Analysis of the spine through a multibody model and IMU technology

The biomechanical analysis of the spine can give important information to clinicians so they can provide appropriate treatment to their patients. It is especially helpful for the surgical planning of people suffering from spine-related pathologies like scoliosis or lower back pain. One of the inputs of the models being used in biomechanical analyses are the kinematics of the spine. This is a highly complex system so in order to recover them, the most widespread technique used is optoelectric motion systems composed of cameras and markers affixed to the skin. But this technique can only be operated in specific laboratories, and are thus constraining for the patient and the clinicians. Moreover, this technique is quite expensive, so a new cheaper and more portable way of obtaining the kinematics of the spine needs to be found. The aim of this master thesis is therefore to simplify the protocol of data acquisition. For this reason, the kinematics will be evaluated thanks to Inertial Measurement Units affixed on the pelvis and the thorax. Those sensors measure the acceleration, angular speed, and magnetic field of the body they are attached to. In order to asses the intervertebral efforts of the spine, a multibody model is developed, based on the anthropometric data of the patient and its spine geometry, as well as the kinematics of the spine and the pelvis like stated before, and the muscles surrounding the spine. It will be demonstrated in this thesis that patient-specific models are important in order to obtain precise results for intervertebral efforts. The benefit of adding muscle structures to the skeletal model will also be presented. Daily life movements, such as walking, kneeling and jumping, will be performed in order for the IMU sensors to gather necessary data to compute the internal efforts of the vertebrae which will be juxtaposed together and compared in order to determine the most demanding movements. Perspectives and improvements will also be proposed for future researches.