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Results for “Prosthesis Design”

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At least 181 records · Page 10Linked to original sources

PubMed1993

[The bi-contact endoprosthesis system--intermediate results of five years use].

The Bicontact endoprosthesis system has been used in our hospital with almost 1800 patients since 1987 for the treatment of painful destructive conditions of the hip joint, the proportion of traumatic subsequent conditions being 20%. It is a modular system that can be used with the same instruments for cementless and cemented fixation. The medium-term results of follow-up examinations over 5 years show that the biomechanical concept is correct. No aseptic loosening of the stem of prostheses has been reported to date, and it has not been necessary to change the prosthesis design. The femoral pain observed in the case of many other shaft prostheses implanted without cement has not been experienced owing to a particularly high rotational stability of the Bicontact shaft. The good results obtained in the meantime have led to an increase in the range of available models(dysplasia prosthesis). Work is progressing on the development of a revision prosthesis based on the biomechanical fixation principles of the Bicontact system.

Adult↗

PubMedDate not supplied

Semibiologic middle ear prostheses: ossicle cup and ossicle columella.

As a natural step in ossicular reconstruction technique, two semibiologic prostheses are introduced. The prosthesis designed for incus replacement is called the "ossicle cup." A hole is drilled in the body of an incus or head of the malleus, and the synthetic shaft of the ossicle cup is placed into the hole. The synthetic cup fits over the stapes capitulum, forming a joint. The ossicle keeps the synthetic portion from touching the tympanic membrane. The prosthesis designed for total ossicular replacement is called the "ossicle columella." In like manner, the shaft is inserted into a shaped ossicle and placed on the remaining footplate. The ossicle columella has a synthetic footplate that rests on the remaining footplate and provides stability and safety. The adaptability of the semibiologic prostheses solves the problems of a laterally healed tympanic membrane, absent stapes capitulum, remaining footplate crura, low-lying stapes, and retracted malleus. The hearing results of the ossicle cup prosthesis indicate 87% of cases with successful hearing at one year. The ossicle columella results in 71% of cases with successful hearing at one year. To date, the extrusion rate is less than 1%.

Bioprosthesis↗

PubMed2003

Contemporary aspects of penile prosthesis implantation.

PURPOSE: Erectile dysfunction today has a number of effective treatment options. This review was undertaken to examine the contemporary role of penile prosthesis implantation in the treatment of this disorder. MATERIALS AND METHODS: A MEDLINE search was performed on the topic of penile prostheses and implants. Current literature was reviewed with regard to types of penile implants, issues related to prosthesis implantation, results, and patient/partner satisfaction. RESULTS: Mechanical failure rates for early penile prostheses, especially the inflatable type, were unacceptably high. Advances in both prosthesis design and implantation techniques have resulted in increased device survival with 5-year actuarial survival rates free of mechanical failure ranging from 86.2 to 93.6%. Recent reviews of implant recipients show 83 and 85% satisfaction and for partners 70 and 76% satisfaction. CONCLUSIONS: When systemic therapy for erectile dysfunction fails, men have a variety of other options to choose from. Penile prosthesis implantation is an option that is feasible for nearly every man with this disorder. Current device survival rates and patient and partner satisfaction rates are high.

Adult↗

PubMed1989

[What should be the shape of extracardiac conduits?].

Studies of the hemodynamic features of the blood flow in extracardiac conduits allow for a grounded and aimed approach to the prosthesis design. The lack of interrelationship between the duct geometry, the flow pattern, and the heart anatomy is one of the reasons for the existing conduits inadequacy. Here is proposed a confuser conduit model providing a stable uninterrupted flow. Development of a hemodynamically optimal type-size series of conduits would allow one to reduce the incidence of complications resulting from inadequate prosthesis design.

Equipment Design↗

PubMed2002

Prosthetic heart valves with silver-coated sewing cuff fabric: early morphological features in two patients.

