![]() Plain radiography is based on a point-shaped source with conical beam projection. In order to correctly interpret plain radiographs, standardized acquisition techniques have to be applied as plain films represent a 2D image of a 3D structure. Perthes disease, developmental dysplasia of the hip, slipped capital femoral epiphysis, etc.) and exclusion of preexisting advanced osteoarthritis (OA ). Plain radiographs allow recognition of a wide variety of underlying hip disorders (i.e. Plain radiography is the primary imaging modality in the diagnostic process of FAI. This is represented by an increased lateral center edge angle (LCE) >40°, a negative acetabular index (AI) and a decreased extrusion index (EI) <16%. The femoral head crosses the ilio-ischial line on both sides indicating acetabular protrusion. The AP pelvic radiograph of a 26 years old female patient with bilateral general acetabular overgrowth and subsequent pincer type FAI is shown. ![]() In the majority of cases, however, the etiology of FAI is developmental, or idiopathic. While FAI describes the pathomechanism, the abnormal morphology can be caused by various underlying conditions such as Legg-Calvé-Perthes disease (LCPD), slipped capital femoral epiphysis or post-traumatic deformities. Cam and pincer type FAI frequently occur concomitantly. Pincer type impingement is typically seen in hips with deep acetabula (i.e. Pincer type FAI is characterized by an excessive acetabular wall that results in a compression of the labrum between the femoral neck and the acetabular rim. Cam Type FAI is predominantly the result of an aspherical contour at the antero-superior femoral head-neck junction that (when rotating into the acetabulum) applies compression and shearing forces at the chondro-labral junction leading to chondro-labral separation, degeneration of the labrum and detachment of the cartilage from the subchondral bone. Intra-articular impingement is subdivided into cam- and pincer type FAI ( Fig. BACKGROUND FAIįAI is a dynamic conflict of the hip defined by an early abutment of the proximal femur onto the acetabulum. The following article provides a literature review on preoperative evaluation of patients suffering FAI, highlighting the roles of different imaging modalities used in the detection of the underlying pathologies. While plain radiography and MR-arthrography (MRA) remain the gold standard in preoperative assessment, other imaging modalities including biochemical sequences of magnetic resonance imaging such as dGEMRIC as well as computed tomography (CT) and preoperative computer assisted animation and treatment simulation play an increasingly important role when evaluating pathologies associated with FAI. Over the past years, an increasing number of imaging modalities for the evaluation of FAI have made their way into clinical practice. Although the diagnosis is primarily made clinically, imaging plays a crucial role in the preoperative assessment. Selecting the right patient for surgical treatment is imperative. ![]() The understanding of the patho-biomechanics has evolved over the past decades leading to a variety of surgical treatment options including open and arthroscopic procedures with promising reported results. Since the description of femoroacetabular impingement (FAI), there has been increasing recognition and interest in this condition. This article provides a summary of current concepts of imaging in FAI and a review of the literature on recent advances, and their application to clinical practice. Advantages of CT include superior bone to soft tissue contrast, making CT applicable for image-guiding software tools that allow evaluation of the underlying dynamic mechanisms causing FAI. Computed tomography may serve as an adjunct. ![]() Recent advances in MRI technology include biochemically sensitive sequences bearing the potential to detect degenerative changes of the hip joint at an early stage prior to their appearance on conventional imaging modalities. Routine diagnostic work-up consists of a set of plain radiographs, magnetic resonance imaging (MRI) and MR-arthrography. While the diagnosis of FAI is primarily made based on the patients’ history and clinical examination, imaging of FAI is indispensable. Following the recognition of femoroacetabular impingement (FAI) as a clinical entity, diagnostic tools have continuously evolved. ![]()
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