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Biomedical subjects

A Meunier

Publications and source records attributed to A Meunier.

At least 55 records · Page 3Linked to original sources
PubMed1998

Cytokine release from marrow mononuclear cells is negatively correlated to cortical elasticity in non-osteoporotic postmenopausal women.

Activation of bone remodeling is likely to be under the control of mechanical factors acting, in part, through soluble local factors. We therefore investigated a relationship between cytokine production by marrow cells and bone elasticity. We studied 36 non-osteoporotic postmenopausal women undergoing hip arthroplasty for hip arthrosis (mean age: 68 +/- 8 years; lumbar BMD Z-score: +0.54 +/- 0.33 SD). Adherent marrow mononuclear cells were cultured for 48 hours with autologous plasma, and supernatants were harvested for PGE2, IL-1, TNF-alpha, and IL-6 measurements. Femoral neck cortical bones were removed during surgery for cortical histomorphometric evaluation and determination of elasticity indices (C33) using ultrasonic transmission method. In this nonosteoporotic population, femoral neck longitudinal elasticity indices were inversely correlated to both cortical thickness (r = -0.58, P < 0.01) and cortical porosity (r = -0.33, P < 0.01). The longitudinal elasticity indices were also negatively correlated to basal IL-1 and TNF-alpha release by adherent mononuclear marrow cells (r = -0.59, P < 0.01; r = -0.60, P < 0.01, respectively). However, no relationship was found between the three cytokines tested and either cortical thickness or porosity. These data show a link between cortical biomechanical properties and local factors involved in bone remodeling. We suggest that increased bone elasticity decreases transmission of strain, which in turn decreases cytokine release from marrow cells. However, whether cytokines influence bone elasticity or vice versa remains to be demonstrated.

Aged↗
PubMed1998

Anatomic and mechanical properties of the lateral disc attachment of the temporomandibular joint.

PURPOSE: This study measured the strength to failure of the human temporomandibular joint (TMJ) lateral disc attachment (LDA) using a tension-compression machine. These data were correlated with the LDA location and its morphologic aspects, the age and sex of the subjects, and the amount of the lateral pterygoid muscle (LPM) inserted in the disc. METHODS: Forty-two TMJs without any obvious internal damage were carefully dissected to preserve the LDA. The width of insertion of the lateral pterygoid muscle fibers in the anterior band, as well as the width of the disc, were measured. The tension test was performed until the complete failure of the sample using a screw machine. RESULTS: Two types of LDA were recognized. In LDA 1, the anterior and posterior bands lateral disc junction were directly inserted on the lateral pole, whereas in LDA 2 this lateral junction was attached behind and below the pole through a sheet of fibrous tissue. The breaking points for LDA 1 (55.8 N) and LDA 2 (28.8 N) were significantly different (P = .03). No correlation was found between the amount of LPM discal fibers insertion, sex, age, or the LDA breaking strength point. CONCLUSION: The LDA 2 insertion strongly suggests that the lateral joint ligament together with the capsule may act as a substitute for the original disc attachment to the lateral pole of the condyle.

Age Factors↗
PubMed1998

The acoustic and structural properties of the human femur.

This study evaluates the variations in the acoustic properties of the human femur at ten evenly spaced locations along its length, as well as differences that exist within given transverse sections. Six pairs of human femora, three male and three female, were sectioned, ground, and polished, and scanned with a microprocessor-driven scanning acoustic microscope. Images with a resolution of approximately 140 microns were used to calculate the average acoustic impedances for each transverse cross section and each quadrant within a cross section. The mean acoustic impedance for all the cross sections was 7.69 +/- 0.18 Mrayls. Variations were observed among the cross sections, and the central sections (4-7) had values that were statistically greater than the other more distal and proximal sections. Within the cross sections, the posterior quadrant had a lower average acoustic impedance compared to the other quadrants and this was statistically significant (Tukey's multiple comparison test). The cross sections were further analyzed to determine several geometric parameters including the principal moments of inertia, polar moment of inertia, and the biomechanical shape index. The product of the acoustic impedance and the maximum moment of inertia provided a result that attempted to account for the acoustic property variation and the change in shape at the different section locations.

