Biomechanical Investigation of Symptomatic FAI and Two Groups of Asymptomatic Controls

Femoroacetabular impingement (FAI) is an orthopaedic condition that is primarily characterized by the presence of anatomic bony abnormalities in the femoral head and/or the acetabulum resulting in an abnormal contact between the two during hip motion, especially in positions of increased hip flexion and rotation, ultimately leading to hip pain. FAI can be radiologically classified into 3 types of morphology: Pincer, CAM and mixed type. While a clear-cut radiological classification makes the identification of FAI seem quite straightforward, it fails to differentiate between symptomatic and asymptomatic patients.

Unfortunately, a FAI diagnosis is frequently only made once symptoms have become severe to an extent that they limit everyday life activities. Not only this movement restriction is a significantly debilitating factor in such a young active population, a recent study reported FAI patients to see on average 4.0 health care providers, undergo on average 3.4 diagnostic imaging tests, and receive on average 3.1 treatments prior to final diagnosis. This raises the cost of an individual FAI diagnosis to be €1,563.26 higher than the calculated minimum required cost. Such calculations clearly reveal the long-lasting, multifactorial burden of FAI on society.

Moreover, another important aspect that has been consistently overlooked in past FAI movement studies is the influence muscle strength and activation can have on movement pattern and symptom presentation. To our knowledge only three studies have looked into muscle strength by using mainly hand-held dynamometers to record the isometric strength of hip musculature. Their findings suggest hip muscle weakness in symptomatic FAI subjects, but whether this weakness is a pain protective consequence, or an actual cause of FAI is still unknown.

In conclusion, the diagnosis and management of FAI needs to be addressed through a more wholesome investigation of the biomechanical influence on the manifestation of symptoms.

This project aims to further unravel the link between spinopelvic anatomy, its biomechanical contribution to femoro-pelvic motion and the manifestation of femoroacetabular impingement in adult male population. By, for the first time, integrating three-dimensional (3D) instrumented motion analysis with state-of-the-art full-body biplanar X-ray imaging (EOS imaging, Paris France), we will more specifically investigate the presence of an association between spinopelvic kinematics and the link to symptomatic FAI morphology, as well as investigate the presence of differences in these measures between symptomatic and asymptomatic subjects with comparable femoral morphology.

Exclusion criteria

• Participants in all three study groups will be excluded if x-ray scans shows a pincer FAI morphology or radiological sign of osteoarthritis.

Inclusion criteria

• All participants will be males aged between 21 and 35 years old.
• For symptomatic CAM-FAI patients

• The presence of CAM-FAI morphology at the head-neck junction of the femur
• Alpha angle >60
• Reduced hip internal rotation (IR<15)
• For asymptomatic CAM controls:

• Exhibit asymptomatic CAM on x-ray scansAlpha angle >60
• For Healthy control group:

• Exhibit no symptoms or abnormal morphologies of the proximal femur (Alpha angle >60 , IR>15).