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At least 649 records · Page 36Linked to original sources
PubMed1991

Aseptic loosening of straight- and curved-stem Müller femoral prostheses.

Out of 1099 Müller total hip prostheses with straight and curved stems consecutively implanted between 1980 and 1984, those performed in as homogeneous a group as possible of patients under the age of 70 years were selected for the present retrospective study. There were 158 straight femoral stems with cementless RM acetabular cups, 105 straight stems with cemented Müller acetabular cups, and 158 curved stems with cemented Müller acetabular cups, and their results over a mean follow-up period of 5.8 +/- 1.24 years were compared. Six (3.7%) curved and 5 (1.9%) straight-stem prostheses were exchanged due to aseptic loosening; 26 (16.3%) curved and 54 (20.1%) straight-stem prostheses were "at risk" or loose at the time of follow-up. Survival curves show a worse result for straight stems after 6 years; within a follow-up period of 6-8 years there was significantly more radiological loosening in straight stems than in curved. Loosening in straight stems is assumed to develop mainly as a physiological reaction to the presence of bone cement particles.

Aged↗
PubMed1995

Three-phase bone scintigraphy pattern of loosening in uncemented hip prostheses.

The three-phase bone scintigraphy pattern of loosening in uncemented hip prostheses (UHPs) has not previously been elucidated. We evaluated 28 patients with complicated UHPs who had undergone total hip arthroplasty a very long time previously (range 3-20 years, mean 8.4). All the patients were surgically reviewed: 26 UHPs were found to be loosened and two infected. Nine asymptomatic UHPs were taken as controls. The dynamic phase was invariably negative in both loosened and asymptomatic UHPs while markedly positive in the infected ones. The blood pool phase was positive to various degrees in 16 of the 26 loosened UHPs as well as in the infected UHPs, but was invariably negative in painless replacements. In the bone phase, areas of significantly (discrete to marked) increased uptake were observed in all the loosened prostheses as well as in two-thirds of the asymptomatic ones. However, the regions of the lesser trochanter and/or tip and/or shaft were involved exclusively in the case of the loosened UHPs, and diffuse periprosthetic uptake was found only with loosened or infected implants. Areas of slight methylene diphosphonate (MDP) uptake were found at every periprosthetic site and areas of discrete to marked MDP uptake were commonly found in the acetabulum and/or the greater trochanter with both loosened and painless prostheses and are thus considered to be nonspecific findings.

Bone Cements↗
PubMed1997

A new method for in vivo evaluation of biofilms on surface-modified silicone rubber voice prostheses.

A new method is presented that permits a rapid and accurate in vivo evaluation of biofilm formation on surface-modified silicone rubber voice prostheses. The method is based on partial modification of a Groningen button voice prosthesis by exposing half of the prosthesis to an argon plasma. This results in one side of the prosthesis becoming hydrophilic while leaving the unmodified side hydrophobic as a control. Modified prostheses were placed in patients for an evaluation period of approximately 4 weeks. Despite making the silicone rubber surface hydrophilic, biofilm formation was stimulated when compared to unmodified, hydrophobic silicone rubber. Findings show that biofilm formation on voice prostheses is influenced by hydrophobicity of a silicone rubber surface. The method of partial surface modification used was seen to be suitable for demonstrating such influences regardless of nutrition and other variations in the patient's lifestyle. Microbiological analysis of the biofilms on both sides of the prosthesis valve did not show any changes in microbial composition, with Candida albicans, streptococci and staphylococci being the most commonly isolated strains.

Biofilms↗
PubMed2003

[Metal-on-metal pairs for hip prostheses].

Due to engineering deficiencies as well as problems in the basic material, the first generation of metal-on-metal hip prostheses was not up to standard.Furthermore, unsatisfying clinical results led to a decrease in the use of these prostheses.Nevertheless, there were several cases which demonstrated good results in long-term clinical outcome. After distinct improvements in manufacturing and materials, metal-on-metal prostheses have made a come back. This second generation, which are known mainly under the names METASUL and SIKOMET,have been in clinical use for up to 10 years and the good results found in biomechanical set ups seem to be confirmed in clinical trials. However, a possible disadvantage of this second generation of metal-on-metal hip prostheses might be the production of large amounts of particulate wear debris in the nanometer size range. Whether the great number of small size particles with an extended metal surface and the possible distribution of these particles in the body have biological effects on the cells and tissues (such as allergic or toxic reactions) remains unknown. Among the tribological problems, there is currently a discussion on the possible inflammatory effect of these metal particles, which might play a crucial role in longterm, systemic reactions of the body to metal particles.

