blunt impact energy. In the past 20 years, threats to US Warfighters have increased with the prevalence of buried improvised explosive devices (IED) simultaneous producing overpressure, blunt and ballistic impact effects, as well as thermal loading in extreme desert conditions. To date, no research has been found in literature that integrates multiple types of loading in helmet system design and performance analysis. The scope of this paper is to integrate such loadings into a design framework that enables trade space analysis across multiple threats. Blunt impact and blast overpressure loadings are simulated using computational fluid dynamics and structural mechanics approaches presented by the authors earlier. The thermal loading and its effects are modeled as buoyancy-driven natural convection, i.e., flow generated by the body’s thermal plume, and forced convection due to ambient wind to assess each design’s efficiency in facilitating evaporative cooling via perspiration and quantified by transport of moisture-laden air away from the head. Blast overpressure and blunt impact loadings, along with thermal loading, are used for multiple configurations of the helmet suspension system as representative cases. The results from the simulated cases are integrated within a framework combining the effects of the loadings to assess helmet system design. We hope that this paper suggests ways to generate a functional representation integrating multiple loadings in protection system design.
{"title":"On a Framework to Integrate Performance of Helmet Systems for Blast, Blunt Impact and Thermal Loading","authors":"A. Bagchi, Y. Khine, D. Mott, X. Tan","doi":"10.1115/imece2021-73556","DOIUrl":"https://doi.org/10.1115/imece2021-73556","url":null,"abstract":"\u0000 Helmets have evolved through improvements in shell and suspension materials, and better designs that can absorb ballistic and blunt impact energy. In the past 20 years, threats to US Warfighters have increased with the prevalence of buried improvised explosive devices (IED) simultaneous producing overpressure, blunt and ballistic impact effects, as well as thermal loading in extreme desert conditions. To date, no research has been found in literature that integrates multiple types of loading in helmet system design and performance analysis. The scope of this paper is to integrate such loadings into a design framework that enables trade space analysis across multiple threats. Blunt impact and blast overpressure loadings are simulated using computational fluid dynamics and structural mechanics approaches presented by the authors earlier. The thermal loading and its effects are modeled as buoyancy-driven natural convection, i.e., flow generated by the body’s thermal plume, and forced convection due to ambient wind to assess each design’s efficiency in facilitating evaporative cooling via perspiration and quantified by transport of moisture-laden air away from the head. Blast overpressure and blunt impact loadings, along with thermal loading, are used for multiple configurations of the helmet suspension system as representative cases. The results from the simulated cases are integrated within a framework combining the effects of the loadings to assess helmet system design. We hope that this paper suggests ways to generate a functional representation integrating multiple loadings in protection system design.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124881209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ethan Rabb, R. Zifchock, Margaret Nowicki, Jeremy D. Paquin, M. Posner
The purpose of this project is to design a device that provides skeletal traction to a patient with a fractured femur in an aeromedical evacuation environment. Skeletal traction is typically provided by using weights and cable to provide tension onto a fractured limb. However, in an aeromedical evacuation environment, the forces vary and the environment is not stable, so the traditional method to provide skeletal traction is not suitable. Therefore, we designed and tested a device that could provide skeletal traction to a femoral fracture in an aeromedical evacuation environment.