BACKGROUND: The current generation of prosthetic heart valves are excellent examples of engineering that work well, for long periods of time. Unfortunately, host-related problems and consequent valve failure continue to occur, including infective endocarditis. St Jude Medical Inc introduced a new model of mechanical heart valve prosthesis with silver-treated fabric to try to reduce the incidence of infective endocarditis. Two cases of failure of this prosthesis, with a clinical diagnosis of infective endocarditis, are presented. MATERIALS AND METHODS: Of the 176 St Jude Medical Silzone-coated prostheses implanted, two were explanted in the first half of 1998. The clinical status of the patients was reviewed, and a detailed gross, histological and stereomicroscopic examination of the prosthetic valves was undertaken. RESULTS: Clinically, both patients developed symptoms of infective endocarditis. The first patient developed features of a stroke and two months later underwent a second valve replacement. The prosthesis showed pannus and thrombus. A paravalvular leak was revealed in the second patient, who underwent a second valve replacement six months after the initial surgery. Blood and tissue cultures were negative in both cases. CONCLUSIONS: The new model St Jude Medical Silzone mechanical heart valve prosthesis, designed to prevent infective endocarditis, was associated with clinical features of endocarditis in these two cases. Significant pannus and thrombus were seen on both prostheses, which likely led to emboli and stroke in the first case. The cause of the paravalvular abscess in the second case has not yet been established. The early failure of these prostheses suggests that patients with this prosthesis be followed up carefully.

Endocarditis, Bacterial↗

PubMed2001

[Biomechanical considerations on shoulder joint prosthesis implantation].

The biomechanical goals of prosthetic reconstruction of the shoulder are to restore the normal anatomy and range of motion, and to recreate the normal soft tissue balance of the static and dynamic stabilizers of the glenohumeral joint. An unconstrained prosthesis design best reproduces the physiological articulation and original anatomy of the shoulder. Humeral head components have been recently developed, which are adaptable to the variable anatomy of the proximal humerus (third generation design). A precise reconstruction of the three dimensional structure of the proximal humerus may lead to an improved functional outcome. However, there is still a lack of biomechanical data to support this concept. The optimal design of the glenoid component remains a challenge for future research. Specific issues including the choice of biomaterials, the optimum shape, radius of curvature, surface area of the articulation, component height and stem design remain under investigation. Although the prosthetic design represents an important factor in the success of glenohumeral arthroplasty, the surgical reconstruction of the soft tissues to recreate the normal soft tissue balance as well as postoperative rehabilitation determine the functional outcome.

Biomechanical Phenomena↗

PubMed2000

[Virtual simulation for optimizing the range of motion in hip alloarthroplasty using an adapted thrust-plate prosthesis model].

The purpose of the present study was to increase the free range of motion in conventional trust-plate prosthesis design and to optimize the trust-plate contact as well as the osteointegration area below the trust-plate. For the first part of the study, the two-dimensional geometry of the osteotomy plane was demonstrated in 25 CT-reconstructed femora after performing a virtual cut at a CCD angle of 135 degrees. In the second part, we constructed a prototype of an anatomic adapted trust-plate prosthesis (A-TPP) with an optimized trust-plate and corpus geometry based on the three-dimensional data of three human cadaveric femurs (age 67-75 years). In the final step, we documented the range of motion with computer-aided movement-mapping and compared the conventional TPP with the A-TPP. The results showed a wide variance in osteotomy geometry in the 12 femurs. With the A-TPP, we were able to obtain a much better fit in the trust plate surface. The movement-mapping showed a much higher range of motion in the A-TPP implant. With the A-TPP, the implant surface area for osteointegration could also be significantly increased.

Adolescent↗

PubMedDate not supplied

Cement- and screw-retained implant-supported prostheses: up to 10 years of follow-up of a new design.

PURPOSE: This retrospective study investigated treatment outcomes over 10 years of a new prosthesis design in implant prosthodontics that uses a combined cement- and screw-retained principle. MATERIALS AND METHODS: The clinical data of 78 implant-supported prostheses were examined. Each prosthesis incorporated at least 1 screw-retained element and 1 or more cement-retained telescopic units. One hundred twenty-four screw-retained and 161 cement-retained abutments were employed. RESULTS: Of the 286 implants placed, 5 were lost prior to prosthetic loading and 4 (1.4%) were lost approximately 14 months after loading. Eight (2.8%) abutment screws were retightened and 1 gold prosthetic screw was replaced after 1,372 days following fracture. No accidental dislodgment of any prosthesis occurred. DISCUSSION: The introduction of a screw retainer into a series of cement retainers permitted the use of weak cement on the telescopic abutments. This facilitated removal when required while preventing accidental dislodgment. Improved equipment and the learning curve decreased the incidence of abutment screw loosening with time. CONCLUSION: The ease of retrievability, allied with the security of seating and excellent appearance, makes the combined screw- and cement-retained prosthesis valuable in implant prosthodontics.

