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1.  The Effect of Aging on the Specialized Conducting System: A Telemetry ECG Study in Rats over a 6 Month Period 
PLoS ONE  2014;9(11):e112697.
Advanced age alone appears to be a risk factor for increased susceptibility to cardiac arrhythmias. We previously observed in the aged rat heart that sinus rhythm ventricular activation is delayed and characterized by abnormal epicardial patterns although conduction velocity is normal. While these findings relate to an advanced stage of aging, it is not yet known when and how ventricular electrical impairment originates and which is the underlying substrate. To address these points, we performed continuous telemetry ECG recordings in freely moving rats over a six-month period to monitor ECG waveform changes, heart rate variability and the incidence of cardiac arrhythmias. At the end of the study, we performed in-vivo multiple lead epicardial recordings and histopathology of cardiac tissue. We found that the duration of ECG waves and intervals gradually increased and heart rate variability gradually decreased with age. Moreover, the incidence of cardiac arrhythmias gradually increased, with atrial arrhythmias exceeding ventricular arrhythmias. Epicardial multiple lead recordings confirmed abnormalities in ventricular activation patterns, likely attributable to distal conducting system dysfunctions. Microscopic analysis of aged heart specimens revealed multifocal connective tissue deposition and perinuclear myocytolysis in the atria. Our results demonstrate that aging gradually modifies the terminal part of the specialized cardiac conducting system, creating a substrate for increased arrhythmogenesis. These findings may open new therapeutic options in the management of cardiac arrhythmias in the elderly population.
PMCID: PMC4232439  PMID: 25398004
2.  Lateral ankle instability in high-demand athletes: reconstruction with fibular periosteal flap 
International Orthopaedics  2013;37(9):1839-1844.
Fibular periosteal flaps have been used to address chronic lateral ankle instability, but there are no studies in the literature reporting functional outcomes after this particular procedure in high-demand athletes. We postulated that for chronic instability, nonanatomical reconstruction of the lateral ankle ligament with a fibular periosteal flap will return high-demand athletes to their previous levels of activity.
Forty patients who had grade III ankle sprain and experienced no success after a course of supervised conservative management lasting at least six months and who had a preinjury Tegner score of ≥6 underwent a lateral compartment reconstruction with a fibular periosteal flap. Each patient was given the Tegner and Karlsson questionnaire and was evaluated by the Zwipp method, Foot and Ankle Outcome Score (FAOS) and the American Orthopaedic Foot and Ankle Society (AOFAS) score at the six-month, one, two and three-year time points. Range of motion (ROM) of the affected ankle was assessed, and stress X-rays were performed. Mean patient age was 24.5 (range17–30) years, and no patient was lost to follow-up.
Mean follow-up was 36 (minimum 18) months, mean Tegner scores at the one, two and three-year time points were 8.8, 8.9 and 8.9, respectively, and mean Karlsson scores were 93 ± 5.2, 95 ± 3.1 and 94.9, respectively. AOFAS and FAOS scores improved from a mean of 69.4 and 71.4, respectively, in the preoperative group to a mean of 97.2 and 94.4, respectively, at the last follow-up. The ROM was equal to the contralateral ankle in all but two patients at the two-year follow-up. No major complications were found.
Nonanatomical ligament reconstruction with a fibular periosteal flap for chronic lateral ankle instability was effective in returning high-demand athletes to their preinjury functional levels.
PMCID: PMC3764284  PMID: 23942989
Lateral ankle instability; High-demand athlete; Fibula periosteal flap; Functional outcomes
3.  A Novel HMM Distributed Classifier for the Detection of Gait Phases by Means of a Wearable Inertial Sensor Network 
Sensors (Basel, Switzerland)  2014;14(9):16212-16234.
