Osseous impingement occurs early in flexion in cam-type femoroacetabular impingement

What is it about?

Femoroacetabular impingement (FAI) is a common condition that affects about 25% of the population, and 80% of professional footballers. In FAI a bump of bone can form on the head of the femur, called a cam deformity. The presence of a cam deformity can result in damage to the cartilage and soft tissue of the joint, which can lead to osteoarthritis of the hip. It is believed that this damage is caused when the cam deformity impinges on the socket of the hip joint when the hip is brought into high flexion and internal rotation. However, our understanding of how a cam deformity may cause damage is based on images taken when the hip is stationary, observations made during surgery, and computer simulated models. None of these methods have been able to truly show us when the cam deformity impinges on the joint in real time functional movement. As such our understanding of how the presence of a cam deformity affects hip movements, and how it may result in osteoarthritis, is limited. Due to this, our ability to determine which patients will be benefit from most from conservative or surgical treatment remains poor. Recent advances in CT scanning technology have allowed the development of real time scanning. Multiple CTs are taken as the hip joint is moved through flexion and internal rotation. From these CTs a 3D model of the bones of the joint can be created that shows the movement of the bones in real time. This is sometimes called 4D CT scanning. We aimed to use 4D CT scanning of the hip to examine the effect of having a cam deformity on hip movement, and determine if the size and location of a cam deformity was important. We found that impingement may be occurring much earlier than previously thought, and a larger cam deformity will result in earlier impingement. Our findings would suggest that the individuals with a large cam deformity may be impinging in functional movements such as walking or going up stairs. Our findings could have large impacts on our understanding of how the hip moves in the presence of a cam deformity, and how we decide treatment options in FAI.

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