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Biomedical subjects

S Perren

Publications and source records attributed to S Perren.

18 recordsLinked to original sources
PubMed2006

Caregivers' adaptation to change: the impact of increasing impairment of persons suffering from dementia on their caregivers' subjective well-being.

As progressive dementia involves changes in patients' behaviour and cognitive and functional abilities, dementia caregiving can be considered as a process that demands continuous adaptation to change. The current intervention study investigated associations between the course of dementia patients' impairment and their caregivers' well-being over two years. One hundred and twenty-eight care recipient-caregiver dyads participated in a controlled randomised intervention study (psycho-educational group intervention), 99 dyads in which the care recipients still lived at home participated in the second assessment, and 75 dyads in the third assessment. Caregivers were interviewed about their subjective well-being (emotional well-being and life satisfaction) as well as care recipients' behavioural problems and functional disability. Care recipients completed various neuropsychological tests. The assessments were repeated one and two years later. The psycho-educational intervention had a positive impact on caregivers' well-being. Level and increase in behavioural problems and increases in cognitive and functional impairment negatively affected caregiver well-being over time. For participants from the control condition the negative association between increase in impairment and decrease in caregiver well-being over time was stronger than for the caregivers in the intervention group. Our results suggest that it is not only the severity of current problems and stress, but also the rate of change, that is important for caregivers' well-being. Psycho-educational group intervention may help caregivers to adapt to the increasing impairment of care recipients with dementia.

Adaptation, Psychological↗
PubMed2001

Polylactide implants and bacterial contamination: an animal study.

Although bioresorbable aliphatic polyesters derived from lactic acid are now used clinically as sutures, bone-fracture fixation devices and sustained-release drug-delivery systems, very little is known about their behavior in the infected environment. The aim of the present study was to compare the resistance to infection of two polylactide implants with different degradation characteristics, and to evaluate the influence of a bacterial challenge on their mechanical and physicochemical properties. Various quantities of a beta-haemolyzing strain of Staphylococus aureus (V 8189-94) were inoculated into the medullary cavity of rabbit tibiae, and an extruded polylactide rod composed of either P(L)LA (Poly(L-Lactide)) or P(L/DL)LA (Poly(L/DL-Lactide)) was then inserted. Animals were sacrificed four weeks after surgery. The tibiae and implants were removed under sterile conditions and evaluated microbiologically by culturing. The severity of infection was graded according to positive colony-forming units in the bone. The mechanical properties of the retrieved implants were assessed by 4-point bending and shear tests, performed in compliance with the ASTM D790 standard and their physicochemical characteristics also were characterized. P(L)LA and P(L/DL)LA implants were equally resistant to local infection, their mechanical and physicochemical properties being unaffected by bacterial challenge. Hence, once an infection has become established, the release of bactericidal/bacteriostatic by-products during implant degradation does not appear to affect its natural course. The release of bactericidal/bacteriostatic degradation products at the implantation site is unlikely to affect the natural course of an established infection.

Animals↗
PubMed2000

An improved peel test method for measurement of adhesion to biomaterials.

Adhesion of tissues to biomaterials is desirable to prevent bacterial proliferation and for epithelial/transmucosal sealing of transcutaneous appliances, but can be counter-productive elsewhere, e.g. implants contacting tendons or maxillofacial subcutaneous tissue. It is therefore important to gauge adhesion strength of tissues to biomaterials before clinical use. Peel-testing is widely used for industrial product adhesion monitoring, but has rarely been applied biomedically. Here we describe peel-testing instrumentation designed for testing adherence of soft tissues to biomaterials. It offers the advantage that a 90 degrees angle between peel and substrate is maintained, simplifying determination of applied normal forces separating tissue layers from material surfaces. The device is portable and can be brought directly to the specimen removal site. This minimizes time delays between explantation and testing, maintaining the tissue/biomaterial interface in the freshest possible state closely approximating in vivo conditions, and so avoids measurement artifacts. So far, the instrument has been used to test adhesion of tape to a biomaterial surface (for determining the device's technical performance), assess strength of tissue adhesives, and measure adhesion of subcutaneous tissue to orthopaedic biomaterials. However, its versatility suggests additional applications for the peel-tester where adhesion of soft tissue to biomaterials is of interest.

Journal Article↗
PubMed1998

Biomechanical behaviour at the distal third of the femur: possible use of a medial metaphyseal plate.

