Stoß- und schlagbelastung des menschlichen schienbeins im drehversuch

Zusammenfassung Die menschliche Tibia wurde bei mittlerer und schneller Drehgeschwindigkeit bis zum Bruch des Knochens belastet. Die Ergebnisse der Zehntel- und Hundertstelsekundenfraktur werden mit denen bei langsamer Drehung (Sekundenfraktur) verglichen.Beim Drehstoß ( = 236°/sec) steigen die Frakturdrehmomente durchschnittlich um 17%, beim Drehschlag ( = 597°/sec) um 25% gegenüber der langsamen Drehung ( = 6°/sec). Die Elastizitätsgrenze, die die Verletzungsgrenze der Tibia darstellt, zeigt jeweils einen noch etwas höheren Anstieg. Die menschliche Tibia ist also gegenüber Stößen und Schlägen weniger empfindlich als gegenüber langsamen Belastungen, bei Drehung noch mehr als bei Biegung. Der Durchmesser des Schienbeinkopfes korrelierte im Vergleich zu zahlreichen weiteren Parametern am besten mit den Bruchwerten. Energieaufnahme, Form, Lage und Länge der Fraktur änderten sich auch bei schneller Drehung nicht, der Frakturdrehwinkel nahm bei Schlagbeanspruchung leicht ab.Für die Verletzungsprophylaxe beim alpinen Skilauf sind bei kurzer Krafteinwirkung die Trägheitsmomente des gesamten Beines zu berücksichtigen und erhöhen die o. g. Werte der Verletzungsgrenze erheblich.Aus den Ergebnissen werden Folgerungen für den Schutz vor typischen Skiverletzungen durch die Skibindung abgeleitet und können dazu beitragen, die passive Sicherheit beim Skilauf weiter zu erhöhen.

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Hit and blow endurance of the human tibia in torsion testing

Summary Whole human tibiae were fractured with rapid loading rates of tenths and hundreds of a second for torsional fracture. Results were compared with data of experiments in slow loading during seconds.Loading time of 100 msec ( = 236°/s) increased the mean maximum torque of 17%, loading time of 10–40 msec ( = 597°/s) showed increase of 25%. In dynamic twisting the applied torque at the elasticity threshold, which represents the injury threshold of the tibia, has relatively higher values than the data at failure. The best correlation to the maximum torque exists at the frontal diameter of the tibia head.In dynamic twisting energies, site, figuration and length of fracture did not differ from those in quasistatic twisting procedures. With loading time of hundreds of a second the angle of fracture diminished.To prevent injuries in alpine skiing it is important to consider inertial effects of the whole leg in dynamic twisting. These effects raise the values of injury threshold distinctly. Practical conclusions are drawn from the results to get better passive safety in alpine skiing by perfecting release bindings.

     

Inhaled environmental combustion particles cause myocardial injury in the Wistar Kyoto rat.

Epidemiologists have associated particulate matter (PM) air pollution with cardiovascular morbidity and premature mortality worldwide. However, experimental evidence demonstrating causality and pathogenesis of particulate matter (PM)-induced cardiovascular damage has been insufficient. We hypothesized that protracted, repeated inhalation by rats of oil combustion-derived, fugitive emission PM (EPM), similar in metal composition to selected sources of urban air PM, causes exposure duration- and dose-dependent myocardial injury in susceptible rat strains. Zinc was the only primary water-leachable/bioavailable element of this EPM. Male Sprague-Dawley (SD), Wistar Kyoto (WKY), and spontaneously hypertensive (SH) rats were exposed nose-only to EPM (2, 5, or 10 mg/m(3), 6 h/day for 4 consecutive days or 10 mg/m(3), 6 h/day, 1 day/week for 4 or 16 consecutive weeks). Two days following the last EPM exposure, cardiac and pulmonary tissues were examined histologically. The results showed that particle-laden alveolar macrophages were the only pulmonary lesions observed in all three rat strains. However, WKY rats exposed to EPM (10 mg/m(3) 6 h/day, 1 day/week for 16 weeks) demonstrated cardiac lesions with inflammation and degeneration. To further characterize the nature of EPM-associated lesions, more rigorous histopathological and histochemical techniques were employed for WKY and SD rats. We examined the hearts for myocardial degeneration, inflammation, fibrosis, calcium deposits, apoptosis, and the presence of mast cells. Decreased numbers of granulated mast cells, and multifocal myocardial degeneration, chronic-active inflammation, and fibrosis were present in 5 of 6 WKY rats exposed to EPM for 16 weeks. None of these lesions were present in WKY exposed to clean air. EPM-related cardiac lesions were indistinguishable from air-exposed controls in SD and SH rats. This study demonstrates that long-term inhalation exposures to environmentally relevant PM containing bioavailable zinc can cause myocardial injury in sensitive rats. These findings provide supportive evidence for the epidemiological associations of cardiovascular morbidity and ambient PM.     

