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At least 235 records · Page 13Linked to original sources

PubMedDate not supplied

Cost analysis of fabricating implant prostheses.

This prospective study analyzed the time and costs involved in fabricating implant prostheses in private practice and the factors affecting prosthesis design. Esthetic was the most commonly reported factor influencing the decision to use a fixed or removable prosthesis, while cost was infrequently cited. The single-tooth fixed implant required the least time to fabricate and had the lowest clinical fees, while the removable bar/clip prosthesis had the highest fees and demanded the greatest amount of time to fabricate. Single-tooth fixed and individual attachment removable prostheses generated approximately half the hourly income produced by multiple-unit fixed and bar/clip removable implant prostheses, and the individual attachment design had the highest ratio of expenses to income.

Canada↗

PubMed1993

Revision of total hip arthroplasty using the R.M. isoelastic prosthesis.

A cemented revision of failed total hip arthroplasty is prone to early mechanical failure. Cementless revision seems to be much more promising. We present our 2 year follow-up of 19 cementless revisions using the R.M. isoelastic stem. During follow-up special attention focused on the restoration of bone stock on the femoral side of the arthroplasty. Bone stock deficiencies encountered during the operation were managed with grafts. Other complications to solve during the procedure were encountered frequently. The average follow-up was 58 months. Rating the results following Merle d'Aubigné and Postel showed very good or good result only in half of the cases, one case needed a revision. Nevertheless good restoration of bone stock was observed in nearly all cases. A greater number of patients should be followed for a longer period of time to establish the exact role of this prosthesis design.

Adult↗

PubMed2004

Morphology of the radial head: a reverse engineering based evaluation using three-dimensional anatomical data of radial bone.

The proximal part of the radius has a complex shape and dimension that cannot be precisely determined by standard roentgenogram for real three-dimensional anatomical shape which is important for prosthesis design. This study presents a method by which computer tomography (CT) images are combined with the reverse engineering technique to obtain and analyse the three-dimensional inner and outer geometry of the proximal radius. The three-dimensional models were reconstructed from CT images obtained from 40 radial bones and approximated with two- and three-dimensional fitting algorithms based on reverse engineering methods. The mean total length of the radius was 240.0 mm [standard deviation (SD) = 17.3]. The radial head in this study is more likely to be circular with an average diameter of 20.5 mm (SD = 1.9). The outer diameter of the radial neck averages 14.7 mm (SD = 1.0). The thickness of the radial head averages 12.9 mm (SD = 1.4). The intramedullary canal diameter of the radial neck averages 7.4 mm (SD = 1.4). The depth of the fossa at the articular surface averages 1.5 mm (SD = 0.4).

Adult↗

PubMedDate not supplied

Success or failure of dental implants? A literature review with treatment considerations.

This study reviews the literature concerning the success or failure of dental implants and provides the general dentist with information to decide whether to recommend dental implant therapy to a patient. The authors conducted an extensive literature search for articles relating to dental implant failure. Metaanalyses and multi-center studies were predominant in the selection. Predictors of dental implant success or failure were gleaned from various articles and presented in the form of text and tables. The main predictors for implant success are the quantity and quality of bone, the patient's age, the dentist's experience, location of implant placement, length of the implant, axial loading, and oral hygiene maintenance. Primary predictors of implant failure are poor bone quality, chronic periodontitis, systemic diseases, smoking, unresolved caries or infection, advanced age, implant location, short implants, acentric loading, an inadequate number of implants, parafunctional habits and absence/loss of implant integration with hard and soft tissues. Inappropriate prosthesis design also may contribute to implant failure.

Age Factors↗

PubMed1990

Keratoprosthesis. II. Results obtained after implantation of 27 dismountable two-piece prostheses. A retrospective, follow-up study.

During the years 1974-1987 a total of 27 two-piece keratoprostheses were implanted in 25 eyes of 22 different patients with bilateral blinding anterior segment disease with no possibility for a successful corneal transplantation. The prosthesis design and the surgical procedures used are described. The healing in and fixation of the prostheses were initially good in all cases, but 9 prostheses were lost or removed because of complications during the postoperative period of observation. The prosthesis retention time was significantly longer than that earlier achieved by the use of a one-piece prosthesis. In 18 of 27 cases a visual acuity of 6/60 or better was obtained. Postoperative complications included necrosis of the tissues covering and supporting the prosthesis, infection around the prosthesis, overgrowth of the surrounding tissues and the development of dense retroprosthetic membranes. Despite the obvious risks, keratoprosthesis surgery in a small number of patients with severe corneal disease represents the only potential hope for a visual rehabilitation, and should therefore be considered.

