Also known as: Femoroacetabular Impingement, FAI
Associated with labral tear/labral damage
The hip is a ball and socket joint where the spherical ball at the head of the femur (thigh bone) rotates in a hollow cup in the pelvis called the acetabulum.
Sometimes a lump can develop behind the head of the femur (Cam deformity), or on the front wall of the acetabulum (Pincer) both of which can interfere with the smooth movement of the joint.
These lumps can initially cause groin pain during certain movements but longer term can lead to damage to both sides of the joint, and may even cause hip arthritis.
There are many theories why the lumps appear. One is that they are the result of stress when the hip is at extremes of movement, when playing rugby, for example. Another theory is that they represent an injury to the hip when it was growing.
Hip impingement was first recognised in Australian Rules football players, where the team orthopaedic surgeon noted that most of his players were having hip replacements before they were 40. He also realised that many players were unable to play because of groin pain. When he studied their X-rays, he noticed that they had the same pattern of arthritis, and then he recognised the Cam bump. He removed the bumps with open surgery, which gave the players better function of their hips and they were able to get back to professional sport.
With a Cam deformity, as the patient flexes their hip forwards and turns their leg so that the knee is pointing inwards, they bring the Cam lump into contact with the acetabular rim and the ring of cartilage known as the labrum.
When the labrum gets repeatedly hit by the Cam it will eventually tear, producing pain. Eventually the socket itself gets damaged, resulting in arthritis.
Pincer deformity is more common in women and is thought to run in families. As with the Cam deformity, when the patient flexes their hip forwards and turns their leg so that the knee is pointing inwards, they will bring the normal femoral neck into contact with the abnormal acetabular rim and its labrum. Again this produces damage to the labrum and the socket.
The surgeon will determine when and where the pain is and what causes it. A specific x-ray is taken to show the shape of the bones of the hip. Usually an MRI scan of the hip is required. To get the best image of the labrum, a special MRI dye is first injected into the hip under local anaesthetic.
If the symptoms are not severe and the patient does not want surgery, physiotherapy and behaviour modification can help. Patients are advised to refrain from doing the movement that causes the pain. There is a physical cause for the pain and lack of movement, and while physiotherapy can help some patients, it will not cure the problem.
If surgery is deemed the best treatment then the operation will usually be performed as a day case.
The surgery is usually a keyhole procedure through two or three small (less than 8mm) incisions, via an arthroscope (similar to a small telescope). If there is a cam or pincer deformity, the extra bone will be shaved off. Tears to the labrum can be repaired by fixing them back to the acetabular rim using special anchors.
The patient will be sent home on crutches and will not be allowed to put full weight on the recovering leg for four weeks. The physiotherapist will work closely with the patient over the next 10 to 12 weeks to regain strength and range of movement in the leg.
Most patients are able to swim after their wounds have healed; able to run at six weeks; and will be fully back to all sport by three months.
Many family doctors will not be fully aware of hip arthroscopy but 80% of patients’ symptoms will have improved after surgery.
Approximately 15% of patients’ symptoms will remain the same and 5% of patients may become worse.
This surgery may decrease the onset of arthritis but sometimes the cam deformity may return.