Biomedical subjects

L Yahia

Publications and source records attributed to L Yahia.

At least 19 recordsLinked to original sources

PubMed2000

Plasma-based sterilization: effect on surface and bulk properties and hydrolytic stability of reprocessed polyurethane electrophysiology catheters.

Plasma-based sterilization is a promising alternative to ethylene oxide (EO) for reprocessing of electrophysiology catheters. To assess its safety in terms of material damage, modifications of surface and bulk properties as well as hydrolytic stability of sterilized catheters were evaluated. Polyurethane (PU) single-use electrophysiology catheters were subjected to one, five, and ten sterilization cycles by Sterrad-100S and Plazlyte, as well as by pure EO for comparison. Surface analysis techniques (ATR-FTIR, XPS, DCA) showed oxidation limited to the near-surface layer induced by both plasma-based sterilizers, whereas EO induced slight but deeper alkylation. Using bulk analysis techniques (RP-HPLC, SEC), oligomer alteration was observed after all three sterilization techniques, without modification of molecular weights. Hydrolytic stability of catheters was slightly changed by plasma-based sterilization, with a small increase in released oligomers. Finally, although Plazlyte and Sterrad are both plasma-based techniques, they induced different impacts on catheters, such as the degradation of an additive with Sterrad, and a clear difference in coloration with Plazlyte.

Catheterization↗

PubMed2000

Three-dimensional knee analyzer validation by simple fluoroscopic study.

Introduction: The complexity of the knee articulation makes its clinical evaluation extremely difficult. Insufficiency of existing instruments for knee evaluation prevents physicians from providing a diagnosis of injury and/or an evaluation of different treatments. To this end, our research group has developed a functional knee analyzer, which allows a three-dimensional evaluation of the knee in motion. The goal of this study is to scientifically validate the functional knee analyzer before using it in clinical setting. Materials and methods: The three-dimensional knee analyzer includes an orthoplastic exoskeleton attachment system, a kinematic tracking device, a screen for graphical display and a C(++) program with a user interface for calculating kinematic indices. A fluoroscopic study was performed on five healthy subjects with a mean age of 28. The experiment was set-up to determine the reduction of skin movement with respect to the underlying bone by using a knee exoskeleton attachment system. The root mean square (RMS) errors of markers movement about the abduction-X (RMSRx) and tibial rotation-Z (RMSRz) axes and displacement in the XZ plane (RMSpxpz) were calculated, once by placing markers directly on the skin and once on the exoskeleton attachment system. Results: Our results demonstrated that RMSpxpz, RMSRx and RMSRz were reduced by a factor of 6 (min 1.8, max 26), 4.3 (min 0.75, max 21) and 6.2 (min 2, max 26.4) on average, respectively, for four subjects out of five when the exoskeleton attachment was used.

Journal Article↗

PubMed2000

Effect of surface treatment and sterilization processes on the corrosion behavior of NiTi shape memory alloy.

Nickel-titanium (NiTi) alloy derives its biocompatibility and good corrosion resistance from a homogeneous oxide layer mainly composed of TiO(2), with a very low concentration of nickel. In this article, we described the corrosion behavior of NiTi alloys after mechanical polishing, electropolishing, and sterilization processes using cyclic polarization and atomic absorption. As a preparative surface treatment, electropolishing decreased the amount of nickel on the surface and remarkably improved the corrosion behavior of the alloy by increasing the mean breakdown potential value and the reproducibility of the results (0.99 +/- 0.05 V/SCE vs. 0.53 +/- 0. 42). Ethylene oxide and Sterrad(R) sterilization techniques did not modify the corrosion resistance of electropolished NiTi, whereas a steam autoclave and, to a lesser extent, peracetic acid sterilization produced scattered breakdown potential. In comparing the corrosion resistance of common biomaterials, NiTi ranked between 316L stainless steel and Ti6A14V even after sterilization. Electropolished NiTi and 316L stainless-steel alloys released similar amounts of nickel after a few days of immersion in Hank's solution. Measurements by atomic absorption have shown that the amount of released nickel from passive dissolution was below the expected toxic level in the human body. Auger electron spectroscopy analyses indicated surface contamination by Ca and P on NiTi during immersion, but no significant modification in oxide thickness was observed.

