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Biomedical subjects

P Christel

Publications and source records attributed to P Christel.

At least 55 records · Page 3Linked to original sources
PubMed1990

[Total hip prosthesis in patients less than 50 years of age. Value of ceramic materials].

87 consecutive cases of sealed total hip prosthesis with an alumina/alumina friction couple, placed in 76 patients less than 50 years old, have been studied. The surveillance period ranged between 2 and 13 years for 74 of them. 51 have been followed over more than 5 years, 10 have been lost out of sight and 3 died. 5 failures are to be deplored, one by fracture of a 22 mm ceramic head, the normal size in this series being 32 mm; the 4 others occurred after 6, 6, 10 and 11 years and are the consequence of a cotyloid loosening. Compared to the other series in literature concerning young patients and therefore those considered to be "at risk", the results obtained are better, especially if the high number of cases re-operated upon in this series (18 prosthesis exchanges out of 87) is taken into account. The actuarial method of Kaplan Meier gives a probability of 94% of keeping the prosthesis for 8 years. It is undoubtedly the quality of the design of the titanium femoral stem and especially the small amount of erosion scraps produced by the alumina/alumina couple which explain this result. The hip replacement must however remain an exceptional indication in a young subject.

Adult↗
PubMed1989

[Strategies for the use of complementary tests in menisco-ligamentous pathology of the knee].

In patients with menisco-ligamentous pathology of the knee, the paraclinical examinations available to physicians and surgeons are standard radiography, arthrography, arthroscopy and magnetic resonance imaging (MRI). The use of these methods on whether the lesions are recent or chronic. Standard radiography and arthrography are sufficient to evaluate chronic lesions, arthroscopy and MRI being reserved to cases with complex laxity. For recent lesions standard radiography must systematically be performed. Arthrography is unreliable, being hampered by haemarthrosis and pain. Arthroscopy may be hazardous and can only be used in patients without peripheral lesions of the articular capsule and ligaments. MRI is sometimes useful, notably in cases with unrecognized post-traumatic haemarthrosis and in children as it avoids hospitalization. In this article, the various situations encountered are analyzed and a strategy for the use of paraclinical examinations is offered.

Arthrography↗
PubMed1989

Mechanical properties and short-term in-vivo evaluation of yttrium-oxide-partially-stabilized zirconia.

Yttrium-oxide-partially-stabilized zirconia (YPSZ) belongs to a new class of ceramics exhibiting an improved toughness when compared to alumina. The toughening mechanism is related to a martensitic-like transformation of tetragonal metastable grains into a monoclinic state occurring at the crack tip. Specific tests showed that YPSZ exhibited a high bending strength (900-1200 MPa), a low Young's modulus (200 GPa), and a high toughness (KIC = 9-10 MN/m3/2). Its average grain size of 0.5 microns allows a surface roughness as low as 0.008 microns. Sterilization or aging in saline solution at room temperature for 100 days did not affect the toughness of this material. Cylindrical YPSZ samples, manufactured by cold isostatic pressing and sintering, were implanted in the paraspinal muscles in the rat up to 12 weeks. The tissue reaction was evaluated with reference to alumina (ISO requirements) by means of quantitative histomorphometry. No significant differences were found between YPSZ and alumina for both the membrane thickness and cell distributions surrounding the implants.

Aluminum Oxide↗
PubMed1989

Comparison of coral resorption and bone apposition with two natural corals of different porosities.

Previous studies showed that natural coral implanted into bone tissue was gradually resorbed and progressively replaced by newly formed bone. The objectives of this study were to compare the fate of two Madreporian corals, Porites and Acropora, after implantation during 1 and 2 months into sheep and pig long bones. These materials are identical in composition (CaCo3) but differ in volume (49 +/- 2%, 12 +/- 4%, respectively) and mean size (250 vs. 500 microns) of porosities. The non-decalcified histological slices were observed under light microscopy. Implant resorption and new bone formation were quantified through an automatic image analysis system. Quantitative results showed that the larger the porosity volume, the greater was the coral resorption as well as the new bone apposition. Large differences were found between the two animal species. Histological findings were identical to those previously reported: implants were resorbed and progressively replaced by newly formed bone. Coral was found to be an osteoconductive biomaterial which acted as a scaffold for a direct osteoblastic apposition and consequently could be an interesting alternative to bone auto-, allo-, or xenografts.

