Robinson DJ, et al. - Researchers design this work to assess whether the femoral head-neck alpha angle could be reliably measured using ultrasound. Compare with computed tomography (CT), ultrasound has good sensitivity and good negative predictive value in calculation of the femoral head-neck alpha angle but with low specificity. In symptomatic patients, ultrasound measurement of the alpha angle can provide objective evidence of cam-type femoroacetabular impingement and can lead patients to more established imaging techniques where appropriate.