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° (95% CI: 0.399–0.757°). 82% of the angles differed less than 1° from the standard of reference, 46% differed less than 0.5° and 31% differed less than 0.2°. The automatic method showed a high agreement between repeated measurements (+0.515° to −0.429°).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.