10:30   Rehabilitation and Pain Development process of an advanced upper extremity orthoses for functional support of patients with muscle weakness Suzanne Filius Abstract: Muscular dystrophies, such as Duchenne muscular dystrophy (DMD) are progressive neuromuscular diseases that affect the skeletal muscle tissue. Resulting in severe muscle weakness and formation of joint contractures over time. Around the age of 12, boys with DMD start to use a wheelchair and cope with upper extremity function loss as well . With the current life expectancy (>30y old) these boys and men are in a wheelchair for the major part of their life and dependent on their upper extremity. If left unsupported, they are limited in their daily activities and social participation for a long period . The objective of the project is to design, build and evaluate an active 4 degrees of freedom (DOF) arm support to make the arm feel lighter and give back independent task execution. In order to achieve this goal, first 1) user needs and requirements were identified. Currently, 2) the hardware and the control strategy are under development. The following step is, 3) to validate the hardware design and control performance in healthy control subjects. The final step is, 4) to evaluate the proof of concept of the prototype in boys with DMD. In the initial phase of the project, it was found that over the past century many attempts have been made to develop supports for arm disabilities in daily life. ,4 Unfortunately, only few are commercially available, the lowest percentage in active-actuated devices. Although the passive arm supports may suffice for the initial stage of DMD, there is a gap and a need for active devices for the following level of impairment.4 In the second phase of the project, a single DOF set-up is built to investigate and compare two gravity compensation strategies. In addition, a method to identify the elevated elbow joint impedance for additional compensation is tested. The current results are a good step towards the realization of the 4DOF design. During the conference the development process and achieved results will be presented. Human-in-the-loop optimisation of power assisted wheelchair propulsion Remco de Vries, Han Houdijk, Cassandra Kraaijenbrink, Jelmer Braaksma, Sonja de Groot, Riemer Vegter Abstract: Handrim Wheelchairs users frequently experience fatigue and overuse problems during ambulation [1]. One way to overcome this, is adding extra mechanical power through a motor to the wheel. These so-called Pushrim Activated Power Assisted Wheelchairs (PAPAW) are exemplified by the WheelDrive produced by Indes (Enschede, The Netherlands). The WheelDrive measures the forces which are exerted on the pushrims and amplifies the power output of the user through a motor attached to each wheel. Because PAPAWs work independently on each side[1], the inevitable push asymmetry of the user [2] is also amplified, causing issues in controlling the wheelchair. Furthermore, because of the differences in work capacity and impairment of each individual, ideally the support of the WheelDrive should be personalized. In this project we attempt to optimize the actuation control of both wheels of the WheelDrive using a human-in-the-loop approach. By use of an Esseda wheelchair ergometer produced by Lode B.V.(Groningen, The Netherlands)wdetailed measurements of power output and wheelchair propulsion technique can be derived. Combining these measurements synchronously with the power output of the WheelDrive, generates the ability to accurately analyse the behaviour of the user without the added power, contrary to earlier research which looked at the combined output of the entire WheelDrive-user system. Based on the combined information of both systems, the Human-in-the-Loop optimisation algorithm will optimize the settings of both individual wheels of the WheelDrive to customize it to the individual needs of the user, by use of an covariance matrix adaptation evolutionary strategy (CMA-ES). Currently the rate of rise, jerk and push frequency as captured by the wheelchair ergometer are given priority in the optimization criterion because these propulsion parameters are related to the quality of the propulsion.[3] Combining these parameters into a single weighted cost-function drives the optimization algorithm to generate the new set of parameters in subsequent iterations until an optimum is found. The development of the experimental setup and the cost-function are finished and currently work as a proof of concept. An able-bodied case-study has been performed showcasing the potential. Future experiments are necessary to see if the individually optimized support setting is beneficial over the regular settings on wheelchair biomechanics and physiological outcomes as well as functional outcomes. [1] de Klerk, R., Lutjeboer, T., Vegter, R. J. K., & van der Woude, L. H. V. (2018). Practice-based skill acquisition of pushrim-activated power-assisted wheelchair propulsion versus regular handrim propulsion in novices. Journal of NeuroEngineering and Rehabilitation, 15(1), 1–10. https://doi.org/10.1186/s12984-018-0397-4 [2] Vegter, R. J. K., Lamoth, C. J., de Groot, S., Veeger, D. H. E. J., & van der