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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cytogenetic analysis of a human embryonal rhabdomyosarcoma revealed a near-diploid karyotype with structural chromosome aberrations not involving the typical rearrangements of rhabdomyosarcomas, plus a large number of double minutes. Comparative genomic hybridization revealed a previously undescribed site of DNA amplification on the short arm of chromosome 1 (band 1p32-33).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European spine journal 9 (2000), S. 571-576 
    ISSN: 1432-0932
    Keywords: Key words Spinal fusion ; Implants ; Biomechanics ; Computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A high rate of pseudarthrosis and a high overall rate of implant migration requiring surgical revision has been reported following posterior lumbar interbody fusion using BAK threaded cages. The high rate of both pseudarthrosis and implant migration may be due to poor fixation of the implant. The purpose of this study was to analyse the motion of threaded cages in posterior lumbar interbody fusion. Six cadaveric human lumbar spine segments (three L2/3 and three L4/5 segments) were prepared for biomechanical testing. The segments were tested, without preload, under forces of axial compression (600 N), torsion (25 Nm) and shearing force (250 N). The tests were performed first with the segments in an intact state, and subsequently following instrumented stabilisation with two BAK cages via a posterior approach. These results were compared with those of a finite element model simulating the effects of identical forces on the segments with constructs. As the results were comparable, the finite element model was used for analysing the motion of BAK cages within the disc space. Motion of the implants was not seen in compression. In torsion, a rolling motion was noted, with a range of motion of 10.6° around the central axis of the implant when left/right torsion (25 Nm) was applied. The way the implants move within the segment may be due to their special shape: the thread of the implants can not prevent the BAK cages rolling within the disc space.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0932
    Keywords: Key words Spine ; Spine ; bone ; plates ; Spine ; screws ; Spine ; biomechanics ; Spine ; implant ; testing ; Spine ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this combined study was to evaluate the stability and safety of a new monocortical screw-plate system for anterior cervical fusion and plating (ACFP) according to Caspar in comparison with classical bicortical fixation. In the biomechanical part of the study two groups, each comprising six fresh human cadaveric spines (C4–C7), matched for bone mineral density, additionally resulting in almost the same mean age, were used. Range of motion and neutral zone were analyzed in flexion-extension, rotation (left, right) and lateral bending (left, right) using pure moments of ± 2.5 Nm for each specimen in the intact state, after discectomy at C5/6 and after discectomy at C 5/6 followed by bone grafting plus plating (Caspar plates), with either monocortical or bicortical screws. For all three motion planes, no significant difference could be found between the new monocortical and the bicortical fixation techniques. The clinical part of the study was performed as a prospective study on 30 patients suffering from symptomatic degenerative cervical disc disease in one segment. At the latest follow-up, no hardware- or graft-related complications were seen in any of the patients. Following these findings monocortical screw fixation can be recommended for the majority of anterior cervical fusion and plating procedures in degenerative disease, making the procedure quicker, easier, and safer. Bicortical screw fixation still has specific indications for multilevel stabilization, poor bone quality (osteoporosis, rheumatoid disease – as bicortical oversized rescue screw), unstable spines (trauma, tumour) and in particular for the realignment of kyphotic deformities (restoration of the normal lordotic curve). Due to the design of the study the results apply only to surgical treatment of monosegmental degenerative disc disease at the time.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Child's nervous system 14 (1998), S. 263-270 
    ISSN: 1433-0350