{"title":"Aeromedical Evacuation Skeletal Traction","authors":"Ethan Rabb, R. Zifchock, Margaret Nowicki, Jeremy D. Paquin, M. Posner","doi":"10.1115/imece2021-70540","DOIUrl":"https://doi.org/10.1115/imece2021-70540","url":null,"abstract":"\u0000 The purpose of this project is to design a device that provides skeletal traction to a patient with a fractured femur in an aeromedical evacuation environment. Skeletal traction is typically provided by using weights and cable to provide tension onto a fractured limb. However, in an aeromedical evacuation environment, the forces vary and the environment is not stable, so the traditional method to provide skeletal traction is not suitable. Therefore, we designed and tested a device that could provide skeletal traction to a femoral fracture in an aeromedical evacuation environment.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124116147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eric Near, Mustafa Ihsan, Waylon Chan, V. Viswanathan
COVID-19 is an infectious disease that has dramatically affected the world, causing a pandemic and changing many aspects of people’s lives and how they interact. The condition is highly contagious and aims at a person’s respiratory system. A ventilator, a medical device that helps patients breathe when they are unable to do it independently, is needed because COVID-19 inflames the airways in the lungs, making it difficult to breathe normally. Ventilators are not the cure for COVID-19 but are a piece of equipment to help people breathe until that body function can be done independently. Such equipment can be expensive to acquire and cumbersome to operate. The Spartan Ventilator uses off-the-shelf equipment, economic controls, and robust techniques to supply a patient’s lungs with oxygen. The system is designed for oxygen tanks that are commonly found within hospitals. However, a mechanical pump will be used as a substitute. All processes are controlled and monitored by an LCD touchscreen attached to an Arduino. The user interface is presented with simple buttons and menus to maximize screen space, provide quick readings of pressure, and control breaths per minute (BPM). PVC pipes, a cheap and durable material suitable for the non-volatile transportation of gas, were used. The valves we use are not definitive; they can be replaced with any 12V valve. The significant differences with the Spartan Ventilator are the price and the simplicity that the new technology has. The Spartan Ventilator can be very cheap compared to other professional ventilators that can be found in hospitals. The ventilator can be ten times less expensive than different professional ventilators while having the same efficiency and power.
{"title":"Design and Testing of a Low-Cost Ventilator to Battle the Global Pandemic","authors":"Eric Near, Mustafa Ihsan, Waylon Chan, V. Viswanathan","doi":"10.1115/imece2021-70897","DOIUrl":"https://doi.org/10.1115/imece2021-70897","url":null,"abstract":"\u0000 COVID-19 is an infectious disease that has dramatically affected the world, causing a pandemic and changing many aspects of people’s lives and how they interact. The condition is highly contagious and aims at a person’s respiratory system. A ventilator, a medical device that helps patients breathe when they are unable to do it independently, is needed because COVID-19 inflames the airways in the lungs, making it difficult to breathe normally. Ventilators are not the cure for COVID-19 but are a piece of equipment to help people breathe until that body function can be done independently. Such equipment can be expensive to acquire and cumbersome to operate. The Spartan Ventilator uses off-the-shelf equipment, economic controls, and robust techniques to supply a patient’s lungs with oxygen. The system is designed for oxygen tanks that are commonly found within hospitals. However, a mechanical pump will be used as a substitute. All processes are controlled and monitored by an LCD touchscreen attached to an Arduino. The user interface is presented with simple buttons and menus to maximize screen space, provide quick readings of pressure, and control breaths per minute (BPM). PVC pipes, a cheap and durable material suitable for the non-volatile transportation of gas, were used. The valves we use are not definitive; they can be replaced with any 12V valve. The significant differences with the Spartan Ventilator are the price and the simplicity that the new technology has. The Spartan Ventilator can be very cheap compared to other professional ventilators that can be found in hospitals. The ventilator can be ten times less expensive than different professional ventilators while having the same efficiency and power.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126559981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Carvalho, F. Carneiro, A. Ferreira, V. Gama, S. Teixeira, J. Teixeira
The characterization of blood flow patterns is an important task to establish links between hemodynamics and atherosclerosis development, one of the leading causes of death worldwide. Taking into account that the development of cardiovascular diseases and the disturbances in blood flow profiles are characteristic of each individual, the study of the effects of geometry and flow distribution is quite important. For this reason, in the present paper, a CFD numerical model for both simplified and real anatomic iliac bifurcation was developed, taking into account a steady velocity inlet profile. The results were analyzed, in terms of the recirculation zone length and location, but also in velocity and wall shear stress distribution. It was observed that the bifurcation angle does not affect significantly the recirculation properties. However, significant differences were achieved with different iliac diameters and bifurcation geometry. Moreover, outflow maldistribution in the iliac arteries leads to more complex flow patterns near the iliac bifurcation, intensifying reverse and asymmetric flow patterns. The results of the simulation using the realistic model geometry confirmed that the regions of the geometry prone to develop recirculation areas occur, preferentially, downstream the bifurcation at the outer walls of iliac branches. In brief, this study allowed a better understanding of the relationship between hemodynamics and vascular diseases, through assessing the distributions of blood velocity and biomechanical forces imposed on the arterial wall by the blood.
