| 1. |
- Boström, Pontus, 1982, et al.
(author)
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The SNARE protein SNAP23 and the SNARE-interacting protein Munc18c in human skeletal muscle are implicated in insulin resistance/type 2 diabetes.
- 2010
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 59:8, s. 1870-8
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Our previous studies suggest that the SNARE protein synaptosomal-associated protein of 23 kDa (SNAP23) is involved in the link between increased lipid levels and insulin resistance in cardiomyocytes. The objective was to determine whether SNAP23 may also be involved in the known association between lipid accumulation in skeletal muscle and insulin resistance/type 2 diabetes in humans, as well as to identify a potential regulator of SNAP23. RESEARCH DESIGN AND METHODS: We analyzed skeletal muscle biopsies from patients with type 2 diabetes and healthy, insulin-sensitive control subjects for expression (mRNA and protein) and intracellular localization (subcellular fractionation and immunohistochemistry) of SNAP23, and for expression of proteins known to interact with SNARE proteins. Insulin resistance was determined by a euglycemic hyperinsulinemic clamp. Potential mechanisms for regulation of SNAP23 were also investigated in the skeletal muscle cell line L6. RESULTS: We showed increased SNAP23 levels in skeletal muscle from patients with type 2 diabetes compared with that from lean control subjects. Moreover, SNAP23 was redistributed from the plasma membrane to the microsomal/cytosolic compartment in the patients with the type 2 diabetes. Expression of the SNARE-interacting protein Munc18c was higher in skeletal muscle from patients with type 2 diabetes. Studies in L6 cells showed that Munc18c promoted the expression of SNAP23. CONCLUSIONS: We have translated our previous in vitro results into humans by showing that there is a change in the distribution of SNAP23 to the interior of the cell in skeletal muscle from patients with type 2 diabetes. We also showed that Munc18c is a potential regulator of SNAP23.
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| 2. |
- Brånemark, Rickard, 1960, et al.
(author)
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A novel osseointegrated percutaneous prosthetic system for the treatment of patients with transfemoral amputation: A prospective study of 51 patients.
- 2014
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In: The bone & joint journal. - 2049-4408. ; 96:1, s. 106-13
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Journal article (peer-reviewed)abstract
- Patients with transfemoral amputation (TFA) often experience problems related to the use of socket-suspended prostheses. The clinical development of osseointegrated percutaneous prostheses for patients with a TFA started in 1990, based on the long-term successful results of osseointegrated dental implants. Between1999 and 2007, 51 patients with 55 TFAs were consecutively enrolled in a prospective, single-centre non-randomised study and followed for two years. The indication for amputation was trauma in 33 patients (65%) and tumour in 12 (24%). A two-stage surgical procedure was used to introduce a percutaneous implant to which an external amputation prosthesis was attached. The assessment of outcome included the use of two self-report questionnaires, the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) and the Short-Form (SF)-36. The cumulative survival at two years' follow-up was 92%. The Q-TFA showed improved prosthetic use, mobility, global situation and fewer problems (all p < 0.001). The physical function SF-36 scores were also improved (p < 0.001). Superficial infection was the most frequent complication, occurring 41 times in 28 patients (rate of infection 54.9%). Most were treated effectively with oral antibiotics. The implant was removed in four patients because of loosening (three aseptic, one infection). Osseointegrated percutaneous implants constitute a novel form of treatment for patients with TFA. The high cumulative survival rate at two years (92%) combined with enhanced prosthetic use and mobility, fewer problems and improved quality of life, supports the 'revolutionary change' that patients with TFA have reported following treatment with osseointegrated percutaneous prostheses. Cite this article: Bone Joint J 2014;96-B:106-13.
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| 3. |
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| 4. |
- Brånemark, Rickard, 1960, et al.
(author)
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Bone response to laser-induced micro- and nano-size titanium surface features.
- 2011
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In: Nanomedicine : nanotechnology, biology, and medicine. - : Elsevier BV. - 1549-9642 .- 1549-9634.
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Journal article (peer-reviewed)abstract
- The present study explored whether laser-induced, site-specific implant surface modifications with micro- and nano-scale topography were able to promote bone formation. The aim was to evaluate the biomechanical and histological response to partly laser-modified titanium implants compared with machined implants. After an early 8-week healing period in rabbit tibia and femur, a 250% increase in removal torque was demonstrated for the partly laser-modified surface. Further, different fracture mechanisms were demonstrated for the two surfaces. Histologically, significantly more bone was found in direct contact with the laser-modified surface for the implants in the tibia sites, while a similar amount of bone tissue was observed in contact with the implant in the femoral sites. In conclusion, an improved bone-implant interface anchorage was promoted by an increase in micro- and nano-scale implant surface topography and surface oxide induced by topological laser treatment.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Frossard, Laurent Alain, et al.
