Màster Oficial en Enginyeria Biomèdica, Universitat de Barcelona. Curs: 2010-2011. Directors: Dr. Josep Maria Font Llagunes, Dra. Rosa Angulo Barroso i Dr. Josep Medina CasanovasInjuries of the nervous system have a considerable impact on the biopsycho-social aspects of patients because of their potential for resulting life-long disabilities and functional and cognitive deficits. Cervical Spinal Cord Injury and Acquired Brain Injury commonly imply a reduction of the upper extremity functionality which complicate or even preclude the performance of basic Activities of Daily Living. Neurological rehabilitation of patients in specialized hospitals is currently the only alternative for treating patients with neurological disorders such as Acquired Brain Injury and Spinal Cord Injury. The progression of the patients through the complex rehabilitation process has to be systematically evaluated. Unfortunately, clinical assessment of functional capacity in the upper extremities is less advanced than that of lower extremities, and currently too dependent on subjective, qualitative observational motion analysis, which is highly based on intuitive understanding of human motion. Objective quantification of rehabilitation progress is necessary for the improvement of clinical treatment methods and rehabilitation strategies, and to prevent injury. This dissertation presents a practical methodology for the objective and quantitative evaluation of the upper extremity motion in subjects with neurological disorders, with particular focus on tetraplegic subjects with complete or incomplete Spinal Cord Injury (SCI) at the C5-C6 cervical level and who have undergone tendon transfer surgery. The core of the dissertation is a new rigid body biomechanical model to carry out a kinematic and dynamic analysis of the upper extremity motion during an Activity of Daily Living through data acquired by an opto-electronic system. In addition to the model, this dissertation describes a new dedicated set-up for the acquisition of motion data of the upper extremity, and a new processing and analysis chain designed to present relevant summaries of biomechanical information to rehabilitation specialists. The upper extremity biomechanical model consists of 10 segments with 20 Degrees of Freedom. The marker set-up combines the advantages of joint and segment markers to determine the joint centers of rotation and the segments' motions. The model makes possible a comprehensive kinematic and dynamic analysis, improving the evaluation of the upper extremity motion. In contrast to previous upper extremity models, the presented model is able to analyze the grasp motion between the first phalange of the thumb and the first phalange of the index finger, a motion considered as crucial by clinicians. The resulting set of biomechanical measurements (joint and segment kinematics and dynamics, and trajectories of the joints and segment Centers of Mass), which are reported according to clinical standards, provides valuable information for clinicians to achieve a thorough understanding of the upper extremity motion of the patients. Furthermore, the Kinematic and Dynamic analyses of the elbow and shoulder flexionextensions carried out by means of Exploratory Graphical Analysis are suitable to highlight biomechanical differences between healthy and pathological subjects.