Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Prosthesis Failure”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48Linked to original sources
PubMed2005

A hip wear simulator with 100 test stations.

A novel high-capacity hip wear simulator of the pin-on-disc type was designed, built, and validated. This so-called Super-CTPOD (circularly translating pin-on-disc) device has as many as 100 separate test stations, being an advanced version of the previously validated 12-station CTPOD. A validity test was done so that in all stations the specimens and the test conditions were as similar as possible. Hence, for the first time in this field, an adequate number of similar tests was done for a proper statistical analysis of wear data. The pins were conventional, gamma-sterilized ultra-high molecular weight polyethylene, and the discs were polished CoCr. The lubricant was diluted calf serum and the test length 3 million cycles. In the course of the test, the pins became highly polished, whereas the discs remained practically unchanged. The majority of the polyethylene wear particles were rounded, with a mean diameter of 0.25 microm. The 100 wear factor values computed from the 100 steady state wear rate values of the pins were normally distributed, the mean +/- 95 per cent confidence interval being 1.63 +/- 0.017 x 10(-6) mm3 /N m. The standard deviation was 5.4 per cent of the mean. There were no outliers. The wear mechanisms and the wear factor agreed well with clinical findings. Altogether, the Super-CTPOD test system was shown to be a unique combination of validity, low variation, capacity, efficiency, reliability, productivity, economy, ease of operation, and compact size.

Equipment Design↗
PubMed2005

Precision and accuracy in ceramic-on-ceramic wear analyses: influence of simulator test duration.

In this, the first report of precision and accuracy in simulator studies, ceramic-ceramic implants with ultra-low wear trends represented a relevant wear model. The effect of test durations was examined in a standard simulator test mode on the quality of the linear regression trends, the average wear estimates, and the amount of noise in the data. Three sets of diametral tolerances were compared in 28 mm diameter alumina implants. The authors' hypothesis was that wear data would be significantly improved with increased test durations. The average wear rates varied little with test duration, the biggest change amounting to only 30 and 15 per cent decreases in the wear estimate by 10 and 14 million cycles respectively. The most satisfactory improvement in the study was the decrease in variance (noise) with increasing duration, +/- 200 per cent at 5 million cycles reduced to +/- 55 per cent at 14 million cycles. The quality of the linear regression coefficients improved 150 per cent by 10 million cycles and 250 per cent by 14 million cycles. Overall the ceramic implants with highest diametral tolerances showed the least wear (15 per cent less, but not statistically significant). However, given such low wear rates for alumina liners, it was unlikely that any differences owing to diametral tolerances would be clinically significant in the typical patient.

Ceramics↗
PubMed1990

Clinical comparative study between mitral mechanical and bioprosthetic valves--what is the benefit of bioprosthetic valves in the mitral position?

Comparative long-term performance characteristics of mechanical valves and bioprosthetic valves were analyzed retrospectively for patients who had undergone isolated mitral valve replacement from 1967 to 1988. Two hundred ninety-one patients received either mechanical (n = 97) or bioprosthetic (n = 194) valves. The cumulative follow-up was 1,609 patient-years (mean 6.3 +/- 3.8 years, ranging from 0.6 to 20.2 years, 98.9% complete follow-up). The actuarial survival rate, including hospital deaths, at 10 years was 72 +/- 12% for mechanical and 74 +/- 4% for bioprosthetic valve recipients. The rates of freedom from thromboembolism, structural valve failure, prosthetic valve endocarditis, prosthetic valve endocarditis, reoperation, and overall valve-related complications at 10 years were 87 +/- 5%, 100%, 91 +/- 3%, 100%, and 79 +/- 8% for mechanical valve recipients and 85 +/- 3%, 77 +/- 5% (p less than 0.001), 85 +/- 13%, 71 +/- 5% (p less than 0.001), and 52 +/- 5% (p less than 0.001) for bioprosthetic valve recipients, respectively. Thromboembolism occurred at a similar incidence in two types of valves (2.0 +/- 0.7 vs. 2.2 +/- 0.4%/pt-yr). Structural valve failure, reoperations, and overall valve-related events occurred more frequently in the bioprostheses recipients (0 vs. 2.0 +/- 0.4%/pt-yr; p less than 0.001, 0.3 +/- 0.3 vs. 2.9 +/- 0.5%/pt-yr; p less than 0.001, 2.5 +/- 0.8 vs. 5.6 +/- 0.7%/pt-yr; p less than 0.005, respectively). There was no mortality at the time of redo-operation. These results show that bioprostheses in the mitral position exhibit small benefits of antithrombogenesis and prominent disadvantage of poor durability requiring reoperation.

Bioprosthesis↗
PubMed2000

Wear debris from two different alumina-on-alumina total hip arthroplasties.

