Ultrasound (U/S) is valuable modality for evaluating the hip in infants because it enables direct imaging of the cartilaginous portion of the hip that cannot be seen on plain radiographs. Furthermore, U/S examination enables dynamic study of the hip with stress maneuvering. U/S is the preferred imaging modality which used to study the hip disorders like developmental dysplasia of hip ( DDH ), because it is sensitive indicator of malposition, instability and lack of acetabular development. U/S accomplishes all of these without exposing the infant to ionizing radiation, not expensive, non-invasive and available.
The aim of our study is to determine the effectiveness and sensitivity of ultrasound examination of neonates to confirm the early clinical diagnosis of developmental dysplasia of hip ( DDH ) especially in the high risk groups of neonates and young infants.
We conducted a retrospective review of ultrasonographic imaging in 60 neonates and young infants ( 36 females and 24 males ; age range, 1-9 months, median age , 4 months). U/S examination of the hip joint were evaluated for, percent bony coverage (PBC), which indicates the percentage of the femoral head that covered by the bony acetabulum, normally, 50% or over of the femoral head should be covered by bony acetabulum. And evaluated for Graf angles, alpha angle which defines the bony acetabulum and normally it is more than 60 degree and beta angle which indicates the cartilaginous development and it is normally less than 55 degree. Also evaluate the femoral head flattening which usually associated with delayed ossification , shortening and anteverting of the femoral neck .
DDH is more common in the female patients ( F:M = 3:1 ). Instability and dislocation is usually unilateral, this is seen in 30 patients (50%), (unilateral :bilateral = 3:1). Left hip is more commonly affected, this is seen in 24 patients(40%),( L:R = 4:1 ). Children born by caesarian section are more likely to have associated instability or dislocation of the hip, 10 patients(25%). First born baby are more affected, 4 patients(10%) and usually these children are more likely to have been breech presentation during their gestation, 14 patients (35%). Family history of DDH is seen in 6 patients(15%).
The U/S is the preferred modality for evaluating the hip in infants who are younger than 6 months. U/S of infant's hip can be used in the diagnosis of DDH and also in monitoring of treatment or follow-up the improvement in the acetabular maturity and morphology, as well as the location of femoral head can be documented to assist in the guidance of therapy plan.