Cementation↗

PubMed1993

The development of a physiological hip prosthesis: evaluation of the strains after implantation of a prototype of hip implant: experiment in a dry femur.

Based upon previous research on the relation between hip prosthesis designs and strain distributions in a proximal femur model, a prototype of a "physiological" hip prosthesis was designed and manufactured. Strain gauge measurements on a dry femur before and after implantation of this prosthesis were made in different loading conditions simulating one-legged stance with and without torsional loading and two-legged stance. The strains in the outer cortex were within 10% of the physiological values along the whole medial side in all measurement conditions.

Biomechanical Phenomena↗

PubMed2006

Penile prosthetic surgery and its role in the treatment of end-stage erectile dysfunction - an update.

The treatment of erectile dysfunction has been revolutionised with the introduction of orally active phosphodiesterase inhibitors which are successful in 70-80% of men. However, there remain a group of men in whom conservative treatment fails and surgical insertion of a penile prosthesis is required. This type of surgery has in the past been associated with technical difficulties and a high complication rate. This has spurred numerous developments in prosthesis design and surgical technique with the field changing at a rapid pace. Perhaps the most significant is the use of antimicrobial coatings on prostheses that have been shown to reduce the infection rate significantly. This review highlights those developments reported in the last 5 years.

Erectile Dysfunction↗

PubMed1989

Complications associated with penile implants used to treat impotence.

The complications associated with a variety of penile prostheses used in the treatment of 302 men with erectile dysfunction are described. Infection of the prostheses resulted in their removal from 11 patients (3.6%), antibiotic therapy and replacement in five men. Mechanical failures required reoperation in 43 men (14.2%); however, recent advances in prosthesis design have reduced this type of malfunction. Adverse psychological reactions prompted removal of the prostheses from two men. Despite these complications, this surgery is remarkably effective.

Adolescent↗

PubMed2005

Metal-on-metal resurfacing versus total hip replacement-the value of a randomized clinical trial.

This article describes a randomized clinical trial in young patients, comparing metal-on-metal cemented resurfacing hip replacement with cemented total hip replacement. The trial was stopped early, mainly because of a high incidence of failure of the cemented resurfacing acetabular component. The results reinforce the importance of clinical trials for evaluating the safety and efficacy of prosthesis designs before being used in a large cohort of patients. Although there may be advantages of resurfacing hip replacement, trials are also required to demonstrate it has a midterm success that reasonably approaches that of total hip replacement.

Adult↗

PubMed1999

Glenoid cancellous bone strength and modulus.

The objectives of this study were to determine the strength and modulus of glenoid cancellous bone, including regional variations. The motivations were: to select a suitable bone substitute for standardized testing of glenoid prosthesis loosening, to assist in shoulder prosthesis design and to provide input data for finite element analyses. Ten glenoids from eight cadavers (mean age, 81) were tested by in situ indentation. Mean strength ranged from 6.7 to 17 MPa for the ten glenoids, the overall mean being 10.3 MPa. Mean E moduli ranged from 67 to 171 MPa for the individual glenoids, the overall mean being 99 MPa. These values are likely at the lower end of what would be expected for normal bone since strength and modulus decrease with age and the available specimens were older. These values may be appropriate for prosthesis design, however, since mechanical properties are reduced in rheumatoid arthritic bone. Regional trends were very similar for modulus and strength. The strongest region was postero-superior. The central column, correlating with the keel position in many glenoid components, was weaker than both the anterior and posterior regions but deeper. A large drop in strength and modulus below the subchondral layer emphasizes the importance of maintaining this layer during prosthetic replacement.

Aged↗

PubMed1986

Revision total knee arthroplasty.

Careful attention to axial alignment, soft tissue balance, and stability will minimize prosthetic failure. In revision arthroplasty a prosthesis designed to replace bone loss with the least constraint possible should be used. In the current series revision of the noninfected failed total knee arthroplasty has provided satisfactory results in 50% to 60% of the patients. We believe that use of the newer implants and instrumentation will improve results markedly.

Adult↗

PubMed2000

Failure of total hip arthroplasty with Boneloc bone cement.

