Shoulder function and outcome evaluation after surgery using 3D inertial sensors

The importance of outcome evaluation of a medical treatment in orthopedics is currently recognized. In shoulder disease, a large variety of evaluation tools is employed to assess the results of the surgery. However, even if the majority of these evaluations are largely widespread, none was accepted as a universal standard. Since 1990, few researchers have been evaluating the assumption that the movement analysis (with camera-based or electromagnetic systems) is likely to provide objective results. In clinical practice, these techniques are not always applicable for outcome evaluation of a treatment. The surgeons lack a convenient and simple method of evaluating in an objective way a patient's activity and quality of life after a surgery of the shoulder. This project provides a new tool for the objective functional evaluation of shoulder pathologies, a tool that can be easily used by a doctor at a hospital and by the patient at home. It allows the measurement of the biodynamic changes as well as 3D kinematics of the treated shoulder by noting the effects of these changes on clinical results and on the patient's daily activity. The project was split in four complementary studies. In the first study, a new ambulatory device allowing long-term monitoring of the shoulder movement using several inertial sensors (3D gyroscopes, 3D accelerometers) attached on the trunk, the humerus and the scapula's spine was designed. By combining acceleration and angular velocity features of the both humerus during 9 tests, three kinematic scores for the functional assessment of the shoulder were presented to evaluate the shoulder function in patient before and after surgery. The kinematic scores objectively showed the shoulder improvement after surgery. In the second study, a new method was proposed to detect and quantify the dominant upper-limb segment during daily activity. The method was tested on healthy subjects (N=31) and a patient group (N=10, at baseline, 3, 6 and 12 months after surgery) while carrying the system during 8 hours of their daily life. The results showed the dominance of the arm during standing, sitting and walking periods for healthy subjects and the quantification of the shoulder improvement after surgery, by taking into account the presence of the disease in the dominant or the non dominant arm. In the third study, 3D gyroscopes attached on the humerus were used to identify the movements of flexion-extension, abduction-adduction and internal/external rotation of the humerus and to identify the rates of adjunct (deliberate rotation) and conjunct rotations (inherent or automatic rotation) within each movement. The frequencies of each movement (number/hour) for the different ranges of the arm speed, as well as the rate of adjunct and conjunct rotations for each movement were estimated during daily activity in healthy and patient groups. The results provided the values of frequency of each movement and adjunct/conjunct rate based on the data obtained from the healthy group. In the pathological case, we found that the painful dominant shoulder of the patients lost its predominance in favor of the healthy shoulder, the non dominant shoulder. Patients had less pure internal/external rotations and performed less fast movements while after surgery these parameters presented no significant differences with the healthy group. In the fourth study, a new method of detecting the working level of the shoulder was presented. By measuring the arm elevation during motionless periods, we proposed a new score to evaluate the ability of working at a specific level for a definite duration. We showed that this score had an average of 100% (±31%) for healthy subjects while the working level of the painful shoulder was lower than the healthy shoulder and improved significantly after surgery (up to 87% at 6 months). This study provides preliminary evidence of the effectiveness of the proposed system in clinical practice and objectively assesses upper-limb activity during daily activity.

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