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 847 records · Page 47Linked to original sources
PubMed1992

A histopathologic study of late aseptic loosening of cemented total hip prostheses.

Eighteen patients being treated for revision total hip arthroplasty for aseptic loosening an average of 9.5 years after primary cemented hip arthroplasty were studied. The patients were found to have been symptomatic an average of one year before revision. Review of the roentgenograms at the time of revision revealed that most patients had moderate to severe loosening of the prostheses by Charnley's criteria. These findings were confirmed at surgery. Study of the tissue surrounding the prostheses suggests that the prominent particles were methylmethacrylate "pearls" caused by cement fragmentation. These particles were surrounded by histiocytes that were actively synthesizing and releasing protein. Cement fragmentation and not polyethylene wear may be the major cause of late aseptic loosening of cemented hip prostheses.

Acetabulum↗
PubMedDate not supplied

Healing process of vascular prostheses seeded with venous tissue fragments.

Rapid neointima formation in fabric vascular prostheses seeded with autologous venous tissue fragments was examined. A piece of peripheral vein was minced into small fragments and stirred into 20 ml of saline. This tissue suspension was sieved through the wall of Dacron prostheses. The prostheses implanted in the descending aortae of dogs showed extremely rapid healing of the neointima. Endothelial cells lined the entire luminal surface within 14 days. There was no difference in the healing process between the area near anastomotic sites and the center.

Animals↗
PubMed1991

Failures and complications in 391 consecutively inserted fixed prostheses supported by Brånemark implants in edentulous jaws: a study of treatment from the time of prosthesis placement to the first annual checkup.

A total of 391 edentulous maxillae and mandibles was consecutively treated with routine fixed prostheses, supported by 2,199 implants. The patients were followed for 1 year; the overall success rate was 99.5% and 98.1% for the prostheses and implants, respectively. The number of severe complications was low, but it was possible to identify a significantly higher ratio of problems in the maxillae throughout the observation period than for the mandibles. While many problems occurred in both the maxillae and mandibles, there were also problems more typical for each jaw. Diction and fractures of resin teeth were more common problems in maxillae; cheek and lip biting was a more frequent postinsertion complication in the treatment of mandibles. Most problems were easily resolved, and the retrievability of the prostheses was of great advantage.

Adult↗
PubMed1991

[Structural changes in valve prostheses].

All available prostheses, either mechanical or biological, may undergo structural alterations which are cause of reoperation or death. Some of these complications are common to all valves, whereas some are specific for certain models. Modern mechanical prostheses usually are resistant to structural deterioration, but still thrombogenic thus requiring long-term anticoagulation therapy to avoid thrombotic and thromboembolic episodes, which implies the risk of anticoagulation related hemorrhages. Bioprostheses, on the other hand, present a lower thrombogenicity, however they undergo by definition structural degeneration, especially dystrophic calcification, which is usually cause of reoperation within 8-10 years from implantation. Other prosthetic complications, such as infective endocarditis and fibrous tissue overgrowth, are common to both types of prostheses.

Bioprosthesis↗
PubMed1991

[Experimental premises and 1st experiences in the clinical use of antibacterial vascular prostheses under circumstances of increased risk of suppuration].

It was shown on the basis of laboratory and experimental data that created antibacterial vascular prostheses are marked, on the main, by local bacteriostatic and anticoagulative effect. It was found that heparin concentration of 3 to 500 U per 1 kg collagen causes a hyperadhesive effect on blood platelets and facilitates the formation of the primary thrombocytic thrombus. The free surface energy grows in this case from 34 +/- 0.8 to 66.3 +/- erg/cm2. The optimal thromboresistant effect occurs in heparin content of 1 U per 1 mg collagen. That this choice is correct is confirmed on examination of the inner surface of the prostheses with an electron microscope after being in the blood flow for 45 minutes. Bifurcation and linear antibacterial prostheses were used in 9 patients with a high risk of suppuration verified by cultures of discharge from ulcers and lymph nodes, and the presence of lymphangitis and lymphadenitis. The effect was positive in 8 patients, 2 of them had superficial suppuration of the operative wounds.