We compared wear particles from two different designs of total hip arthroplasty with polycrystalline alumina-ceramic bearings of different production periods (group 1, before ISO 6474: group 2, according to ISO 6474). The neocapsules and interfacial connective tissue membranes were retrieved after mean implantation times of 131 months and 38 months, respectively. Specimen blocks were freed from embedding media, either methylmethacrylate or paraffin and digested in concentrated nitric acid. Particles were then counted and their sizes and composition determined by SEM and energy-dispersive x-ray analysis (EDXA). The mean numbers and sizes of most alumina wear particles did not differ for both production periods, but the larger sizes of particle in group 1 point to more severe surface destruction. The increased metal wear in group 2 was apparently due to alumina-induced abrasion of the stems. In this study the concentrations of particles in the periprosthetic tissues were 2 to 22 times lower than those observed previously with polyethylene and alumina/polyethylene wear couples.

Adult↗
PubMed2002

[Fracture analysis of a ceramic liner. Is in hip endoprosthesis replacement of ceramic on ceramic components with only one of the corresponding partners justified?].

The good biomechanical and tribological properties, together with the excellent biocompatibility, of ceramic-on-ceramic components, make them a preferential choice for total hip replacement surgery, at least in Europe. We report on a man admitted as an outpatient with painless grating in the hip one year after replacement of a ceramic femoral head, but not of the ceramic inlay. Clinical and radiological findings were indicative of a broken liner. This was confirmed during revision surgery, during which it was replaced by a polyethylene inlay; although the ceramic head appeared intact, it was replaced by a metal head. Inspection of the surface of the broken liner in the scanning electron microscope (SEM) revealed signs of material failure. We recommend careful inspection of ceramic-on-ceramic articulating components during total hip revision surgery and if there is any uncertainty, replacement of both so as to avoid premature failure.

Aged↗
PubMed2003

Primary stability of threaded cups in THR--an experimental study.

Four threaded cups were tested up to their lever-out moments, torque-in moments and their resistance to failure. A was a parabolic-shaped, B was a spherical, C was a spherical-shaped too, and D was a conical shaped cup. Cup A and D represent cups which have proven themselves in clinical applications, but not cup B. The threads were determined and showed different constructive features. The cups were torqued into precise cavities in PVC foam cubes, after that they were levered out in a testing machine. The lever-out moments of all the cups showed significant differences; the results were: A: 78.4 Nm, B: 88.7 Nm, C: 117.5 Nm, D; 136.6 Nm. In the case of the torque-in moments there were no significant differences between A and B, neither between C and D. The differences in stiffness between B and C were not significant, but they were between the others. The primary stability against lever-out and the torque-in moment of threaded cups for artificial hip replacement can be basically influenced by different constructive features. Hence lever-out moment and torque-in moment should be understood and tested as independent variables.

Arthroplasty, Replacement, Hip↗
PubMedDate not supplied

[Retrieval and failure analysis of surgical implants in Brazil: the need for proper regulation].

This paper summarizes several cases of metallurgical failure analysis of surgical implants conducted at the Laboratory of Failure Analysis, Instituto de Pesquisas Tecnológicas (IPT), in Brazil. Failures with two stainless steel femoral compression plates, one stainless steel femoral nail plate, one Ti-6Al-4V alloy maxillary reconstruction plate, and five Nitinol wires were investigated. The results showed that the implants were not in accordance with ISO standards and presented evidence of corrosion-assisted fracture. Furthermore, some of the implants presented manufacturing/processing defects which also contributed to their premature failure. Implantation of materials that are not biocompatible may cause several types of adverse effects in the human body and lead to premature implant failure. A review of prevailing health legislation is needed in Brazil, along with the adoption of regulatory mechanisms to assure the quality of surgical implants on the market, providing for compulsory procedures in the reporting and investigation of surgical implants which have failed in service.

Biocompatible Materials↗
PubMed2003

Accuracy of measurement of polyethylene wear with use of radiographs of total hip replacements.

BACKGROUND: Although a number of methods are used to estimate polyethylene liner wear from radiographs of total hip replacements, there is no consensus with regard to the accuracy of these methods. The purpose of this study was to compare the accuracy of several such measurement methods with use of both laboratory radiographs and routine clinical radiographs. METHODS: A phantom apparatus was designed to simulate random values of three-dimensional wear, with varying degrees of cup abduction and anteversion, and to obtain anteroposterior and cross-table lateral radiographs with each value. Wear was measured with use of the Charnley duoradiographic method, the Livermore method, and the method described by Dorr and Wan, as well as with use of PolyWare and Hip32 software packages, both with and without three-dimensional measurements. Clinical wear was measured from conventional radiographs made prior to revision surgery in fourteen patients and was compared with wear measured directly from the retrieved liners with use of a coordinate measuring machine. RESULTS: With laboratory radiographs, median errors were 0.1 mm with the Livermore method and both computerized methods, 0.23 mm with the Charnley method, and 1.7 mm with the method of Dorr and Wan. Maximum errors were between 0.6 mm (Livermore) and 4.3 mm (Dorr and Wan). In contrast, with use of clinical radiographs, median errors ranged between 0.2 mm (Hip32) and 0.6 mm (Dorr and Wan). Maximum errors ranged between 1.8 mm (Dorr and Wan) and 2.5 mm (Livermore). CONCLUSIONS: With laboratory radiographs, computerized methods of polyethylene wear measurement offered distinctly greater accuracy than did manual methods; however, with clinical radiographs, they offered only slightly better accuracy. Although the increased accuracy of computerized methods may be necessary in research settings, manual methods provided sufficient accuracy for routine clinical assessment of wear.