Acoustics↗
PubMed1997

Scanning Acoustic Microscopy of human and canine cortical bone microstructure at high frequencies.

An Olympus UH3 Scanning Acoustic Microscope (Tokyo, Japan) has been used in the burst mode at 400 and 600 MHz to study the elastic properties of osteons and osteonic lamellae in both canine and human compact cortical bone. The nominal resolution at each frequency is within the width of an individual lamella. Three important new observations have been made regarding the acoustic properties of individual lamellae. Firstly, the acoustic impedance, as measured by shade of gray levels, of the outer most lamellae of adjacent osteons interdigitate (blend) although the structures, as determined by backscatter scanning electron microscopy, are seen to be quite separate. Secondly, in almost every osteon observed in this study, the shade of gray level for individual lamellae appear to alternate-dark, light etc.-translating to alternating compliant, stiff lamellar units respectively. Thirdly, the outermost lamella of each osteon appears to be the most compliant (darkest gray level). A preliminary SAM study of sheep femoral trabecular bone has shown the some alternation of lamellar gray levels as observed in osteonic lamellae.

Acoustics↗
PubMed1997

[Locked nail plate: a new treatment for unstable pertrochanteric fractures].

PURPOSE OF THE STUDY: This work is the outcome of a preliminary study on pertrochanteric fractures which showed that impaction with simple nail plates (SNP) was lead by hypercorrection in valgus demineralization and malposition of the nail in the femoral neck. To improve anchoring of the nail in the cervico-cephalic part, the authors propose to use a locked nail-plate (LNP), an innovative device based on the addition to the normal nail plate, of a screw securing neck and nail. MECHANICAL STUDY: Mechanical flexion and compression tests carried out on 8 pairs of femurs of fresh cadavers showed comparable rigidity for the two mounting, SNP and LNP. The difference became apparent at an equivalent load through a perforation in the SNP across the femoral head and by separation of the head from the LNP without any perforation. CLINICAL STUDY: 56 patients operated on between June 1994 and June 1996 were included 30 cases could be followed. There was only one complication: one dismantling of the plate from the diaphysis. The other 29 cases consolidated within an average of 8 weeks without any complications. Locking of the nail was effective and there was never cutting out the head by the nail nor any impaction in the focus of the fracture site. This was despite the fact that, in 12 cases there was advanced demineralization, in 8 cases hypercorrection in valgus, and in 13 cases of misalignment of the nail in the neck, all three of these being recognized as causes of articular deterioration. DISCUSSION: Pertrochanteric fractures currently represent a serious public health problem for which costs are definitely going to grow in the near future. We need a method for solid osteosynthesis simple and relatively inexpensive, but which also avoids the common mechanical complications. The LNP seems to correct SNP problems. This modification represents an improvement and should be used for any unstable pertrochanteric fracture.

Biomechanical Phenomena↗
PubMed1996

Variation in the inflammatory properties of basic calcium phosphate crystals according to crystal type.

OBJECTIVE: To determine the inflammatory potential of basic calcium phosphate (BCP) crystals, which have been identified in human joints. METHODS: Hydroxyapatite, carbonate apatite, whitlockite, and octacalcium phosphate crystals were injected in rat air pouches. Volume and cellularity of the exudate were measured. Physicochemical properties of the injected BCP crystals were determined, and correlations with the magnitude of induced inflammatory responses were sought. RESULTS: Significant differences were observed among the volumes and white blood cell (WBC) counts of the pouch exudates, based on the various crystal types used to induce inflammation. A strong correlation was demonstrated between the specific surface (SS) area of the injected crystals and the area under the curve for induced WBC count versus time (R2 = 0.88, P = 0.05). This correlation was observed for SS area values below 50 m2/gm, but when SS area increased further, this parameter plateaued. Another parameter of inflammatory response was obtained by dividing the area under the curve figuring WBC counts versus time by the corresponding SS area for each crystal type. This parameter increased linearly with the Ca:P ratio (R2 = 0.97, P = 0.0003). CONCLUSION: The inflammatory potential of BCP crystals appeared to vary according to crystal features. SS area and the Ca:P ratio (which correlates with crystal solubility) influenced inflammatory properties. These results could explain the variable clinical consequences of BCP deposits, and must be taken into account in the choice of apatite ceramics for use as biomaterials.