Alloys↗

PubMed2000

Effects of sterilization processes on NiTi alloy: surface characterization.

Sterilization is required for using any device in contact with the human body. Numerous authors have studied device properties after sterilization and reported on bulk and surface modifications of many materials after processing. These surface modifications may in turn influence device biocompatibility. Still, data are missing on the effect of sterilization procedures on new biomaterials such as nickel-titanium (NiTi). Herein we report on the effect of dry heat, steam autoclaving, ethylene oxide, peracetic acid, and plasma-based sterilization techniques on the surface properties of NiTi. After processing electropolished NiTi disks with these techniques, surface analyses were performed by Auger electron spectroscopy (AES), atomic force microscopy (AFM), and contact angle measurements. AES analyses revealed a higher Ni concentration (6-7 vs. 1%) and a slightly thicker oxide layer on the surface for heat and ethylene oxide processed materials. Studies of surface topography by AFM showed up to a threefold increase of the surface roughness when disks were dry heat sterilized. An increase of the surface energy of up to 100% was calculated for plasma treated surfaces. Our results point out that some surface modifications are induced by sterilization procedures. Further work is required to assess the effect of these modifications on biocompatibility, and to determine the most appropriate methods to sterilize NiTi.

Algorithms↗

PubMed2000

In vitro and in vivo biocompatibility of chitosan-xanthan polyionic complex.

A novel hydrogel, CHITOXAN(TM) (CH-X), has potential as a vehicle for controlled drug delivery. The hydrogel is obtained by complexation of two polysaccharides, chitosan and xanthan. In the present work we investigated the biocompatibility of the complex using in vitro and in vivo models. The cytotoxic effects of CH-X microspheres as well as their degradation products at different concentrations were assessed on fibroblasts (fibroblast cell line L-929) using 3-(4,5-dimethylthiazole-2yl)-2,5-triphenyl tetrazolium) (MTT). The test is based on mitochondrial dehydrogenase cell activity as an indicator of cell viability. Interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) cytokines as well as nitric oxide (NO) production by macrophages (macrophage cell line J-774) were examined as indicators of cell activation. In vivo biocompatibility assessment was performed for 1 to 12 weeks. This study was performed using tablets obtained after compression of CH-X particles implanted at the subcutaneous level in male Wistar rats. CH-X biocompatibility and degradation were investigated using histological studies. Light and transmission electron microscopy (TEM) analyses were used to determine the foreign-body reaction and phagocytosis of the implants by macrophages. Fibroblast exposition to CH-X particles and degradation products did not show cytotoxic effects as measured by MTT test. TNF-alpha production was dependent on CH-X particles concentration, whereas IL-1beta production was found to be dose independent. CH-X extract products stimulated TNF-alpha secretion when used at the highest concentration (10 mg/mL), notably after 28 days' degradation time. No effect was observed on IL-1beta production when CH-X extracts were used in comparison to the control. The effects of CH-X particles on NO secretion were similar as on TNF-alpha. Histological studies showed that CH-X tablets broke down into particles which progressively degraded into smaller fragments. A significant fraction of the fragments was ingested by the macrophages after 12 weeks of implantation. Light microscopy studies showed a weak foreign-body reaction as a function of time and the fibrous layer thickness decreased with time of implantation.

Animals↗

PubMed2000

Effect of gas composition on spore mortality and etching during low-pressure plasma sterilization.

The aim of this work was to investigate possible mechanisms of sterilization by low-temperature gas plasma: spore destruction by plasma is compared with etching of synthetic polymers. Bacillus subtilis spores were inoculated at the bottom of glass vials and subjected to different plasma gas compositions (O(2), O(2)/Ar, O(2)/H(2), CO(2), and O(2)/CF(4)), all known to etch polymers. O(2)/CF(4) plasma exhibited much higher efficacy than all other gases or gas mixtures tested, with a more than 5 log decrease in 7.5 min, compared with a 2 log decrease with pure oxygen. Examination by scanning electron microscopy showed that spores were significantly etched after 30 min of plasma exposure, but not completely. We speculate about their etch resistance compared with that of synthetic polymers on the basis of their morphology and complex coating structure. In contrast to so-called in-house plasma, sterilization by Sterrad(R) tended to increase the observed spores' size; chemical modification (oxidation), rather than etching, is believed to be the sterilization mechanism of Sterrad(R).

