The Role of Imaging in Femoroacetabular Impingement: History, Current Practices, and Future Applications.

¼: Femoroacetabular impingement (FAI) is one of the most common causes of early hip articular cartilage wear and labral damage, and subsequently leads to the onset of hip osteoarthritis. ¼: Cam-type FAI impingement lesions can be best identified with a 90° Dunn lateral radiograph and a cross-table lateral radiograph with 15° of internal rotation; the alpha angle and the femoral head-neck offset are the most used predictive radiographic markers. ¼: FAI lesions with pincer impingement are associated with acetabular retroversion and are more difficult to identify on traditional radiographic imaging; however, the presence of a crossover sign, an ischial spine sign, and/or a posterior wall sign can be useful radiographic markers. ¼: Advanced imaging modalities such as magnetic resonance imaging (MRI) and/or magnetic resonance arthrography (MRA) can also be beneficial in the evaluation of FAI and labral pathology; MRA is more sensitive than MRI in detecting intra-articular pathology. ¼: Computer-assisted navigation for preoperative planning and intraoperative surgical assistance are promising technologies; however, additional studies are needed before they can be utilized safely and effectively.