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Muller K.,University of Leipzig | Diez B.,FLENI Institute for Neurological Research | Muggeri A.,FLENI Institute for Neurological Research | Pietsch T.,University of Bonn | And 6 more authors.
Strahlentherapie und Onkologie | Year: 2013

Background: Intracranial peripheral primitive neuroectodermal tumors (P-PNET) are extremely rare. They can be easily misdiagnosed as central nervous system primitive neuroectodermal tumors (CNS-PNET) or meningiomas. Little is known about the optimal treatment and prognosis of these tumors. Patients and methods: We evaluated the treatment and outcome of 17 patients with intracranial, nonmetastatic, genetically confirmed P-PNET. Three patients were treated at our institutions. Thirteen other cases providing sufficient treatment and follow-up information were extracted from the literature. Results: The median age at diagnosis was 17 years. All patients underwent initial surgery. Complete resection was achieved in 9 of the 17 cases (53 %). Combined adjuvant treatment consisting of radiotherapy (focal, n = 10; craniospinal, n = 1) and chemotherapy was administered to 11 of the 17 patients (59 %). The median follow-up time was 1.4 years. In 8 of the 17 patients (47 %), the disease progressed; 4 of the 17 patients (24 %) died. The 2-year progression-free and overall survival rates were 64 % and 76 %, respectively. Conclusion: The differential diagnosis for intracranial, meningeal-based, small, round-cell tumors should include P-PNET. It is highly probable that complete resection has a positive impact on survival - as previously reported for extracranial P-PNET - but this cannot be shown by our data. Intensive adjuvant treatment consisting of radiotherapy and chemotherapy seems to be essential. A statistically grounded recommendation for the appropriate target volume and radiation dose is not yet possible. However, in most case reports of primary intracranial P-PNET published to date, patients were treated with focal irradiation. The optimal chemotherapy regimen has yet to be established, with both the Ewing tumor and CNS-PNET protocols being promising candidates for effective treatment. © 2013 Urban & Vogel. Zusammenfassung: Hintergrund: Intrakranielle periphere primitive neuroektodermale Tumoren (P-PNET) sind äußerst selten. Sie können leicht mit primitiven neuroektodermalen Tumoren des zentralen Nervensystems (ZNS-PNET) oder Meningeomen verwechselt werden. Bisher weiß man nur wenig über ihre optimale Behandlung und ihre Prognose. Material und Methoden: Wir untersuchten die Behandlung und das Überleben von 17 Patienten mit genetisch gesicherter Diagnose eines intrakraniellen, nichtmetastasierten, peripheren primitiven neuroektodermalen Tumors. Insgesamt wurden 3 Patienten in unseren Einrichtungen behandelt. Weitere 13 Fälle, die ausreichende Informationen über Behandlung und weiteren Krankheitsverlauf aufwiesen, wurden aus der Literatur extrahiert. Ergebnisse: Das mediane Alter bei Diagnosestellung lag bei 17 Jahren. Alle Patienten wurden zunächst operiert. Eine komplette Resektion wurde bei 9 von 17 Patienten (53 %) erreicht. Eine adjuvante Therapie wurde bei 11 von 17 Patienten (59 %) durchgeführt. Sie bestand jeweils aus einer Strahlentherapie (10-mal fokal, 1-mal gesamte Neuroachse) und Chemotherapie. Die mediane Nachbeobachtungszeit betrug 1,4 Jahre. Bei 8 von 17 Patienten (47 %) schritt die Erkrankung fort, 4 von 17 Patienten (24 %) verstarben schließlich. Zwei Jahre nach Diagnosestellung betrug das progressionsfreie Überleben 64 %, das Gesamtüberleben 76 %. Schlussfolgerungen: Die Differentialdiagnosen für intrakranielle, meningeale klein- und rundzellige Tumore sollten P-PNET berücksichtigen. Ein positiver Einfluss einer Komplettresektion auf das Überleben - wie zuvor für extrakranielle P-PNET nachgewiesen - ist sehr wahrscheinlich, kann aber nicht mit unseren Daten belegt werden. Eine intensive adjuvante Therapie, bestehend aus Strahlentherapie und Chemotherapie, scheint von entscheidender Bedeutung zu sein. Eine statistisch fundierte Empfehlung für Zielvolumina und Dosierung der Bestrahlung ist noch nicht möglich. Die Mehrzahl der bisher publizierten Fälle primär intrakranieller P-PNET wurde nur fokal bestrahlt. Die optimale Chemotherapie ist noch unbekannt. Sowohl Ewing-Tumor- als auch CNS-PNET-Protokolle sind vielversprechende Kandidaten. © 2013 Urban & Vogel.

