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Biomedical subjects

H Kristen

Publications and source records attributed to H Kristen.

At least 19 recordsLinked to original sources
PubMed1998

Photometry and spectroscopy of the GRB 970508 optical counterpart

An optical transient within the error box of the gamma ray burst GRB 970508 was imaged 4 hours after the event. It displayed a strong ultraviolet excess, and reached maximum brightness 2 days later. The optical spectra did not show any emission lines, and no variations on time scales of minutes were observed for 1 hour during the decline phase. According to the fireball and afterglow models, the intensity should rise monotonically before the observed optical maximum, but the data indicate that another physical mechanism may be responsible for the constant phase seen during the first hours after the burst.

Journal Article↗
PubMed1992

Synthesis of a heteroglycuronan derivative containing the beta-D-galactopyranosyluronic acid (1-->3)-L-rhamnose repeating unit.

Helferich glycosylation of the cyanoethylidene L-rhamnose derivative 3 with the galactosyluronic bromide 2 gave the disaccharide 4 as a key intermediate in the synthesis of the monomer 13 for trityl-cyanoethylidene condensation (TCC). The following formation of the monomer 13, including introduction of a trityl group at O-3', proceeded in six steps. Because of the difficulty of some steps, an alternative route for 13 was tested. Model compounds 20, 21, and 22 were synthesized in order to confirm the stereoregularity of the products of the polycondensation. The polycondensation of the monomer gave D-GalpA-(1-->3)-L-Rha-oligomer derivatives consisting mainly of three repeating units. This result is in contrast with the degree of polymerisation (dp > or = 22) of other synthetic rhamnans, but is very similar to dp 2-7 of homo- and hetero-glucuronan derivatives.

Carbohydrate Sequence↗
PubMed1991

Rotationplasty for limb salvage in the treatment of malignant tumors at the knee. A follow-up study of seventy patients.

Seventy patients who had a rotationplasty for treatment of a malignant tumor in the region of the knee (the femur or the tibia) between 1974 and 1987 were followed for two to thirteen years (mean duration of follow-up, four years). Forty-seven patients had a stage-IIB osteosarcoma; the remaining twenty-three patients had a malignant fibrous histiocytoma, a chondrosarcoma, a Ewing sarcoma, or a giant-cell tumor. The most severe postoperative complication was occlusion of the reanastomosed vessels (seven patients), leading to amputation proximal to the knee in three patients. Other complications were problems with wound-healing (eight patients), transient nerve palsy (five patients), irreversible nerve palsy (two patients), pseudarthrosis (four patients), and rotational malalignment (one patient). Late complications included eight fractures, two infections, two delayed unions, and one lymphatic fistula. More than half of the patients were free of complications related to the operative procedure. Forty-four of the patients who had a stage-IIB osteosarcoma could be followed, and their data were analyzed for survival statistics. These patients had a 58 percent rate of disease-free survival and a 70 per cent rate of over-all survival. One patient had a local recurrence five years after the operation.

Adolescent↗
PubMed1984

Thermography as a means for quantitative assessment of stump and phantom pains.

Exact differentiation into stump and phantom pain is required when pain is reported after amputation. In a majority of cases appropriate treatment can improve the pain. Thermography is simple and gives a good indication of the circulation in the stump without operative intervention. It provides a key to the nature of the pain in stump and phantom. Although typical patterns occur for pain in the stump or phantom, in this study the thermographic image could confirm the presence of phantom pain, but it could not rule out errors or false statements.

Adult↗
PubMed1981

Treatment of osteosarcomata of the distal femur by rotation-plasty.

Rotation-plasty was carried out on fifteen patients--10 male and 5 female patients aged between 6 and 32--with an osteosarcoma of the distal femur following resection of the tumor. In the operation the lower leg was rotated through 180 degrees after resection of the distal femur and knee joint so that the ankle joint was effectively turned into a "knee joint". The indication for this operation was initially limited to children for whom the only possible therapeutic alternative was a high above-knee amputation. The surprisingly good functional rehabilitation justifies the indication of this method as an alternative to an endoprosthesis or arthrodesis even for young adults. In spite of the cosmetically very unusual position of the foot, none of the patients has so far experienced psychological problems thanks to suitable guidance. Both from an oncological and psychological point of view, this method represents an extremely responsible operation and should therefore only be carried out by hospital departments specializing in the therapy of bone tumors.

Adolescent↗
PubMed1980

An analysis of 119 loosenings in total hip endoprostheses.

One hundred nineteen loosenings of Müller total hip endoprostheses are analyzed. These arise from 1,407 operations performed between 1969 and October 1977. Deep infections occurred in 7 cases (0.5%). Loosening after a minimum of 5 years occurred in 15.3%. Of these the stem only was involved in 73.7%, stem and socket in 11.8% and the socket only in 14.5%. Seventy-eight per cent of the loose femoral components had been implanted in a varus position, with a long neck showing a higher incidence of failure, along with cases of implantation for osteoarthritis with cystic changes of the femoral head. In six cases the femoral component broke. This occurred twice in the acetabular component. Pain and loosening seemed to occur at the same time, and was unusual more than 5 years after the operation. When loosening occurred later, it was frequently caused by a fall.

