In vivo intraocular lens failure.
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Female↗
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Results for “Prosthesis Failure”
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Indwelling acoustic sensor for early detection of total artificial heart failure.
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Cardiac Output↗
Femorodistal vein bypass graft stenoses.
Eighty femorodistal in situ vein bypass grafts have been evaluated at 3-monthly intervals clinically, with ankle:brachial pressure indices (ABI), by intravenous digital subtraction angiography (IV DSA) and by Duplex scanning. Five grafts (6 per cent) failed in the perioperative period. Nineteen (25 per cent) of the remaining 75 grafts subsequently developed stenoses on IV DSA during the first 12 months. All angiographic stenoses were detected by Duplex scanning using velocity ratio criteria before the development of symptoms or a measurable decline in ABI, i.e. while non-haemodynamically significant. This technique involves scanning the entire length of the graft but allows even minor stenoses to be detected and progression of stenoses can be determined. At a mean follow-up of 12 months (3-18 months), four (7 per cent) of the fifty-six grafts without stenoses occluded. Eight (42 per cent) of the nineteen stenosed grafts either occluded or developed symptoms. None of the occluded grafts in this series could be salvaged. Non-haemodynamically significant vein stenoses can be detected non-invasively, occur frequently and are associated with graft failure.
Angiography↗
Survival rate and failure characteristics for two post designs.
The dental records of 638 patients treated with 788 posts and cores were studied to analyze failure rate and failure characteristics for two post designs. Frequency of the technical failures, loss of retention, root fracture, and post fracture were recorded 4 to 5 years after post cementation. There were two types of posts: custom-cast tapered posts and parallel-sided serrated posts. The cumulative failure rate was 15% for 456 tapered posts and 8% for 332 Para-Post posts. Loss of retention was the most frequent reason for failure for both types of posts, whereas root fractures had the most serious consequences, and all resulted in extraction. A significantly higher success rate was recorded for parallel-sided serrated posts, compared with custom-cast posts, regarding the total failure rate and the severity of the failure (p < 0.05).
Dental Abutments↗
Late disassembly of modular acetabular components. A report of two cases.
We report two cases of late disassembly of modular acetabular components, 4 and 5 years after implantation. One was revised immediately after the disassembly and one after 4 months, the latter demonstrating excessive wear of metal and polyethylene. Radiographs showing eccentric displacement of the femoral head in the cup associated with a dark, curved shadow representing the displaced polyethylene insert identify this type of implant failure.
Aged↗
[Tracheoesophageal prostheses].
The AA. report their own experience in the field of tracheoesophageal speech rehabilitation of laryngectomees. In order to get a high rate of successful results, (an accurate selection of patients is of fundamental importance) mainly to identify the physical requirements and the motivational aspects potentially favouring vocal, rehabilitation. The personal technique of tracheoesophageal fistula creation under local anesthesia is illustrated, the procedure generally last 5-10 minutes with minimal tissue trauma and blood loss and is also suitable for outpatients. For the above-mentioned reasons, the AA. prefer to perform the tracheoesophageal puncture as a secondary procedure, i.e., after total laryngectomy, taking into account the many inconveniences related to primary rehabilitation, as reported in literature. Finally, advantages and inconveniences of the various types of prosthetic devices employed are illustrated and the causes of failure are discusses.
Bronchi↗
The Charnley total hip arthroplasty in patients under age 40.
Considering the high morbidity in young individuals, the authors reviewed 73 Charnley total hip arthroplasties in patients under age 40. The average follow-up period was 6.6 years. A total of 22 hips failed. Thirty-one hip arthroplasties were performed in normally ambulatory patients, with nine failures. Forty-two were performed in patients with limited locomotion, with 13 failures. The main cause of failure was loosening requiring revision (ten hips). There was radiologic evidence of progressive loosening in four other hips. Loss of trochanteric fixation required revision of six hips. Activity and rheumatoid disease were major contributing factors. Alternative methods of treatment should be considered in the young patient. When the operation is indicated, the greater trochanter must not be removed. It is hoped that cementless methods of fixation may produce a lower incidence of failure.
Adolescent↗
Comparison of tissues adjacent to different mechanical stress areas from patients with clinically failed implants.
Implants consisting of metallic and polymeric components are used to treat musculoskeletal diseases. At revision surgery, significant wear products maybe recovered from tissues adjacent to failed implants. The failing implant is clinically associated with pain, and radiographic analysis demonstrates deterioration of the bone surrounding the implant. There is concern that areas of high contact stresses and articulating surfaces lead to the generation of wear particles that trigger a biological response that mediates the lysis of bone. This study compares the tissues retrieved from various areas exposed to different mechanical stresses. Tissues were processed for biochemical and immunohistochemical factors (cytokines) responsible for bone resorption. The results from this study showed by both quantitative enzyme linked immunoassay and qualitatively by immunohistology a marked increase in cytokines, interleukin-1 and tumor necrosis factor, in areas of articulation compared to other areas. Evaluation of tissues histochemically demonstrated the presence of fibroblast, macrophages, and multinucleated giant cells. Overall, the results indicate that the generation of wear particles lead to the production of biological mediators responsible for the failure of the implants.
