Avascular necrosis describes the death of bone tissue that occurs when the blood supply to an area of bone is cut off. It causes severe damage to the bone and is also known as ischemic bone necrosis, aseptic necrosis, bone infarction and osteonecrosis.…
Developmental dysplasia of the hip
What is developmental dysplasia of the hip?
Developmental dysplasia of the hip refers to a range of conditions that can affect the development of the hips in infants or young children. Other names can also be used to describe this condition, including congenital dysplasia of the hip, or congenital dislocation of the hip.
The hip joint is a ball-and-socket joint, in which the top of the thighbone (femur) forms a ball that fits into the acetabulum (hollowed-out socket) of the pelvis. The ball of the femur is attached to the socket of the pelvis via ligaments.
Developmental dysplasia of the hip can occur across a range of severity, from minor looseness or laxity of the ligament that holds the femur in the socket (known as subluxation), through to complete dislocation (known as high dislocation), where the femur is located entirely outside the socket. In between the extremes, there may be partial dislocation of the femur because the socket is too shallow, or the ligament is not tight enough to hold it in place properly (known as low dislocation).
It is easier for a baby's or infant's hip to become misaligned or dislocated because their hip sockets are developing and are still made of soft and pliable cartilage. Due to the position of the baby's hip in relation to the mother's spine while the baby is in utero, the left hip is affected the majority of the time.
Developmental hip instability, which includes dysplasia, is estimated to affect about 4-20 babies in every 1000 births.  It has a higher rate of incidence in females and in cultures that keep the hips of their infants tightly swaddled.
Developmental dysplasia of the hip is referred to as a multifactorial trait, meaning that there are many factors that contribute to the development of the condition. These factors are typically both genetic (inherited) and environmental. There is not one specific cause for most cases of developmental dysplasia of the hip.
Factors that can put a baby at higher risk of having developmental dysplasia of the hip include:
Signs and symptoms
Developmental dysplasia of the hip generally only affects one side of the body and is not usually associated with pain. There may be no obvious signs that an infant has developmental dysplasia of the hip, but during routine examination at birth, medical professionals look for:
- An inability to move the thigh outward at the hip;
- A loud clunk sound when the doctor feels around (palpates) the legs and hips;
- Different lengths of the legs, and;
- Asymmetrical folds of skin in the thigh or around the groin and buttocks.
In older infants, there may be:
- Less mobility of the hip joint;
- Delayed physical movement (sitting, crawling and walking);
- Legs of different lengths, and;
- Asymmetrical level of knee joints, with one sitting lower than the other.
Methods for diagnosis
Physical examination at birth
Babies are routinely examined at birth to ensure their hip joints are in the correct position. To check their hips, the baby is put onto their back and their legs rotated to test hip joint mobility. Each hip is examined separately.
Although there is not a gold standard test, the Barlow and Ortolani tests are commonly used. These tests are used to detect if the thighbone (femur) is sliding in and out of the socket. These tests are performed by a doctor, with the baby lying on his/her back as the hips are gently moved. If the hip feels as though it could be pushed out of the socket, this is a sign of hip instability and is a positive Barlow test. As the hips are pushed further apart, if the femur head seems to slide back into the socket, usually with an audible clunk, this is a positive Ortolani test. If the tests are inconclusive on examination at birth, the baby may require a follow-up examination within 2-3 weeks.
In older infants and young children
In some cases, there may not have been any problems observed at birth and the problem may not become apparent until the baby is older, or until they start to walk. For diagnosis of infants and young children, a Galeazzi test (also known as the Allis test, or sign) may form part of the diagnosis. The child lays on their back, with their feet flat on the doctor's couch and their knees bent. If one knee is lower than the other, this may indicate a dislocated hip on the lower side.
Since this condition can develop over some time, regular examinations can help in early diagnosis, to help avoid problems developing later in life.
Imaging scans for all infants at birth is not recommended. However, infants with risk factors or positive clinical examination findings, imaging scans are used to confirm the diagnosis and assess the degree of dislocation. For infants less than six months of age, an ultrasound of the hips is the preferred test. For children six months of age or older, X-ray of the hips is the preferred test.
Types of treatment
The type of treatment may vary, depending on the age of the child and the severity of their condition. The aim of treatment is to reposition the femoral head into the socket to ensure normal hip joint development.
For treatment of babies up to the age of six months, a Pavlik harness is used to hold their hips in place. The Pavlik harness is rarely successful in treating children older than six months.
This harness allows minor leg movement and is usually worn for 4-8 weeks. During the treatment, a medical professional will regularly review the baby and the harness to ensure it is correctly fitted and to examine the baby's hips. At the end of the treatment period, an ultrasound is performed to assess the hip placement.
There is a very high success rate for treating mild cases of dysplasia with a Pavlik harness. Although it is uncommon, if the hip is not held in its correct position, there is the chance of the baby developing avascular necrosis (the death of bone tissue due to a lack of blood supply).
Closed reduction and hip spica
If the Pavlik harness is not effective, the next stage of treatment involves manipulating the hip into the correct position. The procedure is carried out under anesthetic and once the hip is positioned correctly, a special cast, called a spica cast, is applied to keep the hip in the correct anatomical position. The position of the hip is confirmed with either a magnetic resonance imaging (MRI) or computerized tomography (CT) scan. The cast is kept on for at least 12 weeks.
If a child is much older when their condition is diagnosed, or if other treatment has proven to be ineffective, surgery may be performed. During this procedure, the hip joint is surgically exposed and the femur is repositioned into the hip socket. Tight muscles and tissues surrounding the hip joint are divided and loosened, and then gently tightened once the femur is positioned correctly in the socket.
If the condition has not responded to more conservative treatments, further surgery may be performed to alter the hip socket or realign and shorten the femur.
- Children with a spica cast may have delayed walking, but once the cast is removed, the hip develops normally, and;
- The Pavlik harness may cause skin irritation where the straps touch the body, or a difference in leg length.
Untreated development dysplasia of the hip can lead to:
- Avascular necrosis of the hip, and subsequently arthritis of the hip in the long-term;
- Unstable knee joints, and;
- Abnormal gait or limp.
Most babies born with developmental dysplasia of the hip can be successfully treated without recurrence of hip problems later in life. But in some cases, they may develop arthritis in their affected joint when they are older.
This condition cannot be prevented. However, by ensuring your child attends regular medical check-ups, early identification can mean they receive appropriate treatment with very good outcomes.
Many parents find swaddling can provide comfort for their baby, reduce crying and help them to settle. However, swaddling a baby during their first few months of life can increase the likelihood of developing hip dysplasia.