1,721,225 research outputs found
Kinect and wearable inertial sensors for motor rehabilitation programs at home: state of the art and an experimental comparison
Full text linkEmerging sensing and communication technologies are contributing to the development of many motor rehabilitation programs outside the standard healthcare facilities. Nowadays, motor rehabilitation exercises can be easily performed and monitored even at home by a variety of motion-tracking systems. These are cheap, reliable, easy-to-use, and allow also remote configuration and control of the rehabilitation programs. The two most promising technologies for home-based motor rehabilitation programs are inertial wearable sensors and video-based motion capture systems
Joint kinematics from functional adaptation: A validation on the tibio-talar articulation
Full text linkBiologic tissues respond to the biomechanical conditions to which they are exposed by modifying their architecture. Experimental evidence from the literature suggests that the aim of this process is the mechanical optimization of the tissues (functional adaptation). In particular, this process must produce articular surfaces that, in physiological working conditions, optimize the contact load distribution or, equivalently, maximize the joint congruence. It is thus possible to identify the space of adapted joint configurations (or adapted space of motion) starting solely from knowledge of the shape of the articular surfaces, by determining the envelope of the maximum congruence configurations. The aim of this work was to validate this hypothesis by testing its application on 10 human ankle joints. Digitalizations of articular surfaces were acquired in 10 in-vitro experimental sessions, together with the natural passive tibio-talar motion, which may be considered as representative of the adapted space of motion. This latter was predicted numerically by optimizing the joint congruence. The highest mean absolute errors between each component of predicted and experimental motion were 2.07° and 2.29 mm respectively for the three rotations and translations. The present kinematic model replicated the experimentally observed motion well, providing a reliable subject-specific representation of the joint motion starting solely from articulating surface shapes
Ortesi piede-caviglia articolata con asse di rotazione flottante
No full textL’invenzione riguarda un’ortesi articolata (1,1’) comprendente un primo scafo (2,2’) da associare ad un piede (20,20’), un secondo scafo (3,3’) da associare ad una gamba (30,30’) ed una coppia di giunti (10,10’,10’’,10’’’); a sua volta, ciascun giunto (10,10’,10’’,10’’’) comprende una prima piastra interna (4,4’,4’’,4’’’) solidale con il primo scafo (2,2’) dalla parte opposta al piede (20,20’), una seconda piastra esterna (5,5’,5’’,5’’’) solidale con il secondo scafo (3,3’) dalla parte opposta alla gamba (30,30’) e dotata di un foro (50,50’,50’’,50’’’), un distanziale (6,6’,6’’,6’’’), una contro-piastra filettata (7,7’,7’’,7’’’) e un perno di collegamento (8,8’,8’’,8’’’) solidale con la prima piastra interna (4,4’,4’’,4’’’) e la cui testa è in battuta sul primo scafo (2,2’) dalla parte opposta alla prima piastra interna (4,4’,4’’,4’’’), in cui il foro (50,50’,50’’,50’’’) della seconda piastra esterna (5,5’,5’’,5’’’) presenta un diametro maggiore rispetto al diametro del distanziale (6,6’,6’’,6’’’) per ottenere un gioco radiale reciproco, ed in cui il distanziale (6,6’,6’’,6’’’) attraversa il foro (50,50’,50’’,50’’’) della seconda piastra esterna (5,5’,5’’,5’’’) ed è disposto a contatto con la prima piastra interna (4,4’,4’’,4’’’) e con la contro-piastra filettata (7,7’,7’’,7’’’), ed in cui la distanza tra la superficie esterna (40) della prima piastra (4,4’,4’’,4’’’) e la superficie interna (70) della contro-piastra filettata (7,7’,7’’,7’’’) è determinata dalla lunghezza del distanziale (6,6’,6’’,6’’’,6’’’’) e risulta maggiore dello spessore della seconda piastra esterna (5,5’,5’’,5’’’) per ottenere un gioco assiale reciproco, in modo che la coppia di detti giunti (10,10’,10’’,10’’’) presenta gli assi dei perni di collegamento (8,8’,8”,8’’’) allineati tra loro e consente al primo scafo (2,2’) e al secondo scafo (3,3’) un movimento relativo a sei gradi di libertà consistenti in due traslazioni indipendenti nel piano sagittale, una traslazione in direzione medio-laterale, una rotazione nel piano sagittale rispetto a un asse medio-laterale, una rotazione nel piano frontale rispetto a un asse antero-posteriore e una rotazione nel piano trasversale rispetto a un asse longitudinale, cosicché l’asse di rotazione della coppia di giunti (10,10’,10’’,10’’’) risulta flottante nell’intorno del centro anatomico dell’articolazione di un utente e l’ortesi articolata (1,1’) asseconda la cinematica naturale dell’articolazione dell’utente
The foot and ankle complex as a four degrees‐of‐freedom system: Kinematic coupling among the foot bones
No full textSeventy‐eight parameters are theoretically needed to describe the relative position and
orientation of all the 14 bones in the foot and ankle with respect to a reference bone
(foot posture). However, articular contacts and soft tissues introduce kinematic coupling,
reducing the number of the foot degrees‐of‐freedom (DOF). This study aims at providing
quantification and definition of these couplings. The foot posture was measured in vitro
through a series of computed tomography scans, spanning the whole range of foot dorsi/
plantar flexion and pronation/supination, also considering the effect of weightbearing.