Early failure of Boneloc cemented total hip arthroplasty is well documented. However, information regarding the long term prognosis is scanty. The aim of this study was therefore to assess the long term failure rate of total hip replacement with Boneloc bone cement. Between January 1991 and March 1992, Boneloc bone cement (Polymers Recontructive A/S, Farum, Denmark) was used in 42 consecutive total hip replacements in 42 patients. The average age of the patients was 75 years. There were 25 women and 17 men. The diagnosis at operation was osteoarthritis in all cases. A cemented Muller Taperloc femoral stem was used with a cemented Muller acetabular cup (Biomet, Warsaw, USA). The follow-up time was 9 years. All patients underwent radiographic control the first postoperative year and annually after 1995. To date 21 patients have been revised for aseptic loosening at a mean of 5 years (range: one year to 8 years). Three other patients have definite radiographic evidence of loosening. The overall failure rate is therefore 24/42 = 57%. Our results confirm the previously reported poor results of Boneloc bone cement for hip arthroplasty and support the recommendation of indefinite follow-up for surviving prostheses. New prosthesis designs and new cements should have documentation, including laboratory tests and randomized clinical studies with radiostereometric evaluation. However, the ethical responsibility rests heavily on the shoulders of the clinician to make a correct analysis of the need for a new product before he begins to use it.

Aged↗

PubMed2005

A three-dimensional dynamic finite element model of the prosthetic knee joint: simulation of joint laxity and kinematics.

For testing purposes of prostheses at a preclinical stage, it is very valuable to have a generic modelling tool, which can be used to optimize implant features and to avoid poor designs being launched on to the market. The modelling tool should be fast, efficient, and multi-purpose in nature; a finite element model is well suited to the purpose. The question posed in this study was whether it was possible to develop a mathematically fast and stable dynamic finite element model of a knee joint after total knee arthroplasty that would predict data comparable with published data in terms of (a) laxities and ligament behaviour, and (b) joint kinematics. The soft tissue structures were modelled using a relatively simple, but very stable, composite model consisting of a band reinforced with fibres. Ligament recruitment and balancing was tested with laxity simulations. The tibial and patellar kinematics were simulated during flexion-extension. An implicit mathematical formulation was used. Joint kinematics, joint laxities, and ligament recruitment patterns were predicted realistically. The kinematics were very reproducible and stable during consecutive flexion-extension cycles. Hence, the model is suitable for the evaluation of prosthesis design, prosthesis alignment, ligament behaviour, and surgical parameters with respect to the biomechanical behaviour of the knee.

Arthroplasty, Replacement, Knee↗

PubMed1993

Lightweight prostheses for bilateral below-elbow amputees.

In view of the anticipated activity of the patient and working environment, lightweight prostheses were designed for an adult female, bilateral below-elbow (BE) amputee at NIRTAR to provide the greatest degree of function. The prostheses were fabricated using lightweight materials and new techniques. Depending on the stump length there were two different types of lightweight prostheses designed and successfully used, (1) an endoskeletal BE prosthesis and (2) an exoskeletal BE prosthesis. After periodic follow-up and evaluation the function of the prostheses was found to be most satisfactory. By reducing the weight considerably compared to other available alternatives, it is more likely that the amputee will make use of the prostheses to efficiently perform various activities. The new prosthesis designs may counteract the high rejection rate of old conventional ones and the principle may be applied to the fabrication of all BE prostheses.

Activities of Daily Living↗

PubMed2005

Analysis of wear asymmetry in a series of 94 retrieved polyethylene tibial bearings.

Knee joint kinematics is the focus of a significant amount of experimental study for the purpose of knee prosthesis design and for testing the wear of current and prospective bearing materials. This study reports the wear assessment of a series of 94 explanted tibial bearings of various designs and manufacturers and focuses on the extent to which clinical wear is symmetric in the medial-lateral aspect, or is indicative of a systematic asymmetry that would be informative to the design and testing of knee prostheses or surgical practice. Wear assessment of the series of retrievals indicates that, statistically, there was more clinical wear on the medial side. Patterns of wear varied greatly among individual knees; a majority showed very similar extents of wear on the medial and lateral sides, however there were cases with significantly more wear on one condylar articulation than the other. Evidence of edge loading, whereby the femoral component articulates at the margin of the tibial bearing, was common. It was seen most frequently in the central zone of the medial condylar area, and, like the overall wear, edge loading was significantly more frequent on the medial side of bearings. Total bearing wear was seen to generally increase with time over the 208 months of in vivo duration covered by the retrievals in the study. The medial-lateral asymmetry of the wear does not appear to be significantly dependent on duration, however.

Biocompatible Materials↗