PubMed Health⌕ Search

Biomedical subjects

A Pizzoferrato

Publications and source records attributed to A Pizzoferrato.

At least 19 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↗
PubMed1992

Metabolic changes in bone in old age.

The authors conducted a study on the effect of aging upon the factors which regulate calcium metabolism. Hormonal and biochemical tests were performed on samples from patients selected on the basis of sex, age, and other characteristics in order to determine the trend of these regulatory factors in middle and old age, with particular attention to osteoporosis in women. The authors propose several theories regarding the pathogenetic mechanisms of osteoporosis on the basis of this study as well as the literature.

Adult↗
PubMed1992

[In vitro and in vivo evaluation of the blood-biomaterial interaction].

The Authors, after a short description of the phenomena following the interaction between blood and biomaterials, take into consideration the different methods used in studying the in vitro, in vivo and ex vivo hemocompatibility, as well as the problems involved by each method and its contribution to the knowledge of hemocompatibility. The Authors report their experience on the in vitro study of the effects induced by some biomaterials on platelets and coagulation factors.

Animals↗
PubMed1992

In vitro methods to evaluate metal-cell interactions.

The aim of this study was to test different metals, widely employed in constructing prosthetic devices, by in vitro methods. Biological effects of such materials were analyzed through four different assays on human lymphocytes and granulocytes. The lymphocyte proliferation assay gave quantitative results, while the viability test showed the morphological appearance of the cells correlated well with previous results. NK cytotoxicity and granulocyte chemokinesis tests provided interesting data on leucocyte performance when challenged with metals. Therefore the present study adds new basic information on cell behaviour when metal products are present in the body, e.g. around devices implanted in human tissues.

Biocompatible Materials↗
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↗
PubMed1987

Evaluation of autologous cancellous bone grafting of mandibular discontinuity defects in dogs using a Dacron-urethane prosthesis.

Reconstruction of 2 cm discontinuity defects using autologous cancellous bone chips and a Dacron-urethane prosthesis was evaluated in four canine mandibles. Histologic studies were performed on specimens taken six and 12 months after bone grafting. All four grafts were completely incorporated, producing a reconstruction that conformed precisely to the desired shape. Remodeling resulted in a trabecular pattern similar to that of the normal mandible. The prosthesis was well tolerated and did not elicit an inflammatory response.

Animals↗
PubMed1986

Postoperative irradiation of fresh autogenic cancellous bone grafts.

Discontinuity defects were created in the mandibles of dogs and then reconstructed immediately with fresh autogenic cancellous bone grafts and Dacron-urethane prostheses. The grafts were irradiated to a total dose of 5000 rads after waiting intervals of between 3 and 12 weeks. Nonirradiated grafts served as controls. The grafts were evaluated clinically, radiographically, and histologically. There was complete incorporation of all grafts, regardless of the interval between surgery and radiotherapy. There were no soft-tissue complications. The controls were distinguishable from the irradiated grafts only by the presence of hematopoietic bone marrow. Fibrofatty marrow was observed in the irradiated grafts. Theoretical support for this technique is found in the biology of cancellous bone grafting and the pathology of radiation injury. In view of the difficulties associated with mandibular bone grafting in preoperatively irradiated patients, a new method of reconstructing selected cancer patients who require both mandibular resection and radiotherapy is suggested.

Animals↗
PubMed1985

Prosthetic replacement of large defects of the cervical trachea in dogs.

Surgical resection and replacement of a segment of the cervical trachea was performed in 8 mongrel dogs. The replacement was with a porous prosthesis made of Dacron cloth mesh stiffened with a heat-curing polyetherurethane. Ten tracheal rings were resected in each animal to create a complete circumferential defect of the trachea measuring 7 or 8 cm in length depending on the size of the dog. Animals were sacrificed periodically from 3 to 27 months post-reconstruction. The luminal surfaces of the reconstructed tracheae showed respiratory epithelium.