    Keywords: Key words Ependyma ; Hydrocephalus ; Congenital disease model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract H-Tx rats produce congenitally hydrocephalic offspring with varying severity of the condition. We used moderately hydrocephalic rats without evident clinical signs of hydrocephalus and normal controls from the same stock when they were at least 1.5 years old. Macroscopic anatomy was studied by MRI and in fixed brain slices and the ultrastructure of the ependyma, with REM. Apart from markedly stretched areas, where the ependyma was totally destroyed and subependymal structures directly exposed to the CSF, the density of ependymal microvilli and of tufts of cilia was reduced in proportion to the ventricular distension of a given area. A supraependymal “network”– never seen before in acute hydrocephalus – was found, whose purpose is probably to prevent further ventricular enlargement. We conclude that even in arrested hydrocephalus the ependymal sequelae of hydrocephalus are similar to those of the acute stage, illustrating the extremely limited potenctial for recovery, but the organism seems nevertheless to react with an internal stabilization of the ventricular system.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Child's nervous system 16 (2000), S. 451-456 
    ISSN: 1433-0350
    Keywords: Keywords Intracranial pressure ; CSF dynamics ; Infusion test ; Rat ; H-Tx rat ; Outflow resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Although the hydrocephalic H-Tx rat is a widely used model, data on the cerebrospinal fluid (CSF) dynamics in hydrocephalic rats are rare or – as the pressure volume index (PVI) – not available. We used hydrocephalic and nonhydrocephalic H-Tx rats, a stock with a high percentage of inherited hydrocephalus, for the evaluation of such data. In addition, a new, simple mathematical algorithm (”dynamic infusion test”), which has not formerly been used in animal experiments, was used as a pathophysiological model of CSF dynamics. Compared with classical methods for evaluation of these data, the dynamic infusion test gives a deeper insight into the relation between ICP and CSF dynamics. It was found that the resistance to outflow (ROF) in hydrocephalic rats was at least twice that in nonhydrocephalic rats. The PVI measured was similar in hydrocephalic and nonhydrocephalic animals, but clearly higher than the values reported in the literature. This may be attributable to the fact that the classically used bolus test, in contrast to the ”dynamic infusion test”, is representative only for the CSF compartment which is directly exposed to the bolus application.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Der Ophthalmologe 95 (1998), S. 28-32 
    ISSN: 1433-0423
    Keywords: Key words P-VEP • Pituitary • Adenoma • Electrophysiology ; Schlüsselwörter Muster-VEP • Hypophyse • Adenom • Elektrophysiologie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Fragestellung: Hypophysenadenome sind Tumoren der Sellaregion, die zu einer Kompression des Chiasma opticum führen können. Augenärztliche Untersuchungen stellen somit einen wichtigen Bestandteil der perioperativen Betreuung dieser Patienten dar. Patienten und Methode: Neben den klassisch ophthalmologischen Untersuchungsmethoden des bestkorrigierten Fernvisus und der Gesichtsfelduntersuchung verwandten wir die elektrophysiologische Methode der Muster-visuell evozierten Potentiale (M-VEP), um den perioperativen Verlauf nach durchgeführter transphenoidaler Resektion kontrollieren zu können. Ergebnisse: Die N75–P100-Amplitude des M-VEP erwies sich als sensitivster Marker zum Nachweis einer postoperativen Erholung. Es kommt nach durchgeführter Operation zu einem signifikanten Anstieg dieser Amplitude, wobei die P100-Latenzzeit sowie der Fernvisus und der Gesichtsfeldbefund keine signifikante Änderung zeigen. Schlußfolgerung: Das Muster-VEP stellt eine wichtige Ergänzung zur Verlaufskontrolle bei Erkrankungen mit der Gefahr der Optikuskompression dar.
    Notes: Background: Pituitary tumors are adenomas of a region of the sella turcica which can produce compression of the anterior visual pathway. Patients and methods: Besides clinical signs of visual improvement such as enhanced visual acuity and visual field, the use of electroophthalmological methods can help monitor patients after neurosurgery. Results: The N75 P100 amplitude of the p-VEP has proven to be the most sensitive marker for measuring-improvements after surgery. This amplitude significantly increased, whereas latency time, visual acuity and visual field showed no statistically significant changes after surgery. Conclusions: The p-VEP is an important tool in treating patients with compression of the visual pathway.
    Type of Medium: Electronic Resource
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