Ravera E.P.,National University of Entre Rios | Ravera E.P.,National Council of Scientific and Technical Research | Crespo M.J.,FLENI Institute for Neurological Research | Braidot A.A.A.,National University of Entre Rios
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2014

Clinical gait analysis provides great contributions to the understanding of gait patterns. However, a complete distribution of muscle forces throughout the gait cycle is a current challenge for many researchers. Two techniques are often used to estimate muscle forces: inverse dynamics with static optimization and computer muscle control that uses forward dynamics to minimize tracking. The first method often involves limitations due to changing muscle dynamics and possible signal artefacts that depend on day-to-day variation in the position of electromyographic (EMG) electrodes. Nevertheless, in clinical gait analysis, the method of inverse dynamics is a fundamental and commonly used computational procedure to calculate the force and torque reactions at various body joints. Our aim was to develop a generic musculoskeletal model that could be able to be applied in the clinical setting. The musculoskeletal model of the lower limb presents a simulation for the EMG data to address the common limitations of these techniques. This model presents a new point of view from the inverse dynamics used on clinical gait analysis, including the EMG information, and shows a similar performance to another model available in the OpenSim software. The main problem of these methods to achieve a correct muscle coordination is the lack of complete EMG data for all muscles modelled. We present a technique that simulates the EMG activity and presents a good correlation with the muscle forces throughout the gait cycle. Also, this method showed great similarities whit the real EMG data recorded from the subjects doing the same movement. © 2014 Taylor & Francis

Fliger C.G.,National University of Entre Rios | Crespo M.J.,FLENI Institute for Neurological Research | Braidot A.A.,National University of Entre Rios | Ravera E.P.,National University of Entre Rios | Ravera E.P.,CONICET
Journal of Physics: Conference Series | Year: 2016

Clinical gait analysis provides great contributions to the understanding of gait disorders and also provides a mean for a more comprehensive treatment plan. However, direct measures of muscle forces are difficult to obtain in clinical settings because it generally requires invasive techniques. Techniques of musculoskeletal modeling have been used for several decades to improve the benefits of clinical gait analysis, but many of the previous studies were focused on analyzing separately the muscle forces distribution of children or adult subjects with only one condition of walking speed. For these reason, the present study aims to enhance the current literature by describing the age and speed gait effects on muscle forces during walking. We used a musculoskeletal model with 23 degrees of freedom and 92 musculotendon actuators to represent 76 muscles in the lower extremities and torso. The computed muscle control algorithm was used to estimate the muscle forces from the kinematics and to adjust the model obtained in the residual reduction algorithm. We find that hamstrings has an important peak in the mid-stance phase in the adult group but this peak disappears in the children group with the same walking speed condition. Furthermore, the rectus femoris presents an increase in the muscle force during the pre- and mid-swing in concordance with the increment in the walking speed of subjects. This behavior could be associated with the role that the rectus femoris has in the acceleration of the knee joint. Finally, we show that the soleus is the muscle that perform the major force throughout the gait cycle regardless of age and walking speed.

Ravera E.P.,National University of Entre Rios | Crespo M.J.,FLENI Institute for Neurological Research | Catalfamo P.A.,National University of Entre Rios | Braidot A.A.,National University of Entre Rios
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC'10 | Year: 2010

Crouch gait is the most common motion abnormality in children with cerebral palsy (CP). This paper presents a new biomechanical model based on a simple rescaling and adjustment to CP patients who develop crouch gait by subject-specific anthropometric data. The model estimates the length of hamstrings, as the istance between the origin and insertion of the muscle, and the velocity of shortening of hamstrings by the first derivative of the length with respect to time. This model has the potential to increase the benefits of three-dimensional biomechanical models as it can discriminate between short, spastic or normal hamstrings. The main advantage of this model in clinical use is that it does not require costly magnetic resonance imaging. © 2010 IEEE.

Ravera E.P.,National University of Entre Rios | Ravera E.P.,CONICET | Crespo M.J.,FLENI Institute for Neurological Research | Guarnieri F.A.,National University of Entre Rios | And 2 more authors.
IFMBE Proceedings | Year: 2015

Stress fractures are one of the most common and potentially serious injuries. About 30% of people with a hip fracture will die in the following year, and many more will experience significant functional loss. In order to investigate the mechanics of the musculoskeletal tissues, finite element method act as a complementary approach to in vivo and in vitro studies. So a correct interpretation as well as assessing the sensitivity of models and degree of its validation, become vital. The aim of the present study is therefore to develop and evaluate a finite element model of hip based in CT image. To achieve a simulation of the stress that affect the hip in walking, a rotation of the hip joint center and load compression were prescribed. The first one represented the flexion-extention hip joint, while the second one the vertical net force knee joint. The final FE model as result of convergence study consist of ~137.000 tetrahedral elements. Sensitivity values for the models suggests that FE predicted stress were not very sensitive to changes in the material properties assumed. Using a physiological load our model shows the von Mises stress ranged on 0-12 MPa during walking. Maximum peak of stress happens in sacroiliac joint in the anteromedial area as response to the load weight around to 10% of the gait cycle, however this peak moves to posterior-lateral zone when the hip joint is between 50-60% of the gait cycle. © Springer International Publishing Switzerland 2015

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