Woude, L. H. V. (2013). Variability in bimanual wheelchair propulsion: consistency of two instrumented wheels during handrim wheelchair propulsion on a motor driven treadmill. Journal of NeuroEngineering and Rehabilitation, 10(1), 9. https://doi.org/10.1186/1743-0003-10-9 [3] Beirens, B. J. H., Bossuyt, F. M., Arnet, U., van der Woude, L. H. V., & de Vries, W. H. K. (2020). Shoulder Pain Is Associated With Rate of Rise and Jerk of the Applied Forces During Wheelchair Propulsion in Individuals With Paraplegic Spinal Cord Injury. Archives of Physical Medicine and Rehabilitation, 1. https://doi.org/10.1016/j.apmr.2020.10.114 Femoral fracture risk prediction using a crushable foam material model Navid SoltaniHafshejani, Thom Bitter, Nico Verdonschot, Dennis Janssen Abstract: INTRODUCTION :Femoral fracture prediction can be used to estimate the risk of an impending fracture of the pathologic situation. Finite element analysis (FEA) has been shown to be able to improve clinical failure risk assessments. However, improvements can be made in the material model used in FEA. In the current study, FE models of the proximal femur were compared with experiments to investigate the suitability of an Isotropic Crushable Foam (ICF) model for the failure risk assessment, relative to simulations with a softening Von-Mises (sVM) criterion. METHODS: Five human cadaveric femora, aged 63 to 96 years old (4 males and 1 female), were examined previously [1] in our laboratory to assess the failure load and fracture patterns in a stance-type load. A QCT-based FE model of each proximal femur was created and the experimental situation were mimicked perfectly. The ICF and sVM criteria were applied to the FE models. In contrast to the sVM yield criterion, the ICF model included pressure-dependent parameters in the constitutive formulation. RESULTS: The ICF model correctly predicted the fracture location in 4 out of 5 bones but, the sVM was unable to capture different fracture locations in the proximal femur . The ICF model and sVM criterion were able to simulate the failure load with an average accuracy of 88 % and 82 %, respectively, compared to the experiments. Moreover, the estimated proximal femoral stiffness in the ICF model was comparable to the experimental results, while the computed stiffness was commonly overestimated in the sVM models. DISCUSSION: While the sVM model used a single material model to replicate the proximal femur, the ICF model used here made a distinction between trabecular and cortical bone properties, with trabecular bone as a pressure-dependent cellular structure and cortical bone as a compact structure. This distinction improved the prediction of the fracture location and failure load as compared to the experimental results. SIGNIFICANCE: An ICF material model was developed for the human proximal femur that allows for the evaluation of the fracture risk in pathologic femurs, but also for the peri-prosthetic fractures and collapse of joint reconstructions. REFERENCE: [1] L. C. Derikx et al., "The assessment of the risk of fracture in femora with metastatic lesions: comparing case-specific finite element analyses with predictions by clinical experts," The Journal of bone and joint surgery. British volume, vol. 94, no. 8, pp. 1135-1142, 2012. Computation of a patient-specific auricular prosthesis model based on 3D surface scanning Tjitske Bannink, Maarten van Alphen, Baris Karakullukçu, Michiel van den Brekel Abstract: Background Patients with facial defects experience decreased quality of life. This can be improved with a customized, facial prosthesis that restores anatomic structures and enhances facial appearance. However, the conventional process of fabrication of such prostheses is time-consuming and highly dependent on the skills of the anaplastologist. Building on previous research on the use of 3D scanning and printing in auricular prosthetics, we developed a new computer-aided method of designing auricular prosthesis for patients with a unilateral ear defect, with the aim of reducing these limitations. Methods Digital surface data of the face, unaffected auricle and defective skin is obtained by 3D surface scanning (Artec 3D, Luxembourg). A patient specific prosthesis design is computed using an in-house developed algorithm in MATLAB R2020b (The MathWorks, Natick, MA). The prosthesis model is created by mirroring the contralateral unaffected side of the face, followed by a transformation to optimize the auricle’s position and shape. Next, the auricle is extracted, the depth is adapted to the defective surface and the edge is warped to the defective surface to create a seamless fit of the prosthesis to the skin. Results Digital prosthesis models resulting from the algorithm show a case specific shape, size, position and orientation based on the 3D surface data. Computation of a model takes below 10 minutes, dependent on the specifications of the computer. Five easy, user-friendly manual operations (selecting landmarks, drawing a region of interest and optimizing parameters), are required to run the algorithm. Conclusions First tests of this novel method for digital design of auricular prostheses on patient data have shown promising results. Next step is