Hip Dysplasia in Newborns: Complete Guide to DDH

What Is Developmental Dysplasia of the Hip?

Developmental dysplasia of the hip (DDH) is a condition where the hip joint does not form properly in infants. The hip socket (acetabulum) may be too shallow, and the ball of the thighbone (femoral head) may be unstable, partially out of position, or completely dislocated. DDH affects approximately 1-3% of newborns and is 4-6 times more common in girls than boys.

The hip joint is a ball-and-socket joint where the round head of the femur (thighbone) fits into a cup-shaped socket in the pelvis called the acetabulum. In developmental dysplasia of the hip, this joint doesn't develop correctly. The condition ranges from mild hip instability to complete dislocation where the femoral head is entirely outside the socket.

DDH was previously called "congenital hip dislocation" or "congenital hip dysplasia," but the term "developmental" is now preferred because the condition can develop during the first weeks of life, not just at birth. The hip socket continues to develop and shape itself around the femoral head during infancy, which is why early treatment is so effective – it allows the joint to develop normally.

The condition can affect one hip (unilateral) or both hips (bilateral). In about half of affected infants, one or both hips are already displaced at birth. In others, the hip is unstable and can easily slip out of position but is not yet dislocated.

Types and Severity of DDH

DDH exists on a spectrum of severity. Understanding these distinctions helps parents know what to expect from diagnosis and treatment:

• Hip instability (dysplasia): The hip socket is shallow or the ligaments are loose, making the hip potentially unstable. The hip may feel "loose" on examination but is not dislocated.
• Subluxation: The femoral head is partially displaced from the socket. It can move in and out of position.
• Dislocation (luxation): The femoral head is completely outside the hip socket. This is the most severe form.

The earlier the condition is detected and treated, the better the outcome. Mild instability often resolves on its own within the first few weeks of life, while more severe cases require treatment to ensure normal hip development.

What Causes Hip Dysplasia in Newborns?

Hip dysplasia is caused by a combination of increased elasticity in the hip joint capsule and/or a shallow hip socket. Risk factors include breech presentation during pregnancy (significantly increases risk), being female (4-6 times higher risk), having a family history of DDH, and being a first-born child. The condition is not caused by anything the parents did during pregnancy.

The exact cause of DDH involves both genetic and environmental factors during pregnancy and after birth. The condition develops because of abnormal joint development, which can occur due to several interrelated factors.

Genetic Factors

There is a clear genetic component to DDH. If a parent or sibling has been treated for hip dysplasia, the risk for subsequent children is significantly higher. Studies show that first-degree relatives of affected individuals have a 12-fold increased risk of DDH compared to the general population. The inheritance pattern is complex and involves multiple genes affecting hip joint development and ligament laxity.

Some families have naturally looser ligaments (joint hypermobility), which increases susceptibility to hip instability. This genetic predisposition to ligament laxity is more common in females, which partly explains why DDH is much more frequent in girls.

Hormonal Factors

Maternal hormones, particularly relaxin and estrogen, play a role in DDH development. Relaxin is a hormone produced during pregnancy that loosens the mother's pelvic ligaments to prepare for childbirth. This hormone can also affect the baby's ligaments, making them more lax and the hip joint less stable. Female infants appear to be more sensitive to these hormones than males, which contributes to the higher incidence of DDH in girls.

Mechanical Factors During Pregnancy

The position of the baby in the uterus significantly affects hip development. Conditions that restrict fetal movement or press the legs together increase the risk of DDH:

• Breech presentation: When the baby is positioned bottom-down in the uterus, the hips are often held in an extended position that can strain the developing joint. Breech position is the strongest risk factor for DDH.
• First pregnancy: The uterus is tighter in first pregnancies, which can restrict fetal movement and increase pressure on the developing hips.
• Low amniotic fluid (oligohydramnios): Less fluid means less room for the baby to move freely, potentially affecting hip development.
• Large baby size: Larger babies have less room to move in the uterus, which can affect hip positioning.

Risk Factors Summary

The following table summarizes the main risk factors and their approximate impact on DDH risk:

How Is Hip Dysplasia Screened and Diagnosed?

All newborns are screened for hip dysplasia through physical examination within the first few days of life. Doctors use special maneuvers called the Barlow and Ortolani tests to check for hip instability. If abnormalities are found or risk factors are present, ultrasound imaging is used. The examination may look uncomfortable to watch, but it does not hurt the baby.

Early detection is critical for successful DDH treatment. Most developed countries have implemented universal newborn hip screening programs. The screening combines clinical examination with selective or universal ultrasound imaging, depending on the country's guidelines.

