Biomedical subjects

S Affatato

Publications and source records attributed to S Affatato.

25 records · Page 2Linked to original sources

PubMed1999

Mixed oxides prosthetic ceramic ball heads. Part 1: effect of the ZrO2 fraction on the wear of ceramic on polythylene joints.

Although mixed oxides ceramics have been indicated in the literature as a promising compromise between strength and wear, to the authors' knowledge no reports are available on the influence of the percentage of zirconia in ceramic femoral heads when sliding against polyethylene cups. Two types of mixed oxides ceramic ball heads (alumina plus, respectively, 60 and 80% of zirconia) were compared to pure zirconia and pure alumina heads in terms of wear behaviour against UHMWPE in a hip joint simulator. Polyethylene cups and ceramic femoral heads were fixed on a simulator apparatus with a sinusoidal movement and load in presence of bovine calf serum. The experimental results did not show significant difference between the two experimental ceramic materials or in comparison with pure materials. Considering that all specimens, regardless of the material, had the same level of surface roughness, this roughness factor seems to have a more relevant role than the mix of oxides used to manufacture the ceramic head. Wear tests are conducted on materials used in prosthetic hip implants in order to obtain quality control and to acquire further knowledge of the tribological processes that involve joint prostheses, therefore reducing the risk of implant failure of innovative prostheses.

Animals↗

PubMed1999

Mixed-oxides prosthetic ceramic ball heads. Part 2: effect of the ZrO2 fraction on the wear of ceramic on ceramic joints.

Three different types of mixed-oxides ceramic ball heads have been investigated for their wear behaviour against acetabular cups of the same materials in a hip joint simulator. Mixed-oxides ceramics have been indicated in literature as a promising compromise between strength and wear but no reports are available on the influence of a percentage of zirconia in a ceramic femoral head when sliding against itself. Mixed-oxides ceramic acetabular cups and femoral heads were tested on a simulator apparatus with a sinusoidal load in presence of bovine calf serum. The experimental results did not show any significant difference between the experimental and commercial ceramic material couplings. These results were found to be in accord with those developed in Part 1.

Acetabulum↗

PubMed1999

Hip prothesis: an in vitro wear protocol based on a comparison between gravimetric and profilometric analysis.

Ultra high molecular weight polyethylene acetabular cups were analysed by means of a shadowgraph method (using a profile projector) to measure linear wear. The results were compared with those of previous wear tests performed on a hip joint simulator. Twelve polyethylene acetabular cups were analysed. The specimens were evaluated visually for evidence of polyethylene wear. Examination of the polyethylene inner surface did not reveal evidence of surface failure such as delamination, fatigue cracks or scratches. Volumetric wear was calculated using a formula based on dimensional change due to the penetration of the femoral head in the acetabular cup. It was found to be of the same order of magnitude as the wear obtained in in vitro experimental tests.

Biomechanical Phenomena↗

PubMed1995

A computerized system for radiographical evaluation in total hip arthroplasty.

In the field of orthopaedic surgery radiographical image evaluation is frequently used to determine possible pathological processes. For total hip arthroplasty in particular, it is important to evaluate both preoperative femoral morphology and post-operative prosthesis performance in terms of bone adhesion to the implant and, consequently, loosening or stability of prosthesis components. References to a method called Roentgen stereophotogrammetric analysis (RSA) exist in the literature; however, the authors note that this method is expensive and requires the insertion of markers during the operation. Here we present an alternative computerized method for radiographical evaluation which we call radiographical evaluation system in total hip arthroplasty (RESTHA). The accuracy and the repeatability of the method have been evaluated using a medium-sized pelvis-femur system made of composite material. A mean error of +/- 2 mm has been associated to each experimental point. A post-operative inquiry case study is presented to indicate the applicability of the method.

Computers↗

PubMedDate not supplied

A computerized morphometric evaluation of x-ray films for preoperative planning of hip arthroplasty.

Methods for measuring metric size on radiograms constitute an instrument of proven utility. For example, when preoperatively evaluating hip arthroplasty the diameter of the medullary canal and the cervicodiaphyseal angle, must be measured in order to determine the center of rotation of the femoral head, and to establish the flare index of the diaphyseal canal. These results may be obtained by using a computer-controlled graphic table to place the coordinates for the areas of greater anatomical and physiological importance on the radiologic image. Thus, a calculation of distances, anatomical axes and angles is obtained immediately, accurately defining the morphometry of the joint. In this study, the anteroposterior preoperative radiographic views of 87 femurs in 84 patients were evaluated by this method. The values provided by the morphometric analysis were then related to sex, age and weight. The diaphyseal canal was classified by typology for the preoperative planning of hip arthroplasty.

Adult↗

PubMedDate not supplied

Wear of the epiphysis-acetabulum in total hip arthroplasty: a review of the literature.

Problems related to the use of total hip arthroplasty and the properties of the materials used to make prostheses have encouraged wear phenomena of the epiphysis-acetabulum combination of international importance and acknowledgement. Based on a review of the literature, the authors analyze the most recent years of study of wear phenomena and discuss the choice of materials to be used in total hip arthroplasty implant, with particular interest in any potential defects.

Acetabulum↗

PubMedDate not supplied

Metal-UHWMPE (Ultra High Molecular Weight Polyethylene) wear: experimental testing.

Testing conducted on a hip joint simulator verified the Charnley hypothesis that the diameter of the prosthetic head is proportional to wear. The study was conducted by pairing heads in Ortinox TM with acetabular cups in polyethylene at high molecular weight (UHMWPE). A comparison between the different sizes of the heads (26 and 30 mm in diameter) showed a different trend in the wear rate; in particular, the head with a smaller diameter behaves better tribologically than the head with a larger diameter.

Acetabulum↗