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At least 145 records · Page 8Linked to original sources
PubMed1994

[Studies of sound condition in the reconstructed middle ear with a hydrophone. Initial results].

The acoustic result following reconstruction of the middle ear is often disappointing and unpredictable. Apart from biologic factors, this is due to insufficient knowledge of the mechanism of sound transmission through the operated middle ear. Therefore, temporal bone experiments with simulated middle ear operations were set up to investigate the sound transmission following different prosthesis' designs, materials, etc. We developed a tiny hydrophone which has a frequency range from 100 Hz to 10 kHz in order to measure the sound pressure in the cochlear fluid. By comparing the sound pressure in the inner ear with the sound pressure at the drum membrane, we were able to analyze the transfer function of the manipulated middle ear. First results with different reconstruction techniques, prosthesis' designs and attachments demonstrated the usefulness of this measuring technique for the development of acoustically better middle ear reconstructions.

Bone Conduction↗
PubMed2000

Fixed or removable implant-supported restorations in the edentulous maxilla: literature review.

Among the prosthesis designs used to treat the edentulous maxilla are fixed or removable implant-supported restorations. Since the aesthetic requirements and preoperative situation of each patient varies, controversy exists regarding prostheses' success rates and complications. The purpose of this article is to compare the treatment options and prosthesis designs with their indications and to compare implant and prosthesis success and treatment expense. This objective was accomplished through the review of reports with regard to varying design considerations and factors that influence the decision-making process and treatment outcomes.

Cementation↗
PubMedDate not supplied

[Endoprosthetic replacement of the shoulder joint. Possibilities and their analysis].

Functional and anatomic characteristics of the shoulder girdle are special problems, that have to be solved in the process of using an artificial joint replacement to improve the function of a painful shoulder, which is restricted in movement. Seen from a biomechanical point of view, besides a safe fixation of the prosthesis the stability and kinematic of the artificial joint are of considerable importance for the success of the endoprosthetic treatment. The efforts of meeting these requirements by a respective prosthesis design led to a variety of prosthesis types. This study shows the possibilities for prosthetic replacement of the shoulder joint and comprises an analysis of all systems, which are available on the market, as well as of the patent applications of the past 15 years. The prostheses are listed according to their stability. Relative to the state of destruction of the joint unconstrained prosthesis types with completely free and partially restricted mobility, as well as constrained types of joints are being discussed.

Biomechanical Phenomena↗
PubMed1980

Preliminary report on postoperative results of newly designed stable total knee prosthesis.

A newly designed stable total knee prosthesis was made for the severely destructed knee. This prosthesis was named the Yoshino total knee prosthesis, and is a non-hinged type prosthesis consisting of a vitallium femoral component and a ultra-high molecular weight polyethylene tibial component. Clinical results of 127 Yoshino total knee arthroplasties showed the following characteristics: 1) good stability, and 2) good mobility. Stability was exceptionally good, and the results were the same as the hinged total knee prosthesis.

Adult↗
PubMed1992

Pontic design and localized ridge augmentation in fixed partial denture design.

The endpoint of fixed prosthesis design is an esthetic and functional pontic that is compatible with soft-tissue health. In the posterior segment, where esthetics is not as critical, a sanitary pontic form is most compatible with function and hygiene. In the maxillary anterior region, a properly contoured modified ridge-lap pontic design constructed of glazed porcelain most readily fulfills both the esthetic and physiologic requirements. Although the ovate pontic form may satisfy esthetic demands to a greater degree, this is often at the expense of underlying soft-tissue health. In maxillary edentulous regions, ridge deformities may preclude a good pontic fit and esthetic result and dictate the need for surgical augmentation of the collapsed ridge. Selection of the appropriate surgical procedure and graft material depends on the nature and extent of the defect and availability of donor tissue. The subepithelial graft employing the tunnel approach is appropriate when augmentation in only a labial dimension is necessary. When the employing the trapdoor approach or full thickness gingival onlay graft may be employed. In large defects, sequential grafting procedures may be necessary to achieve the desired result. An esthetic and functional result can be attained through proper execution of an appropriate surgical technique and adherence to the principles of proper pontic design.

