FAI Part 1: Epidemiology in Hockey

Femoroacetabular impingement (FAI) is a hot topic right now for sport performance and rehab. In this series of articles, we will be discussing FAI in great detail to give you a better understanding of what it is, where it comes from and why we need to be concerned about it.

In this first article, we will be talking about FAI in general.  There are 2 types of FAI: cam deformities and pincer deformities. A cam deformity occurs when the head/neck of the femur loses it’s spherical shape, while a pincer deformity occurs when the acetabular rim deepens by bony growth and creates an overcoverage of the femoral head (see figure below).

According to Mannava et al  (2017), a diagnosis of FAI can be confirmed best with a plain x-ray. The diagnosis is made by measuring an alpha angle greater than 55^o. The alpha angle is measured by drawing a line from the narrowest point of the femoral neck through the centre of the femoral head. To determine the angle, we must also draw a line from the centre of the centre of the femoral head to the location where the femoral head doesn’t fit into the best fit circle (see figure below).

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These bony changes are very common in hockey players. It has been shown that > 85% of hips in NHL hockey players showed some form of cam deformities (Larson et al. 2016). Research has also shown that hockey players are 10x more likely to have a greater alpha angle on an x-ray compared to a control group (Kuhn et al 2016). There is also research to support that the alpha angle progresses with age when looking at youth hockey players (10-18years old) (Kuhn, 2016). This may suggest that the repetitive stress of playing hockey on an immature skeletal system may be a factor in the progression of this condition

Although this is a common condition, especially in hockey players, it isn’t always necessarily problematic. For the most part, these morphological changes are asymptomatic (Lerebours et al, 2016). However, it does become a problem when it leads impingement symptoms, hip labral tears, and early onset hip osteoarthritis later on in life (Kuhn, 2016, Lerebours, 2016). It also leads to a decrease in hip range of motion (Larson et al, 2017) which can be an issue for skating performance, but that will be a topic for another post.