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Biomedical subjects

S Stea

Publications and source records attributed to S Stea.

10 recordsLinked to original sources
PubMed1992

Microradiographic and histochemical evaluation of mineralization inhibition at the bone-alumina interface.

Microradiographic and histochemical tests were used to examine the behaviour of the bone tissue close to the alumina coating in cementless hip prostheses which were radiologically stable and explanted because of pain. The presence was detected of a decalcification stripe of the bone tissue with a thickness of about 300 microns, parallel to the prosthesis profile and in appearance not influenced by the roughness of the surface. This phenomenon was attributed to the presence of aluminium ions similarly to what happens in osteomalacic osteodystrophy in nephropathic dialysed patients. It was concluded that the phenomenon must be carefully considered because, in the long term, it could cause failure in the alumina coating.

Aluminum↗
PubMed1990

[Palatine torus. Clinical picture and etiopathology].

In this note the Author deals with the so-called "torus palatinus", namely a hyperostosis, which develops very slowly, set on the median line of the palate; it usually develops during the years of youth and doesn't normally require surgical treatment because, as soon as it settles, it will not grow any more. Its surgical removal is needed only in some rare cases, when it does not allow the placing of a prothesis or when the mucosa covering it undergoes ulcerous pathology.

Humans↗
PubMed1990

[The oxidative burst in the determination of immune response to synthetic materials].

Macrophages play an important role at the implant-tissue interface. Their activity is extremely complex but above all they are phagocytic cells. Phagocytosis is accompanied by a sequence of biochemical reactions known as "the oxidative burst" (BO). The fundamental physiological significance of this phenomenon is to provide the phagocytes with an efficient microbicidal mechanism. Our aim was to prepare an objective method for screening biomaterials that could influence macrophagic defence mechanisms against a possible implant contamination.

Animals↗
PubMed1989

Comparative study of the thromboresistance of Dacron combined with various polyurethanes.

In vitro tests were carried out on Dacron samples differently knitted and on Dacron vascular prostheses coated with various urethanes. All the materials were put in contact with human platelet-rich plasma; the subsequent assay of three platelet released substances, i.e. beta-thromboglobulin, platelet factor 4 and thromboxane B2, as well as the quantification of platelet retention, were used to establish the degree of thrombogenicity of the material itself. In some cases Dacron-urethanes composites showed better thromboresistance than any other materials conventionally used in vascular surgery.

Biocompatible Materials↗
PubMedDate not supplied

Cellular reactions in hip prosthesis loosening.

Based on the results obtained in histological examinations carried out on periprosthetic tissues in a large series of cases of prosthetic hip joint explants, the authors analyze the cellular events that may occur in loosening phenomena as compared to what occurs in the paraphysiological repair process that is observed in the stable prosthesis. Like other authors, they believe that the principal role in the mechanism of loosening is played by macrophages which are recalled in a large number, at times together with multinucleate giant cells, at the bone-implant interface, after micromovements of the prosthesis and the formation of wear particles have occurred. The macrophages would be capable of favoring resorption of the periprosthetic bone tissue, producing areas of osteolysis in which the transmission of the mechanical stress of loading is modified. The ensuing prosthetic instability increases wear phenomena, causes a greater amount of osteolysis, and, in a vicious cycle, loss of the relationship between bone and implant, and, thus, prosthetic loosening. Finally, the authors report a hypothesis on the pathogenesis of the phenomenon, based on which non-physiological stress, associated with wear and eventually infection, leads to loosening.

Bone Cements↗
PubMedDate not supplied

Considerations on ceramic prosthesis explants.

The authors report data obtained for 11 cases of explants of prostheses having ceramic joint surfaces. The wear phenomena observed in 9 prostheses, including 1 case with breakage of the ceramic head, was moderate: 20-22,000 debris per mu 2. In 2 cases the wear was massive, with a concentration of debris in the peri-implant tissues 5-10 times greater (100,000-218,000 debris per mu 2). An explanation for the trigger mechanism of wear phenomena is proposed: the cases of massive wear are related to loosening of the acetabulum. A histological examination of the bone tissue surrounding a stem covered with alumina (Al2O3) carried out in three cases allowed us to observe an area of demineralization measuring approximately 500 mu of tissue in contact with the ceramic coating. The osteomalacia could be caused by the diffusion of alumina ions.

Bone Cements↗
PubMedDate not supplied

An evaluation of the "in vivo" and "in vitro" biological reaction and mechanical features of carbon fibre composites.

Tissue reaction to an epoxy resin-carbon fibre composite was tested "in vivo" and "in vitro" in order to evaluate this material as an alternative to metal alloys for clinical use in orthopaedic surgery. While the "in vitro" tests suggest a mild toxic effect of the composite on cells, good biocompatibility "in vivo" was observed when debris are not generated. The mechanical tests compared the composite and stainless steel plates, confirming the expected values for static strength and elastic modulus, revealing, however, the formation of long needles of carbon fibre following breakage of the plate.

Animals↗