What it is.
A normal hip socket covers the ball well, so body weight is spread over a large area of cartilage. In dysplasia the socket is shallower and more vertical, so the same load is carried over a smaller area. Contact stress rises, and cartilage that is loaded beyond what it was built for wears earlier.
The severity is a spectrum. Severe dysplasia is usually detected in infancy and treated then. Mild dysplasia frequently is not detected at all, and the first anyone knows of it is a patient in their thirties or forties with hip pain and a radiograph that explains why.
Symptoms.
Groin pain is the usual complaint, often with pain and fatigue over the outer hip because the abductor muscles are working harder to stabilise a joint that is less stable by shape. Symptoms typically build over years and are worse after prolonged standing or walking. Many people describe a hip that aches after a long day rather than one that hurts sharply.
Dysplasia is also a common underlying cause of a labral tear, because the labrum takes more load in a shallow socket than it was designed to.
How it is diagnosed.
A standing anteroposterior pelvis radiograph is the key investigation. Coverage is measured with the lateral centre-edge angle and related measurements. This is a straightforward assessment on a plain film, which is why dysplasia is a diagnosis that is missed rather than one that is hard to make: it is missed when nobody measures.
CT or MRI may be used to assess version and cartilage where preservation surgery is being considered.
Treatment.
In a younger patient with preserved cartilage, the definitive treatment is a periacetabular osteotomy: the socket is cut free and rotated to cover the ball properly, then fixed in the new position. It is a major operation performed by surgeons who specialise in hip preservation, and where it is appropriate it can change the natural history of the hip.
Where arthritis is already established, the socket cannot be usefully reoriented and hip replacement is the operation that helps. Replacement in a dysplastic hip is more demanding than in a normal one: the socket is shallow, the bone stock is different, leg length may need restoring, and the anatomy is often distorted by previous surgery. It is planned specifically rather than treated as a routine case.
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.
I was told my hips were fine as a baby. Can I still have dysplasia?
Yes. Screening in infancy detects the more severe end of the spectrum. Milder dysplasia frequently goes undetected and only becomes apparent when it causes symptoms in adult life.
Does dysplasia always cause arthritis?
Not always, but it is one of the strongest predictors of hip osteoarthritis in younger adults. The greater the under-coverage, the earlier arthritis tends to appear.
Is hip replacement different in a dysplastic hip?
Yes, it is more demanding. The socket is shallow and the bone stock differs, so component position, restoring the centre of rotation and managing leg length all need specific planning. It is a well-established operation, just not a routine one.
What is a periacetabular osteotomy?
An operation in which the socket is cut free from the pelvis and rotated to cover the ball properly, then fixed. It is for younger patients whose cartilage is still good, and it is performed by hip preservation surgeons rather than in this practice.
Will my children have it?
There is a familial tendency, so it is worth mentioning your diagnosis to your GP if you have children, particularly girls, firstborns, or a breech birth.
References.
- Wilkin GP, Ibrahim MM, Smit KM, Beaulé PE. A contemporary definition of hip dysplasia and structural instability. J Arthroplasty. 2017;32(9S):S20-S27.
- Lerch TD, Steppacher SD, Liechti EF, et al. One-third of hips after periacetabular osteotomy survive 30 years. Clin Orthop Relat Res. 2017;475(4):1154-1168.
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.