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At least 631 records · Page 35Linked to original sources
PubMed1994

Urologic prostheses.

Urologic prosthetics have become increasingly complex and include an assortment of urinary catheters, penile prostheses, artificial urinary sphincters, and testicular prostheses. The majority of urologic prosthetics are constructed of silicone because it is relatively inert, easily sterilized, maintains its strength, and has not been linked to malignancy. Nevertheless, silicone causes some local tissue reaction and deteriorates with time; thus, it is not the ideal prosthetic material. This article provides the clinician with an overview of the most common of these prostheses, their function, and a guide for the management of associated acute urologic complaints.

Emergencies↗
PubMed1998

Automatic tuning of myoelectric prostheses.

This paper is concerned with the development of a software package for the automatic tuning of myoelectric prostheses. The package core consists of Fuzzy Logic Expert Systems (FLES) that embody skilled operator heuristics in the tuning of prosthesis control parameters. The prosthesis system is an artificial arm-hand system developed at the National Institute of Accidents at Work (INAIL) laboratories. The prosthesis is powered by an electric motor that is controlled by a microprocessor using myoelectric signals acquired from skin-surface electrodes placed on a muscle in the residual limb of the subject. The software package, Microprocessor Controlled Arm (MCA) Auto Tuning, is a tool for aiding both INAIL expert operators and unskilled persons in the controller parameter tuning procedure. Prosthesis control parameter setup and subsequent recurrent adjustments are fundamental for the correct working of the prosthesis, especially when we consider that myoelectric parameters may vary greatly with environmental modifications. The parameter adjustment requires the end-user to go to the manufacturer's laboratory for the control parameters setup because, generally, he/she does not have the necessary knowledge and instruments to do this at home. However, this procedure is not very practical and involves a waste of time for the technicians and uneasiness for the clients. The idea behind the MCA Auto Tuning package consists in translating technician expertise into an FLES knowledge database. The software interacts through a user-friendly graphic interface with an unskilled user, who is guided through a step-by-step procedure in the prosthesis parameter tuning that emulates the traditional expert-aided procedure. The adoption of this program on a large scale may yield considerable economic benefits and improve the service quality supplied to the users of prostheses. In fact, the time required to set the prosthesis parameters are remarkably reduced, as is the technician's working time. This is interpreted as minor costs for prostheses manufacturers and suppliers.

Arm↗
PubMed2000

A decade of postlaryngectomy vocal rehabilitation in 318 patients: a single Institution's experience with consistent application of provox indwelling voice prostheses.

OBJECTIVE: To assess long-term results with consistent use of indwelling voice prostheses (Provox; Atos Medical AB, Hörby, Sweden) for vocal rehabilitation after total laryngectomy. DESIGN: Retrospective clinical analysis. SETTING: Comprehensive national cancer center. PATIENTS: Three hundred eighteen patients (261 men and 57 women; mean age, 62 years) from November 1988, through May 1999. INTERVENTION: Standard wide-field total laryngectomy (287 patients) or total laryngectomy with circumferential pharyngeal resection (31 patients), and 2700 prosthesis replacements. Prostheses remained in situ during 364,339 days (1000 patient-years). MAIN OUTCOME MEASURES: Device lifetime, indications for replacement (device or fistula related), adverse events, and voice quality. RESULTS: Median patient-device follow-up was 67 months. Mean actuarial device lifetime for all indications for replacement was 163 days (median, 89 days). Main indications for replacement were device-related, ie, leakage through the prosthesis (73%) and obstruction (4%), or fistula-related, ie, leakage around the prosthesis (13%), and hypertrophy and/or infection of the fistula (7%). Adverse events occurred in 11% of all replacements in one third of the patients, mostly solvable by a shrinkage period, or adequate sizing and/or antibiotic treatment. Definitive closure of the tracheoesophageal fistula tract occurred in 5% of the patients. Significant clinical factors for increased device lifetime were no radiotherapy (P =.03), and age older than 70 years (P<.02). Success rate with respect to voice quality (ie, fair to excellent rating) was 88%, which was significantly influenced by the extent of surgery (P<.001). CONCLUSION: The consistent use of indwelling voice prostheses shows a high success rate of prosthetic vocal rehabilitation, in terms of the percentage of long-term users (95%), and of a fair-to-excellent voice quality (88% of patients).

Adult↗
PubMed1988

Histology of synthetic ossicular prostheses.

Thirty-three synthetic middle ear prostheses removed after two to 99 months of implantation were examined histologically. All prostheses were infiltrated by fibroblasts, capillaries, collagen fibrils, and multinucleate foreign body giant cells. Although some of the giant cells contained tiny particles of the prosthetic material, there was no evidence of erosion or engulfment of larger particles of the prosthesis or structural dissolution of the prosthesis. New histologic findings were aseptic necrosis and focal calcification in the interior of some of the prostheses.

