Hip joint ultrasound in babies for the detection of developmental dysplasia of the hip – a screening test that should be performed on everyone!

What is DDH (Developmental Dysplasia of the Hip)?

This is a disorder in the development of the hip joint.
The hip joint is a joint that is built in the shape of a ball that is found in a socket. Sometimes, a developmental problem can arise that causes a mismatch between the ball part of the joint and the socket part. The socket (which is part of the hip bone) tends to be too shallow and the ball (part of the thigh bone) sits within it in an unstable way. As a result, the head of the thigh bone can sit partly, or entirely, outside the socket.
This condition obviously affects the proper function of the joint and leads to characteristic signs and symptoms, as you will see below.

What are the different causes of DDH?

Similarly to many other things in medicine, we don’t always know what the cause of DDH is. Seemingly, there are many different contributing factors, both genetic and environmental that can lead to this developmental problem.
What we do know is that there are risk factors that increase the risk of developing DDH, including:
# First birth
# Female sex
# Breech position
# Reduced amniotic fluid
# Multiple fetuses (twins, triplets, etc.)
# Family history – a family member that had a similar problem

However, having said all this, it is important to keep in mind that about half of the children who have DDH do not have a single known risk factor.
Another thing we know is that there is an association between DDH and other congenital defects such as metatarsus adductus (a congenital distortion of the feet) and torticollis. This is an important piece of information because it means that if one of these disorders is detected in an infant, the chances of finding an additional one increases significantly (about 20% of children have a combination of 2 or more of the above disorders).

What is the prevalence of DDH?

This is quite a common condition, that occurs in about 7-8 out of 1000 newborns.
It is important to note that this condition can occur during fetal life but also in the first year of life after the baby is born.

What are the signs and symptoms of developmental dysplasia of the hip?

Remember how we said that the problem is an abnormal hip joint where the head of the thigh bone (femur) does not sit in a stable way in the socket that is part of the hip bone? Well, what happens as a result depends on the severity of the disorder, and includes several symptoms:
– Asymmetry in the folds of the thigh and/or buttocks.
– Limited ability to spread the legs.
– One leg can seem to be shorter.
– In children who are able to walk, there can be a limp.

Since DDH has different degrees of severity, as you will see below, the milder degrees will actually not have any signs or symptoms and you will only be able to detect the condition by performing imaging studies such as hip ultrasound or an x-ray at an older age.
Our goal is obviously is to detect the condition as early as possible, and not at an older age.

How is DDH diagnosed?

The diagnosis is made by taking into consideration the relevant risk factors, imaging findings, physical examinations, and auxiliary tests. Again, mainly hip ultrasound.
Physical examination – because this is a developmental problem that could arise during fetal life, in some of the cases the condition can be suspected already at the nursery, prior to discharge or at the baby’s first visit to the pediatrician’s office.
During a physical examination performed by a physician you may be able to see some of the signs mentioned above including limited spreading of the legs, asymmetry in the folds, sometimes you can hear a click when moving the hip joint (due to rough movement of the ball that is found outside the socket) and all kinds of other tricks that experienced physicians play to try and get an impression of whether there is a dislocation and whether it can be reduced.
Again, it is important to remember that when the condition is not severe the physical examination can be completely normal. Furthermore, it is important to keep in mind that because this problem is not always present at birth but develops throughout the first year of life, it is important to have a physician routinely examine the hip joint when visiting and whenever the condition is suspected – an orthopedist should be seen.
Auxiliary tests – as mentioned above, the most common test is hip ultrasound imaging test. It uses the same ultrasound machine that you are familiar with from other tests and from pregnancy. Of course, it is not painful, nor does it expose the baby to radiation.
During the exam the orthopedist demonstrates the structure of the joint, measures the angles between the different parts of the head of the femur and the socket and is able to tell whether the structure is normal. If it is not normal, the degree of severity can be determined (commonly done by using a graph and giving a grade between 1-4 along with a letter) and from here on the appropriate treatment can be chosen. There is a need for a skilled and experienced professional to perform the exam, just like for any other medical exam.
Fortunately, we have a chapter on our website about hip ultrasounds, written from the point of view of a radiologist, you can find it in the following link.
In children that are over the age of one year, ultrasounds are less efficient and therefore x-rays of the hip are more commonly used to assess for the presence of the characteristic signs in the hip.

