Performances of an accelerometric device for detecting fall and loss of consciousness

Falls and loss of consciousness (FLoC) is the leading cause of serious health problems, above all in the elderly population, since the subjects involved are not able to ask for help and may lie in critical conditions for a long time, thus deteriorating into severe conditions which can even lead to death. Therefore, developing a device capable of automatically detecting a FLoC and activating an alarm call seems to be of utmost importance. This study intended to develop such a device using an accelerometer sensor. Four hundred and sixty simulated falls were performed by 20 subjects: 10 young subjects and 10 elderly subjects. The young subjects were asked to perform 200 FLoCs as well as 60 non common activities (NCAs), whereas the elderly subjects were asked to carry out only 200 activities of daily living (ADL). The signal used to detect the fall event was acquired by a single accelerometer placed on the subjects' belts. The test set was divided into two groups of the same size: Training Set (TS) and Verification Set (VS). The first set was meant to determine the related algorithm, whereas the second set was intended to check its reliability. The proposed algorithm was devised to detect the effects of the three phases of a FLoC (impact of the body on the ground, lying position and immobility) into the acceleration and jerk signals along the cranio-caudal axis (CCA). The correct detection of all FLoC cases and the absence of false positives among ADL corroborate the usefulness of the device proposed.

[Functional analysis after Achilles tendon repair]

The Achilles tendon rupture (ATR) is a severe injury and requires a surgical treatment which can result in functional impairment, limiting unprofessional sports activities. In order to evaluate this potential impairment 20 subjects (SG) who had received surgical treatment for ATR and 20 healthy subjects (CG) were required to execute vertical jump according to counter movement jump and squat jump protocol. For both groups the flying time (Tv) of each foot has been acquired, adopting accelerometric transducers positioned posteriorly at the level of malleolar axis. The SG's Tv is significantly lesser than the CG's one, demonstrating an inferior global performance respect to healthy people and the operated leg has a Tv 6% higher than the contralateral, while in the CG there are no statistical difference between the Tv of the limbs. For seven operated subjects Tv values are lesser than threshold values obtained from CG. For them sports activity which implies high and cyclic stress on the lower limbs could be dangerous. Functional evaluation, consequently, allow to assess impairments not differently estimable.

Biomechanical effects of prosthesis neck geometries to contrast limb lengthening after hip replacement

Hip prostheses should meet the anatomical and physiological characteristics of patients; this is the rationale for designing modular implants of different sizes. To optimize implant geometry, it is necessary to consider, not only the prosthesis component design, but also the final configuration of the implanted leg. This means the necessity to consider the specific morphological and functional condition of ""that"" patient and not only of ""that"" hip to restore, at best, limb functions. Variations in the length of the implanted limb are frequent; therefore, the variations in the three geometrical features of the hip prosthesis neck, which can affect the restoration of the anatomical symmetry of the limbs, were investigated: (i) neck lengths (Ln ), between 50.5 and 64.5 mm; (ii) cervico-diaphyseal (CD) angle ( ã ), between 135 and 125 degrees and; (iii) anteversion (AV) angle ( â ), between 0 and 15 degrees . Adopting a three-dimensional (3D) simplified biomechanical model, the resultant load acting on the hip was estimated for each different design solution; corresponding stress distributions and contact pressures at the interface between the prosthesis head and the ultra high molecular weight polyethylene (UHMWPE) layer were evaluated by 3D finite element (FE) analyses and using the Strozzi approach. The following values have been assumed as physiological values: ã = ã p = 125 degrees , â = â p = 15 degrees and Ln = 57 mm; it was found that to contrast limb lengthening, if the CD angle varies from 135-125 degrees (with neck length Ln = 64.5 mm and AV = 0 degrees ), the joint resultant load decreases by 8.8% (7.2% if AV = 15 degrees ); the contact pressure de-creases by 5.8%, (5% if AV = 15 degrees ); the bending moment in the stem neck increases by 10.9% (13.8% if AV = 15 degrees ) and the torque increases by 1% (12.8% if AV = 15 degrees ).

A combined XPS-SEM/EDX investigation on explanted UHMW polyethylene acetabular cups: possible role of silicon traces in the wear debris

An investigation was started aimed at a better understanding of the complex phenomena leading to chemical degradation and morphological deterioration of UHMW polyethylene cups in total hip prostheses. Analysis was performed on retrieved implants which needed revision due to inflammation and pain problems. Preliminary results obtained by parallel XPS and SEM/EDX experiments gave evidence, for the first time, that silicon traces are involved in the process of particle formation and segregation onto the surface of the cups. The extent of modification of the surface chemical composition of cups and the process of particle segregation seem to be correlated to both the implant time and to some particular features of patient (age, activity, style of life, etc.). Investigation on a large number of samples is in progress in order to test this hypothesis. The results obtained so far confirmed the potential of surface spectroscopies (XPS) in biomaterial investigations.