{"title":"Steady Flow Studies of the Geometry Effects on the Recirculation Properties at the Iliac Bifurcation","authors":"V. Carvalho, F. Carneiro, A. Ferreira, V. Gama, S. Teixeira, J. Teixeira","doi":"10.1115/imece2021-73450","DOIUrl":"https://doi.org/10.1115/imece2021-73450","url":null,"abstract":"\u0000 The characterization of blood flow patterns is an important task to establish links between hemodynamics and atherosclerosis development, one of the leading causes of death worldwide. Taking into account that the development of cardiovascular diseases and the disturbances in blood flow profiles are characteristic of each individual, the study of the effects of geometry and flow distribution is quite important. For this reason, in the present paper, a CFD numerical model for both simplified and real anatomic iliac bifurcation was developed, taking into account a steady velocity inlet profile.\u0000 The results were analyzed, in terms of the recirculation zone length and location, but also in velocity and wall shear stress distribution. It was observed that the bifurcation angle does not affect significantly the recirculation properties. However, significant differences were achieved with different iliac diameters and bifurcation geometry. Moreover, outflow maldistribution in the iliac arteries leads to more complex flow patterns near the iliac bifurcation, intensifying reverse and asymmetric flow patterns. The results of the simulation using the realistic model geometry confirmed that the regions of the geometry prone to develop recirculation areas occur, preferentially, downstream the bifurcation at the outer walls of iliac branches.\u0000 In brief, this study allowed a better understanding of the relationship between hemodynamics and vascular diseases, through assessing the distributions of blood velocity and biomechanical forces imposed on the arterial wall by the blood.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128022363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gregory R. Roytman, Matthew Budavich, Judith D. Pocius, Jocelyn Faydenko, Dana Muligano, G. Cramer
The vibration and acoustic emissions produced within facet joints of the lumbar spine, known as crepitus, can be a potential biomarker to identify decreased joint functioning and the site of low back pain. Using piezoelectric accelerometers and a silicone “phantom” mechanical model we sought to identify the site of crepitus. Past analyses of these data with human observers have been too time consuming for eventual practical clinical application, and a more expedient algorithmic method of analysis is preferable. In this study the signal filtering and processing functions of MATLAB were harnessed to filter aberrant noise as well as determine the location (level and left or right side) from which crepitus originated during induced crepitus events in the phantom model (n = 30). Development of this automated method refined the definition of facet joint crepitus. The automated method was found to be as reliable and valid as assessment by human observers, and took significantly less time (p = 0.009). Future studies will assess the reliability of the automated method to detect this phenomenon in humans.
{"title":"Vibration and Acoustic Crepitus Sensing Using Piezoelectric Accelerometers and Automated Signal Analysis","authors":"Gregory R. Roytman, Matthew Budavich, Judith D. Pocius, Jocelyn Faydenko, Dana Muligano, G. Cramer","doi":"10.1115/imece2021-67348","DOIUrl":"https://doi.org/10.1115/imece2021-67348","url":null,"abstract":"\u0000 The vibration and acoustic emissions produced within facet joints of the lumbar spine, known as crepitus, can be a potential biomarker to identify decreased joint functioning and the site of low back pain. Using piezoelectric accelerometers and a silicone “phantom” mechanical model we sought to identify the site of crepitus. Past analyses of these data with human observers have been too time consuming for eventual practical clinical application, and a more expedient algorithmic method of analysis is preferable. In this study the signal filtering and processing functions of MATLAB were harnessed to filter aberrant noise as well as determine the location (level and left or right side) from which crepitus originated during induced crepitus events in the phantom model (n = 30). Development of this automated method refined the definition of facet joint crepitus. The automated method was found to be as reliable and valid as assessment by human observers, and took significantly less time (p = 0.009). Future studies will assess the reliability of the automated method to detect this phenomenon in humans.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132605036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The permanent implantation of stents with and without carrying drugs led to the unresolvable long-term complications such as restenosis and thrombosis. There are increasing interests in bioresorbable stents, which have the potential to resume the vessel tone and mitigate complications. The bioresorbable stent served as a temporary scaffold for an expected period of 6 to 12 months. The design of both polymeric material and stent structure is acknowledged to impact the mechanical integrity of bioresorbable stent. Poly-l-lactide (PLLA), a polymer-based material, is the most adopted bioresorbable stent materials due to its sufficient strength and degradation resistance. The mechanical performances of the PLLA stents need to be evaluated before it is considered to serve in the clinical application. Because of difficulty and time-consuming of physical tests, finite element method (FEM) has become an efficient way to solve the problem. However, the mechanical performances of PLLA stents during the degradation process could not be fully captured using the existing numerical models. A strain-based degradation numerical model with consideration