Automatic assessment of the knee alignment angle on full-limb radiographs

In this study a fully automatic assessment of the knee alignment angles in full-limb radiographs was developed and compared to manual standard of reference measurements in a prospective manner. The data consisted of 28 knees which were gathered from total-leg radiographs of 15 patients (12 males and 3 females with a mean age of 29.4+/-6.9 years) consecutively. For statistical evaluation, a leave-one-out cross-validation was performed. The pattern recognition and consequently the fully automatic assessment were successful in all patients. The automatically measured angles highly correlated with the standard of reference (r=0.989). The mean absolute difference was 0.578 degrees (95% CI: 0.399-0.757 degrees ). 82% of the angles differed less than 1 degrees from the standard of reference, 46% differed less than 0.5 degrees and 31% differed less than 0.2 degrees . The automatic method showed a high agreement between repeated measurements (+0.515 degrees to -0.429 degrees ). The automatic assessment of alignment angles in full-limb radiographs were equal to the manual assessment. No measurement related user interaction was necessary to achieve results.