Biomedical subjects

A Toni

Publications and source records attributed to A Toni.

At least 19 recordsLinked to original sources

PubMed2001

Mixed oxides prosthetic ceramic ball heads. Part 3: effect of the ZrO2 fraction on the wear of ceramic on ceramic hip joint prostheses. A long-term in vitro wear study.

Using ceramic materials it is possible to obtain a number of beneficial mechanical properties such as considerable hardness, good chemical resistance, high tensile strength, and a good fracture toughness. The use of ceramic-on-ceramic as bearing surfaces for hip joint prostheses has been reported to produce a lower wear rate than other combinations (i.e. metal-on-polyethylene and ceramic-on-polyethylene) in total hip artroplasty. These advantages may increase the life expectancy of hip implants and improve the life of patients. Two new types of mixed-oxide ceramics (alumina and yttria-stabilised zirconia) femoral heads and acetabular cups containing different ratios of alumina and zirconia were compared with pure commercial alumina in terms of wear behaviour in a hip joint simulator. Hip joint wear simulator studies were carried out with a full-peak load of 2030 N and a frequency of 1 Hz in bovine calf serum. After 10 million cycles the measured weight loss of all specimens was very low. However, the experimental results did not show any significant difference between the new experimental mixed-oxide ceramics prototype and the commercial ceramic material couplings.

Aluminum Oxide↗

PubMed2000

Initial stability of a new hybrid fixation hip stem: experimental measurement of implant-bone micromotion under torsional load in comparison with cemented and cementless stems.

A new hybrid fixation stem, named cemented-locked uncemented (CLU), for total hip arthroplasty was developed to achieve good initial stability. Primary stability is guaranteed by the cement which is injected into two pockets in the lateral area. This leaves a large surface available for long-term biologic fixation (direct bone attachment on implant). This study evaluates in vitro the initial stability of the CLU prototype under torsional load, in comparison with cemented and cementless stems. The results show that the CLU stem is very stable in simulated stair climbing. Its micromotions are comparable to those of a cemented prosthesis, and significantly less (80-90% lower) than those for a cementless stem. These findings confirm the optimal initial stability expected from the CLU prototype. This new design, which employs hybrid fixation, should improve bone formation on the implant and reduce the risk of stem loosening.

Arthroplasty, Replacement, Hip↗

PubMed2000

An in vitro investigation of diamond-like carbon as a femoral head coating.

Wear of polyethylene acetabular components of hip implants is a significant clinical problem. In prosthetic hip surgery, polyethylene wear is identified as a factor that limits the life of the implant; it is known that the production of debris can cause adverse tissue reactions that may lead to extensive bone loss around the implant, and consequently loosening of the fixation. A new class of so-called Diamond-Like Carbon coatings, applied to titanium femoral heads was compared to ceramic and metallic heads in terms of wear behavior against UHMWPE using a hip joint simulator with a bovine calf serum lubricant. A thin film of Diamond-Like Carbon was deposited directly onto titanium (Ti6Al4V) head using chemical vapor deposition. The wear of polyethylene coupled with Diamond-Like Carbon coated femoral heads was comparable to that obtained with the polyethylene coupled with commercial alumina femoral heads.

Alloys↗

PubMed2000

Sister chromatid exchanges and ion release in patients wearing fracture fixation devices.

The quantification of sister chromatid exchange (SCE) during mitosis is a useful index for evaluating genotoxic effects in subjects occupationally or incidentally exposed to potentially toxic substances. The authors investigated the hypothesis that ions released by corrosion from prosthetic components of fracture fixation devices are associated with change in SCE incidence. In the present study, ten patients with implants were examined, and fifteen subjects with no implants were used as controls. SCE and high frequency cell (HFC) numbers were evaluated in circulating lymphocytes. In addition, nickel (Ni) and chromium (Cr) ion values in the serum were measured because, after iron, these metals are major components of stainless steel. A significant increase in SCE numbers was observed in patients compared to the control population (4.9 +/- 1.3 vs. 3.5 +/- 1.4). Ni concentration was 1.71 +/- 1.49 ng/mL in patients and 0.72 +/- 0.52 ng/mL in control subjects; Cr concentration was, respectively, 1.01 +/- 0.77 ng/mL and 0.19 +/- 0. 27 ng/mL. The increase of serum Cr and Ni was statistically significant. No correlation was found between the increased Cr concentrations and SCE number while Cr ion levels were found to be significantly correlated to HFC. An inverse correlation between Ni level and SCE numbers was observed. Our findings suggest that Cr release by stainless steel implants could have a genotoxic effect; thus it would be useful to carefully monitor implanted subjects with regard to serum ion dosage, SCE analysis, and HFC evaluation. In any case, it would be appropriate to remove the implant when fracture fixation is reached.

