1,720,966 research outputs found
β-Chitin samples with similar microfibril arrangement change mechanical properties varying the degree of acetylation
No full textChitin is widespread in nature and is increasingly used in synthetic process for the production of new biomaterials. Chitin degree of acetylation, crystalline structure and microfibril arrangement differentiate chemical, physical and mechanical properties. Nevertheless, no information are available on the relationship between the mechanical properties and the degree of acetylation (DA) in chitin samples in which the microfibril arrangement does not change. Here, samples of β-chitin with decreasing DA, up to chitosan, were prepared using the squid pen of Loligo vulgaris. These samples were characterized by CP-MAS NMR spectroscopy, scanning electron microscopy, thermal analyses, synchrotron X-ray fiber diffraction and tensile tests. The results showed a similar microfibril arrangement decreasing the DA, except for the chitosan sample. The mechanical properties showed an increase of the maximum strain and a reduction of the maximum stress and Young's modulus, decreasing the DA. These changes, not linear with the DA, were related to structural changes at molecular structure level. The knowledge deriving from this study is of interest both for the understanding of the mechanical properties of chitinous biological samples, but also for the design and synthesis of new biomacromolecular materials
Advantages of customization of osseointegrated implants in transfemoral amputees: a comparative analysis of surgical planning
Full text linkBackground: Commercially available osseointegrated devices for transfemoral amputees are limited in size and thus fail to meet the significant anatomical variability in the femoral medullary canal. This study aimed to develop a customized osseointegrated stem to better accommodate a variety of femoral anatomies in transfemoral amputees than off-the-shelf stems. Customization is expected to enhance cortical bone preservation and increase the stem-bone contact area, which are critical for the long-term stability and success of implants. Methods: A customized stem (OsteoCustom) was designed based on the statistical shape variability of the medullary canal. The implantability of the OsteoCustom stem was tested via 70 computed tomography (CT) images of human femurs and compared to that of a commercial device (OFI-C) for two different resection levels. The evaluations included the volume of cortical bone removed and the percentage of stem-bone contact area for both resection levels. Statistical significance was analyzed using paired and unpaired t tests. Results: The OsteoCustom stem could be virtually implanted in all 70 femurs, while the OFI-C was unsuitable in 19 cases due to insufficient cortical thickness after implantation, further emphasizing its adaptability to varying anatomical conditions. The OsteoCustom stem preserved a greater volume of cortical bone than did the OFI-C. In fact, 42% less bone was removed at the proximal resection level (3.15 cm3 vs. 5.42 cm3, p ≤ 0.0001), and 33% less at the distal resection level (2.25 cm3 vs. 3.39 cm3, p = 0.003). The stem-bone contact area was also greater for the OsteoCustom stem, particularly at the distal resection level, showing a 20% increase in contact area (52.3% vs. 32.2%, p = 0.002) compared to that of the OFI-C. Conclusions: The OsteoCustom stem performed better than the commercial stem by preserving more cortical bone and achieving a greater stem-bone contact area, especially at distal resection levels where the shape of the medullary canal exhibits more inter-subject variability. Optimal fit in the distal region is of paramount importance for ensuring the stability of osseointegrated implants. This study highlights the potential benefits of customized osseointegrated stems in accommodating a broader range of femoral anatomies, with enhanced fit in the medullary canal.Background: Commercially available osseointegrated devices for transfemoral amputees are limited in size and thus fail to meet the significant anatomical variability in the femoral medullary canal. This study aimed to develop a customized osseointegrated stem to better accommodate a variety of femoral anatomies in transfemoral amputees than off-the-shelf stems. Customization is expected to enhance cortical bone preservation and increase the stem-bone contact area, which are critical for the long-term stability and success of implants. Methods: A customized stem (OsteoCustom) was designed based on the statistical shape variability of the medullary canal. The implantability of the