The aims of this study are to evaluate diagnostic performance of conventional radiographs for wrist fractures using multidetector computerized tomography (MDCT) as a reference standard, to determine prevalence, demographic risk factors including age and sex, and associations among various wrist fractures. A retrospective study was performed, finding a total 455 patients (457 wrists) who had wrist trauma and who had undergone a radiography and subsequent MDCT examination during a 45-month period. The MDCT and radiographs of the patients were reviewed by two radiologists, and a consensus was obtained for the presence of fracture. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of radiographs were calculated using MDCT findings as reference standard. The correlation of both age and sex between the presence of fracture was also analyzed. Of the 455 patients, 223 (49.0 %) had one or more fractures in wrist. A total of 302 (160 patients had one, 50 had two, 10 had three, and 3 had four) fractures were diagnosed in the wrist region. In 457 wrists, MDCT revealed 128 occult fractures missed by radiography. The overall sensitivity, specificity, PPV, and NPV of radiography for the detection of all wrist fractures were 57.8, 99.5, 87.4, and 97.4 %, respectively. The sensitivities of radiography ranged 0-41.2 % for other carpal bone except scaphoid (66 %) fractures and 66.7-80 % for the proximal metacarpus, distal ulna, and radius fractures. Wrist fractures appear to be overlooked on radiography. Further imaging should be warranted for patients who are clinically suspicious for wrist fracture in emergency rooms.
The aim of this study is to compare the wear behavior of X45MoCrV5-3-1 tool steel, used as die material in aluminum extrusion, after single treatment (CrN coating) and duplex treatment (nitriding and CrN coating). Gas nitriding and physical vapor deposition were used as processing techniques and wear tests were carried out at both room and elevated temperatures. A ball-on-disc type tribometer was used for room temperature tests, utilizing Al2O3 ball as counterpart. In order to simulate the wear conditions during extrusion, hot wear tests were carried out at 450• C using block-on-cylinder type tribometer against AA 6080 material. Worn surfaces were studied by microscopy to reveal the wear characteristics of treated steels. It was found that (i) duplex treated steel, having higher friction coecient at room and elevated temperature, had higher wear resistance, (ii) at room temperature single treated steel exhibited higher volume loss than the duplex treated one, (iii) at elevated temperature duplex treated steel revealed a stable coating layer, whereas micro cracks were observed on the surface of the single treated steel.
In this study, commercial hot work tool steels were selected and their wear behaviour under dry sliding condition was investigated after heat treatment applications. In the first stage of the study, solution annealing, quenching, and finally tempering treatments were applied to the experimental steels. All samples were examined by light microscopy after metallographic preparations. In the second stage, hardness values (HRC) of the steels were determined to evaluate the surface resistance to wear. Finally, wear tests were carried out using ‘ball-on-disc’ type tribometer under dry sliding condition and all worn surfaces were characterized using both light and scanning electron microscopy. It is concluded that (i) the steels had typical tempered martensite matrices, (ii) alloy content affected the final microstructure and a finer matrix was obtained due to vanadium addition, (iii) hardness levels directly affected the coefficient of wear of steels, and (iv) worn surfaces exhibited abrasive and adhesive wear tracks.
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