Biomechanical Phenomena↗
PubMed2006

["Bionic" arm prostheses. State of the art in research and development].

BACKGROUND: A new generation of arm prostheses is being developed worldwide. These so-called bionic prostheses are intended to offer additional functions, such as sensory feedback, extended range of possible movement, intuitive movement control as far as possible, and a more natural cosmetic appearance. STATE OF THE ART IN RESEARCH AND DEVELOPMENT: In recent years, prosthetic components with much enhanced performance have been developed for use at various levels of the upper limb. Artificial hands that allow for additional grips are are being tested in clinical settings. Innovative methods of signal acquisition and communication with the patient are being intensively researched. CONCLUSION: Several patients have been provided with prototypes of new arm prostheses. At the moment, the results are limited by the restricted communication between patient and prosthesis. However, we can expect the options for prosthesis control to be extended in the near future.

Arm↗
PubMed1998

Gasless videoendoscopic implantation of aortobifemoral vascular prostheses via transperitoneal versus extraperitoneal approach in an animal model.

BACKGROUND: The goal of this acute experimental study was to demonstrate the practicability and reproducibility of aortobifemoral bifurcational prosthesis implantations via either a transperitoneal or extraperitoneal approach using gasless videoendoscopic instrumentation. The endoscopically sutured end-to-side aortic anastomoses were also examined for fluid tightness. METHODS: Eighteen of the 20 domestic pigs in this experimental study received aortobifemoral vascular prostheses in a gasless videoendoscopic procedure. Bursting pressures and leakage (ml/min) were compared for the endoscopically sutured aortic end-to-side anastomoses versus those sutured in conventional techniques using 6-h-old porcine aortas and 6-mm prostheses. RESULTS: The surgical procedures averaged 4 h for the transperitoneal approach (n = 9) and 4.5 h for the extraperitoneal approach (n = 9). However, these times were significantly reduced with increasing routine. Average aortic occlusion times were 1 h for the transperitoneal approach and 1 h 15 min for the extraperitoneal approach; the average iliacofemoral occlusion time ranged from 1 h 45 min with the transperitoneal approach to 1 h 15 min with the extra-peritoneal approach, depending on which side was involved: There were no significant differences in in vitro bursting pressure or leakage amounts between endoscopic and conventionally sutured aortic end-to-side anastomoses. CONCLUSIONS: Gasless videoendoscopic implantation of aortobifemoral vascular prostheses in animal subjects is both practicable and reproducible using either a transperitoneal or extraperitoneal approach. The extraperitoneal approach has proven advantages over the transperitoneal approach. The in vitro fluid tightness achieved with endoscopically sutured aortic end-to-side anastomoses is comparable to conventionally sutured anastomoses.

Anastomosis, Surgical↗
PubMed2005

Effect of flexion angle on coronal laxity in patients with mobile-bearing total knee arthroplasty prostheses.

Proper soft tissue tension is one of the important factors in mobile-bearing total knee arthroplasty (TKA). We evaluated varus/valgus laxities, particularly at flexion, which is a key factor in reducing the risk of subluxation and dislocation of bearings to assess the effect that the flexion angle and the presence or absence of the posterior cruciate ligament (PCL) have on laxity in patients with low-contact stress (LCS) prostheses of the PCL-retaining (24 patients, 24 knees) and PCL-sacrificing (24 patients, 24 knees) type designs during extension and flexion. Both types of prosthesis had about 4 degrees laxity at extension and 3 degrees at flexion. PCL-retaining prostheses had significantly less laxity at flexion than at extension (P = 0.0004 in varus, P = 0.0043 in valgus). For good clinical outcomes following TKA, 3 degrees-4 degrees laxity in the varus and valgus orientations is recommended. In addition, the PCL might be involved in flexion and could affect varus/valgus laxity in PCL-retaining prostheses.

Aged↗
PubMed2005

[Metallic condylar head prostheses to replace the temporomandibular joint].

