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At least 1,657 records · Page 92Linked to original sources
PubMed1999

Analysis of a failed alumina THR ball head.

The favourable properties, on which is based the successful history of the use of alumina in orthopaedic surgery, are due to the tough control made by manufacturers on the whole process from raw materials purity to the quality controls. The minimum requirements of a medical grade alumina are stated from 1981 in ISO 6474 standard. Nevertheless, due to the voluntary character of standards, and lack of national and international laws, it was possible in the past to introduce into the market materials with characteristics not in compliance with the standard ISO 6474. A THR implanted on a fifty years old patient was revised three years after implantation, due to the failure of the alumina ball head. To understand the causes of such an early failure, the fragments of the retrieved ball head were submitted to a series of non destructive and destructive controls. The results show that the poor quality of the design and manufacture of the implant was the origin of the failure.

Aluminum Oxide↗
PubMed2002

Delayed fracture of the ceramic femoral head after trauma.

There are various ways in which a total hip arthroplasty may fail catastrophically. Failure of the ceramic femoral head component is well known and described. It may fail because of trauma, but delayed fracture after trauma has not been described previously. This case report describes this phenomenon and postulates a possible mechanism for this failure.

Arthroplasty, Replacement, Hip↗
PubMed2003

[Percutaneous transhepatic retrieval of an intraoperatively displaced biliary stent].

Biliary stents play an important role in the treatment of jaundice due to malignant and/or benign diseases of the bile duct. Biliary stents are primarily introduced endoscopically whereas the percutaneous transhepatic technique is employed after endoscopic failure. Proximal and distal displacement or migration is a rare complication, but there is a risk of considerable morbidity and mortality, so that the extraction of the prosthesis is recommended in these cases. Again, endoscopic removal is the approach of choice. For stent retrieval multiple techniques have been described, including Dormia basket, special forceps, Fogarty balloon catheter, ball tip catheter and loop catheter. Endoscopic recovery often uses a combination of these techniques reaching a success rate of 90%. However, in patients following hepaticojejunostomy or Bilroth II procedure an endoscopic retrieval cannot be performed for obvious technical reasons. Consequently, percutaneous transhepatic stent removal must be considered. Ensuring a correct technique transhepatic removal is equally successful and safe, thus eliminating the risks of a surgical procedure.

Adult↗
PubMed1990

Microangiopathic hemolytic anemia as the initial manifestation of porcine valve failure.

We compare the findings in a patient whose microangiopathic hemolytic anemia was the initial sign of porcine valvular dysfunction, with those of six other patients with porcine valve failure seen at Tripler Army Medical Center and with those of 12 patients with hemolytic anemia and porcine valve failure whose cases have been reported in the literature. Total bilirubin and serum lactic dehydrogenase were directly related to the degree of anemia in patients with porcine valve dysfunction. Echocardiography confirmed valve dysfunction in only four of eight patients, while cardiac catheterization confirmed valve failure in 16 of 17 patients. Laboratory evidence for hemolysis was minimal in 31 patients who had normal, functioning porcine valves. Microangiopathic hemolytic anemia in the presence of a porcine prosthetic heart valve, and in the absence of other causes, warrants a thorough evaluation to rule out valve dysfunction. Routine laboratory screening for hemolysis may aid the early diagnosis of porcine valve failure.

Anemia, Hemolytic↗
PubMed2004

Results of reoperation for hip dislocation: the big picture.

Hip instability remains a costly complication of primary (3%) and revision (10%) procedures. In those with well-oriented components, instability may be anticipated in about 70% from advancement of the trochanter. Articular reorientation readily is affected by the use of modular cups with elevated rims. This has proven to be an effective strategy both to lessen the likelihood of an initial dislocation after both primary and revision procedures. It has also proven to be an effective strategy to treat the unstable implant, especially if cup orientation has been defined as the primary problem. Larger head sizes in the range of low-friction arthroplasty, such as 32 mm, are not any more stable than 22-mm diameter implants. Anatomic-sized heads as used in bipolar devices are effective in treating established instability in up to 90% of instances. The most popular current option is that of the constrained head/cup articulation. Good short-term results have revealed success in more than 90%. However, the effectiveness is design dependent, and the long-term effectiveness understandably is questioned as reports of mechanical failure begin to emerge.

Arthroplasty, Replacement, Hip↗
PubMed1996

A new technique for determining the denture tooth bond.

Defective bonds between resin teeth and denture base material remain a continuing source of failure. Findings from the limited number of studies on this topic are diminished by the numerous experimental approaches adopted. National and international standard specifications also adopt different methods of specimen preparation and physical straining. A critical appraisal of the various standards is carried out and a new procedure for determining the denture tooth to acrylic resin bond is described. A study using this technique found that physical modification and alginate contamination of the tooth had no significant effect on the bond strength. Ineffectual wax elimination was the main cause of failure.

Acrylic Resins↗
PubMed1995

In-Ceram failure behavior and core-veneer interface quality as influenced by residual infiltration glass.

