The purpose of this retrospective study was to investigate the acetabular morphology of pincer impingement hips in order to better understand damage pattern in these patients. We compared MRI measurements made at different postions from anterior to posterior on the acetbulum in patients with pure pincer type FAI to those made in patients with pure cam-type to collect parameters that may be useful in the diagnosis and classification of pincer impingement. From an initial consecutive retrospective population of 1022 patients that underwent MRI with clinical impingement signs 78 hips which were selected with as clear cam (n=57) or pincer (n=21) impingement on plain radiographics. On these MR Imaging was performed with a 1.5-Tesla system. For analysis, a lateral angle of overcoverage on coronal MRI (MR_LCE), the MR extrusion index and the alpha angle (after Nötzli) were used. In addition to these the gamma angle, the acetabular depth and the angle of lateral acetabular overcoverage were described clock-wise on 7 radial slides from anterior to posterior. These were compared between the cam and pincer population using students-t-test. Measurements were obtained by two observers and inter-observer variability was assessed.Purpose
Material and Methods
