In endoprosthetics alumina ceramic femoral heads have been established for many years and their outstanding wear characteristics are scientifically proven. The taper connection between the hard but brittle ceramic head and the metallic stem must be performed by the operating surgeon intraoperatively. Thereby it is left to the surgeon to interpret imprecise and strongly deviating instructions given from manufacturer to manufacturer. This study clarifies the enormously large variations of interpretation in the clinical everyday life based on interviews and force measurements during handling when assembling. In comparable situations the axial cone setting forces, applied by a total of 39 operating surgeons from German hospitals, varied between 273 N and 7848 N. An additional coupling strength examination in the laboratory shows that torque loadings necessary for loosening several cone connection designs are in the range of those occurring under usual in vivo situations. This leads to the conclusion that for low-force-connected cone tapers joint friction of the artificial hip joint can cause a rotation and thus a loosening of the ceramic head of the implant neck during everyday activities. The authors proclaim the urgent necessity for clear handling references and the supply of a reproducibly safe taper lock method.
A review of current clinically applied biomaterials for the femoral heads and acetabular cups of total hip prostheses (UHMWPE, CoCrMo alloys, alumina and zirkonium) in terms of their resistance to wear is presented. Further developments in metallic and ceramic materials over the last few years have now left UHMWPE as the weakest link in the prosthesis material chain. Alternative materials aimed at improving the tribological properties of the femoral head/acetabular head system are presented. New surface hardening and coating techniques for titanium alloys, polymer coatings, optimized UHMWPE, as well as various carbon-fibre-reinforced synthetic materials are described. The advantages, disadvantages and prospects of these materials are compared with those of standard materials and documented in experimental and clinical studies.
Die endoskopische Infrarot-Diaphanoskopie ist ein Verfahren mit dem Ziel, eine Orientierungsverbesserung in der Nasenhaupthöhle bei endoskopisch kontrollierten, endonasalen Eingriffen im Bereich der Nasennebenhöhle zu erreichen. Die Durchleuchtung soll es ermöglichen, die natürlichen Zugänge von den Nasennebenhöhlen (NNH) zur Nasenhaupthöhle unter endoskopischer Sicht besser zu lokalisieren. Die vorliegende Arbeit spezifiziert die notwendigen Voraussetzungen anhand von In-vitro-Untersuchungen am Tiermodell (Schaf) und am humanen Halbkopfpräparat. Fragen, für welche NNH eine Durchleuchtung prinzipiell möglich ist, ob die Durchleuchtung ein Auffinden der natürlichen Übergänge von einzelnen Nasennebenhöhlen zur Nasenhaupthöhle ermöglicht und welche gerätetechnischen Anforderungen erfüllt werden müssen, werden beantwortet. · ·
Key words: Infrared Diaphanoscopy -endonasal surgery -nasal cavities -in vitro investigationEndoscopic infrared diaphanoscopy is a method of improving orientation in the nasal cavity during endoscopy-controlled endonasal surgery. The transillumination is expected to f acilitate the localisation of the natural passageways between the paranasal sinuses and the nasal cavity during endoscopic procedures. The present study specifies the necessary conditions on the basis of in vitro examinations using an animal model (sheep) and an anatomical preparation of half of the human head. The questions äs to what paranasal sinus is at all accessible to diaphanoscopy, whether the method actually enables the connecting pathways between an individual sinus and the nasal cavity to be identified, and what technical demands need to be met, are considered and answered.
The current success of the treatment of trochanteric fractures of the femur still depends on the type of fracture involved. A number of surgical procedures have proved successful in the treatment of stable fractures (e.g. dynamic hip screw, gamma nail). However, the treatment of unstable fractures remains a problem. With this type of fracture the implant is exposed to very unfavourable biomechanical loading that often leads to failure of the osteosynthesis, and makes removal of the implant necessary. In extensive tests, the biomechanical loading capacity of a new Y-nail has been investigated as a function of the stability and location of the fracture. The results show that this form of intramedullary fixing is suitable for both stable and unstable fractures. Unstable, far distal subtrochanteric fractures of the femur remain borderline indications.
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