The incidence of fractures in the distal femur is becoming more frequent and they are often associated to complex lesions with potential complications. Operative treatment is mandatory for elderly people and several methods of internal fixation with appropriate implants have been developed, generally approaching the lateral aspect of the femur. An alternative antero-medial access was proposed several years ago but the biomechanical aspects of its application must be debated. The aim of the present study is to establish if adverse biomechanical effects should be expected when the plate is affixed at the medial side of the femur metaphysis, by analysing the strain pattern of a human cadaver femur submitted to loads simulated in different experimental conditions. Application of load resulted, as expected, in tension in the lateral aspect and compression in the medial aspect of the femur diaphysis but it turned more and more toward the anterior aspect and the compression turned toward the posterior aspect when the levels measured changed from proximal to distal. The plate was next to the neutral axis and produced a moderate stress protection effect (approx. 70 per cent). No biomechanical disadvantages have been observed as a result of the plate being apposed at the medial aspect instead of the conventional lateral aspect of the distal femur.

Aged↗
PubMed1994

A retrospective analysis of plate contouring in the tibia using the conventional 4.5 (narrow) dynamic compression plate.

Plate contouring is an essential part of plate osteosynthesis. Its safety and technical ease is dependent on plate factors (material and design) and the complexity of the contouring. Our purpose was to determine the range of plate contouring; estimate the strain on the plate from the radius of curvature in the area of contouring; and determine whether shaped plates had a reduction in their load carrying capacity. A retrospective analysis of 500 radiographed tibias that had undergone osteosynthesis with the conventional dynamic compression plate was conducted to evaluate the radius of curvature and degree of bend in the plates, and to determine whether plates were bent at screw holes. Contouring of the plate to fit the bone was done by the surgeon at the time of application. Postoperative radiographs were evaluated. We found that (a) the shorter the length of plate contoured, the greater the strain; (b) plates were bent at screw holes, and these tended to be the areas of highest strain; (c) the range of plate strain was 0.6-16% (average 1.6%); and (d) plates were bent from 10 to 90 degrees (average 20 degrees).

Biophysical Phenomena↗
PubMed1994

[Clinical results with the limited contact DCP plate of titanium--a prospective study of 504 cases].

From the beginning of 1988 to July 1991, ten Swiss and German clinics undertook to document all cases of internal fixation using the titanium LC-DCP as part of a prospective multicenter study. The follow-up period was 14.2 months on average. The clinical results of 504 fixations were convincing. The follow-up rate was 72%. Of these, 95% healed without complication. The most frequent complication was delayed healing which occurred in 2.5% of cases. The infection rate was low (1.1%). A separate comparison of DCP fixations on the tibial shaft in 1984-1988 demonstrated the obvious biological compatibility of the new plate and shows that excellent results can be obtained using plate fixation.

Adult↗
PubMed1993

Healing of cancellous bone osteotomy in rabbits--Part I: Regulation of bone volume and the regional acceleratory phenomenon in normal bone.

We performed a simple, undisplaced, incomplete osteotomy of the distal medial condyle of mature New Zealand White rabbits and permitted healing without fixation for 4 weeks. During the recovery period, the rabbits received the bone label calcein in their drinking water. From ground stained and unstained sections, we determined histomorphometric parameters in five zones: osteotomy gap, juxtaosteotomy, lateral condyle, metaphysis, and diaphysis. At 4 weeks, newly formed cancellous bone had obliterated the osteotomy gap. Osteotomy also stimulated new bone formation in cancellous bone of the medial condyle around the osteotomy. At that site, we found a fivefold increase in new bone without a change in bone volume (BV). Stimulation of bone formation was not observed in cancellous bone of the lateral condyle that had not been operated on or in cortical bone of the metaphysis or diaphysis. The maintenance of BV, despite increased new bone formation in the osteotomized medial femoral condyle, was probably due to a local acceleration of bone remodeling.

Animals↗
PubMed1993

Healing of cancellous bone osteotomy in rabbits--Part II: Local reversal of arthritis-induced osteopenia after osteotomy.