Bacillus subtilis↗

PubMed2000

Study of biodegradation behavior of chitosan-xanthan microspheres in simulated physiological media.

Microspheres of a polyelectrolyte complex hydrogel were prepared from chitosan and xanthan after interaction between the two polyionic polymers. Their biodegradation was studied vs. chitosan. Simulated gastric fluid (SGF, pH 1.2) and intestinal fluid (SIF, pH 7.5) both as biodegradation media and phosphate buffered saline (PBS, pH 7.4) as a negative control were used. The degradation studies were performed at 37 degrees C at 240 rpm permanent stirring to mimic the physiologic conditions. High performance liquid chromatography (HPLC) was carried out to quantify the chitosan degradation products using glucosamine (GA) and N-acetyl-D-glucosamine (N-Ac-GA) as references. The peaks area integration method was used to determine the amount of each degradation product as a function of incubation time in the media. The effect of the media on the morphological structure of microspheres was assessed by scanning electron microscopy. From HPLC studies, it appeared that in SGF and SIF the major degradation products were glucosamine (GA) and N-acetyl-D-glucosamine (NAc-GA). In the first 15 days, oligochitosan fractions were released from the complex, whereas N-acetyl-D-glucosamine was detected in the media after this period. The degradation kinetics were assessed by the measurement of the cumulative degradation products, which showed faster degradation of chitosan than the complex in SGF and SIF. SEM micrographs showed an enhancement of microsphere porosity as a function of incubation time in the simulated physiological media. Our results suggest a better control of the degradation kinetics when chitosan is complexed to xanthan.

Acetylglucosamine↗

PubMed1999

Induction of macrophage apoptosis by ceramic and polyethylene particles in vitro.

The purpose of this study was to investigate in vitro the presence of apoptotic cell death after macrophage stimulation with different ceramic (Al2O3 and ZrO2) and high density polyethylene (HDP) particles. We also analyzed the effects of particle size, concentration, and composition. The J774 mouse macrophage cell line was exposed to commercial particles of different sizes (up to 4.5 microm) and concentrations (up to 500 particles per macrophage). Fluorescence microscopy and DNA laddering were used to investigate the presence of apoptosis in cell cultures after 24 h of incubation. Fluorescence microscopy of propidium iodide stained cells showed two characteristic morphological features that occur in apoptotic cells, namely nuclear condensation and heterogeneity of stain uptake. The effect of ceramic particles on apoptotic nuclear morphology was size- and concentration-dependent and reached a plateau above 150 particles per macrophage at 1.3 microm. With regards to composition, we did not find any difference in cell morphology between Al2O3 and ZrO2. Ceramic and HDP particles induced DNA fragmentation into oligonucleosomes as evidenced by DNA laddering, another characteristic of apoptosis. The induction of DNA laddering was size- and concentration-dependent whereas particle composition (Al2O3 vs. ZrO2 and Al2O3 vs. HDP) had no effect. In conclusion, our results demonstrated that ceramic and HDP particles induce macrophage apoptotic cell death in vitro and open doors for possible modulation of debris-induced periprosthetic osteolysis.

Aluminum Oxide↗

PubMed1999

A mechanical comparison of the immediate stability of three fixation devices used in wrist arthrodesis: a cadaveric study.

This study was designed to determine which of 3 fixation devices used in wrist arthrodesis provides the greatest immediate stability along 2 axes of movement. Twenty cadaver wrists were mechanically tested. Group 1 consisted of 7 wrists stabilized using a 2.3-mm Steinmann pin. Six wrists from the second group were immobilized with a 9-hole, 3.5-mm AO dynamic compression plate. The third group consisted of 7 wrists stabilized with an 8-hole, short-bend, precontoured low-contact dynamic compression plate. Stiffness and fracture force were determined in both forced flexion and forced pronation. The results showed that the Steinmann pin was the least stable of the 3 constructs in both axes of movement. No differences were observed between the 2 compression plates for either of the 2 axes of movement.

Arthrodesis↗

PubMed1999

Cytotoxicity and macrophage cytokine release induced by ceramic and polyethylene particles in vitro.