Ear, Middle↗
PubMed1999

Enhanced expression of P-selectin (CD62P) by endothelial cells seeded onto synthetic arterial prostheses (PET, Dacron) is correlated with leukocyte interactions.

This study evaluated the expression by seeded endothelial cells (S-EC) of P-selectin (CD62P/GMP-140/PADGEM), an adhesion molecule implicated in endothelial-leukocyte interactions. Endothelial cells were seeded onto knitted polyethylene terephthalate (PET, Dacron(R)) prostheses and compared with control endothelial cells (C-EC) cultured in flasks to the same stage. Using flow cytometry techniques, we observed that CD62P expression by PET S-EC was significantly increased (p<0.05) compared to C-EC. Moreover, RT PCR techniques showed that the CD62P RNA level was higher on S-ECs compared to C-ECs. Following adhesion assays, increased polymorphonuclear neutrophil (PMN) attachment to the PET-seeded prostheses as compared to control cultures (p<0.001) was observed. PMN adherence was enhanced by TNFalpha activation. PMN adhesion was decreased significantly (p<0.001) after the incubation of resting EC or TNFalpha-activated EC-seeded prostheses with a blocking monoclonal antibody (LYP20) directed against the P-selectin. Such results suggest that: (1) PET prosthetic material may induce the expression of P-selectin by S-EC; (2) seeding conditions provoke an increase in PMN adhesion; (3) increased PMN interactions with seeded PET material is partially dependent upon P-selectin expression by the S-EC.

Animals↗
PubMed1999

In vivo evaluation of modified mandrel-grown vascular prostheses.

The Omniflowtrade mark Vascular Prosthesis (OVP) has been manufactured and extensively tested in animal and human trials. It has mechanical and biological qualities superior to synthetic and biological conduits, particularly in low flow conditions. For further development into the smaller diameter coronary prostheses, the inner luminal surface is of paramount importance. In a previous study this inner surface was modified to produce a more uniformly thicker nonundulating surface. In this study the mandrels of these modified OVPs were treated with either collagen or heparin; the OVPs were evaluated for patency, tissue integration and wound healing, and endothelialization using a dog model comparable to that used to evaluate the unmodified OVP. In all instances, each of the modified prostheses were fully patent and had no signs of any deleterious effects caused by these modifications; no thrombus or aneurysms were visible. The tissue response was rapid with excellent new host collagen deposition within the vessel wall and minimal inflammatory and foreign body giant cells. Endothelialization was noted at the earliest explant time point in central regions of the prostheses, albeit that the histological picture at this time point appeared to reflect a complex atypical intimal layer.

Animals↗
PubMed2004

Carcinogenic potential of commonly used hernia repair prostheses in an experimental model.

BACKGROUND: The purpose of this study was to assess the carcinogenic potential of commonly used hernia repair prostheses in an animal model. METHODS: Three types of prosthetic material (monofilament polypropylene, multifilament polypropylene and expanded polytetrafluoroethylene) were implanted in CBA/H mice. Flat (1 cm(2)) and rolled pieces of the same material were placed subcutaneously in either flank, and a further flat piece was placed in the preperitoneal space. Owing to a high incidence of mesh extrusion in the polypropylene groups, the study protocol was modified to allow only preperitoneal placement of the material. A fourth, control, group had the pockets for the prostheses created but no material implanted. After modification of the protocol there were approximately 60 mice in each group. The mice were followed for 2 years, then killed and assessed histologically for tumour development. RESULTS: No sarcoma developed at the site of mesh implantation in any of the groups. CONCLUSION: This study indicates that the risk of sarcoma formation at the site of hernia repair prostheses is very low.

Animals↗
PubMed2001

Biofilm formation and design features of indwelling silicone rubber tracheoesophageal voice prostheses--an electron microscopical study.

After total laryngectomy, voice can be restored with a silicone rubber tracheoesophageal voice prosthesis. However, biofilm formation and subsequent deterioration of the silicone material of the prosthesis will limit device life by impairing valve function. To simulate the natural process of biofilm development under dynamic nutrient conditions, a modified Robbins device was used to evaluate the biofilm-related valve dysfunction of the Groningen, Provox2, Blom-Singer indwelling, and VoiceMaster voice prostheses. Obstruction of the semicircular slit-valved Groningen prosthesis leading to increased airway resistance was caused not only by a buildup of deposits on the esophageal flange and valve hat, but also by accumulation of deposits on the semicircular valve seating. The hinged flap valved Provox2 and indwelling Blom-Singer prostheses failed to close sufficiently because of biofilm formation on the valve seating. The esophageal flange of the VoiceMaster prosthesis was affected, but the tripod structure of the ball valve was fully colonized up to the titanium sleeve, which interfered with proper valve opening and closure. These findings on biofilm formation could be used for the further development and modification of critical design features of voice prostheses to facilitate tracheoesophageal speech.