Animals↗
PubMed1991

A contribution to our understanding of post-implantation cross-section reduction in the vascular prostheses.

Using theory of linear elasticity, a theoretical model describing the decrease in the flow section of artificial vascular prostheses in response to blood pressure changes in proposed. The model is based on the presumably different deformation behaviours of the vessel and the prosthesis. An increase in the vascular intima thickness in small-calibre prostheses allows greater deformations of their inner surface, closely resembling those observed in the inner surface of the intimal layer of the normal vessel. Results of an analysis presented in the article show that depending on the material properties of the vascular prosthesis there exists such a critical radius of the prosthesis that smaller calibre prostheses, when used, become occluded.

Blood Vessel Prosthesis↗
PubMed1991

[Reoperations in patients with EMIKS and LIKS prostheses].

The frequency, terms, techniques, and the results of reoperations on patients with EMIKS and LIKS prostheses are analysed. In the period between June, 1983 and December, 1989, 994 EMIKS prostheses and 210 LIKS prostheses were implanted in 1,015 patients. In this period 22 reoperations were performed which accounted for 0.62% of patients per year. The reasons for the repeated operations were prosthetic endocarditis in 54.5%, paraprosthetic fistula in 36.4%, and wedging of the disk of a mitral prosthesis in 9.1% of patients. In 81.8% of patients the second operation was conducted within the first year after the first operation. By the 6th postoperative year 96.4 +/- 0.61% of patients did not need a reoperation. This index was 97.1 +/- 0.54% in the group of patients with isolated mitral prosthetics, 95.7 +/- 0.88% in aortic prosthetics, and 94.9 +/- 0.91% in mitro-aortic replacement. Hospital mortality in the group of patients with reoperations was 22.7%.

Heart Valve Prosthesis↗
PubMed1991

Cavitation potential of mechanical heart valve prostheses.

Just like technical check valves, the function of mechanical heart valve prostheses may presumably also lead to cavitation effects during valve closure. Due to the waterhammer effect, cavitation may primarily occur in the mitral position leading to high mechanical loading of the valve itself and of corpuscular blood elements. Ten different types of commercial mechanical heart valves were investigated in the mitral position of a pulsatile mock loop, to detect cavitation thresholds under physiologically similar conditions by cinematographic techniques. Almost all these valve prostheses show cavitation up to a ventricular pressure gradient of 5000 mmHg/s. The threshold depends on valve type and size and is sometimes within the physiological range below 2000 mmHg/s. Visible cavitation bubbles with a diameter of up to 1.8 mm and a collapse time of less than 0.1 ms suggest that vapour cavitation may play an important role for material and blood damage in mechanical heart valve prostheses.

Coronary Circulation↗
PubMedDate not supplied

Resilient acrylic resin template for facial prostheses.

Clay or wax is used extensively as a modeling material for trial facial prostheses. This article describes a technique that uses a resilient acrylic resin as a matrix to lodge the ocular component and wax as the sculpturing medium for orbital prostheses. The technique can be adapted and used for all facial prostheses.

Acrylic Resins↗
PubMed1990

[Speech and prostheses for congenital cleft palate patients in adulthood].

The surgical treatment should be preferred for cleft palate patients in childhood. However, a prosthesis is favorable for some adult patients. The construction of prostheses are rather complicated for patients who require pharyngeal speech aid in addition to anterior prosthesis. Sound prosthodontic rules are valid in designing a speech aid prostheses. Often stability and retention increase is required for these prostheses. Furthermore, the velar and the pharyngeal sections should not interfere with the muscular activity of pharynx and/or tongue movements during speech and deglutition. This article describes the prosthodontic habilitation of congenital cleft palate patients by means of pharyngeal speech aid prosthesis.

Adult↗
PubMed1990

On occlusal forces in dentitions with implant-supported fixed cantilever prostheses.

