Volume 53, Issue 4

Prediction of countershock success from ventricular fibrillation (VF) ECG is a major challenge in critical care medicine. Recent findings indicate that stable, high frequency mother rotors are one possible mechanism maintaining VF. A computer model study was performed to investigate how epicardiac sources are reflected in the ECG. In the cardiac tissues of two computer models – a model with cubic geometry and a simplified torso model with a left ventricle – a mother rotor was induced by increasing the potassium rectifier current. On the epicardium, the dominant frequency (DF) map revealed a constant DF of 23 Hz (cubic model) and 24.4 Hz (torso model) in the region of the mother rotor, respectively. A sharp drop of frequency (3–18 Hz in the cubic model and 12.4–18 Hz in the torso model) occurred in the surrounding epicardial tissue of chaotic fibrillatory conduction. While no organized pattern was observable on the body surface of the cubic model, the mother rotor frequency can be identified in the anterior surface of the torso model because of the chosen position of the mother rotor in the ventricle (shortest distance to the body surface). Nevertheless, the DFs were damped on the body surfaces of both models (4.6–8.5 Hz in the cubic model and 14.4–16.4 Hz in the torso model). Thus, it was shown in this computer model study that wave propagation transforms the spatial low pass filtering of the thorax into a temporal low pass. In contrast to the resistive-capacitive low pass filter formed by the tissue, this spatial-temporal low pass filter becomes effective at low frequencies (tens of Hertz). This effect damps the high frequency components arising from the heart and it hampers a direct observation of rapid, organized sources of VF in the ECGs, when in an emergency case an artifact-free recording is not possible. Zusammenfassung Die Vorhersage des Defibrillationserfolges bei Kammerflimmern (VF) stellt eine grosse Herausforderung in der Notfallmedizin dar. Neueste Forschungsergebnisse zeigen, dass stabile Hochfrequenzrotoren (Mother Rotors) ein möglicher Mechanismus sind, um VF aufrechtzuerhalten. Deshalb wurde in zwei Computermodellen – ei-nem Modell mit kubischer Geometrie und einem verein-fachten Torsomodell mit linkem Ventrikel – untersucht, wie sich die epikardiale Aktivität auf der Körperoberfläche abbildet. Ein stabiler Rotor wurde in der Mitte des Herzgewebes durch Erhöhung des Kaliumstromes induziert. Betrachtet man die dominierenden Frequenzen (DF) der epikardialen Schicht beider Modelle, kann man in der Region des Rotors eine konstante Frequenz von 23 Hz im kubischen Modell beziehungsweise von 24.4 Hz im Torsomodell nachweisen. Im umgebenden Gewebe ist ein chaotisch flimmerndes Muster mit geringeren Frequenzen (3–18 Hz im kubischen Modell und 12.4–18 Hz im Torsomodell) beobachtbar. Während auf der Körperoberfläche des kubischen Modells keine organisierte Region erkennbar ist, kann man die Mother-Rotor-Frequenz auf der Torsooberfläche wegen der gewählten Position des Rotors im Ventrikel (kürzester Abstand zwischen Ventrikel und Körperoberfläche) beobachten. Dennoch werden die auftretenden DFs auf der Körperoberfläche in beiden Modellen gedämpft (4.6–8.5 Hz im kubischen Modell und 14.4–16.4 Hz im Torsomodell). Es konnte gezeigt werden, dass es wegen räumlicher Glättung der Potentialverteilung im Thorax in Kombination mit der kontinuierlichen Erregungsausbreitung sowohl zu einer räumlichen als auch zeitlichen Tiefpassfilterung des EKG-Signals kommt. Durch die Dämpfung von hochfrequenten Signalkomponenten an der Körperoberfläche wird die Messung epikardialer Organisation im EKG erschwert, wenn eine artefaktfreie Signalaufnahme im Notfall nicht möglich ist.

