Until the advent of MRI scanning and hip arthroscopy, FAI was an underdiagnosed condition of hip pain and young adults. FAI is a mechanical problem related to impingement between the neck of the femur and the rim of the acetabulum and it’s attached acetabular labrum. This impingement most commonly occurs in flexion, adduction and internal rotation and patients present with groin pain which may be reproduced with provocative testing. Chronic femoroacetabular impingement results in damage to the acetabular labrum (labral tears) as well as secondary cartilage delamination which will progress to focal cartilage loss and early onset of osteoarthritis over time.
There are two types of femoroacetabular impingement. Cam-type impingement occurs in young male patients with a normal acetabular depth who have developed a significantly large osteophyte on the femoral neck or who have a abnormally shaped femoral neck secondary to conditions such as slipped upper femoral epiphysis.
Pincer type impingement occurs in middle-aged female patients with a deep acetabulum and a normal femoral neck. Primary pathological conditions which may cause this are soft bone diseases such as rheumatoid arthritis.
Impingement is usually confirmed with an MRI scan, which will indicate the amount of labral damage as well as the degree of cartilage thinning and delamination, which is a consequence of chronic impingement. Management in young patients with minimal cartilage damage involves hip arthroscopy with either simple debridement of the damaged labrum or arthroscopic labral repair.
Older patients with established cartilage damage (which may not always be visible on x-ray) have not been shown to benefit from hip arthroscopy and will require conservative management of early hip arthritis with a view to an arthroplasty procedure later in their lives.