In this work, we decided to apply a hierarchical weighted decision, proposed and used in other research fields, for the recognition of gait phases. The developed and validated novel distributed classifier is based on hierarchical weighted decision from outputs of scalar Hidden Markov Models (HMM) applied to angular velocities of foot, shank, and thigh. The angular velocities of ten healthy subjects were acquired via three uni-axial gyroscopes embedded in inertial measurement units (IMUs) during one walking task, repeated three times, on a treadmill. After validating the novel distributed classifier and scalar and vectorial classifiers-already proposed in the literature, with a cross-validation, classifiers were compared for sensitivity, specificity, and computational load for all combinations of the three targeted anatomical segments. Moreover, the performance of the novel distributed classifier in the estimation of gait variability in terms of mean time and coefficient of variation was evaluated. The highest values of specificity and sensitivity (>0.98) for the three classifiers examined here were obtained when the angular velocity of the foot was processed. Distributed and vectorial classifiers reached acceptable values (>0.95) when the angular velocity of shank and thigh were analyzed. Distributed and scalar classifiers showed values of computational load about 100 times lower than the one obtained with the vectorial classifier. In addition, distributed classifiers showed an excellent reliability for the evaluation of mean time and a good/excellent reliability for the coefficient of variation. In conclusion, due to the better performance and the small value of computational load, the here proposed novel distributed classifier can be implemented in the real-time application of gait phases recognition, such as to evaluate gait variability in patients or to control active orthoses for the recovery of mobility of lower limb joints.
PMCID: PMC4208171  PMID: 25184488
gait detection; Hidden Markov Models; hierarchical decision; distributed classifier; wearable sensor network; gyroscopes
4.  Shoulder motor performance assessment in the sagittal plane in children with hemiplegia during single joint pointing tasks 
Pointing is a motor task extensively used during daily life activities and it requires complex visuo-motor transformation to select the appropriate movement strategy. The study of invariant characteristics of human movements has led to several theories on how the brain solves the redundancy problem, but the application of these theories on children affected by hemiplegia is limited. This study aims at giving a quantitative assessment of the shoulder motor behaviour in children with hemiplegia during pointing tasks.
Eight children with hemiplegia were involved in the study and were asked to perform movements on the sagittal plane with both arms, at low and high speed. Subject movements were recorded using an optoelectronic system; a 4-DOF model of children arm has been developed to calculate kinematic and dynamic variables. A set of evaluation indexes has been extracted in order to quantitatively assess whether and how children modify their motor control strategies when perform movements with the more affected or less affected arm.
In low speed movements, no differences can be seen in terms of movement duration and peak velocity between the More Affected arm (MA) and the Less Affected arm (LA), as well as in the main characteristics of movement kinematics and dynamics. As regards fast movements, remarkable differences in terms of strategies of motor control can be observed: while movements with LA did not show any significant difference in Dimensionless Jerk Index (JI) and Dimensionless Torque-change Cost index (TC) between the elevation and lowering phases, suggesting that motor control optimization is similar for movements performed with or against gravity, movements with MA showed a statistically significant increase of both JI and TC during lowering phase.
Results suggest the presence of a different control strategy for fast movements in particular during lowering phase. Results suggest that motor control is not able to optimize Jerk and Torque-change cost functions in the same way when controls the two arms, suggesting that children with hemiplegia do not actively control MA lowering fast movements, in order to take advantage of the passive inertial body properties, rather than to attempt its optimal control.
PMCID: PMC4128539  PMID: 25073726
Motor assessment; Hemiplegia; Cerebral palsy; Kinematics; Biomechanics
5.  Signs of Cardiac Autonomic Imbalance and Proarrhythmic Remodeling in FTO Deficient Mice 
PLoS ONE  2014;9(4):e95499.