Animals↗
PubMed1996

Novel assays based on human growth hormone receptor as alternatives to the rat weight gain bioassay for recombinant human growth hormone.

Two methods, High-Performance Receptor Binding Chromatography (HPRBC) and Cell Proliferation (CP), have been developed as alternatives to the classical hypophysectomized rat weight gain bioassay for the determination of potency for recombinant human growth hormone (rhGH). In the HPRBC assay, rhGH is combined with an excess of the soluble extracellular domain of the recombinant human growth hormone receptor (referred to as 'receptor' in the discussion of the HPRBC assay). Nondenaturing size-exclusion chromatography is used to analyzed the resulting complex, which forms in a 2:1 receptor to rhGH ratio. The 2:1 complex is assayed at a concentration near the Kd (approximately 0.4 nM), providing high specificity for rhGH and detection of rhGH variants with reduced activity. In the CP assay, a mouse myeloid leukaemia cell line (FDC-P1) transfected with the full-length receptor is exposed to varying levels of rhGH for 16-20 h. The incorporation of 3H-thymidine into DNA is used as an index of cell proliferation. The results show that the HPRBC assay provides significantly improved precision with a relative standard deviation (RSD) of < or = 5% vs. an RSD of 23% for the rat bioassay. The CP assay has RSDs of 4-16%. Analysis of rhGH variants and mutants shows that the potencies measured by both the HPRBC and CP assays are in general agreement with the rat weight gain bioassay. Both of the HPRBC and CP assays are sufficiently rugged for operating in a Good Manufacturing Practices (GMP) routine batch release testing environment. In vitro alternatives such as the HPRBC and CP assays build a foundation for replacing the hypophysectomized rat weight gain bioassay by correlating receptor dimerization, binding specificity and signal transduction with the biological activity of rhGH.

Amino Acid Sequence↗
PubMed1996

On the mechanical characterization of compact bone structure using the homogenization theory.

In a previous paper (Crolet et al., 1993, J. Biomechanics 26, 677-687), a modelling of the mechanical behavior of compact bone was presented, in which the homogenization theory was the basic tool of computation. In this simulation, approximations were used for the modelling of the lamellae and the osteons: the lamella and the osteon were divided into cylindrical sectors, each sector being approximated as a parallelepiped having a periodic structure (fibrous composite for the lamella, superimposition of plates for the osteon). The present study deals with a new model without these approximations. First, it can be proved that the homogenized elasticity tensor for a lamella, which has non-periodic structure, is obtained at each geometrical point as a homogenized tensor of a periodic problem. Similarly, for the osteonal structure, the components of the homogenized tensor are determined at each point as the result of a periodic homogenization. The software OSTEON, which is the computational method associated with this model, allows one to obtain a better understanding of the effects of many bony parameters. The obtained results are in accordance with experimental data.

Algorithms↗
PubMed1996

[Axillary lymphoceles after breast cancer surgery. Pathogeny, prevention].

We report a retrospective series of 126 patients seen in 1992 for conservative surgery (group T) or Patey procedure (group P) for breast cancer. We looked for factors predictive of axillary lymphocele and their prevention. Axillary lymphadenectomy performed in patients undergoing surgery for breast cancer leads to a certain degree of morbidity including the development of lymphoceles. The mean number of lymph nodes removed was 16 in group T and 19 in group P. Mean lymphorrhea was 741 cm3. Two factors were significantly implicated in the pathogenesis of postoperative lymphorrhea : the number of nodes resected (p < 0.005) and obesity (p < 0.001). Prevention of lymphoceles requires meticulous lymphostasis and reduction of the surgical detachment spaces.

