|Case of the Week - Patient Summary 3967|
Peer Reviewed and Certified -
|Demographics: an infant y.o. girl|
|History & Chief complaint:|
| This patient is a female infant who was referred to radiology by pediatrics for ultrasound evaluation of subluxable hips.
Pt's medical history was significant for in-utero breech position, delivered via C-section and noted to have a left hip click. Pt was initially referred for a left hip ultrasound to rule out ddh. This US was followed-up approximately one month later with another bilateral hip US.
|Physical exam: Not Available|
|Summary of Findings:|
|27June: Bilateral abnormalities of hips by sonographic imaging. Right hip is 40% seated in the acetabulum. Alpha angle of 53-55 degrees on right hip. Left hip is 30-40% covered by acetabulum. Alpha angle of 52-55 degrees on left hip. The impression was bilateral ddh.
26July: Bilateral hip US done at follow-up in the standard coronal and axial planes. The right hip is normal, (improved compared to previous). Femoral head 50% covered by acetabulum (alpha angle 59 degrees). Dynamic imaging of right hip shows no evidence of ligamentous laxity. Left hip is approx 40% covered by acetabulum (alpha angle 51 degrees). Left hip does show ligamentous laxity on stress imaging. The impression was persistent ddh of left hip with 40% coverage and a 51 degree alpha angle.
| Developmental Dysplasia of the Hip (DDH) |
|US examination of the hip for ddh is done to assess anatomy/morphology of the acetabulum and the stability of the joint during dynamic/stress imaging. Anatomy of the joint is assessed with static coronal and axial images that assess the depth of the acetabular cup and its relation to the labrum and location of the femoral head (whether or not it is dislocated out of the cup). There are four types of hip maturity according to the Graf classsification (type one is a normal hip, two can vary from physiologic immaturity to mild dysplasia, three is a dislocation, and four is a high dislocation). Joint stability is assessed by imaging the femoral head and acetabulum during a Barlow maneuver (laxity in the joint can be assessed visually and felt clinically by attempting to dislocate the hip). (1)
On the US films, the femoral head and acetabular articulation is assessed with the alpha angle. Lines are often drawn directly on the film to delineate the articulation. The P line (Perkins line) is drawn vertically in a frontal plain through the iliac crest, tangential to the outer acetabular bony margin, and pointing down the shaft of the femur. The H line (Hilgenreiner line) is drawn perpendicular to the P line, in a horizontal orientation, through the triradiate cartilages (on diagram, where the ilium, ischium, and pubic bones intersect at the acetabulum, in a frontal plane). The A line is tangential to the bony acetabular roof, and forms the acetabular angle at its intersection with the H line. The alpha angle is the intersection between the A and P line. In a shallow acetabular joint, the alpha angle is decreased. Greater than or equal to 60 is a mature hip, 50-59 is physically immature or delayed ossification, 43-49 is subluxable, and less than 43 degrees is dislocated (with or without structural alteration) or severely dislocated. (2)