BACKGROUND: Up to now the results after condylar reconstruction of the mandible have been regarded as less than satisfactory. PURPOSE: Functional and aesthetic long-term results after condylar head resection in traumatic and tumour cases with or without replacement by a metallic condylar head prosthesis were compared in a retrospective study. PATIENTS AND METHODS: From 1980 to 2001, 23 temporomandibular joints of 19 patients were reconstructed with metallic condylar head prostheses. The resected region, the contralateral joint, facial and masticatory muscles and the dental system were clinically and radiographically monitored for a mean period of 4 years and 9 months. Seven patients who underwent condylar resection without substitution were observed over an average follow-up time of 7 years and 11 months. RESULTS: Patients who underwent condylar resection without substitution reported more trouble with eating and speaking for a long time. TMJ endoprostheses preserved facial symmetry better. Maximum mandibular opening as well as lateral and protrusive excursions were slightly reduced in comparison with both unaffected controls and patients who underwent condylar resection without substitution. In this study bilateral condylar prostheses exhibited the same functional and aesthetic results as unilateral arthroplasty. CONCLUSIONS: Metallic condylar head prostheses originally developed for temporary replacement worked in some cases as long-term joint replacement but were not able to reach the total functional quality of natural temporomandibular joints.

Bone Plates↗
PubMed1999

Impregnated polyester arterial prostheses: performance and prospects.

Impregnated polyester arterial prostheses have gained wide acceptance by most vascular surgery teams, probably because these prostheses are easy to use, without any preclotting. We offer here a synthesis of the main studies that have appraised the experimental and clinical performance of these prostheses, and we delineate their major prospects.

Animals↗
PubMed1975

Ball valve prostheses: current appraisal of late results.

Advanced actuarial techniques are used to analyze late results in 912 patients who had isolated mitral or aortic valve replacement with ball valve prostheses from 1965 to 1974. Experience with noncloth-covered and cloth-covered valves is compared in terms of late survival, rate of thromboembolic complications and reoperation and the influence of anticoagulation. The cloth-covered prostheses have substantially reduced the incidence of emboli after mitral valve replacement (1.9 vs. 6 emboli per 100 patient years) and have thus far eliminated emboli after aortic valve replacement in patients receiving warfarin. Patients with a cloth-covered aortic valve who did not receive warfarin had nine emboli per 100 patient years. The safety of cloth-covered valves is clearly enhanced by warfarin therapy; the efficacy of anti-platelet drugs is still uncertain. Strut cloth wear was found at reoperation in 10 patients. This should be prevented in the new model 2400 composite strut ("track") valve by a narrow metal track on the inner surface of each strut. The substantial recent reductions in operative mortality and in prosthesis-related complications pose important questions regarding timing of operations and selection of prostheses. These decisions must be individualized for each patient on the basis of a thorough analysis of late results using modern statistical methods.

Aortic Valve↗
PubMed1989

Maternal and fetal sequelae of anticoagulation during pregnancy in patients with mechanical heart valve prostheses.

Previous reports indicate an increased risk of thrombotic and embolic events in patients with mechanical heart valve prostheses during pregnancy. We prospectively followed 50 pregnancies in 49 patients with 62 cardiac prostheses from presentation at the antenatal clinic through the remainder of the pregnancy. Of the 60 mechanical prostheses, 39 were Medtronic-Hall, 7 St. Jude Medical, 7 Starr-Edwards and 7 Björk-Shiley. Forty-three patients were in New York Heart Association functional class I or II and 6 were in functional class III or IV. Forty-five patients were in sinus rhythm and 4 had chronic atrial fibrillation. All patients received warfarin during the first and second trimesters. Forty-one pregnancies proceeded beyond 28 weeks. In 23 of these (group I) warfarin was replaced with heparin at 36 weeks gestation. In the remaining 18 (group II) warfarin was not substituted owing to premature onset of labor. The target prothrombin ratio (international normalized ratio) in patients receiving warfarin was 2.0 to 2.5. The partial thromboplastin time was maintained at 1.5 to 2.5 times the control value in patients receiving heparin. Eleven patients received dipyridamole plus warfarin for the duration of pregnancy. There were no maternal thromboembolic complications or deaths associated with pregnancy. Antepartum hemorrhage occurred in 1 patient at 35 weeks gestation. One patient (group I) experienced peripartum hemorrhage. All patients were hemodynamically stable before delivery, but 2 developed pulmonary edema during labor. The mean fetal birth weight was low (2.54 +/- 0.98 kg). There were 9 abortions (18%), 7 stillbirths (14%), 2 neonatal deaths (4%) and 2 instances of warfarin embryopathy (4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Comparison of transthoracic and transesophageal color Doppler flow imaging in patients with mechanical prostheses in the mitral valve position.

