The hip joint is a large ball and socket joint, the socket being the acetabulum of the pelvis and the ball being the head of the femur (thigh bone). The hip joint has a large weight bearing surface area and subsequently is a very stable joint and not prone to dislocation. The bone surfaces of the joint are covered by a layer of cartilage which allows the joints to glide freely and then an additional cartilaginous structure called a labrum. The labrum increases the surface area of the joint, helps in shock absorption and suctions the whole joint together.
There are many names for hip dysplasia including Developmental Dislocation of the Hip (DDH), Acetabular Dysplasia, Developmental Dysplasia of the Hip (DDH) and Congenital Dislocation of the Hip. Put simply Hip Dysplasia is when the Hip joint is not formed correctly. There are many different variations of this which include
- A shallow acetabulum
- An acetabulum that faces the wrong direction to support the femoral head
- Irregularity to the femoral head and the angle at which it faces the acetabulum. Coxa Vara where the angle is too small and Coxa Valga where the angle is too large.
- Or a very uncommon type of dysplasia found in a particular family group where the femoral head is flat
We must also bear in mind that there are varying degrees of hip dysplasia seen in the population from very obvious forms of the disease seen in infants to slight variations picked up later in life which may have contributed to osteoarthritis.
So how does this Happen?
Congenital Hip Dysplasia is when a baby is born with the hip deformity. It is largely unknown why this occurs and there are some genetic links that have been shown to increase the risk of the disease.
Acquired or developmental hip dysplasia is when other factors influence the normal development of the hip joint after birth such as particular birthing positions and sustained positions the baby is held in. It is important to consider that in many circumstances it may be the influence of both congenital and acquired factors.
So what if my baby has hip dysplasia?
Every baby born in Australia should receive some kind of neonatal screening for hip dysplasia. This is usually conducted in the form or the Ortolani or Barlow manoeuvre (tests where the baby’s hips are moved around to reveal clicking or clunking) and if positive will then be then further assessed using ultrasound or x-ray. If hip dysplasia is then confirmed on imaging, the baby is put in a rigid hip brace called a Pavlic harness for usually around 12 weeks to allow the immature bone around the hip sockets correct the deformity. While this process is often very confronting for parents it is something that babies adapt quite well to and most of time results in a resolution of the deformity.
When Hip Dysplasia isn’t picked up at birth
Due to varying degrees of hip dysplasia and human error there are always people who slip through the cracks of the neonatal screening. Hip dysplasia reduces the stability of the hip joint and its capacity to cope with stress and load. Often weight bearing occurs on parts of joint that are not fully equipped to take the weight. This often then leads to labral tears and cartilage loss which then become painful and causes that individual to present to a medical practitioner.
On examination an individual suffering from hip dysplasia will likely experience pain and or clicking or clunking with hip joint screening. Further confirmation then needs to be made via x-ray and or CT/MRI. These scans should also be interpreted by a specialist who can piece them together with the patient’s history before making a clinical diagnosis.
Conservative management of hip dysplasia in adolescents and adults includes education and management plans around reducing the load through the joint and preventing further damage. This may include avoiding end range hip positions, avoiding high impact sports or repetitive stress sports and making the muscles around the hip joint as strong as possible to best support the hip. It is however unlikely in cases where chondral loss is present that this approach will be enough and many will eventually go on to have surgery.
So what are the surgical options?
Labral tears in individuals with hip dysplasia are very common due to altered mechanics around the joint. Arthroscopic repair if these structures especially without properly repairing or reinforcing the joint capsule are often unsuccessful or only provide short term relief as the underlying reason why the hip has a labral tear has not been addressed.
For individuals under the age of 40 where the acetabulum is too shallow and does not support the femoral head correctly a Periacetabular Osteotomy (PAO) may be performed. This type of surgery is typically only appropriate in the absence of arthritis and cartilage wear as it aims to normalise the load across the hip joint and reduce the severity, likelihood and onset of arthritis. A PAO is performed by cutting a section of bone out of the acetabulum and fixing it in a new position with the aid of screws. This aims to deepen the socket and change the angle at which it faces to better support the femoral head. Due to the bony disruption there is a significant rehabilitation which takes about 6 months.
In more severe cases where articular cartilage has already been worn through a Total Hip Replacement (THR) may be required. In this operation the head of the femur and the acetabulum are both replaced with artificial devices. Despite the severity of the operation the recovery is quite fast with clients usually up and about in 2 weeks. Full rehabilitation of the joint and the muscles that support it does still take several months. Posterior and lateral approaches cut significant amounts of muscle and have a period of 3 months where certain hip positions need to be avoided to reduce the risk of dislocation. Anterior approaches which are becoming increasingly more common do not have to cut through as much muscle and subsequently have a faster return to activity and less hip precautions.
Lindsay Christie (APAM)
I must firstly thank Orthopaedic Surgeon Dr David Agolley for his time discussing this topic with me as some of his opinions I have written into this Blog.
Derotation, H. (1972). Problems in the early diagnosis and management of congenital dislocation of the hip.
Nelitz, M., Guenther, K. P., Gunkel, S., & Puhl, W. (1999). Reliability of radiological measurements in the assessment of hip dysplasia
Hip Dysplasia. (N.D.) Retrieved May 25, 2016, from https://en.wikipedia.org/wiki/Hip_Dysplasia
Gillingham, B. L., Sanchez, A. A., & Wenger, D. R. (1999). Pelvic osteotomies for the treatment of hip dysplasia in children and young adults.Journal of the American Academy of Orthopaedic Surgeons, 7(5), 325-337.
GANZ, R., KLAUE, K., VINH, T. S., & MAST, J. W. (1988). A New Periacetabular Osteotomy for the Treatment of Hip Dysplasias Technique and Preliminary Results. Clinical orthopaedics and related research, 232, 26-36.