| 1. |
- Bahaloo, Hassan, 1983-, et al.
(författare)
-
On the failure initiation in the proximal human femur under simulated sideways fall
- 2018
-
Ingår i: Annals of Biomedical Engineering. - : Springer. - 0090-6964 .- 1573-9686. ; 46, s. 270-283
-
Tidskriftsartikel (refereegranskat)abstract
- The limitations of areal bone mineral density measurements for identifying at-risk individuals have led to the development of alternative screening methods for hip fracture risk including the use of geometrical measurements from the proximal femur and subject specific finite element analysis (FEA) for predicting femoral strength, based on quantitative CT data (qCT). However, these methods need more development to gain widespread clinical applications. This study had three aims: To investigate whether proximal femur geometrical parameters correlate with obtained femur peak force during the impact testing; to examine whether or not failure of the proximal femur initiates in the cancellous (trabecular) bone; and finally, to examine whether or not surface fracture initiates in the places where holes perforate the cortex of the proximal femur. We found that cortical thickness around the trochanteric-fossa is significantly correlated to the peak force obtained from simulated sideways falling (R 2 = 0.69) more so than femoral neck cortical thickness (R 2 = 0.15). Dynamic macro level FE simulations predicted that fracture generally initiates in the cancellous bone compartments. Moreover, our micro level FEA results indicated that surface holes may be involved in primary failure events.
|
|
| 2. |
- Bergström, Joakim, et al.
(författare)
-
An Overview of Mechanical Properties and Material Modeling of Polylactide (PLA) for Medical Applications
- 2016
-
Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 44:2, s. 330-340
-
Tidskriftsartikel (refereegranskat)abstract
- This article provides an overview of the connection between the microstructural state and the mechanical response of various bioresorbable polylactide (PLA) devices for medical applications. PLLA is currently the most commonly used material for bioresorbable stents and sutures, and its use is increasing in many other medical applications. The non-linear mechanical response of PLLA, due in part to its low glass transition temperature (T g ≈ 60 °C), is highly sensitive to the molecular weight and molecular orientation field, the degree of crystallinity, and the physical aging time. These microstructural parameters can be tailored for specific applications using different resin formulations and processing conditions. The stress-strain, deformation, and degradation response of a bioresorbable medical device is also strongly dependent on the time history of applied loads and boundary conditions. All of these factors can be incorporated into a suitable constitutive model that captures the multiple physics that are involved in the device response. Currently developed constitutive models already provide powerful computations simulation tools, and more progress in this area is expected to occur in the coming years.
|
|
| 3. |
- Hellström, Mats, 1976, et al.
(författare)
-
Uterine Tissue Engineering and the Future of Uterus Transplantation.
- 2017
-
Ingår i: Annals of biomedical engineering. - : Springer Science and Business Media LLC. - 1573-9686 .- 0090-6964. ; 45:7, s. 1718-1730
-
Tidskriftsartikel (refereegranskat)abstract
- The recent successful births following live donor uterus transplantation are proof-of-concept that absolute uterine factor infertility is a treatable condition which affects several hundred thousand infertile women world-wide due to a dysfunctional uterus. This strategy also provides an alternative to gestational surrogate motherhood which is not practiced in most countries due to ethical, religious or legal reasons. The live donor surgery involved in uterus transplantation takes more than 10h and is then followed by years of immunosuppressive medication to prevent uterine rejection. Immunosuppression is associated with significant adverse side effects, including nephrotoxicity, increased risk of serious infections, and diabetes. Thus, the development of alternative approaches to treat absolute uterine factor infertility would be desirable. This review discusses tissue engineering principles in general, but also details strategies on how to create a bioengineered uterus that could be used for transplantation, without risky donor surgery and any need for immunosuppression. We discuss scaffolds derived from decellularized organs/tissues which may be recellularized using various types of autologous somatic/stem cells, in particular for uterine tissue engineering. It further highlights the hurdles that lay ahead in developing an alternative to an allogeneic source for uterus transplantation.
|
|
| 4. |
|
|
| 5. |
- Hernandez, Fidel, et al.