The purpose of this study was to introduce infinite models in scoliosis and to analyze personal experience. Based on a three-dimensional patient-specific finite element model of the spine, rib cage, pelvis and abdomen, a parametric individual model of a thoracolumbosacral orthosis was built. Three standard strap tensions (20, 40, 60 N) were loaded on the back of the brace to simulate the strap tension. The I-Scan distribution pressure measurement system was used to measure the pressure of the different regions and the equivalent forces in these regions were calculated. The spinal curve changes and the forces acted on the brace generated by the strap tension were evaluated and compared with the measurement results. The reduction of the coronal curvature was approximately 60% for a strap tension of 60 N. The sacral slope and the lordosis were partially reduced in this case. The brace modified the axial rotation at the deformed vertebrae. The forces generated in finite element analysis were in good agreement with the measurement. The findings supported the feasibility of such an approach to analyze individual bracing biomechanics, which may be useful in the design of more effective individual braces.

Aim : The aim of this study was to evaluate a new endodontic leakage measurement method. Materials and methods : Permeability was assessed measuring the gas flow passing through the root. Positive and negative tests were carried out to assess the validity of the method. We used glass capillaries for calibration (diameters of 15, 30, 40, 50 and 75 μm). The applicability of the method was assessed with human teeth using three sealing methods: GuttaFlow (GF) and a single cone; Pulp Canal Sealer (PCS) and a single cone; PCS and system B. Results : This method demonstrated to be highly reproducible as the standard deviation was approximately 1% on average with glass capillaries. Significantly higher leakage (p<0.05) was recorded for endodontic treatment with GF and single cone compared to PCS and single cone and PCS with system B. Conclusion : Gas permeability is quantitative, sensitive, non-destructive and reproducible and seems appropriate for endodontic tests. It would participate in the indirect comprehension of leakage phenomena.

One of the current main challenges in transluminal surgery is in obtaining sterile and secure access to the peritoneal cavity. Since the transgastric approach has not fulfilled these requirements up to now, a new transcolonic surgical approach was developed to achieve these objectives and enhance the potential of transluminal surgery. A new set of instruments comprising an endoscopic trocar, a flexible obturator and a modified transanal endoscopic microsurgery device was designed to permit sterile sigmoid access for transcolonic surgery. The set of instruments has already been successfully tested in an experimental in vivo survival study that confirmed safety and sterility as objectives during surgical intervention. The suitability of the instruments for use in the human anatomy was confirmed by a cadaveric study. Zusammenfassung Eine der Hauptherausforderungen in der heutigen transluminalen Chirurgie ist die Herstellung eines sterilen und sicheren Zugangs zur Bauchhöhle. Da die transgastrische Entrierung des Abdomens diese Anforderungen bis heute nicht hinreichend erfüllt hat, wird der neue Ansatz einer transkolischen Penetration eingeführt, um die definierte Zielsetzung zu erfüllen und die Potenziale der transluminalen Chirurgie zu erweitern. Ein neues Instrumentenset bestehend aus einem endoskopischen Trokar, einem flexiblen Obturator und einem modifizierten transanalen endoskopischen Mikrochirurgiegerät wurden entwickelt, um einen sterilen sigmoidalen Zugang für die transkolische Chirurgie zu ermöglichen. Das Instrumentenset konnte in einer experimentellen In - vivo -Studie erfolgreich getestet werden. Sicherheit und Sterilität, als wichtige Zielsetzungen, konnten während des ganzen chirurgischen Eingriffs gewährleistet werden. Die Tauglichkeit für den Einsatz in der menschlichen Anatomie wurde durch eine zusätzliche Leichenstudie bestätigt.