In humans, variants of the fat mass and obesity associated (FTO) gene have recently been associated with obesity. However, the physiological function of FTO is not well defined. Previous investigations in mice have linked FTO deficiency to growth retardation, loss of white adipose tissue, increased energy metabolism and enhanced systemic sympathetic activation. In this study we investigated for the first time the effects of global knockout of the mouse FTO gene on cardiac function and its autonomic neural regulation. ECG recordings were acquired via radiotelemetry in homozygous knockout (n = 12) and wild-type (n = 8) mice during resting and stress conditions, and analyzed by means of time- and frequency-domain indexes of heart rate variability. In the same animals, cardiac electrophysiological properties (assessed by epicardial mapping) and structural characteristics were investigated. Our data indicate that FTO knockout mice were characterized by (i) higher heart rate values during resting and stress conditions, (ii) heart rate variability changes (increased LF to HF ratio), (iii) larger vulnerability to stress-induced tachyarrhythmias, (iv) altered ventricular repolarization, and (v) cardiac hypertrophy compared to wild-type counterparts. We conclude that FTO deficiency in mice leads to an imbalance of the autonomic neural modulation of cardiac function in the sympathetic direction and to a potentially proarrhythmic remodeling of electrical and structural properties of the heart.
PMCID: PMC3990670  PMID: 24743632
6.  A Wireless Flexible Sensorized Insole for Gait Analysis 
Sensors (Basel, Switzerland)  2014;14(1):1073-1093.
This paper introduces the design and development of a novel pressure-sensitive foot insole for real-time monitoring of plantar pressure distribution during walking. The device consists of a flexible insole with 64 pressure-sensitive elements and an integrated electronic board for high-frequency data acquisition, pre-filtering, and wireless transmission to a remote data computing/storing unit. The pressure-sensitive technology is based on an optoelectronic technology developed at Scuola Superiore Sant'Anna. The insole is a low-cost and low-power battery-powered device. The design and development of the device is presented along with its experimental characterization and validation with healthy subjects performing a task of walking at different speeds, and benchmarked against an instrumented force platform.
PMCID: PMC3926603  PMID: 24412902
sensorized insole; plantar pressure distribution; gait analysis; real-time gait monitoring; wearable sensor
7.  Feasibility Study of a Wearable Exoskeleton for Children: Is the Gait Altered by Adding Masses on Lower Limbs? 
PLoS ONE  2013;8(9):e73139.
We are designing a pediatric exoskeletal ankle robot (pediatric Anklebot) to promote gait habilitation in children with Cerebral Palsy (CP). Few studies have evaluated how much or whether the unilateral loading of a wearable exoskeleton may have the unwanted effect of altering significantly the gait. The purpose of this study was to evaluate whether adding masses up to 2.5 kg, the estimated overall added mass of the mentioned device, at the knee level alters the gait kinematics. Ten healthy children and eight children with CP, with light or mild gait impairment, walked wearing a knee brace with several masses. Gait parameters and lower-limb joint kinematics were analyzed with an optoelectronic system under six conditions: without brace (natural gait) and with masses placed at the knee level (0.5, 1.0, 1.5, 2.0, 2.5 kg). T-tests and repeated measures ANOVA tests were conducted in order to find noteworthy differences among the trial conditions and between loaded and unloaded legs. No statistically significant differences in gait parameters for both healthy children and children with CP were observed in the five “with added mass” conditions. We found significant differences among “natural gait” and “with added masses” conditions in knee flexion and hip extension angles for healthy children and in knee flexion angle for children with CP. This result can be interpreted as an effect of the mechanical constraint induced by the knee brace rather than the effect associated with load increase. The study demonstrates that the mechanical constraint induced by the brace has a measurable effect on the gait of healthy children and children with CP and that the added mass up to 2.5 kg does not alter the lower limb kinematics. This suggests that wearable devices weighing 25 N or less will not noticeably modify the gait patterns of the population examined here.
PMCID: PMC3762849  PMID: 24023822
8.  A Flexible Sensor Technology for the Distributed Measurement of Interaction Pressure 
Sensors (Basel, Switzerland)  2013;13(1):1021-1045.
