This is the key question those of us involved in hip preservation surgery would like to be able to answer. At the present time we only know that timely intervention is effective in getting individuals back to their sport. Timely intervention means before the hip joint has become too damaged. What we do not know is if early intervention, particularly in relation to FAI and arthroscopic hip surgery, will necessarily protect the hip from future damage and the risk of injury and osteoarthritis. There is more evidence that early intervention in dysplastic hips by way of a PAO (periacetabular osteotomy) is effective in delaying in the onset of hip arthritis.
One area that we are gathering more information about is the effect of high level sports training/participation during adolescence. There is increasing evidence that a high level of sports activity during the time that the hips are developing is associated with femoral head changes in particular a cam-type deformity. Initially there was an observation that hips with FAI appearances appeared to be more common in athletic individuals. More focussed studies have now implicated that it is the effect of the training itself that can alter the shape of the hip. This is particularly unfortunate, as with an abnormal hip shape a lot of high level activity is going to be more likely to damage the hip.
At a recent meeting of the International Hip Society in London I had the opportunity to discuss with Prof Ganz, who characterised the nature of the hip injury caused by FAI, why it was that some individuals presented early with pain from their hips and others very late when there was already significant damage with osteoarthritis. The area of the hip that transmits pain is the labrum which is the soft cartilage rim around the hip which provides a suction seal around the femoral head. In certain types of FAI this gets directly traumatised and leads to significant pain early in the development of the condition. The pain therefore provides a warning sign that potentially something bad is going on.
In other cases the labrum is not injured directly and so the damage to the articular cartilage within the joint (which does not have any nerve pain fibres) can continue and become very severe before pain starts to develop; unfortunately by that time it is maybe too late to save the joint. This is the situation in many cases of cam impingement, where the initial injury is caused when the abnormal area of the femoral head slides under the labrum and produces abnormal shear stresses against the articular cartilage of the joint. Eventually the labrum does become increasingly damaged and therefore often starts to cause pain, but the early warning sign was not there.
Ongoing research in this area will allow us to advise patients better as to the optimal time for intervention in these hip conditions.