An alternative method of conventional prosthesis is  osseointegrated transfemoral implant, in where the prosthesis is fixated directly to the bone. The benefits with this system is increased range of motion, sensory feedback and reduced soft tissue problem. One of the drawbacks of this method is the effect of stress shielding, which could in long term lead to bone loss and bone resorption. The aim of this study is to investigate how the length of the fixture (60, 80 and 100 mm) of OPRA system (Osseointegrated Prosthesis for the Rehabilitation of Amputees) affects the stress distribution in femoral bone and implant during short walk by using Finite Element Methods.  The finite element model used in this study was constructed of three major parts: THUMS model (Total Human Model of Safety) of left thigh, implant and bone graft. The analysis was performed through the software LS-DYNA, with an implicit solver. The loading of the total gait cycle was applied in the distal end of the implant, whereas the proximal end of the thigh was fixed.  The FE simulation revealed lower stress distribution in the distal end of femoral bone, and higher in the proximal end. Implant 60 had lowest effect of stress shielding. The highest stress distribution in OPRA implant was shown in the abutment shaft, in the interface with bone graft. The length of the fixture did not have any impact on the stress distribution in the implant.

The primary aim of this study was to fill a gap in the literature in understanding maximal BH in untrained, non-divers by generating a predictive numerical model for PAO2 and PACO2 throughout BH. There have been little to no previous attempts at explicitly characterizing the influence of impermanent personal or environmental factors on PAO2 or PACO2 at BH breakpoint. The metabolic human consumption of O2 and production of CO2 as measured through alveolar partial pressures was observed over time during a voluntary maximum breath-hold for 18 members of the general population. The coefficient of determination was used to determine accuracy of the model in fitting participants’ BH data from this experiment. The volume of the last inhalation pre-BH, time to subjective breakpoint, and breath-to-breath calculated respiratory exchange ratio (RER) were identified as the most influential combination of key variables that improved PAO2 model fit (from R2 = 0.8591 to R2 = 0.8840). Clustering methods coupled with two sample t-tests or ANOVA were then used to identify survey responses most correlated to inter-BH similarities. These were barometric pressure, age, height, weight, resting HR, smoker/ freediver/scuba experience, and weekly frequency of engaging in physical exercise. The model was validated on testing data from an experienced free-diver, from non-rebreathing trials of a sample of the participants, and from simulated dives of 5 participants from research in the Environmental Physiology Department of Karolinska in 1994 [1]. It has been suggested that the presented model can be a valuable tool in developing safer free diving practices. Furthermore, interesting trends in continuous HR, starting PACO2 values, and O2 consumption were observed and analyzed using statistical analysis. Findings were discussed with connection to the underlying physiological principles that might explain the results obtained.

Powered exoskeletons can assist patients suffering from motor dysfunctions. Recent researches are focused on how to improve the communication system between patient and device. Further research is needed in order to design an EMG based robotic assistive device able to convey intended motions to the patient. The primary need is the understanding of how EMG patterns from different muscles contribute to motions. Studies on muscle synergy have shown how different muscles of lower limbs contribute to gait. This study is aimed to expand the analysis to motions other than gait by analysing ten muscles around the right knee joint. The chosen muscle were soleus, gastrocnemius medialis, gastrocnemius lateralis, peroneus longus, tibialis anterior, rectus femoris, vastus medialis, vastus lateralis, biceps femoris and semitendinosus. The main hypothesis is that specific movements are controlled by specific muscle synergies. Motion data and EMG data of eight healthy subjects have been compared in order to outline a coordination pattern specific to four different movements: gait, gait stop and balance, sit to stand and stand to sit. Through the analysis of EMG signals, three muscle synergies have been identified including muscles from the same group, i.e. four plantar flexors, three quadriceps and two hamstrings. It was possible to conclude that the four movements were controlled by the same muscle synergies with different coordination patterns. Further research is recommended to expand the knowledge about muscle synergies.

For various reasons it might be required to scan an object that partially lies outside the field of view(FOV) of a CT scanner. The parts of the object that lie outside the FOV will not contribute to the line integrals measured by the detector which will cause image artifacts that affect the final image quality. In this paper, I suggest a novel reconstruction approach that estimates the attenuation by the object outside the FOV using a priori knowledge about the outline of the object. It is shown that, knowing the object’s outline, it is possible to determine whether the attenuation along a given line is truncated. The total attenuation for a truncated projection is then estimated by interpolating the data between the consistent projections. The method therefore requires some of the projections to be consistent. This estimate, along with the knowledge of the distance traversed by the X-Ray inside the object is then used to determine the average attenuation. The method was tested on both numerical and physical phantoms. The results are satisfactory even when up to 80% of the projections are truncated. Structural Similarity Index (SSIM) was compared for the complete reconstructed images,and regions of truncations before and after the algorithm was applied. Reconstructed images from completely consistent projections served as ground truth. The results indicate that the algorithm can be used to reconstruct partially truncated CT data, which was tested on numerical and physical phantoms (of semicircular cross section). There is scope for further testing of the algorithm on irregularly shaped objects. / Technology

