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228 results on '"Widmer, Jonas"'

2. A new sensing paradigm for the vibroacoustic detection of pedicle screw loosening

Author

Seibold, Matthias, Sigrist, Bastian, Götschi, Tobias, Widmer, Jonas, Hodel, Sandro, Farshad, Mazda, Navab, Nassir, Fürnstahl, Philipp, and Laux, Christoph J.

Subjects
Physics - Medical Physics
Abstract

There is an unmet clinical need for developing novel methods to complement and replace the current radiation-emitting imaging-based methods for the detection of loose pedicle screws as a complication after spinal fusion surgery which fail to identify a substantial amount of loose implants. In this work, we propose a new methodology and paradigm for the radiation-free, non-destructive, and easy-to-integrate detection of pedicle screw loosening based on vibroacoustic sensing. Furthermore, we propose a novel simulation technique for pedicle screw loosening, which is biomechanically validated. For the detection of a loose implant, we excite the vertebra of interest with a sine sweep vibration at the spinous process and attach a custom highly-sensitive piezo contact microphone to the screw head to capture the propagated vibration characteristics which are analyzed using a detection pipeline based on spectrogram features and a SE-ResNet-18. To validate the proposed approach, we conducted experiments using four human cadaveric lumbar spine specimens and evaluate our algorithm in a cross validation experiment. Our method reaches a sensitivity of 91.50 +- 6.58% and a specificity of 91.10 +- 2.27%. The proposed system shows great potentials for the development of alternative assessment methods for implant loosening based on vibroacoustic sensing.

Published
2022

32. Bone density optimized pedicle screw insertion

Author

Tsagkaris, Christos, primary, Calek, Anna-Katharina, additional, Fasser, Marie-Rosa, additional, Spirig, José Miguel, additional, Caprara, Sebastiano, additional, Farshad, Mazda, additional, and Widmer, Jonas, additional

Published
2023
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38. Bullingers Briefwechsel zugänglich machen: Stand der Handschriftenerkennung

Author

Ströbel, Phillip, Hodel, Tobias, Fischer, Andreas, Scius-Bertrand, Anna, Wolf, Beat, Janka, Anna, Widmer, Jonas, Scheurer, Patricia, Volk, Martin, Trilcke, Peer, Busch, Anna, Helling, Patrick, Plum, Alistair, Wolter, Vivien, Weis, Joëlle, Chudoba, Hendrik, and University of Zurich

Subjects
style adaptation, 100 Philosophy, Data augmentation, Annotieren, Manuskript, 410 Linguistics, 800 Literature, rhetoric & criticism, maschinelles Lernen, 000 Computer science, knowledge & systems, correspondence, Daten, handwritten text recognition, OCR, 10105 Institute of Computational Linguistics, Bewertung, Handschriftenerkennung, DHd2023, history, digital humanities, 900 History, Transkription
Abstract

"Anhand des Briefwechsels Heinrich Bullingers (1504-1575), das rund 10'000 Briefe umfasst, demonstrieren wir den Stand der Forschung in automatisierter Handschriftenerkennung. Es finden sich mehr als hundert unterschiedliche Schreiberhände in den Briefen mit sehr unterschiedlicher Verteilung. Das Korpus ist zweisprachig (Latein/Deutsch) und teilweise findet der Sprachwechsel innerhalb von Abschnitten oder gar Sätzen statt. Auf Grund dieser Vielfalt eignet sich der Briefwechsel optimal als Testumgebung für entsprechende Algorithmen und ist aufschlussreiche für Forschungsprojekte und Erinnerungsinstitutionen mit ähnlichen Problemstellungen. Im Paper werden drei Verfahren gegeneinander gestellt und abgewogen. Im folgenden werde drei Ansätze an dem Korpus getestet, die Aufschlüsse zum Stand und möglichen Entwicklungen im Bereich der Handschriftenerkennung versprechen. Erstens wird mit Transkribus eine etablierte Plattform genutzt, die zwei Engines (HTR+ und PyLaia) anbietet. Zweitens wird mit Hilfe von Data Augmentation versucht die Erkennung mit der state-of-the-art Engine HTRFlor zu verbessern und drittens werden neue Transformer-basierte Modelle (TrOCR) eingesetzt." Ein Beitrag zur 9. Tagung des Verbands "Digital Humanities im deutschsprachigen Raum" - DHd 2023 Open Humanities Open Culture.

Published
2023
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40. Spine Biomechanics in the Work of Aristotle (384 – 322 BC).

Author

Tsagkaris, Christos, Kalachanis, Konstantinos, Widmer, Jonas, and Farshad, Mazda

Abstract

Background: Spine biomechanics is a field of applied research aiming to unravel the biomechanical understanding of the spine and its disorders and to understand the implications of their interventional therapy to improve clinical practice, physical performance and daily living. Its scientific whereabouts can be traced in the work of Aristotle, who discussed physical and biological concepts of spine biomechanics in a series of treatises. Results: The authors searched the Thesaurus Linguae Graecae archive for original texts written in Greek and attributed to Aristotle and selected excerpts of medical and biological treatises that elaborate on spine biomechanics. Discussion: While many of his theories have become outdated, his methodology and rationale remain relevant for contemporary researchers and clinicians. Here, the relevant content of passages of the corpus aristotelicum related to spine biomechanics and discuss their practical implications are presented. [ABSTRACT FROM AUTHOR]

Published
2023
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42. Modic type 2 changes are fibroinflammatory changes with complement system involvement adjacent to degenerated vertebral endplates

