D. Hartmann

Hypertrophic repair of articular cartilage in experimental osteoarthrosis.

Section of the anterior cruciate ligament has been performed in the knee of 11 mature dogs. The macroscopically normal cartilage from patella and femoral trochlea of animals killed from 2 to 32 weeks after operation was used for histological, histomorphometrical, and biochemical analysis. Previously undescribed degenerative lesions of the superficial matrix were observed, and there was evidence for secondary healing of these lesions. An early and progressive decrease in superficial cell density and a later progressive increase in cartilage thickness without any change in the cell density of the middle and deep cartilage layers was found. A slight increase in water content with no reduction in glycosaminoglycan content was observed. The results suggest that joint laxity results initially in superficial degenerative changes and later in hypertrophic regenerative changes due to cell proliferation and increased matrix synthesis. Hypertrophic remodeling of articular cartilage in response to abnormal mechanical stresses is postulated.

Reactions to a bovine collagen implant: Clinical and immunologic study in 705 patients

A small percentage of patients treated with bovine collagen implants have adverse reactions involving both the cellular and humoral types of immune response. We report a clinical follow-up of 705 subjects treated with a new bovine collagen implant, Atelocollagen (Koken Co. Ltd., Tokyo, Japan). Sensitization to the implant was evaluated in all subjects by skin testing, and humoral response was monitored in 166 subjects by measuring the level of circulating antibodies directed against bovine collagen. Twenty-seven patients (3.8%) exhibited a positive response to a skin test, and of the remaining 656 patients, an adverse reaction to the implant developed in 2.3%. We found a strong correlation between the presence of antibodies to collagen and a positive response to skin testing (92%) or an adverse reaction (100%). In the case of a borderline clinical response to bovine collagen implantation, anticollagen serologic tests appeared to be a useful tool for the identification of clinically reactive patients.

In vitro and in vivo evaluation of an alumina–zirconia composite for arthroplasty applications

In order to improve the reliability and the mechanical properties of orthopaedic hip prosthesis, new ceramic composites starting with nanosized powders of alumina and zirconia have been recently developed. The aim of the present study was to investigate the biological tolerance of one of these sintered ceramics and of its alumina and zirconia constitutive nanosized powders with both in vitro and in vivo approaches. At first, osteoblasts and fibroblasts were cultured either upon sintered ceramic discs with polished or rough surfaces or in the presence of the corresponding alumina or zirconia powders at various concentrations. Thereafter, we chronically injected these powders in the knee articulation of rats. In vitro, the materials showed no deleterious effect on cell proliferation, extra-cellular matrix production (human type I collagen and fibronectin) or on cell morphology. In vivo, the histological examination showed only a very moderate and non-specific granulomatous response of the synovial membrane but no major inflammation as clinically described with metals or polyethylene wear debris. Besides its improved physical properties, this recently developed alumina-zirconia composite showed satisfactory biocompatibility.

Direct silanization of zirconia for increased biointegration

High-performance bioinert ceramics such as zirconia have been used for biomedical devices since the early seventies. In order to promote osseointegration, the historical solution has been to increase the specific surface of the implant through roughness. Nevertheless these treatments on ceramics may create defects at the surface, exposing the material to higher chances of early failure. In zirconia, such treatments may also affect the stability of the surface. More recently, the interest of improving osseointegration of implants has moved the research focus towards the actual chemistry of the surface. Inspired by this, we have adapted the current knowledge and techniques of silica functionalization and applied it to successfully introduce 3-aminopropyldimethylethoxy silane (APDMES) directly on the surface of zirconia (3Y-TZP). We used plasma of oxygen to clean the surface and promote hydroxylation of the surface to increase silane density. The samples were extensively characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle, mechanically tested and its cytotoxicity was evaluated through cell adhesion and proliferation tests. Additionally, aging was studied to discard negative effects of the treatment on the stability of the tetragonal phase. No adverse effect was found on the mechanical response of treated samples. In addition, plasma-treated samples exhibited an unexpectedly higher resistance to aging. Finally, silane density was 35% lower than the one reported in literature for silica. However cells displayed a qualitatively higher spreading in opposition to the rounder appearance of cells on untreated zirconia. These results lay the foundations for the next generation of zirconia implants with biologically friendlier surfaces.nnnSTATEMENT OF SIGNIFICANCEnThe use of zirconia-based ceramics in biomedical devices is broad and well accepted, especially in dental implants. However, they do not bond naturally to bone, therefore to ensure fixation surgeons typically rely on roughness at different scales, or on cements. Alternatively in this work we present a new perspective of surface modification through chemistry to enhance the interaction between surface and biological environment, without the downsides of roughness. This surface treatment is proposed for zirconia, which allowed a direct silanization of its surface and a higher cell attachment. The results of this research may open the possibility for the next generation of bioinert ceramic implants with more advanced tailored surfaces for increased osseointegration.

