PubMed Health⌕ Search

Biomedical subjects

R Ascherl

Publications and source records attributed to R Ascherl.

At least 19 recordsLinked to original sources
PubMed1992

Cementless prosthesis of the hip joint with "spongy metal" surface. A prospective study.

Our investigations in human specimens and animal experiments show that prostheses with a spongy metal surface can become fixed by bony ingrowth to varying degrees. After consistent clinical and radiological follow-up over 12-65 months (mean 34 months) in a prospective study of 100 consecutive patients in whom 106 cementless total hip replacements had been carried out, we were able to show that after 1 year 82% of patients were pain-free with the prosthesis fixed by bony ingrowth, 8% were pain-free with the prosthesis fixed by dense fibrous tissue and 10% were not pain-free, but did not want revision surgery. Thigh pain decreased steadily from 53% 3 months postoperatively to 6.6% 15 months after operation. We believe that, when the implantation technique is exact, a high percentage of cementless spongy metal prostheses are fixed by bony ingrowth, and that a cementless prosthesis should be implanted only in patients under 60 years of age without osteoporosis.

Female↗
PubMed1992

[The value of epidemiologic studies of ski injuries].

The Garmisch-Partenkirchen experience--15,513 skiing injuries between 1972 and 1990--was compared to the results of an inquiry into the skiing injuries among 565 persons of the medical profession, that were active skiers over an average of 18 years. The parameter injuries per 1000 skiing days was calculated from the outpatient clinic data as well as from all skiing injuries that had happened in the interview group and those that required surgical treatment. The mean value of 2.7 injuries/1000 skiing days--corrected for the number of patients--from the literature and the clinical data with 2.1 is comparable to the 1.8 injuries/1000 skiing days (injuries that required surgical treatment) but stands sharply against the 4.2 arising from the total number of injuries in the inquiry group.--Thus, every epidemiological study clearly underestimates the actual rate of skiing injuries. This fact may be defined as the "bypass-effect". The comparison between clinical setting and inquiry allowed for a quantification: Depending on the type of injury and the study design, a true prevalence of skiing injuries that is between 10% and 200% higher than the published data has to be expected.--Descriptive, not controlled epidemiologic studies on skiing injuries are justified and give valid trends on which therapeutic and prophylactic measures can be based--but exclusively under the following prerequisite conditions: 1. a standardized study protocol; 2. an observation.

Adult↗
PubMed1992

[Experimental studies of thermal disinfection and sterilization of allogeneic bone transplants and their effects on biological viability].

Thermal energy (80 degrees) for the disinfection of cancellous allogenic bone grafts was employed, and it proved to be an advantageous, safe and easily accessible method. The effects of this treatment on biological values were examined in terms of biomechanical and biodynamic (graft incorporation) loss of the treated grafts versus the autoclaved and untreated samples. Given the thermolability of the pathogens in question, the thermal approach presented here has the advantage of being readily controllable. The lack of toxic or mutagenic risks through this method and its accessibility represent further advantages. In thermal treatment of bone allografts, it is essential that one knows the thermoconductivity of the bone sample and that one can demonstrate pathogen inactivation through the entire graft volume. All of the parameters in the 80 degrees C group that were measured in this study indicate clear biological superiority over the autoclaved group. A newly developed thermoincubator is introduced for gentler disinfection of allogenic bone grafts and it inactivates common vegetative pathogens as well as HIV. It is still necessary to conduct serological screening for hepatitis antigens in the donor pool, however. Based on these results, we conclude that the clinical use of autoclaved allogenic bone grafts needs to be reviewed and possibly limited.

Animals↗
PubMed1990

Quantitative effects of allogeneic small-bowel transplantation on nutrient digestion and on body protein balance as determined in vivo in rats.

Heterotopic and orthotopic small-bowel allotransplantation was carried out in Wistar rats using grafts reduced to one-half of the original length. Portocaval venous anastomoses and intestinal end-to-end anastomoses were performed. Animals either with complete or with partially reduced native small-bowel served as control. In a total of 51 rats, 88 quantitative in vivo measurements of apparent digestion and absorption of dietary dry matter, organic matter, energy, protein, fat, total ash, and glucose were carried out. Body protein retention was calculated from intake and losses with feces and urine. The digestion trials comprised 8 days of adaptation and 10 days of continual recording of nutrient balance data. In experiments 1 and 2, digestibility coefficients were obtained before and after transplantation within the same animals, untreated or initially treated with cyclosporine A after surgery. Similar groups of rats untreated, with partial resection and with transplantation of the small-bowel, followed by temporary cyclosporine treatment, were used in experiment 3. In experiment 4, rats with transplanted intestines from experiments 1 and 2 were subjected to a further digestion trial 4 to 6 months after the respective first trial. With transplantation of the small intestine, apparent digestion and absorption of nutrients, as well as protein retention, tended to be lower. Significant depression occurred in the digestion of fat and ash. In long-term survivors all parameters decreased further. The adverse effects on fat and ash digestion seemed to be pronounced when rejection occurred. Fecal fat excretion might therefore be an indication of dysfunction of small-bowel grafts. Digestion was less imparied if cyclosporine was applied, and part of the effects on digestion and protein balance could be attributed to the shortened bowel.