Accidents, Home↗
PubMed1979

[Reaction of connective tissue and striated muscle tissue to implanted ashwood (author's transl)].

In former experiments it could be shown, that new bone is formed around ashwood after implantation in the tibia of rabbits, in spite of a foreign-body tissue reaction. Equally prepared ashwood half-cylinders were now implanted in the soft tissue of rats and evaluated 2, 6, 12 and 30 weeks after implantation. Around the implants a foreign-body tissue reaction developed and demonstrates the hitherto insufficient preparation of the implants.

Animals↗
PubMed1979

[Investigation of bone growth into porous metal implants (author's transl)].

Stainless-steel cylinders of different pore size were implanted into the tibia, and small tubes, 500 micrometers diameter, of the same material into the iliac crests of 19 rabbits. It was found that after three weeks ingrowing bone tissue anchored the cylinders if the pore size was adequate. The same applied to the tubes. A stable implantation was the prerequisite for the ingrowth of fibre-bone trabeculae. Additionally, the use of fibrinogen adhesive system seems to be advantageous for this anchorage. These results were established by mechanical tensile tests and morphological examinations.

Animals↗
PubMed1979

The effects of dynamic loading on intracalcaneal wood implants and on the tissues surrounding them.

The dorsal parts of the calcanei of rabbits were resected and replaced with similarly-shaped implants made of ash wood. In each case the Achilles tendon was reinserted into the projecting part of the implant so as to subject the latter to the dynamic loads generated by use of the limb. The implants were removed from some of the animals after 5 weeks and from the others after 14 weeks. They were evaluated by preparing undecalcified microtome sections and ground sections which were examined by light microscopy and microradiography. Some of the animals underwent vital staining so as to produce polychromatic sequential labelling of the calcaneal specimens. In the area of insertion of the Achilles tendon soft tissue grew into the larger pores of the wood and, in some cases, differentiated into cartilage. Every implant remained stably anchored in the calcaneus. In every animal the intracalcaneal part of the implant became surrounded by new bone which was in direct contact with the surface of the implant and which also formed in the pores of the wood, even all rabbits loaded the operated foot. The formation of new bone in and around the implants demonstrates the basic feasibility of using ash wood as an isoelastic implant material in bone.

Achilles Tendon↗
PubMed1979

[Disarticulation in the knee joint (author's transl)].

Based on the results with thirty patients, disarticulation in the knee is to be recommended as a very good amputation level. Two groups of patients seem to be especially suitable for this amputation level: patients with malignant bone tumors of the proximal tibia or fibula and patients with peripheral vascular diseases. Above all, the easy operational technique and the functionally valuable long thigh stump offer decisive advantages as compared with amputation of the thigh. Problems with prosthesis fitting were solved through modification of the socket shape as well as new developments in artificial knee joints.

Adolescent↗
PubMed1978

[X-ray dose reduction in examination of infant's hip with image-intensifier-fluoroscopy-system (author's transl)].

An image intensifier--70mm camera--fluoroscopy system combined with a conventional X-ray tube is used for routine examination of the infant's hip. The high quality of 85% of these 70mm exposures makes immediate diagnostic interpretation possible. An even higher percentage can be achieved by most exact positioning of the patients. Apart from the radiation protection of the gonades, the X-ray skin dose of the primary beam is reduced by 90-95% compared with full size radiography using film screen combinations. This exposure technique can certainly be used not only for the examination of the infant's hip.

Fluoroscopy↗
PubMed1978

[Surgical treatment of the congenital femural defect by means of rotation plasty (author's transl)].

Experiences made in 5 cases with Borggreve's rotation plasty have shown that in cases of congenital femural defects and exceptionally also in malignant bone tumors of the distal femur this method should be suggested to the patient as a possible therapy. By rotating and shortening of the leg, the ankle joint is converted to a new knee joint. With this method an active movement of the knee joint can be obtained, so that the fitting with a below knee prosthesis becomes possible.

Abnormalities, Multiple↗
PubMed1977

[Biocompatibility of wood in bone tissue (author's transl)].

Alcohol-extracted and sterilised cylinders of ash- and birchwood were implanted into the tibia of rabbits. The selection criteria of these two wood species were thoroughly described. 28 implants were evaluated after 3, 5, 14 and 32 weeks using undecalcified microtome sections and ground sections employing polychromatic sequential-labelling and microradiography. In spite of a foreign-body-tissue reaction new bone is formed around the implants and within the pores of the wood as well. Both wood species therefore seem to be suitable implant materials, which were anchoraged by the bone itself. A tensile strength and elastic properties comparable to bone and simple handling would be the advantages of this material.

Animals↗