Adult↗
PubMed1995

[Bradycardia during treatments of weight loss].

Sinus bradycardia was observed in 10 adolescents participating in a weight loss diet conducted in a health centre. The precise cause was assessed. The subject's age ranged from 10 to 15 years and weight loss ranged from 8 to 24 kg over a period ranging from 8 to 23 weeks. None of the subjects had taken drugs with a bradycardic effect and search for toxic agents in the blood and urine was negative in all cases. Infection was suggested since 8 of the 10 adolescents had a rhinopharyngitis a few weeks before the discovery of bradycardia. This cause was not retained due to the lack of any signs of infection or inflammation and negative virus serology. Nutritional status was therefore retained as the most likely cause in these adolescents who were eating a diet containing < or = 1350 kcal/day. This hypothesis was supported by the results of work reported in 1970 showing arrhythmia in very low calorie diets. The effect is essentially related to the biological value of proteins in the diet, its duration and the initial weight of the subjects. In addition bradycardia is frequently seen in subjects taking hypocaloric diets or with anorexia nervosa and should be considered as an adaptation to hypometabolism rather than a true heart disorder. Thus the biological value of the proteins and the mineral status should be taken into consideration during the course of low calorie diets, even though bradycardia is frequent and does not require a specific treatment. Therefore heart rate and decreasing rate of weight loss should be carefully followed during the course of low calorie diets.

Adolescent↗
PubMed1995

[Experimental capsulo-ligamentar lesions of the knee during passive hyperextension. Biomechanical aspects. A lesional evaluation and consequences].

PURPOSE OF THE STUDY: Passive hyperextension is a rare mechanism of injury of knee ligaments in clinical practice. The lesions are often complex and no consensus exists about their sequence. Our purpose was to study the mechanical behavior and the anatomical lesions of the knee following passive hyperextension until rupture. MATERIAL AND METHODS: 12 pairs of fresh human cadaveric knees were tested after resection of soft tissue except for the ligaments and the Popliteus muscle. Some of them had specific ligaments sections (PCL or posterior capsule). We used a "four point bending" model at a constant rate (V = 3 10E-4 m/s) and measured failure torque and bending stiffness of the knee. Results were expressed as percent of the response of the normal contra lateral knee. RESULTS: A wide range of absolute data was noted and correlated to the age and bone quality. Bony avulsion was constant. The posterior capsule was the first structure injured at an average of 23 degrees of recurvatum, followed by the posterolateral ligament. The PCL was the ultimate structure to fail at its femoral attachment, preceding complete dislocation of the knee. No ruptures of the ACL and medial collateral ligament were noted. After section of the posterior capsule, the stiffness of the knee decreased 40 to 80 percent compared to the normal opposite knee, whereas the isolated section of the PCL had no significant effect. DISCUSSION: The method used in this study appears reliable. "The four point bending" is a reproducible model and the use of paired specimens allows a quantitative approach. The use of elderly specimens at a low strain rate in this experiment remains a questionable point. Passive hyperextension is characterized by automatic external rotation resulting in asymmetrical posterior lesions and tears of the PCL at its femoral attachment. On the contrary, active hyperextension of the knee can produce ACL injury by anterior translation of the tibia under the femur consecutive to Quadriceps femoris contraction. CONCLUSION: Our experimental model is an effective and reproducible method to create passive hyperextension of the knee. The first structure to fail is the posterior capsule followed by the posterolateral ligament. The PCL is the ultimate structure to fail and no ACL rupture has been noted before dislocation. CLINICAL RELEVANCE: if passive hyperextension mechanism is suspected, isolated posterior capsule lesion may occur and should be repaired. On the contrary, PCL tear should never be isolated and always associated with peripheral ligament injuries.

