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At least 217 records · Page 12Linked to original sources

PubMed1975

[St. George's model of total elbow-joint prosthesis].

The elbow-prosthesis, design St. George, a hinge prosthesis is developed according to the principle of the Low Friction Arthroplasty. Only small resection of the joint is necessary so that in the "second line of defence" a resection-arthroplasty of elbow is possible. The experiences on 44 implanted prosthesis and the results of 37 cases are described. Restriction of motion, pain, instability and ankylosis in case of rheumatiod arthritis and posttraumatic arthrosis were the main indications.

Adult↗

PubMed1998

Impaction allografting with cement for the management of femoral bone loss.

Impaction allografting with cement is the only technique currently available which reverses the diminution of bone stock that occurs in a revision hip arthroplasty, and as such, has great potential. It is particularly appropriate in the younger patient, though older patients may also benefit from the technique. Although the short term results are encouraging, there is a need for further basic science research to determine the optimal graft material and prosthesis design. Refinements in surgical instrumentation and technique will continue to improve the predictability of the clinical result and expand the indications for this important addition to the available options in revision hip arthroplasty.

Age Factors↗

PubMed1996

Procedure to predictably seat multiple, hexed abutments onto endosseous implants: a clinical report.

The use of implants to restore the dentition of partially edentulous patients has increased over the past several years. Optimal esthetic results depend on satisfactory implant placement. Occasionally, implants are placed in less than optimal positions, which may require modification in the prosthesis design and increase the technical difficulty. In these instances, preangled or customized abutments can be used. If more than one of these abutments has to be used, accurate orientation of the hexed components to the implants and each other may be a problem. This clinical report illustrated a simple, inexpensive procedure to transfer the orientation of two or more hexed abutments from a master cast to the mouth. This procedure reduced the time needed to orient the hexed abutments correctly in laboratory and clinical situations. It may also reduce the chances of the patient aspirating or swallowing abutments or screws.

Adult↗

PubMed1998

Rigidly splinted implants in the resorbed maxilla to retain a hinging overdenture: a series of clinical reports for up to 4 years.

STATEMENT OF PROBLEM: The results of the implant overdenture treatment in the maxilla remains inferior to those in the mandible. Different reasons have been alluded to, such as bone quality and quantity, number of implants, as well as the prosthesis design. PURPOSE: To investigate the latter, a new design for the rehabilitation of the resorbed maxillae was set up. MATERIAL AND METHODS: Thirteen patients were selected and provided with four endosseous maxillary implants, splinted with a rigid-cast bar. RESULTS: After a mean loading time of 3 years, six implants were lost; three at abutment and another three shortly after abutment connection, resulting in a cumulative success rate of 88.6% at year 4. A mean marginal bone loss of 0.3 mm was observed within the first year. After the first year, the marginal bone level, the attachment level, and the Periotest scores hardly changed. The main prosthetic complication was the frequent need to renew or to activate the attachments. A strong improvement in patient satisfaction was observed when compared with the old conventional denture. CONCLUSIONS: Within the limits of this study, the outcome confirmed that, on a medium-term base, implant-retained hinging overdentures on four implants were promising.

Adult↗

PubMed1980

The influence of design parameters on calcar stresses following femoral head arthroplasty.

A two-dimensional finite element model (FEM) was used to investigate the effect of various prosthesis design parameters on stresses along the proximal medial aspect of the femur. Strain calculations were compared to reported experimentally measured strains for an intact femur and femur containing a prosthesis in an effort to verify the FEM results. The results of the study indicated that stress levels in the medial aspect of the femur approaching those of the intact femur are possible with a device having an elastic modulus similar to bone. It was found that acrylic bone cement had little effect on stress profiles in the medial aspect when compared to stresses for devices utilizing a direct bone to implant attachment mechanism. It was also found that reduction in implant stem length and elastic modulus of tissue present at the prosthesis--bone interface could be used to increase stresses in the medial aspect; however, their effects were not as dramatic as reducing the elastic modulus of the stem material.

Arthroplasty↗

PubMed1991

[Valve replacement with Macchi prosthesis].

OBJECTIVE: to evaluate the performance of a new ball valve prosthesis. DESIGN: set up of two groups of patients who underwent mitral valve replacement with two different prosthesis: the Macchi prosthesis under evaluation and the well known Starr-Edwards model prosthesis. The chi-square test was used to compare the results. PATIENTS: Patients referred for valvular surgery. INTERVENTIONS: One group of 98 consecutive patients who underwent isolated mitral valve replacement with a Macchi prosthesis from January 1984 to June 30 1986 was compared to a matched group of 49 patients who received a Starr-Edwards prosthesis in the same period of time. Follow-up data were available from 99% patients in the Macchi group 96% in the Starr-Edwards group, with a mean follow-up time of 35.2 (2-57) and 42.9 (4-62) months, respectively. RESULTS: There was no statistical difference in the incidence per 100 patients--month of prosthetic complications--thromboembolism, hemorrhagic events, prosthetic endocarditis, reoperation and mechanical failure. CONCLUSIONS: In our experience and with the available follow-up data the Macchi prosthesis is a good cost effective option when there is indication for a ball valve prosthesis.