Adolescent↗

PubMed2000

Cytokines and osteolysis around total hip prostheses.

The aim of this work is to assess the correlation between the osteolysis around the prosthesis and the presence of cytokines favouring inflammation in the tissues at the interface between loosened prosthesis and bone. In this study, twenty-nine patients that underwent revision surgery were examined. Bioptic samples were collected at the interface between bone and implant both at the stem and socket level. Semiquantitative immunohistochemistry was performed to detect interleukin 1 alpha, interleukin 1 beta, interleukin 6 and tumour necrosis factor, cytokines that directly cause bone resorption and indirectly induce synthesis of other bone resorbing cytokines. Wear particles were identified and quantified by light microscopy. Radiographic evidence for osteolysis was scored by the Engh and Bobyn score. In tissues collected at the interface, the percentage of cells positive to IL1, IL6 and particularly to TNF increased in relation to the tissues collected at the interface with stable components. The cells occurring in the new capsule do not secrete cytokines in quantities that can be related to severity of wear. Cemented prostheses showed higher incidence of severe osteolysis, and higher levels of cytokines. It can be concluded that TNF, and to a lesser extent IL1 and IL6, are positively related to the severity of osteolysis around the prosthesis and therefore a pharmacological treatment can be hypothesized with anti-inflammatory or anti-cytokine drugs in order to limit or to avoid prosthesis loosening.

Adult↗

PubMed2000

Evaluation of radiolucency condition in total hip arthroplasty: a statistical comparison of the diagnostic capability of digitised image vs. conventional X-ray film.

This work analyses the diagnostic capability of radiographic images taken from patients with total hip arthroplasty and visualised on monitor. Images were obtained with digital acquisition of conventional X-ray films. The investigated pathology is the absence of direct contact between bone and prosthesis (radiolucency). Three senior orthopaedists defined the diagnostic "truth" on well-defined regions of interest on 22 conventional X-ray films of total hip arthroplasty, obtaining a total of 110 reference ratings. Films were digitised by use of an X-ray scanner. Four readers evaluated the X-ray images, applying conventional and monitor visualisation. To show any difference between ratings on film and ratings on monitor a sensitivity, specificity and accuracy study jointly with a receiver operating characteristics (ROC) study were performed for each reader and for all combined readings. The intra-observer reproducibility of the radiographic protocol was equal to 87% and the inter-observer one was in the range 85-92%. The sensitivity, specificity and accuracy study together with the ROC analysis did not show significant differences between the two evaluation modes. The evaluation of radiolucency from digitised X-ray films visualised on a monitor resulted statistically comparable with the conventional evaluation on X-ray films.

Diagnosis, Computer-Assisted↗

PubMed2000

Apoptosis in peri-implant tissue.

The authors examined 54 biopsies taken from the tissue surrounding loosened hip joint prostheses. In situ apoptotic cell identification was performed by the detection of single- and double-stranded DNA breaks that occurred in the early stages of apoptosis. Both types of breaks can be revealed by labeling the free 3'-OH termini with modified nucleotides (fluoresceine-dUTP) in an enzymatic reaction catalyzed by terminal deoxynucleotidyl transferase (TdT). Results were correlated with the presence of wear debris in the tissue and with the use of bone cement for prosthesis fixation. Apoptotic cells were present in a higher percentage in tissue sections where metal particles were present (24% apoptotic cells) if compared to areas where no wear (6%), or plastic wear (2.8%) or ceramic wear (1.5%) was observed. Apoptosis is neither related to bone cement, nor to the time it takes for the implant to fail. Cell death by apoptosis may be important in implants which release metal ions by corrosion or wear and may have been underestimated up to now, as it is a 'clean' way of cell death, leading to limited damage in the surrounding tissues.

Acetabulum↗

PubMed2000

In vitro cytokine production by mononuclear cells exposed to bone cement extracts.

The authors evaluated the ability of bone cement to modify the profile of pro-inflammatory cytokines secreted by the immune cells. Peripheral blood mononuclear cells (PBMC) collected from healthy individuals were cultured with cement extracts and tested to assess the release of IL-1beta, TNFalpha, GM-CSF and IL-6 in both unstimulated and PHA-stimulated PBMC. The cytokine release of unstimulated PBMC was very poor, and in particular the IL-1beta was undetectable: the addition of cement extract increased both TNFalpha and GM-CSF release and decreased IL-6, sometimes significantly. The most recurrent observation in PHA-stimulated PBMCs exposed to bone cement extract was the increase in both IL-1beta and IL-6 release, while both the mean concentration and the index of release of TNFalpha and GM-CSF were changeable. In conclusion our results showed that leachable components of some bone cements can induce in vitro the release of pro-inflammatory cytokines which are known to be involved in the bone resorption associated with aseptic loosening of hip prostheses. These findings allowed us to identify materials endowed with the highest inflammatory power.