(författare)
-
Six Degree-of-Freedom Measurements of Human Mild Traumatic Brain Injury
- 2015
-
Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 43:8, s. 1918-1934
-
Tidskriftsartikel (refereegranskat)abstract
- This preliminary study investigated whether direct measurement of head rotation improves prediction of mild traumatic brain injury (mTBI). Although many studies have implicated rotation as a primary cause of mTBI, regulatory safety standards use 3 degree-of-freedom (3DOF) translation-only kinematic criteria to predict injury. Direct 6DOF measurements of human head rotation (3DOF) and translation (3DOF) have not been previously available to examine whether additional DOFs improve injury prediction. We measured head impacts in American football, boxing, and mixed martial arts using 6DOF instrumented mouthguards, and predicted clinician-diagnosed injury using 12 existing kinematic criteria and 6 existing brain finite element (FE) criteria. Among 513 measured impacts were the first two 6DOF measurements of clinically diagnosed mTBI. For this dataset, 6DOF criteria were the most predictive of injury, more than 3DOF translation-only and 3DOF rotation-only criteria. Peak principal strain in the corpus callosum, a 6DOF FE criteria, was the strongest predictor, followed by two criteria that included rotation measurements, peak rotational acceleration magnitude and Head Impact Power (HIP). These results suggest head rotation measurements may improve injury prediction. However, more 6DOF data is needed to confirm this evaluation of existing injury criteria, and to develop new criteria that considers directional sensitivity to injury.
|
|
| 6. |
- Honkanen, Juuso, et al.
(författare)
-
Cationic contrast agent diffusion differs between cartilage and meniscus
- 2016
-
Ingår i: Annals of Biomedical Engineering. - : Springer. - 0090-6964 .- 1573-9686. ; 44:10, s. 2913-2921
-
Tidskriftsartikel (refereegranskat)abstract
- Contrast enhanced computed tomography (CECT) is a non-destructive imaging technique used for the assessment of composition and structure of articular cartilage and meniscus. Due to structural and compositional differences between these tissues, diffusion and distribution of contrast agents may differ in cartilage and meniscus. The aim of this study is to determine the diffusion kinematics of a novel iodine based cationic contrast agent (CA(2+)) in cartilage and meniscus. Cylindrical cartilage and meniscus samples (d = 6 mm, h ≈ 2 mm) were harvested from healthy bovine knee joints (n = 10), immersed in isotonic cationic contrast agent (20 mgI/mL), and imaged using a micro-CT scanner at 26 time points up to 48 h. Subsequently, normalized X-ray attenuation and contrast agent diffusion flux, as well as water, collagen and proteoglycan (PG) contents in the tissues were determined. The contrast agent distributions within cartilage and meniscus were different. In addition, the normalized attenuation and diffusion flux were higher (p < 0.05) in cartilage. Based on these results, diffusion kinematics vary between cartilage and meniscus. These tissue specific variations can affect the interpretation of CECT images and should be considered when cartilage and meniscus are assessed simultaneously.
|
|
| 7. |
- Lantz, Jonas, 1982-, et al.
(författare)
-
Impact of Pulmonary Venous Inflow on Cardiac Flow Simulations : Comparison with In Vivo 4D Flow MRI
- 2019
-
Ingår i: Annals of Biomedical Engineering. - : Springer-Verlag New York. - 0090-6964 .- 1573-9686. ; 47:2, s. 413-424
-
Tidskriftsartikel (refereegranskat)abstract
- Blood flow simulations are making their way into the clinic, and much attention is given to estimation of fractional flow reserve in coronary arteries. Intracardiac blood flow simulations also show promising results, and here the flow field is expected to depend on the pulmonary venous (PV) flow rates. In the absence of in vivo measurements, the distribution of the flow from the individual PVs is often unknown and typically assumed. Here, we performed intracardiac blood flow simulations based on time-resolved computed tomography on three patients, and investigated the effect of the distribution of PV flow rate on the flow field in the left atrium and ventricle. A design-of-experiment approach was used, where PV flow rates were varied in a systematic manner. In total 20 different simulations were performed per patient, and compared to in vivo 4D flow MRI measurements. Results were quantified by kinetic energy, mitral valve velocity profiles and root-mean-square errors of velocity. While large differences in atrial flow were found for varying PV inflow distributions, the effect on ventricular flow was negligible, due to a regularizing effect by mitral valve. Equal flow rate through all PVs most closely resembled in vivo measurements and is recommended in the absence of a priori knowledge.