Hip Prosthesis↗
Ha coatings in implant dentistry: hype, hysteria, or clinical reality?
Hydroxylapatite (HA) coatings have shown promise due to the enhanced integration of osseous tissues to coated implant surfaces, particularly in sites where bone quality or quantity is compromised. This promise has resulted in a dramatic increase in clinical utilization of HA-coated implants. In spite of encouraging clinical findings, the long-term stability of the hydroxylapatite/bone interface has been challenged. Microbiologically, the HA-coated implant surface may be more susceptible to the formation of bacterial plaque. Additionally, critical variations exist between implant coatings that may affect long-term survival. Despite such concerns, after eight years of clinical utilization, the hydroxylapatite-coated implant surface has not been shown to be predisposed to increased long-term failure.
Animals↗
[Polyethylene faults as causes for failure in total hip replacement].
The paper deals with polyethylene faults leading to failure in total hip replacement. The material has well known advantages and is widely used but has also significant disadvantages: excessive wear of some cups, delamination and peeling of the bearing surface of the cup, fracture and fragmentation of the cup and inducing adverse biological reactions that might lead to the loosening of the implant. Final modeling of the polyethylene cup, radiation sterilization and biological factors can alter internal structure of the polyethylene and change mechanical properties of the cup with failure of the hip arthroplasty resulting.
Biocompatible Materials↗
Influence of polyethylene creep behavior on wear in total hip arthroplasty.
After total hip arthroplasty (THA), polyethylene acetabular liner creep occurs quickly and serves to increases head-liner contact area and decrease contact pressures. What effect these early changes in contact mechanics will have on the wear behavior of the articulation remains unclear, and hence, selection or modification of polyethylene materials for optimal creep and wear performance is impossible. The objective of this study was to determine the influence of polyethylene creep behavior on volumetric wear and linear creep and wear penetration during simulated gait loading conditions. A finite element model of THA articulation was developed, and simultaneous numerical creep and wear simulation was performed to 10 million gait cycles with three levels of polyethylene creep behavior. Long-term volumetric wear and penetration were surprisingly unaffected by the polyethylene creep behavior due to the competing decrease in contact pressures coupled with increased contact area. In addition, variation in contact mechanics with the creep levels studied was only noteworthy in the initial postoperative period; after 1 million gait cycles, peak contact pressures and areas were within 13% regardless of the creep material behavior selected. Femoral head size had considerable impact on wear and penetration, while liner thickness primarily affected only early penetration. These results suggest that polyethylene creep behavior plays a major role in early penetration, but has little influence on the more important long-term volumetric wear.
Arthroplasty, Replacement, Hip↗
Stability of the bonded lingual wire retainer-a study of the initial bond strength.
Bonded lingual retainers (individually adjusted multistranded wires with one bond site per tooth) are used extensively to maintain the orthodontic treatment result. Failure or loss often leads to a relapse. The bond strength of bonded lingual retainers has not yet been studied in respect of the loads that can be withstood by them through deflection of the interdental archwire region. Furthermore, human anterior teeth have never before been used for a study of this kind. Six different wire/composite combinations were studied (wires: Dentaflex co-axial 0.018", Dentaflex multistranded 0.018", and Respond Dead Soft straight, length 0.0175"; composites: Tetric Flow and Heliosit Orthodontic) by bonding 1 cm lengths of wire to the lingual surfaces of 360 extracted lower anterior teeth. Using an Instron 6025 universal testing machine, vertical shear bond strength tests at the bond site as well as vertical shear bond strength tests and horizontal tensile strength tests were performed. The failure characteristics after failure at maximum force were evaluated by light microscopy, scanning electron microscopy, and morphometry. Most failures were observed at the enamel/composite interface. The selected wires displayed no significant differences; Tetric Flow proved to be the most stable resin; and no enamel tear-outs were observed.
Adhesiveness↗
International multi-centre survivorship analysis of mobile bearing total knee arthroplasty.
We retrospectively reviewed the experience of a large international multi-centre study of primary total knee arthroplasty with mobile bearing design and modifications of the tibial component to allow for bicruciate preservation, posterior cruciate retention, or sacrifice. Twenty-seven surgeons performed 4,743 total knee replacements between 1981 and 1997. Implants inserted were 324 that retained both cruciate ligaments, 2,165 that retained the posterior cruciate, and 2,254 that sacrificed both cruciates. The patella was resurfaced in 2,838 and unresurfaced in 1,905. With failure defined as revision or reoperation for any reason, the overall survivorship was 79% at 16 years' follow-up. Revision occurred in 259 (5.4%) knees out of the entire cohort. The risk adjusted rates of failure were higher in females, younger patients, osteoarthritis, post-traumatic arthritis, and in patients who had a meniscal bearing prosthesis or patellar resurfacing. The most common cause of revision was bearing-related issues including chronic instability, bearing subluxation, bearing dislocation, or bearing wear in 2.3%.
Arthroplasty, Replacement, Knee↗
Wear of high-dose gamma-irradiated polyethylene in total hip replacements.
