147 research outputs found
From kinetic models to hydrodynamics: some novel results
No full textFrom Kinetic Models to Hydrodynamics serves as an introduction to the asymptotic methods necessary to obtain hydrodynamic equations from a fundamental description using kinetic theory models and the Boltzmann equation. The work is a survey of an active research area, which aims to bridge time and length scales from the particle-like description inherent in Boltzmann equation theory to a fully established “continuum” approach typical of macroscopic laws of physics.The author sheds light on a new method—using invariant manifolds—which addresses a functional equation for the nonequilibrium single-particle distribution function. This method allows one to find exact and thermodynamically consistent expressions for: hydrodynamic modes; transport coefficient expressions for hydrodynamic modes; and transport coefficients of a fluid beyond the traditional hydrodynamic limit. The invariant manifold method paves the way to establish a needed bridge between Boltzmann equation theory and a particle-based theory of hydrodynamics. Finally, the author explores the ambitious and longstanding task of obtaining hydrodynamic constitutive equations from their kinetic counterparts. The work is intended for specialists in kinetic theory—or more generally statistical mechanics—and will provide a bridge between a physical and mathematical approach to solve real-world problems.
Allograft-Prosthetic Composite in the Proximal Tibia After Bone Tumor Resection
No full textWe consider an allograft-prosthesis composite in the proximal tibia one of the better reconstructive options in this site because it combines the mechanical stability of a prosthesis with the biologic reconstruction of the extensor mechanism. We retrospectively reviewed 62 patients who had proximal tibia reconstructions with allograft-prosthesis composites to ascertain the complications and functional outcomes. By combining an allograft with a prosthesis, placing cement in the graft, and press-fitting the prosthesis in the tibial diaphysis, we obtained satisfactory Musculoskeletal Tumor Society scores in 90.4% of patients, with a 5-year survival rate (73.4%) comparable to that of reconstruction with a modular prosthesis. However, we observed high infection rates (24.2%) and rotation of the medial gastrocnemius seemed not to reduce this complication. For this reason, we do not recommend using this reconstructive technique in patients who will receive postoperative chemotherapy or in patients in whom a previous reconstructive method failed. We believe the ideal candidate is the young patient with a benign aggressive or malignant low-grade tumor who has not undergone previous surgery.
Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
Each author certifies that he or she has no commercial associations (e.g., consultancies, stock, ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article.
Each author certifies that his or her institution has approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research
Image-guided Cryotherapy for Musculoskeletal Tumors
No full textBackground: This article represents a review about the use of image-guided cryotherapy in the treatment of musculoskeletal tumor lesions. Cryotherapy is able to induce a lethal effect on cancer cells through direct and indirect mechanisms. In this manuscript, we combined our experience with that of other authors who have published on this topic in order to provide indications on when to use cryotherapy in musculoskeletal oncology.
Discussion: Image-Guided percutaneous cryotherapy is a therapeutic method now widely accepted in the treatment of patients with musculoskeletal tumors. It can be used both for palliative treatments of metastatic bone lesions and for the curative treatment of benign bone tumors such as osteoid osteoma or osteoblastoma. In the treatment of bone metastases, cryotherapy plays a major role in alleviating or resolving disease-related pain but it has also been demonstrated that it can have a role in local disease control. In recent years, the use of cryotherapy have also expanded for the treatment of both benign and malignant soft tissue tumors.
Conclusion: Percutaneous cryotherapy can be considered a safe and effective technique in the treatment of benign and malignant musculoskeletal tumors. Cryotherapy can be considered the first option in benign tumor lesions such as osteoid osteoma and a valid alternative to radiofrequency ablation. In the treatment of painful bone metastases, it must be considered secondarily to other standard treatments (radiotherapy, bisphosphonate therapy and chemotherapy) where they are no longer effective in controlling the disease or when they cannot be repeated (for example radiotherapy)
IL TRATTAMENTO CHIRURGICO DEI CORDOMI DEL SACRO: RISULTATI A LUNGO TERMINE
No full textIntroduzione: Il cordoma è un tumore a basso grado di ma-lignità che origina da residui della notocorda. Si sviluppa, per-tanto, principalmente nel rachide e nella base cranica. In genere l’evoluzione di questi tumori è molto lenta, possono recidivare localmente anche a distanza di anni e raramente metastatizzare. In rari casi possono dedifferenziarsi in sarcomi ad alto grado di malignità. Scopo del presente studio è di analizzare i fattori pro-gnostici per il controllo locale e sistemico della malattia.
Materiali e Metodi: Dal 1994 al 2015 sono stati operati 33 paziente affetti da cordoma del sacro, di cui 19 maschi e 14 femmine. L’età media è stata di 61 anni (43-80). In 24 pazienti è stata eseguita una resezione sopra S2. Nessun paziente è stato sotto-posto a radioterapia pre-operatoria. I margini chirurgici sono stati ampi in 17 casi, marginali in 14 ed intralesionali in 2.