Background : Allogeneic bone transplantation is at risk of infection, and established disinfection methods typically compromise bone quality. High hydrostatic pressure (HHP) is well established for disinfection in food technology, and also it does protect biomechanical and biological properties of bone. This study is the first investigation of HHP regarding disinfection of bone biopsies. Materials and methods : Bone biopsies of 34 patients with chronic infections were subjected to HHP and assessed for persisting bacterial growth. In series 1, bone biopsies were proceeded directly to HHP (10 min; maximal pressure P max 600 MPa). In series 2, HHP was applied after 5-day incubation in growth media (10 min or 2×30 min; P max 600 MPa). Furthermore, HHP-induced changes of bacterial morphology on artificially infected bone samples were evaluated by scanning electron microscopy (SEM). Results : For series 1, 71% of the bone samples were sterilised by HHP (n=17), compared to 38% of the untreated control samples, which were obtained during the same surgery (n=8). For series 2, after prior incubation, HHP disinfected 7% of the bone specimens (n=55), all control samples showed bacterial growth (n=33). Destruction of cell wall integrity of Gram-negative strains was observed by SEM. Conclusion : The effectiveness of HHP for bone disinfection should be improved by optimising treatment parameters. Infections with barosensitive Gram-negative bacteria or yeast might represent possible clinical indications.

The potential of plasma treatment in medicine is only slowly gaining acceptance. Inactivation of germs through exposure to UV radiation produced by plasma discharges and sterilization of medical implant devices and instruments is one possible application of this technique. In addition, due to the manifold possibilities of coating through plasma processes, quick sterilization-coating combinations of medical implant devices are possible. To analyze the effectiveness of this sterilization process on different material surfaces, three different alloys (X2CrNiMo18-15-3, Ti6Al7Nb and Ti6Al4V) and one thermoplastic material (ultra-high molecular weight polyethylene, UHMWPE), commonly used in medical implant devices, were examined in the presented study. After spraying Bacillus atrophaeus spores (10 6 CFU) on the surfaces of four different implant materials tested in this study (X2CrNiMo18-15-3, UHMWPE, Ti6Al7Nb and Ti6Al4V), it was demonstrated in each of four gas mixtures used (Ar, Ar:O 2 , Ar:H 2 and Ar:N 2 ) that due to the application of inductively coupled low-pressure plasma technique, plain medical implant materials can be sterilized rapidly, and can be protective and efficient.

Background : The most essential improvement of modern hip resurfacing arthroplasty is the metal-on-metal bearing as well as the integration of a procedure for the exact and repeatable positioning of the femoral component through a specific mechanical alignment instrument. Nevertheless, the main reasons for early implant failure are mal-positioning of the femoral component and notching of the femoral neck during femoral head preparation. Materials and methods: In the context of an in vitro study, in each case six DUROM™-Hip resurfacing prostheses were implanted in artificial femora with the prosthesis-specific mechanical alignment instrument, as well as under navigation control. The aim of the study was to evaluate the functionality and accuracy of a computer-assisted planning and navigation system on the basis of a navigation module library from Surgitaix AG (Aachen, Germany), as well as a comparison with the prosthesis-specific mechanical alignment instrument. Results: The main angulation error between planning and navigation of the stem-shaft angle was 0.2±1.2° for the navigation system and 6.5±4.1° for the mechanical alignment instrument, the main anterior offset error was 1.2±1.2 mm vs. -0.83±4.1 mm. The mean time for all five planning and navigation steps was 17±1.2 min vs. 14±0.8 min. The main distance error between planning and navigation was 1.9±0.6 mm for the navigation system, and 5.3±2.4 mm for the mechanical alignment instrument. Femoral notching was not observed for navigational or conventional positioning. Conclusion: The computer-assisted fluoroscopic planning and navigation system for hip resurfacing showed, within the scope of this in vitro study, first promising experiences. The system approves a practicable planning with a high accuracy in implementation. Nevertheless, the potential benefit has to be evaluated in further clinical studies, especially from the perspective of a possible integration of this navigation system into the clinical workflow. Further studies should consider a fluoroscopy-assisted range of motion assessment under consideration of an additional cup-module to enhance the postoperative range of motion after hip resurfacing procedures.