Biocompatible Materials↗

PubMed2000

Leg length measurement: a new method to assure the correct leg length in total hip arthroplasty.

The precise measurement of leg length plays an important role in total hip arthroplasty. Leg length inequality occurs frequently after total hip arthroplasty and may cause patient discomfort. Current clinical methods used for measuring leg length are not accurate enough to meet the demands of precision required for hip replacement. The aim of this study was to examine the validity of determining leg length differences using an ultrasound system. The proposed system measures the distance between three points, in millimetres, so that the difference between preoperative and postoperative measurements gives an indication about the leg length. The mean ultrasound variation observed in in vitro measurements showed a relative error of 1.7% (range: 52-133 mm) that means a leg length inequality of about 0.4 mm (range: 52-133 mm). The method is non-invasive (ultrasound is not limited by radiation hazards), easy, quick to use, and can be used for standard clinical screening.

Anthropometry↗

PubMed2000

The effect of sandblasting treatment on endurance properties of titanium alloy hip prostheses.

Sandblasting is a procedure of increasing surface roughness. This treatment is common in the orthopedic field. An increased roughness may affect the endurance limit of the material. This study investigates the effect on the endurance limit of the Ti6Al4V due to two different sandblasting treatments: fine sandblasting and coarse sandblasting. Twenty hip stems, 10 finely sandblasted and 10 coarsely sandblasted, were tested under sinusoidal fluctuating bending. The staircase method was used to estimate the endurance limit of the material. The results show an important reduction in the endurance properties up to 40% for the coarsely sandblasted specimens. The failures of the sandblasted specimens were not due to material defects. Rather, the decreased endurance strength of the sandblasted stems was caused by surface defects, which act as crack initiators. By modulating the roughness with an appropriate sandblasting treatment, it is possible to limit the reduction in the endurance limit of the alloy.

Alloys↗

PubMed2000

Sister chromatid exchange in patients with joint prostheses.

The evaluation of sister chromatid exchanges (SCE) is used to establish the cytogenic damage in subjects exposed to toxic substances. The test is considered to be 1 of the most sensitive and accurate indicators of damage and responds to toxic chemicals at low doses. We evaluated the incidence of SCE in peripheral lymphocytes of patients with articular prostheses. Subjects with prostheses made of titanium-aluminium-vanadium alloys presented a significantly higher SCE number than the control population (6.3+/-2.3 vs 4.4+/-1.3; P = .0128), whereas subjects with prostheses made of chrome-cobalt alloy or mixed prostheses presented a higher SCE value than the controls but not significantly different. The presence of high-frequency cells was alarming only in 5 patients, 4 of whom had titanium alloy prostheses, whereas none belonged to the control group. The number of SCE was not affected by the presence of bone-cement used in prosthesis fixation or by the implant duration. The indication of possible cytogenic damage in patients with titanium alloy prostheses that emerged from this study should be considered carefully, even though the sample population was small.

Adult↗

PubMed2000

Design and validation of a machine for reproducible precision insertion of femoral hip prostheses for preclinical testing.

Preclinical testing of orthopaedic implants is becoming increasingly important to eliminate inferior designs before animal experiments or clinical trials are begun. Preclinical tests can include both laboratory bench tests and computational modeling. One problem with bench tests is that variability in prosthesis insertion can significantly influence the failure rate; this makes comparison of prostheses more difficult. To solve this problem an insertion method is required that is both accurate and reproducible. In this work, a general approach to the insertion of hip prostheses into femoral bones is proposed based on physically replicating an insertion path determined using computer animation. As a first step, the seated prosthesis position is determined from templates and femur radiographs. Three-dimensional images of the prosthesis and bone are then imported into computer animation software and an insertion path in the coronal plane is determined. The insertion path is used to determine the profile of a cam. By attaching the prosthesis to a carriage, which is pneumatically moved along this cam, the required insertion motion of the prosthesis in the coronal plane can be achieved. This paper describes the design and validation of the insertion machine. For the validation study, a nonsymmetric hip prosthesis design (Lubinus SPII, Waldemar Link, Germany) is used. It is shown that the insertion machine has sufficient accuracy and reproducibility for preclinical mechanical testing.

Animals↗

PubMed2000

The Italian experience of a Pap test and speculoscopy based screening programme.

