Bernhard Clasbrummel

Passive Wireless Resonant Galfenol Sensor for Osteosynthesis Plate Bending Measurement

The healing process of bone fractures can be monitored by a measurement of the osteosynthesis plate bending. For this purpose a wireless magnetostrictive bending sensor is proposed. A planar rectangular coil on top of a magnetostrictive Galfenol ( alloy) layer forms an electrical resonant circuit. The sensor is manufactured in thin film technology. Coil turns were electrodeposited by pattern plating. Sensors with overall dimensions of (13 2 0.5) mm were manufactured with varied turn numbers showing self-resonance frequencies from 5 to 50 MHz. Examined sensors possess linear frequency-force characteristic up to 6 N with frequency shifts of 6 kHz . In order to obtain the sensor resonance frequency wirelessly, several measurement techniques were employed using inductively coupled coils. Frequency domain measurements have been carried out by employing a network analyzer with a single detection coil and a lock-in amplifier with separate coils for excitation and detection. In time domain measurements, two coils for transmission and reception are used. In the transmit case a short sine pulse excites the sensor and afterwards its decaying response signal is received. To determine the resonance frequency, a frequency counting, Fourier or wavelet technique can be used. By integrating additional cores of high permeability into sensor and detection coil, measurement ranges can be increased.

Pressure sensors for the monitoring of diseases in surgical care

Microtechnology components are already pointing the way forwards in minimally invasive diagnosis, therapy and therapy monitoring, in implants and medication dosage systems. The latest developments show a wide range of new possible uses for microtechnology in medical applications. The world market in physical pressure, temperature and acceleration sensors was worth several hundred billion euros in 2003. Given the extreme miniaturisation now possible through micro- and nanotechnology, such sensors readily suggest themselves for medical applications. If physical sensors are linked to a telemetric unit for wireless data transmission, are biocompatibly packaged or are implanted in a minimally invasive procedure, then bodily functions such as the acceleration of vessel walls, blood pressure, temperature or nerve streams can be measured permanently and wirelessly.  Regarding pressure sensors, surgical diagnosis is yielding a range of possibilities extending from pressure measurements in the brain following a trauma, compartment pressure measurements in the abdomen, organs or extremities through to bladder pressure measurements for injury patients with compartment syndrome. The present work gives a surgery-based overview of the latest developments and trends in this high technology field.

Gibt es das universelle Implantat zur Versorgung trochantärer Femurfrakturen

ZusammenfassungEtwa 40 000 trochantäre Femurfrakturen sind jährlich in Deutschland zu erwarten. Die Inzidenz ist steigend. Als typische Fraktur des älteren Menschen ist der unfallbedingte Verlust des Lebens oder der persönlichen Selbstandigkeit zu befürchten und in der Vergangenheit häufig eingetreten. Während in den 70er Jahren bis zu 19 verschiedene Operationsverfahren miteinander konkurrierten, kommen heute fast nur die dynamische Hüftschraube (DHS), ggf. in Kombination mit der Trochanterabstützplatte, und der Gammanagel bzw. seine Weiterentwicklung, der Gleitnagel, zur Anwendung. Berichtet wird ër 217 Patienten, die wegen einer trochantären Femurfraktur mit einer DHS, in 14 Fällen kombiniert mit einer Trochanterabstützplatte, versorgt wurden. Es traten 4,6% implantatspezifische Komplikationen auf, bei sieben Patienten (7,8%) kam es postoperativ zu einem Verlust an persönlicher Selbständigkeit. Die Krankenhausletalität lag bei 0,9%.AbstractApproximately 40,000 trochanteric femur fractues have to be expected in Germany yearly. The incidence is increasing. As a typical fracture type of the elder patient here the posttraumatic loss of life or of personal independence has to be suspected and in former times frequently took place. Whereas in the 70s up to 19 different competitive techniques of operation were applied, nowadays the dynamic hip screw (DHS), if necessary combined with the trochanter support sheet and the gamma-nail, respectively its development, the glide-nail are utilized.It is reported on 217 patients treated with a DHS because of a trochanteric femur fracture, in 14 cases combined with a trochanter support sheet. 4.6% implant complications occurred, 7 patients (7.8%) postoperatively showed a loss of personal independence. The hospital mortality was 0.9%.

