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Femoroacetabular impingement (FAI) is a condition in which abnormal contact between the femoral head-neck junction and the acetabular rim occurs during hip motion, particularly flexion and internal rotation.
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Femoroacetabular Impingement Explained: Groin Pain, Labral Tears, Best Exercises & Surgery
https://www.youtube.com/watch?v=ENjq5Is94PE
| Type | Morphological Feature | Epidemiology | Key Radiological Sign | Pathophysiology |
|---|---|---|---|---|
| Cam type | Aspherical femoral head with bony convexity at head–neck junction (usually anterosuperior) | Young athletic males | Alpha angle > 55° on MRI/CT | Shearing of cartilage and labrum due to loss of femoral sphericity |
| Pincer type | Acetabular overcoverage, often anterior | Middle-aged women | Crossover sign, center-edge angle > 40° on AP radiograph | Labrum compressed between overhanging acetabulum and femoral neck |
| Mixed type | Features of both cam and pincer | Most common in clinical practice | Combination of the above | Complex interaction of mechanisms |
Diagram outlining the mechanisms of chondral and labral injury in cam impingement. The main focus of injury is the chondrolabral junction. There is relative sparing of the labrum until later in the disease process
Li, A.E., Jawetz, S.T., Greditzer, H.G. et al. MRI for the preoperative evaluation of femoroacetabular impingement. Insights Imaging 7, 187–198 (2016). https://doi.org/10.1007/s13244-015-0459-0
Diagram outlining the mechanisms of chondral and labral injury in pincer impingement. The labrum is the main focus of damage. Chondral injury is initially limited to a relatively small strip of cartilage at the transition zone
Li, A.E., Jawetz, S.T., Greditzer, H.G. et al. MRI for the preoperative evaluation of femoroacetabular impingement. Insights Imaging 7, 187–198 (2016). https://doi.org/10.1007/s13244-015-0459-0
Clinical triad:
Secondary findings:
Clinical evaluation: