Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PROSTHESES”

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 775 records · Page 43Linked to original sources
PubMed1988

Complement activation by vascular prostheses and its role in progression of arteriosclerotic lesions.

This study, using C3a, C4a, and C5a assay and crossed immunoelectrophoresis in vitro and in vivo, was designed to determine whether vascular prostheses activate the complement system. The degree of complement activation and the pathway of activation were also studied. The complement levels (C3, C4, CH50) in different arterial diseases were measured, and the relationship of complement levels to serum lipids in patients with arteriosclerosis obliterans (ASO) was also investigated, in order to clarify a relationship between the complement system and arteriosclerosis or other arterial diseases. Bovine graft, dacron, and PTFE activated the complement system in vitro. In order of the degree of complement activation, bovine graft ranked first, followed by dacron and PTFE. The patient group with acute arterial occlusion showed high C3 and C4 levels. The healthy elderly group showed higher C3 and C4 levels than the healthy persons in their twenties. In ASO patients, C3 levels correlated with serum lipid levels. Judged from the relation of complement activation by vascular prostheses to the progression of arteriosclerotic changes, vascular prostheses should be assessed with regard to complement activation.

Arterial Occlusive Diseases↗
PubMed1993

Analysis of debond rates of resin-bonded prostheses.

Debonding rates of 164 resin-bonded prostheses (RBP) placed from 1974 to 1985 were examined at recall. The yearly debond rates were calculated, the cumulative probability of failure was determined for the debonded RBPs, and Weibull distribution parameters were determined. For perforated prostheses, there was a high initial debond rate, followed by slowly decreasing rates for about 5 years. Increasing rates after 5 years indicated the beginning of wear-out. The Weibull parameters for the wear-out period of the perforated prostheses were: characteristic life = 128 (SE = 2) months, modulus = 1.27 (0.06), and threshold parameter = 0. Data were available for etched frameworks for 6 years and showed decreasing debond rates during this time. The characteristic life of the etched bridges was 318 (84) months. The cumulative failure data were also modeled with a cubic polynomial distribution that resulted in a U-shaped hazard function.

Adolescent↗
PubMed1999

A within-subject comparison of mandibular long-bar and hybrid implant-supported prostheses: evaluation of masticatory function.

Sixteen edentulous subjects participated in a within-subject crossover clinical trial to test the hypotheses that a long-bar overdenture attached to 4 implants gives greater patient satisfaction and masticatory efficiency than a two-implant hybrid overdenture. All subjects were given a new maxillary conventional denture. Ten received mandibular long-bar overdentures first and six the hybrid overdentures. Two months later, psychometric assessments and functional tests were repeated 3 times at one-week intervals. The mandibular prosthesis was then changed, and recordings were repeated after another 2 months. Mandibular movements and electromyographic activity of jaw muscles were recorded while subjects chewed standard-sized pieces of 5 foods: bread, cheese, apple, sausage, and carrot. Measurements included masticatory time, cleaning time (the time between the end of mastication and the last swallow), and duration and amplitude of masticatory cycles and phases. Multilevel analyses were performed. No significant differences in masticatory time were found between prostheses for any test food. However, cleaning time for carrot [estimated mean of difference (delta) +/- SE: 1.6 sec +/- 0.7] and bread (delta = 1.0 sec +/- 0.4) was slightly but significantly longer for subjects wearing long-bar overdentures. Cycle duration was longer with the long-bar overdenture only for subjects chewing carrot. The opening phase was shorter and the closing phase longer with the long-bar overdenture for almost all test foods. Vertical amplitude was significantly less with the long-bar overdenture for cheese (delta = -2.6 mm +/- 1.1), apple (delta = -2.6 mm +/- 1.0), and sausage (delta = -2.9 mm +/- 1.3). These results suggest that mastication with the 2 prostheses is equally efficient, although clearance of some foods from the mouth is longer with the long-bar overdentures. They also indicate that patients adapt their masticatory movements to the characteristics of different prostheses.

Adult↗
PubMed2000

A new method for quantitative evaluation of perceived sounds from mechanical heart valve prostheses.