Risultati: Ad un follow-up medio di 53 mesi (0-198), 19 pazienti risultano essere liberi da malattia, 6 liberi da malattia dopo tratta-mento di recidiva locale (5 casi), o metastasi (1 caso), 3 pazienti vivi con malattia, 4 pazienti sono morti per malattia ed 1 per altre cause. Sono stati riscontrati 9 casi di recidiva locale (27%) che sono state sottoposte ad intervento chirurgico, di cui 3 hanno inoltre eseguito carbon ion therapy dopo escissione. La sopravvivenza globale è stata dell’86% a 10 anni. Liberi da recidiva sono stati il 51% a 10 anni. L’analisi statistica ha confermato l’importanza dei margini chirurgici ampi per il controllo della malattia locale (p=0.0007). Nel caso di resezioni sopra S2 si è riscontrato una minor sopravvivenza e un aumentato rischio di recidiva.
Discussione: Il trattamento di prima scelta per la cura dei cordomi sacrali è la resezione chirurgica a margini oncologicamente adeguati con conseguenti deficit neurologici permanenti, più o meno invalidanti, a seconda del livello di resezione (sopra vs sot-to S2). La radioterapia convenzionale e la chemioterapia, infatti, sono inefficaci per il trattamento della malattia. Recentemente l’adroterapia è risultata efficace soprattutto per il trattamento del-le recidive locali.
Conclusioni: Il gold standard per il trattamento dei cordomi del sarcro è ad oggi la resezioni in blocco del tumore, tuttavia quando il livello di resezione è al di sopra di S2, bisogna prendere in considerazione anche la adronoterapia come alternativa alla chirurgia
Il Fantasma del Nolli. Roma, Ospedale san Giacomo
No full textNel 2008, la Regione Lazio all’interno delle misure anticrisi per il rispetto del patto di bilancio decide la chiusura, dismissione e cartolarizzazione dell’antico Ospedale San Giacomo, codice 476-480 della mappa del Nolli di Roma. L’ospedale, una delle più antiche istituzioni pubbliche romane, viene chiuso il 31 ottobre 2008. L’edificio viene inserito all’interno di un fondo immobiliare e destinato alla vendita. Fin qui sembra una delle tante operazioni di valorizzazione privata del patrimonio immobiliare pubblico. Pochi giorni prima però, presso l’Archivio di Stato di Roma viene ritrovato il testamento del Cardinale Antonio Maria Salviati, che aveva voluto la ristrutturazione del complesso sanitario nel XVI secolo: In Nomine Domini e per volere del potente prelato l’Ospedale San Giacomo, viene donato al Popolo Romano e l’edificio resterà pubblico a patto che rimanga destinato ad uso ospedaliero; in caso contrario gli eredi della famiglia ne rientreranno in possesso. Il ritrovamento del documento rende illegittima la procedura di alienazione da parte del governo regionale ultimo discendente delle antiche istituzioni del popolo romano in materia di sanità. Nonostante questo l’ospedale, perfettamente funzionante, viene chiuso; ma il complesso resta abbandonato, al centro del conflitto giudiziario tra l’amministrazione pubblica che ne difende la privatizzazione e i privati – i Salviati più le associazioni cittadine - che ne difendono l’uso pubblico. L’ospedale, antico spazio di ricovero e isolamento dei malati fino al XVIII secolo; poi tra i primi complessi sanitari romani ristrutturati secondo i principi illuministici dell’individuazione, disciplinamento, osservazione ed esame del paziente alla base delle forme di cura del novecento resta oggi una sorta di isolato fantasma al centro di Roma. Una sorta di buco nella mappa del Nolli, né poché nero della città privata, né spazio bianco degli spazi e delle istituzioni pubbliche
Hybrid Simulation and Planning Platform for Cryosurgery with Microsoft HoloLens
No full textCryosurgery is a technique of growing popularity involving tissue ablation under controlled freezing. Technological advancement of devices along with surgical technique improvements have turned cryosurgery from an experimental to an established option for treating several diseases. However, cryosurgery is still limited by inaccurate planning based primarily on 2D visualization of the patient’s preoperative images. Several works have been aimed at modelling cryoablation through heat transfer simulations; however, most software applications do not meet some key requirements for clinical routine use, such as high computational speed and user-friendliness. This work aims to develop an intuitive platform for anatomical understanding and pre-operative planning by integrating the information content of radiological images and cryoprobe specifications either in a 3D virtual environment (desktop application) or in a hybrid simulator, which exploits the potential of the 3D printing and augmented reality functionalities of Microsoft HoloLens. The proposed platform was preliminarily validated for the retrospective planning/simulation of two surgical cases. Results suggest that the platform is easy and quick to learn and could be used in clinical practice to improve anatomical understanding, to make surgical planning easier than the traditional method, and to strengthen the memorization of surgical planning
DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Return): a balloon-borne dust particle collector