Alveolar Ridge Augmentation↗
PubMed2001

Implant versus tooth-implant supported prostheses in the posterior maxilla: a 2-year report.

When implants are used for restoration of a jaw with a residual dentition, the possibility of combining implants with natural abutments may be considered. In a longitudinal comparative study, 26 patients (15 women & 11 men, age 49-84 years) with residual anterior dentitions were treated with two different designs of fixed partial dentures bilaterally in the posterior maxilla. On one side the reconstruction was supported by implants only, while on the contralateral side an implant and a tooth in combination were used. The patients were followed at intervals of 3, 6, 12 and 24 months after loading of the implants. 95 implants were placed, of which 11 non-loaded. A total of 10 implants failed, 7 prior to loading and three within the first three months of service (88.0+/-SE 6.7% cumulative survival for tested implants after two years' follow-up). There was no difference in failure rate for the implants in the two different prosthesis designs. The total mean loss of marginal bone height close to the implants was within acceptable standards, but was more pronounced at the implants not combined with teeth. The results indicate a correlation between the prosthesis design and the loss of marginal bone.

Aged↗
PubMed2000

Optimization of design and surgical positioning of inflatable penile prostheses.

The interaction between the cylinders of an inflatable penile prosthesis (IPP) and the surrounding tissues during IPP-aided erection may result in local elevated stresses. These stresses may reach values that can obstruct penile blood vessels and cause ischemia and/or stimulate nerves around the operation site, thereby inducing sensations of pain. A new numerical model was used to analyze penile stresses postimplantation of different IPP types, in order to optimize prosthesis design and surgical positioning by enabling minimal stress transfer to dorsal blood vessels and nerves. The results suggest that intraluminal pressures should be maintained at low levels (about 80 kPa) while cylinder thickness and stiffness should be kept just high enough (approximately 15% of the radius and 1000 MPa, respectively) to eliminate deleterious cylinder-tissue contact stresses. Smaller prosthetic cylinders, i.e., occupying about 45% of the cavernosal space, may be advantageous in terms of reducing dorsal stresses, but lower penile rigidity should be expected. A significant decrease of dorsal stresses can also be achieved by encouraging the surgeon to position the cylinders toward the lower part of the corpora. The numerical simulations indicate that circular cylinders may allow greater biomechanical compatibility of the IPP with the penis structure than elliptic ones, and this should be a subject for clinical investigations.

Biomechanical Phenomena↗
PubMed2001

A novel low wearing differential hardness, ceramic-on-metal hip joint prosthesis.

Osteolysis and loosening of artificial joints caused by polyethylene wear debris has prompted renewed interest in alternative bearing materials for hip prosthesis designs. Lower wearing metal-on-metal (MOM) and ceramic-on-ceramic prostheses are being used more extensively, and there is considerable interest in further improving on their performance. This study investigated the wear properties and debris morphology of a novel differential hardness ceramic-on-metal (COM) prosthesis, in comparison with MOM articulations in a physiological anatomical hip joint simulator. The COM pairings were found to have wear rates approximately 100-fold lower than the MOM pairings. The MOM pairings showed a higher "bedding in" wear rate (3.09+/-0.46mm(3)/10(6) cycles) in the first million cycles, which then reduced to a steady state wear rate of 1.23+/-0.5mm(3)/10(6) cycles. The wear rate of the COM pairings over the duration of the test was approximately 0.01mm(3)/10(6) cycles with very little wear detected on the surface of the prosthesis components. The wear particles from both articulations were oval to round in shape and in the nanometer size range. After one million cycles the mean maximum diameter of the MOM and COM wear particles were 30+/-2.25 and 17.57+/-1.37nm, respectively. After five million cycles the wear particles were statistically significantly smaller than at one million cycles, 13.9+/-0.72nm for the MOM pairings and 6.11+/-0.40nm for the COM pairings. The wear rates of the MOM prostheses were representative of clinical values. The use of differential hardness COM pairings dramatically reduced the wear rate compared to MOM hip prostheses. The wear particles from the MOM articulation were similar to particles found in retrieved tissues from around MOM prostheses. The extremely low wearing differential hardness COM bearings presented in this study produced far smaller volumetric particle loads compared to MOM prostheses currently used clinically.

Biocompatible Materials↗
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↗
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↗