CAM Impingement

What is it?

CAM impingement is the most common form of femoroacetabular impingement (FAI) and is a condition related to the bony morphology of the hip joint. it has recently come into the spotlight in terms of research and advancing treatment. It is characterised by excessive abutment of the femoral head-neck junction (ball) against the rim of the acetabulum (socket). In the case of CAM impingements, the excess bone is on the femoral aspect leading to an aspherical femoral head. (Leunig et al, 2009)

 

Causes:

Genetics are thought to be the primary factor for development of the underlying bony morphology (Pollard et al, 2010). The condition has been associated with a more active population, particularly of the running/kicking athlete type (Siebenrock et al, 2011) . However, a large number of CAM lesions are also present in the non sporting and asymptomatic population and it is thought that the above sporting activities are more likely to cause aggravation of the joint where the bony changes are already present . 

 

Symptoms:

  • Hip/groin pain aggravated by squatting, twisting, pivoting movements
  • Buttock pain
  • Reduced hip movement/joint stiffness, particularly into flexion and internal rotation
  • Altered motor control of the pelvis/hip (Kumar et al, 2014)

 

Associated Issues:

  • Labral tear – the labrum is a rim of cartilage around the acetabulum (socket) that creates a tight seal between the femoral head and acetabulum, hence maximising joint stability. Impingement of the femoral neck on the acetabulum can cause wearing/tearing of this cartilage, leading to increased pain, joint instability and occasionally a clicking/catching sensation on movement
  • Back pain – due to limited movement in the hip,  the joints in the lower back may be susceptible to further loading to achieve functional tasks eg forward flexion. Overtime this can lead to repetitive strain and low back pain
  • Osteoarthritis – In some cases, CAM impingement can be present without symptomsor associated issues. However, in cases where symptoms are present and particularly where there is progression to labral tearing, there may be a higher risk of degeneration of the joint 

 

Management Options:

  • Investigation: If you are suffering from hip pain and FAI is suspected on clinical examination, an MRI scan will help to confirm diagnosis and identify presence of labral tear or further degenerative changes. This will help to guide management
  • Physiotherapy: will not reverse/change bony morphology that is present but it can be helpful in settling symptoms by using techniques to offload the structures under stress. An exercise programme specifically directed towards pelvic and hip stability and retraining of movement patterns in functional tasks is essential whether or not further management is required
  • Medical Management: Anti-inflammatory medication and injection therapy can be used to settle inflammation present as a result of impingement itself or associated labral tear. Again, this will not affect the bony changes in the joint or remove the root cause but may provide pain relief and a window of opportunity to maximise rehabilitation
  • Surgical intervention: if conservative management is not successful, a surgical approach may be employed to trim/shave the excess bone on the femoral neck and repair/remove damaged labrum. In most cases, this can be done arthroscopically with small incision and minimal invasion. Although FAI osteoplasty is a relatively new procedure that is currently under research in terms of long-term outcome, results are shown to be positive at medium-term follow up (Gupta et al, 2014).