Physical Examination

A pediatrician or other qualified healthcare provider examines every newborn's hips within the first 48-72 hours of life. The examination includes two key maneuvers that have been used for decades to detect hip instability:

Barlow test: The examiner holds the baby's thigh and gently pushes backward while adducting (bringing together) the leg. This test attempts to dislocate an unstable hip. A positive test means the hip can be pushed out of the socket, indicating instability.

Ortolani test: The examiner gently abducts (spreads apart) the baby's legs while lifting the thigh. In a dislocated hip, the examiner may feel a "clunk" as the femoral head slips back into the socket. This test detects a hip that is already dislocated and can be reduced (put back in place).

Parents sometimes feel concerned watching these examinations because their baby may fuss. However, the tests are performed gently and do not cause pain. The momentary discomfort is from being handled, not from the examination itself.

Ultrasound Examination

Ultrasound is the primary imaging method for diagnosing DDH in infants under 4-6 months of age. It provides detailed images of the cartilaginous hip structures that cannot be seen on X-rays at this age. Ultrasound can assess:

• The shape and depth of the acetabulum (hip socket)
• The position of the femoral head in relation to the socket
• The stability of the hip during movement
• The alpha angle (a measurement of socket depth)

Some countries perform universal hip ultrasound screening on all newborns, while others perform selective screening based on risk factors or clinical findings. Ultrasound is typically performed at 4-6 weeks of age if there are concerns, as many hips stabilize spontaneously in the first few weeks.

X-ray Examination

X-rays become useful after about 4-6 months of age when the bones have calcified enough to be visible on imaging. X-rays are used for:

• Follow-up of treated patients (typically at 4 and 12 months of age)
• Diagnosis of late-detected DDH in older infants
• Assessment before and after surgical treatment

The reason X-rays are not used in the newborn period is that the hip bones are largely cartilage at birth and don't show up clearly on X-ray images.

Late Detection

Despite screening programs, some cases of DDH are not detected until later. This can happen because:

• The hip was stable at the initial examination but became unstable later
• The hip was in the correct position at birth but developed dysplasia
• Signs were subtle and missed on initial examination

Later signs that may indicate undiagnosed DDH include asymmetric skin creases on the thighs, apparent difference in leg length, limited ability to spread the legs apart, and (once walking begins) a waddling or limping gait.

How Is Hip Dysplasia Treated?

The primary treatment for DDH is the Pavlik harness or von Rosen splint, which holds the baby's legs in an outward, flexed position (the "frog-leg" position) for 6-12 weeks. This position allows the hip socket to develop properly around the femoral head. Treatment success rates are 90-95% when started within the first 6 weeks of life. Only trained healthcare professionals should put on or remove the harness.

Treatment for DDH depends on the age at diagnosis and severity of the condition. The goal of all treatment is to position the femoral head deep in the hip socket so that the joint can develop normally. The younger the infant at the start of treatment, the shorter the treatment duration and the better the outcome.

Pavlik Harness Treatment

The Pavlik harness is the most widely used treatment for DDH in infants under 6 months of age. Named after the Czech physician Arnold Pavlik who developed it in the 1950s, this soft brace holds the hips in a flexed (bent) and abducted (spread apart) position while allowing some movement.

The harness consists of chest and shoulder straps connected to leg straps that hold the legs in position. It is worn full-time (24 hours a day) initially, and the duration of treatment depends on the severity of the dysplasia and response to treatment, typically 6-12 weeks.

Key principles of Pavlik harness treatment:

• Proper fitting is essential: The harness must be fitted by a trained healthcare provider. Incorrect positioning can lead to treatment failure or complications.
• Never remove the harness at home: Parents should not take the harness off. This is crucial for treatment success.
• Regular follow-up: The baby will have frequent appointments (often weekly initially) to check harness fit and monitor hip position with ultrasound.
• Harness may be replaced as baby grows: As the infant grows, larger harnesses will be needed.

Von Rosen Splint

The von Rosen splint is an alternative abduction device used in some regions, particularly in Scandinavian countries. It is a rigid splint that holds the hips in a similar position to the Pavlik harness. Like the Pavlik harness, it is worn continuously and should only be applied by healthcare professionals.

Practical Tips for Parents During Harness Treatment

Living with a baby in a Pavlik harness requires some adjustments, but most families adapt quickly:

• Clothing: Use clothes one size larger than normal to accommodate the harness. Choose garments that are easy to put on and remove. Dress the baby in a soft cotton onesie or undershirt beneath the harness to protect the skin.
• Diapering: Diapers go under the harness. You can change diapers without removing the harness.
• Feeding: Hold the baby in a sitting or semi-reclined position rather than lying flat. This is more comfortable with the legs in the abducted position.
• Bathing: The baby typically comes to the orthopedic clinic periodically for supervised bathing, where the harness is briefly removed. Some providers allow home bathing with specific instructions.
• Car seats: Many babies can still use a car seat with the harness if the legs fit. Consult your healthcare provider about car seat compatibility.
• Sleep: The baby can sleep on their back as normal. The harness position is safe for sleep.