Adult↗

PubMed1993

Simulation and animation of musculoskeletal joint system.

This paper describes the development of computer-based software for three-dimensional geometric data base of the human musculoskeletal system. Using a computer graphics workstation, a user of the software will interactively display detailed information about the muscles, tendons, ligaments, bone, and joint anatomy. This software will enable a wide range of health care workers to visualize complex physiological data. In addition to geometric and visual realism, this software will include kinematic relationships which allow the calculation and display of the motion and forces of the joints, muscles, and tendons. This will permit a user to interactively move joints or tendons and display the resulting motion of the surrounding tissues, as well as internal reactive forces and joint pressure distribution. A two-dimensional version of this software is currently being used for knee and hip osteotomy preoperative planning, total joint replacement prosthesis design and dimensional selection, and osteochondral allograft sizing and reconstruction using radiographic data.

Computer Simulation↗

PubMedDate not supplied

[Reconstruction prosthesis after upper epiphyseal and diaphyseal resection of the femur for tumor. Results of 16 cases and a biomechanical study].

The authors have treated 16 cases of tumours of the upper end of the femur by resection over at least 12 centimetres and insertion of a massive prosthesis. The tumour was secondary in 9 cases and primary in 7. This treatment was used for metastases where conservative surgery was impossible or had failed. In primary tumours, when the excision was very extensive, the main problem was of stability of the prosthesis and its long-term future. A new type of total massive prosthesis, designed by the authors after biomechanical studies, is described.

Biomechanical Phenomena↗

PubMed2002

Maximizing flexion after total knee arthroplasty: the need and the pitfalls.

Currently available knee prostheses can provide 100 degrees to 110 degrees of knee flexion, which is usually good enough for most daily activities, such as ascending or descending stairs and rising from chairs. Many activities require deep knee flexion, however. In Asian countries, deep knee flexion also is needed for special cultural activities. Preoperative range of motion, surgical technique, prosthesis design, and postoperative rehabilitation are important factors that influence postoperative range of motion.

Arthroplasty, Replacement, Knee↗

PubMed1988

Pathology of prosthetic cardiac valves.

Heart valve prostheses (HVPs) have been inserted for more than 25 years. That period has witnessed a remarkable evolution and growing sophistication in the diagnosis of valvular heart disease--in anesthetic, perfusion, and operative techniques and in the management of the postoperative patient. As a result, operative mortality related to single valve replacement is in the 3-5% range. Also, the quarter century has seen prosthesis design improve and the introduction of new materials used in their manufacture. The net result is that an individual needing a heart valve replacement now has a better chance both of surviving and of enjoying a prolonged life relatively free of complications related to the prosthesis.

Heart Rupture↗

PubMed1984

Amputations and prostheses for the lower limb.

Amputations in the lower limb are now carried out principally in the elderly because of vascular disease. The management and rehabilitation of the amputee is best achieved by a team approach with the close cooperation of the different disciplines. Attention should be paid to the psychological state of the patient who should be encouraged to mobilise as soon as possible. Prosthesis design and manufacture has changed greatly in recent years. Widespread use is now made of lightweight plastic materials. Modern technology is being applied to the design and manufacture of prostheses, with increasing use of modular systems of components.

Aged↗

PubMedDate not supplied

A literature review on the prosthetic treatment of structurally compromised teeth.

PURPOSE: This article presents a review of the literature on biomechanical factors affecting the treatment outcome of prosthetic treatment of structurally compromised dentitions, with the main emphasis on often-compromised endodontically treated teeth. MATERIALS AND METHODS: Articles cited in a MEDLINE/PubMed search were reviewed with a focus on factors influencing the risk for fatigue failures. RESULTS: Technical failures in connection with fixed prosthodontics are often caused by fatigue fractures. The abutments, cement, and reconstruction are all subjected to stress caused by occlusal forces, and fatigue fracture may occur at the weakest point or where the maximum stress occurs. The weakest point is frequently in connection with endodontically treated teeth restored with posts and cores. CONCLUSION: The literature points to nonaxial forces as a risk for fatigue fracture of teeth, cement, and restorative material. Favorable occlusal prosthesis design is probably more important for survival of structurally compromised endodontically treated teeth than is the type of post used.