implementing and evaluating the methodology in the clinical workflow. The aesthetic appearance of the resulting prostheses will be the main outcome measure in this evaluation, but time savings and decreased dependency on the artistic skills of the anaplastologist due to automation of the design process are also of interest. Physical activity patterns of patients with chronic low back pain and central sensitization: insights from a machine learning method Xiaoping Zheng, Michiel Reneman, Egbert Otten, Claudine Lamoth Abstract: Introduction: Chronic low back pain (CLBP) is the leading global cause of disability. Central sensitization (CS) is present in a subsample of patients with CLBP. Optimal physical activity (PA) is often recommended in the management of CLBP because it can reduce the risk of disability. However, the evidence of the relationship between PA intensity levels and CLBP is inconsistent, and the knowledge about the association with CS is limited. This study aimed to investigate PA patterns in patients with CLBP and low or high CS using an unsupervised machine learning approach. Methods: Forty-two patients were included (23 CLBP-, a CS Inventory score lower than 40; 19 CLBP+, 40-100). Patients wore a 3D accelerometer for about one week. For each patient, 4 days of data were used for analyses. Accelerometer data were corrected for gravity and the vector magnitude was calculated. For each group, a Hidden semi Markov Model (HSMM) was made to measure the temporal organization and transition of hidden states (PA intensity levels), based on accelerometer vector magnitude. Differences between CLBP- and CLBP+ in duration and occupation of hidden states were assessed with independent t-tests. The transition probability was assessed by Binomial-proportion test. The compositions of corresponding hidden states were assessed with Jensen–Shannon divergence (JSD). Results: The corresponding 5 hidden states of CLBP- and CLBP+ were similar, indicated by JSD. These states were defined as: rest (e.g., sleeping), sedentary (e.g., desk work), light activity (e.g., standing), light locomotion (e.g., slow walking), and moderate-vigorous activities (e.g., fast walking). Significant differences between 2 groups showed that CLBP+ exhibited higher duration and transition probability of active state (light activity, light locomotion, and moderate-vigorous states) and higher duration of inactive state (rest and sedentary states). Discussion: The significant differences in temporal organization and transition of PA levels may suggest that CLBP- and CLBP+ had different PA patterns. CLBP+ group exhibited a prolonged period of activity engagement (overactive) and then had a long period of rest. This PA pattern may suggest that CLBP+ had the distress-endures response pattern. Combined psychophysical and neurophysiological tools for mechanism-based observation of impaired nociceptive processing Jan Buitenweg Abstract: Chronic pain is sustained and amplified by impaired nociceptive processing. In patients with chronic neuropathic pain, spontaneous ectopic activity causes long episodes of pain and drives central sensitization. In patients with chronic nociplastic pain, sensitization and reduced inhibition of nociception lead to pain amplification and the generation of pain by activation of other sensory modalities, often for unknown reasons. It remains difficult for clinicians to effectively treat neuropathic, nociplastic or mixed chronic pain because it is difficult to observe the underlying physiological mechanisms and the effect of treatments on those mechanisms. A mechanism based approach could enable early diagnosis and selection of effective treatments to improve the outlook for neuropathic, nociplastic and mixed pain patients. This presentation is about our first steps towards the development of new assessment methods, by improving the observability of nociceptive processing mechanisms in a research or clinical setting. Our strategy was to combine psychophysical methods for the observation of nociceptive processing with neurophysiological techniques to provide objective mechanism-based information on nociceptive function. Combined observation of nociceptive detection thresholds and evoked potentials allows for the observation of impaired nociceptive processing following sleep deprivation, in a setup for pharmacological testing, as well as the identification of impaired nociceptive processing in patients with failed back surgery syndrome at the hospital. New techniques might improve the accuracy of our observations. Automated measurement of nociceptive detection thresholds based on brain activity could eventually lead to a more objective, faster and accessible procedure for measuring the nociceptive detection threshold. Intra-epidermal electric steady-state evoked potentials provide a method to observe brain activity associated with the sensory-discriminative aspects of the pain experience. The potential of these methods warrants further research to determine in which chronic pain conditions impaired nociceptive processing can be observed using these methods, and whether the observed values can be used to guide pain treatment.

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