Ganz and colleagues recently described the concept of femoroacetabular impingement (FAI) as a source of labrum (labral) tears and articular cartilage injury. Two bony abnormalities, CAM and pincer, frequently occur together. CAM impingement results from abnormal contact between an abnormally shaped femoral head and neck with a morphologically normal acetabulum. This type of impingement may be of unknown cause or may be associated with femoral neck fractures that have healed incorrectly, slipped femoral capital epiphysis, or Legg-Calve-Perthes disease. Pincer impingement results from abnormal contact between a normal femoral head with an abnormal acetabulum. This type of impingement is the result of focal (acetabular retroversion) or global (deep socket) over-coverage.
Because of its association with articular cartilage injuries and labral tears, there is considerable overlap in terms of presenting symptoms. Asymmetrical range of motion, especially into flexion-internal rotation or flexion–abduction–external rotation, may be noted. Radiographs and MRIs are the current standard to assess for FAI.
Open or arthroscopic surgical interventions include osteoplasty to reshape the head – neck junction of the femur or rim trimming to remove excessive bone from the acetabular rim.
Impingement is due to a bony abnormality and therefore no true preventative measure can be taken. Proper maintenance of core strength and muscle balance in and around the hip may help protect the soft tissues in the joint.