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At least 1,693 records · Page 94Linked to original sources
PubMed1979

Arthrodesis of the knee following failed total knee arthroplasty.

In forty-five patients, who had an arthrodesis because of failed total knee arthroplasty, the cause was infection in forty, instability in two, failure of the prosthesis in two, and loosening in one. The arthrodesis succeeded in twenty-nine (81%) of thirty-six patients who had had a minimally or partially constrained arthroplasty and in five (56%) of nine who had had a hinge-type prosthesis inserted. The reasons for failure were severe bone loss, persistent sepsis, and loss of bone apposition after manipulation. The technique of arthrodesis did not seem to influence the final result. External fixation most commonly had to be used because of the infections and the device was kept in place for an average of ten weeks, after which immobilization in a cast was used until the arthrodesis healed.

Adult↗
PubMed1990

Patients' observations of bioprosthetic valve failure: "my heart is honking, doctor".

Audible cardiac murmurs are uncommon and may indicate severe native valve dysfunction. In six patients with bioprosthetic mitral valves audible honking systolic murmurs suddenly developed. Doppler echocardiography showed characteristic striated regurgitant signals. At operation each prosthesis had torn cusps. New audible murmurs and striated Doppler signals originating from mitral bioprosthetic valves are indicators of cusp tears. Recognition of this is important because early detection of prosthetic valve dysfunction may improve subsequent surgical outcome.

Aged↗
PubMed2000

[Artificial urinary sphincter].

OBJECTIVE: To review the literature on artificial urinary sphincters, to describe their function, technique of implantation, indications, results and complications, and to analyze the possible utility of the prosthesis in the treatment of stress incontinence. METHODS: Medline (Index Medicus Online) and Embase (Excerpta Medica Online) were accessed to review the literature on artificial urinary sphincters published from 1974 (when the first artificial urinary sphincter was described by Foley) to October 1999. Of 322 articles identified, only those that described the patient selection criteria, type of prosthesis utilized, results and complications, and mean follow-up were considered. Articles describing historical aspects and new prototypes were also reviewed. Papers by the authors of the present article were excluded to avoid the bias of author preference. The bias of the language barrier, which occurs when articles published in Spanish, English and French are reviewed, was minimum. RESULTS: The AMS-800 is the only model available today. The results achieved are excellent if the indication is correct and perioperative management is careful and exact. The ideal candidate is one with genuine stress urinary incontinence and normal bladder function, although hyper or hyporeflexia is not an absolute contraindication if corrected before, during or after insertion of the prosthesis. The surgical technique is relatively simple and the only difficulty consists in the choice of the appropriate cuff and reservoir. The complications include urethral atrophy, erosion, infection and bladder instability, and are less frequent in women with stress urinary incontinence type III and in men incontinent after prostate surgery, and more frequent in patients with incontinence following pelvic trauma, incontinence due to congenital malformation and those with a neurogenic bladder. The mechanical failures of the prosthesis have diminished with its improved design. New hydraulic and non-hydraulic prototypes have been designed to reduce the complications, but the results are as yet unavailable. CONCLUSIONS: Today, patients with stress urinary incontinence have more possibilities to recover continence. If incontinence persists after all the available medical and surgical options have been attempted, one possibility still remains: the artificial urinary sphincter.

Female↗
PubMed1992

Applications of crude incidence curves.

Crude incidence curves display the cumulative number of failures of interest as a function of time. With competing causes of failure, they are distinct from cause-specific incidence curves that treat secondary types of failures as censored observations. After briefly reviewing their definition and estimation, we present five applications of crude incidence curves to show their utility in a broad range of studies. In some of these applications it is helpful to model survival-time distributions with use of two different time metameters, for example, time from diagnosis and age of the patient. We describe how one can incorporate published vital statistics into the models when secondary types of failure correspond to common causes of death.

Antineoplastic Agents↗
PubMed2005

[Effects of magnetic resonance tomography on upper eyelid implants].

BACKGROUND: For the therapy of lagophthalmos in facial palsy, gold (99.99%), platinum (99.95%) and platinum/iridium (97%/3%) alloy weights are implanted into the upper eyelid. Investigations on the MRI compatibility of the different eyelid implants with 1.5 and 3.0 Tesla-MRT-systems, which are often used for the diagnosis of head and neck tumours, are still missing. METHODS: Three different eyelid implants made of pure gold, pure platinum and a platinum/iridium alloy were tested in vitro. As parameters, temperature changes, movements of the implants and picture artefacts of the different implants were determined using a 1.5 and 3.0 Tesla MR system. The deflection forces of the implants were evaluated by thread test, lying in a Petri dish and floating in a water bath. RESULTS: No rise in temperature was recorded in any implant. On the water surface, all three implants changed their positions and floated towards the magnetic field. The velocity of the implants increased in the 3.0 Tesla system. Increasing the frictional resistance by lying the implants in a Petri dish, there was no movement in the 1.5 or 3.0 Tesla systems. In addition, no movement of the implants could be observed in the thread test. All implants made few artefacts, with gold showing the least artefacts. CONCLUSION: MR imaging at 1.5 or 3.0 Tesla may be performed safely for warming up or dislocation of the implant in patients with eyelid implants made of pure gold, pure platinum or a platinum/iridium alloy.