We present a sensor technology for the measure of the physical human-robot interaction pressure developed in the last years at Scuola Superiore Sant'Anna. The system is composed of flexible matrices of opto-electronic sensors covered by a soft silicone cover. This sensory system is completely modular and scalable, allowing one to cover areas of any sizes and shapes, and to measure different pressure ranges. In this work we present the main application areas for this technology. A first generation of the system was used to monitor human-robot interaction in upper- (NEUROExos; Scuola Superiore Sant'Anna) and lower-limb (LOPES; University of Twente) exoskeletons for rehabilitation. A second generation, with increased resolution and wireless connection, was used to develop a pressure-sensitive foot insole and an improved human-robot interaction measurement systems. The experimental characterization of the latter system along with its validation on three healthy subjects is presented here for the first time. A perspective on future uses and development of the technology is finally drafted.
PMCID: PMC3574719  PMID: 23322104
distributed force sensor; wearable robotics; physical human-robot interaction; pressure-sensitive insole
9.  Stress-Induced Susceptibility to Sudden Cardiac Death in Mice with Altered Serotonin Homeostasis 
PLoS ONE  2012;7(7):e41184.
In humans, chronic stressors have long been linked to cardiac morbidity. Altered serotonergic neurotransmission may represent a crucial pathophysiological mechanism mediating stress-induced cardiac disturbances. Here, we evaluated the physiological role of serotonin (5-HT) 1A receptors in the autonomic regulation of cardiac function under acute and chronic stress conditions, using 5-HT1A receptor knockout mice (KOs). When exposed to acute stressors, KO mice displayed a higher tachycardic stress response and a larger reduction of vagal modulation of heart rate than wild type counterparts (WTs). During a protocol of chronic psychosocial stress, 6 out of 22 (27%) KOs died from cardiac arrest. Close to death, they displayed a severe bradycardia, a lengthening of cardiac interval (P wave, PQ and QRS) duration, a notched QRS complex and a profound hypothermia. In the same period, the remaining knockouts exhibited higher values of heart rate than WTs during both light and dark phases of the diurnal rhythm. At sacrifice, KO mice showed a larger expression of cardiac muscarinic receptors (M2), whereas they did not differ for gross cardiac anatomy and the amount of myocardial fibrosis compared to WTs. This study demonstrates that chronic genetic loss of 5-HT1A receptors is detrimental for cardiovascular health, by intensifying acute, stress-induced heart rate rises and increasing the susceptibility to sudden cardiac death in mice undergoing chronic stress.
PMCID: PMC3399824  PMID: 22815962
10.  The trivector approach for minimally invasive total knee arthroplasty: A technical note 
One of the main criticisms of minimally invasive approaches in total knee arthroplasty has been their poor adaptability in cases of major deformity or stiffness of the knee joint. When they are used in such cases, excessive soft-tissue tension is needed to provide appropriate joint exposure. Here, we describe the “mini trivector approach,” which has become our standard approach for total knee replacement because it permits us to enlarge the indication for minimally or less invasive total knee replacement to many knees where quad sparing, a subvastus approach, or a mini quad or mini midvastus snip may not be sufficient to achieve correct exposure. It consists of a limited double snip of the VMO and the quadriceps tendon that reduces tension on the extensor mechanism and allows easier verticalization of the patella as well as good joint exposure.
PMCID: PMC3427701  PMID: 22527151
Total knee replacement; Minimally invasive; Trivector
11.  Selective recognition of DNA from olive leaves and olive oil by PNA and modified-PNA microarrays 
Artificial DNA, PNA & XNA  2012;3(2):63-72.
PNA probes for the specific detection of DNA from olive oil samples by microarray technology were developed. The presence of as low as 5% refined hazelnut (Corylus avellana) oil in extra-virgin olive oil (Olea europaea L.) could be detected by using a PNA microarray. A set of two single nucleotide polymorphisms (SNPs) from the Actin gene of Olive was chosen as a model for evaluating the ability of PNA probes for discriminating olive cultivars. Both unmodified and C2-modified PNAs bearing an arginine side-chain were used, the latter showing higher sequence specificity. DNA extracted from leaves of three different cultivars (Ogliarola leccese, Canino and Frantoio) could be easily discriminated using a microarray with unmodified PNA probes, whereas discrimination of DNA from oil samples was more challenging, and could be obtained only by using chiral PNA probes.