This study determined the relative value of transthoracic and transesophageal color Doppler flow imaging to systolic flow patterns in the left atrium in different types of mechanical prostheses in the mitral valve. Thirty-nine patients were investigated. Based on clinical findings, 36 of 39 patients had normal prosthetic valve function. Seventeen patients were interrogated within a few days after surgery. Systolic regurgitant jets in the left atrium were absent in all patients by both transthoracic pulsed and color Doppler flow imaging. Using transthoracic continuous wave Doppler, however, jets were demonstrated in 8 of 39 patients (21%). Transesophageal color Doppler flow imaging demonstrated systolic regurgitant jets originating from the prosthesis in all patients. Tilting disc valves showed jets during the entire systole (closure and leakage backflow). Each type of prosthesis generated a specific jet pattern. Pathologic regurgitant jets were crescent-shaped, more extensive and turbulent than jets caused by normal closure and leakage backflow. Thus, transthoracic color Doppler flow imaging is not sensitive for detecting regurgitant jets in mechanical prostheses in the mitral valve. All mechanical prostheses show a specific jet pattern, which should be helpful when transesophageal echocardiography is used to identify pathologic backflow.

Adult↗
PubMed1978

Pregnancy and its complications following cardiac valve prostheses.

Approximately 100 cases of pregnancy in women with cardiac valve prostheses have been reported in the world's medical literature. In most instances, the need for continuous anticoagulation therapy constituted a major concern in the obstetric management of these high-risk pregnancies, particularly since coumarin has been implicated as causing an increased frequency of fetal wastage or birth defects (or both). Of all women who received cardiac valve prostheses at the Mayo Clinic between 1965 and 1975, 23 conceived 40 times after the procedure. Fetal wastage was more than doubled in women receiving coumarin therapy at conception and during the first trimester, as compared with that in women not receiving coumarin therapy. Fetal wastage exceeded 80% in women with multiple-valve prostheses who received coumarin therapy throughout early pregnancy. There were no serious maternal sequelae in any of the women. One infant of a mother receiving anticoagulation therapy had mild nasal hypoplasia, but there were no other congenital anomalies in which coumarin had been previously implicated.

Abnormalities, Drug-Induced↗
PubMed1990

Clinical performance of St. Jude and Medtronic-Hall prostheses: a randomized comparative study.

Newer and improved models of mechanical prostheses are regularly added to surgeons' armamentarium. This study was designed to compare the clinical performance of two of the most used current models of mechanical prostheses. From August 1983 through July 1985, 182 white patients were prospectively randomized to implantation of the St. Jude Medical (95 patients) or Medtronic-Hall (87 patients) prostheses. There were 84 mitral, 85 aortic, and 13 double (mitral and aortic) valve replacements. There were no differences between the two groups with regard to sex distribution, age, functional class, emergency operation, and site of implantation. Early mortality was 3.2% for patients with the St. Jude valve and 5.7% for those with the Medtronic-Hall (p = NS). The survivors were followed for 3 to 5 years (mean, 4.2 +/- 0.6 years; cumulative follow-up, 559 patient-years). Late mortality was 7.1%/patient-year for the St. Jude group and 3.2%/patient-year for the Medtronic-Hall group (p less than 0.05). However, the valve-related mortality was equal (1.4%/patient-year) for both groups. Noncardiac causes accounted for most of the difference between the St. Jude and Medtronic-Hall groups (2.5%/patient-year and 0.4%/patient-year, respectively). There were no cases of thrombotic obstruction, whereas serious systemic thromboembolism occurred at the rate of 1.8%/patient-year (5 episodes) for the St. Jude group and 2.5%/patient-year (7 episodes) for the Medtronic-Hall group (p = not significant); there were another nine episodes of systemic embolism that left no sequelae. Three patients (St. Jude, 2; Medtronic-Hall, 1), all of whom had aortic valve replacement, required reoperation (0.5%/patient-year) because of prosthetic endocarditis, with two deaths.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Mitral valve replacement: randomized trial of St. Jude and Medtronic-Hall prostheses.

