Why does children's hip dislocation occur

Patient's question:

Developmental dysplasia of the hip

Doctor's answer:

At 3 months, the fetus is in the period of hip joint formation. If the pregnant mother suffers from a cold, fever, or other illnesses, it may cause a temporary halt in fetal growth, leading to abnormal joint development and resulting in dislocation. The ratio of affected males to females is approximately 1:5, so parents must pay attention to checking for this condition when the baby is born.
There is a simple self-examination method: Lay the baby down and gently spread their hips to both sides (with knees at a 90-degree angle and thighs perpendicular to the body). If the baby's legs are stiff and cannot be moved, it is likely this condition. Additionally, if the baby's thigh stripes are asymmetrical or the legs appear of unequal length, it is often a sign of this condition. However, mild or partial dislocations can be difficult to diagnose through manual examination, especially since infants have thick leg fat and leg length differences may be hard to determine. Therefore, ultrasound examinations are recommended for infants under 6 months to confirm the diagnosis.
It is important to note that X-rays are not useful for infants under 6 months because their bones are not yet calcified, and the centers of ossification have not yet appeared, resulting in blank X-ray images. Thus, there is no need to expose the baby to unnecessary X-ray harm. For infants over 10 months, X-rays can be used for diagnosis.
Early diagnosis and treatment of congenital hip dislocation are crucial. If a diagnosis is confirmed in infants aged 3–6 months, specialized harnesses can be used for immobilization, with a cure rate of over 95% after 3 months. This treatment does not damage the joint and has few complications. For toddlers around 1 year old who are starting to walk, the dislocated joint must first be reduced, followed by 3 months of frog-leg casting, and then the use of a frog-leg brace for 9–12 months to restore normal function. Children over 2 years old may require surgery followed by casting. Children aged 4–7 must undergo surgery to fully recover. The younger the child, the better the surgical outcome; the older the child, the greater the surgical trauma and the poorer the results.
If hip dislocation is left untreated, it can lead to leg disability, limping, and chronic leg pain that becomes unbearable as the person grows older.