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At least 811 records · Page 45Linked to original sources
PubMed2005

Percutaneous closure of an aortic prosthetic paravalvular leak with an Amplatzer duct occluder.

Following aortic valve replacement, up to 5% of patients may develop clinically significant paravalvular leaks. Reoperation is associated with higher mortality and an excess risk of recurrent paravalvular insufficiency. No specifically designed transcatheter device is available for paravalvular leak repair. We describe in a patient with severe aortic prosthetic paravalvular leak the use of an Amplatzer duct occluder device resulting in effective closure and symptomatic improvement.

Aged↗
PubMed2003

Preliminary study of interfacial shear strength between PMMA precoated UHMWPE acetabular cup and PMMA bone cement.

Followed by successful demonstration of high interfacial tensile strength in a new design of cemented all-polyethylene acetabular cup, interfacial shear strength was investigated in this study, with the use of canine-size prototypes of polymethylmethacrylate (PMMA) precoated UHMWPE acetabular cups. In addition to the PMMA precoated prototypes, three different types of controls were also prepared and tested: grooved UHMWPE cups, PMMA (bone cement) cups, and noncoated, plain UHMWPE cups. The interfacial shear strength of the precoated prototypes was 10.1 +/- 0.69 MPa (n = 6), whereas it was 24.3 +/- 0.78 MPa (n = 2) for the PMMA cup, 6.95 +/- 0.21 MPa (n = 2) for the grooved UHMWPE cup, and 0.34 +/- 0.47 MPa (n = 2) for the UHMWPE cup. These results indicate benefits of the PMMA precoating to stabilize the polyethylene acetabular cup securely when applied with bone cement in simulated clinical applications. Analysis of the failed PMMA precoated UHMWPE prototype cups suggested that the chemically induced bonds between precoated PMMA layer and bone cement played a key role in developing high shear strength. After the interfacial shear test of the PMMA precoated prototypes, major disruptions at the interface between treated UHMWPE and precoated PMMA layer were observed by scanning electron microscopy (SEM), which was a unique failure pattern, not found with other prototypes.

Animals↗
PubMed2003

Reduction of wear in total hip replacement prostheses by amorphous diamond coatings.

Wear-debris-induced periprosthetic bone loss and aseptic loosening is regarded as the main long-term problem of total hip replacements (THRs). In this study the amount of wear debris from articulating surfaces of THRs was reduced so as to be close to negligible by the use of high-quality amorphous diamond (AD) coatings deposited by pulsed plasma arc techniques. The wear rates determined in a commercial hip simulator for 15 million walking cycles (corresponding to about 15 years of clinical use) in serum lubrication were even 1,000,000 times lower than the clinical values for conventional THRs (polyethylene-metal or metal-metal pairs). Elimination of wear debris and good biomechanical performance should provide a substantial improvement of the clinical longevity of the THRs.

Biocompatible Materials↗
PubMed2003

Clinical and simulator wear study of alumina ceramic THR to 17 years and beyond.

Three THAs with cementless monolithic alumina ceramic sockets and cementless Co-alloy stems were retrieved because of aseptic loosening after 17 and 24 years. At revision heads and cups were marked for orientation. Maps were drawn of wear patterns with the use of light microscopy and surveyed by SEM. In a simulator experiment 28-mm-diameter alumina heads and liners were used. The cups were mounted inverted in a hip simulator and run with calf serum as the lubricant. The hip loads were 2 kN maximum and a 1-Hz frequency for 20 million cycles. Wear severity was classified into five grades. In retrieved implants, SEM analysis showed that the main wear zones (MWZ) had Grade 4 wear. The peripheral wear zones (PWZ) showed grain pull-out regions (Grade 5 wear). These corresponded to neck-socket impingement and head-acetabular cup separation. Gray was due to transferred CoCr particles from the stem. In the simulator study, the MWZ had only localized areas of grain pull out surrounded by polished surface regions (Grade 4 wear) at 20 million cycles; stripe wear was not seen. The alumina ceramic bearings proved excellent up to 22 years in simulator studies and clinical studies. However, microseparation kinematics would be necessary in the simulator to duplicate the more peripheral wear zones.

Adult↗
PubMed2003

In vitro corrosion testing of modular hip tapers.

