Biomedical subjects

A Toni

Publications and source records attributed to A Toni.

At least 55 records · Page 3Linked to original sources

PubMed2001

Fluid absorption study in ultra-high molecular weight polyethylene (UHMWPE) sterilized and unsterilized acetabular cups.

The weight gain due to fluid absorption was measured in gamma-sterilized, ethylene oxide (ETO) gas-sterilized, and unsterilized ultra-high molecular weight (UHMW) polyethylene acetabular cups. After about 2 months the total average fluid absorption gain of the polyethylene cups was: 1.76 +/- 0.45 mg (average +/- standard deviation) for the unsterilized polyethylene cups, 2.81 +/- 0.95 mg for the gamma-sterilized polyethylene cups and 1.51 +/- 0.34 for the ETO gas-sterilized polyethylene cups. There was little difference in fluid absorption between the sterilized and unsterilized specimens. In particular, the gamma-sterilized acetabular cups absorbed more than the ETO gas-sterilized and the unsterilized cups. However, the weight gain was higher in serum compared with that in water.

Absorption↗

PubMed2001

Temperature and ageing condition effects on the characterization of acrylic bone cement.

This study investigates the effect of the environmental temperature and ageing condition on the characterization of acrylic bone cement. The tests were performed according to ISO 5833. The testing parameters were allowed to vary within the limits defined by the standard, in order to assess their effect on the results of the test. In certain cases the tests were also performed under conditions which the standard does not provide for but which are likely to occur clinically. This investigation showed that the cement behaviour may also change in the temperature range specified in the standard. Therefore, it is deemed appropriate to correlate the curing parameters of the bone cement to the environmental temperature, performing the test at different temperatures. In this way the effect of temperature on the duration of the phases in the cement curing could be assessed. The resultant graphical representation of the effect of temperature on the duration of the phases in cement curing has direct clinical relevance. Furthermore, this study showed that the ageing conditions of the mechanically tested specimens affected the results. Hence, it is deemed advisable to modify the ageing conditions of the specimens, fixing them closer to the in vivo conditions.

Arthroplasty, Replacement↗

PubMed2001

In vitro testing of the primary stability of the VerSys enhanced taper stem: a comparative study in intact and intraoperatively cracked femora.

The Zimmer VerSys enhanced taper uncemented stem was tested in vitro for primary stability. Six stems were implanted in six composite femora. Three femora were unintentionally damaged by cracking of the bone during stem insertion and press-fit. A previously validated protocol was used to load the specimens cyclically and to record locally the rotational and axial bone/implant relative motions in terms of elastic motion and permanent migration. For the undamaged femora, the VerSys stem showed excellent primary stability, in terms of both elastic motions (less than 9 microns) and permanent migrations (less than 6 microns), and in both axial and rotational directions, comparing favorably with the literature. Intraoperatively-induced proximal cracks did influence the primary stability of the stem in terms of permanent migration. As cracks may easily be produced in the diaphyseal canal during insertion of cementless stems, which rely for primary stability on conical fitting into the canal, great care must be taken in preparation of the canal and insertion of the stem.

Arthroplasty, Replacement, Hip↗

PubMed2001

A CAD-CAM methodology to produce bone-remodelled composite femurs for preclinical investigations.

Femoral bone remodelling, following total hip arthroplasty, is a clinically observed phenomenon attributed to the changed stress environment of the postoperative implanted hip. While this process cannot be avoided, there is concern as to its consequences on the long-term survival of hip joint replacements. Previous methods of studying remodelling, such as clinical or animal-based studies, or finite element analyses, have their limitations. The aim of this study is to develop experimental specimens incorporating bone resorption features typical of clinically successful implants. This work describes the use of computer aided design/manufacturing methods (CAD-CAM) to produce these specimens, based on modifying commercially available composite femurs. The procedures are investigated and verified for two different designs of cemented prostheses (Lubinus SPII and Muller Curved). Quantitative clinical data is used to define the remodelled geometry of a CAD model of the femur for each stem design. Composite femur specimens are machined using a three-axis milling machine, where each specimen can be accurately positioned using a custom-designed jig and a digitizer system. The accuracy of the process is assessed by analysing the deviation of the digitized premachined and postmachined surfaces of each specimen in relation to the CAD model. The results demonstrate that the procedure can be used for developing in vitro specimens with bone resorption features. These specimens are proposed as a useful tool for performing preclinical trials, such as load transfer or longevity/stability testing, with the advantage of modelling a long-term clinical situation, rather than solely analysing implanted femurs in an immediate postoperative state.

Arthroplasty, Replacement, Hip↗

PubMed2001

Design revision of a partially cemented hip stem.

In a previous preclinical study the prototype version of a partially cemented hip stem, cement-locked uncemented (CLU) prosthesis, showed optimal primary stability and moderate stress shielding. However, numerical analysis suggested that the prototype design would induce relatively high stresses in the cement and a significant relative motion between cement and metal. The present study aimed to verify if these problems could be eliminated once the CLU design is improved. The revised design was analysed using a complete finite element model of an implanted human femur. To further strengthen the predictions of the finite element analysis, the cement damage induced by a severe load history was assessed experimentally in synthetic femurs implanted with the improved CLU stem or with a clinically successful fully cemented stem. The modifications made to the CLU stem design did not reduce its good primary stability but decreased the metal-cement relative micromotion. The same load induced stresses in the cement mantle of the improved CLU stem that were significantly lower than those predicted for the prototype design. Although the presence of modelling artefacts produced a highly localized stress peak of 13 MPa. 99 per cent of the cement volume was subjected to a principal tensile stress lower then 4 MPa. These levels of stress compare favourably with the tensile fatigue limit of the acrylic cement used in this study (9.7 MPa). The experimental results further supported these findings. The cemented stem showed a number of cracks per volume unit approximately ten times higher than the partially cemented stem under investigation.

Bone Cements↗

PubMed2001

Severe wear from retrieved alumina-on-alumina coupled implant: a case report.

This study details the in vivo wear behavior of an alumina acetabular cup and a femoral head on a retrieved non-cemented hip prosthesis. A commercial alumina ceramic-on-ceramic prosthesis was retrieved from a patient previously treated for bilateral hip arthrosis in "coxa profunda". Massive wear was found on the retrieved alumina ceramic head and acetabular cup. The total measured penetration depth was 1.9 mm while the total calculated weight loss for the acetabular cup was 6.06 g. The study underlines the head-cup instability caused by cup loosening as major cause of severe ceramic wear.

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↗