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Biomedical subjects

C P Klein

Publications and source records attributed to C P Klein.

At least 55 records · Page 3Linked to original sources
PubMed1989

Macroporous calcium phosphate bioceramics in dog femora: a histological study of interface and biodegradation.

This study examines the biodegradation behaviour of calcium phosphate macroporous bioceramics consisting of hydroxylapatite or beta-whitlockite implants. The implantations were performed in hard tissue of femora and muscular tissue of dogs for periods of 6 and 12 month. With microradiography and light microscopy, respectively, of ground and thin sections it was shown that hydroxylapatite remained unchanged and beta-whitlockite degraded within 6 month in bone tissue. In the muscular tissue, the biodegradation of beta-whitlockite was slower. In addition, beta-whitlockite gave rise to a cellular response of lymphocytes and plasma cells rather than hydroxylapatite in the soft tissue region. For tissue response hydroxylapatite is more suitable as an implant material than beta-whitlockite.

Animals↗
PubMed1989

Rib fracture healing after osteosynthesis with wire mesh titanium and screws: a histological study in sheep.

Twenty sheep were placed under general anesthesia and five ribs (6-10) were transected at their lateral angle using a pair of rib shears. The fractures were stabilized by titanium wire mesh plates. After 4, 6, 8, 10 and 12 weeks groups of 4 animals were sacrificed and rib samples were prepared for histological examinations. The study showed that the osteosynthesis stabilized the fractures and that the healing is similar to untreated rib fractures. This osteosynthesis method is a good contribution to severe injured chest treatment.

Animals↗
PubMed1988

Bonding of bone to apatite-coated implants.

Implants of solid sintered hydroxyapatite form very tight bonds with living bone, but are susceptible to fatigue failure. This problem can be overcome by using plasma-sprayed apatite coatings on titanium implants. A very strong bond is formed between bone and this composite material; this was studied in canine bone with plug implants, avoiding any mechanical retention. Mechanical testing showed an interface shear strength at six weeks of 49 MPa with a maximum of 64 MPa after six months. There was histological evidence of direct bonding between the apatite coating and living bone while uncoated control plugs were easily extracted. The results indicate that apatite-coated implants can form a chemical fixation with a strength comparable to that of cortical bone itself. This fixation is far stronger than that provided by current cemented or uncemented fixation techniques.

Adhesiveness↗
PubMed1988

A simple method for preparing thin (10 microM) histological sections of undecalcified plastic embedded bone with implants.

A simple method for preparing undecalcified thin sections of bone with implants has been developed. After exposing a surface of bone and implant in a plastic block by sawing thick sections, the surface is stained prior to making a thin section. A glass coverslip is affixed with a thin layer of cement to the stained surface to stabilize the tissue and implant during sectioning. A mixture of glycerine and water is used as a coolant and lubricant. The orientation in situ is preserved allowing demonstration of bone architecture and cells, and the tissue-implant interface.

Animals↗
PubMed1987

Plasma sprayed coatings of hydroxylapatite.

The technique of plasma spraying has been applied to deposit a thin, dense layer of hydroxylapatite onto a titanium substrate. Bond strength of such apatite coatings with the substrate have been measured, as well as the (absence of) influence of the coating process on fatigue properties of the substrate. Animal studies showed similar histological reactions to apatite coatings as to (well documented) apatite bulk materials.

Animals↗
PubMed1987

Comparison of calcium phosphate glass ceramics with apatite ceramics implanted in bone. An interface study--II.

In order to study bone tissue interaction on calcium phosphate glass ceramics and on apatite ceramics, cylinders of standard size were implanted in the tibiae of rabbits. The materials were evaluated by radiography, light microscopy and microradiography. Apatite ceramics gave rise to a very close contact with new bone. Glass with an apatite surface evoked bone growth similar to that for apatite ceramics but with a loose contact while glass without an apatite surface gave rise to porous remodelling of new bone without close contact to the implant.

Animals↗
PubMed1987

SDS-PAGE analysis of the protein layers adsorbing in vivo and in vitro to bone substituting materials.

The composition of the protein layer adsorbed to the bone substituting materials, hydroxyapatite, beta-whitlockite, titanium and aluminium, in vivo (intramuscularly in guinea pig) and in vitro, was investigated using SDS-gel electrophoresis (SDS-PAGE). After in vivo implantation for 1 d mainly proteins with molecular weights between 10,000 and 20,000 were adsorbed. After 3 months the biolayer of the implanted biomaterials also contained proteins with molecular weights 35,000, 45,000, 60,000 and 200,000. No large qualitative differences in protein composition of the biolayers on the various implanted materials were found. In vitro incubation with human serum resulted in binding of proteins with estimated molecular weights of 30,000, 60,000 (albumin), 200,000 and greater than 200,000. It is suggested that the differences between in vivo and in vitro protein adsorption are due to proteolysis occurring in vivo in the vicinity of the implanted material.

Adsorption↗
PubMed1987

Chemical implant fixation using hydroxyl-apatite coatings. The development of a human total hip prosthesis for chemical fixation to bone using hydroxyl-apatite coatings on titanium substrates.

