What it is.
The hip works well when a round ball turns inside a matched socket. Femoroacetabular impingement is what happens when the two shapes do not match, so at the extremes of movement the neck of the femur abuts the rim of the socket instead of clearing it.
There are two patterns, and many hips have both:
- Cam. Extra bone on the head-neck junction of the femur, so the ball is not perfectly round. As the hip flexes and rotates, that extra bone is driven into the socket, shearing the cartilage at the rim. More common in men, and associated with high-level sport during adolescence while the growth plate is open.
- Pincer. Over-coverage of the socket, so the rim projects further than it should and the neck strikes it earlier in the arc. More common in women.
An important distinction: the shape is common, the syndrome is not. Cam morphology is found in a large proportion of asymptomatic people, particularly athletes. Impingement becomes a diagnosis only when the shape, the symptoms and the examination findings all agree. That is why current consensus uses the term FAI syndrome rather than treating the radiograph alone as the diagnosis.
Symptoms.
Groin pain brought on by positions that close the hip down: deep squatting, prolonged sitting, getting out of a low car, cycling. Pain typically comes on after activity rather than during it at first. Many people notice restricted internal rotation before they notice pain, and some describe clicking or catching from an associated labral tear.
How it is diagnosed.
Examination reproduces the pain on flexion, adduction and internal rotation, and usually shows reduced internal rotation compared with the other side. Plain radiographs, including a lateral view of the head-neck junction, show the bony shape. MRI shows the labrum and the cartilage. A diagnostic injection confirms the joint as the source.
Treatment.
Non-operative management is the starting point and is effective for many: modifying the positions that provoke it, physiotherapy for the deep stabilisers and gluteal muscles, and sometimes an injection.
Where symptoms persist in a hip with preserved cartilage, arthroscopic surgery to reshape the bone and address the labrum is an option, performed by a hip preservation surgeon. Randomised trials have shown benefit over physiotherapy alone in appropriately selected patients.
Where the cartilage is already substantially worn, reshaping the bone no longer helps. The relevant question at that point is whether the symptoms justify hip replacement.
Where this practice fits.
Professor Rodda's practice is focused on hip and knee replacement. He does not perform joint-preserving surgery such as arthroscopy or osteotomy. If your condition is at a stage where preservation surgery is the right option, you will be told that and referred to a colleague who does it, within Sunshine Coast Orthopaedic Group or elsewhere. Where the joint has reached the point that replacement is the reasonable option, that is the work done here.
Common questions.
Does impingement always cause arthritis?
No. Cam and pincer shapes are common and most people who have them do not develop symptoms or arthritis. Impingement is associated with a higher risk of earlier osteoarthritis, particularly cam morphology, but it is a risk factor rather than a certainty.
Can impingement be fixed without surgery?
The bony shape cannot be changed without surgery, but the symptoms often can be managed without it. Avoiding provoking positions and targeted physiotherapy help a significant proportion of people.
Is surgery for impingement worth it?
In carefully selected patients with preserved cartilage, randomised trials have shown arthroscopic surgery gives better outcomes than physiotherapy alone. Selection is the critical variable: the same operation in a hip with established arthritis does not help.
Am I too old for impingement surgery?
It is less about age than about cartilage. Results fall off substantially once there is joint space narrowing on a weight-bearing radiograph, which becomes more likely with age. Beyond that point hip replacement is the operation that reliably helps.
Does Professor Rodda treat impingement?
He treats the arthritis that can follow it, with hip replacement. Arthroscopic surgery for impingement is performed by hip preservation surgeons, and you will be referred if that is the right option.
References.
- Griffin DR, Dickenson EJ, O'Donnell J, et al. The Warwick Agreement on femoroacetabular impingement syndrome. Br J Sports Med. 2016;50(19):1169-1176.
- Griffin DR, Dickenson EJ, Wall PDH, et al. Hip arthroscopy versus best conservative care for the treatment of femoroacetabular impingement syndrome (UK FASHIoN): a multicentre randomised controlled trial. Lancet. 2018;391(10136):2225-2235.
- Agricola R, Heijboer MP, Bierma-Zeinstra SMA, et al. Cam impingement causes osteoarthritis of the hip. Ann Rheum Dis. 2013;72(6):918-923.
This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.