Animals↗
PubMed1990

[Immunization against blood group antigens by allogeneic bone transplantation].

33 bone allotransplants (cryopreserved) of AB0- and Rh-incompatible (donor-recipient) patients were performed to evaluate the question which AB0 Rh-incompatibility leads to immunization of the bone transplant recipient. Several different antibodies were tested pre- and postoperatively in the recipient. Regarding the Rh-system no immunization was demonstrable; however, a significant increase of antibody leads was found regarding the AB0-system. Thus, in bone bank techniques AB0 compatibility is important for allogeneic bone transplantation in young women. Otherwise, there is a risk for the development of MHN in case of pregnancy. Blood group-typing is not necessary in other patient groups. Although no Rh-antibodies were demonstrable, a similar mechanism can be postulated for the Rh-system. We, thus, conclude that in allogeneic bone tx in young women the Rh-system has to be taken into consideration.

ABO Blood-Group System↗
PubMed1990

[Bone healing--an immunoreactive process?].

Cell mediated immune reactions, demonstrated by leukocyte migration assay and histological analysis of spleen and lymph nodes, could be observed after fresh autografting of cortical segments in rats. The detected immune answer showed a bone-specific reaction pattern. In consideration of the temporal correlation of the observed immune reactions and the histological signs of graft incorporation, a connection of bone healing and immune system may be possible.

Animals↗
PubMed1990

[Orotracheal intubation in rats].

A detailed description of the technique of orotracheal intubation under visual control in rats is given. This method was used successfully in 190 animals, the complication rate being 3.2%. The hazards consisted of laryngospasm (1.6%) and fatal bleeding (0.5%). Intubation was proved to be a safe, reliable, simple and atraumatic way to establish a patent airway in this laboratory animal.

Animals↗
PubMed1989

Non-linear three-dimensional finite element analysis of a cementless hip endoprosthesis.

In this finite element study the stresses between a stem component of a cementless hip endoprosthesis (Young modulus of Co-Cr-Mo) and the human femur were calculated for two different loading types. Linear and non-linear models were used to simulate the interface implant bone. Two models, a stem with a porous coated surface over the entire length and a stem with a porous coated surface in the proximal region were compared regarding the load transmission to the femur. An additional calculation of an 'isoelastic' stem (Young modulus of cortical bone) was done to show the influence of the stem stiffness. A porous coated surface over the entire length causes principal shear stresses up to 2.75 MPa in the distal-medial region during level walking. The highest compressive stresses were calculated in the proximal-lateral region as 1.5 MPa in cancellous bone. A more physiological load transmission is obtained by limiting the coated area to the proximal region. All stresses in the two models are lower than experimentally evaluated strengths in the interface between implant and bone. A strong influence of the Young modulus of the stem material on the interface stresses was found. An 'isoelastic' stem causes compressive stresses in the proximal-lateral region whose values exceed the experimental strength of cancellous bone.

Biomechanical Phenomena↗
PubMed1989

[Material related aspects of surface structured endoprostheses].

In this article technical problems of surface-structured endoprostheses for cementless implantation are discussed. On the basis of four prostheses (two hip and two knee endoprostheses) various different porous coating technologies are compared. One sintered sphere layer, a cast sphere layer, a cast layer with "spongy-bone" structure and a plasma sprayed coating were compared. The quality of the bonding between the prosthesis and the porous surface layer was examined metallographically using polished specimens, with additional investigation of fraction surfaces of special tension test specimens. Additional information is given on the notch effect of the different coatings, in terms of a reduction in fatigue strength. The notch sensitivity differs for each material, and the reduction in fatigue strength is discussed for different implant alloys and different technologies for surface structuring. The investigation shows that the present quality of surface-structured endoprostheses is not satisfactory. We would like to thank the Dr. Johannes Heidenhain Foundation for financial support of this research.

