Several techniques exist to estimate polyethylene wear in total hip replacements, using conventional clinical anteroposterior radiographs. Some stages of these techniques rely on subjective measurements by the observer. To eliminate observer subjectivity and thereby improve accuracy and reproducibility, a digital image analysis based algorithm incorporating edge detection techniques has been developed. To test the reliability of the algorithm, total hip components were loaded in a materials testing machine, and x-rayed. A cylindrical wear track was milled into the polyethylene and the preparation again x-rayed. The radiographs were digitized, and the amount of wear was computed using the new algorithm. Results show an average imprecision of only 0.027 mm. in measuring 0.914 mm. of simulated wear, a relative error of 2.96%.
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