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At least 271 records · Page 15Linked to original sources
PubMed2006

Composite mesh repair of a large paraesophageal hiatal hernia.

We describe the first experience in Italy with a new pre-cut composite polytetrafluoroethylene (PTFE)/expanded PTFE (ePTFE) prosthesis designed for the hiatal region. A 78-year-old female patient with a large paraesophageal hiatal hernia with migration of the left transverse colon inside the hiatal defect (type IV hernia) received laparoscopic repair by means of the composite V-shaped mesh. The procedure was completed laparoscopically and a partial fundoplication was performed. A favorable outcome was assessed by barium swallow radiograms performed on postoperative day 7. A complete resolution of the symptoms was noted at follow-up 1 month postoperatively. This report confirms the feasibility, effectiveness, and added advantages of the composite V-shaped mesh in tension-free repair of a large hiatal hernia.

Aged↗
PubMed2000

Evaluation of interarch space for implant restorations in edentulous patients: a laboratory technique.

This article describes a laboratory procedure for the visual evaluation of interarch space and its effect on implant prosthesis design. The method is applicable to patients presenting with completely edentulous arches. Silicone impression material is used to form a resilient cast and an external mold from an existing denture. The denture is duplicated using autopolymerizing acrylic resin. The duplicate denture and resilient cast are mounted on an articulator. Spatial relationships of anatomic landmarks can be evaluated, and a quantitative evaluation of available space can be made. The duplicate denture can also be used as a surgical template to direct implant placement. Reference tables are provided to serve as guidelines in the correlation between available space and minimum space required for various implant-assisted restorations.

Acrylic Resins↗
PubMed2003

Total wrist arthroplasty with Destot prostheses in patients with posttraumatic arthritis.

PURPOSE: To analyze the functional and radiologic results after Destot arthroplasty, a wrist prosthesis designed for posttraumatic arthritis, and to define the indications for the use of the implant. METHODS: Using the Meuli point score system, 28 Destot total-wrist arthroplasties in 25 patients with stage 2 or 3 scaphoid nonunion advanced collapse and scapholunate advanced collapse were evaluated for 12 to 96 months after surgery. RESULTS: The overall ratings of the study group were excellent in 17 cases, good in 6, fair in 1, and poor in 4. Eighty-four percent showed improved range of motion and grip strength. Four patients experienced postoperative complications. No imbalance or dislocation was noted after surgery. CONCLUSIONS: The Destot implant seems to be a good solution to restore functional range of motion after posttraumatic wrist arthritis when arthrodesis is required by nonmanual laborers older than 50 years of age.

Arthritis↗
PubMed2006

Femoral rollback of cruciate-retaining and posterior-stabilized total knee replacements: in vivo fluoroscopic analysis during activities of daily living.

Restoration of the physiological flexor/extensor mechanism at the knee in terms of appropriate muscular lever arms, proper required quadriceps force, and suitable patellofemoral compressive force, is fundamental for the success of total knee replacement. Therefore, measurements of anteroposterior translation of the femoral component over the tibial base-plate against joint flexion during daily living activities are essential for the assessment of the in vivo performance of current prosthesis designs. Patients treated with posterior stabilized and cruciate retaining prostheses with excellent clinical scores were evaluated during stair climbing, sitting and rising from a chair, and step up and down, using a three-dimensional pose reconstruction technique based on videofluoroscopy. The posterior stabilized patients experienced a fairly consistent and physiological rollback specific of each motor task, demonstrating proper function of the spine-cam mechanism. Rollback was somehow inconsistent among subjects in the cruciate retaining group, accompanied with a smaller range of knee flexion. In this group, more posterior locations of the condyles correlated significantly with higher clinical and functional scores. Articular surface conformity restores physiological rollback in the presence of a spine-cam mechanism, but not coherently in the presence of the posterior cruciate ligament.

Activities of Daily Living↗
PubMed1995

Hydroxyapatite-coated hip prostheses. Early results from an international study.