Animals↗
PubMed1989

A histomorphometric comparison of the muscular tissue reactions to high-density polyethylene in rats and rabbits.

In order to bring quantitative elements into the rational selection of animal species for the evaluation of in vivo compatibility of biomaterials, a comparison between the muscular tissue response of rats and rabbits was made using quantitative histomorphometry. The experimental model was based on the quantification of the tissue reaction to specimens made of ultra-high-density-polyethylene (UHDPE) implanted in the paravertebral muscles, according to ASTM F-469 standard. The tissue reaction was evaluated by digitization of both the encapsulating membrane contours and the different cell types located within it. In each animal species, the cell distribution from the interface exhibited an asymetric bell-shape curve with a maximum close to the interface, corresponding to a three-parameter statistical model. The membrane thickness, a fibrocyte-related parameter, was larger in the rabbit, but its time-course was identical in each species, showing a late and significant increase. Few differences were observed for most cell types due to the low level of foreign-body-reaction induced by HDPE implants. Although there were interspecies differences for fibrocytes and, to a lesser extent, macrophages, between 2 and 8 weeks, there was no statistical differences for any of the computed parameters either at 2 weeks or between 26-week rats and 52-week rabbits. The quantitative histomorphometry picked up differences between close tissue responses, whereas the qualitative observation was unable to demonstrate distinguishing differences between rats and rabbits.

Animals↗
PubMed1989

Wear analysis of retrieved alumina heads and sockets of hip prostheses.

The wear behavior of hip prostheses alumina components was studied on 20 retrieved implants removed for socket loosening. The observed wear takes two forms: a running-in of the mating surfaces and a gross disruption of the surfaces. The running-in is very shallow, in the order of 0.2 micron after 8 years of implantation. This is observed on the load-bearing areas of the components. Gross wear is not material-related but had always been associated to a high contact pressure between the edge of the socket and the femoral head. Such a high contact pressure occurs after the socket had loosened and then tilted or if it was initially positioned too vertically. The long-term success of alumina-alumina THP components depends essentially upon biomechanical considerations and upon the quality of the material. The area of contact between the head and the socket should be large enough to minimize the contact stresses. This can only be achieved by a good positioning of the socket and by a close tolerance fit of the alumina components; any deviation from sphericity should also be avoided. The normal wear behavior of alumina is a running-in process leading to an average wear rate of 0.025 micron/year as compared to 100 microns/year for UHMWPE on metallic heads.

Aged↗
PubMed1989

The evaluation of bone remodeling about orthopaedic implants with ultrasound.

Total hip arthroplasty causes biomechanical changes in the normal femur, including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Two complementary ultrasonic techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. An ultrasonic wave propagation technique was used to determine elastic properties and a new scanning acoustic microscope (SAM) mapped the acoustic impedance profile of each section. The effects of the implantation of two types of hip prostheses, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis, were investigated. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.

Aged↗
PubMed1988

The use of dense alumina-alumina ceramic combination in total hip replacement.