Animals↗
PubMed1979

Evaluation of the tissue response to the wear products of the hip joint endo-arthroprosthesis.

The causes of tissue reaction surrounding heterogeneous materials are: cell-mediated hypersensitivity due to an implant material; infection; post-surgery hematoma, following lysis of red cells and deposition of hemosiderin; "True" implant reaction, i.e., tissue modifications produced by wear particles of components of the prosthetic devices used. The stages of inflammation due to wear particles are: phagocytosis of particles by newly formed fibrous capsule cells; lymphatic drainage of particles through the newly formed joint capsule; granulation tissue reaction in the internal surface of the joint capsule which stores non-removed particles from inadequate drainage; necrosis of granulation tissue in contacting the artificial joint surface; formation of free masses of necrotic tissue in the joint cavity; formation of new granulation tissue due to these necrotic masses and by wear particles liberated from them (the beginning of a vicious cycle); insufficient storage by granulation tissue; formation of "auxiliary" granulation tissue in the fibrous layer of the bone-cement interfaces and in the R.E.S. of the bone-marrow; bone resorption and its replacement by granulation tissue; loosening of the prosthesis.

Acetabulum↗
PubMed1979

Preliminary histologic evaluation of a biocompatible mesh for tracheal reconstruction.

The purpose of this study was to evaluate a porous Dacron - urethane mesh tracheal prosthesis in large dogs with surgically created discontinuous defects of the cervical trachea. Some protheses were carbon coated in an attempt to improve biocompatibility. Histology was performed on 2 dogs. The mucosa regenerated entirely covering the prosthesis. Respiratory epithelium was formed over a large central portion of the tracheas.

Animals↗
PubMed1977

Evaluation of hip arthroprostheses by means of body environment simulators.

Laboratory tests carried out by means of body environment simulators have proved to be very important for the evaluation of endoprostheses potentially useful for implantation. The present paper examines the problems connected with the design of such a simulator. The results obtained with an initial, very primitive simulator concerning the outlines of the phenomena of wear, corrosion, and friction and some wear properties of commercially available hip endoprostheses are presented. From these results, the motivation that led to the design of a more advanced simulator is presented. This latter simulator is also described.

Corrosion↗
PubMed1975

Thermodifferential analysis of ceramic implants.

Ceramic pelletes (in Al2O3 92% and in calcium aluminate) implanted into the muscles of rabbits for varying periods of time, and samples of similar material, not implanted but mixed with organic substances, have been analyzed by means of thermal differential analysis (TDA). Which hydrated calcium aluminates are formed from implants after contract with the tissue fluid, has been established. It has also been ascertained that the ceramic implants absorb organic substances from the tissue fluid, which, from a first evaluation, seem to be composed of simple molecules. The results of this initial inquiry have provided positive indications of the utility of TDA to assist in elucidating the phenomena that occur between implant and tissue.

Absorption↗
PubMedDate not supplied

[Dental implantations of ceramics-coated metals].

Recent studies and personal experience of the Authors in the field of dental implants have encountered the same fundamental problem which arises with orthopedic prosthesis procedures. The basic problem is that of adhesion between the bone tissue and the metal implant. Chrome-cobalt alloy, Tantalum and Titanium are the metals of most recent use. The Authors therefore proceeded to investigate the behaviour of alveolar bone tissue in the proximity of artificial teeth made of alloy (platinum-gold) covered with ceramic, as used in prosthetic dentistry. The experiment was carried out in a dog and a man. In the dog, two of its mandibular teeth were substituted with the same ceramic-gold implants: the first, a replica of natural tooth, was placed in the socket and held in place by metal splint and mandibular circumferential wirings. The other implant, without a replicated crown, was left free, within the alveolus, without contacting the near or opposing teeth. A solid smooth surfaced alumina device, shaped like a small cylinder, was implanted in the upper femoral epiphysis of the same animal.

Alveolar Process↗
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↗