Femoral Acetabular Impingement
Femoral Acetabular Impingement (FAI) is an increasingly recognised source of hip pain in the younger adult population. There are two types of abnormal hip morphology that lead to FAI, though these can co-exist in a ‘mixed’ presentation. The first one is a Cam deformity (more common in males), and this is an abnormal bony prominence or ‘bump’ at the femoral head-neck junction. Secondly A pincer lesion (more common in females) is an abnormal bony overhang of the anterolateral acetabular rim resulting in over-coverage of the femoral head. These bony changes lead to abnormal contact between the femoral head and the acetabulum, which can result in labral tears and cartilage damage and ultimately the early onset of hip osteoarthritis. Femoroacetabular Impingement – StatPearls – NCBI Bookshelf
FAI is not an uncommon entity, with the overall incidence of symptomatic FAI shown to affect 3% of the total population. Incidence of Symptomatic Femoroacetabular Impingement: A 4-Year Study at a National Collegiate Athletic Association Division I Institution – PMC Whereas the prevalence of asymptomatic FAI has been found to be closer to 15% in the general population. The prevalence of cam-type femoroacetabular deformity in asymptomatic adults – PubMed. Meaning in order to be diagnosed with this condition, you need to have both the clinical symptoms along with radiographic/MRI morphology changes.
FAI is the most common cause of labral tears in the young hip but they can also develop due to other underlying issues, including dysplasia, trauma and degeneration A comprehensive review of hip labral tears – PubMed for the sake of this patient information context, we will be focusing on those caused by FAI.
What are the signs and symptoms?
This condition affects the young adult hip (late teens to mid-3rd decade of life) with a clear link to sporting or high-demand activities. Patients complain of an insidious onset of typical groyne pain, which is often described with a C-sign (hand forming a C) over the anterior hip. Trochanteric pain (lateral hip pain) can often co-exist.
Deep hip flexion and prolonged sitting are often provocative, and patients can describe mechanical symptoms such as clicking/catching due to bony impingement and subsequent labral tears stopping free movement of the joint. Femoroacetabular Impingement – StatPearls – NCBI Bookshelf
How is it diagnosed?
The diagnosis of FAI will usually be made from a combination of your clinical history, examination findings, and a plain film X-ray of your pelvis.
Patients will be of appropriate demographics and describe the aforementioned symptoms. Clinically the FADIR test (combination of flexion, adduction and internal rotation of the hip) is provocative; this test has been shown to be highly sensitive for provoking intraarticular hip pathology Sensitivity and Specificity for Physical Examination Tests in Diagnosing Prearthritic Intra-Articular Hip Pathology Are Highly Variable: A Systematic Review – PubMed. Contractile strength around the hip adductors is usually preserved and unprovocative; there is usually not any symphysis pubis symptoms and no evidence of inguinal pathology. A plain film x-ray, typically an AP view of the pelvis and a lateral view of the proximal femur, will demonstrate the abnormal bony morphology. Sometimes a ‘Dunn’ View is obtained with the patient lying supine; the hip joint is flexed to 90 degrees and abducted to 20 degrees. This position has a high sensitivity for detecting femoral head-neck asphericity.
An MRI scan will be needed to assess the cartilaginous acetabulum labrum for any concurrent tears. Sometimes these can be missed on MRI, and a Magnetic Resonance Arthrography (MRA) may be requested; however, with new 3T MRI scanners, these tears can often be reported on accurately and reliably.
How are they treated?
Treatment options are divided into conservative and surgical.
- Advice, education and a period of unloading/avoidance of the aggravating factors (where possible) can sometimes allow symptoms to settle.
- An ultrasound-guided hip joint injection of local anaesthetic +/- steroid into the joint itself can be helpful from a diagnostic perspective, confirming symptomatic FAI +/- labral pathology. It can also provide therapeutic relief at 12-month follow-up in certain individuals, avoiding the need for surgical intervention. Utility of Intra-articular Hip Injections for Femoroacetabular Impingement: A Systematic Review – PMC. Where surgical workup is being considered, the outcome of the injection is important, as evidence shows that a negative response to preoperative targeted injections predicts poorer surgical outcomes.
Surgical options:
If conservative options do not provide adequate relief or if there is a reoccurrence of symptoms following a beneficial diagnostic hip joint injection, then there are surgical options.
- Hip arthroscopy/keyhole surgery. This is the surgical treatment of choice for carefully selected patients, with key exclusions being the presence of any hip arthrosis or hip dysplasia. The procedure involves reshaping the bony deformities (osteoplasty), excising loose bodies and repairing/debriding labral tears. A comprehensive review of hip arthroscopy techniques and outcomes – Carlos Suarez-Ahedo, Javier Camacho-Galindo, Alberto López-Reyes, Laura E Martinez-Gómez, Carlos Pineda, Benjamin G Domb, 2024. It has a favourable outcome in reducing symptoms and allowing return to high-demand activity/sporting requirements in appropriate patients that have been suitably worked up. Hip Arthroscopy for Femoroacetabular Impingement-Associated Labral Tears: Current Status and Future Prospects – PubMed
Book An Initial Consultation Online
No GP referral needed.
Expert specialist care.
