to the robot. 3D markers trajectories are recorded by an optoelectronic camera system (OQUS, Qualisys, Sweden). These trajectories are then processed under Matlab (R2018b, The MathWorks, USA) and used to define the constraints of a trajectory planning problem trajectories. 6) Specimen-specific kinematic chain: After the insertion of the intracortical pins, computed tomography scans of the specimens are performed. The radiographic images are acquired by CT-scan at the Unité d’imagerie et anthropologie forensique (HUG). Bone geometries (including intracortical pins and cluster of markers) are then reconstructed. In order to define the segment coordinate systems, a set of bony landmarks are identified as virtual markers following the recommendations of the International Society of Biomechanics (ISB). 7) Shoulder kinematics: Three dimensional trajectories of each marker constituting the bone pins clusters are recorded by an optolectronic camera system (OQUS, Qualisys, Sweden). These trajectories are processed under Matlab (R2018b, The MathWorks, USA) and 3D kinematics is be computed. Bone and joint 3D kinematics are then compared between each experimental condition. Goodness-of-fit parameters (i.e. root mean square error, determination coefficient) and range of motion will be included in this comparison. All computations will be performed under Matlab (R2018b, The Mathworks, USA). Avantages Acromioclavicular proof of concept study using the the B-Lab has following goals: 1) Previous biomechanical evaluation of acromioclavicular joint were only focused on the movements between the scapula and the clavicle. Our plateform will allow to take into consideration the whole shoulder complex and thus to better reproduce in vivo conditions. 2) The use of a robotic manipulator will allow to ensure the reproductibility of the movements induced on the humerus, and thus to have comparable situations between the different conditions tested (i.e. native joint, complete rupture and a set of surgical joint reconstructions). 3) All tests will be done will keeping surrounding structures (e.g. bones, muscles, ligaments). The fusion between motion capture system recordings (i.e. reflective markers) and CT-scan images (i.e. bone geometry) will allow to follow bone position, orientation and movement. In particular, this will allow us to analyse joint congruence. Résultats préliminaires The first tests of the present pilot project are under achievement. The whole feasibility of the proposed methods have been already tested on one cadaveric specimen. The related records are currently being analysed. Ten shoulders will be investigated until December 2020. Regarding the present pilot study, the expected outcomes are: 1) a complete kinematic description of the full shoulder complex in native, complete dislocation and reconstruction conditions, 2) an advanced analysis of the acromioclavicular joint congruence in these different conditions. These results are expected to allow for identification of the surgical procedure leading to the highest stablility of the shoulder complex.
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