Although the response of macrophages to polyethylene debris has been widely studied, it has never been compared with the cellular response to ceramic debris. Our aim was to investigate the cytotoxicity of ceramic particles (Al2O3 and ZrO2) and to analyse their ability to stimulate the release of inflammatory mediators compared with that of high-density polyethylene particles (HDP). We analysed the effects of particle size, concentration and composition using an in vitro model. The J774 mouse macrophage cell line was exposed to commercial particles in the phagocytosable range (up to 4.5 microns). Al2O3 was compared with ZrO2 at 0.6 micron and with HDP at 4.5 microns. Cytotoxicity tests were performed using flow cytometry and macrophage cytokine release was measured by ELISA. Cell mortality increased with the size and concentration of Al2O3 particles. When comparing Al2O3 and ZrO2 at 0.6 micron, we did not detect any significant difference at the concentrations analysed (up to 2500 particles per macrophage), and mortality remained very low (less than 10%). Release of TNF-alpha also increased with the size and concentration of Al2O3 particles, reaching 195% of control (165 pg/ml v 84 pg/ml) at 2.4 microns and 350 particles per cell (p < 0.05). Release of TNF-alpha was higher with HDP than with Al2O3 particles at 4.5 microns. However, we did not detect any significant difference in the release of TNF-alpha between Al2O3 and ZrO2 at 0.6 micron (p > 0.05). We saw no evidence of release of interleukin-1 alpha or interleukin-1 beta after exposure to ceramic or HDP particles.

Aluminum Oxide↗

PubMed1999

[Mechanical evaluation of a ligament fixation system for ACL reconstruction at the tibia in a canine cadaver model].

OBJECT: Excellent fixation of an artificial ligament in bone is mandatory for initial stability. ACL reconstruction with the LARS artificial ligament may fail if anchorage to bone is inadequate. The weak metaphyseal bone of the proximal tibia is prone to inadequate fixation. This study evaluates the initial mechanical stability of two techniques with an interference screw on the tibial side of an ACL reconstruction with the LARS ligament. METHODS: Six left tibias were obtained from 1 to 3 year old mongrel dog weighing 20 to 26 kg. ACL straight line reconstruction according to the technique described by J.P. Laboureau was performed with a 4.5 mm drill. Two tunnels were created in the tibia, one oblique and one transverse, the latter 2 cm below the former. Reconstruction was done with a 30-fiber LARS ligament and a 5.2 mm x 15 mm conical titanium cannulated interference screw. Group I had an interference screw in the oblique tunnel and group II had an interference screw in the transverse tunnel. Pull-out tests were performed parallel to the oblique tunnel on an Instron 8521 machine at a speed of 5 mm per minute until failure. The oblique tunnel was tested first then the transverse tunnel. RESULTS: Group I (n = 6): sliding value = 238 +/- 115 N. Group II (n = 6): sliding value = 998 +/- 148 N. This is statistically significant (p < 0.001, student t-test). CONCLUSION: One interference screw in a transverse tibial tunnel for ACL reconstruction with the LARS ligament is 4 times more resistant on loading and impact than an oblique screw.

Animals↗

PubMed1998

Flow cytometric analysis of macrophage response to ceramic and polyethylene particles: effects of size, concentration, and composition.

Using the J774 macrophage cell line, we designed an in vitro model to analyze by flow cytometry the effects of size, concentration, and composition of ceramic (Al2O3 and ZrO2) and high density polyethylene (HDP) particles on phagocytosis and cell mortality. Inflammatory mediator (TNF-alpha) also was measured by ELISA. Kinetic studies revealed that phagocytosis of the particles begins very early after cell exposure, increasing with time and particle concentration and reaching a plateau after 15 h. This implies that the optimum period to evaluate cellular response to particulate debris is between 15 and 24 h of incubation. Results also showed that phagocytosis increases with concentration for particles up to 2 microns. For larger particles (up to 4.5 microns), phagocytosis seems to reach a plateau independent of size and concentration, which suggests a saturation of phagocytosis that is most likely dependent on overall particle volume ingested. We did not detect any significant difference in phagocytosis between Al2O3 and ZrO2 at 0.6 microns. Al2O3 seems to be more easily phagocytosed than HDP at the same size (4.5 microns) and concentrations. Cytotoxicity studies revealed that macrophage mortality increases with particle size and concentration for sizes greater than 2 microns. Smaller particles (0.6 microns) cause cell mortality only at higher concentrations (from 1,250 particles per cell), but the mortality is still very low (10%). No significant difference in cell mortality and TNF-alpha release was found between Al2O3 and ZrO2. Effects of Al2O3 and HDP at 4.5 microns were compared by measuring TNF-alpha release. Results showed that TNF-alpha release increases with particle concentrations and is higher with HDP than with Al2O3.