Bacterial Adhesion↗
PubMed1975

Fatigue fractures of the femoral component of Charnley and Charnley-Müller type total hip prostheses.

A survey is given of the mechanical failures of the femoral component of Charnley and Charnley-Müller type total hip prostheses. Fractographic analysis reveals that all the prostheses have broken by metal fatigue. A review of the clinical data has been combined with a metallurgical and a mechanical study in order to assess the reasons of the mechanical failures. The following conclusions have been reached. The prosthesis should be inserted in varus position with regard to the axis of the intramedullary canal, and the prosthesis should be made of an alloy with appreciably higher yield stress and fatigue strength than the alloys of the investigated broken Charnley and Charnley-Müller type prostheses.

Alloys↗
PubMed1981

Investigations on the galvanic corrosion of multialloy total hip prostheses.

Total hip prostheses combining cobalt and titanium alloys in direct physical contact are currently being used. The purpose of this paper was to investigate the possibility of an accelerated corrosion occurring due to the coupling of these alloys. Electrochemical corrosion studies based on mixed potential and protection potential theories were used to study the in vitro effects of coupling the titanium and cobalt alloys. Verification of these studies was made by direct coupling experiments. Macroscopic examination of' surface features of four retrieved total hip prostheses ranging from 0-6 years implantation were conducted. The electrochemical studies predicted coupled corrosion potentials of -0.22 V and low coupled corrosion rates of 0.02 microA/cm2. Direct coupling experiments verified these results. Cobalt-titanium interfaces on the implants were macroscopically examined, and no instances of extensive corrosion were found. Overall, the in vitro corrosion studies and the examination of retrieved prostheses predicted no exaggerated in vivo corrosion due to the coupling of these cobalt and titanium alloys.

Alloys↗
PubMed1982

Durability of pyrolytic carbon-containing heart valve prostheses.

To assess abrasive wear of mechanical valve prostheses containing pyrolytic carbon components, we recovered at necropsy or surgery and analyzed by scanning electron microscopy and surface profilometry eight prostheses. Seven were implanted for 30-85 (mean 50 months. Valves included DeBakey aortic (2), DeBakey mitral (1), Beall mitral (2), Bjork-Shiley aortic (1), Cooley-Cutter mitral (1), and Lillehei-Kaster (L-K) tricuspid (1). All carbon occluders had undetectable wear. Carbon cage struts had a superficial burnish. Metallic struts had insignificant wear marks. In contrast, a Teflon Beall Model 104 valve implanted for 34 days and similarly analyzed had considerable material loss from the cage struts. This study suggests that clinically important abrasive wear will not be a late complication of cardiac valve replacement with pyrolytic carbon prostheses.

Adult↗
PubMed1984

Molecular weight characterization of virgin and explanted polyester arterial prostheses.

The macromolecular properties of 17 virgin commercial arterial prostheses and a series of explanted prostheses, both manufactured from poly(ethylene terephthalate) (PET) yarns, have been studied by gel permeation chromatography (GPC) and by differential scanning calorimetry (DSC). Only small differences were found between the average molecular weights and the degree of crystallinity of the unused reference grafts. A broadening of the DSC curves was observed for the prostheses containing texturized yarns compared with those made solely from flat, untexturized yarns. This broadening may be due to greater heterogeneity of the crystal sizes caused by the texturizing process and to the use of two or more different yarns with dissimilar thermal histories in the same prosthesis. Average molecular weights of the explant series were significantly lower than those of the corresponding reference grafts but almost time independent. The polydispersity index and the degree of crystallinity of the explants remained constant as a function of time. These results are discussed in regard to others available in the literature.

Adult↗
PubMed2005

In vitro leakage susceptibility of tracheoesophageal shunt prostheses in the absence and presence of a biofilm.

Although leakage through a tracheoesophageal shunt prosthesis is the main cause of prosthesis failure in a laryngectomy patient, this has never been the subject of in vitro evaluation. The aim of this study was to compare three commercially available voice prostheses by comparison of their in vitro leakage patterns, in absence or presence of a biofilm. To compare in vitro leakage patterns, a model comprised of an artificial throat equipped with a single prosthesis coupled to a water reservoir was developed. By varying the height of the water reservoir, different pressures on the voice prosthesis can be obtained. Both in absence and presence of a biofilm, the Blom Singer voice prosthesis demonstrated the lowest leakage, followed by Groningen Low Resistance. The Provox2 showed significantly the most leakage, however, in presence of a biofilm the leakage of the Provox2 significantly decreased. Regular airflow during biofilm formation significantly increased leakage through the Provox2. Out of 746 clinical replacements, Provox2 showed 76% and Groningen Low Resistance 57% replacements due to leakage. The model used in this study showed significant differences in leakage of the three types of voice prostheses used. Leakage occurred more readily through Provox2 than through Groningen Low Resistance and Blom Singer prostheses, which is in line with clinical observations and enforces the model.