of stent-artery interaction was proposed based on the previous published experimental data. In this model, the elongation fracture of the PLLA material was correlated to the degradation degree, a scalar factor controlled by the time and local strain. The degradation evolution process was then fully captured after the stent implantation using the derived material model. With continuously loss of mass in material, the degradation rates were not uniform in different locations along the stent structure. Severe degradation was observed at the higher strain regions of the stent, which locates at the outer surface of the stent, near the crowns of the ring stent strut. At first stage of degradation, the stent strut thinning was observed in the model which was also found in the previous experimental study. At second stage of degradation, the degradation happened at the connection region between the link strut and ring struts which resulted in the break of mechanical integrity. The diameter of the vessel has minor change during the first stage of the degradation process, while at the second stage, with the breakdown of the ring structure, the vessel recoiled to its original diameter in one month time. The two-staged degradation process showed a vision for the ideal stent design. The developed computational model provided more insights into the degradation process, which could complement the discrete experimental data for improving the design and clinical management of the bioresorbable vascular scaffold.
{"title":"Strain-Based Degradation Model With Application to Poly-L-Lactide Acid (PLLA) Artery Stent","authors":"Shengmao Lin, Pengfei Dong, L. Gu","doi":"10.1115/imece2021-72395","DOIUrl":"https://doi.org/10.1115/imece2021-72395","url":null,"abstract":"\u0000 The permanent implantation of stents with and without carrying drugs led to the unresolvable long-term complications such as restenosis and thrombosis. There are increasing interests in bioresorbable stents, which have the potential to resume the vessel tone and mitigate complications. The bioresorbable stent served as a temporary scaffold for an expected period of 6 to 12 months. The design of both polymeric material and stent structure is acknowledged to impact the mechanical integrity of bioresorbable stent. Poly-l-lactide (PLLA), a polymer-based material, is the most adopted bioresorbable stent materials due to its sufficient strength and degradation resistance. The mechanical performances of the PLLA stents need to be evaluated before it is considered to serve in the clinical application. Because of difficulty and time-consuming of physical tests, finite element method (FEM) has become an efficient way to solve the problem. However, the mechanical performances of PLLA stents during the degradation process could not be fully captured using the existing numerical models. A strain-based degradation numerical model with consideration of stent-artery interaction was proposed based on the previous published experimental data. In this model, the elongation fracture of the PLLA material was correlated to the degradation degree, a scalar factor controlled by the time and local strain. The degradation evolution process was then fully captured after the stent implantation using the derived material model. With continuously loss of mass in material, the degradation rates were not uniform in different locations along the stent structure. Severe degradation was observed at the higher strain regions of the stent, which locates at the outer surface of the stent, near the crowns of the ring stent strut. At first stage of degradation, the stent strut thinning was observed in the model which was also found in the previous experimental study. At second stage of degradation, the degradation happened at the connection region between the link strut and ring struts which resulted in the break of mechanical integrity. The diameter of the vessel has minor change during the first stage of the degradation process, while at the second stage, with the breakdown of the ring structure, the vessel recoiled to its original diameter in one month time. The two-staged degradation process showed a vision for the ideal stent design. The developed computational model provided more insights into the degradation process, which could complement the discrete experimental data for improving the design and clinical management of the bioresorbable vascular scaffold.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132759262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dan Huynh, J. J. Steckenrider, Gregory M Freisinger
This paper presents an original technique for estimating human posture metrics using Novel Loadsols®. Under the proposed technique, center of pressure (COP) metrics are derived by combining physics- and data-driven estimates to achieve reasonably high accuracy at relatively low cost. To develop a training set upon which the probabilistic data model was constructed, 79 trials were conducted in which participants stood comfortably still for 30 seconds at a time simultaneously on a force plate and a pair of Loadsols, where the force plate is considered to be the gold-standard of COP measurement. These data were then used to generate Gaussian mixture models (GMMs) of pairwise combinations of force plate and Loadsol metrics. The GMMs can then be conditioned on Loadsol measurements and fused using Bayesian inference. When the training set was re-processed by converting 12 Loadsol metrics into estimated force plate metrics, it was found that the converted metrics matched ground-truth more accurately on average than raw Loadsol metrics. Furthermore, there was improvement in the r2 values of the regression lines after conversion for 75% of the metrics. Given some experiment and algorithm refinement, the proposed probabilistic approach has potential to offer the accuracy of force plate COP estimation at a fraction of the cost.