The purpose of this article was to review the laboratory and clinical performances since 1970 of a total hip prosthesis using alumina-alumina combination. The chemical and physical properties of dense alumina ceramic were studied in relation to biocompatibility, mechanical strength, and surface properties. Through the examination of 35 retrieved implants, it was found that the long-term success of alumina-alumina total hip replacement depends on both the ceramic microstructure (small grain size with uniform distribution, minimum porosity, absence of inclusions) and implant geometry (sphericity deviation +/- 1 micron, radius tolerance between components 7-10 microns). Alumina component wear and fractures have disappeared with the use of high-performance materials and severe manufacturing quality control. Examination of human biopsies from well-fixed prostheses showed that alumina particles deposits increase with time with only a low-grade macrophagic reaction. When loosening occurred, an inflammatory reaction appeared; this reaction was less striking than with loose metal-polyethylene prostheses, however. The long-term behavior of cementless alumina cup fixation depends upon initial positioning and stability; survivorship analysis of the cemented ceramic cups showed an 88% survival probability after 8 years with a 1.6% average annual probability of revision. The percentage of surviving was 100% after 8 years in patients who were less than 50 years old. Aseptic loosenings occurring at the cup-cement interface were assumed to be related to stress protection secondary to the high rigidity of the ceramic leading to a weakening of the spongious bone supporting the cement mantle. Good bone stock quality as well as high-quality ceramic appear to be the prerequisites for durable fixation of alumina sockets.

Aluminum↗
PubMed1988

A reflection scanning acoustic microscope for bone and bone-biomaterials interface studies.

A relatively simple scanning acoustic microscope (SAM) that operates in the reflection mode has been constructed. The system uses a 20 MHz spherically focused transducer, acting both as transmitter and as detector, to obtain acoustic impedance information on a thin surface layer at a maximum resolution of approximately 100 micron. The specimen is mounted on an X-Y driving system (precision, 5 micron) under computer control in order to scan a grid of 256 x 256 points across areas ranging from 6.5 to 1300 mm2. An algorithm is used to reference the data against standards; specially developed software provides for pseudo-color mapping, three-dimensional images, zooming to 16 x magnification, contouring, and single line profiles of the data. The system has been used to determine inhomogeneities in surface acoustic properties of mineralized tissues and implant materials, in many cases as a complement to using ultrasonic wave propagation techniques to measure the bulk anisotropic properties.

Adult↗
PubMed1988

[Validity and diagnostic value of magnetic resonance imaging in traumatic menisco-ligamentous pathology of the knee. Prospective study of 22 knees].

Twenty-two patients were prospectively examined by magnetic resonance imaging to determine the diagnostic validity of the method in the assessment of traumatic lesions of the menisci and ligaments of the knee. All the patients had their lesion verified by arthrotomy with or without arthroscopy. The accuracy of magnetic resonance imaging in the detection of lesions of the medial menisci, lateral menisci and cruciate ligaments was respectively 82, 91 and 100 per cent. Its specificity for lesions of the same structures was 92, 100 and 100 per cent. Lesions of the articular cartilage and of the peripheral ligaments were detected with an accuracy of 100 and 95 per cent and a specificity of 100 per cent. Thus magnetic resonance imaging presents a high level of reliability in the detection of ligamentous and cartilaginous lesions. It is less reliable for the detection of meniscal lesions because of the number of false positives and false negatives, which is not negligible. However its demonstrable diagnostic value will increase with improved knowledge of the pathology of imaging and with technical improvements. Its three-dimensional features and the fact that it is totally non-invasive give to this method a great future in the field of the traumatic pathology of the knee. In the steps leading to the diagnosis of meniscal and ligamentous lesions of the knee, magnetic resonance imaging has an interesting place in the field of recent lesions and may avoid the need for hospitalization.

Adult↗
PubMed1988

[Percutaneous arthrolysis under arthroscopic control and manipulation under anesthesia in the treatment of postoperative stiffness of the knee].

In the post-operative management of surgery of the knee complicated by stiffness, the results of manipulation under anaesthesia and percutaneous release of adhesions under arthroscopy have been compared in two groups of twenty and twenty-four patients. The two groups were identical in age, 32 years, in the cause, which was ligamentous surgery in 85 per cent and in their level of activity. Arthroscopic release was performed in 90 per cent of cases under continuous peridural anaesthesia whilst manipulations were performed under general anaesthesia in 75 per cent of cases. The mean duration of follow-up was 13 months in arthroscopic releases and 29 months in manipulations. Pre-operative limitation of flexion to 57 degrees in arthroscopic releases and 67 degrees in manipulations under anaesthesia improved to 124 degrees and 134 degrees respectively at the last follow-up. The speed of recovery proved to be twice as rapid in patients with arthroscopic release - 3.2 months compared with 6.1 months for straightforward manipulations. Manipulations under anaesthesia were followed by 6 patello-femoral syndromes (30 per cent) whilst arthroscopic release only had 4 syndromes (18 per cent). Arthroscopic releases and manipulations under anaesthesia made before the end of the third month after operation gave better results than those performed later. However, arthroscopic release can be done very late compared with manipulation under anaesthesia and avoids the need for surgical arthrolysis.