Author

Heggli, Irina, primary, Laux, Christoph J., additional, Mengis, Tamara, additional, Karol, Agnieszka, additional, Cornaz, Frédéric, additional, Herger, Nick, additional, Aradi‐Vegh, Borbala, additional, Widmer, Jonas, additional, Burkhard, Marco D., additional, Farshad‐Amacker, Nadja A., additional, Pfammatter, Sibylle, additional, Wolski, Witold E., additional, Brunner, Florian, additional, Distler, Oliver, additional, Farshad, Mazda, additional, and Dudli, Stefan, additional

Published
2022
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46. Subject-Specific Alignment and Mass Distribution in Musculoskeletal Models of the Lumbar Spine

Author

Fasser, Marie-Rosa, Jokeit, Moritz, Kalthoff, Mirjam, Gomez Romero, David A, Trache, Tudor, Snedeker, Jess G, Farshad, Mazda, Widmer, Jonas, University of Zurich, and Widmer, Jonas

Subjects
spine loading prediction, 1502 Bioengineering, subject-specificity, musculoskeletal modelling, 2204 Biomedical Engineering, Bioengineering and Biotechnology, bi-planar radiography, 610 Medicine & health, thoracolumbar alignment, 2722 Histology, spine biomechanics, upper body mass distribution, automatized model generation, 1305 Biotechnology, 10046 Balgrist University Hospital, Swiss Spinal Cord Injury Center, Original Research
Abstract

Musculoskeletal modeling is a well-established method in spine biomechanics and generally employed for investigations concerning both the healthy and the pathological spine. It commonly involves inverse kinematics and optimization of muscle activity and provides detailed insight into joint loading. The aim of the present work was to develop and validate a procedure for the automatized generation of semi-subject-specific multi-rigid body models with an articulated lumbar spine. Individualization of the models was achieved with a novel approach incorporating information from annotated EOS images. The size and alignment of bony structures, as well as specific body weight distribution along the spine segments, were accurately reproduced in the 3D models. To ensure the pipeline's robustness, models based on 145 EOS images of subjects with various weight distributions and spinopelvic parameters were generated. For validation, we performed kinematics-dependent and segment-dependent comparisons of the average joint loads obtained for our cohort with the outcome of various published in vivo and in situ studies. Overall, our results agreed well with literature data. The here described method is a promising tool for studying a variety of clinical questions, ranging from the evaluation of the effects of alignment variation on joint loading to the assessment of possible pathomechanisms involved in adjacent segment disease., Frontiers in Bioengineering and Biotechnology, 9, ISSN:2296-4185

Published
2021

47. Bone density optimized pedicle screw instrumentation improves screw pull-out force in lumbar vertebrae

Author

Caprara, Sebastiano, Fasser, Marie-Rosa, Spirig, José Miguel, Widmer, Jonas, Snedeker, Jess G, Farshad, Mazda, Senteler, Marco, University of Zurich, and Caprara, Sebastiano

Subjects
1709 Human-Computer Interaction, 1502 Bioengineering, 1706 Computer Science Applications, 2204 Biomedical Engineering, 610 Medicine & health, 10046 Balgrist University Hospital, Swiss Spinal Cord Injury Center
Published
2022

49. Modic type 2 changes are fibroinflammatory changes with complement system involvement adjacent to degenerated vertebral endplates.

Author

Heggli, Irina, Laux, Christoph J., Mengis, Tamara, Karol, Agnieszka, Cornaz, Frédéric, Herger, Nick, Aradi‐Vegh, Borbala, Widmer, Jonas, Burkhard, Marco D., Farshad‐Amacker, Nadja A., Pfammatter, Sibylle, Wolski, Witold E., Brunner, Florian, Distler, Oliver, Farshad, Mazda, and Dudli, Stefan

Subjects
COMPLEMENT activation, EXTRACELLULAR matrix proteins, LUMBAR pain, MAGNETIC resonance imaging, GRANULATION tissue
Abstract

Background: Vertebral endplate signal intensity changes visualized by magnetic resonance imaging termed Modic changes (MC) are highly prevalent in low back pain patients. Interconvertibility between the three MC subtypes (MC1, MC2, MC3) suggests different pathological stages. Histologically, granulation tissue, fibrosis, and bone marrow edema are signs of inflammation in MC1 and MC2. However, different inflammatory infiltrates and amount of fatty marrow suggest distinct inflammatory processes in MC2. Aims: The aims of this study were to investigate (i) the degree of bony (BEP) and cartilage endplate (CEP) degeneration in MC2, (ii) to identify inflammatory MC2 pathomechanisms, and (iii) to show that these marrow changes correlate with severity of endplate degeneration. Methods: Pairs of axial biopsies (n = 58) spanning the entire vertebral body including both CEPs were collected from human cadaveric vertebrae with MC2. From one biopsy, the bone marrow directly adjacent to the CEP was analyzed with mass spectrometry. Differentially expressed proteins (DEPs) between MC2 and control were identified and bioinformatic enrichment analysis was performed. The other biopsy was processed for paraffin histology and BEP/CEP degenerations were scored. Endplate scores were correlated with DEPs. Results: Endplates from MC2 were significantly more degenerated. Proteomic analysis revealed an activated complement system, increased expression of extracellular matrix proteins, angiogenic, and neurogenic factors in MC2 marrow. Endplate scores correlated with upregulated complement and neurogenic proteins. Discussion: The inflammatory pathomechanisms in MC2 comprises activation of the complement system. Concurrent inflammation, fibrosis, angiogenesis, and neurogenesis indicate that MC2 is a chronic inflammation. Correlation of endplate damage with complement and neurogenic proteins suggest that complement system activation and neoinnervation may be linked to endplate damage. The endplate‐near marrow is the pathomechanistic site, because MC2 occur at locations with more endplate degeneration. Conclusion: MC2 are fibroinflammatory changes with complement system involvement which occur adjacent to damaged endplates. [ABSTRACT FROM AUTHOR]

Published
2023
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