{"title":"Probabilistic Estimation of Posture Metrics Using Novel Loadsols","authors":"Dan Huynh, J. J. Steckenrider, Gregory M Freisinger","doi":"10.1115/imece2021-69409","DOIUrl":"https://doi.org/10.1115/imece2021-69409","url":null,"abstract":"\u0000 This paper presents an original technique for estimating human posture metrics using Novel Loadsols®. Under the proposed technique, center of pressure (COP) metrics are derived by combining physics- and data-driven estimates to achieve reasonably high accuracy at relatively low cost. To develop a training set upon which the probabilistic data model was constructed, 79 trials were conducted in which participants stood comfortably still for 30 seconds at a time simultaneously on a force plate and a pair of Loadsols, where the force plate is considered to be the gold-standard of COP measurement. These data were then used to generate Gaussian mixture models (GMMs) of pairwise combinations of force plate and Loadsol metrics. The GMMs can then be conditioned on Loadsol measurements and fused using Bayesian inference. When the training set was re-processed by converting 12 Loadsol metrics into estimated force plate metrics, it was found that the converted metrics matched ground-truth more accurately on average than raw Loadsol metrics. Furthermore, there was improvement in the r2 values of the regression lines after conversion for 75% of the metrics. Given some experiment and algorithm refinement, the proposed probabilistic approach has potential to offer the accuracy of force plate COP estimation at a fraction of the cost.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124535186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shear forces at sitting interfaces are a major contributing factor in pressure injury formation. However, measuring shear forces throughout the sitting interface is not possible due to a lack of shear sensors for this application. This paper presents a finite element simulation model for an automated air cell smart seat cushion that can predict shear forces at the interface. The model was developed and validated by comparing static analyses to experimental data, with respect to interface pressure, internal air cell pressure, and interaction forces. The real-time experimental data in this study was generated from three different sources: 1) A commercial seating pressure mat yields an interface pressure map, 2) The smart seat cushion yields the internal pressure of air cells, and 3) The rigid cushion loading indenter yields the immersion into the cushion and the force applied on the cushion. The validated simulation model was used to evaluate shear force data at the sitting interface corresponding to different loading scenarios.
{"title":"Numerical Modeling of Air Cell Cushion and Estimation of Shear Force Distribution at Sitting Interface","authors":"Veysel Erel, Pavan Nuthi, Yixin Gu, Himanshu Purandare, Nischita Haldipurkar, M. Wijesundara","doi":"10.1115/imece2021-71765","DOIUrl":"https://doi.org/10.1115/imece2021-71765","url":null,"abstract":"\u0000 Shear forces at sitting interfaces are a major contributing factor in pressure injury formation. However, measuring shear forces throughout the sitting interface is not possible due to a lack of shear sensors for this application. This paper presents a finite element simulation model for an automated air cell smart seat cushion that can predict shear forces at the interface. The model was developed and validated by comparing static analyses to experimental data, with respect to interface pressure, internal air cell pressure, and interaction forces. The real-time experimental data in this study was generated from three different sources: 1) A commercial seating pressure mat yields an interface pressure map, 2) The smart seat cushion yields the internal pressure of air cells, and 3) The rigid cushion loading indenter yields the immersion into the cushion and the force applied on the cushion. The validated simulation model was used to evaluate shear force data at the sitting interface corresponding to different loading scenarios.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122095142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Khandaker, S. Nikfarjam, Karim Kari, O. Kalay, F. Karpat, H. Progri, A. Bhuiyan, Erik Clary, A. Haleem
