Femoroacetabular impingement and comparison of radiological indexes: a study on 50 cases

To study the asphericity of femoral head in femoroacetabular impingement using radiological indices such as alpha angle and triangular index, and to compare the alpha angle and triangular index measured in the radiograph and MRI. The study was conducted prospectively from January 2008 to June 2009 on 50 consecutive patients of suspected cam-type FAI hip, reporting to orthopedics outpatients department of Postgraduate Institute of Medical Education and Research. Radiograph of the affected hip was taken, and then alpha angle and triangular index are measured and compared. The mean alpha angle in anteroposterior view was measured as 75° ± 10°, and the mean in lateral view was 740 ± 80. In MRI the mean alpha angle was 79° ± 9°. The mean triangular index in radiograph was 2.9 ± 1.2. In MRI the mean triangular index was 2.6 ± 0.8. Frog-leg lateral view is sufficient for the diagnosis of the cam-type femoroacetabular impingement. But MRI is required in cases, where surgical intervention is planned to rule out other pathological condition and for decision making.