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At least 1,135 records · Page 63Linked to original sources
PubMed2006

Comparison of fondaparinux, low molecular-weight heparin and unfractionated heparin in preventing thrombus formation on mechanical heart valves: results of an in-vitro study.

BACKGROUND AND AIM OF THE STUDY: The study aim was to investigate the efficacy of three different anticoagulants in preventing thrombus formation on mechanical heart valves, using an in-vitro system. METHODS: Blood samples (470 ml) were taken from young and healthy male volunteers and anticoagulated with unfractionated heparin (UFH; n=18), low molecular-weight heparin (LMWH; n=18) or fondaparinux (n=16). Bileaflet mechanical heart valves were placed in a new device--the 'Thrombosis Tester'--and exposed in a continuous circulation at a rate of 80 beats per min to the anticoagulated blood samples for a total exposure time of 60 min. Results for thrombus weight were skewed distributed and presented as log-transformed values. RESULTS: The weight of each valve was measured before and after 1 h of perfusion; subsequent mean (+/-SD) thrombus weights were 0.739 +/- 0.573 g for UFH, 0.789 +/- 0.099 g for LMWH, and 0.934 +/- 0.145 g for fondaparinux (p = 0.397 for comparison of all groups by ANOVA). Electron microscopy showed concordant results with regard to thrombus formation on heart valve surfaces. CONCLUSION: Fondaparinux and LMWH were as effective as UFH in preventing thrombus formation on mechanical heart valves in vitro. The 'Thrombosis Tester' proved to be a new, unique instrument for investigating the ability of anticoagulants to prevent valve thrombosis on mechanical heart valves under in-vitro conditions.

Anticoagulants↗
PubMed1988

Histopathologic evaluation in failed Gerard double cup arthroplasty.

Fifteen femoral head remnants were removed at revision of an uncemented double cup arthroplasty and were investigated by histological methods. Nine showed resorption of the head, partly due to osteoporosis by stress protection, preexistent pseudocysts, or osteonecrosis. Necrosis was frequently seen in the apicocranial area, and in six cases extended into deeper areas. One failure was attributed to synovitis caused by polyethylene debris. A smooth collagenous membrane developed at both the femoral head and the acetabular interfaces. In some cases metaplasia into cartilage and osteophytes developed at the cup rim.

Adult↗
PubMed1988

Preparation of the proximal femur in cementless total hip revision.

With an increased incidence of revision for the failed cemented total hip arthroplasty, techniques of revision surgery need meticulous attention to detail. Although the causes of the failed cemented total hip arthroplasty are many, they tend to follow characteristic patterns. The proximal femur can be exposed through an extensive muscle split incision, which offers a complete circumferential view of the femur. The cement removal is enhanced by controlled perforation using high-speed drills. Classification of bony deficits of the proximal femur can be divided into Type I, including intact cortex and medullary content; Type II, in which there is intact cortex but deficient medullary content; and Type III, in which deficits of both the cortex and medullary canal are present. Prosthetic selection is based on residual bone stock. In general, cementless fixation is advocated, with distal fixation using long-stem devices. Augmentation of bone deficits requires the use of segmental prosthetic replacement or fresh-frozen allografts. One hundred sixty patients were followed for two to six years. Satisfactory results have occurred in over 90% of the patients; better results are anticipated in patients with minimal bone deficits. Aseptic loosening requiring rerevision has occurred in 5% of the patient population. Understanding the dynamics of failure and the residual bone deficits allows one to manage the failed cemented total hip arthroplasty with greater efficiency and predictability.

Bone Cements↗
PubMed1996

Immunoglobulins and complement deposits in mitroflow pericardial bioprosthetic heart valves--a contributing factor to structural deterioration.

BACKGROUND AND AIMS OF THE STUDY: Twenty-two bovine pericardial Mitroflow prostheses were explanted after 73-114 months from either the aortic or mitral position because of clinical failure. All the samples exhibited cuspal tears and foldings. Eleven prostheses were calcified. The aim was to study biological factors involved in the structural deterioration. METHODS: Histologic and biochemical assays were carried out on the deteriorated, non-calcified and on the calcified leaflets. Labelled antibodies and avidinbiotinyilated peroxydase complex were used to detect plasma proteins and cells in the cusps. RESULTS: Fibrin covered the cuspal surface and accumulated in the deep disrupted layers (19/22). Scattered fibronectin filaments were seen across the transversal sections (20/22). IgG, complement fractions C1q, C3, C4 (20/22), macrophages (sixteen) and cells containing granulocyte elastase were revealed in the altered matrix. These plasma proteins and cells were detected in the disintegrated matrix of non-calcified and of calcified leaflets. IgA was present in amorphous cuspal thickenings with lipid infiltration (12/22). Western blot analysis of the PBS-2% SDS extracts from the leaflets indicated the breakdown of fibrinogen/fibrin, fibronectin and of complement proteins C3, C4 and C5. CONCLUSIONS: The results suggest the activation of the complement by the non-hemocompatible, chemically processed bovine pericardium. The bioactive peptides generated in this process can stimulate monocyte migration, phagocytosis and exocytosis of proteases able to degrade the glutaraldehyde cross-linked macromolecular matrix. These biological factors can contribute, together with the mechanical stress, to the structural deterioration of the bioprosthesis.