Adult↗

PubMed2006

A pilot study in the application of texture relief for digitally designed facial prostheses.

This pilot research aims to identify and assess suitable technologies that may be used to capture, create, and produce fine textures and wrinkles that may be incorporated into computer aided prosthesis design and production techniques. A range of suitable technologies is identified and two methods that may be used in different prosthetic rehabilitation situations are assessed: the creation of three-dimensional relief in a computer aided design environment and the capture of facial anatomy and texture using fringe-projection surface scanning. Patterns were produced using the suitable rapid prototyping processes identified, and these were assessed by a qualified and experienced prosthetist. The suitability of the technologies is commented upon, limitations discussed, and future directions identified.

Computer Simulation↗

PubMed2005

A parametric analysis of fixation post shape in tibial knee prostheses.

A primary concern of total knee replacement (TKR) is aseptic loosening of the tibial component, which may be caused by shielding of mechanical stresses in the bone and may require subsequent revision surgery. A three-dimensional (3D) finite element (FE) model has been developed to study bone and interface stresses for four different tibial prosthesis designs. The model described here incorporates orthotropic and heterogeneous bone properties with physiologically representative loading conditions. Results from this model indicate that stress distribution is affected by the incorporation of anisotropy and spatial variation of bone properties. All bone properties were mapped from published data to characterize their anisotropy and heterogeneity. Physiological loading was incorporated by mapping experimentally determined contact patterns. Convergence testing was performed to ensure model accuracy. In terms of interface forces, a tapered post decreased post shear while slightly increasing post compression compared to a cylindrical post; a post of elliptical cross-section increased post shear and decreased post compression. In terms of cancellous bone stress, tapered and elliptical posts both relieved compression compared to a cylindrical post, while a tapered post also produced increased peripheral stress. The inclusion of medial and lateral pegs in addition to a central fixation post caused localized stress shielding in the periphery of the pegs. In general, all implant models caused a reduction of cancellous bone stress plus high compression beneath the central fixation posts.

Arthroplasty, Replacement, Knee↗

PubMed1993

Minimizing biomechanical overload in implant prostheses: a computerized aid to design.

Implant-supported prostheses must be able to withstand the load capabilities of individual patients to overload them. The gold alloy screw in the Brånemark system is by intention the weakest component. Therefore, if cantilever lengths can be designed so that occlusal forces distributed to individual fixtures are limited to the gold screws' ability to accept them, breakage-free performance may be assured. Models, such as that of Skalak, are capable of developing the required analytical processes to provide the information necessary to achieve this design. Unfortunately, the overt mathematical complexity of the Skalak model has militated against its routine use in the operatory. Its computational aspects are, however, eminently suited to computerization and indeed provide the basis for the computer program that is described in this article. This program is simple to apply clinically and, when used in conjunction with available load parameters of gold screw performance, can provide the clinician with a routine and scientific basis for rational implant prosthesis design.

Bite Force↗

PubMed2000

Initial stability of fully and partially cemented femoral stems.

OBJECTIVE: To test the initial stability of a newly designed partially cemented femoral stem in comparison with a fully cemented conventional stem. DESIGN: An in vitro study to determine the interface motion between femoral stem and bone as a response to loading. BACKGROUND: The aim of the new prosthesis design is a proximal load transfer by a defined partial cement fixation in the proximal femur region and a slim prosthesis stem in the distal region. Before a clinical study can be started, the new stem has to show an initial stability comparable to that of fully cemented prostheses. METHOD: Six paired fresh cadaveric femora were used for the testing of the new partially cemented stem (Option 3000, Mathys Orthopaedics, Bettlach, Switzerland) and a fully cemented stem (Weber Shaft, AlloPro, Baar, Swizerland). Under cyclic loading up to 1600 N hip joint forces, the interface motion between implants and bone was measured at six locations. RESULTS: Both stems showed uncritical interface motions below 43 microm. However, the Option 3000 stem exhibited significantly smaller motions in the proximal region and slightly larger movements in the distal regions than the Weber prosthesis. CONCLUSIONS: The new type of partially cemented stem provided a comparable initial stability to the fully cemented Weber prosthesis. Relevance The high initial stability of the Option 3000 stem justified the clinical use of the new implant. More than 100 implantations in the last three years, with very good preliminary clinical results, support the preclinical findings.

Aged↗

PubMed1982

Effects of a prosthetic tongue on vowel intelligibility and food management in a patient with total glossectomy.

