Developmental Dysplasia of the Hip (DDH) is a spectrum of disorders where the "ball and socket" joint of the hip does not form correctly. This can range from a mild looseness of the joint to a complete dislocation where the ball is entirely out of the socket.
1. Key Facts & Risk Factors
- The "F" Factors: DDH is most commonly seen in children who are Female, First-born, and/or were in a Frank breech position (buttocks-down) during the third trimester.
- Incidence: About 1 in 100 infants are born with some form of hip instability, and 1 in 1,000 has a complete dislocation.
- Left Side Dominance: For reasons likely related to how a baby sits in the womb, the left hip is affected in approximately 60% of cases.
2. Signs and Symptoms
In infants, DDH is painless, which makes it difficult for parents to spot. Doctors look for:
- Asymmetric Skin Folds: Uneven "rolls" of skin on the thighs or buttocks.
- Limited Abduction: Difficulty spreading the baby’s legs apart (stiffness in the hip).
- Leg Length Discrepancy: One leg appearing shorter than the other.
- The "Clunk": During a physical exam, a doctor may feel a "clunk" (Ortolani or Barlow maneuvers) as the hip slips in or out of the socket.
- Walking Patterns: If missed until walking age, a child may have a noticeable limp or a "waddling" gait.
3. Diagnosis
- Physical Exam: The most important tool. Every newborn is screened at birth and during well-child visits.
- Ultrasound (Under 6 Months): Preferred for young infants because much of the hip joint is still made of cartilage, which does not show up well on X-rays.
- X-ray (Over 6 Months): Once the bones begin to harden (ossify), X-rays become the most reliable way to measure the depth and shape of the socket.
4. Treatment Pathways
The goal of treatment is to keep the "ball" centered in the "socket" so the joint can grow properly.
5. Important Note on Swaddling
POSNA and OrthoKids strongly emphasize "Hip-Safe Swaddling." Tightly wrapping a baby’s legs straight down and pressed together can actually cause or worsen hip dysplasia.
- Rule of Thumb: Always ensure the baby’s legs can bend "up and out" like a frog.
6. Long-Term Outlook
When diagnosed early, the vast majority of children develop normal hips and lead active lives. If left untreated, DDH is a leading cause of early-onset hip arthritis and the need for hip replacements in young adulthood.