Biomechanical Phenomena↗

PubMed2000

Design of a surface replacement prosthesis for the proximal interphalangeal joint.

A surface replacement finger joint prosthesis was designed specifically for the proximal interphalangeal joint (PIPJ). The two-piece design consisted of a bi-condylar proximal phalangeal head and a conforming bi-concave middle phalangeal base. The bearing surfaces were designed as close to the original anatomy of the PIPJs as possible, using detailed information obtained from a previous anatomical study of 83 PIPJs by the present authors. Four sizes of prosthesis were designed with maximum head diameters of 7, 8, 9 and 10 mm. Fixation of the joint prosthesis was achieved by an interference fit between the stems of semicircular cross-section and the phalangeal bone shafts. The main considerations for the stem designs were the offset from the centre of rotation, angle of inclination, length, and cross-sectional shape and size. It is proposed that the two components will be made from cross-linked polyethylene (XLPE) because it can be injection moulded to produce the complex shapes of the joint prosthesis. In addition, XLPE against itself has shown comparable wear rates with stainless steel against ultra-high molecular weight polyethylene from previous work by Joyce et al.

Biocompatible Materials↗

PubMedDate not supplied

A prospective study on the maintenance of implant prostheses in private practice.

This study examined the adjustments, repairs, time, and costs required to maintain 69 implant prostheses in private prosthodontic practice for an average of 22 months after placement. For the removable prosthesis design, the most common adjustment was contouring the prosthesis and the most common repair was retentive component replacement. Screw tightening or fracture repair were the most frequently needed modifications for fixed implant prostheses. Each removable implant prosthesis averaged four times as many postplacement adjustments and almost twice as many repairs as did each fixed implant prosthesis, and the mean length of each maintenance appointment was also longer for removable prostheses. Mean repair costs were approximately 60% higher for the removable design.

Adult↗

PubMed2006

Medium-term results of the Scorpio total knee replacement.

We performed a medium-term clinical and radiological analysis of 160 patients (173 knees) who underwent Scorpio total knee arthroplasty between August 1997 and September 2000. Seventeen patients (19 knees) were lost to follow-up and 29 patients (29 knees) died before completing a minimum 5 year follow-up. The mean age of the patients at the time of the operation was 73.5 years and the mean duration of follow-up was 5 years and ten months. At the time of latest follow-up, the mean knee score was 92 and the mean functional score was 65. Overall, 104 knees were rated as excellent, 12 knees as good, 8 knees as fair, and one knee as poor. Thin, incomplete, non-progressive radiolucent lines were noted around eight tibial components and one femoral component. Massive osteolysis in the tibia was observed in one case. Only one patient needed revision of the prosthesis. Our findings suggest that the prosthesis design with a single flexion extension radius is associated with a good medium-term outcome.

Aged↗

PubMedDate not supplied

Fluid dynamics of venous valve closure.

In vitro experiment was performed on a stented bovine jugular vein valve (VV, 14 mm I.D. x 2 cm long) and a stentless bovine jugular vein valve conduit (10 mm I.D. x 6 cm long) in a hydraulic flow loop with a downstream oscillatory pressure source to mimic respiratory changes. Simultaneous measurements were made on the valve opening area, conduit and sinus diameter changes using a specially designed laser optic system. Visualization of flow fields both proximal and distal to the venous valve, and the valve opening area were simultaneously recorded by using two video cameras. Laser Doppler anemometer surveys were made at three cross sections: the valve inlet, the valve exist, and 2 cm downstream of the venous valve to quantity flow reflux at valve closure. The experiment confirmed that the VV is a pressure-operated rather than a flow-driven device and that little or no reflux is needed to close the valve completely. The experiment further demonstrated that the VV sinus expands rapidly against back pressure, a critical character to consider in venous prosthesis design.

Animals↗

PubMed1998

Immediate weightbearing after uncemented total hip arthroplasty.