|
|
| 8. |
- Müller, Michael, et al.
(författare)
-
Alginate Sulfate–Nanocellulose Bioinks for Cartilage Bioprinting Applications
- 2017
-
Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 1573-9686 .- 0090-6964. ; 45:1, s. 210-223
-
Tidskriftsartikel (refereegranskat)abstract
- One of the challenges of bioprinting is to identify bioinks which support cell growth, tissue maturation, and ultimately the formation of functional grafts for use in regenerative medicine. The influence of this new biofabrication technology on biology of living cells, however, is still being evaluated. Recently we have identified a mitogenic hydrogel system based on alginate sulfate which potently supports chondrocyte phenotype, but is not printable due to its rheological properties (no yield point). To convert alginate sulfate to a printable bioink, it was combined with nanocellulose, which has been shown to possess very good printability. The alginate sulfate/nanocellulose ink showed good printing properties and the non-printed bioink material promoted cell spreading, proliferation, and collagen II synthesis by the encapsulated cells. When the bioink was printed, the biological performance of the cells was highly dependent on the nozzle geometry. Cell spreading properties were maintained with the lowest extrusion pressure and shear stress. However, extruding the alginate sulfate/nanocellulose bioink and chondrocytes significantly compromised cell proliferation, particularly when using small diameter nozzles and valves. © 2016, Biomedical Engineering Society.
|
|
| 9. |
|
|
| 10. |
- Riveros, Fabian, et al.
(författare)
-
On the Impact of Intraluminal Thrombus Mechanical Behavior in AAA Passive Mechanics
- 2015
-
Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 43:9, s. 2253-2264
-
Tidskriftsartikel (refereegranskat)abstract
- Intraluminal thrombus (ILT) is a pseudo-tissue that develops from coagulated blood, and is found in most abdominal aortic aneurysms (AAAs) of clinically relevant size. A number of studies have suggested that ILT mechanical characteristics may be related to AAA risk of rupture, even though there is still great controversy in this regard. ILT is isotropic and inhomogeneous and may appear as a soft (single-layered) or stiff (multilayered fibrotic) tissue. This paper aims to investigate how ILT constitution and topology influence the magnitude and location of peak wall stress (PWS). In total 21 patient-specific AAAs (diameter 4.2-5.4 cm) were reconstructed from computer tomography images and biomechanically analyzed using state-of-the-art modeling assumptions. Results indicated that PWS correlated stronger with ILT volume (rho = 0.44, p = 0.05) and minimum thickness of ILT layer (rho = 0.73, p = 0.001) than with maximum AAA diameter (rho = 0.05, p = 0.82). On average PWS was 20% (SD 12%) higher for FE models that used soft instead of stiff ILT models (p < 0.001). PWS location strongly correlated with sites of minimum ILT thickness in the section of maximum AAA diameter and was independent from ILT stiffness. In addition, ILT heterogeneity, i.e., the spatial composition of soft and stiff thrombus tissue, can considerably influence stress in the AAA wall. The present study is limited to identification of influential biomechanical factors, and how its findings translate to an AAA rupture risk assessment remains to be explored by clinical studies.
|
|
| 11. |
- Stenlund, Patrik, et al.
