OVERVIEW

What is hip dysplasia?

Hip dysplasia refers to a range of conditions related to abnormal development of the hip joint, including limited abduction in infants and asymmetrical gait in young children.

The hip joint is a "ball-and-socket joint": the rounded head of the femur (ball) fits into the acetabulum (socket) of the pelvis, hence its name.

In hip dysplasia, the socket does not form properly, resulting in excessive joint looseness. The ball can easily slip out of the socket, and if it completely dislocates, the condition is called "dislocation," while treatment is termed "reduction."

How common is hip dysplasia?

Hip dysplasia typically occurs in infants and children, with an incidence rate of approximately 0.1%–0.2%. Studies suggest that up to 40% of newborns may exhibit hip looseness or immaturity, but 90% of these cases resolve spontaneously.

Which areas are commonly affected by hip dysplasia?

The contact area between the femoral head and the acetabulum.

Which medical department should be consulted for hip dysplasia?

Orthopedics or orthopedic surgery.

SYMPTOMS

What are the common manifestations of hip dysplasia?

• Hip dysplasia in infants usually does not cause obvious symptoms.

• In toddlers and older children, hip dysplasia can cause symptoms such as one leg appearing shorter or turned outward, and may lead to limping, characterized by an uneven gait while walking.

• Additionally, activity-related pain in adolescents and the development of adult osteoarthritis are clinical features of hip dysplasia.

How does hip dysplasia develop?

During the neonatal period, ligament laxity makes the developing hip joint susceptible to external mechanical forces such as swaddling. If these forces persist, they can lead to eccentric contact of the hip joint.

Over time, the likelihood of the femoral head relocating into the acetabulum decreases, resulting in dysplastic changes in the hip joint. Without active treatment, activity-related pain may occur in adolescence, and adult osteoarthritis may develop in adulthood.

What serious consequences can hip dysplasia cause?

If left untreated, patients with hip dysplasia may experience progressively worsening functional disability, pain, and accelerated osteoarthritis over time.

CAUSES

What causes hip dysplasia?

Hip dysplasia results from abnormal contact between the acetabulum and the femoral head, involving various genetic and environmental factors (both in utero and after birth).

• In late pregnancy, the hip joint is susceptible to mechanical forces that displace the femoral head from the center of the acetabulum. Factors restricting fetal mobility (including breech presentation) amplify these forces, leading to eccentric contact between the femoral head and acetabulum.

• During the neonatal period, ligamentous laxity makes the developing hip joint vulnerable to external mechanical forces. Keeping the hip in an extended position (e.g., swaddling) can cause eccentric contact.

If these factors persist, abnormal hip contact leads to anatomical changes. Over time, the likelihood of the femoral head relocating into the acetabulum decreases.

What are the risk factors for hip dysplasia?

Female infants, breech presentation, oligohydramnios, conditions restricting fetal mobility (e.g., swaddling), and family history.

Is hip dysplasia hereditary?

There is a genetic component (possibility).

DIAGNOSIS

What tests are needed for hip dysplasia?

• Doctors typically examine for hip dysplasia by moving the child's legs with the hip joint as the center, while also checking if both legs appear symmetrical and equal in length. Infants with uncertain physical examination results or those with risk factors but normal physical exams may undergo imaging tests that visualize the inside of the body for diagnosis.

• Imaging tests include ultrasound and X-rays. These tests can create images of the body's internal structures.

• For infants under 4–6 months of age, ultrasound is usually the preferred diagnostic method; X-rays are more suitable for infants older than 4–6 months.

Which conditions are easily confused with hip dysplasia?

It is easily confused with coxa vara.

Coxa vara is a condition where the angle between the femoral neck and the femoral shaft is less than 120°, causing elevation of the greater trochanter.

Is hip dysplasia screening required for all infants?

No. Infants with risk factors, such as a family history, can inform their doctor for ultrasound screening. In general, clinical assessments for hip dysplasia are performed at birth and during each pediatric health visit.

TREATMENT

Can hip dysplasia heal on its own?

• In untreated infants with hip dysplasia, 90% will become normal shortly after birth as physiological laxity decreases and the femoral head and acetabulum grow.

• Only a small number of patients require treatment, depending on the patient's age and the severity of the condition.

How is hip dysplasia treated?

• Infants under 2 weeks old generally do not receive immediate treatment, as hip laxity can be normal in newborns and may sometimes resolve on its own. Regular check-ups are recommended to determine whether the condition subsides or persists.

• Treatment for infants aged 2 weeks to 6 months usually involves wearing a device to keep the hip in place for proper bone growth. The infant typically needs to wear the device continuously for 2–3 months.

• Treatment for infants older than 6 months and children generally involves manually or surgically repositioning the hip bones into the correct position. The child then wears a cast for 3–4 months to maintain the hip in place.

Does hip dysplasia require hospitalization?

Hospitalization is generally not required, except for surgical patients.

What are the common risks of surgical treatment for hip dysplasia?

• The main surgical risks of open reduction for children aged 6–18 months include redislocation, osteonecrosis, infection, scarring, and joint stiffness.

• The main surgical risks of open reduction for children aged 18 months and older include osteonecrosis, proximal femoral growth disorders, and residual dysplasia.

Can hip dysplasia cause long-term problems?

This depends on the child's age at onset and the severity of the condition. Many infants with this condition do not experience long-term hip problems. Some children may later develop hip pain or damage, especially those with late-onset cases in later childhood.

DIET & LIFESTYLE

What are the precautions after surgical treatment for hip dysplasia?

• Handle the child gently and steadily when moving them.

• Comfort the child promptly if they cry due to discomfort.

• Ensure good ventilation in the room, maintain moderate temperature and humidity, keep the bedding clean, dry, smooth, and free of wrinkles or debris, and provide proper care for urination, defecation, and perineal hygiene.

• Prevent pressure sores.

• After cast removal, assist the child with hip joint functional exercises as instructed by the doctor.

Is follow-up necessary for hip dysplasia?

Yes, and long-term follow-up as advised by the doctor is essential.

Children undergoing treatment for hip dysplasia should have regular X-ray examinations until skeletal maturity to ensure normal hip development and check for late complications or sequelae. The frequency of long-term follow-ups will be determined by the doctor.

Are there any sequelae after treatment for hip dysplasia?

Yes. Possible sequelae include recurrent or residual dysplasia, osteonecrosis, and osteoarthritis, making regular follow-ups crucial.

PREVENTION

Can hip dysplasia be prevented?

There is currently no way to prevent it, but the risk can be reduced by eliminating risk factors, such as providing sufficient space for hip and knee flexion and free movement of the lower limbs.

How to prevent recurrence of hip dysplasia?

After successful treatment of hip dysplasia, up to 20% of children may still develop residual hip dysplasia. Therefore, after the child's hip is stable and has recovered from surgery, annual or biennial follow-ups are recommended until skeletal maturity, with specific follow-up frequency determined by the doctor.