Understanding Hip Dysplasia

How is hip dysplasia diagnosed?

• Doctors use a combination of physical exams and imaging such as ultrasound or x-rays to diagnose hip dysplasia. Standard practice in the developed world is to do hip exams for newborns and babies for hip dysplasia at well-baby checkups.
• Babies are at increased risk for hip dysplasia in the following situations:The baby is a twin or multiple, or was in a breech position at birth.
• There is a family history of hip dysplasia.
• The doctor is concerned about the results of the physical exam.
• There are signs and symptoms of a possible hip problem, such as a limp in a child of walking age.

The American Academy of Pediatrics recommends an ultrasound study at six weeks of age for almost all baby girls who were in the breech, or bottom-first position. Babies with other risk factors may also benefit from an ultrasound, especially when the pediatrician has any concerns about the examination of the hips. An x-ray at four months of age or older is sometimes recommended.

Hip dysplasia can be difficult to diagnose, especially if it is bilateral (both hips are affected) because the hips are symmetrical. The hips could be a little loose, but otherwise fine, and then get progressively worse as the baby gets older, especially if they slip farther out of the socket when the baby is relaxed, such as while sleeping. When both hips are dislocated, the exam is symmetrical.

When a baby with dislocated hips walks, he or she has a waddling gait that is a little more exaggerated than a normal toddler gait. If only one hip is affected, it is easier to spot the affected hip because it can be compared to the other hip. In some cases, hip dislocations have developed in older babies even when the infant exam was normal and the ultrasound was normal at six weeks of age. The cause of these late developing cases is unknown.

X-Ray Screening

For babies 4 months of age or older and children, x-rays are performed when hip dysplasia is suspected. This is necessary to make the diagnosis or to be sure the hip is normal.

During treatment x-rays can reveal the progress of the hip as it improves. Most children do not need surgery, but for those who do, an arthrogram (x-ray dye injected into the hip joint) at the beginning of the surgery can help the surgeon decide exactly what needs to be corrected.

Ultrasound

An ultrasound study in young infants is performed when hip dysplasia is suspected. This is necessary to make the diagnosis or to be sure the hip is normal. There are angles that are measured during the examination. The one that is used the most to help guide treatment is the alpha angle. This angle is considered normal if it is more than 60 degrees. Mild dysplasia is present when the alpha angle is between 43-60 degrees. Dysplasia is severe when the alpha angle is less than 43 degrees. During the ultrasound examination, the hip is also examined for stability in the same manner as the Barlow test, but the ultrasound is used to see if the hip is unstable instead of relying on the feel of the doctor. Many babies have slightly loose hips so this can be very difficult to interpret. The images can generally show how far out of the socket the hip will move. Of course, this depends on how hard the examiner pushes. In general more than 50% of the ball should remain in the socket. When the number is less than 45% then there is instability. The instability is much more common in newborn infants and the ligaments get tighter with age. Some instability in a six-week old infant is not very uncommon. Sometimes this is treated and sometimes it is observed with a repeated ultrasound study at age three months. Other imaging methods that may be used for babies or children are x-rays and arthrograms.

Infant Signs and Symptoms

Hip dysplasia in babies is most frequently discovered at the time of newborn examinations by physicians but dysplasia and dislocation can develop after this time in some children. This is why hip dysplasia is greatly considered developmental. It is also hard to detect because hip dysplasia is known as a “silent” condition. It does not cause pain in babies and doesn’t normally prevent them from learning how to walk at a normal age.

Signs that parents might notice include:

Asymmetry

Asymmetrical buttock creases can suggest hip dysplasia in infants but, like a hip click, an ultrasound or x-ray study will need to be done to determine whether the hips are normal or not.

When a baby’s hip dislocation is present for several months, the hips gradually lose range of motion and the leg appears shorter because the hip has migrated upward.

Hip Click

What is a “hip click”?

A “hip click” refers to an audible “click” or “pop” that occurs when a baby’s hips are being examined. When an infant has a “hip click” it does not mean that a baby has hip dysplasia. While some infants that have a hip click will be diagnosed with hip dysplasia, there are babies with hip clicks that have normal hips.

Why would a baby with normal hips “click”?

There are many ligaments inside an infant’s hip joint that can make snapping or popping noises in certain positions for many different reasons as the baby develops. A “hip click” is just one sign that hip dislocation may be present in an infant. Further examinations and tests will be needed to know why an infant’s hip is clicking.

So what does a “hip click” mean?

An infant that has a hip click should be monitored for hip dysplasia. It is important for babies to have regular hip examinations during the first year of life. There are documented cases where the hips were normal at birth but became dislocated in the first few months of life as the baby developed physically. Even with a careful physical examination, hip dysplasia can be difficult to detect in newborn infants. Further tests such as ultrasounds and X-rays are normally needed to make a diagnosis for hip dysplasia or to be sure the hip is normal.