PubMed · 9771239
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J Chell, P J Livesley. 1998. Which primary total knee replacement?. https://pubmed.ncbi.nlm.nih.gov/9771239/
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The articulating surfaces of CoCrMo alloy wear specimens and retrieved femoral components of artificial total knee joints are subject to uneven wear. A repeatable and reliable measurement method is necessary to evaluate the surface damage. In this study, the surface roughness of CoCrMo alloy specimens subjected to in vitro third-body wear, and retrieved femoral components of knee joints were analyzed using a white light interference surface profilometer. Each third-body wear specimen was divided into a 19x19 grid of 1-mm(2) squares (361 squares) and each femoral condyle of retrieved specimens was divided into two 10x10 grids of 1-mm(2) squares (100 squares). The surface roughness average (Ra) and root mean square roughness (RMS) were measured for each of the squares. The average of all points measured was defined as the true surface roughness mean (TSRM). Measurements were then performed on 40-60 (in vitro specimens) or 30 (retrieved specimens) randomly selected points on each surface and a cumulative average was calculated. The cumulative average surface roughness value from only a few (5-15) measurement points generated large deviations (>40%) from the TSRM, but converged to the TSRM as the number of measurements increased. The number of randomly selected points necessary for the cumulative average roughness to be within 10% of the TSRM was defined as the representative measurement number (RMN). The RMN for the third-body wear specimens (surface area of 573 mm(2)) was 40 points, and the RMN for the retrieved femoral components (surface area of 100 mm(2)) was 20 points. To obtain the cumulative surface roughness average within a desired percentage of the TSRM, it is important to define or experimentally determine the critical minimum number of measurements, RMN. Several types of measurements may be necessary to understand wear and damage on metal components of artificial knee joints. The TSRM represents a consistent and reproducible measure of surface damage, and a starting point to develop appropriate measurement protocols to quantify damage on a specific surface.
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In 1988 we did develop an EDP-System for data collection of daily routine documentation, which allows on the one hand a complete registration and on the other hand only offers entire and plausible data because of the logical program structure. The registered data are saved in a data bank structure as well as in report form for routine documentation. The substitution of routine documentation by such a system essentially depends on the content of interrogation which has to reflect the user's individual indication and operative technique. First doubts about reflection of the high variation of the individual operative technique could be disproved with help of the evaluation of this system of documentation. None of the 200 registered cases had to be documented without the help of the standardized system. The use in a prospective multicenter study for endoprosthesis of the knee was the starting point of the evaluation for the system's efficiency and acceptance. It had been analyzed the expressiveness of the study's documentation. As there was no standard in free dictated operation records the information content seemed to be reduced and with regard to scientific aspects unqualified. The analysis of the EDP-system especially checked three aspects: the general suitability to represent medical facts by standardized evaluation as well as the user's and patient's acceptance. All in all this system is an instrument for standardized daily routine documentation in a clinic which seems able to establish a quality management because of the high data quality, the differentiated registrations of multiple parameters and timeneutral application.