Mechanical stress exerted on long bones stimulate ossification and it has been shown that the mechanical variable frequency promotes osteogenesis. This ex-vivo study aimed to investigate how compressive and cyclic loading frequency impacts longitudinal growth of long bones. Three separate experiments were performed utilizing fetal Sprague-Dawley rat bones as experimental model. In the first two trials metatarsals where used while tibias were tested in the third trial. The bones were loaded once with a material testing system, cultured in an incubator and had their length measured on several occasions throughout their growth period. Loading protocol and days of length measurement differed between the trials. The first trial failed, since all of the control bones decreased in length in relation to the day of loading, while they should at least have grown 30% on the fifth day after loading. The results obtained from the second trial indicate that the frequency 0.4 Hz has a great impact on longitudinal growth, with a length increase of 50%-60% in relation to the day of loading. A conclusion regarding the other frequencies studied could not be made due to high spread of length alteration data. The tibias from the last trial did not show any significant results. Moreover, it was concluded that compressive and cyclic loading do promote longitudinal growth, despite the great variation in length alteration for most of the bones, including the control bones. The findings of this study could serve as a foundation for a research study further investigating the relation between frequency and longitudinal growth.

The skeleton has several fundamental functions in the body, providing protection and structure and safeguarding organs, enabling movement and bearing of weight. The significance of having a complete and strong skeleton is essential for individuals, but it is far from certain for those with a skeletal disorder. Skeletal disorders can manifest in various ways, with the common condition of a more fragile skeleton that is prone to fractures under low force and load. Currently, there are over 450,000 individuals estimated to have the most common skeletal disorder, Osteoporosis, in Sweden alone. In 2019, it was estimated that a total of 124,000 fractures related solely to skeletal disorders occurred in Sweden, equivalent to 338 fractures per day. A registry extract from the Swedish Cause of Death Register in 2019 revealed that deaths related to osteoporotic fractures were the third leading cause of death in Sweden, following dementia and cardiovascular disease. Skeletal disorders not only result in a reduced quality of life for individuals but also impose a state cost of nearly 18 billion SEK per year. This cost exceeds the combined expenses of diabetes care and care for patients with multiple sclerosis today. Despite this, skeletal disorders, according to the Swedish Agency for Health Technology Assessment and Assessment of Social Services, remain an undertreated segment, with the majority of cases neither diagnosed, treated, nor provided with other preventive measures for fractures. For Sofie Hellström and her son Gabriel, their perspective on life changed in the summer of 2020 with a diagnosis of Osteogenesis Imperfecta, a skeletal disorder. At Karolinska Institutet, they were offered a piece of mattress as hip protection. Sofie then discovered a global lack of functional clothing for individuals in need of extra protection in their daily lives. This became the starting point for the company OICAN and the vision of providing all children with the best conditions to explore the world. The aim of the project has been to create integrated knee protectors that can prevent injuries and fractures to the knee and femur. The goal has been to develop a pair of pants with integrated protection that does not compromise on protective capability, freedom of movement, or aesthetic design. The project has resulted in prototypes of integrated knee protectors for both adults and children, along with corresponding injection molding tools. In the final stages of the project, the prototypes have been integrated into pants and tested with excellent results.

Hypotension är vanligt förekommande vid anestesi och i den postoperativa fasen. Om blodtrycket sjunker till för låga nivåer eller pågår under för lång tid kan vitala organ som hjärta och njurar ta allvarlig skada. De flesta fall av hypotension behandlas idag retroaktivt. Med möjlighet att kunna upptäcka hypotension innan det uppstår skulle behandling kunna ske i ett förebyggande syfte och på så sätt minska tiden i hypotension för patienten. Med hjälp av maskininlärning går det att analysera blodtryckskurvor och kunna hitta vilka attribut i dem som kan förutse hypotension. Detta projekt har gått ut på att definiera och beräkna attribut för att i framtida arbeten kunna låta en maskininlärningsalgoritm analysera dem. Utöver detta har arbetet med signalbehandling skett för att kunna upptäcka bristande kvalitet på den analyserade signalen och kunna förbättra den vid behov. Målet att definiera och beräkna attribut har lyckats. Målet att kunna avgöra kvaliteten på signalen har lyckats delvis.