Effects of a prosthetic tongue on vowel intelligibility and food management in a patient who underwent total glossectomy are discussed. Results of the vowel intelligibility study indicate improvement from 48% to 64% on the Vowel Rhyme Test with use of the prosthesis. Analyses of listener confusions suggest that the most significant effects of the prosthesis were reductions in height and antero-posterior confusions, and a proportionately larger number of same category errors. Results further reveal that front vowels appear better preserved than back and central vowels, in both prosthesis and nonprosthesis conditions. Effects of the prosthesis on food management are discussed and consideration is given to future prosthesis design and fabrication.

Deglutition↗

PubMed1997

The talar body prosthesis.

Arthrodesis or talectomy for the treatment of avascular necrosis of the talus or a severe crush fracture of the body of the talus often produces a disability of the ankle and the foot. Therefore, a prosthesis designed to replace the body of the talus and to preserve the function of the ankle and the foot was developed. The prosthesis has a superior curved surface, and the medial and lateral surfaces are inclined for articulation with the tibia and the fibula. The inferior aspect has a concave curved surface at the posterior aspect of the prosthesis to serve as the posterior facet for articulation with the posterior facet of the calcaneus, and there is a convex curved surface at the anterior aspect of the prosthesis for articulation with the middle facet of the calcaneus. The neck and the head of the talus are preserved to allow insertion of the prosthetic stem into bone. A transmedial malleolar approach is used for insertion of the prosthesis. We inserted the talar body prosthesis in sixteen patients - twelve who had avascular necrosis of the talar body and four who had a severe crush fracture of the talar body - between 1974 and 1990. Three patients who were evaluated five years postoperatively had a satisfactory result, and one patient had failure of the prosthesis at eight months because the diameter of the inferior concave curved surface was too small in the region of the posterior facet and had caused erosion of the posterior facet of the calcaneus. All three patients who were evaluated six to ten years postoperatively had a satisfactory result. All except one of the nine patients who were evaluated eleven to fifteen years postoperatively had a satisfactory result; the exceptional patient had an unsatisfactory result because the prosthetic stem had sunk into the talar neck. This patient had a revision thirteen years after the index operation. We believe that the talar body prosthesis can be used to replace the body of a talus with avascular necrosis or a severe crush fracture, thus maintaining the function of the ankle and the foot for a prolonged period.

Adult↗

PubMedDate not supplied

Fracture of the radial head with associated elbow dislocation: results of treatment using a floating radial head prosthesis.

OBJECTIVES: To assess elbow function, complications, and problems of radial head fractures associated with elbow dislocation receiving surgical treatment with a floating prosthesis. DESIGN: Prospective clinical study. SETTING: University Hospital, Orthopaedic Department, Sart Tilman, Liège, Belgium. PATIENTS: Eleven consecutive adult patients were treated with a floating prosthesis for acute radial head fractures associated with elbow dislocation from January 1994 to September 1996. INTERVENTION: The floating radial head prosthesis (Tornier SA, Saint-Ismier, France) was used in all our patients. The implant is in two parts: a radial head made of high-density polyethylene enclosed in a cobalt-chrome cup, which articulates in a semiconstrained manner with the spherical end of a cemented intramedullary stem. The implants were inserted within the first week following the injury (range 2 to 7 days). Three cases also required internal fixation of the coronoid process of the ulna; in one case plate fixation of an olecranon fracture was also performed. MAIN OUTCOME MEASUREMENTS: Patients were assessed by physical examination, a functional rating index (Morrey et al.), and radiographs. The parameters evaluated were motion, stability, pain, and grip strength. Potential complications such as infection, prosthetic failure, or dislocation were investigated. RESULTS: The minimum follow-up time was two years (mean 32 months, range 24 to 56 months). Four patients were considered to have excellent results, four patients were considered to have good results, two patients had fair results, and one patient had a poor result. There were no cases of infection, prosthetic failure, or dislocation. No patient required prosthetic revision. CONCLUSION: The basic principle of maintaining anatomic and physiologic relationships applies when deciding on treatment for radial head fractures with associated elbow dislocation. The loss of lateral osseous support will render the elbow grossly unstable. We believe that a floating prosthesis may be indicated in Mason Type III radial head fractures associated with elbow dislocation, especially in the presence of associated destabilizing fractures. Well-controlled comparative randomized studies will be needed to delineate the optimal treatment for a given situation.

Adult↗

PubMed1992

The influence of lateral release on patello-femoral joint loading in knee arthroplasty. An experimental in vitro study.

Eight fresh, cadaveric knees have been fitted with four different total knee cemented prostheses. Loading forces at the bone implant fixation interface of the patella component have been measured in a knee joint testing rig by four miniaturized force transducers, before and after a lateral release of the patellar retinaculum. The lateral release resulted in a significant local force reduction in the lateral and/or proximal quadrant of the patella resection plane depending on the knee flexion angle, quadriceps tensile force direction, and the patellar prosthesis design.