OBJECTIVES: The main objective of the study was to evaluate if speculoscopy, a magnified chemiluminescent examination, combined with a Pap smear, could improve the detection of early cervical lesions compared with the Pap smear alone. SETTING: Pap tests and speculoscopies were performed in two family planning centres located in the surrounding areas of Modena. Colposcopic investigations and biopsies of the uterine cervix were performed in a second level centre (Gynaecological Prevention Centre of Modena Policlinico). Histological specimens were analysed at the Section of Pathological Anatomy of Modena Policlinico. SUBJECTS: The study population comprised 1000 women aged 25-64 years, invited to undergo a Pap smear every three years in accordance with the screening programme for cervical cancer started in Modena in 1997. METHODS: Midwives performed the Pap smear and speculoscopy in succession. Women with a positive Pap test and/or positive speculoscopy underwent colposcopy and, if colposcopic findings were positive, targeted punch biopsies were performed. RESULTS: A total of 1000 patients were subjected to cytology and speculoscopy examinations. Among these women, 10 had abnormal Pap smear findings whereas 144 had an abnormal speculoscopic pattern. Only three of 59 patients with a histological diagnosis of cervical intraepithelial neoplasia grade I (CIN I)/human papillomavirus and only three of seven patients with CIN II/CIN III had a positive Pap test. CONCLUSIONS: Speculoscopy combined with a Pap test can significantly increase the detection of cervical lesions when included in a screening programme.

Adult↗

PubMed2000

In vitro testing of ten bone cements after different time intervals from polymerization.

Biological response of cells to implanted bone cement is a fundamental but often neglected issue in successful cemented implants. In this study, ten acrylic bone cements for orthopedics were assayed using two different in vitro testing methods on L929 cells. The cements were mixed as prescribed, cured for either 1 h or 7 days and then extracted in minimum essential medium (MEM) according to the ISO standard for the preparation of samples. For the evaluation of cytotoxicity, the neutral red uptake assay (NRU) and the incorporation of propidium iodide (PI) were used to detect the viability/death of cells. The two methods were shown to be well correlated (p < 0.0001) in the case of both the 1-h and the 7-day extracts. Two cements, i.e. CERIM LT and CMW2, were found to be toxic after 1-h curing through both the spectrophotometric NRU assay and the cytofluorometric assay with PI. After 7-day curing, these two cements, as well as the Zimmer-low viscosity cement, were toxic according to the NRU assay. The toxic effect of all the cements disappeared after dilution of extracts 1:2 with MEM, except in the case of CERIM LT. In the search for the component inducing the toxic effect, the possible contribution of the residual monomer was discarded on the basis of literature data and the influence of various other factors was analyzed, including the contrast medium (barium sulphate or zirconium dioxide) and the concentrations of N,N-dimethyl-paratoluidine and of benzoyl peroxide (< 1% or > or = 1%). Unlike zirconium dioxide, barium sulphate was found to damage the cells at the 1-h endpoint. Benzoyl peroxide at concentration > or = 1% was found to affect cells at the same endpoint, whereas dimethylparatoluidine had no effect regardless of the proportion.

Animals↗

PubMed2000

Modulation of pro- and anti-apoptotic genes in lymphocytes exposed to bone cements.

The ability of bone cements to modify the apoptotic program in activated immune cells and the mechanisms by which they act were evaluated. Mononuclear cells were collected from healthy individuals, cultured for 4 and 24 h with phytohemoagglutinina-P and cement extracts and then tested to assess: (a) cell viability; (b) early apoptotic events, by Annexin V/propidium iodide staining; and (c) the expression of pro- (p53, c-myc, ICE) and anti-apoptotic (bcl-2) genes. After 4 h three cements were able to increase significantly the percentage of apoptotic cells, while after 24 h no differences were found. The proportion of dead cells was not significantly changed at either culture time. The simultaneous expression of both pro-apoptotic (ICE, c-myc, p53) and antiapoptotic genes (bcl-2) was investigated only with regard to the materials which induced significant changes in apoptosis: two cements induced the p53 expression, while the third down-regulated bcl-2. As apoptosis regulates the balance of immune response, the authors recommend that the interaction between materials and immune cells should be assessed, so that the use of pro-apoptotic materials may be avoided in patients with immune defects.

Annexin A5↗

PubMed2000

Alumina femoral head fracture: an in vitro study.

A fracture of a ceramic femoral head is reported in this study. Fractures of ceramic femoral heads are uncommon and reports on this complication are rare. After 3 million cycles, on a twelve station hip simulator that tested alumina femoral head against polyethylene acetabular cup, fracture of the ceramic ball was observed. The retrieved specimen consisted of three large ceramic fragments from the same ceramic femoral head, a polyethylene acetabular cup and a stainless steel jig. Careful and detailed examination of the removed components was made. The fracture of the ceramic ball resulted in damage to the metal taper of the jig component which was fixed into the simulator.

Acetabulum↗

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↗