[Is a blockade of the lateral cutaneous nerve of the thigh an alternative to the classical femoral nerve blockade for knee joint arthroscopy? A randomised controlled study]. / Ist die Blockade des N. cutaneus femoris lateralis eine Alternative zu einer klassischen Femoralisblockade bei Kniegelenkarthroskopien? Eine randomisierte, kontrollierte Untersuchung.

BACKGROUND: Gaps in the distribution area of the lateral femoral cutaneous nerve (LFCN) are assumed to be the reason for pain caused by a thigh tourniquet when performing a femoral nerve (FN) block according to Winnie. The aim of the study was to evaluate if a direct single blockade of the LFCN in patients undergoing knee surgery resulted in a better tolerance to the tourniquet with equally good analgesic quality during surgery. METHODS: A total of 40 patients undergoing knee arthroscopy received a proximal blockade of the sciatic nerve and randomly either an FN or an LFCN block. Practicability, onset time, quality of sensory and motor block, and clinical effectiveness during tourniquet and surgery were assessed. RESULTS: Stimulation time was significantly longer in the LFCN than in the FN group. Quality of sensory and motor block was worse in the LFCN than the NF group. Of the LFCN patients 65% indicated troublesome paraesthesia or pain when a tourniquet was placed, compared to 35% of the FN patients. Of the LFCN patients 50% had pain during cutaneous incision, compared to none of the FN group. During the course of surgery, 70% of the LFCN patients needed supplemental systemic analgesia, but this was required by only 30% of the FN group. CONCLUSION: An LFCN block is not a suitable alternative to an FN block for regional anaesthesia. For patients with contraindications for an FN block according to Winnie (e.g. vessel surgery in the groin) other more effective methods are available.

[Characterization of the dentin by a 2-dimensional ultrasonic velocity profile]. / Dentincharakterisierung mittels zweidimensionaler Ultraschallgeschwindigkeitsprofile.

The velocity of sound is material-specific and therefore offers the opportunity for indirect physical characterization of materials. Preliminary ultrasound velocity profiles gained from ground tooth sections suggested that in the dentin core of the tooth areas of different sound velocity and thus different physical properties can be differentiated. As a base for this type of non-destructive characterization of materials an optimized and automated measurement system is presented, and its possibilities are critically discussed with regard to hardness tests. Normally, the LSV in the dentin core was found to be decreasing from the coronal to the apical regions, as well as from the outer to the inner parts near the pulp.

[The resolution of a 2-dimensional ultrasonic velocity profile of human tooth sections]. / Untersuchungen zur Auflösung zweidimensionaler Ultraschallgeschwindigkeitsprofile von humanen Zahnschliffen.

In a previous study (Löst et al. 1992, Löst et al. 1994) two-dimensional ultrasound velocity profiles of human dentin were introduced, and their possible significance and the underlying measuring system were discussed. Profiles of ultrasound velocity enable us to differentiate the structure and the elasticity of dental hard tissues. The quality of these color-coded profiles enhances with improved lateral resolution of the used ultrasound measuring system. Establishing an optimal window for displaying longitudinal sound velocities increases topological statements. Under given conditions of the measuring system an optimal lateral distance between points of measurement could be found. The differentiation of values within the profiles of ultrasound velocity is most meaningful applying a standardized window within the range of ultrasound velocity. For the used 20 MHz-ultrasound transducer a 0.2 mm lateral distance of measuring points was found to be optimal and a chosen window of ultrasound velocity in dentin from at least 2800 to 4300 m/s, respectively.

Two-dimensional distribution of sound velocity in ground sections of dentin.

The longitudinal velocity of sound in a specific material depends, amongst others, on the material's density and elasticity (Young's Modulus). Ultrasound therefore may be used for indirect characterization of materials. In this paper a method is described which allows high resolution measurements on coplanar ground sections of human teeth. The results are presented in two-dimensional velocity profiles. There is evidence from the first images, that longitudinal sound velocity (LSV) in dentin varies depending on the location. The use of LSV may be another way to characterize hard dental tissues physically, and to monitor induced changes.

Ultrasonic B-scans of the facial/oral periodontium in pigs.

In vitro ultrasonic scans of the oral/facial periodontium of pigs were obtained using a special experimental design and with the help of a newly developed ultrasonic measuring and analysis system. These two-dimensional images distinguish themselves from the one-dimensional RF-echograms and A-scans in that they enable the viewer to have a quick overview of the relationship between different interfaces in a scanned sector. A selection of ultrasonic B-scans proves that the scanned tissues such as gingiva, bone, periodontal ligament, tooth surface and even structures of the inner part of the tooth may be clearly imaged and distinctly differentiated. Furthermore, we demonstrate with manipulations of the pigs periodontium, that the interpretation of the pictures is correct. The primary goal of our investigation was to assess whether the ultrasonic procedure is suitable for the determination of the height of the facial/oral bone crest. On the basis of this study, we may confirm this supposition for the imaging in ultrasonic B-scans.

Determination of the facial/oral alveolar crest using RF-echograms. An in vitro study on the periodontium of pigs.

This study is a part of a research project in which we have been investigating the use of the ultrasonic pulse echo technique as a means of determining in vivo the facial/oral alveolar crest precisely and routinely. Here, RF-echograms are presented, showing the facial/oral periodontium of pigs. These echograms have been produced using a focussed 20 MHz transducer and a special design of an ultrasonic measuring and analysis system. In one series of measurements on macerated periodontia of pigs we found out that RF-echograms characteristic of a particular level of the facial/oral pericrestal aspect can be achieved. Based upon these results, we succeeded in determining exactly the height of the facial/oral alveolar crest in a 2nd experimental group using the intact periodontium of pigs. In all experiments, we tried to image separately both the echo amplitudes of the facial/oral alveolar plate and of the tooth surface. In other words, the periodontal ligament space is imaged sonographically. In our experience, the imaging of the space is an important aspect for the correct interpretation of echograms. Possibilities and limits of this method are demonstrated and explained.

[Determination of the acoustical properties of enamel, dentin and alveolar bone]. / Bestimmung akustischer Kenngrössen von Schmelz, Dentin und Alveolarknochen.

An ultrasonic method for periodontal diagnosis has been developed by the authors. A fundamental part of this work is the evaluation of the acoustical properties of the hard tissues: enamel, dentine and alveolar bone. Using an adapted measuring device, in combination with a computer-controlled signal acquisition and analysing system, acoustical parameters (velocity, impedance and frequency-dependent attenuation) are determined. The knowledge of these parameters is a prerequisite for a correct interpretation of A-mode and B-mode images, representing parts of the oral/facial aspect of a periodontium.