Closing clicks from mechanical heart valve prostheses are transmitted to the patient's inner ear mainly in two different ways: as acoustically transmitted sound waves, and as vibrations transmitted through bones and vessels. The purpose of this study was to develop a method for quantifying what patients perceive as sound from their mechanical heart valve prostheses via these two routes. In this study, 34 patients with implanted mechanical bileaflet aortic and mitral valves (St Jude Medical and On-X) were included. Measurements were performed in a specially designed sound insulated chamber equipped with microphones, accelerometers, preamplifiers and a loudspeaker. The closing sounds measured with an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the 'real-time' clicks he or she perceived directly from his or her valve. In this way the feedback sound energy includes both the air- and the bone-transmitted energies. Sound pressure levels (SPLs) were quantified both in dB(A) and in the loudness unit sone according to ISO 532B (the Zwicker method). The mean air-transmitted SPL measured close to the patient's ear was 23 +/- 4 dB(A). The mean air- and bone-transmitted sounds and vibrations were perceived by the patients as an SPL of 34 +/- 5 dB(A). There was no statistically significant difference in the perceived sound from the two investigated bileaflet valves, and no difference between aortic and mitral valves. The study showed that the presented feedback method is capable of quantifying the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to three times higher than nearby persons, because of the additional bone-transmitted vibrations.

Acoustics↗
PubMed2006

Biological effects of clinically relevant wear particles from metal-on-metal hip prostheses.

The problems of osteolysis and late aseptic loosening associated with ultra-high molecular weight polyethylene (UHMWPE) particles has lead to a renewed interest in metal-on-metal prostheses. Wear particles generated by modern Co-Cr-on-Co-Cr prostheses are nanometre in size (range: 10-120 nm; mean: about 40 nm), an order of magnitude smaller than the size of UHMWPE known to be critical for activation of osteolytic cytokines by macrophages. Co-Cr wear particles will induce osteolytic cytokine production by human macrophages, but only at high volumetric concentrations. Unlike UHMWPE, Co-Cr particles are not inert. Co-Cr particles have the potential to release metal ions; they may be toxic to cells, induce deoxyribonucleic acid damage or cause host hypersensitivity. The nanometre size range of Co-Cr wear particles means that they may be disseminated widely in the body. The potential for metal-on-metal bearings to induce adverse effects clinically will be dependent upon the rate of wear. What constitutes a safe wear rate for modern metal-on-metal bearings is unknown. However, the wear of metal-on-metal prostheses is critically dependent upon the design and, in particular, the carbon content of the alloy, the radial clearance, and the head diameter. Thus, the potential for adverse biological reactions associated with metal-on-metal bearings can be reduced by selection of appropriately designed implants.

Chromium Alloys↗
PubMed2005

NeuFlex metacarpophalangeal prostheses tested in vitro.

This paper describes the testing of three single-piece silicone NeuFlex metacarpophalangeal prostheses in a finger function simulator and describes the resulting modes of prosthesis failure. In all cases, failure was due to imminent fracture of the prosthesis across the pivot of the central hinge section. This result is in contrast with previous in-vitro and in-vivo experience with single-piece silicone Swanson and Sutter metacarpophalangeal prostheses, which both tend to fracture at the junction of the distal stem and the hinge. In comparison with earlier in-vitro simulator tests of the Sutter metacarpophalangeal prosthesis, the NeuFlex prostheses showed a greater longevity before fracture. To date, no other reports of fracture of the NeuFlex metacarpophalangeal prosthesis have been reported, either in vitro or in vivo.

Equipment Failure Analysis↗
PubMed1999

Three-dimensional surface characterization for orthopaedic joint prostheses.

This study attempts to investigate a range of 'better' methods for the characterization of the three-dimensional (3D) surface topography of orthopaedic joint prostheses. In this paper, a new characterization tool for the comprehensive identification and evaluation of functional features of these surface topographies is presented. For identification, the surface topography is investigated in a space-scale space, by employing wavelet analysis. The roughness, waviness and form involved in surface topography are consequently separated and recovered respectively. The multiscalar topographical features are identified and captured. The errors caused as a consequence of three-dimensional measurement methods can be reduced. After identification, the three-dimensional surface assessment techniques previously reported by Stout and co-workers are used for the quantitative evaluation of various surface roughness features of the orthopaedic joint prostheses. Moreover, the functional properties, such as bearing area, material volume and void volume which are significantly effected by large peaks, pits and scratches are studied and the location of isolated peaks, pits and scratches in the different scales is also clearly characterized. In this work, measurement of the femoral heads and acetabular cups is carried out to demonstrate the applicability of the characterization technique for the three-dimensional surface topography of orthopaedic joint prostheses.