Aseptic loosening is a well-recognized phenomenon in cementless total knee replacement (TKR) and often carries severe consequences for the patient. We recently developed and tested in vitro a novel strategy for enhancing osseointegration and acute mechanical stability of orthopedic implants that employ laser-induced microgroove (LIM) and nanofiber membrane (NFM) applications at the bone-implant interface. We report herein investigation of the approach with results from a pilot study employing three skeletally mature female Spanish cross goats (∼4y, 35–45kg) receiving cementless TKR with a commercially available implant system (Biomedrix® Canine Total Knee). Pre-operative radiographs were taken to ensure limb normality and to select the appropriately sized implants for each goat. With the animal under general anesthesia and the limb properly prepped for aseptic surgery, the stifle was approached, and osteotomies of the proximal tibia and distal femur performed in preparation for implantation of the tibial (TT) and femoral (FT) trays. For one goat, the arthroplasty implant surfaces were unaltered from the manufacturer’s mirror-polished (MP) condition. For the other two goats, the TT bone-contact surface was laser-micro grooved (150 μm depth, 200 μm width, 200 μm spacing) prior to sterilization and then implanted with (LIM/NFM) or without (LIM) an intermediate (surface-applied) polycaprolactone (PCL) nanofiber mesh (50 × 50mm, electrospun, aligned, unidirectional, 10 μm thickness). Following surgery, animals received appropriate analgesic therapy and rehabilitative care to maximize animal comfort, function, and quality of life while limiting the risk of major complications. Post-operative monitoring included assessment of mentation, vital signs, pain level, digestive function (weight, appetite, rumen contractions, feed intake, fecal output), and limb status (usage, range of motion, muscular volume). By the study’s end (12 wks), all animals had recovered a pre-surgery range of motion in the operated knee and exhibited typical bony changes on radiographic follow-up. At necropsy following humane euthanasia, no gross instability of TKR components was observed. Histomorphometric analysis of explanted bone-TT constructs showed the increased new bone surface area in the LIM-NFM sample (0.49 mm2) compared with the MP sample (0.03 mm2), suggesting that microgrooves and/or PCL nanofiber coating may improve the clinical performance of the implant. A finite element analysis (FEA) model was developed to explore the impact of surface micro grooving to the mechanical stimuli at the bone-implant interface to supplement the in vivo studies. The three-dimensional geometry of the tibia was scanned using computed tomography and imported into a proprietary (MIMICS®) software to construct the solid models for finite element micro-strain analyses.
{"title":"Laser Microgrooving and Nanofiber Membrane Application for Total Knee Replacement Implants Using a Caprine Model","authors":"M. Khandaker, S. Nikfarjam, Karim Kari, O. Kalay, F. Karpat, H. Progri, A. Bhuiyan, Erik Clary, A. Haleem","doi":"10.1115/imece2021-73597","DOIUrl":"https://doi.org/10.1115/imece2021-73597","url":null,"abstract":"\u0000 Aseptic loosening is a well-recognized phenomenon in cementless total knee replacement (TKR) and often carries severe consequences for the patient. We recently developed and tested in vitro a novel strategy for enhancing osseointegration and acute mechanical stability of orthopedic implants that employ laser-induced microgroove (LIM) and nanofiber membrane (NFM) applications at the bone-implant interface. We report herein investigation of the approach with results from a pilot study employing three skeletally mature female Spanish cross goats (∼4y, 35–45kg) receiving cementless TKR with a commercially available implant system (Biomedrix® Canine Total Knee). Pre-operative radiographs were taken to ensure limb normality and to select the appropriately sized implants for each goat. With the animal under general anesthesia and the limb properly prepped for aseptic surgery, the stifle was approached, and osteotomies of the proximal tibia and distal femur performed in preparation for implantation of the tibial (TT) and femoral (FT) trays. For one goat, the arthroplasty implant surfaces were unaltered from the manufacturer’s mirror-polished (MP) condition. For the other two goats, the TT bone-contact surface was laser-micro grooved (150 μm depth, 200 μm width, 200 μm spacing) prior to sterilization and then implanted with (LIM/NFM) or without (LIM) an intermediate (surface-applied) polycaprolactone (PCL) nanofiber mesh (50 × 50mm, electrospun, aligned, unidirectional, 10 μm thickness). Following surgery, animals received appropriate analgesic therapy and rehabilitative care to maximize animal comfort, function, and quality of life while limiting the risk of major complications. Post-operative monitoring included assessment of mentation, vital signs, pain level, digestive function (weight, appetite, rumen contractions, feed intake, fecal output), and limb status (usage, range of motion, muscular volume). By the study’s end (12 wks), all animals had recovered a pre-surgery range of motion in the operated knee and exhibited typical bony changes on radiographic follow-up. At necropsy following humane euthanasia, no gross instability of TKR components was observed. Histomorphometric analysis of explanted bone-TT constructs showed the increased new bone surface area in the LIM-NFM sample (0.49 mm2) compared with the MP sample (0.03 mm2), suggesting that microgrooves and/or PCL nanofiber coating may improve the clinical performance of the implant. A finite element analysis (FEA) model was developed to explore the impact of surface micro grooving to the mechanical stimuli at the bone-implant interface to supplement the in vivo studies. The three-dimensional geometry of the tibia was scanned using computed tomography and imported into a proprietary (MIMICS®) software to construct the solid models for finite element micro-strain analyses.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126471221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohit Agarwal, P. Pasupathy, R. De Simone, A. Pelegri
Numerical simulations using non-linear hyper-elastic material models to describe interactions between brain white matter (axons and extra cellular matrix (ECM)) have enabled high-fidelity characterization of stress-strain response. In this paper, a novel finite element model (FEM) has been developed to study mechanical response of axons embedded in ECM when subjected to tensile loads under purely non-affine kinematic boundary conditions. FEM leveraging Ogden hyper-elastic material model is deployed to understand impact of parametrically varying oligodendrocyte-axon tethering and analyze influence of aging material characteristics on stress propagation. In proposed FEM, oligodendrocyte connections to axons are represented via spring-dashpot model, such tethering technique facilitates contact definition at various locations, parameterize connection points and vary stiffness of connection hubs. Two FE submodels are discussed: 1) multiple oligodendrocytes arbitrarily tethered to the nearest axons, and 2) single oligodendrocyte tethered to all axons at various locations. Root mean square deviation (RMSD) were computed between stress-strain plots to depict trends in mechanical response. Axonal stiffness was found to rise with increasing tethering, indicating role of oligodendrocytes in stress redistribution. Finally, stress state results for aging axon material, with varying stiffnesses and number of connections in FEM ensemble have also been discussed to demonstrate gradual softening of tissues.
{"title":"Oligodendrocyte Tethering Effect on Hyperelastic 3D Response of Injured Axons in Brain White Matter","authors":"Mohit Agarwal, P. Pasupathy, R. De Simone, A. Pelegri","doi":"10.1115/imece2021-73376","DOIUrl":"https://doi.org/10.1115/imece2021-73376","url":null,"abstract":"\u0000 Numerical simulations using non-linear hyper-elastic material models to describe interactions between brain white matter (axons and extra cellular matrix (ECM)) have enabled high-fidelity characterization of stress-strain response. In this paper, a novel finite element model (FEM) has been developed to study mechanical response of axons embedded in ECM when subjected to tensile loads under purely non-affine kinematic boundary conditions. FEM leveraging Ogden hyper-elastic material model is deployed to understand impact of parametrically varying oligodendrocyte-axon tethering and analyze influence of aging material characteristics on stress propagation. In proposed FEM, oligodendrocyte connections to axons are represented via spring-dashpot model, such tethering technique facilitates contact definition at various locations, parameterize connection points and vary stiffness of connection hubs. Two FE submodels are discussed: 1) multiple oligodendrocytes arbitrarily tethered to the nearest axons, and 2) single oligodendrocyte tethered to all axons at various locations. Root mean square deviation (RMSD) were computed between stress-strain plots to depict trends in mechanical response. Axonal stiffness was found to rise with increasing tethering, indicating role of oligodendrocytes in stress redistribution. Finally, stress state results for aging axon material, with varying stiffnesses and number of connections in FEM ensemble have also been discussed to demonstrate gradual softening of tissues.","PeriodicalId":314012,"journal":{"name":"Volume 5: Biomedical and Biotechnology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116759082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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