(author)
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Load on osseointegrated fixation of a transfemoral amputee during a fall: loading, descent, impact and recovery analysis.
- 2010
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In: Prosthetics and orthotics international. - : Ovid Technologies (Wolters Kluwer Health). - 1746-1553 .- 0309-3646. ; 34:1, s. 85-97
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Journal article (peer-reviewed)abstract
- Falling represents a health risk for lower limb amputees fitted with an osseointegrated fixation mainly because of the potential damage to the fixation. The purpose of this study was to characterize a real forward fall that occurred inadvertently to a transfemoral amputee fitted with an osseointegrated fixation while attending a gait measurement session to assess the load applied on the residuum. The objective was to analyze the load applied on the fixation with an emphasis on the sequence of events, the pattern and the magnitude of the forces and moments. The load was measured directly at 200 Hz using a six-channel transducer. Complementary video footage was also studied. The fall was divided into four phases: Loading (240 ms), descent (620 ms), impact (365 ms) and recovery (2495 ms). The main impact forces and moments occurred 870 ms and 915 ms after the heel contact, and corresponded to 133% BW and 17 % BWm, or 1.2 and 11.2 times the maximum forces and moments applied during the previous steps of the participant, respectively. This study provided key information to engineers and clinicians facing the challenge to design equipment, and rehabilitation and exercise programs to restore safely the locomotion of lower limb amputees.
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| 9. |
- Frossard, L., et al.
(author)
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Apparatus for monitoring load bearing rehabilitation exercises of a transfemoral amputee fitted with an osseointegrated fixation: a proof-of-concept study
- 2010
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In: Gait & Posture. - : Elsevier BV. - 1879-2219 .- 0966-6362. ; 31:2, s. 223-228
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Journal article (peer-reviewed)abstract
- The purpose of this proof-of-concept study was to determine the relevance of direct measurements to monitor the load applied on the osseointegrated fixation of transfemoral amputees during static load bearing exercises. The objectives were (A) to introduce an apparatus using a three-dimensional load transducer, (B) to present a range of derived information relevant to clinicians, (C) to report on the outcomes of a pilot study and (D) to compare the measurements from the transducer with those from the current method using a weighing scale. One transfemoral amputee fitted with an osseointegrated implant was asked to apply 10 kg, 20 kg, 40 kg and 80 kg on the fixation, using self-monitoring with the weighing scale. The loading was directly measured with a portable kinetic system including a six-channel transducer, external interface circuitry and a laptop. As the load prescribed increased from 10 kg to 80 kg, the forces and moments applied on and around the antero-posterior axis increased by four-fold anteriorly and 14-fold medially, respectively. The forces and moments applied on and around the medio-lateral axis increased by nine-fold laterally and 16-fold from anterior to posterior, respectively. The long axis of the fixation was overloaded and underloaded in 17% and 83% of the trials, respectively, by up to + or - 10%. This proof-of-concept study presents an apparatus that can be used by clinicians facing the challenge of improving basic knowledge on osseointegration, for the design of equipment for load bearing exercises and for rehabilitation programs.
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| 10. |
- Frossard, L., et al.
(author)
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Load applied on bone-anchored transfemoral prosthesis: Characterization of a prosthesis-A pilot study
- 2013
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In: Journal of Rehabilitation Research and Development. - : Journal of Rehabilitation Research & Development. - 0748-7711. ; 50:5, s. 619-634
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Journal article (peer-reviewed)abstract
- The objectives of this study were to (1) record the inner-prosthesis loading during activities of daily living (ADLs), (2) present a set of variables comparing loading data, and (3) provide an example of characterization of two prostheses. The load was measured at 200 Hz using a multi-axial transducer mounted between the residuum and the knee of an individual with unilateral transfemoral amputation fitted with a bone-anchored prosthesis. The load was measured while using two different prosthetic knees, mechanical (PRO1) and microprocessor-controlled (PRO2), during six ADLs. The characterization of the prostheses was achieved using a set of variables split into four categories, including temporal characteristics, maximum loading, loading slopes, and impulse. Approximately 360 gait cycles were analyzed for each prosthesis. PRO I showed a cadence improved by 19% and 7%, a maximum force on the long axis reduced by 11% and 19%, and an impulse reduced by 32% and 15% during descent of incline and stairs compared with PRO2, respectively. This work confirmed that the proposed apparatus and characterization can reveal how changes of prosthetic components are translated into inner-prosthetic loading.