Should ultrasound imaging be performed on all neonates or only those at high risk of developing the disorder?

In some countries in the world, hip ultrasound is recommended as a screening test for all neonates in the world whereas in other countries it is only recommended for those who are at high risk.
What are the considerations against performing this screening test on everyone? Possibly because of a concern for overdiagnosis of borderline cases, where the purpose of treatment is unclear, or maybe because it would oversaturate orthopedists with work deeming them too busy to provide service for those who truly need them, etc. What is definitely not arguable is the need for a good physical examination performed by a pediatrician prior to discharge from the nursery, and of course routine examinations during the first few months of life. In addition, it is important to refer to a skilled orthopedist whenever in doubt, whenever there are questions or in the presence of any risk factors.
However, since the physical examination can be completely normal in some cases, there can exist different degrees of severity, and the condition can develop without any risk factors and following birth – many specialists including myself, strongly believe that everyone should get a hip ultrasound done on their neonate during their first few weeks of life, even in the absence of risk factors.

When should hip ultrasound imaging be performed on a neonate?

If there are any sings of imbalance of the hip joint following birth, an ultrasound should be performed as soon as possible.
If there are no such signs, the right timing of the ultrasound is as soon as possible and preferably closer to age 4 weeks.
Since the test needs to be booked in advance, I always recommend that parents book it as soon as the infant is born, despite the numerous other tasks they have to fulfil during this time.
In addition, as mentioned above, this condition can develop over time and may not be detected during birth. Therefore, a physical examination examining the stability of the hip joint should be performed at the pediatrician’s office during every visit in their first year of life.

What is the treatment for DDH?

The treatment varies depending on the age at diagnosis, the severity of the condition and the accompanying medical conditions.
The purpose of the treatment is to bring the head of the femur to the right position in the hip, and by doing so to force the baby’s soft tissue to develop into a normal hip joint structure.
How is this done?
In general, treatment of a baby under the age of 6 months is done with the help of a harness that keeps the thighs spread apart (see the example below of the Pavlik harness, even though there are other types as well).
Nowadays, the use of double diapers is not applicable. It was applicable back in the day when reusable cloth diapers were used and other options were unavailable.
Pavlik Harness – this is a type of harness that is meant to bring the head of the femur to the right position in the hip joint. One of its important benefits is that it allows a certain degree of movement of the legs and hip joint, which allows the development and strengthening of the structures surrounding the joint so that the socket part can deepen.
This harness is to be worn for 23 hours per day in the first few weeks and afterwards only during sleep time, until a normal hip joint is obtained (or the use of it is stopped due to lack of improvement). In the beginning of the course of treatment, the child is followed up once every 2 weeks, and once the straps are taken off, they continue to be monitored to ensure proper development of the joint. It is challenging and difficult but if the condition is diagnosed early and treated early, there is a 95% success rate, and this is why it is very important to try and detect it as early as possible.
Hip surgery and spica cast – If the Pavlik harness fails to obtain adequate results, the next stage is a hip joint examination performed under anesthesia (that means in an operating theater), surgical reduction of the hip joint into the correct position and then fixation using a spica cast (a cast that looks like a pair of pants that keep the thigh spread apart). The cast is kept for a few weeks to months and every few weeks it’s taken off and the stability of the joint is reassessed. Surgical reconstruction is rare if the condition is diagnosed and treated in the first few weeks of life.
However, if it is only detected later in life, most children will need to undergo surgery.

Does DDH have any implications for the future?

The good news is that success rates are about 95% in children that are diagnosed and treated early. Treatment leads to normal development of the hip joint, without any pain or any sort of functional limitations in the future.
In children that had a delay in diagnosis or treatment or if the problem is part of a series of additional medical disorders, the chances of success are significantly lower, surgeries are often required (sometimes more than one), and the result is an effect on the function of the joint and leg, accelerated wear and tear and often a need for hip replacement at an early stage in life.
If the condition is deprived of good medical care – the child will suffer from pain, functional limitations, and a discrepancy in leg length. Detection is simple and early treatment is very successful.
In summary, DDH is a congenital disorder that is relatively common and can play a significant role in a child’s future. The key to success is early detection and treatment, which lead to high success rates leaving no residual damage. Therefore, one must keep a high index of suspicion. I recommend hip ultrasounds and orthopedist examinations for all newborns, especially if there are risk factors or abnormal findings on physical examination.
Good luck.