The in vivo fretting behavior of modular hip prostheses was simulated to determine the effects of material combination and a unique TiN/AlN coating on fretting and corrosion at the taper interface. Fretting current, open-circuit potential (OCP), and quantities of soluble debris were measured to determine the role of mechanically assisted crevice corrosion on fretting and corrosion of modular hip tapers. Test groups consisting of similar-alloy (Co-Cr-Mo head/Co-Cr-Mo neck), mixed-alloy (Co-Cr-Mo head/Ti-6Al-4V neck), and TiN/AlN-coated mixed-alloy modular hip taper couples were used. Loads required to initiate fretting were similar for all test groups and were well below loads produced by walking and other physical activities. Decreases in OCP and increases in fretting current observed during long-term cyclic loading were indicative of fretting and corrosion. Current measured after cessation of cyclic loading suggests that once the conditions for crevice corrosion are established, corrosion can continue in the absence of loading. The chemical, mechanical, and electrochemical measurements, along with microscopic inspections of the taper surfaces indicate that the fretting and corrosion behavior of similar- and mixed-alloy taper couples are similar and that the coated samples are more resistant to fretting and corrosion. The results of this study clearly indicate the role of mechanical loading in the corrosion process, and support the hypothesis of mechanically assisted crevice corrosion.

Alloys↗
PubMed1998

[Radiologic results of the ARO multicenter study].

We present the radiological results of 2286 total hip replacements (THR) from the multicenter study. Concerning the acetabular component the analysis showed that socket migration and radiolucent lines were much more dependent on the specific design of the socket than on the primary diagnosis. A similar results was found for the femoral stems: rheumatoid arthritis did not cause a higher percentage of stem subsidence, radiolucent lines or bone remodeling. Within a mid-term follow-up period the reduced bone quality in rheumatoid arthritis is not associated to premature failure of a cemented or cementless prosthesis. THR failure seems to be more dependent on specific construction features of the individual socket and stem.

Arthritis, Rheumatoid↗
PubMed2004

Arrhythmia risk stratification with regard to prophylactic implantable defibrillator therapy in patients with dilated cardiomyopathy. Results of MACAS, DEFINITE, and SCD-HeFT.

To date, generally accepted indications for prophylactic defibrillator implantation in patients with dilated cardiomyopathy do not exist. Recently, the Marburg Cardiomyopathy Study (MACAS) revealed left ventricular ejection fraction to be the only significant arrhythmia risk predictor in a relatively large patient population with dilated cardiomyopathy. Meanwhile, the preliminary results of two prospective randomized trials evaluating prophylactic defibrillator therapy in dilated cardiomyopathy have been reported. The Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation study (DEFINITE) randomized 458 patients with a history of symptomatic heart failure, a left ventricular ejection fraction < or = 35% and arrhythmias on Holter to an ICD versus no ICD. As a result, ICD therapy was associated with a significant reduction of arrhythmic deaths, which failed to result in a significant decrease in total mortality due to an insufficient number of patients in DEFINITE. The Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) was a three-arm study comparing placebo to amiodarone to prophylactic ICD therapy in a total of 2,521 patients with ischemic cardiomyopathy (51%) or nonischemic dilated cardiomyopathy (49%). All patients in SCD-HeFT had a left ventricular ejection fraction inverted exclamation mark U 35% despite optimized medical heart failure therapy. SCD-HeFT showed a significant reduction of total mortality in the ICD group, whereas amiodarone did not improve survival.

Arrhythmias, Cardiac↗
PubMed2005

Comparative surface examinations on corund blasted titanium implants and explants in total hip arthroplasty.

INTRODUCTION: Blasting techniques using corundum to create rough surfaces are used in many different processes for the surface treatment of hip implants. Recent evidence points an association between residual particles and early loosenings in the sense of third-body wear. MATERIALS AND METHOD: The surfaces of five unused, original-packaged CLS stems and ARR-Titan supporting rings, respectively, were compared with five explanted CLS stems and ARR-Titan supporting rings. RESULTS: The surface of the ARR-Titan supporting rings was adhered to Al2O3 particles at 23.2+/-2.5% on the implants and 12.3+/-3.0% on the explants (P < 0.0001). For the CLS stem, the surface to which Al2O3 particles adhered was 16.4+/-2.2 % on the implants, whereas the surface to which Al2O3 particles adhered was 12.4+/-3.3% on the explants (P = 0.0275). DISCUSSION: The results of this study show that corundum particles can be found to cover a high percentage on rough-blasted titanium surfaces of ready-to-use devices. In contrast, this contamination is significantly less on the explants treated in an identical fashion prior to implantation.

Aluminum Oxide↗
PubMed1993

Diamond-like carbon: a potential means of reducing wear in total joint replacements.