Adolescent↗
PubMed1987

[Magnetic resonance imaging in lesions of the plantar aponeurosis].

Exploration of sporting injures to plantar aponeurosis (PA) has up to now been based mainly on clinical examination, from which the diagnosis was established. Imaging technics such as standard radiography and ultrasound scanning have limitations allowing diagnosis to be made usually only by elimination, the lesion being very rarely visualized directly. Ten patients with hyperalgic lesion of plantar arch and functional impotence were explored by MR imaging, and in all cases this examination provided superior data confirmed at operation. The examination is painless and little invasive and can be carried out during the acute phase. The plantar aponeurosis is visualized directly between the muscle mass of the plantar arch and the fatty cushion. All three spatial planes can be investigated, most interesting data being obtained from the sagittal (in the PA axis) and frontal (comparative) planes.

Adult↗
PubMed1987

Development of a carbon-carbon hip prosthesis.

This article deals with the use of carbon-fiber-reinforced-carbon materials for the manufacture of hip prosthesis stems. It considers the manufacturing process of carbon-carbon (C-C) composites made of carbon fibers infiltrated either with dense pyrolytic carbon or silicon carbide (SiC) through chemical vapor infiltration. The chemicophysical properties of these composites are examined according to their structures. The long-term response (2 years) of cortical bone to various types of carbon-carbon was evaluated mainly for bone contact and ingrowth. Carbon-carbon coated with calcium phosphate was found to speed up the bone formation as compared to pyrolytic carbon or SiC coatings. The low modulus of elasticity of the C-C materials could be responsible for quicker bone contact as compared to a much stiffer material like sintered aluminum oxide. The biomechanical performance of C-C hip stems was assessed through (a) implantations into cadaver femurs, (b) fatigue testing, and (c) finite element analysis. These tests showed: (a) a better stress transfer as compared to a metal prosthesis having the same design, (b) no fatigue damage, (c) a computerized stem stress distribution in accordance with the fractures obtained during static mechanical testing.

Biocompatible Materials↗
PubMed1987

[The role of peripheral capsulo-ligamentoplasties in the treatment of chronic anterior instability of the knee. Apropos of a series of 104 cases].

The authors have studied the results of 91 extra-articular ligamentoplasties amongst 104 knees treated surgically for chronic anterior laxity of the knee. The technique used in 40 cases was a Lemaire isolated lateral extra-articular ligamentoplasty using a strip of fascia lata and in 51 cases a double plasty, combining the same lateral plasty with a tightening of the posteromedial capsule and a forward transfer of the semimembranosus. The follow-up was from one to seven years, with a mean of four years. The results were assessed using the "ARPEGE" (Research Association for the Study of the Knee) scoring system, based on ability to undertake sports, functional stability, pain, resistance to fatigue, mobility and residual laxity. The overall results were excellent in 51 per cent, good in 10 per cent, fair in 10.5 per cent and bad in 28.5 per cent of cases. These results may seem to be unsatisfactory but a detailed study of the failures showed some errors in the indications for surgery which could have been avoided by a full appreciation of the type of laxity, the post-operative needs of the patient, his age and the level of sporting activity. Meniscectomy and lesions of the articular cartilage had a disturbing effect on the results. This study indicates a more precise place for extra-articular ligamentoplasties compared with in situ reconstructions of the anterior cruciate ligament.

Adolescent↗