A hydroxyapatite-coated hip prosthesis designed to stimulate proximal femoral stress transfer was studied in 222 patients undergoing primary total hip arthroplasty with a minimum followup of 2 years. The femoral component was a roughened titanium alloy with a 50-mu coating of hydroxyapatite applied to the proximal third. A proximal press-fit technique was applied with distal femoral over-reaming as standard procedure. The hydroxyapatite-coated acetabulum was of hemispherical design. Analysis of the clinical results showed a mean Merle D'Aubigné score of 16.7 points at 6 months and 17.4 points at 2 years. Mild residual thigh pain of unknown origin was reported in 3.6% of patients at 2 years. Radiographic evaluation showed complete acetabular and proximal femoral osseointegration without any loosening. No radiolucency or reactive line formation was observed around the hydroxyapatite-coated areas of the prostheses. Femoral bone densification occurred at the coated-uncoated transition zone (54%); 4% to 6% of cases showed cortical hypertrophy at the uncoated area of the stem. Reactive lines were seen around the distal stem in 52% of patients after 2 years. The clinical outcome was excellent, and the radiographic data pointed mainly to proximal femoral stress transfer.

Adult↗
PubMed1987

Inherent laxity in total knee prostheses.

The anterior-posterior and rotatory laxities of 14 total knee prosthesis designs were measured in a loading rig with compressive, shear, and torque loads representative of physiologic loads. The measured laxities covered a wide range, both greater and smaller than that of the anatomic knee. This range was mainly due to the curvature or flatness of the plastic tibial surface and conformity with the femoral component. Pressure patterns showed the corresponding contact track and area on the tibial surfaces. It is proposed that for normal function, the laxity of the device should complement the remaining anatomic structures to produce a combined laxity resembling that of the normal knee. Excessive prosthetic laxity will lead to the risk of instability, soft tissue attenuation, edge-loading on components, and high contact stresses on the plastic. Inadequate prosthetic laxity may lead to altered kinematics and excessive stresses at the interface, running the risk of long-term loosening. The authors show the laxities of many currently used devices, providing important background information for assessing the role intrinsic prosthetic constraint might play in total joint performance in clinical analyses.

Biomechanical Phenomena↗
PubMed1983

Results of total knee arthroplasty with a non-constrained prosthesis.

A non-constrained total knee prosthesis designed at St. Luc Hospital, Montreal, has been used there since 1977. The geometry of its femoral component simulates the normal anatomy of the knee and the flat articular surfaces of its tibial component allow unconstrained rotation, rolling, and sliding motion, as dictated by the retained cruciate ligaments. The results achieved in the first 107 consecutive arthroplasties (in eighty-three patients) were evaluated after a minimum follow-up of two years (range, two to four and one-half years). Using the knee-rating system of The Hospital for Special Surgery, 91 per cent of the knees had an excellent or good result. In ninety-eight knees the preoperative pain was adequately relieved and the limb was in physiological valgus alignment. One hundred and four knees had normal medial-lateral stability in extension, and three were unstable. The average postoperative arc of flexion was 102.8 degrees. Sixty-three patients (76 per cent) could ascend and descend stairs normally, and gait studies on seventeen of these patients (twenty-three involved knees) demonstrated that the flexion arc of the knee while the patients were ascending and descending stairs was the same as that of normal controls. Three knees had a deep wound infection and one knee had aseptic loosening of the femoral component.

Adult↗
PubMed2003

The performance of gamma- and EtO-sterilised UHMWPE acetabular cups tested under severe simulator conditions. Part 2: wear particle characteristics with isolation protocols.