Aged↗
PubMed1994

Late complications after total hip replacement in renal allograft recipients.

Seventy nine hips in 53 recipients of renal allografts were treated by cemented total hip replacement for avascular necrosis of the femoral head between 1972 and 1992. Eight hips in 6 patients required revision for aseptic loosening after a mean of 11.2 years. Three replacements in 3 patients became infected with salmonella enteritidis after a mean of 6.2 years. One was revised, one had a disarticulation of the hip, and the third was treated with long term antibiotics. Survivorship analysis for total hip replacement and the renal allografts showed a hip reoperation rate of 9.9% at 10 years and 54.6% at 15 years with mortality rates of 32.2% and 42.2% respectively. Thus patients surviving 15 years are at a higher risk of failure of the prostheses than of dying.

Adult↗
PubMed2006

Current etiologies and modes of failure in total knee arthroplasty revision.

UNLABELLED: Although total knee arthroplasty is a very effective intervention and increasing in prevalence, failures do occur. We studied patients presenting for total knee arthroplasty revision to determine any modifiable causes of failure, both short and long term, and where future efforts should be directed to reduce the incidence of failure. A multicenter prospective observational cohort study of 318 consecutive patients, with minimum 1 year follow-up, undergoing total knee arthroplasty revision was performed. Associations between modes of failure were also assessed. The mean time from primary procedure to total knee arthroplasty revision was 7.9 years. Many patients (64.4%) had more than one cause of failure. Thirty-one percent of patients were early (< 2 years) failures at a mean of 11 months. These had a higher prevalence of infection, perioperative factors and comorbidities. Late failures occurred at a mean of 119.2 months. Other major causes of failure included instability (28.9%), wear (24.5%) and component loosening suggesting the importance of modifications in technique, implants and other areas. Application of these findings will ultimately reduce revision numbers through continued refinement of total knee arthroplasty practice and through further specific investigation of these modes of failure. LEVEL OF EVIDENCE: Therapeutic study, level II-2 (prospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Adult↗
PubMed2006

Lessons learned from early clinical experience and results of 300 ASR hip resurfacing implantations.

Between August 2003 and April 2005, 300 ASR metal-on-metal resurfacing hip endoprostheses were implanted by the first author and a fellow surgeon. The mean age at surgery was 56.8 years (18-75.9 years) and mean body mass index was 27.6 kg/m2 (range, 19-41 kg/m2). The mean follow-up time was 202 days. The mean Harris hip score improved from 44 pre-operatively to 89 at 3 months post-operatively. In total, eight (2.7 per cent) cases [five neck fractures (1.66 per cent) and three cup revisions (1 per cent)] were revised. Two neck fractures occurred within a group of seven cases of femoral neck notching detected postoperatively; one neck fracture occurred out of two cases of incomplete seating of the femoral implant. A significantly higher (p < 0.001) failure rate was observed for patients who had undergone a previous osteosynthesis of the proximal femur (three revisions in a group of 15 patients). Revision cases had a significantly greater body mass index (p = 0.031). A learning curve was evident from the reduction in revisions from 5 in the first 100 surgical procedures to 2 in the next 100 and 1 in the last 100. These results show the importance of accurate surgical technique and careful patient selection for fourth-generation hip resurfacing implants,

Adolescent↗
PubMed1982

Ten-year follow-up of Müller hip replacements.

During 1969-72 138 total hip replacements were performed according to the technique of Müller. The mean age of the patients at operation was 65.4 years. The results were analysed 9-12 years after the operation. Deep infection occurred in two cases necessitating removal of the prosthesis. Eighteen per cent (25/138) were reoperated on because of mechanical failure, the prosthesis was exchanged in 20 of them. Radiological signs of loosening of either component were found in a further 17 patients; only two had symptoms. The total loosening rate was thus 33 per cent (42/138). Twenty-six patients with 31 operated hips died during the observation period. In all of these the aim of the operation was achieved. The remaining cases were evaluated for the long-term results of total hip replacement. These were found to be satisfactory in all of but two cases with symptoms of mechanical failure. Loosening of the femoral stem was associated with varus position, while no relationship was found between loosening of the acetabular cup and the degree of inclination.

Adult↗
PubMed2004

[Heart transplantation and assist devices].

