[Femoroacetabular impingement - Update 2019]

Since the first description of the femoroacetabular impingement (FAI) concept diagnostic imaging of FAI has continuously been developed.

The biomechanical concept is explained and an update on diagnostic imaging of FAI is presented.

Based on a literature search this review article presents the current state of knowledge about FAI mechanisms and gives an overview on state of the art radiological diagnostics. A perspective on new imaging methods is also given.

The FAI is a dynamic phenomenon with a mechanical conflict between the femoral head and/or neck and the acetabulum. It is usually suspected clinically; however, imaging plays an essential role in establishing the diagnosis by detecting and defining the underlying deformities of the proximal femur (cam deformity) and the acetabulum (pincer deformity) and by evaluating associated lesions of the articular cartilage and labrum. Basic imaging diagnostics consist of anteroposterior and lateral radiographs. Magnetic resonance imaging (MRI) and MR arthrography are the preferred imaging modalities for detailed analysis of deformities, for the detection and graduation of lesions of articular cartilage (sensitivity 58-91%) and labral lesions (sensitivity 50-92%). Simultaneously, these methods can exclude other hip diseases. Current standards and new developments in FAI imaging are presented.

For the diagnosis of FAI typical clinical and imaging findings are required. Radiological diagnostics are an indispensable component in establishing the diagnosis of FAI, in the differentiation of the underlying deformities and in the assessment of treatment-relevant joint damage.