Aluminum Oxide↗

PubMed1998

[Biomechanical evaluation and clinical correlation of 3 methods of internal fixation of metacarpophalangeal arthrodesis of the thumb].

Three methods of internal fixation for MCP arthrodesis of fifteen cadaveric thumbs were used to analyze the biomechanical stability by applying a palmar force, lateral force, and torsion moment. The techniques used included two K-wires 0.045 in parallel (BK), 2 cerclage metallic wires #25 perpendicular to each other (CP), and a 6-holes plate and screws construct from Synthes (PV). The initial rigidity was measured using a Bionix MTS-858. The results after statistical analysis showed: 1) CP was just as rigid as PV for the palmar and lateral tests; 2) CP was, overall, superior to BK in palmar and lateral tests; 3) no difference existed in torsion between the three types of fixation. A comparison was done between the rigidity of the fixation techniques used and the rates of bony nonunion found in the literature. The mean rates of nonunion were reported to be 0-4.0% for the following techniques: CP, tension band wiring (TB), plate and screws, external fixation, compression screw. The rates of nonunion were higher, 7.5-12.5%, for BK, cerclages not perpendicular (CM), bone pegs. According to the results of this biomechanical study and the review of the literature, fixation with BK is the least rigid, and fixation with CP is just as rigid as with PV. The success clinically of CP is yet to be demonstrated. Other studies on the properties of CP for fatigue would be necessary to give a better analysis.

Analysis of Variance↗

PubMed1997

Ceramic-ceramic and metal-polyethylene total hip replacements: comparison of pseudomembranes after loosening.

We made a semiquantitative study of the comparative histology of pseudomembranes from 12 loose cemented ceramic-ceramic and 18 metal-polyethylene total hip replacements. We found no significant difference in cellular reaction between the two groups, but there was a major difference in the origin of the particulate debris. In the metal-polyethylene group, polyethylene of articular origin was predominant, while in the ceramic-ceramic group the cellular reaction appeared to be a response to zirconia ceramic particles used to opacify cement used for fixation. Isolation and characterisation of the debris showed that the zirconia particles formed the greatest proportion (76%) in ceramic-ceramic hips, while alumina debris of articular origin formed only 12%. Our study has indicated that aseptic loosening of ceramic cups is not due to a response to debris generated at the articular interface, but to mechanical factors which lead to fragmentation of the cement.

Bone Cements↗

PubMed1996

Proliferative and matrix synthesis response of canine anterior cruciate ligament fibroblasts submitted to combined growth factors.

We investigated the effects of growth factors on the proliferation and matrix synthesis of anterior cruciate ligament fibroblasts. Fibroblasts from the anterior cruciate ligaments of dogs were transferred at the second passage in a defined medium. Epidermal growth factor, platelet-derived growth factor-AB, transforming growth factor-beta 1, insulin-like growth factor-1, and insulin, combined two by two following a 5 x 5 logarithmic concentration matrix, were added. Tridimensional curves showing cell proliferation at 24 hours against the concentration of two effectors were obtained for each combination. Collagen and proteoglycan productions were quantified using [14C]glycine and Na2[35S]O4. Ratios of type I:III collagen and hydrodynamic size distributions of proteoglycans were assayed, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography. Epidermal growth factor had an effect nearly equivalent to that of platelet-derived growth factor-AB on cell proliferation. Both had a greater effect than insulin-like effect of transforming growth factor-beta 1. Neither platelet-derived growth factor-AB nor insulin has a significant effect by itself on collagen production. Epidermal growth factor slightly decreases collagen production as well as the type I:III collagen ratio; both transforming growth factor-beta 1 and insulin-like growth factor-1 increase the same parameters. Epidermal growth factor inhibits the stimulation induced by transforming growth factor-beta 1. Similarly, insulin decreases the response to insulin-like growth factor-1. Proteoglycan production was significantly increased by all growth factors in this study, with transforming growth factor-beta 1 having the strongest effect. Small hydrodynamic size of proteoglycan was correlated to a high level of proteoglycan. biosynthesis. The results may be readily applied to tissue engineering or provide a basis for in vivo investigations.