Radiographic subsidence of the femoral prosthesis and clinical results after unilateral and simultaneous bilateral uncemented total hip arthroplasty were compared. Patients who had bilateral total hip arthroplasty began weight-bearing as tolerated on both lower extremities the day after surgery. Patients who had undergone unilateral total hip arthroplasty were maintained at 10% weightbearing on the operative limb for 6 weeks after surgery. Patients in both groups were matched for age, gender, and weight. Minimal followup was 2 years. There was no difference between the two groups in terms of clinical results. Radiographic assessments were performed immediately after surgery, 6 weeks after surgery, and again at 2 years after surgery. Radiographs were reviewed by a single observer and analyzed with a digitized data recorder. Increased subsidence of the femoral prosthesis within the bilateral group was found at 6 weeks. The mean subsidence of the femoral prosthesis at 6 weeks for the bilateral total hip arthroplasty group was 0.86 mm (range, 0.18-2.60 mm) and for the unilateral group was 0.39 mm (range, 0.07-1.46 mm). However, subsidence occurring between 6 weeks and 2 years averaged 0.50 mm (range, 0.09-1.10 mm) for the bilateral group and 0.54 mm (range, 0.03-0.99 mm) for the unilateral group. This difference was not significant. At the 2-year followup, all femoral prostheses in both groups appeared radiographically stable with evidence of bone ingrowth and no indications of loosening. Thus, immediate weightbearing after bilateral total hip arthroplasty in this study resulted in more initial subsidence (during the first 6 weeks after surgery) of the femoral prosthesis but did not preclude the prosthesis from becoming stable and achieving bone ingrowth. Patients in both groups obtained satisfactory clinical results. Because initial stability and bone ingrowth are factors influenced by prosthesis design, the results of this study may not be applicable to all implants.

Adult↗

PubMed1986

Effects of total knee replacement design on femoral-tibial contact conditions.

Ten fresh knee specimens with prosthetic components inserted were tested in a loading rig. Compressive and shear force were applied to the femur with the tibia held fixed. The location of the femoral-tibial contact points was measured. The contact reaction forces, the shear forces, and the rocking moments transmitted to the tibial component were calculated. The variations in the test conditions were: high and low compressive force, flexion angles of 0 degree, 45 degrees, and 90 degrees, three curvatures of tibial plastic inserts, and the posterior cruciate retained or resected. When the posterior cruciate was retained, the contact points were close to the center of the component; for cruciate resection, the contacts were close to the anterior of the component. The shear forces and rocking moments were higher for cruciate resection, but the contact reaction forces were lower. There is a wide variety of knee prosthesis designs, but the amount of inherent stability between the femoral and tibial surfaces, and whether the posterior cruciate ligament is retained or sacrificed, are two of the most important design variables. This study shows that cruciate resection increases the shear forces and the rocking moments to the tibial components and that additional fixation means may be necessary to compensate. On the other hand, cruciate retention with low conformity gives higher contact forces, which may lead to more wear in the long term. Cruciate sacrificing designs with intercondylar guiding surfaces are a separate category of design and were not considered in this study.

Biomechanical Phenomena↗

PubMed1990

Uncemented press-fit total knee arthroplasty.

Nineteen total knee arthroplasties in 16 patients were performed using a new prosthesis designed specifically for uncemented, press-fit fixation without any provision for tissue ingrowth. This design may be suited for use in patients with juvenile rheumatoid arthritis, postseptic knees, failed total knee arthroplasties with large bone stock deficiencies, and young, active, overweight individuals. Preservation of bone stock is possible because the fixation stems are nails rather than larger cement pegs, removal for revision is easier without cement, sequestration of microbes within cement cannot occur, and bone graft may be continually loaded with this type of prosthesis. Pain relief, discarding crutch support, operative blood loss, and corrective alignment were equivalent to results obtained with cemented arthroplasty. Seventeen of the 18 knees available for review (average follow-up period, 3 years, 7 months; range of follow-up period, 2 years, 10 months to 4 years, 11 months) were pain-free. Range of motion averaged -2 degrees of extension to 101 degrees of flexion. Ambulation was unrestricted and unsupported in the majority of patients. Radiographic evaluation showed the development of increased bone density under the tibial plateau as well as a sclerotic line at the ends of the femoral and tibial stems. This observation gives support to the theory that multiple microtrabecular fractures with healing form a new supportive "subchondral bone plate." There was one incidence of tibial subsidence. Prosthesis migration and loosening were not observed.

Adult↗