A shallow hip socket in infants and young children is called developmental dysplasia of the hip or DDH. DDH is a risk factor for dislocation. It is treatable with a special harness during the first year of life. The device is called a Pavlik harness named after Dr. A. Pavlik.

In this study doctors report how ultrasound can be used to predict hips that won’t respond well to the harness. Knowing this ahead of time helps doctors make a better treatment plan for the child. Until now researchers have tried to link other factors such as age, gender, and breech birth with increased risk for failure. None of these were helpful.

Serial ultrasound pictures are useful because they allow several measures. The doctor can see how much of the head of the femur is covered by the hip socket. This is called the dynamic coverage index or DCI. It also shows important hip angles and the type of cartilage that forms the hip socket covering.

Full success using the Pavlik harness is possible unless the DCI is less than 22 percent, the angle is less than 43 degrees, and the joint cartilage shows up as fibrocartilage. When any of these three factors are present, the harness is not likely to work. A more rigid splint may be needed.

The authors advise doctors to do long-term follow-up studies with all children at risk for problems later on. The single most predictive factor of problems is the presence of fibrocartilage instead of hyaline cartilage forming the roof of the hip socket.