Adhésion bactérienne aux implants intraoculaires et prévention de l'endophtalmie

L′adhesion bacterienne aux implants intraoculaires (IOLs) lors de leur implantation est un facteur etiologique reconnu des endophtalmies postoperatoires. Le polypropylene a ete le premier biomateriau pour lequel la relation de cause a effet entre adhesion bacterienne et endophtalmie a ete prouvee. L′adherence aux IOLs a fait l′objet de plusieurs etudes in vitro , certaines personnelles, et des resultats contradictoires ont ete rapportes, du fait entre autre de conditions experimentales differentes (temps d′incubation des IOLs et methodes employees). L′adherence est egalement affectee par la nature de l′IOL, des souches bacteriennes et du milieu environnant, complexe a modeliser. Nous avons donc recemment conduit une etude in vivo et determine l′evolution de la quantite de Staphylococcus epidermidis ayant adhere a cinq types d′IOLs. Enfin, peu d′etudes epidemiologiques ont porte sur les relations possibles entre endophtalmie et le type d′IOL. En 2004, le biomateriau parfait qui pourrait prevenir l′endophtalmie postoperatoire n′existe pas encore. Globalement, les materiaux hydrophiles et les acryliques hydrophobes semblent etre moins adhesifs que le silicone ou le PMMA, mais ceci reste a prouver en clinique humaine.

Implant intraoculaire et adhésion bactérienne : influence des conditions environnementales, des propriétés bactériennes et des caractéristiques du biomatériau

Adhesion of bacteria to intraocular lenses is an important step in the pathogenesis of postoperative endophthalmitis. It can be described as a two-phase process including an initial, instantaneous, and reversible phase followed by a time-dependant and irreversible molecular and cellular phase. The binding of bacteria is affected by many factors including environmental factors such as medium composition, presence of proteins and flow conditions, the bacterial cell surface characteristics, and the materials surface properties. This article reviews all these factors affecting the adhesion of bacteria to intraocular lenses. A better understanding of these mechanisms would make it possible to reduce the bacterial adhesion process and thus could help decrease the incidence of postoperative endophthalmitis.

Biofilms à Staphylococcus epidermidis à la surface des implants intraoculaires

Bacterial adhesion to intraocular lenses (IOLs) takes place during their implantation. This is a prominent etiological factor of postoperative endophthalmitis. Following adhesion, secretion of an extracellular matrix (called slime for Staphylococcus epidermidis) and formation of multiple layers of microcolonies lead to the colonization of the biomaterial surface. Scanning electron microscopy photographs illustrate the different steps of biofilm formation. The different adhesins expressed by S. epidermidis involved in the adhesion process are described. The biofilm is not only an adhesive medium; it also affects virulence. Last, notions on biofilm physiology are discussed in an attempt to explain the dynamic equilibrium of this system. In 2004, the perfect biomaterial able to prevent postoperative endophthalmitis does not yet exist. Moreover, there is no effective tool, at the present time, to fight against mature biofilms. Therefore, preventing biofilm formation remains capital, which requires perfect knowledge of all stages of formation and the factors involved.

Endophtalmie : étiopathogénie et antibioprophylaxie

Postoperative endophthalmitis is still one of the most fearsome complications of cataract surgery. The present reviews aims are to study the etiology and pathogenesis of endophthalmitis and the criteria for antibiotic prophylaxis. Endophthalmitis prevalence is 0.07%-0.32% in cataract surgery. The clinical presentation needs to be perfectly known, even if none of the signs is pathognomonic. Bacteria predominantly cultured in postoperative endophthalmitis are gram-positive, especially Staphylococcus epidermidis. Most of the bacteria come from the patient. Bacterial adhesion to intraocular lenses (IOLs) takes place during their implantation, a prominent etiological factor. Polypropylene was the first biomaterial that proved this relation of cause and effect between bacterial adhesion and endophthalmitis. The benefit of antibiotic prophylaxis during cataract surgery has yet not been proven, since the low prevalence of endophthalmitis makes controlled studies with a large cohort difficult. The criteria and the four possible administration approaches (topical, subconjunctival, irrigation liquid, systemic) are analyzed.