Congenital Hip Dysplasia (Developmental Dysplasia of the Hip)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Congenital Hip Dysplasia, also known as Developmental Dysplasia of the Hip (DDH), is a condition where the hip joint does not develop properly in infants and young children. The hip is a ball-and-socket joint, and in DDH, the ball (femoral head) is either loose in the socket (acetabulum) or dislocated. This can lead to joint instability, improper development, and potential long-term problems such as arthritis if untreated.

Aetiology

Congenital Hip Dysplasia is influenced by both genetic and environmental factors:

• Family history: DDH is more common in children with a family history of hip dysplasia or other joint problems.
• Position in the womb: Breech position (feet first) during pregnancy is a significant risk factor for hip dysplasia.
• Oligohydramnios: A low level of amniotic fluid during pregnancy can lead to restricted movement of the baby, increasing the risk of DDH.
• Firstborn child: Firstborn babies are more likely to have DDH due to the limited space in the womb.
• Postnatal positioning: Swaddling an infant with their legs straight and tightly bound can increase the risk of hip dysplasia by restricting the natural position of the hips.
• Female gender: DDH is more common in females, possibly due to the effect of maternal hormones that relax the ligaments during birth.

Pathophysiology

In a normal hip joint, the femoral head (ball) fits securely into the acetabulum (socket). In DDH, there is abnormal development of the hip joint, which may range from mild instability to complete dislocation. If the femoral head is not properly seated in the acetabulum, the socket may fail to develop correctly, leading to a shallow socket. Over time, this can result in a hip that becomes unstable and prone to dislocation. Untreated, DDH can lead to abnormal gait, leg length discrepancy, pain, and early osteoarthritis.

Risk Factors

• Female gender: DDH is more common in girls than boys.
• Breech presentation: Babies born in a breech position have a higher risk of DDH.
• Family history: A family history of hip dysplasia increases the likelihood of the condition.
• Firstborn child: Being the firstborn is a risk factor, possibly due to the limited space in the womb.
• Oligohydramnios: Reduced amniotic fluid during pregnancy increases the risk.
• Postnatal swaddling: Improper swaddling, with legs straightened and tightly bound, increases the risk.

Signs and Symptoms

The symptoms of DDH can vary depending on the severity of the condition:

• Limited hip abduction: Affected infants may have limited range of motion when spreading their legs, particularly when changing nappies.
• Asymmetry: Asymmetry in the skin folds of the thigh or buttocks may be present.
• Leg length discrepancy: One leg may appear shorter than the other.
• Gait abnormalities: Older children may develop a limp or exhibit a waddling gait if the condition goes untreated.
• Hip clicking: A soft clicking or popping sound may be heard when moving the baby's hips.

Investigations

• Physical examination: Routine newborn screening includes the Barlow and Ortolani manoeuvres, which check for hip instability and dislocation. The Barlow test involves pushing the hip out of the socket, while the Ortolani test involves repositioning the dislocated hip back into the socket.
• Ultrasound: If physical exam findings are suspicious or if the infant has risk factors such as breech birth, an ultrasound is typically performed to visualise the hip joint in infants under six months old.
• X-ray: X-rays are generally used in children older than six months when the bones are more developed and visible on radiographs.

Management

The treatment for DDH depends on the age of the child and the severity of the condition:

Non-Surgical Treatment:

• Pavlik harness: For babies under six months, a Pavlik harness is commonly used to hold the hip in a stable position, allowing the femoral head to stay properly aligned in the socket while the joint develops. The harness is typically worn full-time for 6-12 weeks.
• Bracing: After the Pavlik harness or for older infants, a rigid brace may be used to maintain proper hip positioning while the joint stabilises.

Surgical Treatment:

• Closed reduction: If the Pavlik harness or bracing is unsuccessful, a closed reduction may be performed. This involves manipulating the hip into place under anaesthesia, followed by the application of a spica cast to hold the hip in the correct position.
• Open reduction: In more severe cases or in older children, surgery may be required to reposition the hip joint and reconstruct the acetabulum.
• Osteotomy: An osteotomy may be needed to reshape the hip socket or femur to improve joint stability.

Follow-Up and Referral:

• Referral to a paediatric orthopaedic specialist is essential for early diagnosis and management to prevent long-term complications.
• Regular follow-up appointments with ultrasound or X-rays are necessary to monitor hip development and ensure the effectiveness of treatment.

References

1. NICE (2024). Developmental Dysplasia of the Hip: Diagnosis and Management in Children. Available at: NICE Guidance
2. Royal College of Paediatrics and Child Health (2023). Congenital Hip Dysplasia. Available at: RCPCH
3. British Orthopaedic Association (2023). Hip Dysplasia in Children: Treatment Guidelines. Available at: BOA