OsteoCustom stem was tested via 70 computed tomography (CT) images of human femurs and compared to that of a commercial device (OFI-C) for two different resection levels. The evaluations included the volume of cortical bone removed and the percentage of stem-bone contact area for both resection levels. Statistical significance was analyzed using paired and unpaired t tests. Results: The OsteoCustom stem could be virtually implanted in all 70 femurs, while the OFI-C was unsuitable in 19 cases due to insufficient cortical thickness after implantation, further emphasizing its adaptability to varying anatomical conditions. The OsteoCustom stem preserved a greater volume of cortical bone than did the OFI-C. In fact, 42% less bone was removed at the proximal resection level (3.15 cm3 vs. 5.42 cm3, p ≤ 0.0001), and 33% less at the distal resection level (2.25 cm3 vs. 3.39 cm3, p = 0.003). The stem-bone contact area was also greater for the OsteoCustom stem, particularly at the distal resection level, showing a 20% increase in contact area (52.3% vs. 32.2%, p = 0.002) compared to that of the OFI-C. Conclusions: The OsteoCustom stem performed better than the commercial stem by preserving more cortical bone and achieving a greater stem–bone contact area, especially at distal resection levels where the shape of the medullary canal exhibits more inter-subject variability. Optimal fit in the distal region is of paramount importance for ensuring the stability of osseointegrated implants. This study highlights the potential benefits of customized osseointegrated stems in accommodating a broader range of femoral anatomies, with enhanced fit in the medullary canal
Sviluppo di un applicativo software per la pianificazione chirurgica di protesi osteointegrate transfemorali personalizzate costruite tramite stampa 3D
No full textLe protesi con invasatura imperversano nel mercato mondiale della protesica ancora al giorno d’oggi, tuttavia, lo studio di nuove soluzioni che sostituiscano le protesi con invasatura ha compiuto passi da gigante a partire da metà del secolo scorso, cioè dalla scoperta del concetto di osteointegrazione; il mercato ha perciò assistito all’avvento di protesi rivoluzionarie e uniche nel loro genere: gli impianti protesici osteointegrati. La trattazione offre una panoramica di quelli che sono i limiti di utilizzo delle protesi con invasatura, nonché una fotografia dello stato dell’arte dei pochi impianti protesici osteointegrati, principalmente transfemorali, disponibili sul mercato ed i rispettivi pregi e limiti. Lo scopo del lavoro svolto è stato quello di ideare un software di pianificazione chirurgica in ambiente Grasshopper (un plug-in di Rhinoceros) usufruibile dai chirurghi ortopedici in fase preliminare di studio di fattibilità e parametri di progettazione dell’impianto osteointegrato per pazienti con amputazioni transfemorali. Prima della fase di progettazione del software vera e propria, è stato necessario effettuare uno studio preliminare qualitativo tramite la piattaforma di programmazione Matlab©. I risultati ottenuti dal test pilota spalancano le porte a quello che viene chiamato approccio patient specific, soluzioni protesiche di impianti osteointegrati che si adattano alla fisionomia del distretto anatomico del paziente amputato e preservano il più possibile l’osso residuo sano, garantendo al contempo stabilità ed affidabilità dell’impianto stesso
Ausili per disabili
Full text linkopenEmbargo per motivi di segretezza e di proprietà dei risultati e informazioni di enti esterni o aziende private che hanno partecipato alla realizzazione del lavoro di ricerca relativo alla tes
Messa a punto di metodi per la caratterizzazione meccanica in vitro di segmenti ossei
No full textIn the last decade, the mechanical characterization of bone segments has been seen as a fundamental key to understanding how the distribution of physiological loads works on the bone in everyday life, and the resulting structural deformations. Therefore, characterization allows to obtain the main load directions and, consequently, to observe the structural lamellae of the bone disposal, in order to recreate a prosthesis using artificial materials that behave naturally.
This thesis will expose a modular system which provides the mechanical characterization of bone in vitro segment, with particular attention to vertebrae, as the current object of study and research in the lab where I did my thesis work.
The system will be able to acquire and process all the appropriately conditioned signals of interest for the test, through dedicated hardware and software architecture, with high speed and high reliability.