Biomechanical Phenomena↗
PubMed1988

Laser induced shock wave lithotripsy--biologic effects of nanosecond pulses.

Laser energy of a Nd-YAG laser (1064 nm. wave length, 8 nsec pulse duration) was directed against various tissue cultures and the urothelium of the ureter, bladder and kidney parenchyma in pigs. Single pulse energy was 50 to 120 mJ with a repetition rate of 20 Hz. Urothelium and kidney parenchyma were irradiated in seven pigs. Tissue samples were examined histologically and electron microscopically directly, two, four, eight and 12 days after irradiation. No macroscopic lesion could be found. Maximum energy caused a small 'rupture cone' of 40 micron. depth. No thermic effects or necrosis resulted, so that no harm is to be expected with unintentional irradiation during laser stone disintegration.

Animals↗
PubMed1988

An evaluation of retrieved UHMWPE hip joint cups.

In this study it is demonstrated that the combined chemical and mechanical influences of the implant situation cause property changes of ultra-high-molecular-weight polyethylene (UHMWPE) hip joint cups. Nearly 250 loosened hip cups, retrieved 3 weeks to 14 years after implantation, were investigated. The clinical long-term behavior of various shaped polyethylene hip sockets are statistically analyzed. The main damage features were defined and described. Density measurements show a density increase with implantation time and a dependence of these changes from implant position and loading conditions. The rate of extractable constituents also increases with course of time. An increased in vivo conditioned oxidation of the UHMWPE can be demonstrated by infrared (IR) spectrometry. The density increase can be explained by post-crystallization, which is the result of oxidative chain scission. This leads to a reduction of the average molecular weight of the PE and to an increased extractability of constituents. Since these changes have been recognized as the reasons for aging and failing of UHMWPE, the methods of material characterization used in this study for retrieved implants will help to develop suitable in vitro testing and simulating methods. Characteristic damage features of hip cups allow direct relationships with construction characteristics and their improvement.

Hip Prosthesis↗
PubMed1987

Animal experiments on hemostasis with a collagen-fibrin tissue-adhesive sealant in the nephrostomy tract.

After a median laparatomy, nephrostomy was performed on 22 porcine kidneys: puncture, dilatation and introduction of a 26-French operating sheath through the parenchyma into the renal pelvis. At the end of the operation, an 8-French nephrostomy catheter prepared with a collagen-fibrin tissue-adhesive sealant was introduced through the operating sheath and the sheath was afterwards extracted. The hemostasis in the nephrostomy tract was very good in all 22 cases. There were no complications such as wound infection or stone formation during a post-operative period of between one and 95 days. Experimental investigations showed severe bleeding in nontamponade of the nephrostomy tract, in tamponade with an 8-French nephrostomy catheter and in tamponade of the nephrostomy tract with the collagen fleece wrapped around an 8-French nephrostomy catheter but not coated with the fibrin glue.

Animals↗
PubMed1987

[Morphologic examination of the urothelium after irradiation with laser energy].

The energy of a Nd-YAG laser (1,064 nm wave length, 8 ns pulse duration) was used to irradiate the urothelium of the ureter or bladder and kidney parenchyma in pigs. Single pulse energy was 50-120 mJ with a 20-Hz repetition rate. The horizontal laser beam was reflected 90 degrees down by a 100% mirror and with a specially designed apparatus focussed on the surface of the tissue. Laser light from a quartz glass fiber was also focussed directly onto the tissue. Urothelium and kidney parenchyma were irradiated in 7 pigs. Tissue samples were examined histologically and raster electron microscopically 2, 4, 8 and 12 days after irradiation. No macroscopic lesion could be found. Maximum energy caused a small cone of 40 micron depth. No thermic effects or necrosis resulted, so that no harm is to be expected with unintentional irradiation.

Animals↗
PubMed1987

Local hemostasis of nephrostomy tract with fibrin adhesive sealing in percutaneous nephrolithotomy.

In 26 patients percutaneous nephrolithotomy was carried out under local anesthesia with systemic sedation. Instead of the 25-French nephrostomy catheter used so far, a 5- or 10-French nephrostomy catheter prepared with a collagen-fibrin adhesive sealant was introduced into the nephrostomy tract. In all cases, excellent hemostasis was attained with the fibrin glue. In applying a fibrin glue, the danger of protracted venous or arterial hemorrhage from the parenchymal canal can be markedly reduced; the large-lumen nephrostomy catheter can also be dispensed with.

Aprotinin↗