Current concepts in the management of femoroacetabular impingement

Abstract

The Journal of Bone and Joint Surgery. British volumeVol. 87-B, No. 11 Aspects of Current ManagementFree AccessCurrent concepts in the management of femoroacetabular impingementJ. R. Crawford, R. N. VillarJ. R. CrawfordOrthopaedic Specialist RegistrarCambridge Hip and Knee Unit, BUPA Cambridge Lea Hospital, Impington, Cambridge CB4 9EL, UK.Search for more papers by this author, R. N. VillarConsultant Orthopaedic SurgeonCambridge Hip and Knee Unit, BUPA Cambridge Lea Hospital, Impington, Cambridge CB4 9EL, UK.Search for more papers by this authorPublished Online:1 Nov 2005https://doi.org/10.1302/0301-620X.87B11.16821AboutSectionsPDF/EPUB ToolsDownload CitationsTrack CitationsPermissionsAdd to Favourites ShareShare onFacebookTwitterLinked InRedditEmail Secondary osteoarthritis of the hip occurs due to a known precipitating cause. In primary or idiopathic osteoarthritis the cause remains unknown although some studies1,2 have suggested that femoroacetabular impingement (FAI) may be responsible for the progression of degenerative changes in this group of patients. FAI is a distinct pathological entity and can be defined as the abutment between the proximal femur and the acetabular rim.3 It affects active, young adults and presents clinically with groin pain. FAI can occur either in patients with an abnormal morphology of the hip or in patients with a normal anatomical structure but who have an excessive range of hip movement.Mechanism of femoroacetabular impingementA widening of the femoral neck or a decreased offset at the anterolateral head-neck junction results in decreased joint clearance.4 This results in repetitive contact between the femoral neck and the acetabular rim which is responsible for a range of injuries including anterior hip pain, labral tears and damage to the acetabular articular cartilage.5 Several studies have shown that FAI can cause a progressive degenerative process and lead to early osteoarthritis of the hip.1,2,6,7There are two distinct types of FAI. The first type, ‘cam impingement’, is more common in young, athletic men. It is commonly due to a nonspherical portion of the femoral head abutting against the acetabular rim especially in flexion and internal rotation.1,8 This causes an outside-in abrasion of the acetabular cartilage which may result in its avulsion from the labrum and subchondral bone. Damage to the acetabular cartilage occurs in the anterosuperior area of the acetabulum and can lead to separation of cartilage from the labrum.9The second type of FAI, ‘pincer impingement’, is more common in middle-aged athletic women. It is due to the contact between the femoral head-neck junction and the acetabular rim. Repeated abutment leads to degeneration of the labrum resulting in intrasubstance ganglion formation, ossification of the acetabular rim and deepening of the acetabulum. The chondral damage is located more circumferentially and usually includes only a narrow strip of acetabular cartilage. Changes in the labrum occur at adjacent areas often present as ossification of the labrum.9Cam and pincer impingement rarely occur in isolation. In their study of 149 hips, Beck et al9 found that only 26 hips had an isolated cam and 16 hips had an isolated pincer impingement. They found that most cases of FAI involve a combination of these two mechanisms and are classified as having mixed campincer impingement.Histologically, FAI is characterised by a gentle chronic irritation of the labrum located at the site of rupture that elicits a degenerative reaction.10 In a study of 25 patients with symptomatic FAI, there was no difference in the histopathological features of the acetabular labrum between cam and pincer impingement.10AetiologySeveral predisposing conditions reduce the femoral head-neck offset resulting in cam impingement.1 These include slipped capital femoral epiphysis with posterior tilt of the femoral head,2,11 femoral head necrosis with subsequent flattening,12 previous fracture of the femoral n