Anterior Cruciate Ligament↗
PubMed1995

[Orthopedic biomaterials].

It is very challenging to insure long term security and effectiveness for joint arthroplasties, artificial ligaments, extensive bone replacement and some other orthopaedic biomaterials. How can we predict the long term security and efficacy of such an implant? Only an interdisciplinary approach can provide a satisfactory answer. The surgeon must define the needs, he must find the appropriate surgical techniques and conduct the clinical trial. The material scientist must elaborate safe and secure materials with regards to their biotolerance and mechanical resistance. This has to be performed in close connection with the biomechanics lab. Biomechanic Science must predict the expected stresses. It has to design special simulator to quantify in vitro material toughness, wear characteristics, lubrication, behaviour and surface deformation. Biological and mechanical standardized tests have to be carried on. Then it is possible to conduct a clinical trial, prospectively in comparison to another already developed material. Clinical studies could serve to measure efficacy and radiological modification. After failure, it is possible to analyse retrieved specimen, to measure the material degradation in real environment, to perform biological studies on retrieved tissues i.e. : macrophagic activities, tissue response, bone ingrowth, inflammatory or immunological reaction. For more than twenty years we worked on alumina against alumina total hips. The idea was to develop a low debris system to enhance long term longevity of the prosthesis. The Charnley design has proven its effectiveness for more than fifteen years, but polyethylene wear is responsible for late failures. This is specially crucial for young patients, male sex and high activity level patients. At the beginning, biological studies and mechanical tests were performed, it appeared that the biological tolerance of alumina ceramic was excellent, the fracture toughness was adequate, but there were some problems related to alumina fixation in the body and also alumina head fixation on metallic stem. Alumina material improved with time. It was possible to diminish the fracture risks and to increase the safety. Parallel information from the first period was used to increase the material quality, the surgical techniques and also to define indication in the use of such material. It is now clear and it also has been published that alumina against alumina system has proved to be as safe as Charnley total hips. It has been proved to give better results in the young age population. Then it is now possible to operate on very young patients, to allow these patients to perform heavy work, sports and regular daily activity for their demand.(ABSTRACT TRUNCATED AT 400 WORDS)

Biocompatible Materials↗
PubMed1994

Analysis of the general features of the soft tissue response to some metals and ceramics using quantitative histomorphometry.

This article analyzes the general features of the tissue response to orthopedic biomaterials when implanted in the paraspinal muscles in rats for periods between 1 week and 1 year. Using a computer-assisted cell counting method, it was shown that the membrane thickness was a stable parameter that poorly correlated with the other histomorphometric parameters except fibrocyte distance parameters. Macrophages were significant in number only in the short term and were always located at the implant-tissue interface. At 4 weeks, the period corresponding to which macrophages disappeared, fibrocytes were found nearer the interface than at earlier periods and did not migrate for up to 52 weeks, although their densities decreased to 50% of their initial values. Therefore, it can be histomorphometrically confirmed that 1) the presence of an implant induced a delay in the healing process; 2) the immune system was not usually involved in the response to bulk metals; and 3) at early time periods, the presence of PMN cells was correlated to the long-term number of macrophages. On the contrary, the histomorphometric findings suggested that around the tested materials, a large number of macrophages did not induce an immediate or a delayed fibrocyte proliferation. If one considers that a low fibrocyte surface density is related to activated cells surrounded by a matrix high in collagen content, then the large number of macrophages induced the stimulation of collagen synthesis by the fibrocytes already included in the membrane. Accordingly, in the short-term, a high fibrocyte density and few macrophages may be a criterion for testing biocompatibility.

Animals↗
PubMed1993

Circulating stable antigens at higher levels down-regulate antibody responses to Plasmodium falciparum.

