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Biomedical subjects

S Stea

Publications and source records attributed to S Stea.

At least 73 records · Page 4Linked to original sources
PubMed1994

Cytotoxicity testing of cyanoacrylates using direct contact assay on cell cultures.

The use of a tissue adhesive for surgical procedures has prompted a large number of clinical and experimental studies. Alkyl-2-cyanoacrylate esters constitute a family of adhesives with good mechanical properties but their biological compatibility has to be assessed. In this study the cytotoxicity of three commercially available cyanoacrylates and one of unknown composition has been determined. The first part of the study deals with direct contact testing procedures using L 929 cells challenged with drops of adhesives: cell morphology, cell growth and bacterial growth inhibition were assayed. Testing methods included cell viability assay using vital dyes, cell growth measurement using crystal violet staining uptake and bacterial growth assay using S. aureus growth inhibition. All the cyanoacrylate adhesives tested were found to be cytotoxic and to inhibit cell proliferation: differences between the cyanoacrylates were found.

Adhesives↗
PubMed1994

Toxicity of cyanoacrylates in vitro using extract dilution assay on cell cultures.

Comparative cytotoxicity testing of four cyanoacrylate adhesives suggested for orthopaedic applications was performed. These substances were placed in complete culture medium with serum and the resulting extraction fluids were tested on L 929 cells and human lymphocytes. Testing procedures include cell morphology assessment using light microscopy and vital dyes, cell counting using a computer-assisted image analysis system, cell growth measurement using total protein content assay and cell viability assessment using the MTT method. Quantitation of the toxicity of the degradation products released by cyanoacrylates in the extracts was achieved and differences in the cytopathic effect related to the chemical composition of the cyanoacrylates were found. A toxicity rating of the assayed cyanoacrylate adhesives was obtained as follows (in order of increasing toxicity): BCA < xCA < ECAg < ECAl.

Adhesives↗
PubMed1994

Cell culture methods for testing biocompatibility.

Cell culture systems may be of value in testing the biocompatibility of prosthetic materials before they are introduced into clinical use. In recent years, in vitro methods for assaying biomaterials have gained in importance owing to the growing concern over the use of animals for biomaterials testing. Significant effort is therefore being focused toward developing predictive and quantitative, but also simple and reliable, methods of testing using cultured cells. At present, a number of methods for measuring both the cytotoxicity and the specific cytocompatibility of different materials are available. The usefulness of these systems is no longer confined to screening new materials; they can be used to study the mechanisms of action of various materials during tissue/material interaction. This paper reviews the published literature on the use of cell culture models in evaluating biocompatibility and reports on the personal experience of the authors, who have been using cell culture systems for many years and for different purposes.

Biocompatible Materials↗
PubMed1994

Bone demineralization induced by cementless alumina-coated femoral stems.

The biologic compatibility of ceramic materials has been widely demonstrated, and alumina (Al2O3) has been used extensively in clinical applications for nearly 20 years. The authors examined the behavior of bone tissue adjacent to the alumina coating in eight cementless hip prosthetic stems that appeared radiologically stable and were explanted because of pain. Histologic evaluation demonstrated the presence of a consistent layer of decalcified bone tissue in continuity with and parallel to the prosthetic interface. Based on laboratory findings, the authors attribute this demineralization phenomenon to a high local concentration of aluminum ions with metabolic bone disease, which is histologically comparable to the osteomalacic osteodystrophy described in dialysis patients. These findings must be carefully considered given the potential long-term implications for alumina-coated implants.

Aged↗
PubMed1994

Surgical repair of achilles tendon ruptures using polypropylene braid augmentation.

Surgical repair in fresh rupture of the Achilles tendon should be considered in active patients and athletes to restore their preinjury level of activity. Fifteen cases of Achilles tendon rupture underwent surgical repair using interpositional augmentation. This technique provides an immediate mechanical strength of the repair, avoiding the need for a postoperative plaster cast and allowing immediate motion of the ankle. No wound infection, scar adherence of the skin to the tendon, or rerupture of the tendon is present in this series. All patients were subjectively satisfied with the results and returned to their preinjury level of activity. Objectively, isokinetic assessment revealed no significant difference, as per t-test evaluation (P < .05), between the operated leg and the controlateral one.