Between 1971 and 1978, 62 patients underwent total hip replacements (THRs) with high-dose (100 Mrad) gamma-irradiated polyethylene sockets. After a mean follow-up of 17. 3 years (range, 6-23 years), 28 hips in 26 patients were available for radiographic wear measurement. Twenty-three THRs with non-irradiated sockets were used as controls, although all these hips had loosened within 13 years. The rate of linear wear in irradiated sockets was significantly lower throughout the follow-up period (less than 2 years, 0.16 and 0. 38 mm/year; 2-6 years, 0.05 and 0.29 mm/year; more than 6 years, 0. 05 and 0.28 mm/year, respectively; mean, P < 0.0001). This result has demonstrated that high-dose gamma-irradiated, cross-linked polyethylene is a promising articulating material for THRs.
Adult↗
Biological properties of the intervertebral cages made of titanium containing a carbon-carbon composite covered with different polymers.
Intervertebral cages are used in orthopaedics for stabilization of injured lumbar parts of vertebral columns. Our study provides preliminary results of tests of the biological properties of titanium cages with a variously modified carbon/carbon composite (C/C) core. This core was produced from a C/C composite modified by hydrogel materials based on poly(2-hydroxyethyl methacrylate) (HEMA) enriched with 1% collagen or 35% methylmethacrylate or 30% terc-butylmethacrylamide. We evaluated the adhesion of the cells to the tested material coating using an in vitro study of the metabolic activity and cytokine production of the cells (TNF-alpha, IL-8). We studied the biocompatibility of intervertebral cages coated with different copolymers under in vivo condition and in an implantation experiment in the porcine femurs. Both in vitro and in vivo results revealed favourable biotolerance of the use system. Modification of the composite HEMA with the use of collagen seems to have a more positive effect on the new bone tissue formed around the implanted devices than HEMA copolymerized with methylmethacrylate or terc-butylmethacrylamide.
Animals↗
Intramedullary nails with two lag screws.
OBJECTIVE: To investigate the structural integrity of intramedullary nails with two lag screws, and to give guidance to orthopaedic surgeons in the choice of appropriate devices. DESIGN: Alternative designs of the construct are considered, and the use of a slotted upper lag screw insertion hole is analysed. BACKGROUND: Intramedullary fixation devices with a single lag screw have been known to fail at the lag screw insertion hole. Using two lag screws is considered. It has also been proposed to use a slot in the nail for the upper lag screw to prevent the upper lag screw from sticking. METHODS: Bending and torsion load cases are analysed using finite element method. Consideration of both load conditions is essential. RESULTS: The results present the overall stiffness of the assembly, the load sharing between lag screws, and the possibility for cut-out to occur. CONCLUSIONS: While the slot for the upper lag screw might be advantageous with regard to the stresses in the lag screws, it could be detrimental for cut-out occurring adjacent to the lag screws. RELEVANCE: Comparative analyses demonstrate that two lag screws may be advantageous in patients whose cancellous bone quality is good and who impose large loads on the lag screw/nail interface. However, the use of two screws might pre-dispose to failure by cut-out of the lag screws. The addition of a slotted hole for the upper lag screw appears to do nothing significant to reduce the risk of such a failure.
Bone Nails↗
Bone remodelling inside a cemented resurfaced femoral head.
BACKGROUND: Although the short-term performance of modern resurfacing hip arthroplasty is impressive, the long-term performance is still unknown. It is hypothesised that bone remodelling and the resulting changes in stress/strain distribution within the resurfaced femur influence the risk of fixation failure. METHOD: Three-dimensional finite element models and adaptive bone remodelling algorithms have been used to predict long-term changes in bone density following cemented femoral head resurfacing. Applied loading conditions include normal walking and stair climbing. The remodelling simulation was validated by comparing the results of an analysis of a proximal femur implanted with a Charnley femoral component with known clinical data in terms of bone density adaptations. FINDINGS: Resurfacing caused a reduction of strain of 20-70% in the bone underlying the implant as compared to the intact femur, immediately post operative. Elevated strains, ranging between 0.50 and 0.80% strain, were generated post-operatively around the proximal femoral neck regions, indicating a potential risk of neck fracture. However, this strain concentration was considerably reduced after bone remodelling. After remodelling, bone resorption of 60-90% was observed in the bone underlying the implant. Reduction in bone density of 5-47% occurred in the lateral femoral head. Bone apposition was observed in the proximal-medial cortex, around the inferior edge of the implant. Hardly any changes in bone density occurred in the distal neck or the femoral diaphysis. INTERPRETATION: Although resurfacing has produced encouraging clinical results, bone remodelling within the femoral head might be a concern for long-term fixation. Regions of strain concentration at the head-neck junction, which may increase the initial risk of femoral neck fracture, are reduced with bone remodelling. In order to reduce this risk of femoral neck fracture, patients should avoid activities which induce high loading of the hip during the early rehabilitation period after surgery.
Bone Cements↗
Effects of pre-cooling and pre-heating procedures on cement polymerisation and thermal osteonecrosis in cemented hip replacements [Medical Engineering & Physics 25 (2003) 559-64].
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Arthroplasty, Replacement, Hip↗