Which of the following is the most sensitive clinical sign for detection of developmental dysplasia of the hip (DDH) in a baby aged 6 months?
**Core Concept**
Developmental dysplasia of the hip (DDH) is a condition where the hip joint forms abnormally, leading to instability or dislocation. Early detection is crucial to prevent long-term complications. The clinical examination of infants is critical in identifying DDH, and various signs have been described.
**Why the Correct Answer is Right**
The most sensitive clinical sign for DDH in a 6-month-old baby is the Ortolani sign. This sign involves gently abducting and externally rotating the hip while palpating the greater trochanter. A dislocatable or reducible hip will "clunk" back into place, indicating a positive Ortolani sign. This sign is particularly useful in the 4-9 month age group, as it is more likely to be positive in infants with DDH. The Ortolani sign is thought to be related to the laxity of the hip joint capsule and the surrounding muscles in young infants.
**Why Each Wrong Option is Incorrect**
* **Option A:** The Barlow sign, which involves attempting to dislocate the hip, is less sensitive than the Ortolani sign in detecting DDH in infants aged 6 months.
* **Option B:** The Trendelenburg sign is a clinical sign of hip abductor weakness, which may be seen in older children or adults with hip disorders, but is not specific for DDH in infants.
* **Option D:** The Galeazzi sign, which involves flexing the hip and knee to assess for asymmetry, is not as sensitive as the Ortolani sign for detecting DDH in infants.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that the Ortolani sign is most sensitive in the 4-9 month age group, and its absence does not rule out DDH in infants. A thorough clinical examination, including the Ortolani and Barlow signs, should be performed in all infants before the age of 6 months to detect DDH early.
**Correct Answer:** C.