This paper begins with a review of recent studies of the progressive mechanisms of degradation in total hip and knee replacements. It is concluded that wear is a major problem due to resulting tissue reactions especially to fine polymeric debris. Methods of lessening or overcoming these problems by modern methods of surface modification are considered, among these being ion implantation and ion beam-assisted deposition. It is argued that the physical and chemical properties of diamond-like carbon (DLC) coatings make them especially promising for the reduction of friction and adhesive wear in all forms of joint replacement. An ion beam-assisted method of depositing DLC efficiently at low temperatures is described, together with the physical properties of the resulting material.

Adhesiveness↗
PubMed1995

Custom CAD/CAM total temporomandibular joint reconstruction system: preliminary multicenter report.

PURPOSE: The purpose was to test the outcome of a custom computer assisted design/computer assisted manufactured (CAD/CAM) total temporomandibular joint (TMJ) reconstruction system. PATIENTS AND METHODS: There were 215 patients (13 males and 202 females); the average age at reconstruction was 40.9 +/- 10.3 years (range, 15 to 77 years). There were 363 joints placed, 296 bilateral and 67 unilateral. The patients had TMJ problems for an average of 10.3 +/- 7.0 years (range, 1 to 44 years), and had undergone a mean of 5.4 +/- 4.8 (range, 0 to 28) prior unsuccessful surgeries. Preoperative and postoperative data were collected for up to 48 months using a standardized data collection format. Subjective data related to pain, function of the lower jaw, and diet, were obtained using a visual analogue scale. Objective measures of mandibular range of motion were made directly on the patient preoperatively and postoperatively. RESULTS: Preliminary analysis of these data reveals a statistically significant decrease in pain, an increase in function, and improvement in diet (P < .0001) from the preoperative measurements to 1 and 2 years postoperatively. There was also improvement in mandibular vertical range of motion. The number of previous surgeries was a strong predictor of postoperative pain, function, and diet scores, as well as of maximal interincisal opening. A life table analysis of failures indicates good durability of the prosthesis over time. CONCLUSION: These preliminary data indicate that this custom CAD/CAM total TMJ reconstruction system seems to be useful in the treatment of the multiply operated, and/or anatomically mutilated TMJ.

Adolescent↗
PubMed2006

Factors influencing the initial micromotion between polyethylene acetabular cups and titanium alloy shells.

Mechanical test factors affecting short-term rotational stability under combined torsional and compressive loading was assessed in modular press-fit acetabular components with 4 different locking mechanism designs, by measuring the micromotion of the liner-shell interface at either room (20 degrees C) or body temperature (37 degrees C) and with either a high (2,943 N) or low (490 N) compressive load. Liner-shell constructs whose short-term stability was statistically significantly affected by temperature exhibited more rotational stability at body temperature than at room temperature. Liner-shell constructs whose short-term stability was statistically significantly affected by the level of compressive load exhibited more rotational stability with high compressive loads than with low loads. Liner-shell constructs with different locking mechanism designs were influenced by temperature and compressive loads differently. It is recommended to consider including these factors in tests of acetabular component locking mechanisms.

Acetabulum↗
PubMed2006

Does neck/liner impingement increase wear of ultrahigh-molecular-weight polyethylene liners?

We explore the hypothesis that repetitive impingement increases wear of ultrahigh-molecular-weight polyethylene inserts. During revision total hip arthroplasty, 113 acetabular components were retrieved and examined for impingement, backside wear, and articular wear. Sixty percent of acetabular liners showed evidence of prosthetic impingement, with moderate or severe damage to the rim in 32%. Moderate or severe backside damage was present in 31%. Backside wear was found in 61% (22/36) of liners exhibiting impingement vs 16% (12/73) of liners without impingement (P < .0001). The average articular wear rate of liners with moderate/severe impingement damage was 159 +/- 42 mm(3)/y, compared with 70 +/- 21 mm(3)/y for liners with no/mild impingement damage (P = .02). Repetitive impingement frequently occurs after total hip arthroplasty and leads to a multitude of adverse events, including motion between the liner and the acetabular shell.

Acetabulum↗
PubMed2005

Wear behaviour of cross-linked polyethylene assessed in vitro under severe conditions.