Artifacts↗
PubMed2006

Behavior of metal implants used in ENT surgery in 7 Tesla magnetic resonance imaging.

Magnetic resonance imaging (MRI) has become increasingly important as an imaging technique in cross-sectional imaging of head and neck diseases. To investigate whether MRI examinations can be performed without risk in patients with metal implants even at higher field strengths, we examined different materials in 7 Tesla MRI. Implants near sensory organs like the middle ear or eye are of particular interest here. Using the 7 Tesla research MRI for small animals, we tested implants made of various metals like titanium, gold, gold/platinum, platinum/iridium, gold-plated silver, PTFE and stainless steel for heating, translocation and rotation according to a standardized protocol. A fiber optic temperature probe measured the heating of the implant before, during and after MRI scanning. None of the implants showed significant heating. The gold-plated stainless steel ventilation tube was the only implant to markedly change its position already in the Petri dish. Of the remaining implants, a trachea support ring, a nose dilatator and the wire from the ventilation tubes moved during vibration of the Petri dish. With exception of two implants, all implants changed positions in the water bath. In the swim test, the gold implants showed the least movement of all the implants. In this study, the properties of the non-ferromagnetic implant materials differed in the 7 Tesla MRI. Stainless steel ventilation tubes, the trachea support ring and the nose dilatator were not suited for the 7 Tesla MRI system, because they changed their position during MRI. In the case of ventilation tubes with a steel wire, the wire should be removed before MRI to prevent injury to the external auditory canal. There was a tendency for the pure gold implants to move less in the 7 Tesla MRI than all other tested materials. General statements cannot be made about the MRI suitability of different implants. Every implant should be individually examined to confirm its definitive MRI compatibility. Particularly, middle ear implants warrant special attention here due to their closeness to the oval window.

Equipment Failure Analysis↗
PubMed1992

Early structural deterioration with the mitroflow pericardial xenograft in the mitral position.

Early structural deterioration with the mitral Mitroflow pericardial valve requiring reoperation occurred in 6 patients. Clinical diagnosis of prosthetic failure was made 5 to 58 months after valve implantation (mean, 38 months). Re-replacement was carried out 22 to 80 months (mean, 55 months) after the initial operation. Mode of failures were cuspal tear without calcification in three valves and massive calcifications in the remaining bioprostheses. High incidence of early structural deterioration of the Mitroflow pericardial valve makes this new prosthesis an unsatisfactory alternative as a substitute in the mitral position.

Adult↗
PubMed2006

Late mitral annuloplasty failure: the loss of the ring.

An 81-year-old man complained with increasing dyspnoea and asthenia few months after a successful double mitral and tricuspid valvuloplasty intervention. The echocardiogram revealed a partial detachment of the mitral annuloplasty ring due to dehiscence determining a severe regurgitation. Curiously, at Color-Doppler analysis of mitral inflow, the prolapse of the detached ring produced a fascinating circular line inside the regurgitation signal, mimicking the shape of a gemstone ring. We described a case of a relatively uncommon cause of late mitral valvuloplasty failure characterized by a really unusual echocardiographic finding.

Aged, 80 and over↗
PubMed2005

Molecular chain stretch is a multiaxial failure criterion for conventional and highly crosslinked UHMWPE.

The development of accurate theoretical failure, fatigue, and wear models for ultra-high molecular weight polyethylene (UHMWPE) is an important step towards better understanding the micromechanisms of the surface damage that occur in load bearing orthopaedic components and improving the lifetime of joint arthoplasties. Previous attempts to analytically predict the clinically observed damage, wear, and fatigue failure modes have met with limited success due to the complicated interaction between microstructural deformations and continuum level stresses. In this work, we examined monotonic uniaxial and multiaxial loading to failure of UHMWPE using eight failure criteria (maximum principal stress, Mises stress, Tresca stress, hydrostatic stress, Coulomb stress, maximum principal strain, Mises strain, and chain stretch). The quality of the predictions of the different models was assessed by comparing uniaxial tension and small punch test data at different rates with the failure model predictions. The experimental data were obtained for two conventional (unirradiated and gamma radiation sterilized in nitrogen) and two highly crosslinked (150kGy, remelted and annealed) UHMWPE materials. Of the different failures models examined, the chain stretch failure model was found to capture uniaxial and multiaxial failure data most accurately for all of the UHMWPE materials. In addition, the chain stretch failure criterion can readily be calculated for contemporary UHMWPE materials based on available uniaxial tension data. These results lay the foundation for future developments of damage and wear models capable of predicting multiaxial failure under cyclic loading conditions.