Noninvasive Tracking of Patient's Head Movements During Computer-Assisted Intranasal Microscopic Surgery

A noninvasive system designed for patient tracking during image-guided intranasal sinus surgery is described. It is based on optical digitizing with a custom-made registration and reference system, locatable surgical instruments, and a self-localizing operating microscope. Experimental and clinical results reveal a high degree of accuracy for the system. A mean spatial error of 0.82 ± 0.31 mm was determined for repositioning of the reference system in a plastic model of the skull. For the positioning of the microscope, a mean error of 2.3 ± 0.83 mm was calculated. Measurements of repositioning accuracy in 24 patients who received surgery for various sinus diseases had a mean spatial error of 1.56 ± 0.76 mm. The 95% error interval for locating intranasal structures using the surgical instrument was 2.05 mm, and it was 4.92 mm using the microscope. These results suggest that the use of our noninvasive registration and reference system may be effective, accurate, and useful for noninvasive tracking of patient movements in computer-assisted intranasal surgery.     

Pelvis-shoulder dysplasia

Pelvis-shoulder dysplasia is a rare focal skeletal dysostosis. We present the long-term follow-up of a patient with this condition. This patient has severe pelvic dysplasia but no involvement of the scapulae or clavicles. Despite the severity of the pelvic dysplasia, this man is able to function well. This is the fifth case of pelvis-shoulder dysplasia reported, but the only one documenting follow-up into adulthood. Received: 16 July 1997 Accepted: 4 February 1998     

Amantadine influences cognitive processing in patients with multiple sclerosis

We investigated the effect of amantadine on cognitive processing in patients with multiple sclerosis (MS) and fatigue with objective electrophysiological measures. Behavioral methods (Reaction Time, RT) and two different Event Related Potential (ERP) components measuring i) stimulus selection (Selection Negativity, SN) and ii) response selection (Lateralized Readiness Potential, LRP) were employed. Twenty-four patients with clinical definite MS (10 relapsing remitting and 14 secondary progressive) and confirmed fatigue in the past three months (Fatigue Severity Scale (FSS) > 4) were included. Patients were randomized in a double-blind, placebo-controlled cross-over design. We found a difference between the two treatments for ERP measures to stimuli with relevant colour starting at about 200 ms. This negativity had a higher amplitude during amantadine treatment regardless of treatment order. The RT did not differ significantly between the treated and untreated groups. Additional analysis indicated that patients with a disease duration of less than 7 years had a significant test position (practice effect), but no treatment effect, while patients with a longer MS duration showed no practice effect, but rather an improved reaction speed and increased ERP amplitude effects when treated with amantadine. The present findings suggest that amantadine exerts beneficial effects on early cognitive processes in patients with MS, but appears to be limited to subjects with a longer duration of the disease.     

An inter-centre quality assurance network for IMRT verification: results of the ESTRO QUASIMODO project.

BACKGROUND AND PURPOSE: IMRT necessitates extension of existing inter-centre quality assurance programs due to its increased complexity. We assessed the feasibility of an inter-centre verification method for different IMRT techniques. MATERIALS AND METHODS: Eight European radiotherapy institutions of the QUASIMODO network, have designed an IMRT plan for a horseshoe-shaped PTV surrounding a cylindrical OAR in a simplified pelvic phantom. All centres applied common plan objectives but used their own equipment for planning and delivery. They verified the delivery of this plan according to a common protocol with radiographic film and ionisation chamber measurements. The irradiated films, the results of the ionisation chamber measurements and the computed dose distributions were sent to one analysis centre that compared the measured and computed dose distributions with the gamma method and composite dose-area histograms. RESULTS: 4% (relative to the prescribed dose) and 3mm (distance-to-agreement) were decided feasible gamma criteria. The composite dose-area histograms showed a maximum local deviation of 3.5% in the mean dose of the PTV and 5% in the OAR. Systematic differences could be identified, and in some cases explained. CONCLUSIONS: This multi-centre dosimetric verification study demonstrated both the feasibility of a multi-centre quality assurance network to evaluate any IMRT planning and delivery system combination, as well as the validity of the methodology involved.     

Anticoagulant action of melagatran: a comparison between neonates and adults using calibrated automated thrombography (CAT)

In the present study, we comparatively evaluated the anticoagulant efficacy of the new direct thrombin inhibitor melagatran in cord vs. adult plasma. In contrast to heparin, melagatran does not require antithrombin as a cofactor. Thus, anticoagulant treatment with melagatran is of special interest in neonatal patients, whose plasma is relatively deficient in antithrombin. We evaluated the anticoagulant action of increasing amounts of melagatran (0.1–2.0 μmol/l) in both cord and adult plasma by means of calibrated automated thrombography (CAT) with respect to the lag time until the onset of thrombin formation, time to thrombin peak maximum (TTP), endogenous thrombin potential (ETP), and thrombin peak height. Melagatran exhibited approximately the same ability to prolong lag times or TTPs in both cord and adult plasma. Similar concentrations (IC₅₀) of melagatran were required to double the lag times (0.44±0.04 μmol/l vs. 0.52±0.05 μmol/l) or to double the TTPs (0.91±0.08 μmol/l vs. 1.06±0.09 μmol/l) in cord vs. adult plasma. Melagatran exhibited a higher ability to suppress ETPs or thrombin peak heights in cord vs. adult plasma. Markedly lower concentrations (IC₅₀) of melagatran were required to suppress ETPs (0.27±0.03 μmol/l vs. 0.70±0.06 μmol/l) or thrombin peak heights by 50% (0.29±0.03 μmol/l vs. 0.53±0.04 μmol/l) in cord vs. adult plasma. We conclude that our results suggest a higher ability of melagatran to suppress thrombin formation in cord vs. adult plasma. Thus, lower amounts of melagatran might be required in neonates undergoing antithrombotic therapy.