Luigi Bertozzi

Investigation of the biomechanic function of cruciate ligaments using kinematics and geometries from a living subject during step up/down motor task

The modeling approach is the only possible way to estimate the biomechanic function of the different anatomical sub-structures of the knee joint in physiological conditions. Subject-specific geometry and kinematic data were the foundations of the 3D quasi-static model adopted for the present work. A previously validated cruciate ligaments model was implemented taking the anatomical twist of the fibers into account. The anatomical load components, developed by the modeled ligaments, were estimated during step up/down motor tasks. The anterior cruciate ligament never developed force, along every directions. The posterior cruciate ligament developed increasing forces with the increasing of the flexion angle until at about 70° of flexion. Bigger repeatability in the force curves was obtained in extension with respect to the flexion movement. In conclusion the proposed model was effective in evaluating loads in the anterior and posterior cruciate ligament during the execution of daily living activities.

Estimation of knee ligaments loads using the modelling approach applied on in-vivo accurate kinematics and morphology of a young subject

The knee joint is a key structure of the human locomotor system. Any lesion or pathology compromising its mobility and stability alters its function. As direct measurements of the contribution of each anatomical structure to the joint function are not viable, modelling techniques must be applied. The present study is aimed at evaluating the importance of anatomical twist in the determination of mechanical stabilising action of the cruciate ligaments during the execution of a daily living activity. For this purpose accurate parameters from nuclear magnetic resonance and 3D-fluoroscopy of a single selected subject during chair risingsitting motor task were used. The modelling of the twist of fibres was fundamental in the determination of the specific behaviour of the posterior cruciate ligament in particular.

Biomechanical Modeling from In-Vivo Data

Biomechanics assists in understanding the living organ functions both in normal conditions and after alterations. It plays an important role in the development of new prostheses, tools and procedures in the diagnostic, surgical and rehabilitative fields. Although experimental approaches produce direct and reliable measurements of the variables of interest, they are invasive and can alter physiological conditions and limit generalization. With the evolution of the medical and the diagnostic technologies, such as MRIs, CTs, EMGs, and EEGs, we can investigate the function of organs and tissues of a living and healthy subject without any or less invasiveness. In this Chapter, the authors survey the states-of-the-art of the biomechanics modeling methods and present a case study of the subject-specific cruciate ligaments model of the knee joint for living activities. In the model, the cross-sectional area and the reference length are estimated by means of subject-specific nuclear magnetic resonance (NMR) and 3D video-fluoroscopy respectively.

IN-VIVO ESTIMATION OF THE TIBIO-FEMORAL CONTACT AREA USING THIN-PLATE SPLINE TOOL

Interaction between articular surfaces at the knee joint allows movement and stability. The knowledge of how this mechanism works in physiological conditions could be very useful for the development of new clinical procedures. The objective of this study was to develop a subject-specific model able to estimate the articular contact area at the tibio-femoral joint avoiding any destructive measurements. Thin plate splines were used to describe articular surfaces and to allow an analytical estimation of the distance between the surfaces. The sensitivity of the model was evaluated and the tibio-femoral contact area was estimated in a living subject. Femoral contact area results were always smaller than the tibial one, whereas tibial contact area results were less repeatable. Increasing the distance threshold, the increase of the contact area was almost linear. High repeatability was obtained sampling each condyle with more than 60 steps. Contact areas, estimated with the loaded knee, were in accordance with p...