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| 11. |
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| 13. |
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| 14. |
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| 15. |
- Häggström, Eva, et al.
(author)
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Vibrotactile evaluation: Osseointegrated versus socket-suspended transfemoral prostheses
- 2013
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In: Journal of Rehabilitation Research and Development. - : Journal of Rehabilitation Research & Development. - 0748-7711 .- 1938-1352. ; 50:10, s. 1423-1434
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Journal article (peer-reviewed)abstract
- This study investigated detection thresholds of vibrometric stimuli in patients with transfemoral amputation supplied with osseointegrated (OI) and socket-suspended prostheses. It included 17 patients tested preoperatively with socket-suspended prostheses and after 2 yr with OI prostheses and a control group (n = 17) using socket-suspended prostheses, evaluated once. Assessments on the prosthetic and intact feet were conducted at six frequencies (8, 16, 32, 64, 125, and 250 Hz). Furthermore, measurements were conducted to investigate how vibrometric signals are transmitted through a test prosthesis. The results showed that the OI group had improved ability to detect vibrations through the prosthesis at 125 Hz (p = 0.01) at follow-up compared with the preoperative measurement. Compared with the control group, the 01 group at follow-up had better ability to detect high frequency vibrations through the prosthesis (125 Hz, p = 0.02; 250 Hz, p = 0.03). The vibrometric signal transmitted through the test prosthesis was reduced at 8, 125, and 250 Hz but was amplified at 16, 32, and 64 Hz. Differences between the OI and the control groups were found in the highest frequencies in which the test prosthesis showed reduction of the vibrometric signal. The study provides insight into the mechanisms of vibration transmission between the exterior and bone-anchored as well as socket-suspended amputation prostheses.
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| 16. |
- Jönsson, Stewe, et al.
(author)
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Osseointegration amputation prostheses on the upper limbs: methods, prosthetics and rehabilitation.
- 2011
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In: Prosthetics and orthotics international. - : Ovid Technologies (Wolters Kluwer Health). - 1746-1553 .- 0309-3646. ; 35:2, s. 190-200
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Journal article (peer-reviewed)abstract
- The osseointegration programme for upper extremity amputation started in Sweden in 1990, when a titanium fixture was first implanted into a thumb. This method has since been used for transhumeral and below-elbow amputation. The treatment involves two surgical procedures. During the first a titanium fixture is surgically attached to the skeleton, and a second procedure six months later involves a skin penetrating abutment to which the prosthesis is attached.
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| 17. |
- Nebergall, Audrey, et al.
(author)
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Stable fixation of an osseointegated implant system for above-the-knee amputees.
- 2012
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In: Acta orthopaedica. - : Medical Journals Sweden AB. - 1745-3682 .- 1745-3674. ; 83:2, s. 121-128
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Journal article (peer-reviewed)abstract
- Background and purpose Rehabilitation of patients with transfemoral amputations is particularly difficult due to problems in using standard socket prostheses. We wanted to assess long-term fixation of the osseointegrated implant system (OPRA) using radiostereometric analysis (RSA) and periprosthetic bone remodeling. Methods 51 patients with transfemoral amputations (55 implants) were enrolled in an RSA study. RSA and plain radiographs were scheduled at 6 months and at 1, 2, 5, 7, and 10 years after surgery. RSA films were analyzed using UmRSA software. Plain radiographs were graded for bone resorption, cancellization, cortical thinning, and trabecular streaming or buttressing in specifically defined zones around the implant. Results At 5 years, the median (SE) migration of the implant was -0.02 (0.06) mm distally. The rotational movement was 0.42 (0.32) degrees around the longitudinal axis. There was no statistically significant difference in median rotation or migration at any follow-up time. Cancellization of the cortex (plain radiographic grading) appeared in at least 1 zone in over half of the patients at 2 years. However, the prevalence of cancellization had decreased by the 5-year follow-up. Interpretation The RSA analysis for the OPRA system indicated stable fixation of the implant. The periprosthetic bone remodeling showed similarities with changes seen around uncemented hip stems. The OPRA system is a new and promising approach for addressing the challenges faced by patients with transfemoral amputations.
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| 18. |
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| 19. |
- Ortiz Catalan, Max Jair, 1982, et al.