Ultra-high molecular-weight polyethylene (UHMWPE) has been used in total joint replacement for the last three decades. Despite the recent advancements in prosthesis design, the wear of UHMWPE remains a serious clinical problem; the release of wear debris may induce osteolysis and implant loosening. Controlling the quality of the polyethylene is essential to improve its wear resistance and any potential adverse effect caused by processing, manufacturing or sterilisation should be avoided. To evaluate the influence of the sterilisation method (gamma-irradiation and ethylene oxide (EtO)-treatment) and third-body particles, gamma- and EtO-sterilised UHMWPE acetabular cups were tested against CoCrMo femoral heads in a hip joint simulator run for 2.5million cycles in bovine calf serum in the presence of third-body polymethylmethacrylate (PMMA) particles. A method not requiring ultra-centrifugation has been proposed for the isolation of polyethylene wear debris from the serum lubricant. SEM analysis allowed debris shape and morphology to be determined, and the wear mechanism operating in this study to be hypothesised. The morphological features of the wear debris were in agreement with clinical findings, enabling the hip simulator function to be validated. Micro-Raman spectroscopy coupled to PLS analysis showed that the mechanical friction during in vitro tests induced significant crystallinity changes in all the cups. The most significant changes were observed for the EtO-sterilised cups, which showed the highest weight loss.

Animals↗
PubMedDate not supplied

Kinematics and constraint of total elbow arthroplasty.

Total elbow arthroplasty has been a valuable procedure for patients with rheumatoid arthritis, posttraumatic arthritis, osteoarthritis, and failed reconstructive procedures of the elbow. Many of the original designs were simple hinge joints, in which intrinsic complete constraint of the articulation predictably resulted in failure by loosening. Subsequently, the development of elbow prostheses diverged into 2 general types: loose hinge (linked) and resurfacing (unlinked). The main concern with such development is instability, which is attributable to numerous factors including prosthesis design, ligament integrity, and position of the prosthesis. A series of studies have been performed to examine the intrinsic constraint of various total elbow arthroplasty designs, as well as the joint laxity after implantation in cadaveric specimens.

Arthroplasty, Replacement↗
PubMed1984

Bileaflet, tilting disc and porcine aortic valve substitutes: in vivo hydrodynamic characteristics.

The St. Jude valve is a new bileaflet disc cardiac valve prosthesis designed to avoid some of the hemodynamic drawbacks of other prostheses. The in vivo flow characteristics of the St. Jude aortic valve (42 patients) were studied and compared with those of three other commonly used aortic prostheses. Björk-Shiley (12 patients), Hancock (27 patients) and Carpentier-Edwards (15 patients). The studies, performed 24 to 48 hours after surgery, included measurements at rest and during augmentation of valve flow by infusion of isoproterenol. The mean performance index for valves of all sizes is higher for the St. Jude than for either porcine valve, both at rest and during isoproterenol infusion (p less than 0.05). Utilizing data both at rest and with isoproterenol, the relation of valve flow and mean systolic gradient for each size of St. Jude valve (19 to 25 mm) indicates the occurrence of small increases in gradient (5.3 to 8.2 mm Hg) as valve flow increases, ranging from 161 to 436 ml/systolic X min. A direct comparison of valve flow and gradient data for all size 25 and 23 mm prostheses at rest indicates a tendency for a lower mean systolic gradient in both mechanical valves than in either porcine valve (p = 0.07). With isoproterenol augmentation of valve flow in 25 mm valves, the gradient is less (p less than 0.05), and the effective orifice area and performance index are larger (p less than 0.05) for the St. Jude than for either porcine valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Multi-factorial retainer design analysis of posterior resin-bonded fixed partial dentures: a finite element study.

OBJECTIVES: Biomechanical aspects related to prosthesis design of RBFPD have been proposed as the predominant contributor to unpredictable clinical retention. The aim of this study was to investigate the biomechanics of multiple posterior retainer designs and their interactions using three-dimensional finite element analysis. METHODS: To understand the interactions among the retainer design factors, three values of retainer thicknesses (1.2, 0.8 and 0.4mm), heights (100, 75 and 50% of the distance from 2mm above the CEJ to the occlusal surface) and angle of the axial surface extensions (150, 180 and 210 degrees ) were selected as the design parameters. Twenty-seven RBFPD FE models with three retainer-design parameters were created by image processing, contour stacking, and mapping mesh procedures. The maximum principal and von Mises stresses in remaining tooth and prosthesis, respectively, were recorded in 54 FE analyses (27 FE models with axial and lateral occlusal loadings). RESULTS: The simulated results showed that the averaged stress values of the remaining tooth and prosthesis decreased with greater retainer thickness and height as a result of increasing prosthesis stiffness and maximizing of the bonding area between the enamel and the retainer, respectively. However, no significant stress differences were found according to the angle of the retainer extension because stress transmission was concentrated at the connectors. CONCLUSIONS: The stress elevation rate (termed as VSR-stress elevation by decreasing one unit volume of the remaining tooth) addresses that the height was the most influential factor for the remaining tooth structure, followed by retainer thickness and extension angle.