Arthroplasty, Replacement↗
PubMed2004

Tissue engineering auricular reconstruction: in vitro and in vivo studies.

Although investigators have demonstrated that neocartilage can be constituted in a predetermined shape and in complex three-dimensional structures, such as a human ear, by using cell transplantation on polymer constructs, many unsolved problems still remain. The crucial issues for auricular tissue engineering consisted of optimal cell culture environment, choice of polymers, behavior of chondrocytes, study of cell-polymer constructs in an acceptable animal model, and long-term structural integrity. Here we describe our tissue engineering approaches for auricular reconstruction including auricular scaffold fabrication, in vitro chondrogenesis, in vivo immunocompromized xenograft and immunocompetent autologous animal models, and long-term follow-up. Though many current obstacles regarding auricular tissue engineering still exist, we demonstrate techniques of auricular scaffold fabrication with promising in vitro and in vivo neocartilage formation, optimal selection and application of animal models, and, to the best of our knowledge, the first report of different biodegradable biomaterial trials and the longest in vivo results (10 months) for auricular tissue engineering.

Animals↗
PubMed2003

Finite element analysis of the initial stability of ankle arthrodesis with internal fixation: flat cut versus intact joint contours.

OBJECTIVE: Qualitative comparison of the initial stability provided by two joint preparation techniques and various screw configurations in ankle arthrodesis, using the finite element method.Design. A three-dimensional model of a healthy ankle was developed from computed tomography images. Two groups of models were built, one with the joint contours resected to produce flat surfaces, and the second with the joint contours preserved. In each case, a variety of screw orientations were examined. BACKGROUND: Despite the improved results of ankle arthrodesis, failure rates due to non-union are still reported. The initial stability of the arthrodesis construct seems important in the final outcome of the fusion. METHODS: Non-linear contact finite element analyses were performed in the arthrodesis constructs subjected to internal/external torsion and dorsiflexion. Micromotions at the bone-to-bone interface were calculated for frictionless and Coulomb friction contact, and compared for the two joint preparation techniques and screw configurations. RESULTS: Overall lower peak micromotions were predicted when preserving the joint contours both in torsion and dorsiflexion. For both preparation techniques, the lowest micromotions tended to occur with the screws inserted at 30 degrees with respect to the long axis of the tibia, crossing above the fusion site. Inclusion of friction in the models caused a general decrease on the magnitude of the micromotions as compared to the frictionless case, but did not affect the ranking of the models. CONCLUSIONS: The finite element method can be used as a qualitative tool to study the initial stability of ankle arthrodesis, overcoming the difficulties of measuring bone-to-bone interface micromotions experimentally. Better initial stability was predicted for ankle arthrodesis when the joint contours were preserved rather than resected. Crossing the screws above the fusion site at a steeper angle also tended to increase the stability at the fusion site. RELEVANCE: Finite element analyses can help during the pre-operative planning of ankle arthrodesis. When bone density is not compromised, preserving the joint contour and inserting the screws at less than 45 degrees to the long axis of the tibia, crossing over the arthrodesis site, may offer better initial stability.

Ankle Joint↗
PubMed2003

Dissemination of metals from a failed patellar component made of titanium-base alloy.

Complications related to the patella are the most common problems in total knee arthroplasty and major reasons for revision surgery. Among patellofemoral problems, metal-to-metal contact between patellar and femoral components is the worst. We measured levels of titanium, aluminum, and vanadium in serum and urine samples and compared these measures from cases in which metal-to-metal contact of the patellar component occurred with those in cases in which only polyethylene wear occurred. Serum levels of the metals in cases with metal-to-metal contact were over 10 times higher than those in cases without metal-to-metal contact. This suggests that different ranges of serum metal ion levels could eventually be correlated with a variety of mechanisms of patellar failure. Therefore, cases with metal-to-metal contact should be distinguished from cases without metal-to-metal contact. These should not be considered as a single group in patellar component failure.

Alloys↗
PubMed1999

Edge loading of patellar components after total knee arthroplasty.

Patellofemoral joint kinematics, contact areas, contact pressures, and contact patterns were assessed after total knee arthroplasty (TKA) using human cadaver knees. Two contemporary TKA systems with anatomic patellofemoral joints were implanted and tested under anatomically based loading conditions. An electromagnetic tracking system was used to evaluate patellofemoral kinematics, and Fuji pressure-sensitive film was used to determine contact areas, pressures, and patterns. Edge loading of patellar components was observed at higher knee flexion angles with both TKA systems. Peak contact pressures seen at the regions of edge loading exceeded the yield strength of ultra-high-molecular weight polyethylene. Efforts to reduce edge loading and contact pressures may decrease the incidence of patellofemoral joint complications and component failure after TKA.

Arthroplasty, Replacement, Knee↗