The polyethylene (PE) for hip implants presents serious clinical problems; the production of debris may induce adverse tissue reactions that may lead to extensive bone loss around the implant and consequently osteolysis and implant loosening. Several attempts have been made to improve the wear properties of ultra-high molecular weight polyethylene (UHMWPE). More recently the attention of various researchers has been focused on cross-linked polyethylene (XLPE), due to its improved wear resistance with respect to conventional UHMWPE. This study was aimed at comparing the wear performances of clinically available acetabular liners (Zimmer Inc.) made of electron beam XLPE and conventional UHMWPE. To evaluate the influence of the material properties on wear, conventional UHMWPE and XLPE acetabular cups were tested against deliberately scratched CoCrMo femoral heads (Ra = 0.12-0.14 microm) in a hip joint wear simulator run for 3 million cycles with bovine calf serum as lubricant. Gravimetric measurements revealed significant differences between the wear behaviours of the two sets of acetabular cups: XLPE exhibited a wear rate about 40 times lower than conventional UHMWPE. Raman spectroscopy coupled to partial least-squares analysis was used to evaluate the possible crystallinity changes induced by mechanical stress (and thus the material wear resistance): only the UHMWPE cup which showed the highest weight loss displayed significant crystallinity changes. These results were correlated to the thickness of the plasticity-induced damage layer. The wear debris produced during the tests were isolated according to a validated protocol and imaged by scanning electron microscopy . The wear particles produced by XLPE were smaller than those produced by UHMWPE; the latter were observed as fibrillar and agglomerated particles. The mean equivalent circle diameter was 0.71 and 0.26 microm for UHMWPE and XLPE, respectively.

Arthroplasty, Replacement, Hip↗
PubMed2005

Oxidative degradation in highly cross-linked and conventional polyethylene after 2 years of real-time shelf aging.

Previous studies have reported oxidative degradation of conventional polyethylene (PE) components during shelf aging, following radiation. However, no studies have yet reported data concerning the effect of real-time shelf aging in the manufacturer's packaging on the oxidative degradation of commercially available highly cross-linking PE components. The null hypothesis tested was that in either highly cross-linked or conventional PE acetabular components there would be no significant difference in the amount of oxidative degradation between time zero PE liners and PE liners that had been real-time shelf aged for 2 years in their respective packaging. The results of the study indicated that after 2 years of real-time shelf aging, negligible oxidative degradation occurred with minimal changes in oxidation index, density, and percent crystallinity in commercially available highly cross-linked and conventional PE acetabular liners. These data suggested that oxidative degradation was not a clinical issue in the highly cross-linked and conventional PE components examined after 2 years of real-time shelf aging. It is likely that current manufacturing and packaging technologies have limited the previous clinical concerns related to oxidative degradation during shelf aging of highly cross-linked and conventional PE components.

Arthroplasty, Replacement, Hip↗
PubMed1995

Commissural dehiscence of Carpentier-Edwards mitral bioprostheses. Explant analysis and pathogenesis.

Manufacturing factors have seldom been implicated as a direct cause of structural deterioration of valvular bioprostheses; this phenomenon has generally been considered to be of a host-dependent origin. We analyzed the clinical and pathologic data from 12 Carpentier-Edwards mitral bioprostheses removed from 12 patients because of severe dysfunction and showing detachment of the porcine aortic wall from the stent in one commissure or more. These 12 prostheses were part of a group of 92 such valves that were explanted and displayed structural deterioration. They belong to a population of 405 Carpentier-Edwards bioprostheses implanted in the mitral position in our institution between May 1978 and November 1988. The patients included three men and nine women with a mean age of 54 +/- 13 years. One patient had a history of chronic renal failure, and two had systemic hypertension. Prosthesis sizes were 29, 31, and 33 mm (n = 4 for each size). The models of the valves were 6625 (n = 8) and 6650 (n = 4). Mean duration of implantation of the prostheses was 99 +/- 27 months (52 to 136 months) and did not differ depending on the model. There was no significant clustering of commissural detachments depending on valve size, year of implantation, or gender of the patient. No similar phenomenon was observed among 76 explanted aortic Carpentier-Edwards bioprostheses with structural deterioration from a population of 441 valves implanted during the same time frame. Native porcine aortic roots (n = 5) and aortic Carpentier-Edwards bioprostheses explanted because of structural deterioration (n = 4) were used as controls for comparison. Macroscopic examination showed single commissural dehiscence in 10 patients and double in two. Radiology disclosed no or mild mineralization in eight valves and no calcium in the area of aortic wall dehiscence, except for heavily calcified valves. Light microscopy evidenced a significant thinning of the aortic wall at the paracommissural level of mitral bioprostheses (351 +/- 68 microns) compared with either aortic bioprostheses (526 +/- 59 microns; p < 0.01) or control native porcine aortic roots (419 +/- 50 microns; p < 0.01). No difference was found in terms of aortic wall thickness between detached (322 +/- 42 microns) and intact (366 +/- 74 microns) commissures in mitral bioprostheses.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