Dental Prosthesis Retention↗
PubMed1985

Long-term results of wear of plastic hip prostheses.

The Oscobal-Daubenspeck hip prosthesis was used in 19 hemiarthroplasties and 38 total hip arthroplasties in 1973-1975 and the 10-year experience is presented. Pain recurred some years after the operation. The reason was wear of the high-density polyethylene prosthesis head, most pronounced in the hemiarthroplasties, resulting in wear-debris synovitis, resorption of bone, and mechanical loosening of the prosthesis. This design of prosthesis should not be used.

Aged↗
PubMed2000

Rotating hinge total knee arthroplasty in severly affected knees.

A consecutive series of 24 knees in 21 patients who received a Finn rotating hinge for primary (nine knees) or revision (15 knees) total knee arthroplasty between August 1993 and January 1997 was reviewed. The average followup was 33 months (range, 21-62 months) for all patients in the study. Seventeen patients (20 knees) were followed up for more than 2 years. Twenty-four knees (21 patients) were categorized according to Knee Society scoring criteria: 37.5% (nine knees) were Category A, 25% (six knees) were Category B, and 37.5% (nine knees) were Category C. Using the Knee Society knee and function scores, clinical and radiographic results were assessed and outcome analysis was determined. The average Knee Society knee score improved from 44 points (range, 5-64 points) before surgery to 83 points (range, 45-95 points) after surgery; the average functional score according to the Knee Society system improved from 10 points (range, 0-35 points) before surgery to 45 points (range, 0-100 points) after surgery. Pain and function markedly improved after surgery. For treatment of the most severely affected knees with compromised bone and ligamentous instability, the Finn total knee replacement appears to be an acceptable option. As a rotating hinge design, the prosthesis at early followup provides excellent pain relief, restoration of walking capacity, and stabilization, without evidence of early mechanical failure.

Adolescent↗
PubMedDate not supplied

Design of the cochlear prosthesis: effects of the flow of current in the implanted ear.

When structures within the temporal bone are stimulated electrically it is desirable to maximize the dynamic range of the stimulus. The maximum dynamic range of electrical stimulus seems to be found when the threshold of stimulation is minimum. The minimum threshold of stimulus is likely to be reached when the electrical current that flow through regions containing excitable cells is maximized. By implanting electrodes throughout the temporal bone, it is possible to apply electrical currents to the ear and to measure the distributions of current flowing within the ear. The results of these measurements demonstrate that when current flow is directed outside the scala tympani, lower thresholds can be obtained. Frequency dependence of the paths of current flow cannot be used to explain the frequency dependence of the frequency-threshold functions measured in animals.

Animals↗
PubMed1993

A prospective comparison of Butel and PCA hip arthroplasty.

We compared two cementless femoral components, the 'isoelastic' Butel stem and the more rigid PCA design, in a randomised, prospective study of 56 patients with a mean follow-up of 4 years (2 to 5). Patients were matched in 28 pairs, and one of each pair was treated with each femoral component. The isoelastic stem gave fewer signs of stress shielding radiologically, but both the Harris hip score and the visual analogue pain scale showed significantly inferior results at the two-year and three-year follow-up. The overall failure rates for the femoral components were 43% for the Butel and 11% for the PCA. These results contrast with those of earlier experimental and clinical studies, in which isoelastic properties appeared to be advantageous. This review emphasises the importance of controlled studies before an altered or new design of prosthesis is released on to the market for general use.

Alloys↗