Area Under Curve↗
PubMedDate not supplied

Ex vivo evaluation of ferromagnetism, heating, and artifacts produced by heart valve prostheses exposed to a 1.5-T MR system.

Ex vivo testing techniques were used to determine the ferromagnetic qualities of, presence of heating in, and artifacts produced by 13 different heart valve prostheses exposed to a 1.5-T (64-MHz) magnetic resonance (MR) system. None of the heart valve prostheses showed a measurable deflection in the 1.5-T static magnetic field. Only minimal artifacts were produced during MR imaging with a fast spoiled GRASS (gradient-recalled acquisition in the steady state) pulse sequence. The largest temperature changes measured during a "worst case" MR imaging sequence (estimated average specific absorption rate, 2.5 W/kg; estimated spatial peak specific absorption rate, 7.6 W/kg) were +0.2 degree C with the implant imaged "in air" and +0.3 degrees C with the implant imaged in normal saline. Therefore, MR procedures performed with a 1.5-T (64-MHz) MR system may be performed safely in patients with any of the 13 different heart valve prostheses evaluated in this study.

Absorption↗
PubMed1991

Failure to obtain long-term patency after implantation of fibrous polyurethane prostheses in the carotid arteries of rabbits.

Fibrous polyurethane prostheses were implanted in the carotid arteries and aortae of New Zealand white (NZW) and Chinchilla (CHIN) rabbits. No immediate post-implantation patency was obtained after implantation in the carotid arteries in NZW rabbits. In CHIN rabbits patency up to 1 week was obtained after carotid implantation. Attempts to increase patency rates by administration of 20 mg/kg body weight/day of both dipyridamol (DIP) and acetyl-salicylic acid (ASA) p.o., starting the week before implantation, had an adverse effect; prostheses became occluded within a few hours after implantation. Coagulation tests (Lee and White, Am J Med Sci 145:495-503, 1913) carried out with blood drawn from CHIN rabbits revealed hypercoaguability after administration of either 10 or 20 mg/kg body weight/day of both DIP and ASA compared to pre-medication values. Prostheses implanted in the aortae of both strains remained patent without anti-platelet-aggregation therapy for a 3-month observation period. It is concluded that in the NZW rabbit carotid implantation was not successful due to severe spasmic reactions and that in CHIN rabbits only very short-term patency could be obtained both with and without administration of 10 or 20 mg/kg body weight/day medication DIP and ASA.

Animals↗
PubMed1994

Use of latissimus dorsi flap for reconstruction with prostheses after tumor resection.

Five latissimus dorsi musculocutaneous flaps (LD flap) were used for reconstruction with prostheses after resection of tumors between 1984 and 1991 in our hospital. Bony structures were reconstructed with prostheses and in three cases autoclaved autobone grafts were also needed. The prostheses and adjacent grafts were then wrapped by the LD flaps. Tumor sites included one humerus, two thighs, and two knees. All but one case healed primarily. The sole case of infection was successfully treated with debridement and irrigation. Due to the LD flaps' plentiful blood supply, we believe infection of the prosthetics can be avoided and good clinical results can be achieved using the flap with autoclaved autograft prosthetic composite reconstruction.

Adolescent↗
PubMed1981

Fracture hip prostheses due to welding defects.

Two retrieved Moore type hip prostheses of cast Co-Cr-Mo-alloy were examined after metallic failure. The first case concerns a fatigue fracture in the stem of the prosthesis due to an abrupt change in the cross-sectional area and the presence of inappropriate welding beads in the stem. The abrupt change occurring at a transition from an I-beam into a rectangular profile gives rise to stress concentrations thus increasing change of fatigue crack initiation. The second case is a fracture of the hollow head of the prosthesis through a weld. The two parts of the cast femoral head were incompletely welded. Comparison with similar welds in other femoral heads of prostheses of the same type reveals a poor welding uniformity. Hence, both fractures are associated with the welding process. A critical investigation is needed to find optimal welding conditions for Co-Cr-Mo-alloy prostheses.

Biomechanical Phenomena↗
PubMed1975

[Clinical and experimental experiences of important factors concerning the permanent anchorage of hip-joint-prostheses (author's transl)].

Amomg a lot of conditions influencing the permanent anchorage of hip-joint-prostheses the following factors are very important: form and surface conditions of the material, in addition to a valgus position of the prostheses. The importance of these parameters in changed biomechanics after arthroplastic replacement is confirmed by measurements of spherical shape, morphology of the surface and diameter of the material. Furthermore, the vectorial distribution of weight by the different varus and valgus positions were examined. The experimental results were confirmed by clinical studies on 1407 prostheses during the course of 5 years.

Alloys↗