(author)
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An osseointegrated human-machine gateway for long-term sensory feedback and motor control of artificial limbs
- 2014
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In: Science Translational Medicine. - : American Association for the Advancement of Science (AAAS). - 1946-6234 .- 1946-6242. ; 6:257
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Journal article (peer-reviewed)abstract
- A major challenge since the invention of implantable devices has been a reliable and long-term stable transcutaneous communication. In the case of prosthetic limbs, existing neuromuscular interfaces have been unable to address this challenge and provide direct and intuitive neural control. Although prosthetic hardware and decoding algorithms are readily available, there is still a lack of appropriate and stable physiological signals for controlling the devices. We developed a percutaneous osseointegrated (bone-anchored) interface that allows for permanent and unlimited bidirectional communication with the human body. With this interface, an artificial limb can be chronically driven by implanted electrodes in the peripheral nerves and muscles of an amputee, outside of controlled environments and during activities of daily living, thus reducing disability and improving quality of life. We demonstrate in one subject, for more than 1 year, that implanted electrodes provide a more precise and reliable control than surface electrodes, regardless of limb position and environmental conditions, and with less effort. Furthermore, long-term stable myoelectric pattern recognition and appropriate sensory feedback elicited via neurostimulation was demonstrated. The opportunity to chronically record and stimulate the neuromuscular system allows for the implementation of intuitive control and naturally perceived sensory feedback, as well as opportunities for the prediction of complex limb motions and better understanding of sensory perception. The permanent bidirectional interface presented here is a critical step toward more natural limb replacement, by combining stable attachment with permanent and reliable human-machine communication.
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| 20. |
- Ortiz Catalan, Max Jair, 1982, et al.
(author)
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Biologically inspired algorithms applied to prosthetic control
- 2012
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In: BioMed 2012 , February 15 – 17, 2012, Innsbruck, Austria. - 9780889869097 ; :track 764
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Conference paper (peer-reviewed)abstract
- Biologically inspired algorithms were used in this work to approach different components of pattern recognition applied to the control of robotic prosthetics. In order to contribute with a different training paradigm, Evolutionary (EA) and Particle Swarm Optimization (PSO) algorithms were used to train an Artificial Neural Network (ANN). Since the optimal input set of signal features is yet unknown, a Genetic Algorithm (GA) was used to approach this problem. The training length and rate of convergence were considered in the search of an optimal set of signal features, as well as for the optimal time window length. The ANN proved to be an accurate pattern recognition algorithm predicting 10 movements with over 95% accuracy. Moreover, new combinations of signal features with higher convergence rates than the commonly found in the literature were discovered by the GA. It was also found that the PSO had better performance that the EA as a training algorithm but worse than the well established Back-propagation. The latter considered accuracy, training length and convergence. Finally, the common practice of using 200 ms time window was found to be sufficient for producing acceptable accuracies while remaining short enough for a real-time control.
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| 21. |
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| 22. |
- Ortiz Catalan, Max Jair, 1982, et al.
(author)
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BioPatRec: A modular research platform for the control of artificial limbs based on pattern recognition algorithms
- 2013
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In: Source Code for Biology and Medicine. - : Springer Science and Business Media LLC. - 1751-0473. ; 8
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Journal article (peer-reviewed)abstract
- Background Processing and pattern recognition of myoelectric signals have been at the core of prosthetic control research in the last decade. Although most studies agree on reporting the accuracy of predicting predefined movements, there is a significant amount of study-dependent variables that make high-resolution inter-study comparison practically impossible. As an effort to provide a common research platform for the development and evaluation of algorithms in prosthetic control, we introduce BioPatRec as open source software. BioPatRec allows a seamless implementation of a variety of algorithms in the fields of 1) Signal processing; 2) Feature selection and extraction; 3) Pattern recognition; and, 4) Real-time control. Furthermore, since the platform is highly modular and customizable, researchers from different fields can seamlessly benchmark their algorithms by applying them in prosthetic control, without necessarily knowing how to obtain and process bioelectric signals, or how to produce and evaluate physically meaningful outputs. Results BioPatRec is demonstrated in this study by the implementation of a relatively new pattern recognition algorithm, namely Regulatory Feedback Networks (RFN). RFN produced comparable results to those of more sophisticated classifiers such as Linear Discriminant Analysis and Multi-Layer Perceptron. BioPatRec is released with these 3 fundamentally different classifiers, as well as all the necessary routines for the myoelectric control of a virtual hand; from data acquisition to real-time evaluations. All the required instructions for use and development are provided in the online project hosting platform, which includes issue tracking and an extensive "wiki". This transparent implementation aims to facilitate collaboration and speed up utilization. Moreover, BioPatRec provides a publicly available repository of myoelectric signals that allow algorithms benchmarking on common data sets. This is particularly useful for researchers lacking of data acquisition hardware, or with limited access to patients. Conclusions BioPatRec has been made openly and freely available with the hope to accelerate, through the community contributions, the development of better algorithms that can potentially improve the patient's quality of life. It is currently used in 3 different continents and by researchers of different disciplines, thus proving to be a useful tool for development and collaboration.