The envelope of foot postures was investigated by means of principal component
analysis. The foot and ankle motion were well described with four principal sets of
kinematic couplings, that is, synergies. One synergy covers the independent motion of
the ankle, while three synergies describe the foot motion. The first foot synergy shows all
the bones rotating approximatively about a common axis, mapping the foot abduction/
adduction about the Chopart joint. The second foot synergy results in a spherical motion,
whose center is located between lateral cuneiform and navicular bone, mapping the foot
pronation/supination. The third foot synergy maps the opening of the foot arches during
the load acceptance. The foot and ankle complex can thus be described as a four DOF
system, whose motion is the result of the linear combination of four synergies. Significance:
Synergies reveal the contribution of each bone to the three‐dimensional foot
posture, providing a compact representation of the motion of the foot and ankle complex,
improving the comprehension of its physiology
In vivo kinematics of knee replacement during daily living activities: Condylar and post-cam contact assessment by three-dimensional fluoroscopy and finite element analyses
Full text linkIn total knee replacement, the investigation on the exact contact patterns at the post-cam in implanted patients from real in vivo data during daily living activities is fundamental for validating implant design concepts and assessing relevant performances. This study is aimed at verifying the restoration of natural tibio-femoral condylar kinematics by investigating the post-cam engagement at different motor tasks. An innovative validated technique, combining three-dimensional fluoroscopic and finite element analyses, was applied to measure joint kinematics during daily living activities in 15 patients implanted with guided motion posterior-stabilized total knee replacement. Motion results showed physiological antero-posterior translations of the tibio-femoral condyles for every motor task. However, high variability was observed in the position of the calculated pivot point among different patients and different motor tasks, as well as in the range of post-cam engagement. Physiological tibio-femoral joint rotations and contacts at the condyles were found restored in the present knee replacement. Articular contact patterns experienced at the post-cam were found compatible with this original prosthesis design. The present study reports replaced knee kinematics also in terms of articular surface contacts, both at the condyles and, for the first time, at the post-cam
Mechanics of the anterior drawer test at the ankle: the effects of ligament viscoelasticity
No full textMAL-POSITIONING OF A NOVEL TOTAL ANKLE REPLACEMENT: A SENSITIVITY STUDY
No full textOverall biomechanical behaviour of replaced ankle joints is dependent also on the position and orientation of the prosthesis components relative to the bone and the soft tissues. Mal-positioned compoenents could lead to instability promoting the ultimate failure of the implant. The aim of the present work was investigating the sensitivity of a mobile bearing ankle replacement to prosthesis component final position. For this purpose, a previosuly validated explicit finite element (FE9 model of a novel ankle prosthesis, which includes also eight major ligaments was used to asses the influence of prosthesis mal-positioning relative to the ligaments to joint kinematics, polyethylene contact pressure and stress ligament forces
A musculoskeletal model of the ankle joint complex for the analysis of the dynamic behavior of an ankle prosthesis
No full textThe ankle joint complex constitutes a biomechanical system of extreme complexity. Both in case of joint arthrodesis and joint replacement, the analysis of the forces generated under dynamic conditions is crucial. In the present work, we developed a musculoskeletal model of the ankle joint complex in order to: (a) analyze the physiological movements of the ankle joints, (b) evaluate the forces experienced by ligaments, muscles and at the contacts between tibia and talus, and (c) evaluate the effects of the insertion of a modern ankle prosthesis
Author Correction: 3D measurement techniques for the hindfoot alignment angle from weight-bearing CT in a clinical population
Full text linkCone-beam CT (CBCT) scans now enable accurate measurements on foot skeletal structures with
the advantage of observing these in 3D and in weight-bearing. Among the most common skeletal
deformities, the varus/valgus of the hindfoot is the most complex to be represented, and a number
of measure proposals have been published. This study aims to analyze and to compare these
measurements from CBCT scans in a real clinical population with large such deformity. Ten patients
with severe acquired adult fatfoot and indication for surgery underwent CBCT scans (Carestream,
USA) while standing on that leg, before and after surgical correction. Corresponding 3D shape of each
bone of the distal shank and hindfoot were defned (Materialise, Belgium). Six diferent techniques
from the literature were used to calculate the varus/valgus deformity, i.e. the inclination of the
hindfoot in the frontal plane of the shank. Standard clinical measurements by goniometers were taken
for comparison. According to these techniques, and starting from a careful 3D reconstruction of the
relevant foot skeletal structures, a large spectrum of measurements was found to represent the same
hindfoot alignment angle. Most of them were very diferent from the traditional clinical measures. The
assessment of the pre-operative valgus deformity and of the corresponding post-operative correction
varied considerably. CBCT fnally allows 3D assessment of foot deformities in weight-bearing.
Measurements from the diferent available techniques do not compare well, as they are based on
very diferent approaches. It is recommended to be aware of the anatomical and functional concepts
behind these techniques before clinical and surgical conclusions
- …