Treatment for Late-Diagnosed DDH

When DDH is diagnosed after 6 months of age, or when Pavlik harness treatment fails, more intensive treatment is needed:

Closed reduction: Under general anesthesia, the orthopedic surgeon manually repositions the femoral head into the socket without making an incision. An arthrogram (dye injection) may be used to confirm proper positioning. After closed reduction, the baby wears a spica cast (a hard cast that covers the torso and affected leg(s)) for several months.

Open reduction: If closed reduction cannot achieve proper positioning, surgery is performed to remove obstacles (such as tight tissues) and place the femoral head in the socket. This is followed by spica casting.

Osteotomy: In older children or severe cases, bone-cutting procedures may be needed to reshape the socket or femur to achieve stable hip positioning.

What Happens After Treatment?

After the harness or splint is removed, children are followed with regular examinations and X-rays, typically at 4 and 12 months of age, and sometimes longer. The legs may naturally remain in an outward position for a while after treatment, but this resolves on its own without any intervention or physical therapy needed.

Monitoring after treatment is essential to ensure the hip develops normally and to detect any problems early. The follow-up schedule typically includes:

• Regular clinical examinations: The doctor checks hip stability and range of motion
• X-rays at 4 months: To assess hip development after treatment
• X-rays at 12 months: To confirm normal development
• Additional follow-up: Some centers continue monitoring until age 2-4 years or even until skeletal maturity

After the harness is removed, parents often notice that their baby's legs remain in an outward, frog-like position. This is completely normal and gradually resolves over the following weeks as the baby gains muscle control and freedom of movement. There is no need for physical therapy or exercises to correct this – it happens naturally.

Long-term Outlook

For the vast majority of children treated early for DDH, the long-term outlook is excellent. The hip develops normally, and there are no lasting effects. These children can participate fully in sports and activities without restrictions.

Late-diagnosed or inadequately treated DDH can lead to problems including:

• Hip pain during childhood or adolescence
• Waddling gait or limping
• Leg length difference
• Early-onset hip arthritis (potentially requiring hip replacement at a young age)

These complications underscore the importance of newborn screening and early treatment.

What Are the Potential Complications?

Complications from DDH treatment are uncommon when performed correctly. The main concern is avascular necrosis (damage to blood supply of the femoral head), which can occur if the hip is held in an extreme position. Untreated DDH leads to more serious problems including chronic hip pain, abnormal gait, and early-onset arthritis requiring hip replacement.

Complications of Treatment

When treatment is performed correctly by experienced providers, complications are rare. However, potential issues include:

Avascular necrosis (AVN): This is the most serious treatment complication. It occurs when blood supply to the femoral head is compromised, potentially damaging the growing bone. Risk factors include extreme hip positioning and late age at treatment. Proper harness fitting and positioning minimizes this risk.

Treatment failure: The Pavlik harness is not successful in all cases, particularly for hips that are completely dislocated or in older infants. Failed harness treatment may require more invasive treatment such as closed or open reduction.

Residual dysplasia: Some children may have persistent shallow hip sockets despite treatment. This requires ongoing monitoring and potentially additional intervention.

Consequences of Untreated DDH

Without treatment, DDH causes progressive hip joint abnormality that worsens with age:

• Abnormal gait: Children with bilateral (both hips) DDH develop a waddling walk. Those with unilateral (one hip) DDH will limp.
• Leg length difference: The affected side is shorter, causing pelvic tilt and gait abnormality.
• Hip pain: Usually develops in adolescence or young adulthood as the abnormal joint wears.
• Early osteoarthritis: The abnormal joint surfaces lead to premature wearing of the cartilage, often requiring hip replacement surgery at a young age (30s-50s).

Does Treatment Affect My Baby's Development?

Research consistently shows that treatment with harness or splint does not negatively affect children's physical, emotional, or developmental outcomes. Babies adapt remarkably well, and parents report that after a brief adjustment period, their babies seem comfortable in the harness. There is no evidence of psychological harm from wearing a harness in infancy.

One of the most common concerns parents have is whether the harness will affect their baby's development or cause emotional distress. The evidence is reassuring:

Motor development: Studies tracking children treated for DDH show that they reach motor milestones (sitting, crawling, walking) at the same ages as their peers. Any brief delay during treatment is quickly caught up.

Emotional development: There is no evidence that wearing a harness causes any psychological harm. Babies are remarkably adaptable, and for them, the harness simply becomes their normal experience.

Parent-child bonding: While the harness may initially feel like a barrier, parents quickly learn to hold, feed, and care for their baby comfortably. Skin-to-skin contact remains possible. The treatment period is temporary, and most families look back on it as a manageable challenge.