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| 23. |
- Ortiz Catalan, Max Jair, 1982, et al.
(author)
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Effect on signal-to-noise ratio of splitting the continuous contacts of cuff electrodes into smaller recording areas
- 2013
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In: Journal of NeuroEngineering and Rehabilitation. - : Springer Science and Business Media LLC. - 1743-0003. ; 10:1, s. 22-
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Journal article (peer-reviewed)abstract
- ABSTRACT: BACKGROUND: Cuff electrodes have been widely used chronically in different clinical applications. This neural interface has been dominantly used for nerve stimulation while interfering noise is the major issue when employed for recording purposes. Advancements have been made in rejecting extra-neural interference by using continuous ring contacts in tripolar topologies. Ring contacts provide an average of the neural activity, and thus reduce the information retrieved. Splitting these contacts into smaller recording areas could potentially increase the information content. In this study, we investigate the impact of such discretization on the Signal-to-Noise Ratio (SNR). The effect of contacts positioning and an additional short circuited pair of electrodes were also addressed. METHODS: Different recording configurations using ring, dot, and a mixed of both contacts were studied in vitro in a frog model. An interfering signal was induced in the medium to simulate myoelectric noise. The experimental setup was design in such a way that the only difference between recordings was the configuration used. The inter-session experimental differences were taking care of by a common configuration that allowed normalization between electrode designs. RESULTS: It was found that splitting all contacts into small recording areas had negative effects on noise rejection. However, if this is only applied to the central contact creating a mixed tripole configuration, a considerable and statistically significant improvement was observed. Moreover, the signal to noise ratio was equal or larger than what can be achieved with the best known configuration, namely the short circuited tripole. This suggests that for recording purposes, any tripole topology would benefit from splitting the central contact into one or more discrete contacts. CONCLUSIONS: Our results showed that a mixed tripole configuration performs better than the configuration including only ring contacts. Therefore, splitting the central ring contact of a cuff electrode into a number of dot contacts not only provides additional information but also an improved SNR. In addition, the effect of an additional pair of short circuited electrodes and the "end effect" observed with the presented method are in line with previous findings by other authors.
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| 24. |
- Ortiz Catalan, Max Jair, 1982, et al.
(author)
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Evaluation of Classifier Topologies for the Real-time Classification of Simultaneous Limb motions
- 2013
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In: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. - 9781457702167 ; , s. 6651-6654
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Conference paper (peer-reviewed)abstract
- The prediction of motion intent through the decoding of myoelectric signals has the potential to improve the functionally of limb prostheses. Considerable research on individual motion classifiers has been done to exploit this idea. A drawback with the individual prediction approach, however, is its limitation to serial control, which is slow, cumbersome, and unnatural. In this work, different classifier topologies suitable for the decoding of mixed classes, and thus capable of predicting simultaneous motions, were investigated in real-time. These topologies resulted in higher offline accuracies than previously achieved, but more importantly, positive indications of their suitability for real-time systems were found. Furthermore, in order to facilitate further development, benchmarking, and cooperation, the algorithms and data generated in this study are freely available as part of BioPatRec, an open source framework for the development of advanced prosthetic control strategies.
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| 25. |
- Ortiz Catalan, Max Jair, 1982, et al.
(author)
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On the viability of implantable electrodes for the natural control of artificial limbs: Review and discussion
- 2012
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In: BioMedical Engineering OnLine. - 1475-925X. ; 11:33
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Journal article (peer-reviewed)abstract
- The control of robotic prostheses based on pattern recognition algorithms is a widely studied subject that has shown promising results in acute experiments. The long-term implementation of this technology, however, has not yet been achieved due to practical issues that can be mainly attributed to the use of surface electrodes and their highly environmental dependency. This paper describes several implantable electrodes and discusses them as a solution for the natural control of artificial limbs. In this context "natural" is defined as producing control over limb movement analogous to that of an intact physiological system. This includes coordinated and simultaneous movements of different degrees of freedom. It also implies that the input signals must come from nerves or muscles that were originally meant to produce the intended movement and that feedback is perceived as originating in the missing limb without requiring burdensome levels of concentration. After scrutinizing different electrode designs and their clinical implementation, we concluded that the epimysial and cuff electrodes are currently promising candidates to achieving a long-term stable and natural control of robotic prosthetics, provided that communication from the electrodes to the outside of the body is guaranteed.
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