Rita Stagni

Comparison of Knee Cruciate Ligaments Models Using Kinematics from a Living Subject during Chair Rising-Sitting

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 comparing cruciate ligaments models of different complexity using accurate parameters from RMN and 3D-fluoroscopy of a single selected subject during chair rising-sitting motor task.. The complexity of the model was not relevant for the calculation of the strain range of the cruciate ligaments fibres. On the other hand, three-dimensionality and anatomical twist of the modelled fibres resulted to be fundamental for the geometrical strain distribution over the ligament section.

Kinematic study of a reconstructed hip in paediatric oncology.

In 1997, a large portion of the femur of a four-year-old child affected by a Ewings sarcoma was reconstructed with an innovative technique that used a massive bone allograft, in conjunction with a vascularised fibula autograft that was directly articulated within the acetabulum. The aim of the present study was to assess the kinematic behaviour of the reconstructed hip during flexion, once the acute remodelling process observed after the operation had ceased. A few additional CT slices of the hip joint region, in a flexed position, were taken at month 33 of the follow-up. The helical axes relative to the neutral-flexion motor action were estimated: their relative positions, with respect to the anatomical femoral heads, were compared, and the translation of the anatomical head centres was estimated. The angles spanned by the two femurs were almost equal, as were the translations along the respective helical axis. The main difference between the two femurs was the distance between the estimated femoral head centres and the relative helical axes. This resulted in a non-negligible translation of 2.9 mm of the fibula head inside the acetabulum during flexion, significantly higher than the 0.5 mm found for the intact contralateral femur. The results showed that, although the transplanted fibula grew and remodelled during the follow up, the action of the reconstructed hip joint still cannot be described as a ball-and-socket.

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.

INVERSE DYNAMICS MODELING IN GAIT ANALYSIS: AN APPLICATION

A method based on inverse dynamics modeling for the subject specific in vivo evaluation of muscle activity in one subject during the execution of chair rising is being described in this article. Th...

BIOMECHANICS OF THE INTACT AND REPLACED HUMAN ANKLE JOINT

The main objective of the study was to develop advanced biomechanical models of the intact human ankle complex. It was also aimed at designing a total ankle replacement which would better reproduce the physiological function of the joint. Passive flexion was analyzed in a number of lower-leg preparations with stereophotogrammetry and radiostereometry. The articular surfaces and fibres within the calcaneofibular and tibiocalcaneal ligaments were observed to prescribe the changing positions of bones, ligaments and instantaneous axis of rotation. Joint motion included rolling as well as sliding. Computer-based models elucidated this kinematics at the intact joint, and how changing positions of the centre of rotation and muscle lines of action affect lever arm length at different flexion angles. The mechanical response of the joint to anterior drawer and talar tilt tests was explained in terms of fibre recruitment. The experimental evidence and the geometrical models gave the basis for the design of a novel a...

Comparison of Knee Cruciate Ligaments Models Using In-vivo Step Up-Down Kinematics

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 comparing cruciate ligaments models of different complexity using accurate parameters from MRI and 3D-fluoroscopy of a single selected subject during step up-down motor task. The complexity of the model was not very relevant for the calculation of the strain range of the cruciate ligaments fibres. On the other hand, three-dimensionality and anatomical twist of the modelled fibres resulted to be fundamental for the geometrical strain distribution over the ligament section.