Hip Prosthesis↗
PubMed2006

Importance of head diameter, clearance, and cup wall thickness in elastohydrodynamic lubrication analysis of metal-on-metal hip resurfacing prostheses.

The main design features of metal-on-metal (MOM) hip resurfacing prostheses in promoting elastohydrodynamic lubrication were investigated in the present study, including the femoral head diameter, the clearance, and the cup wall thickness. Simplified conceptual models were developed, based on equivalent uniform wall thicknesses for both the cup and the head as well as the support materials representing bone and cement, and subsequently used for elastohydrodynamic lubrication analysis. Both typical first- and second-generation MOM hip resurfacing prostheses with different clearances and cup wall thicknesses were considered with a fixed large bearing diameter of 50 mm, as well as a 28 mm diameter MOM total hip replacement bearing for the purpose of comparison. The importance of the head diameter and the clearance in promoting elastohydrodynamic lubrication was confirmed. Furthermore, it was also predicted that a relatively thin acetabular cup in the more recently introduced second-generation MOM hip resurfacing prostheses would be capable of improving elastohydrodynamic lubrication even further.

Acetabulum↗
PubMed1978

The radiation improvement of polyethylene prostheses. A preliminary study.

The radiation crosslinking of high-density polyethylene prostheses was investigated over a wide range of doses in the presence and absence of gaseous crosslinking agents. It was found that in the bulk polymer the crosslinking pattern is completely different from the homogeneous crosslinking that occurs in polymer films. The presence of crosslinking agents causes highly crosslinked polymer to be formed on the surface while the bulk of the polymer is largely unaffected--which is explained in terms of diffusion phenomena. This surface crosslinking has a profound effect on the mechanical properties of the prostheses and restricts cold flow and deformation of the polymer without sacrificing the excellent abrasion-resistance properties of the polyethylene when subjected to high pressures. Based on this research a number of high-density polyethylene knee prostheses have been radiation-crosslinked and the results in vitro appear to be very promising.

Acetylene↗
PubMed1992

Hydroxyapatite coating of hip prostheses. Effect on migration into the femur.

We studied two groups of femoral hip prostheses: 43 TiAlV ridged press-fit stems, and 26 with similar stems coated with hydroxyapatite on the proximal half. At one year, radiological measurement showed a mean downward migration of 0.99 mm for the TialV prostheses and 0.12 mm for the HA-coated prostheses (p = 0.0002). Hydroxyapatite coating appeared to provide effective bio-active supplementary fixation.

Adult↗
PubMed1997

Femoral component wear in retrieved hip prostheses.

We retrieved 159 femoral heads at revision surgery to determine changes in surface configuration. Macroscopic wear of the head was observed in three bipolar hip prostheses as a result of three-body wear. There was a considerable change in surface roughness in the internal articulation of bipolar hip prostheses. Roughness in alumina heads was almost the same as that in new cobalt-chromium heads. The annual linear wear rate of polyethylene cups with alumina heads was less than that of cups with cobalt-chromium alloy heads. Polyethylene wear was increased in the prostheses which had increased roughness of the head.

Adult↗
PubMed1998

Is there a future for hinged prostheses in primary total knee arthroplasty? A 20-year survivorship analysis of the Blauth prosthesis.

The Blauth prosthesis is a hinged total knee replacement. We have evaluated 422 consecutive primary total knee arthroplasties using this design in 330 patients with a maximum follow-up of 20 years (mean 6). The mean age of the patients at the time of operation was 70 years (29 to 87). Using endpoints of infection, removal because of aseptic loosening, removal for any cause, and the worst case as definitions of failure, the cumulative rates of survival at 20 years were 93.6%, 96.0%, 94.4% and 86.8%, respectively. The cumulative rate of survival of the patients themselves was 14.4% (24% in patients with osteoarthritis and 9% in these with rheumatoid arthritis) after 20 years. Our survivorship analysis shows that hinged knee prostheses, when they are biomechanically well designed, can yield a satisfactory long-term outcome, similar to those of the best prostheses of the resurfacing type. Hinged knee prostheses continue to be of value in patients with severe deformity or instability of the knee.

Adult↗
PubMed1998

Bone-resorbing cytokines in serum of patients with aseptic loosening of hip prostheses.