Achilles Tendon↗
PubMed1993

X-ray diffraction of newly formed bone close to alumina- or hydroxyapatite-coated femoral stem.

The study was focused on the bone tissue response to two types of ceramic coating [alumina and hydroxyapatite (HA)] obtained with a plasma-spray technique. The HA coating was performed on titanium stems, while the alumina coating was on chromium-cobalt-molybdenum stems. The investigation was carried out by means of micro-area X-ray diffractometric analyses and microdiffractometric analyses at the bone-implant interface. Moreover, the coating before and after implantation was analysed by means of the conventional powder X-ray diffractometric technique. This study demonstrated that 1 yr after implantation in animals the newly formed bone adjacent to the HA-coated hip prosthesis stems was mineralized as much as the pre-existing bone, while 24-64 months after surgery in humans the newly formed bone close to the alumina-coated hip prosthesis stems showed a lamellar and Haversian structure strongly demineralized, probably due to the release of aluminum ions from the alumina covering. The authors conclude that the X-ray diffraction allows the evaluation of the structural modifications of the ceramic coating, the bone formation rate close to the coating and the chemical nature of the particles released from the coating.

Aluminum Oxide↗
PubMed1993

Morphometric and microanalytical analyses of alumina wear particles in hip prostheses.

We analysed tissues harvested during 24 retrievals of hip joint prostheses, with one or both articular components made of alumina. We describe the morphology of wear particles, measure their size and analyse their chemical composition. We relate histopathological aspects to the parameters that characterize ceramic wear particles, and notice that tissue reaction relates to the physical aspect and amount of wear debris and does not necessarily depend on their chemical composition.

Aluminum Oxide↗
PubMed1993

[Assessment of the plasma phase of coagulation in platelet-rich plasma after passage through a special polyester filter].

The authors have examined the alterations in the coagulation pathway of plasma filtered through a polyester filter coated by a hydrophilic polymer. The activation of the coagulation pathway was evaluated by measuring prothrombin time, activated partial thromboplastin time, coagulation factors and fibrinopeptide A. The results obtained demonstrate that the examined filter does not induce significative activation of the coagulation pathway.

Blood Coagulation↗
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↗
PubMed1991

Cellular events in the mechanisms of prosthesis loosening.

The functional restoration of a joint damaged by trauma or disease is obtained by prosthetic surgery. In particular the implantation of hip prostheses is regarded as routine in orthopedic surgery and thorough research has been developed in this field. The prosthetic replacement of the knee and even more so the ankle and elbow occurs less frequently in clinical practice and has been studied less intensively. The results of artifical hip replacement are generally good, both in terms of pain relief and the restoration of satisfactory joint function. Nevertheless, as time passes, a high rate of failures have been recorded due to prosthesis infections, fracture and wearing of the prosthetic components and prosthesis loosening by various causes. The use of ultra-filtered air and laminar flow in operating theatres and antibiotic prophylaxis have dramatically reduced the incidence of infections in total hip arthroplasty. Thanks to the setting up of new stem configurations and the use of superalloys that are highly resistant to fatigue failure, the fracture of the femoral component has been virtually eliminated as a complication of total hip arthroplasty replacements. Loosening is thus the most frequent complication in total hip replacement.

Bone Cements↗
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↗
PubMed1988

Results of histological grading on 100 cases of hip prosthesis failure.

One hundred cases of hip prosthesis failure were classified on the basis of the different types of tissue reaction occurring around alloplastic material. The results revealed infectious phlogosis in 32% of the cases, phlogosis due to wear in 42%, phlogosis due to allergy in 1% and mixed phlogosis in 25%. The distribution of the type and degree of intensity of the phlogosis, in relation to the duration of the implant, is also highlighted. This new grading technique yields reproducible results.

Biocompatible Materials↗