Mikro- und Nanosystemtechnik – medizintechnologische Aspekte am Beispiel eines Blasendrucksensors

In der minimal invasiven Diagnostik, Therapie und Therapiekontrolle, bei Implantaten oder Medikamentdosiersystemen sind heute mikro- und nanotechnologische Komponenten wesentliche Bausteine von Gesamtsystemen. Aktuelle Entwicklungen zeigen ein weites Feld von Einsatzmöglichkeiten der Mikro- und Nanotechnik für medizinische Anwendungen. Allein der Weltmarkt physikalischer Sensoren für Druck, Temperatur und Beschleunigung erreichte im Jahr 2003 ein Handelsvolumen von mehreren 100 Milliarden EUR. Aufgrund extremer Miniaturisierung durch mikro- und nanotechnologische Methoden bieten sich kleinste Sensoren für medizinische Anwendungen immer mehr an. Werden physikalische Sensoren mit einer Telemetrieeinheit zur drahtlosen Datenübertragung verbunden, biokompatibel verpackt und minimal invasiv implantiert, können Parameter von Körperfunktionen - wie Drücke in Organen oder Blutdruck, Beschleunigung von Gefäßwänden, Temperatur oder Nervenströme - permanent und kabellos gemessen werden. Für den Bereich der Drucksensorik eröffnen sich in der chirurgischen Diagnostik eine Reihe von Möglichkeiten, die von Druckmessungen im Gehirn nach Trauma, Kompartmentdruckmessungen im Abdomen, Organen oder Extremitäten bis hin zu Blasendruckmessungen bei Patienten mit Querschnittssyndrom reichen. In der vorliegenden Arbeit wird am Beispiel eines Blasendrucksensors dieser Hochtechnologiebereich aus chirurgischer Sicht dargestellt und diskutiert.

Anregung und drahtlose Lock-in-Messung von Hüftprothesenschwingungen zur LockerungsdetektionExcitation and Wireless Lock-in Measurement of Hip Prosthesis Vibrations for Loosening Detection

Zusammenfassung Es wird ein Experimentalaufbau zur Anregung und drahtlosen Messung von Schwingungen einer teilweise in einen künstlichen Oberschenkelknochen einzementierten Hüftprothese vorgestellt. Um das dynamische Verhalten des mechanischen Systems zu diskutieren, wurde ein translatorisch-rotatorisches Netzwerkmodell erstellt. Mit diesem Modell werden die Eigenfrequenzen des Femur-Prothesen-Verbundes berechnet.

A wireless integrated hip prosthesis loosening detection system - influence of mechanical cross-sensitivities on resonance frequencies

Established diagnostic methods used to detect hip prosthesis loosening are mostly based on imaging techniques and are still accompanied with a high failure rate leading to either unnecessary revision of sufficiently osseointegrated endoprostheses or a too late diagnosis with bone stock destruction and difficulties in implant revision. A possible alternative approach is in-vivo vibration analysis directly at the prosthesis. This could allow early post implantation healing process monitoring and later on the detection of prosthesis loosening by evaluating frequency response characteristics identifiable through the presented integrated wireless measurement system positioned in the femoral ball head.

B1.3 - Excitation and Wireless Lock-In Measurement of Hip Prosthesis Vibrations for Loosening Detection

An experimental setup for excitation and detection of hip prosthesis loosing is developed and analyzed. Small vibration signals are detected by acceleration sensors fixed in the prosthesis. Lock-in technique is applied to separate sensor signals at low signal-to-noise ratio. Stand-alone measurements were taken at an artificial thigh where an electrodynamic audio shaker was fixed at the knee using an appropriate designed support structure. It could be demonstrated that the measurement setup is suitable to excite and to measure oscillations of a prosthesis which was partially fixed in an artificial femur.

Femoral neck fracture

: Femoral neck fractures are frequent fractures of the elderly. They can be treated by the use of dynamic hip screws, lag screws, bipolar hemi-protheses or total hip replacement. The results are markedly influenced by the timing of the operation and the choice of the implant. Using the Garden classification of femoral neck fracture we demonstrate a different therapeutic approach according to Garden stadium I-IV.