Sintered hydroxyl-apatite implants form very tight bonds with living bone but are susceptible to fatigue failure. Plasma-sprayed apatite coatings on titanium substrates overcome the fatigue problem. The static tensile substrate bond strength of the apatite coating is in excess of 85 megapascals (MPa) (12,000 psi). In a plug implant study designed to discount mechanical retention, a bone bonding shear strength of 64 MPa (9280 psi) was achieved, comparable to the strength of cortical bone. Histologic sections confirm the close bonding between apatite coating and living bone. In a canine total hip arthroplasty study, the apatite-coated implants proved far superior to the uncoated controls. Uncoated prostheses were surrounded by fibrous tissue and were easily extracted from the femur at any postoperative time. The apatite-coated implants were rigidly fixed within three weeks with demonstrable bone formation up to the implant surface. Bony defects up to 2 mm in depth were filled with bone within six weeks. The hypothetical mechanism of bone bonding is chemical. Hydroxyl-apatite coatings permit an implant fixation far superior to current methods using either cemented or cementless techniques. The plan is to study a human total hip prosthesis with hydroxyl-apatite coating for chemical fixation to bone.

Animals↗
PubMed1986

A comparative study of different beta-whitlockite ceramics in rabbit cortical bone with regard to their biodegradation behaviour.

Different beta-whitlockite ceramic cylinders of standard size were implanted in the tibiae of rabbits to study the influence of micropores and chemistry on the biodegradation rate. The materials were evaluated by radiography and light microscopy. Surface chemistry was varied by the addition of impurities, while different applied pressures before sintering and different sintering temperatures gave rise to different micropores. Both factors influenced the biodegradation rate.

Animals↗
PubMed1986

Granuloma and plasma cell formation induced by the subcutaneous implantation of beta-whitlockite particles.

In this paper, the formation of a granuloma following subcutaneous implantation of beta-whitlockite powder is described. The implants were removed after 3, 5 and 7 wk and examined histologically. In the granuloma giant cells, macrophages, lymphocytes and plasma cells are present. The presence of plasma cells indicates that not only inflammation occurs, but that an immunoresponse also takes place. Resorption and phagocytosis of particles was observed and the particles were found in the regional lymph nodes after 7 wk. beta-Whitlockite powder induces an inflammation and both a cellular and a humoral immunological response, when implanted subcutaneously.

Animals↗
PubMed1985

[Spironolactone in the treatment of portal hypertension in liver cirrhosis. A new therapeutic principle?].

Five patients with liver cirrhosis, portal hypertension and oesophageal varices received spironolactone in daily doses of 50-200 mg. Measurements of hepatic vein occlusion pressure at intervals of 1 to 5 months showed a pressure reduction of between 9 and 11 mm Hg. Thus the pressure lowering effect of spironolactone is about the same as that of beta-blockers. Since spironolactone is without the well known side effects of beta-blockers this therapeutic approach has wide application in the long term drug therapy of portal hypertension.

Blood Pressure Determination↗
PubMed1985

Interaction of biodegradable beta-whitlockite ceramics with bone tissue: an in vivo study.

The biodegradation of different porous beta-whitlockite materials are studied by in vivo experiments, radiographic follow-ups and light microscopy observations. The materials were implanted in rabbit tibiae for 16 month. Micropores play an important role in the biodegradation rate. The resorbing materials evoke an inflammation with plasma cells. The resorption starts in the medulla, and the phagocytosed particles are removed to the lymph nodes. Normal bone function can be restored after all the implant material is resorbed.

Animals↗
PubMed1984

Relationship between the degradation behaviour of calcium phosphate ceramics and their physical-chemical characteristics and ultrastructural geometry.

The neck geometry of different calcium phosphate materials was studied by scanning electron microscopy. The dissolution rate of these materials, especially of the necks, was determined by chemical analysis. The degradation of calcium phosphate materials in lactate buffer, related to the detachment of sintered particles, was found to be determined by neck dissolution rate and neck geometry. The latter factor depends on the crystallography and stoichiometry of the material and the sintering conditions.

Biocompatible Materials↗
PubMed1983

Biodegradation behavior of various calcium phosphate materials in bone tissue.

In order to study the biodegradation behavior of calcium phosphate materials, cylinders of standard size were implanted in the tibiae of rabbits. Material parameters were stoichiometry (hydroxyapatite with a Ca/P ratio of 1.67 versus tricalcium phosphate with a Ca/P ratio of 1.50), crystallographic structure (apatite versus beta-whitlockite), microporosity, and macroporosity. The extent of biodegradation was evaluated by radiography, light and fluorescence microscopy, microradiography, and porosity measurements. All calcium phosphate materials were biocompatible in bone tissue. Hydroxyapatite ceramics had a higher osteogenic potential than beta-whitlockite materials. Depending on their porosities, sintered tricalciumphosphate (beta-whitlockite) materials were more or less biodegradable, in contrast to sintered hydroxyapatite materials, which showed no detectable resorption over a period of 9 months of implantation.

Animals↗
PubMed1983

Activation of complement C3 by different calcium phosphate powders.

The ability of different calcium phosphate to activate the complement system is studied by crossed immunoelectrophoresis demonstrating conversion of C3 to C3b. Complement consumption is determined by a haemolytic assay CH50. Hydroxyapatite powders after sintering induce a significant conversion of C3 and reduction of CH50 value. However the complement system is not activated by sintered tricalciumphosphate (beta-whitlockite). This is not related to the adsorption behaviour; it depends neither on chemical composition nor on crystal lattice. It is argued that C3 conversion is not triggered by the convertase of the classical pathway.

Calcium Phosphates↗