With use of the intravital bone label calcein, we previously identified, by histomorphometry, greatly increased new bone formation and juxtaarticular osteopenia (a high turnover state) in carrageenan-induced experimental inflammatory arthritis of the knee in rabbits. In Part I of this paper, we showed that a large increase in new bone formation after a stable incomplete distal femoral condylar osteotomy of normal bone in the rabbit does not increase bone volume (BV) in normal tissue adjacent to the osteotomy (zone 1). In this study, we performed an osteotomy of bone made osteopenic by experimental inflammatory arthritis. After 4 weeks of healing, we examined new bone formation and BV in five zones around the osteotomy. In zone 0 (the osteotomy gap), new bone formation filled the gap to normal BV, as we found for the normal/osteotomy group. In zone 1 (adjacent to but excluding the osteotomy gap), we found greatly increased new bone formation and a return to normal BV, increased from the osteopenic level induced by experimental inflammatory arthritis. In this model, osteotomy apparently reversed the bone-wasting process of inflammatory arthritis. This effect was not observed in other zones: the lateral condyle that had not been operated on, the metaphysis, or the diaphysis.

Animals↗
PubMed1989

Changes in the metaphysis and diaphysis of the femur proximal to the knee in rabbits with experimentally induced inflammatory arthritis.

We quantified the cross-sectional cortical bone area and remodeling rates in the ipsilateral femoral diaphysis and metaphysis of rabbits with carrageenan-induced inflammatory monarthritis of the knee. Although osteogenesis rates were significantly elevated (approximately threefold in diaphyses and sixfold in metaphyses), the cross-sectional bone area of the diaphysis was significantly diminished. Fivefold and sixfold increases in bone resorption rates were calculated in diaphyses and metaphyses, respectively. Other morphologic changes observed were porosity and net resorption of the anterior cortex and net accretion on the posteromedial cortex ("drift" of bone). These findings may have clinical significance with regard to the mechanisms and consequences of bone changes in patients with rheumatoid arthritis.

Animals↗
PubMed1988

Juxtaarticular bone loss in experimental inflammatory arthritis.

The osteopenia associated with experimental inflammatory arthritis was studied by a histomorphometric method that exphasized net changes in bone composition. Juxtaarticular trabecular bone volume and turnover were studied in the carrageenan injection model of inflammatory arthritis of the mature rabbit knee. Trabecular bone volume was studied by histomorphometry of the femoral condyles and confirmed by photodensitometry on standard macroradiographs. Osteogenesis was studied by imaging of calcein fluorochrome-labeled newly formed bone in undecalcified histological sections. A significant net loss of cancellous bone (approximately 20%) occurred over 49 days in both the medial and the lateral femoral condyle in the arthritis group compared with normal controls. Total osteogenesis was increased fourfold and it was calculated that an even greater increase in total bone resorption was responsible for the negative bone balance. There is evidence that the periarticular bone loss of human rheumatoid arthritis is also associated with increased bone turnover. Quantitative studies of the kinetics of bone remodeling in inflammatory arthritis will provide the basis for therapeutic attempts to prevent or reverse arthritis-induced bone loss. Fracture risk in inflammatory arthritis may be increased not only by osteopenia, but additionally by the presence of a large proportion of newly formed (and presumably less mineralized) bone.

Animals↗
PubMed1976

[Microparticles in heart operations with extracorporal circulation (author's transl)].

Disturbances of the microcirculation during extracorporal circulation are not yet clearly understood. Many authors think that microembolism is reposible. In two groups of patients with different perfusion techniques we were looking for microparticles with a new constant pressure filtration method using the Agglometer r apparatus. During the by-pass no particles were found. Yet, we found particles in the priming when blood was used, in the suction blood and in special blood samples after contact with the pericardium. In these cases it was always possible to eliminate the particles with special filters. The particles in the suction blood seemed to originate from the extracardial blood portion coming from the pericardium. This portion seemed to be responsible for postoperative complications such as hemolysis and petechia. These complications could not be seen when extracardiac suction blood was eliminated or filtrated.

Adult↗
PubMedDate not supplied

A defect-in-continuity in the canine femur: and in-vivo experimental model for the study of bone graft incorporation.

The in-vivo study of bone graft incorporation has traditionally used a segmental diaphyseal bone defect. This model reliably produces a nonunion, but is complicated by graft instability and altered limb loading stresses. The authors discuss the advantages of a defect-in-continuity canine femur model which produces a more consistent union with fewer mechanical complications despite the absence of fixation. This proposed model permits analysis of radiographic, histologic and biomechanical data which are more applicable to the usual clinical setting in which bone graft is required.

Animals↗