Humans↗

PubMed1976

Comparison of an EMG-controlled prosthesis and the normal human biceps brachii muscle.

An electromyographically-controlled elbow prosthesis, the "Boston arm", was tested with constant and sinusoidally-modulated inputs under different loading conditions. These tests were used to determine the frequency response of the EMG amplifier, the range of motor speeds, the force-velocity curve, and the frequency response of the prosthesis for cyclic movements. Human biceps muscle was tested during movements under similar loads, and under isometric conditions using random, electrical stimuli to determine its frequency response. The results were compared to evaluate the performance of the prosthesis and contrast its characteristics to those of the physiological system it replaces. The prosthesis minimizes quiescent power drain, and the possibilities of instability or "tremor" by employing velocity control, an overdamped mechanical system, and an electrical "dead-band". These factors limit the ability of the prosthesis to follow rapidly changing inputs or to move rapidly and accurately to a desired position. These comparisons should provide a useful supplement to the usual clinical evaluations, and a starting point for further improvements in prosthesis design.

Arm↗

PubMed2003

The kinematics of fixed- and mobile-bearing total knee arthroplasty.

The success of any total knee arthroplasty (TKA) is influenced by a complex interaction between component geometry and the surrounding soft tissues. The objective of this study was to investigate posterior femoral translation and tibial rotation in a single design posterior-stabilized TKA offering fixed- and mobile-bearing tibial components. Specifically, we examined whether mobile-bearing TKA restores normal knee translation and rotation better than fixed-bearing TKA design. Eleven human knee specimens retrieved postmortem were tested using a robotic system. The translation and rotation of the intact and reconstructed knees were compared. The data indicate that for all knees, posterior femoral translation occurs along the passive path and under muscle loading conditions. Furthermore, increasing flexion angle corresponded with increased internal tibial rotation. Femoral translation and tibial rotation for fixed- and mobile-bearing posterior-stabilized TKAs were similar despite component design variations. However, both arthroplasties only partially restored intact knee translation and rotation. The data presented here may serve as an aid in the development of a rationale for additional improvement in surgical techniques and prosthesis design, so that normal knee function may be restored.

Aged↗

PubMedDate not supplied

Nasopharyngoscopy in palatopharyngeal prosthetic rehabilitation: A preliminary report.

PURPOSE: Prosthetic rehabilitation of speech disorders related to palatopharyngeal dysfunction is accomplished through separation of the oral and nasal cavities. The ability to achieve this separation is challenged when the disorder or defect involves the soft palate. Prosthetic rehabilitation of soft palate disorders and defects has traditionally relied on functional contouring of a prosthesis using functionally adapted impression materials. However, there are limitations to this process, particularly in its inability to visualize function as it relates to the prosthesis in a 3-dimensional space. The aim of this study was to address this limitation by describing outcomes related to the use of nasopharyngoscopy (NPS) for visualization of the velopharyngeal port during assessment and treatment of palatopharyngeal dysfunction. MATERIALS AND METHODS: A retrospective analysis of speech data was conducted for 5 patients who were assessed before treatment, after prosthetic intervention using conventional functional impression techniques, and after prosthetic intervention using NPS. Nasalance and velopharyngeal orifice area outcome measurements were collected for each patient at clinically predetermined intervals. Perceptual assessment of speech samples was performed as well. RESULTS: Improvements in speech function were observed for all patients after treatment with a prosthesis designed via a conventional functional impression technique; however, no patient showed normal values for nasalance or velopharyngeal orifice area. With the use of NPS to adjust the wax impression-derived prosthesis, both nasalance and velopharyngeal orifice area measurements for all patients were within normal limits. Similarly, perceptual judgment of speech found that normal resonance balance was obtained after use of NPS. CONCLUSION: The addition of NPS into prosthetic treatment for palatopharyngeal disorders shows promise for improved speech results.

Adolescent↗

PubMed1981

The correction of knee alignment in 225 consecutive total condylar knee replacements.

Two hundred twenty-five consecutive total knee replacements were reviewed radiographically to determine final alignment of the leg and accuracy of component placement. Of the 126 knees that were in varus preoperatively, only one knee was found to be in varus after knee replacement. Eighty-nine percent of the knees were found to be in 7 degrees +/- 5 degrees of valgus postoperation, while 7 degrees were in greater than 12 degrees valgus, 4 percent were in neutral position. Severe instability in the mediolateral plane was noted preoperatively in 62 knees in this series. Correction of more than 15 percent of deformity was necessary in 34 varus knee and 15 valgus knees. However, there has been no failure in the series attributable to instability in the mediolateral plane. Anteroposterior stability is controlled by the prosthesis design.

Aged↗