The main aims of this thesis were (1) to study the functional characteristics of dentitions with mandibular implant-supported fixed cantilever prostheses - IFCP s- occluding with complete dentures, (2) to study in detail the magnitudes and distributions of axially directed closing and chewing forces in such dentitions, (3) to study the influence of number and distribution of occlusal contacts on the magnitude and distribution of closing and chewing forces, (4) to assess the vertical bending moment and the resulting vertical bending stress in the cantilever joints and (5) to find out whether the force distribution over the cantilever beams and the resulting vertical bending stress in the cantilever joint are influenced by the type of prosthetic construction in the opposing jaw. Closing and chewing forces were registered in altogether seventeen subjects by means of miniature strain gauge transducers mounted bilaterally and symmetrically in performed matrices in prosthetic appliances. Four, six or eight transducers, evenly distributed over the tooth-arch, permitted registrations of axially directed occlusal forces in several occluding areas simultaneously. In Papers I-IV, the implant-supported prostheses were installed in the mandible and occluded with complete dentures. In Paper V, group A, the fixture-supported prostheses were installed in the maxilla and occluded with tooth-supported fixed partial dentures whereas in group B, the arrangements were analogous to those in Papers I-IV. All subjects exhibited a rhythmic chewing pattern and preferred one side for chewing although both sides were used. Most chewing sequences were terminated with swallowing with occlusal force development. The mean total forces acting over the tooth-arch varied somewhat between groups and occlusal arrangements but averaged 350 and 170 N for closing and chewing respectively. Closing and chewing forces increased distally along the cantilever beams when occluding with complete dentures and decreased distally when occluding with fixed partial dentures. The distally increasing force distribution pattern could be altered to a distally decreasing force distribution pattern by infraoccluding the second cantilever unit by as little as 100 microns. Calculated vertical bending moments and stresses in the cantilever joints of the preferred chewing sides created by closing and chewing forces were larger in dentitions where the IFCP occluded with a complete denture than in dentitions where the IFCP occluded with a tooth-supported fixed partial denture.

Adult↗
PubMed1990

[Echocardiographic evaluation of mechanical and biological heart valve prostheses].

The complex echocardiography is the method of choice for the non-invasive assessment of patients with prostheses of the cardiac valve. The particular advantages of the method lie in the non-invasiveness, the common ability of repetition, the complete risklessness, the lacking radiation exposure and, what is particularly of importance for the early postoperative phase, the bedside applicability also on the intensive care unit. With regard to potential complications (thrombo-embolism, prosthetic endocarditis) the echocardiography is superior to the invasive examination methods with suspicion to malfunction or leak. The most important prerequisite for an exact interpretation of the findings is the possibility of the comparison with the basis documentation. Moreover, the judgement of prostheses of the cardiac valve demands particular echocardiographic experience, as it in general can be acquired only in a centre. Disturbing echos by valve ring and valve body must be regarded as disadvantage. Disturbances of the cardiac rhythm may simulate defective functions particularly in replacement of the mitral valve with mechanical prostheses.

Bioprosthesis↗
PubMed1990

[Repeat surgery occasioned by the incompetence of the primary tissue in biological prostheses].

The authors analyse the causes of repeated operations on 42 among a group of 157 patients with implanted biological cardiac valve prostheses and a postoperative follow-up period of 3.5 to 13 years. The main cause of dysfunction of biological prostheses is calcification which develops mostly in xenopericardial valves irrespective of their localization. Detachment of the cusps from the frame and their destruction is characteristic of allogeneic prostheses and those formed from the dura mater. Dysfunction of bioprostheses in the tricuspid position develops much later.

Adolescent↗
PubMed1990

[Reflections on a small series of cementless total hip prostheses].