No full textThe DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Retrieval) project is aimed at uncontaminated collection and retrieval of stratospheric solid aerosol particles, in the submicron/micron range, from the upper stratosphere. The approach implies: (1) in-situ particles collection; (2) sample recovering; and (3) laboratory analyses. The scientific aim is deriving the dust size distribution, the concentration, chemistry and mineralogy of the collected stratospheric aerosols. The main characteristics of the instrument are: (1) Capability of working autonomously during balloon flight at 30-40 km altitude, temperatures down to -80°C; (2) sampling at least 20 m3 of air to collect several hundreds of aerosol particles); (3) Samples storage and retrieval under controlled conditions. A detailed description of the experiment is reported her
Patients Specific Spine Simulators for Surgical Training and Rehearsal in Pedicle Screws Placement: A New Way for Surgical Education
No full textIn pedicle screws placement using a free-hand technique or a fluoroscopic guided technique the main difficulties are facing to the bone morphology (i.e in deformity cases) and it could be easily reproduced in a patient’s specific spine simulator (we can choose the case). The aim of this work is to evaluate the use of 3D printed patient- specific models (3D printing) not only as a surgical planning tool but also as a surgical training tool in spine surgery and in particular in pedicle screws placement. The manufacturing of patient-specific physical replica involves the elaboration of CT dataset and rapid prototyping techniques. . Five resident surgeons were involved in different training sessions on simulators. To evaluate the exact screws position we performed a CT evaluation of each instrumented simulators. Statistical analysis was conducted using SPSS software. A total of 120 pedicle screws were positioned, 90 screws were well-positioned and 30 screws were bad-positioned. There were a significant difference (p = 0.000008) between the bad-positioning screw rate of the “senior” resident (13/72) and those of “young” participants (17/48). Timeline analysis of pedicle instrumentation training showed the presence of a learning effect, with a lower error rate in the latest session (p=000001). We believe that the use of patient- specific surgical simulators, especially for those surgical tasks in which the complexity is mainly linked to the spine morphology (i.e. deformity), may represent a valid alternative to the use of cadavers that generally present a standard or otherwise poorly predictable anatomy
Parapharyngeal space tumors: a twenty-year single-center retrospective analysis on the effectiveness of transcervical and transoral approaches on local control and disease-specific survival
No full textIntroduction: To retrospectively analyzed our twenty-years single-center experience in the treatment of PPS tu-mors, focusing on the selection of surgical approach and the survival outcome.Methods: Tumors involving the PPS between January 2000 and February 2022 were retrospectively included. The surgical approach was dictated by the localization of the tumor, its dimensions, the relation to anatomic structures and its etiology.Results: 34 patients were included in the study. The median age was 50.5 yr, with a gender female prevalence. Most tumors were benign and non recurrent. 20 tumors were treated through lateral approach (transcervical or transcervical-transparotid), 11 through medial approach (transoral), and only 3 tumors were approached by multiple corridors. The 5 years disease free survival (DFS) was 78.8 % (CI 78-79.3 %).Conclusions: In our experience, the transcervical and transoral approaches can be considered the ideal surgical approach to manage tumors of PPS, especially in cases of benign neoplasms
One-step reconstruction with custom-made 3D-printed scapular prosthesis after partial or total scapulectomy
No full textEn bloc scapulectomy with covering muscles was historically considered the only procedure available for surgical treatment of bone and soft tissue tumors of the scapula. When possible, reconstruction with scapular allograft is the gold standard, and gives satisfactory functional, cosmetic, and oncological outcomes. While good results have recently been reported with 3D-printed prostheses for reconstruction of bone loss, there is little information available in the medical literature regarding scapula reconstruction with a 3D-printed prosthesis. Between 2016 and 2018, we performed four scapular resections (two total and two involving the superior 1/3) followed by reconstruction with a 3D-printed prosthesis made of a porous titanium alloy (Ti-6Al-4V, diameter between 100 and 400 mm), using computer-aided design (CAD) and patient-specific implants (PSI) with previously acquired CT-MR fusion images. At 2 years follow-up, the patients with partial scapulectomy had an MSTS score of 76%, no local or systemic recurrence, good clinical results and no pain. At 1 year 6 months follow-up, the patients with total scapulectomy had an MSTS score of 46%, no local or systemic recurrence, fair clinical results and no pain. Thus, custom-made 3D-printed prostheses appear to be valuable in orthopedic surgery. However, a larger cohort and longer-term analysis are needed to evaluate the scapular 3D-printed prosthesis as a reliable reconstruction technique
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