Arthroplasty, Replacement, Hip↗
PubMed2003

Measurement of polyethylene wear in total hip arthroplasty--accuracy versus ease of use.

The aim of this study was to compare the accuracy of four different methods for measuring wear using an apparatus that simulates known amounts of three dimensional wear. Wear was measured using the manual methods reported by Charnley, Livermore, Dorr and Wan and the computerized method reported by Devane. Only the method reported by Devane measured the three-dimensional (superior and anterior) wear with a reasonable accuracy, with a mean measurement error of 0.21 mm. With superior wear alone, Charnley's method underestimated the extent of wear by 16.6%, with a mean error of 0.35 mm; Livermore's method estimated wear to within 9.5%, with a mean error of 0.16 mm; Devane's method estimated wear to within 9.5%, with a mean error of 0.15 mm; and Dorr's method underestimated wear by 25.4%, with a mean error of 0.56 mm. Dorr's method was modified as a result of the experimental tests. The clinical application of the new method showed comparable data to that using the Devane method. In conclusion, this new method can be used to estimate the average wear in groups of patients accurately.

Equipment Failure Analysis↗
PubMed1990

Survival of cemented total hip replacements.

A Kaplan-Meier survival analysis of 240 Charnley, 149 Mueller (Depuy, Warsaw, IN), 576 Trapezoidal 28 (Zimmer, Warsaw, IN), and 100 Miami Orthopaedic Surgical Clinics (Biomet, Warsaw, IN) cemented total hip replacements with all polyethylene acetabular components, performed by the senior author (M.A.R.) should be the basis that all noncemented total hip replacements must exceed to be a reasonable alternative. Failure, ie, revision and a loose prosthesis, shows that 80%, 61%, and 63% of the Charnley, Mueller, and Trapezoidal 28, respectively, survive longer than 15 years. The Miami Orthopaedic Surgical Clinics prosthesis, which uses current cement technology, has been observed for only 8 years. Despite the fact that there are no differences noted between all four prostheses at 8 years, more time is needed to judge the usefulness of current cement technology.

Aged↗
PubMed1994

Do abnormal hemipelvic bone stresses contribute to loosening and migration of screw-threaded cups?

Excellent long-term results have been reported with the Charnley low-friction arthroplasty. Failure of the cemented acetabular component has been identified as a problem in the longer term, while cemented hip replacements in active young patients have exhibited a disconcerting incidence of early clinical or radiological failure. This resulted in the development of the cementless arthroplasty. Bone responds favourably to an optimal stress window and reacts dynamically to metal implants that have a greatly differing modulus of elasticity. This study represents a comparative qualitative analysis of the peri-acetabular hemipelvic stresses after loading two cementless (press-fit and screw-threaded) acetabular components inserted into identical bone models. A simplified model of the artificial hip joint was constructed and the very sensitive stress analysis technique of holographic interferometry was used for the investigation. Peri-acetabular stress concentrations were noted with the screw-threaded cup. This may predispose to bone resorption and it is suggested that these could be implicated in the migration of these cups described in published reports.

Cadaver↗
PubMed2001

[Case report of bioprosthetic mitral valve malfunction associated with right pulmonary embolism and heart failure].

The perioperative treatment of open heart surgery cases with preoperative pulmonary embolism is controversial. A 40-year-old woman, who had undergone mitral valve replacement with a bioprosthetic valve 16 years earlier, showed severe heart failure, right pulmonary embolism diagnosed by pulmonary perfusion scan in the subacute stage, and prosthetic valve regurgitation. Preoperative catheterization showed severe pulmonary hypertension of 122 mmHg, equal to the systemic pressure. Pulmonary angiography showed right peripheral pulmonary embolism without main pulmonary artery embolism. Prosthetic valve replacement with a BICARBON 27 M and tricuspid annuloplasty were performed, with thrombolytic therapy before and after operation without thrombectomy, because of pulmonary hypertension attributed to prosthetic valve regurgitation. Pulmonary perfusion scan and angiography showed improvement of pulmonary embolism after treatment. Postoperative catheterization showed good results, with right and left pulmonary artery pressure of 43/16(23) and 39/15(24) mmHg, mean pulmonary capillary wedge pressure of 4 mmHg, and cardiac index of 4.96 l/min/m2. It is important to make an early diagnosis of pulmonary embolism and treat the major cause of pulmonary hypertension in cases of cardiac valve disease with pulmonary hypertension.

Adult↗