Animals↗

PubMed1996

Moment arms and lengths of human upper limb muscles as functions of joint angles.

Modeling of musculoskeletal structures requires accurate data on anatomical parameters such as muscle lengths (MLs), moment arms (MAs) and those describing the upper limb position. Using a geometrical model of planar arm movements with three degrees of freedom, we present, in an analytical form, the available information on the relationship between MAs and MLs and joint angles for thirteen human upper limb muscles. The degrees of freedom included are shoulder flexion/extension, elbow flexion/extension, and either wrist flexion/extension (the forearm in supination) or radial/ulnar deviation (the forearm in mid-pronation). Previously published MA/angle curves were approximated by polynomials. ML/angle curves were obtained by combining the constant values of MLs (defined by the distance between the origin and insertion points for a specific upper limb position) with a variable part obtained by multiplying the MA (joint radius) and the joint angle. The MAs of the prime wrist movers in radial/ulnar deviation were linear functions of the joint angle (R2 > or = 0.9954), while quadratic polynomials accurately described their MAs during wrist flexion/extensions. The relationship between MAs and the elbow angle was described by 2nd, 3rd or 5th-order polynomials (R2 > or = 0.9904), with a lesser quality of fit for the anconeus (R2 = 0.9349). In the full range of angular displacements, the length of wrist, elbow and shoulder muscles can change by 8.5, 55 and 200%, respectively.

Anthropometry↗

PubMed1996

Corrosion resistance improvement of NiTi osteosynthesis staples by plasma polymerized tetrafluoroethylene coating.

NiTi shape Memory Alloys (SMA) are potential biomaterial candidates for medical devices such as osteosynthesis staples. However, Ni dissolution induced by uniform or localized corrosion could lead to toxicity. In this work, plasma polymerized tetrafluoroethylene (PPFTE) coating is used to improve the corrosion resistance of NiTi plates and corresponding NiTi stables. The scratch test indicates a good surface adhesion of the film but that it lacks cohesiveness. Potentiodynamic tests in physiological Hank's solution show that PPTFE coating improved the pitting corrosion resistance. The passivation range is increased from 35% to 96% compared to the untreated sample and the pit diameter is decreased from 100 microns to 10 microns. The uniformity of the deposited film is a very important parameter. When the film is damaged, the corrosion seems to increase in comparison to the untreated samples. Otherwise, if the staple is carefully manipulated, the coating follows the large deformations induced by the memory effect of the alloy without cracking, and then, protects efficiently the staple from pitting.

Alloys↗

PubMed1995

[Responses of ligamentous fibroblasts to mechanical stimulation].

Mechanical stimulation, as provided by physiotherapy or controlled motion is essentially the only factor able to improve anterior cruciate ligament (ACL) healing. We investigate the cellular effects of such stimulus. Two types of stimulations are applied on canine ACL fibroblasts: repetitive stretch of an elastomeric adhesion substrate and a laminar flow of culture media over the culture surface. Cell orientation, proliferation rate, synthesis and type of collagen as well as proteoglycans (PG) synthesis and hydrodynamic characteristics have been studied. According to our results, the fibroblasts tend to align perpendicularly to the deformation axis of their substrate, and along a laminar flow. The shear stress induced by the laminar flow does not modify significantly proliferation rate nor extracellular matrix synthesis. Substrate stretching however, increases proliferation rate, collagen synthesis, mostly type III, and PG synthesis, principally of small sizes. The characteristics of fibroblasts submitted to repeated deformation match those of fibroblasts from ligament scar tissues. Their orientation perpendicular to substratum deformation differs from the one usually encountered in the undamaged tissue: aligned on the ligament axis.

Adult↗