Retrieval study

This chapter will explain the setup and methodology used for the field retrieval study. The physical and chemical analysis techniques used to study the oxidation of the tire rubber, along with the data analysis developed to interpret the results, will also be explained. Then, the development of an oven-aging protocol that attempts to reproduce the mechanism and rate of tire field aging will be described. 

In addition to the Ford field-retrieval study, NHTSA has carried out further studies of aging from tires retrieved from Phoenix [8]. Analysis in this chapter will be Umited to tires SUV/Minivan-A, -B, and -C and Large Car-C from the Ford study. Tire sizes and maximum inflation pressures for these tires are reported in Table 34.2. The analysis will focus on extracting accurate rate data from the field data. Of key importance is developing an understanding regarding the sources of variability in field aging. 

The final portion of the GLP surveiUance inspection includes examination of records and reports as described under Parts 58.185, 58.190, and 58.195. To accomphsh this, FDA assesses the fachitys ability to store and retrieve study data, reports, specimens, and so on in a manner that maximizes their integrity and utihty. This must include an overview of how the firm maintains materials such as the raw data and the various specimens that are developed in the course of the study. The investigators must become famihar with the facility s archives regarding their location and accessibility. The individuals responsible for the archives must be identified and FDA must learn whether or not the archive is indexed and if the materials and records that have been transferred and stored elsewhere are appropriately identified. Furthermore, the procedures for adding or removing materials from the archives must be examined and individual test systems are selected randomly to determine that all raw data, specimens, and documents have been retained as required. 

The final portion of the GLP surveillance inspection includes examination of records and reports as described under Parts 58.185, 58.190, and 58.195. To accomplish this, the FDA assesses the facility s ability to store and retrieve study data, reports, specimens, and so on in a manner that maximizes their integrity and utility. This must include an... 

Comparison of Wear Rates in Clinical and Retrieval Studies... 

Willert H.G., and G.H. Buchhom. 1999. Retrieval studies on classic cemented metal-on-metal hip endoprostheses. In METASUL A metal-on-metal bearing. C.B. Rieker, M. Windier, and U. Wyss, Eds. Bern, Switzerland Hans Huber. 

Before 1992 (Peters et al. 1992), osteolysis was generally not noted in the orthopedic knee literature except as isolated case reports. Witiiin the past 10 years, however, there has been increased interest in wear and osteolysis as it relates to knee replacement. Several clinical and retrieval studies related to osteolysis in TKA have been summarized in Table 8.3. 

S. Torgersen and N.R. Gjerdet, Retrieval study of stainless steel and titanium miniplates and screws used in maxillofacial surgery. Journal of Materials Science Materials in Medicine, 5, 256-262 (1994). 

Although this approach is widespread, it is unsatisfactory for a number of reasons. For one, recovery rates tend not to sufficiently account for early enrichments in sets of retrieved compounds. This deficiency can be partially eliminated using cumulative recall curves, which plot the fraction of actives against the number of compounds retrieved [58, 150]. These curves are similar to the receiver operating characteristic (ROC) curves that have become a popular in compound retrieval studies. Truchon and Bayly [151] have carried out a comprehensive analysis ROC curves and related metrics and have developed an optimal, statistically more robust index, the BEDROC (Boltzmann-enhanced discrimination of ROC) metric. 

Abstract The biocompatibihty, biofunctionahty and biostability of a prosthesis, its degradation and the host response are determined throngh an implant retrieval stndy.This chapter focnses on varions aspects of analyzing retrieved biotextile implants. Sample preparation techniques, analytical test methods and different test standards are reviewed. Some precautions and the limitations of implant retrieval studies are also discussed. 

A biotextile retrieval study is the study of a biotextile implant that has been retrieved from an animal or human patient after a certain period of time. In animal trials, retrieval times are prescheduled and coincide with the time of sacrifice of the animal. For human patients this is obviously not possible, and the time of retrieval is unscheduled and occurs either at... 

Standards and animal models for implant retrieval studies... 

As mentioned earlier, biotextile retrieval studies can be carried out in animals (preclinical trials) as well as in human subjects (clinical trials). Retrieval studies using animal models are usually planned studies where the device to be tested is implanted in the animal for a fixed duration after which it is harvested and studied for the desired characteristics. 

Retrieval study samples from human beings are more difficult to obtain and are usually available as a result of an unscheduled reoperation or autopsy, either of which could be due to device failure or to some totally unrelated cause. Implants retrieved at reoperation are generally in a poorer condition since they are often collected in response to emergency surgery where the patient is the primary concern and the preservation and integrity of the biotextile explant is of limited interest. It is therefore mandatory to include with every clinically retrieved sample some explanation... 

Some other examples of animal models that are used in biotextile retrieval studies include implanting hernia repair meshes in the abdomen of piglets and mitral valve replacement in juvenile sheep or calves, and subcutaneous implants of valve materials in young rats for in vivo biocompatibility and calcification studies. 

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