BACKGROUND: Although drug therapy of patients with chronic heart failure has improved significantly over the years, mortality still remains high. At present, heart transplantation is the gold standard therapy for patients with end stage heart disease. Due to the limited number of organs, a growing number of patients require the implantation of mechanical assist devices. HEART TRANSPLANTATION: Because of the excellent long-term survival after cardiac transplantation, current studies focus on long-term complications. The aim of these studies is the establishment of an immunosuppressive strategy that effectively prevents cardiac allograft vasculopathy in combination with a low incidence of negative side effects. Furthermore, quality of life is a major focus of current interest. ASSIST DEVICES: Assist device implantation has changed from an experimental to a routine procedure in several centers. Still, many problems have to be solved. Especially because of recurrent infections the long-time use of assist devices is limited. For final judgment, results of current studies have to be awaited.

Clinical Trials as Topic↗
PubMed1997

The theory of early loosening of hip prostheses.

The issue of prosthetic loosening is currently a matter of debate, particularly with regard to the timing and nature of the precipitating events. The theory presented here postulates that loosening begins at an early stage due to either insufficient initial fixation or early loss of fixation. The loosened prosthetic component is then affected by varying degrees of mechanical stress associated with normal daily activity, which differs according to patient characteristics (body weight and level of physical activity) and the components used (prosthetic design, positioning, friction, and wear). This theory of early loosening can explain without supplementary ad hoc assumptions the rapid early prosthetic migration detected by roentgen stereophotogrammetry, the development of focal osteolysis and wear granulomas, the phenomenon known as stress-shielding, and, to a great extent, the epidemiology of clinical failure.

Bone Resorption↗
PubMed1994

Early migration and late aseptic failure of proximal femoral prostheses.

The vertical migration of four configurations of a proximal femoral prosthesis, followed for up to nine years, was measured on standard radiographs. The same implant was used without cement (group 1) and with cement (group 2). The migration of both groups was linear from six months onwards. The mean migration rate and the incidence of late aseptic loosening were both greater in group 1. Survival analysis of the two groups, however, showed no statistically significant difference. In both groups, hips later destined for revision migrated more rapidly from the initial postoperative period onwards, than did the remainder. A threshold migration of 1.2 mm/year during the first two years after implantation detected hips likely to fail with a specificity of 86% and a sensitivity of 78%. This 'migration test' was applied to the results in two further groups of patients in which a modified femoral prosthesis had been implanted without hydroxyapatite coating (group 3) and with hydroxyapatite coating (group 4). The test distinguished between the four groups and suggested that at least two fixation procedures should be abandoned. We conclude that vertical migration measured on standard radiographs in the first two years after implantation can be used to predict late aseptic loosening. New prosthetic configurations should be evaluated by migration measurements before their general release. Our observations support the view that one cause of late aseptic loosening is imperfect initial fixation.

Adult↗
PubMed1998

Sloppy hinge prosthetic elbow replacement for post-traumatic ankylosis or instability.

From 1984 to 1995, 68 ankylosed elbows and 11 which were unstable after trauma were replaced in India by Baksi sloppy hinge prostheses. The mean age of the patients was 28.6 years (17 to 70) and the mean follow-up 9.6 years (2 to 13.5). Of the 68 ankylosed elbows, 59 (87%) regained a mean arc of painless movement of 88.5 degrees (27 to 115). The mean improvement of supination was 24 degrees and of pronation 16.5 degrees . There were 54 good results (80%), eight fair and three poor. There were two complete failures due to infection, and one due to a broken humeral stem. Of the 11 unstable elbows, the nine with good results had a mean arc of 125 degrees (15 to 140) of painless stable movement, with a mean improvement in supination of 26 degrees and of pronation of 19.5 degrees . There was one fair result and one failure due to loosening with subsequent late infection. There were significant complications in 14 cases with infection in seven and aseptic loosening in four. Patients with loosening or late removal of the prosthesis often retained reasonably stable elbow movement because periprosthetic fibrosis had connected the approximated bone ends, and muscle balance had been restored.

Adolescent↗
PubMed2004

Immune reactions associated with silicone-based ventriculo-peritoneal shunt malfunctions in children.

The implantation of ventriculo-peritoneal (VP) shunting systems is the most commonly performed neurological procedure in children with hydrocephalus. Although the overall complication risk is low, the cumulative risk of shunt failure is high and unfortunately results in a high prevalence of revision surgeries. In this study, we explored the concept that some pediatric patients may develop an immune response to either the proteins attached to the silicone implant surface or to the biomaterial itself, and that this reaction may contribute to VP shunt failure in some individuals. The data displays that the sterile shunt malfunction group had a higher rate of protein deposition and increased levels of autoantibodies to the extracted surface proteins as compared to individuals with functioning shunting systems. The precise nature of the shunt-bound proteins that serve as antigens in this experiment have not yet been determined. The data also indicated that some individuals develop antibodies to polymeric substances that cross-react with partially polymerized acrylamide. The detection of significant amounts of shunt-bound protein, antibody responses to these proteins and to polymeric substances suggest that an immunological response to these proteins may play a role in the mechanism behind sterile shunt malfunctions.

Adolescent↗