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  • 1
    ISSN: 1432-0932
    Keywords: Key words Computer-assisted ¶surgery ; Cervical spine ; Posterior instrumentation ; In vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transarticular C1/2 screws are widely used in posterior cervical spine instrumentation. The use of pedicle screws in the cervical spine remains uncommon. Due to superior biomechanical stability compared to lateral mass screws, pedicle screws can be used, especially for patients with poor bone quality or defects in the anterior column. Nevertheless there are potential risks of iatrogenic damage to the spinal cord, nerve roots or the vertebral artery associated with both posterior cervical spine instrumentation techniques. Therefore, the aim of this study was to evaluate whether C1/2 transarticular screws as well as transpedicular screws in C3 and C4 can be applied safely and with high accuracy using a computer-assisted surgery (CAS) system. We used 13 human cadaver C0-C5 spine segments. We installed 1.4-mm Kirschner wires transarticular in C1/2, using a specially designed guide, and drilled 2.5-mm pedicle holes in C3 and C4 with the assistance of the CAS system. Hole positions were evaluated by palpation, CT and dissection. Forty-eight (92%) of the 52 drilled pedicles were correctly positioned after palpation, imaging and dissection. The vertebral artery was not injured in any specimen. All of the 26 C1/2 Kirschner wires were placed properly after imaging and dissection evaluations. No injury to vascular or bony structures was observed. C1/2 transarticular screws as well as transpedicular screws in the cervical spine can be applied safely and with high accuracy using a CAS system in vitro. Therefore, this technique may be used in a clinical setting, as it offers improved accuracy and reduced radiation dose for the patient and the medical staff. Nevertheless, users should take note of known sources of possible faults causing inaccuracies in order to prevent iatrogenic damage. Small pedicles, with a diameter of less than 4.0 mm, may not be suitable for pedicle screws.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0932
    Keywords: Key words Posterior instrumentation ; Occipito-cervical spine ; Biomechanical testing, in vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Posterior instrumentation of the occipito-cervical spine has become an established procedure in a variety of indications. The use of rod-screw systems improved posterior instrumentation as it allows optimal screw positioning adapted to the individual anatomic situation. However, there are still some drawbacks concerning the different implant designs. Therefore, a new modular rod-screw implant system has been developed to overcome some of the drawbacks of established systems. The aim of this study was to evaluate whether posterior internal fixation of the occipito-cervical spine with the new implant system improves primary biomechanical stability. Three different internal fixation systems were compared in this study: the CerviFix System, the Olerud Cervical Rod Spinal System and the newly developed Neon Occipito Cervical System. Eight human cervical spine C0/C5 specimens were instrumented from C0 to C4 with occipital fixation, transarticular screws in C1/C2 and lateral mass or pedicle screws in C3 and C4. The specimens were tested in flexion/extension, axial rotation, and lateral bending using pure moments of ± 2.5 Nm without axial preload. After testing the intact spine, the different instrumentations were tested after destabilising C0/C2 and C3/C4. Primary stability was significantly increased, in all load cases, with the new modular implant system compared to the other implant systems. Pedicle screw instrumentation tended to be more stable compared to lateral mass screws; nevertheless, significant differences were observed only for lateral bending. As the experimental design precluded any cyclic testing, the data represent only the primary stability of the implants. In summary, this study showed that posterior instrumentation of the cervical spine using the new Neon Occipito Cervical System improves primary biomechanical stability compared to the CerviFix System and the Olerud Cervical Rod Spinal System.
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  • 3
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The main aim of the present project is to study the feasibility of using different trophic organisms for evaluating the toxicity of dredged sediments arising in Hong Kong. A total of eight sediment samples (duplicate samples collected from four selected sites: Kowloon Bay, Tsing Yi, Chek Lap Kok, and Double Haven) of Hong Kong coastal waters were analyzed for the total concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, total organic carbon, acid volatile sulfides, simultaneously extracted metals, redox potential, and 12 organic micropollutants. The sediment elutriates were also analysed for the various metal concentrations, as well as contents of ammonia-N, nitrate, total sulfide, sulfate, and total organic carbon. Elutriate Sediment Toxicity Tests (ESTT) were also conducted, using two microalgae (Skeletonema costatum, a diatom and Dunaliella tertiolecta, a flagellate), juvenile shrimp (Metapenaeus ensis) and juvenile fish (Trachinotus obtaus). Two commercially available tests using bacteria (Microtox Test and Toxi-Chromotest) also were employed to test both the solid phase and elutriates of the sediments. The results of Microtox test on the solid phase, and bioassay tests using diatom on the sediment elutriate, especially the former, were correlated significantly (p 〈 0.05) with a number of physico-chemical properties of sediments and elutriates. It is recommended that a combination of a liquid-phase bioassay using diatom and a solid-phase bioassay using Microtox test should be used for screening a large number of sediment samples. However, the presence of ammonia in the sediments containing a high content of organic matter seemed to interfere the detection of contamination impacts.
