Review Question - QID 219113

The patient in the question stem is being evaluated for possible developmental dysplasia of the hip (DDH). The letter “B” in the ultrasound depicts the cartilaginous labrum.

Several physical exam findings and tests are employed as adjuncts to radiographic examination to diagnose DDH. While asymmetric inguinal skin folds may be suggestive of hip dysplasia, other physical exam findings are often utilized to increase the sensitivity in detecting true hip pathology. The sensitivity of the Ortolani and Barlow maneuvers is limited beyond 8-12 weeks in age, given the lessened effects of maternal relaxin and ongoing development of the hip which is characterized by decreased capsular laxity and increased muscle tone. Additionally, both maneuvers may be negative if the hip is already dislocated, especially in children with stiff, chronically dislocated hips refractory to closed reduction maneuvers. Therefore, the older infant may require additional physical exam maneuvers (limitations in hip abduction, Klisic test, Galeazzi test) and hip ultrasound evaluation to detect true developmental hip dysplasia.

Harcke and Kumar published a 1991 review of the role of ultrasound in the diagnosis and management of DDH. The ultrasound examination is a sensitive indicator of malposition, instability, and lack of acetabular development. It is more accurate than a radiograph in defining any abnormalities of the hip because it shows the cartilaginous components of the acetabulum and the proximal part of the femur, which are not visualized on routine radiographs. Dynamic techniques accurately describe stability and can show subluxation with or without dislocatability. In dislocated hips, examination by ultrasound assesses reducibility. In many respects, it yields information that formerly had to be obtained by contrast arthrography. Ultrasonography accomplishes all of this without exposing the child to ionizing radiation.

Litrenta et al. published a 2020 review on the utility of ultrasound in evaluating pediatric patients. For DDH, the authors note that physical examinations can be difficult, especially in very young or uncooperative patients. Additionally, stable dysplasia is clinically silent and can be difficult to detect on physical examination alone. Additionally, for frank hip dislocation in children younger than the age of 4 months, the sensitivity of physical examination alone is only 37%, which improves to 66% with radiographs and to 89% with ultrasonography. Instability decreases the sensitivity even further, and because instability is dynamic, physical examination is a better predictor than radiographs, but sensitivity remains low. Ultrasonography captures dynamic images and therefore maintains its sensitivity for both instability and stable dysplasia.

Figure A is a coronal flexion view of a hip ultrasound. It is often best interpreted as an anteroposterior view rotated 90º to the left. The abductor musculature (A) overlies the cartilaginous labrum (B). The femoral head is the large circular structure (D) surrounded by the acetabulum. The ilium (C) forms the roof. The triradiate cartilage (E) and ischium (not labeled) form the medial wall.

Incorrect answers:

Answers 1, 3, 4, and 5: The letter “B” identifies the acetabular labrum.