Our aim was to determine if the serum levels of bone-resorbing cytokines (IL-1beta, TNF-alpha, IL-6, GM-CSF) are altered in patients with aseptic loosening of a total hip prosthesis, and if such levels are influenced by the type of implant. We determined cytokine levels in sera from 35 patients before revision for failed total hip arthroplasty and compared them with those in 25 healthy donors. We also assessed the soluble receptor of interleukin-2 (sIL-2r) in serum as an indication of a specific immune reaction against the implant. Our findings showed that the sIL-2r and TNF-alpha serum level did not change. The IL-6 level was not significantly altered, but was higher in patients with TiAIV prostheses than in those with a CrCoMo implant and in patients with cemented prostheses. The IL-1beta level was found to be higher in those with a TiAIV cemented prosthesis than in the control group (p=0.0001) and other groups of patients (p=0.003 v uncemented TiAIV, p=0.01 v cemented CrCoMo, p=0.001 v uncemented CrCoMo). The GM-CSF level significantly increased in patients compared with healthy subjects (p=0.008), and it was higher in those with cemented than with uncemented implants (p=0.01). Only patients with cementless CrCoMo prostheses had levels of GM-CSF similar to those of the control group. The highest GM-CSF concentrations were observed in patients treated with non-steroidal anti-inflammatory drugs (NSAIDs) in the last months before revision (p=0.04). In addition, when massive osteolysis was observed, the level of GM-CSF tended to decrease to that of the control group.

Acetabulum↗
PubMed1999

Cytokine levels in synovial fluid from hips with well-functioning or loose prostheses.

We analysed synovial fluid from 88 hips, 38 with osteoarthritis and 12 with well-functioning and 38 with loose hip prostheses. The levels of TNF-alpha, IL-1beta (71 hips) and IL-6 (45 hips) were measured using the ELISA technique. Joints with well-functioning or loose prostheses had significantly increased levels of TNF-alpha compared with those with osteoarthritis. Hips with aseptic loosening also had higher levels of IL-1beta but not of IL-6 compared with those without an implant. The levels of TNF-alpha and IL-1beta did not differ between hips with stable and loose prostheses. Higher levels of TNF-alpha were found in hips with bone resorption of type II and type III (Gustilo-Pasternak) compared with those with type-I loosening. The level of cytokines in joint fluid was not influenced by the time in situ of the implants or the age, gender or area of the osteolysis as measured on conventional radiographs. Our findings support the theory that macrophages in the joint capsule increase the production of TNF-alpha at an early phase probably because of particle load and in the absence of clinical loosening. Since TNF-alpha has an important role in the osteolytic process, the interfaces should be protected from penetration of joint fluid.

Adult↗
PubMed1975

Late postoperative anatomic observations after insertion of Hufnagel caged-ball prostheses in descending thoracic aorta.

Clinical and necropsy observations are described in two patients who died 11 and 13 years, respectively, after implantation of Hufnagel prostheses (the first ever used successfully in humans to treat cardiac valve disease) in descending thoracic aorta. Despite the long implantation periods, there was no evidence of prosthetic degeneration or thrombosis or intravascular hemolysis. Although approximately 4000 Hufnagel descending aortic prostheses were distributed by the manufacturer for human use, data in only 55 patients in whom these prostheses were inserted were found in previous publications, and 26 of them had died. Of the 13 late deaths previously reported, no evidence of prosthetic degeneration or thrombosis was described in the three patients surviving greater than 3 years (8, 10, 12.5 years, respectively). Since neither our patients nor any of the other three reported long-term survivors had prosthetic-related complications and since the dangers of excising the descending aortic prosthesis are considerable, it appears most reasonable, as a rule, not to remove the descending aortic prosthesis at any time in these patients if aortic valve replacement is subsequently performed.

Adult↗
PubMed1995

[15 years experience with the Ti-6Al-7Nb alloy for joint prostheses].

The Ti-6Al-7Nb alpha-beta alloy, Protasul-100 was developed between 1978 and 1982, and proved to be highly biocompatible. In 1985 the TiAlNb material was approved for clinical use. Over the last ten years, more than 200 tons of semi-finished bar material has been processed, mainly for the production of cementless femoral stem systems and elastically deformable cup shells. For uncemented femoral components of knee prostheses made of TiAlNb, a special oxygen diffusion hardening process was developed that enables a surface hardness of up to 1200 HV and 600 HV at a depth of 20 microns, as compared with 350 HV in the case of the TiAlNb base material. This ODH-treated, polished surface is extremely scratch and wear resistant, and forms a good articulating surface with UHMW polyethylene. This surface-hardened TiAlNb, Tribosul, has been in clinical use in femoral knee components since 1990, and a multicentric clinical study involving femoral heads for hip prostheses has been ongoing since 1992. These different applications in hip and knee joint prostheses may suffice to demonstrate that the custom-made Ti-6Al-7Nb alpha-beta alloy is a real alternative to the well-known Ti-6Al-4V alloy, which has been used for decades as an implant material. Both national and international standards are available, and the alloy was already approved by the FDA in 1987.

