Biomedical subjects
A Melzer
Publications and source records attributed to A Melzer.
Histologic effects of different technologies for dissection in endoscopic surgery: Nd:YAG laser, high frequency and water-jet.
Precise cutting combined with reliable coagulation of the margins of the lesion is an important requirement for dissection techniques in endoscopic surgery. These requirements are met by the two most common ancillary energy sources applied for endoscopic dissection today, electrosurgery and "thermal lasers", mostly the Nd:YAG. For the comparison of the histological effects of monopolar and bipolar high frequency with the Nd:YAG laser an experimental in vitro and in vivo study has been performed. In order to evaluate the advantages of non thermal dissection for endoscopic procedures, a water jet cutting system was included in the in vitro study. In parenchymatous tissue the water jet was found to be the least traumatic technique, followed by bipolar high frequency, laser and monopolar high frequency. The water jet was not applicable for intestinal dissection since uncontrolled bloating of the rectal wall with uncontrolled disruption of the tissue layers occurred. A general disadvantage is that secure haemostasis in the line of incision is hard to achieve. In the microscopic comparison of the shape of the incision, the Nd:YAG laser produced the smoothest lesions with well-defined margins. The monopolar technique was more often associated with irregular and sometimes fissured margins. These results were confirmed in the in vivo part of the study (Transanal Endoscopic Microsurgery).
Materials for surgical instruments: metallurgy. I.
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Development of steerable instruments for minimal invasive surgery in modular conception.
The augmenting complexity of minimal invasive interventions requests a continuous improvement of technologies. Extended endoscopic procedures, e.g. laparoscopic-transanal sigmoidectomy or thoracoscopic esophagus dissection require difficult surgical manipulations like mobilisation, sceletonization as well as ligatures and sutures. They are difficult to perform with the present endo-surgical instruments. A major instrumental weakness is represented by the restricted steerability because of the rigid shaft axis and the resulting low degrees of freedom (DOF). Therefore a series of steerable flexible instruments has been developed in interdisciplinary cooperation between surgeons and engineers. The prototypes provide a multi-joint working as the instrument's elbow, which allows to incline the tip around +/- 280 degrees. The second additional DOF is the rotation of the surgical tool. The prototypes have been experimentally tested in laparoscopy and thoracoscopy, showing a clear improvement in the carrying out of complex operative manipulations. The further development is performed in modular conception, including electric drives.