(författare)
-
Loads on Transhumeral Amputees Using Osseointegrated Prostheses
- 2019
-
Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 47:6, s. 1369-1377
-
Tidskriftsartikel (refereegranskat)abstract
- The treatment of the upper extremities is not as prevalent as that of the lower limbs, but it is nonetheless equally important. Today, there are no load data relating to upper extremity bone-anchored prosthesis users in the literature, but they are important in order to improve the rehabilitation protocol, design aspects and confidence of the user when it comes to loading the prosthesis in daily life. The aim of the present study was to investigate, in a population of eleven transhumeral amputees with osseointegrated implants, the load levels reached during specific prosthetic movements at maximum voluntary effort and during daily activities. The data showed a wide range of maximum load levels throughout the different activities. Furthermore, the data indicate that some test subjects felt apprehensive about loading the prosthesis, resulting in relatively low loads compared with the group as a whole. Within the limits of the present study, it was concluded that loading the implant system was subject specific, which resulted in large subject-to-subject variability. Moreover, some subjects exhibited uncertainty about the levels that could damage the fixation or the implant system. The study illustrates the diversity and uncertainty that exist in a population of transhumeral amputees treated with bone-anchored prostheses in terms of loading in daily life.
|
|
| 12. |
- Thesleff, Alexander, 1986, et al.
(författare)
-
Biomechanical Characterisation of Bone-anchored Implant Systems for Amputation Limb Prostheses: A Systematic Review
- 2018
-
Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 46:3, s. 377-391
-
Tidskriftsartikel (refereegranskat)abstract
- Bone-anchored limb prostheses allow for the direct transfer of external loads from the prosthesis to the skeleton, eliminating the need for a socket and the associated problems of poor fit, discomfort, and limited range of movement. A percutaneous implant system for direct skeletal attachment of an external limb must provide a long-term, mechanically stable interface to the bone, along with an infection barrier to the external environment. In addition, the mechanical integrity of the implant system and bone must be preserved despite constant stresses induced by the limb prosthesis. Three different percutaneous implant systems for direct skeletal attachment of external limb prostheses are currently clinically available and a few others are under investigation in human subjects. These systems employ different strategies and have undergone design changes with a view to fulfilling the aforementioned requirements. This review summarises such strategies and design changes, providing an overview of the biomechanical characteristics of current percutaneous implant systems for direct skeletal attachment of amputation limb prostheses.
|
|
| 13. |
- Valero, C., et al.
(författare)
-
Challenges in the Modeling of Wound Healing Mechanisms in Soft Biological Tissues
- 2015
-
Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 1573-9686 .- 0090-6964. ; 43:7, s. 1654-1665
-
Tidskriftsartikel (refereegranskat)abstract
- Numerical models have become one of the most powerful tools in biomechanics and mechanobiology allowing highly detailed simulations. One of the fields in which they have broadly evolved during the last years is in soft tissue modeling. Particularly, wound healing in the skin is one of the processes that has been approached by computational models due to the difficulty of performing experimental investigations. During the last decades wound healing simulations have evolved from numerical models which considered only a few number of variables and simple geometries to more complex approximations that take into account a higher number of factors and reproduce more realistic geometries. Moreover, thanks to improved experimental observations, a larger number of processes, such as cellular stress generation or vascular growth, that take place during wound healing have been identified and modeled. This work presents a review of the most relevant wound healing approximations, together with an identification of the most relevant criteria that can be used to classify them. In addition, and looking towards the actual state of the art in the field, some future directions, challenges and improvements are analyzed for future developments.
|
|
| 14. |
- Vuong, Vicky, et al.
