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Biomedical subjects

R Ascherl

Publications and source records attributed to R Ascherl.

53 records · Page 3Linked to original sources
PubMed1985

[Comparative experimental studies with biologic materials for replacement of the anterior cruciate ligament].

Allogeneic and xenogeneic biological tendon and ligament materials for ligament replacement were tested in the knee of rabbits and sheep. In-vitro and ex-vivo biomechanical tests as well as micromorphological investigations following implantation were performed. The preparation procedure mainly consists in cross linking of collagen by dicarboxylic acids (DC). Modifications in the method induce changes in the biomechanical stability also after implantation. Sheep with autologous patellar tendons substitutions and glutaraldehyde (GA) fixed bovine tendons served as controls. Because of biocompatibility reasons the later seem to be not yet suitable for clinical applications. The DC-tendons need for improved midterm stability prior to clinical implantations; the biocompatibility appears to be excellent.

Animals↗
PubMed1984

Viability of surrounding tissue attached to vein graft.

The technique of grafting skin with an attached subcutaneous vein for vessel-skin defects was investigated in an experimental rabbit study. Vein grafts were not able to nourish the skin immediately after grafting. After 14 days, there was a certain amount of vital, revascularized tissue in the area of the vein graft. Plasmatic circulation and revascularization from the wound bed are apparently responsible for the successful clinical application of this technique.

Angiography↗
PubMed1981

[Clinical picture in Sudeck's dystrophy].

Concerning course, symptomatology and morphology the clinical picture of Sudeck's dystrophy is commented unanimously. Different views of pathogenesis, terminology, and therapy are still existing. Among multifarious contributing factors, vasomotor reflexes as well as endogenous factors are of particular significance. Methods of treatment and their benefits within different stages are pointed out and discussed. Besides physical treatment, application of calcitonin or neurostimulation are viewed to be effective. In cases of progressing dystrophy blocking of the sympathetic ganglia or (periarterial) sympathectomy are still measures of benefit. Prophylaxis is of great importance, though Sudeck's dystrophy is not always avoidable.

Diagnosis, Differential↗
PubMed1979

[Treatment of infected pseudoarthroses with electrodynamic field therapy].

The electrodynamic field treatment, its method and fundamentals in the therapy of infected, atrophic pseudarthrosis are described. In addition to the common principles of treatment, particularly the transplantation of autologous spongious bone is of great importance. The bone graft reestablishes normal electrical conduction within the pseudarthrosis and as a reactive receptor for the applied a.c.-potentials consolidates the defect. Up to now in 8 years of employing this method 271 patients, suffering from pseudarthroses have been treated, 91 of them had an infected, often atrophic pseudarthrosis. In each group in 92% of the cases bony healing could be achieved. Some case reports demonstrate clinic and therapy.

Action Potentials↗
PubMedDate not supplied

[Mechanical stability of hip joint endoprosthesis shafts of carbon fiber composite materials].

The use of composite materials in orthopaedic surgery permits the design of implants with varying degrees of stiffness. A system of carbon fibre reinforced epoxy hip stems was investigated and compared to the mechanical safety of metal ones. Special attention has been paid to the fact that torsional moments are the common failure mechanism of composite materials. In total 74 hip stems (three different sizes) have been tested under static and dynamic loading conditions according to ISO 7206. A group of 27 implants was pre-conditioned for 75 days in 80 degrees C Ringer's solution to discover potential degradation effects of absorbed fluids. The carbon fibre hip stems proved to reach run-out loads higher than conventional metal ones. Moisture absorption didn't influence the mechanical properties within the range of the experimental accuracy. The calculated fatigue stress of 750 MPa permits further optimization of stiffness parameters without the risk of implant fracture.

Biomechanical Phenomena↗
PubMedDate not supplied

[Experimental studies of the biomechanical properties of hollow nails and solid nails for interlocking intramedullary nailing in the dog].

Since locked intramedullary nailing of the tibia in dogs was followed by material failure of the conventional slotted hollow nails within days, special solid nails were developed and tested with respect to their mechanical properties. There was a clear advantage of the solid nails over the hollow nails in terms of bending resistance and yield force. In animal experiments--even in long-term experiments over nine months--no case of material failure occurred with the solid nails. The high torsional and bending resistance of the solid nails suggests the use of a mechanical device which, as our experience shows, permits reliable interlocking without the need for an image intensifier, that is to say, without radiation exposure.

Animals↗
PubMedDate not supplied

[A method for determining the biomechanical properties of trabecular and spongiosa bone tissue].

With the aim of determining the biomechanical properties of cancellous bone, a method was developed that permits the investigation of the effects of tensile and compressive forces on cancellous bone trabeculae while eliminating the problem of porosity. Individual, rod-like trabeculae were removed from cancellous bone with the aid of special instruments. Each end of a trabeculae was embedded in a cylinder of polymethylmethacrylate. To keep bending moments to a minimum while testing, the trabeculae was aligned along the longitudinal axis of the cylinders with the aid of positioning instruments. With a test apparatus, the deformation behaviour and maximum strength of the trabeculae under tension and compression can be determined under both dry and moist conditions. With account being taken of shape and dimensions of the trabeculae, the material properties of the cancellous bone tissue can be computed. In comparison with the small number of methods so far used for investigating trabeculae, a number of advantages were found: 1. Tensile and compression testing in a single specimen, 2. testing under reliably moist conditions, 3. non-destructive testing enabling further investigations on the specimen.

Biomechanical Phenomena↗
PubMedDate not supplied

Treatment of pseudarthroses with electrodynamic potentials of low frequency range.

In 319 patients suffering from septic and noninfected pseudarthroses, bone consolidation has been achieved in 93.6% by a cancellous bone graft plus a semi-invasive method of electrostimulation of nonunion using low frequency A.C. potentials, i.e., the electrodynamic procedure. By inductively coupled electromagnetic fields, the potentials are produced in inductable implants. There are no contraindications for the procedure and no side effects.

Adult↗