We report on our series of 48 patients with uncemented hip prostheses, with an average follow-up of 3 years. The clinical results, according to the Merle d'Aubigné's classification, are comparable to those obtained with cemented prostheses except for transitory pain, very often localized to the lateral aspect of the thigh, which seems to be correlated with the bone adaptation to the implant. Radiological findings are valuable in the assessment of long-term results with uncemented prostheses. During the operation, it is of utmost importance that the surgeon obtain a very tight fit of the prosthesis into the bone, which must be confirmed on postoperative X-ray. Under such conditions, the radiological appearance remains the same, showing a condensation line outlining the cup and absence of radiolucent lines along the stem. On the other hand, cortical thickening, bony condensation around the tip of the stem and sclerotic lines are the radiological evidence of bone adaptation to the prosthesis. They are not indicative of a less good result. Finally, radiolucent lines wider than 1 millimeter, extending along the stem, or a progressive sinking of the femoral component are the radiological signs of implant instability. In these rare cases, the prognosis may be compromised.

Adolescent↗
PubMedDate not supplied

Endothelialization of vascular prostheses by transplantation of venous tissue fragments.

A method to accelerate the endothelialization of vascular prostheses by seeding venous tissue fragments was developed. A piece of peripheral vein was obtained, chopped into small fragments, and stirred into 20 ml of saline, making a tissue suspension. This suspension was sieved through the wall of a highly porous vascular prosthesis (water porosity: 3,600-4,000). The prostheses, (7 mm ID and 5.7 cm in length) seeded with tissue fragments, were implanted into the thoracic descending aortae of 20 dogs, and were removed from 1 to 371 days after implantation. Ten prostheses, preclotted with fresh blood, were used as controls. In the seeded grafts, an infinite number of endothelial cells migrated and proliferated from the fragments. These had produced numerous capillaries by 5 days after implantation that had reached and opened onto the luminal surface of the prosthesis. From these openings, numerous endothelial cells spread out and formed colonies. With the increase in the size of the colonies, the inner surface was completely endothelialized within 5 weeks. This quick neointimal formation by seeding venous tissue fragments might be applicable to several artificial organs.

Animals↗
PubMed1990

Intraocular silicone prostheses in a dog and a horse with corneal lacerations.

Intraocular silicone prostheses were implanted in the eyes of a horse and a dog with traumatic corneal lacerations and protrusion of intraocular contents. Several months after surgery, the horse and dog were tolerating the intraocular prostheses, and the appearance was cosmetically acceptable. This contradicts earlier reports that have cited corneal disease as a contraindication for implantation of intraocular silicone prostheses.

Animals↗
PubMed1990

Estimation of shear stress-related blood damage in heart valve prostheses--in vitro comparison of 25 aortic valves.

The hemodynamics of heart valve prostheses can be reproducibly investigated in vitro within circulatory mock loops. By measuring the downstream velocity and shear stress fields the shear stresses which are clinically responsible for damage to platelets and red blood cells can be determined. The mechanisms of damage and the effects of shear stresses on blood corpuscles were investigated by Wurzinger et al. at the Aerodynamics Institute of the RWTH Aachen. In the present study, the above data are incorporated into a mathematical correlation, which serves as a basic model for the estimation of blood damage. This mathematical model was applied to in vitro investigations of 25 different aortic valve prostheses. The results were compared to clinical findings. In most cases agreement was good, indicating that this model may be directly applied to the clinical situation. This new method facilitates the estimation of clinically expected blood damage from in vitro measurements. It may be useful for the development and evaluation of new valve prostheses. By comparative evaluation of different valve types it also provides additional information to help the implanting surgeon select the optimum valve for his patient.

Aortic Valve↗
PubMed1989

[Clinical experience with silastic middle-ear prostheses].

The authors made clinical tests of silastic prostheses of the middle ear, type PORP, TORP and piston. They used 29 X PORP, 26 X TORP and 21 pistons. They did not reveal any signs of tissue intolerance to Silastic MDX 44-516, which is used for making prostheses. They achieved satisfactory anatomical and functional results. They recorded an auditory gain in more than half the patients (early: PORP 97%, TORP 73%, piston 52%; plasty transplants of ossicles obtained from subjects who died accidentallyĕ For preserfic Council of the Ministry of Health, Czech Socialist Republic, recommended, based on the clinical tests, the manufacture of silastic prostheses of the middle ear.

Audiometry↗