PMCID: PMC3429532  PMID: 22772038
PNA; olive oil; hazelnut oil; SNP; cultivar identification; DNA fingerprinting
12.  Ceramic Femoral Components in Total Knee Arthroplasty - Two Year Follow-Up Results of an International Prospective Multi-Centre Study 
Total knee arthroplasty can be considered as a reliable surgical procedure with a good long-term clinical result. However, implant failure due to particle induced aseptic loosening as well as the aspect of hypersensitivity to metal ions still remains an emerging issue.
The purpose of this prospective international multi-centre study was to evaluate the clinical and radiological outcomes and the reliability of the unconstrained Multigen Plus Total Knee System with a new BIOLOX® delta ceramic femoral component. Cemented total knee arthroplasty was performed on 108 patients (110 knees) at seven hospitals in three countries. Clinical and radiological evaluations were performed preoperatively, and after 3, 12 and 24 months postoperatively using the HSS-, WOMAC-, SF-36-score and standardised X-rays.
The mean preoperative HSS-Score amounted to 55.5 ± 11.5 points and improved significantly in all postoperative evaluations (85.7 ± 11.7 points at 24 months). Furthermore, improvements in WOMAC- and SF-36-score were evaluated as significant at all points of evaluation. Radiolucent lines around the femoral ceramic component at 24 months were found in four cases. Progression of radiolucent lines was not seen and no implant loosening was observed. During the 24 month follow-up eight patients underwent subsequent surgery due to reasons unrelated to the implant material.
The observed clinical and radiological results are encouraging for a long-term survival of the ceramic femoral component. Therefore, ceramic implants could be a promising solution not only for patients with allergies against metallic implant materials, but also for the osteoarthritic knee joint. Long-term follow-up is necessary to draw conclusions regarding the superiority of the ceramic knee implants concerning in vivo wear and long-term survivorship.
PMCID: PMC3349949  PMID: 22582104
Ceramics; functional outcome; radiological outcome; total knee arthroplasty.
13.  Growth Factor-Induced Mobilization of Cardiac Progenitor Cells Reduces the Risk of Arrhythmias, in a Rat Model of Chronic Myocardial Infarction 
PLoS ONE  2011;6(3):e17750.
Heart repair by stem cell treatment may involve life-threatening arrhythmias. Cardiac progenitor cells (CPCs) appear best suited for reconstituting lost myocardium without posing arrhythmic risks, being commissioned towards cardiac phenotype. In this study we tested the hypothesis that mobilization of CPCs through locally delivered Hepatocyte Growth Factor and Insulin-Like Growth Factor-1 to heal chronic myocardial infarction (MI), lowers the proneness to arrhythmias. We used 133 adult male Wistar rats either with one-month old MI and treated with growth factors (GFs, n = 60) or vehicle (V, n = 55), or sham operated (n = 18). In selected groups of animals, prior to and two weeks after GF/V delivery, we evaluated stress-induced ventricular arrhythmias by telemetry-ECG, cardiac mechanics by echocardiography, and ventricular excitability, conduction velocity and refractoriness by epicardial multiple-lead recording. Invasive hemodynamic measurements were performed before sacrifice and eventually the hearts were subjected to anatomical, morphometric, immunohistochemical, and molecular biology analyses. When compared with untreated MI, GFs decreased stress-induced arrhythmias and concurrently prolonged the effective refractory period (ERP) without affecting neither the duration of ventricular repolarization, as suggested by measurements of QTc interval and mRNA levels for K-channel α-subunits Kv4.2 and Kv4.3, nor the dispersion of refractoriness. Further, markers of cardiomyocyte reactive hypertrophy, including mRNA levels for K-channel α-subunit Kv1.4 and β-subunit KChIP2, interstitial fibrosis and negative structural remodeling were significantly reduced in peri-infarcted/remote ventricular myocardium. Finally, analyses of BrdU incorporation and distribution of connexin43 and N-cadherin indicated that cytokines generated new vessels and electromechanically-connected myocytes and abolished the correlation of infarct size with deterioration of mechanical function. In conclusion, local injection of GFs ameliorates electromechanical competence in chronic MI. Reduced arrhythmogenesis is attributable to prolongation of ERP resulting from improved intercellular coupling via increased expression of connexin43, and attenuation of unfavorable remodeling.