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry 18 (1926), S. 72-73 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry 23 (1931), S. 323-325 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial and engineering chemistry 2 (1930), S. 382-384 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial and engineering chemistry 6 (1934), S. 426-428 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0942-0940
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Two cerebral angioblastomas which were encountered among 60 cerebellar angioblastomas caused us to engage in a study of the literature, the clinical features and the pathology of these very rare tumours. Their occurrence can no longer be doubted even though this contradicts the classical works ofLindau and ofCushing. In this connection, special significance attaches to the case associated with a pureLindaus, syndrome. It is remarkable that there were five children among the 23 verified and well documented cases. In contrast, cerebellar angioblastomas in children are incomparably much rarer. The tumour can develop in all regions of the brain, so that frontal, occipital, and temporal lobes may be affected. Usually the same general characteristics as those which are recognized with the cerebellar angioblastomas apply—e.g. the preponderance of males, the lesion is benign and has fine tissue variations. It is especially important to differentiate these lesions from the angioblastic meningiomas because they are common supratentorially. Not all authors differentiate these two tumours. However, morphological and histogenetic considerations have led the majority of authors, up to now, to a dualistic position concerning this question.
    Abstract: Riassunto L'osservazione di due angioblastomi cerebrali contro 60 angioblastomi cerebellari é stato il motivo di una ricerca nella letteratura sulla clinica e sulla patologia di questi tumori assai rari del sistema nervoso centrale. Sulla loro comparsa non si possono avere dubbi che contrastino quanto scritto originariamente da Lindau e Cushing. Particolare intéresse suscitano i casi che appaiono affetti da vero e proprio morbo di Lindau. E' pure degno di nota il fatto che dei 23 casi accertati, ossia accettabili, il tumore si é sviluppato cinque volte nell'infanzia. L'angioblastoma cerebellare dell'infanzia é al contraio molto più raro. Il tumore può sorgere in regioni cerebrali intere preferibilmente dove hanno sede i lembi frontale, occipitale e temporale. Per il resto valgono le stesse caratteristiche generali che sono note per l'angioblastoma cerebellare, con particolare frequenza nel sesso maschile, in forma benigna e con varianti di tessuto sottile. Particolarmente significativa risulta la limitazione dei meningiomi angioblastici, in quanto questi compaiono per la maggior parte in zona sopratentoriale. Non tutti gli autori fanno distinzione tra questi due tipi di tumori. Gli autori hanno sinora condotto i loro studi soprattutto sulla parte morfologica e istogenetica, gingendo però ad una visione dualistica del problema.
    Notes: Zusammenfassung Die Beobachtung von zwei Großhirnangioblastomen war Veranlassung, sich mit der Literatur, der Klinik und der Pathologie dieser sehr seltenen Tumoren zu beschäftigen. An ihrem Vorkommen kann im Gegensatz zu den Ansichten vonLindau undCushing nicht mehr gezweifelt werden. Besondere Beweiskraft erlangten die im Rahmen einer echtenLindau-Krankheit vorkommenden Fälle. Bemerkenswert ist, daß sich unter den 23 gesicherten bzw. akzeptablen Fällen (21 Fälle aus der Literatur) der Tumor fünfmal im Kindesalter entwickelte. Kleinhirnangioblastome im Kindesalter sind dagegen ungleich viel seltener. Der Tumor kann in sämtlichen Hirnregionen entstehen, wobei Frontal-, Occipital- und Temporallappen bevorzugter Sitz sind. Im übrigen gelten die gleichen allgemeinen Charakteristika, die für die Kleinhirnangioblastome bekannt sind, insbesondere Häufung beim männlichen Geschlecht und Gutartigkeit. Besondere Bedeutung erlangt die Abgrenzung von den angioblastischen Meningeomen, da diese meist supratentoriell sitzen. Nicht alle Autoren unterscheiden zwischen diesen beiden Tumorarten. Morphologische und histogenetische Überlegungen führten die Mehrzahl der Autoren bisher aber zu einem dualistischen Standpunkt in dieser Frage.
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  • 9
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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