Alloys↗
PubMed2004

New flexible polymeric heart valve prostheses for the mitral and aortic positions.

OBJECTIVE: Current prosthetic heart valves necessitate permanent anticoagulation or have limited durability and impaired hemodynamic performance compared with natural valves. We report in vivo and in vitro results with new polymeric valve prostheses that have a special design for the mitral and aortic positions. The aims are improved durability and elimination of the need for permanent anticoagulation. METHODS: The mitral and aortic prostheses (Adiam Life Science, Erkelenz, Germany) are made entirely of polycarbonate urethane (PCU). The bileaflet asymmetric mitral valve mimics natural, nonaxial inflow, which creates a left ventricular vortex, saving energy for systolic ejection of blood. The trileaflet aortic prosthesis has diminished pressure loss and reduced stress and strain peaks at the commissures. The valves were subjected to long-term in vitro testing and in vivo testing in a growing calf model (20 weeks; 7 mitral and 7 aortic valves) with comparison with 2 commercial bioprostheses (7 mitral, 2 aortic). Two-dimensional echocardiography was performed after implantation and prior to sacrifice with autopsy and valve examination. RESULTS: In vitro durability of the PCU valves was proved up to 20 years. In vivo durability and hemodynamics were superior to those of all bioprostheses. Survival of PCU valves versus bioprostheses was 7 versus 2 mitral valves and 5 versus 0 aortic valves, respectively. Two animals with PCU aortic valves died of pannus overgrowth that caused severe left ventricular outflow tract obstruction without changes in the valves. Degeneration and calcification were mild (mitral) and moderate (aortic) in PCU valves but were severe in biological valves. There was no increased thrombogenicity of the PCU valves compared with bioprostheses. CONCLUSION: The new flexible polymeric aortic and mitral valve prostheses were superior to current bioprostheses in animal testing.

Aortic Valve↗
PubMed1995

Early experience with the Sydney and EVT prostheses for endoluminal treatment of abdominal aortic aneurysms.

PURPOSE: The aim of this study was to report early experiences with the Sydney and Endovascular Technologies (EVT) prostheses for the treatment of abdominal aortic aneurysms (AAA) deemed suitable for endoluminal tube graft repair. METHODS: Consecutive endoluminal tube graft repairs were analyzed over the first 12 months in which the Sydney and EVT prostheses were used. Patients eligible for the EVT prosthesis had type I AAAs: a proximal neck length > or = 2 cm, a distal cuff length > or = 1.5 cm, and nontortuous iliac arteries > or = 8 mm. Selection criteria for the Sydney device were more liberal and included AAAs that had distal cuffs < 1.5 cm. During the study period, 28 of 91 patients evaluated for AAA repair were thus selected for endoluminal grafting: 18 patients received the Sydney endograft and 10 the EVT device. Medical comorbidities were present in slightly less than one third of patients in both groups. Contrast-enhanced computerized tomography (CT) was performed preoperatively, within 10 days of operation, and at 6 and 12 months postprocedure. RESULTS: All endografts were successfully deployed in both groups. Postprocedural CT scans revealed incomplete aneurysm exclusion in four patients with the Sydney endograft. Subsequent deployment of a second endograft sealed these "leaks" in two cases; the other two were converted to open repair (89% clinical success). No leaks were seen with the EVT device. Local/vascular complications occurred in 33% of the Sydney group compared with 20% for the EVT device (p = 0.001); systemic sequelae were more common in the EVT group (30% versus 17% in the Sydney cohort, p = 0.002). There were no deaths within 30 days; three late deaths were not procedure related. CONCLUSION: AAAs that are suitable for endoluminal tube graft repair may be treated with a high rate of initial success with either the Sydney or EVT prostheses. More liberal selection criteria may increase the likelihood of local/vascular complications.

Aged↗