Florian M. Buck MD, Presenter: Nothing to Disclose

Marco Zanetti MD, Abstract Co-Author: Nothing to Disclose

Juerg Hodler MD, Abstract Co-Author: Research Consultant, Smith & Nephew plc Research Consultant, Bayer AG

Christian W.A. Pfirrmann MD, Abstract Co-Author: Nothing to Disclose

To develop a screening technique for femoroacetabular cam impingement using ultrasound (US).

50 consecutive hips of patients referred for MR arthrography of the hip were prospectively included. 24 women (mean age, 40.1 y; range, 18 – 58 y) and 26 men (mean age, 32.6 y; range, 16 – 59 y). Longitudinal US images of the anterior and anterosuperior contour of the femoral neck were obtained. The shape of the femoral head and neck was characterized measuring the alpha angle and beta angle by two independent and blinded radiologists using an adapted measurement method for US. Qualitative criteria included the presence of an osseous bump at the femoral head-neck junction and the presence of eccentricity of the femoral head. MR arthrography of the hip served as reference standard.

36 patients had cam impingement deformity at MR imaging. Regression analysis showed a significant (p<0.001) positive linear association (Pearson correlation coefficient, 0.891) between the values measured on MR and US. Anterior alpha angle (MR/US mean: 52.6°/64.8°; SD: 9.8°/ SD: 12.5°; range: 35°-80°/ 31°-89°). Anterior beta angle (MR/US mean: 69.3°/72.9°; SD: 13.1°/15.7°; range, 40°-100°/38°-108°) also showed a strong positive linear correlation (p<0.001, Pearson correlation coefficient, 0.947). Equally anterosuperior measurements showed a significant (p<0.001) strong positive linear association (Pearson correlation coefficient: alpha angle: 0.889; beta angle: 0.887) between MR and US (alpha angle mean: 59.7°/69.5°; SD: °11.2/11.7°; range: 41°-82°/43°-94° and beta angle: mean: 49.2°/57.2°; SD: 15.3°/12.2°; range: 21°-90°/31°-87°) angles. Based on these a correction factor for US screening measurements was calculated (alpha/beta angle: anterior, -12°/-4°; anterosuperior, -10°/-8°). Qualitative read-out showed no significant differences of osseous bumps, head-neck junction, or eccentricity of the femoral head between MRI and US using McNemar test.

US of the femoral neck allows screening for femoroacetabular cam-impingement and permits measurement of the alpha and beta angle comparable to MR imaging using a correction factor.

US of the femoral neck allows screening for femoroacetabular cam-impingement.

Buck, F, Zanetti, M, Hodler, J, Pfirrmann, C, Is It Possible to Use Ultrasound to Screen Patients for Femoroacetabular Cam Impingement?.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6016320.html