PURPOSE: Crown and fixed partial denture fabrication using In-Ceram all-ceramic restorative material (Vita Zahnfabrik, Bad Säckingen, Germany) involves the veneering of a glass-infiltrated alumina core with porcelain. The manufacturer instructs that excess infiltration glass be removed from all core surfaces before++ porcelain application; however, meticulous removal may not be practical. This study evaluates the failure behavior of two different types of In-Ceram structures with or without thin layers of excess infiltration glass left on core surfaces. MATERIALS AND METHODS: Two groups of porcelain-veneered incisor crowns were fabricated having either (1) excess infiltration glass removed from the aluminous core (n = 10) or (2) a thin layer (0.1 to 0.3 mm) of excess glass remaining on the core (n = 10). Each crown was loaded on its incisal edge against a flat compression platen at 0.5 mm/min. Two groups of core disks (thickness, 1 mm; radius, 7.5 mm) underwent similar surface treatments; i.e., group A as recommended (n = 15) and group B having excess glass (n = 15). Disks were veneered with porcelain, polished to 1.5 mm, and loaded in biaxial flexure at 0.5 mm/min. All fracture surfaces were analyzed using light microscopy and a select sample were examined using scanning electron microscopy. A simple two-dimensional finite-element model was used to evaluate the stress state at the core-veneer interface of bend samples. RESULTS: Failure loads were significantly higher for crowns having excess glass (Student's t test, P < .004). Weibull moduli were indistinguishable (m = 6.2) between crown groups, consistent with the microscopic impression that they shared a common failure mode. Microscopic evaluation of cross-sectioned crowns showed core-veneer interfaces with less porosity in the presence of excess infiltration glass. Failure loads for the disk groups were indistinguishable (Student's t test, P > .8). Scanning electron microscopic analysis of disk samples revealed that failures originated either at core-veneer interfaces or at lower disk surfaces, consistent with the finite-element analysis. CONCLUSION: Excess infiltration glass on the core surface will not degrade the strength of In-Ceram structures. Central incisor crowns (as tested) were strengthened by excess infiltration glass, but disk samples (stressed differently) were not. Finite-element results suggest that disk failure originates from three possible sources.

Aluminum Oxide↗
PubMed1992

Ossiculoplasty prognosis: the spite method of assessment.

A series of 535 ossiculoplasties were studied to determine statistically significant links between the presence of presenting preoperative clinical features and adverse audiologic results, in order to identify those aspects of case presentation that indicate a good or poor prognosis. Analysis by chi-square testing has identified twelve features classified as surgical, prosthetic, infection, tissue, and eustachian (SPITE) factors. Regrouping the significant features has demonstrated their value in predicting accurately an ossiculoplasty prognosis. The data were used to compare accurately the results of 247 Plastipore procedures and 265 procedures using the Richards Oval-Top hydroxylapatite implant. There was no statistical difference between the series. The use of these factors will permit precise matching of future series to allow accurate comparisons of prostheses, techniques, individual skills, and also surgical philosophies such as the open and closed cholesteatoma management. Most importantly, the SPITE factors permit an accurate preoperative individual assessment when counseling the patient as to the likelihood of success or failure of a proposed ossiculoplasty.

Aged↗
PubMed1994

Posteromedial tibial polyethylene failure in total knee replacements.

This report details 16 cases of focal posteromedial tibial polyethylene wear and failure after total knee arthroplasty. This wear phenomenon was associated with an external rotatory subluxation of the tibial component relative to the femoral component. Failure occurred in ten Miller Galante 1, three Porous Coated Anatomic, two Kinematic, and one Press-Fit Condylar knee designs at a mean time of 45 months from their implantation. With this type of failure, there did not seem to be a relationship with metal type, fixation, polyethylene manufacturing method, or polyethylene thickness. A relatively flat design of the tibial articular surface was common to all of these components. In certain patients this articular design may allow excessive component translation, which leads to polyethylene deformity, wear, and subluxation. Some methods for preventing this failure mode are reported here.

Aged↗
PubMed1998

Kinematic posterior cruciate ligament-retaining total knee replacements. A 10-year survivorship study of 445 arthroplasties.

Survival was tested in 445 primary Kinematic knee replacements performed between January 1981 and December 1990. Three criteria were applied to indicate failure: 1) revision or recommended revision, 2) presence of moderate to severe pain or revision, and 3) lost to follow-up or revision. Using these three criteria, the survival rate at 10 years was 96%, 78%, and 69%, respectively. At last follow-up examination, 84% of knees had good or excellent Bristol knee scores with mean range of motion 100 degrees. Overall, 11 knees (2.5%) have been revised and 27 cases (6%) were graded as failures due to presence of moderate to severe pain at the time of the last evaluation. These results indicate that the posterior cruciate ligament-retaining Kinematic prosthesis provides satisfactory function and survival up to 10 years.

Arthritis, Rheumatoid↗