PMCID: PMC3060871  PMID: 21445273
14.  Sensing Pressure Distribution on a Lower-Limb Exoskeleton Physical Human-Machine Interface 
Sensors (Basel, Switzerland)  2010;11(1):207-227.
A sensory apparatus to monitor pressure distribution on the physical human-robot interface of lower-limb exoskeletons is presented. We propose a distributed measure of the interaction pressure over the whole contact area between the user and the machine as an alternative measurement method of human-robot interaction. To obtain this measure, an array of newly-developed soft silicone pressure sensors is inserted between the limb and the mechanical interface that connects the robot to the user, in direct contact with the wearer’s skin. Compared to state-of-the-art measures, the advantage of this approach is that it allows for a distributed measure of the interaction pressure, which could be useful for the assessment of safety and comfort of human-robot interaction. This paper presents the new sensor and its characterization, and the development of an interaction measurement apparatus, which is applied to a lower-limb rehabilitation robot. The system is calibrated, and an example its use during a prototypical gait training task is presented.
PMCID: PMC3274101  PMID: 22346574
human-robot interaction; physical human-machine interface; distributed force sensor; lower-limb exoskeleton
15.  Solute removal during continuous renal replacement therapy in critically ill patients: convection versus diffusion 
Critical Care  2006;10(2):R67.
The best modality, for continuous renal replacement therapy (CRRT) is currently uncertain and it is poorly understood how transport of different solutes, whether convective or diffusive, changes over time.
We conducted a prospective cross over study in a cohort of critically ill patients, comparing small (urea and creatinine) and middle (β2 microglobulin) molecular weight solute clearance, filter lifespan and membrane performance over a period of 72 hours, during 15 continuous veno-venous dialysis (CVVHD) and 15 continuous veno-venous hemofiltration (CVVH)sessions. Both modalities were administered based on a prescription of 35 ml/kg/h and using polyacrylonitrile filters.
Median filter lifespan was significantly longer during CVVHD (37 hours, interquartile range (IQR) 19.5 to 72.5) than CVVH (19 hours, IQR 12.5 to 28) (p = 0.03). Median urea time weighted average (TWA) clearances were not significantly different during CVVH (31.6 ml/minute, IQR 23.2 to 38.9) and CVVHD (35.7 ml/minute, IQR 30.1 to 41.5) (p = 0.213). Similar results were found for creatinine: 38.1 ml/minute, IQR 28.5 to 39, and 35.6 ml/minute, IQR 26 to 43 (p = 0.917), respectively. Median β2m TWA clearance was higher during convective (16.3 ml/minute, IQR 10.9 to 23) than diffusive (6.27 ml/minute, IQR 1.6 to 14.9) therapy; nonetheless this difference did not reach statistical significance (p = 0.055). Median TWA adsorptive clearance of β2m appeared to have scarce impact on overall solute removal (0.012 ml/minute, IQR -0.09 to 0.1, during hemofiltration versus -0.016 ml/minute, IQR -0.08 to 0.1 during dialysis; p = 0.79). Analysis of clearance modification over time did not show significant modifications of urea, creatinine and β2m clearance in the first 48 hours during both treatments. In the CVVHD group, the only significant difference was found for β2m between 72 hours and baseline clearance.
Polyacrylonitrile filters during continuous hemofiltration and continuous hemodialysis delivered at 35 ml/kg/h are comparable in little and middle size solute removal. CVVHD appears to warrant longer CRRT sessions. The capacity of both modalities for removing such molecules is maintained up to 48 hours.
PMCID: PMC1550874  PMID: 16646985

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