(författare)
-
Surface and Subsurface Analyses of Metal-on-Polyethylene Total Hip Replacement Retrievals
- 2016
-
Ingår i: Annals of Biomedical Engineering. - : Springer Nature. - 0090-6964 .- 1573-9686. ; 44:5, s. 1685-1697
-
Tidskriftsartikel (refereegranskat)abstract
- Metal-on-polyethylene (MoP) articulations are one of the most reliable implanted hip prostheses. Unfortunately, long-term failure remains an obstacle to the service life. There is a lack of higher resolution research investigating the metallic surface component of MoP hip implants. This study investigates the surface and subsurface features of metallic cobalt chromium molybdenum alloy (CoCrMo) femoral head components from failed MoP retrievals. Unused prostheses were used for comparison to differentiate between wear-induced defects and imperfections incurred during implant manufacturing. The predominant scratch morphology observed on the non-implanted references was shallow and linear, whereas the scratches on the retrievals consisted of largely nonlinear, irregular scratches of varying depth (up to 150 nm in retrievals and up to 60 nm in reference samples). Characteristic hard phases were observed on the surface and subsurface material of the cast samples. Across all samples, a 100-400 nm thick nanocrystalline layer was visible in the immediate subsurface microstructure. Although observation of the nanocrystalline layer has been reported in metal-on-metal articulations, its presence in MoP retrievals and unimplanted prostheses has not been extensively examined. The results suggest that manufacturing-induced surface and subsurface microstructural features are present in MoP hip prostheses prior to implantation and naturally, these imperfections may influence the in vivo wear processes after implantation.
|
|
| 15. |
- Frosth, Sara, et al.
(författare)
-
Sample pooling for real-time PCR detection and virulence determination of the footrot pathogen Dichelobacter nodosus
- 2017
-
Ingår i: Veterinary Research Communications. - : Springer Science and Business Media LLC. - 0165-7380 .- 1573-7446. ; 41, s. 189-193
-
Tidskriftsartikel (refereegranskat)abstract
- Dichelobacter nodosus is the principal cause of ovine footrot and strain virulence is an important factor in disease severity. Therefore, detection and virulence determination of D. nodosus is important for proper diagnosis of the disease. Today this is possible by real-time PCR analysis. Analysis of large numbers of samples is costly and laborious; therefore, pooling of individual samples is common in surveillance programs. However, pooling can reduce the sensitivity of the method. The aim of this study was to develop a pooling method for real-time PCR analysis that would allow sensitive detection and simultaneous virulence determination of D. nodosus. A total of 225 sheep from 17 flocks were sampled using ESwabs within the Swedish Footrot Control Program in 2014. Samples were first analysed individually and then in pools of five by real-time PCR assays targeting the 16S rRNA and aprV2/B2 genes of D. nodosus. Each pool consisted of four negative and one positive D. nodosus samples with varying amounts of the bacterium. In the individual analysis, 61 (27.1%) samples were positive in the 16S rRNA and the aprV2/B2 PCR assays and 164 (72.9%) samples were negative. All samples positive in the aprV2/B2 PCR-assay were of aprB2 variant. The pooled analysis showed that all 41 pools were also positive for D. nodosus 16S rRNA and the aprB2 variant. The diagnostic sensitivity for pooled and individual samples was therefore similar. Our method includes concentration of the bacteria before DNA-extraction. This may account for the maintenance of diagnostic sensitivity. Diagnostic sensitivity in the real-time PCR assays of the pooled samples were comparable to the sensitivity obtained for individually analysed samples. Even sub-clinical infections were able to be detected in the pooled PCR samples which is important for control of the disease. This method may therefore be implemented in footrot control programs where it can replace analysis of individual samples.
|
|
| 16. |
|
|
| 17. |
- Attorps, Iiris, et al.
(författare)
-
School-University Action Research : Impacts on Teaching Practices and Pupil Learning
- 2017
-
Ingår i: International Journal of Science and Mathematics Education. - : Springer Science and Business Media LLC. - 1571-0068 .- 1573-1774. ; 15:2, s. 313-330
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this article is to describe a design and implementation of a school-university action research project about teaching and learning biology and mathematics in primary school. Nine teachers in grades 1 to 6, in collaboration with two researchers, were using content representation (CoRe) in learning study (LS)-inspired cycle as pedagogical tools when planning, implementing, and reflecting on lessons and pupil learning. By using pre- and post-tests, the teachers acquired knowledge about pupil subject-specific knowledge and learning. Some examples are given on how the tools in the project influenced the teaching practices and pupil learning. This research design brought together university and school practitioners to work collaboratively in a professional learning community, which developed teaching and learning in biology and mathematics.
|
|