The aim of my thesis is to create a system that can be used as a versatile tool for experimentation and innovation for future tests of the mechanical characterization of biological components, allowing a quantitative and qualitative assessment of the deformation in analysis, regardless of anatomical regions of interest
Studio di fattibilità e progettazione di un impianto osteointegrato per amputazioni transtibiali
No full textLAUREA MAGISTRALELe protesi osteointegrate stanno diventando una nuova opzione per gli amputati di arti superiori e inferiori. Consistono in un impianto in leghe biocompatibili inserito nell’osso al quale viene collegata la protesi esterna del paziente. Viene di conseguenza eliminata l’invasatura e tutti i problemi che derivano dal suo utilizzo, aumentando però il rischio di infezione in quanto lo stoma, zona da cui fuoriesce l’impianto, resta aperto. Quasi tutti i dispositivi osteointegrati impiantabili attualmente utilizzati per gli amputati transtibiali, sono stati progettati per impianti transfemorali, i due distretti corporei presentano però morfologie molto diverse. In questo elaborato è stato sviluppato un nuovo dispositivo patient-matched realizzato in additive manufacturing (fixture) che si adatta perfettamente alla forma del canale midollare tibiale, il quale, specialmente nella zona prossimale, non ha una forma che favorisce l’osteointegrazione. Alla fixture è collegato un abutment, che permette al paziente di indossare la protesi esterna e di riportare la rima articolare della caviglia protesica ad un’altezza concorde a quella dell’arto controlaterale sano. L’estremità distale dell’abutment viene inserita in un dispositivo di sicurezza che permette di avere un sistema di aggancio/sgancio rapido della protesi esterna (minori tempi di vestizione) e di essere esso stesso il dispositivo di sicurezza per carichi torsionali. Sono stati dimensionati i due accoppiamenti (fixture/abutment e abutment/dispositivo di sicurezza) al fine di rendere il dispositivo resistente ai carichi a cui è comunemente soggetto nelle attività quotidiane, ma anche a quelli accidentali che potrebbero sopraggiungere, come ad esempio la caduta del paziente.Osseointegrated prostheses are emerging as a new option for individuals with upper and lower limb amputations. These consist in the placement of a biocompatible alloy implant into the bone, which serves as a connection point for the patient's external prosthesis. This innovative approach deletes the need for a traditional socket and the associated issues it can cause. However, it's important to note that there is an increased risk of infection due to the open stoma, the area where the implant emerges. Most currently used osseointegrated devices for transtibial amputations have been designed primarily for transfemoral implants, even though these two areas of the body have distinct morphologies. In this research paper, a new patient-specific device, created using additive manufacturing (the fixture), has been developed. This fixture perfectly conforms to the shape of the tibial medullary canal, particularly in the proximal region, where the bone's shape doesn't naturally promote osseointegration. An abutment is connected to the fixture, enabling the patient to attach their external prosthesis and align the prosthetic ankle joint with the height of their healthy contralateral limb. The distal end of the abutment is inserted into a safety device, which facilitates a quick coupling/release system for the external prosthesis. Additionally, this safety device serves as a safeguard against torsional loads. Both couplings (fixture/abutment and abutment/safety device) have been carefully sized to ensure the device can withstand the typical daily loads experienced by users, as well as any unforeseen accidents, such as a patient falling
Feasibility study for an osseointegrated prosthesis for transhumeral amputees
No full textOsseointegrated prostheses for patients with transhumeral amputation provide a direct
connection between the external prosthesis and the patient’s bone. However, there
are some problems that are still to be solved. One of the main problems is that not all patients are eligible for the
osseointegrated implantation. Commercially available
prostheses are produced in a restricted range of sizes. Therefore, they do not account for the
high anatomical variability of the medullary canal. A possible solution could be to consider
the anatomic variability of the medullary canal in developing a new prosthesis design.
The aim was to assess the feasibility of a transhumeral osseointegrated
prosthesis that would better match the variability of the humeral medullary canal. To this aim
a patent research was conducted. Moreover, an
experimental assessment of humeral anatomical variability was carried out. This was followed
by the application of SSM to identify the principal modes of variation and
to determine the sample size required for convergence in shape analysis. The medullary canals of 64 humeri were segmented from CT images and the
resulting 3D meshes were registered to align the structures. Each mesh was then sliced
at 19 lengths to simulate different amputation levels. The resulting meshes were
subsequently analysed through SSM and PCA to identify and quantify the shape variations of the canals. Finally, the number of instances
necessary to obtain accurate results was evaluated through a convergence analysis.
Results showed how at most 4 PCs are necessary to explain 90% of the shape variance of each
canal segment. The 64 instances available resulted sufficient for all the PCs and canal segment
evaluated, with the only exception of the first PC of the segment of 80% of residual canal length.
The results highlight relevant shape variation within humeral medullary canal. This supports
the idea of adapting the geometry of osseointegrated prostheses to these shape variations
- …