The analysis of human movement is important for diagnosis of as wellas planning and evaluating treatments of disorders or injuries affectingmovement. Optical motion capture combined with force plates provideaccurate measurements, but are confined to laboratory settings limiting theirpotential usefulness in clinical applications. Efforts are made to movemeasurements out of the laboratory making them more accessible, cheaperand easier to use for healthcare providers. This work aimed to assess thefeasibility of doing motion analysis with a wearable system consisting ofIMUs and pressure insole sensors, while also developing a methodology thatcould be used for subsequent validation. Six subjects performed walking, sideskipping, squats, chair stands and a balance exercise, while data was collectedsimultaneously from the wearable system and optical motion capture withforce plates. For demonstration, data from one example subject was analysedand included in this work. The wearable system showed promising results formeasuring ground reaction force. Center of pressure errors were relativelyhigh, likely influenced by the choice of method for coordinate transformationbetween the systems. Joint angle errors varied from low to very high fordifferent trials. Ankle dorsiflexion angle showed low errors and pelvis tiltangle high errors for all motion types. There is a need to investigate thecause for these high errors before more measurements are conducted. Themethodology presented in this work can, with a few recommended changes,be used for future validation of the wearable motion analysis system.

This report focuses on the characterization of an acupuncture needle microsensor, designed tomeasure the conductivity and oxygen saturation of tissues in the body, in particular musculartissues. The device is intended to help the practitioner localize and treat sources of chronicneuromuscular pain in patients. Acupuncture is shown in some cases to lower pain in patients.The specific aim of this project was to characterize the functional properties of the microsensor.Oxygen sensing is accomplished using the phosphorescent indicator dye platinum tetraphenyltetrabenzoporphyrin (PtTPTBPF) placed on the tip of an optical fiber placed in the lumen oflong, thin needle, while conductivity sensing is accomplished with a gold-sputtered electrodearrangement at the tip of the needle. The end goal is to get the microsensor needle classified asa medical device. Preclinical tests that are required for the needle to get the approval arediscussed in this report. To determine the needle’s accuracy and precision when measuringconductivity and oxygen saturation, an experimental setup was created in which an in-vitromaterial for the simulation of muscular tissue was utilized. The in-vitro test material wascomprised of a cellulose gel containing different nitrate salts producing a material with similarstiffness to soft tissues in the human body. Different concentrations of the nitrate salts produceddifferent conductivities in the tissue model gels that covered the conductivity span of humantissues. To create different levels of oxygen saturation, the tissue model gels were placed in aplastic bag filled with oxygen or nitrogen. Performance characterizations of individual devicescan be used to calibrate individual devices, which provides data for the technical file used in theapproval of the device as a medical device. However, none of the sensors where able tomeasure the true value of conductivity in the calibration liquids. The oxygen sensor where alsoto slow to get to the true value of the sample. The tests proved that the needle has potential tomeasure the physiochemical properties of oxygen saturation and conductivity in body tissues,but as there is a large variation in measured values between devices, an improvement in devicedesign or manufacturing is likely required in a final medical product.

Introduction: The brain can change its structure and functionality as a result ofexternal factors. The working memory (WM) of the brain is where informationcan be held and manipulated during a short period of time, with the purpose ofachieving higher cognitive functions such as reasoning and learning. The WMimproves in capacity during the development from childhood into adulthood,and variation of improvement is possible as an effect of situational factors andstimuli.Goal: The main goal of this project was to examine the effects of a WMtraining program on power distribution, connectivity and synchronicity withinbrain networks, using an intra-individual analysis approach.Method: A series of magnetoencephalography (MEG) measurements wasacquired for four subjects while they were performing WM and control tasks,during a WM training program, along with an MRI image of the brain for eachof the participants. The data was preprocessed for noise and artifact removaland a source reconstruction was performed. Time-frequency representationsof the data were created and the frequencies were categories into alpha,beta and gamma bands. The power difference between the WM and controltask was calculated as a function of cognitive load of each frequency band,and its variation over load was calculated as a constructed metric called’area under power difference curve’ (AUPDC), and visualised using colourscale representation upon the brain MRI of each subject. Brain parcels thatsignificantly deviated from a random distribution of AUPDC values wereidentified using a Gaussian distribution fit.Results and discussion: All subjects showed a clear improvement inperformance accuracy of the tasks, but as the effect on the power distributionsvaried considerably for each subject and frequency band, other aspects besidepower need to be investigated in order to understand the mechanisms behindthe improvement. However, the overall results indicate that many significantAUPDC values seem to have decreased during the WM training, both forthe positive and negative significant AUPDC values, suggesting a strongerdecreasing trend in power difference over cognitive load and a weaker increasingtrend. This could suggest an improved brain activation efficiency as an effectof the WM training.