SINGLE-PICTURE X-RAY-ANALYSIS FOR MEASURI NG MIGRATION OF HIP ENDOPROSTHESES

A method to determine migration of hip endoprostheses is described. Mi gration is measured by means of standard AP radiographs and therefore can also be evaluated in retrospective studies. Measurement is conduct ed on X-ray studies displayed on a computer screen. Enhancement of bon y structures by application of filters is available. The developed sof tware can be used with common commercially available computers and X-r ay scanners, and does not require special hardware. Several methods to determine accuracy are described. The accuracy of the described metho d is about 1 mm (95% confidence limit), which compares favourably with Other methods, but is less accurate than roentgen stereophotogrammetr y. For other methods, accuracy was not determined adequately. Two year s after implantation, revision within the first 10 years of follow-up can be predicted with a sensitivity and specificity of more than 80%.