A study involving 169 schoolchildren (5-14 years old) living in Manarintsoa near Antananarivo (Madagascar, East Africa) was performed during the seasonal malaria transmission period. For the whole population examined, the prevalence of Plasmodium falciparum and the rates of spleen enlargement and of circulating stable antigen (S-Ag) were found to be 60.9%, 71.7%, and 46.8%, respectively. The prevalence of IgG antibody to RESA (ring-infected erythrocyte surface antigen) was 42.7% and that of IgG and IgM antibodies to E-Ag (exoantigens) was 44.9% and 2.9%, respectively. The positive rates for IgG and IgM antibodies to Som-Ag (somatic antigen) were 48.5% and 5.9%, respectively. Concerning S-Ag, no significant relationship was observed for parasitemia, spleen size, age, or IgM antibody responses to exoantigens (E-Ag) or to somatic antigen (Som-Ag). Levels of S-Ag were found to be related to IgG antibodies to E-Ag. Our results suggest that S-Ag at low levels may participate in the mechanisms involved in the development of the IgG antibody responses to E-Ag and to Som-Ag, whereas at a comparative population level, higher quantities of S-Ag down-regulate antibody responses to P. falciparum. The data we obtained were compared with those gathered in another malaria mesoendemic area (Bobo-Dioulasso, Burkina Faso, West Africa), where lower levels of S-Ag were found.

Adolescent↗
PubMed1993

Compact bone: numerical simulation of mechanical characteristics.

One of the main difficulties encountered in the numerical simulation of the anisotropic elastic characteristics of compact bone is to account for the Haversian microstructure when determining the overall macroscopic behavior. Engineering analyses of such problems are usually based on 'homogenized approximations'. Compact bone is not exactly a composite material, but rather a heterogeneous medium which exhibits a multiscale composite structure. If the homogenized approximation is precise enough (and this is true for the mathematical theory of homogenization), it is then possible to simulate the macroscopic behavior from the microscopic mechanical characteristics. The present paper is devoted to such mathematical developments. Moreover, the 'inverse simulation' allows the computation of the microscopic stress fields in the haversian structure from the macroscopic stress fields, taking into account bone microstructure.

Biomechanical Phenomena↗
PubMed1993

Disc movements over the condylar head. Radiographical study on autopsy materials.

A radiographical study has been performed to evaluate the movement of the disc posterior band over the condylar head during mandibular opening. Six formal free embalmed subjects were selected as 'normal'. Micro stainless steel balls were used as landmarks both into the bone and into the disc for X-ray identification. The data was processed at each phase of movement in selected planes. The true coordinates of each disc landmark gave the potential to calculate the linear length of their path and any distance change between them. It can be concluded that there is a 5% width reduction during the opening movement and it also suggests strongly that a fair amount of translation movement between the disc and the condyle occurs in the lower compartment.

Cadaver↗
PubMed1993

Scanning acoustic microscope studies of the elastic properties of osteons and osteon lamellae.

Scanning acoustic microscopy (SAM) provides the means for studying the elastic properties of a material at a comparable level of resolution to that obtained by optical microscopy for structural studies. SAM is nondestructive and permits observation of properties in the interior of materials which are optically opaque. Two modes of ultrasonic signals have been used in a Model UH3 Scanning Acoustic Microscope (Olympus Co., Tokyo, Japan) as part of a continuing study of the microstructural properties of bone. The pulse mode, using a single narrow pulse in the range of 30 MHz to 100 MHz, has been used to survey the surface and interior of specimens of human and canine femoral compact cortical bone at resolutions down to approximately 30 microns. To obtain more detailed information at significantly higher resolution, the burst mode, comprised of tens of sinusoids, has been used at frequencies from 200 MHz to 600 MHz. This has provided details of both human and canine single osteons (or haversion systems) and ostenoic lamellae at resolutions down to approximately 1.7 microns, well within the thickness of a lamella as viewed in a specimen cut transverse to the femoral axis.

Animals↗