To better define the merits of the bileaflet and tilting-disc valves, we prospectively randomized 102 patients (mean age, 57 years; range, 11 to 85 years) to receive either the St. Jude (n = 55) or the Medtronic-Hall (n = 47) mitral valve prosthesis between September 1986 and May 1991. The two groups were not different with respect to preoperative New York Heart Association class, incidence of mitral stenosis and insufficiency, angina score, extent of coronary artery disease, ventricular function, completeness of revascularization, or cross-clamp or bypass time. The hospital mortality (14.5% versus 10.6%, St. Jude versus Medtronic-Hall) and late mortality (7.3% versus 2.1%) were not significantly different. Follow-up was complete in 84 of 89 hospital survivors (94%) with a mean of 26 months (range, 1 to 60 months). The linearized rates of valve-related events and the 3-year actuarial survival demonstrated no significant differences between both cohorts. Comparison of the clinical outcome and echocardiographic parameters obtained at the time of follow-up demonstrated no significant differences between the two prostheses. These data indicate that the Medtronic-Hall and St. Jude mitral prostheses are similar with respect to their rates of valve-related complications and hemodynamic profiles. This study suggests that there is no difference between the St. Jude and Medtronic-Hall prostheses with regard to early clinical performance or hemodynamic results and therefore does not support the preferential selection of either prosthesis.

Adolescent↗
PubMed1995

Comparison of porcine bioprostheses and mechanical prostheses in multiple valve replacement operations.

The performance of porcine bioprostheses and mechanical prostheses in multiple valve replacement operations was evaluated in 494 patients with 553 operations between 1975 and 1992. Porcine bioprostheses were implanted in 351 multiple replacement operations and 202 operations were performed with mechanical prostheses. The mean age of the bioprosthesis group was 59.1 +/- 14.4 years and of the mechanical prostheses group, 55.9 +/- 13.3 years. Concomitant procedures, primarily coronary artery bypass grafting, were performed in 27.4% (96 patients) of the bioprosthesis group and 20.8% (42 patients) of the mechanical prosthesis group (p = not significant [NS]). The early mortality for the bioprosthesis group (BP) was 12.0% (42 patients), whereas for the mechanical prosthesis (MP) group it was 10.9% (22 patients) with no difference (p = NS) for the performance with or without concomitant procedures, primarily coronary artery bypass grafting. The total cumulative follow-up was 1,914 years for BP and 458 years for MP group. The late mortality was different between the groups (p < 0.05), 6.1%/patient-year for BP and 3.7%/patient-year for MP. The difference in late mortality was not different (p = NS) for performance of concomitant procedures and not different (p = NS) for the absence of concomitant procedures, 5.6%/patient-year for BP and 2.2%/patient-year for MP. The freedom from thromboembolism- and antithromboembolic-related hemorrhage favored the biological population (p < 0.05) at 10 years with 79.7% +/- 3.4% for BP and 75.4% +/- 5.0% for MP. The freedom from structural valve deterioration was 100% for MP, whereas for the BP group, 94.7% +/- 1.6% at 5 years and 65.9% +/- 4.3% at 10 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Custom-made nipple-areola prostheses in breast reconstruction.

The nipple-areola prosthesis is a useful temporary or permanent adjunct to breast reconstruction. The commercially available prostheses, however, are unable to reflect the remarkable normal variation in this anatomical feature. We describe the production and use of custom-made prostheses using the remaining nipple-areola complex as a template. Their success in 72 patients has led us to adopt such prostheses as routine in breast reconstruction.

Breast↗
PubMed1982

In vitro closing behaviour of Björk-Shiley, St Jude and Hancock heart valve prostheses in relation to the in vivo recorded aortic valve closure.

To compare prosthetic valve behaviour with that of the natural aortic valve, experiments were performed in vitro as well as in vivo. In a mock circulation system, cinematographic high-speed recordings of the valvular behaviour were made for Björk-Shiley, St Jude and Hancock heart valve prostheses. Simultaneously with the film recording, the aortic flow and the left ventricular and aortic pressures were measured. The closing behaviour of the natural aortic valve was recorded in in vivo experiments following the same measuring technique. Comparison of the film frames with the aortic flow signal revealed that the mechanical prostheses mainly close due to the back flow in the early phase of diastole; they close only for 5% of their cross-sectional area during systolic ejection. The Hancock bioprosthesis closes already for 45% during the flow deceleration phase of systole, which is however significantly less than the corresponding closure of the aortic valve as recorded in vivo (74%). The change in fluid viscosity from 3.10(-3) Ns/m2 to 1.10(-3) Ns/m2 does not affect the closing behaviour of the mechanical prostheses. Reducing the peak value of systolic aortic flow by a factor two decreases the cross-sectional area of the prosthetic valves at peak systole. When the natural aortic valve closing mechanism is applied to a disc-valve prosthesis, a partial (30%) systolic valve closure is found.

Animals↗