Congenital Hip Dysplasia Health Article

Definition

Congenital hip dysplasia is a condition of abnormal development of the hip, resulting in hip joint instability and potential dislocation of the thigh bone from the socket in the pelvis. This condition has been in the early 2000s been termed developmental hip dysplasia, because it often develops over the first few weeks, months, or years of life.

Description

Congenital hip dysplasia is a disorder in children that is either present at birth or shortly thereafter. During gestation, the infant's hip should be developing with the head of the thigh bone (femur) sitting perfectly centered in its shallow socket (acetabulum). The acetabulum should cover the head of the femur as if it were a ball sitting inside of a cup. In the event of congenital hip dysplasia, the development of the acetabulum in an infant allows the femoral head to ride upward out of the joint socket, especially when the infant begins to walk.

Demographics

In the United States, approximately 1.5 percent of all infants have congenital hip dysplasia. Though the worldwide incidence of congenital hip dysplasia varies, researchers estimate the global incidence to be approximately 1 percent.

Clinical studies show a familial tendency toward hip dysplasia with a greater chance of this hip abnormality in the first born compared to the second or third child. Infants with siblings who have been diagnosed with congenital hip dysplasia or who have parents with the defect are at an increased risk. Females are affected four to eight times more than males, and in children with congenital hip dysplasia, the left leg in more often affected. This disorder is found in many cultures around the world. However, statistics show that infants in colder climates have a higher incidence. It is speculated that this increase may be due to the practice of swaddling which can place the infant's legs in an extreme straightened or adducted position, forcing the hips closer together. The incidence of congenital hip dysplasia is also higher in infants born by cesarean and in breech position births.

Causes and symptoms

Hormonal changes within the mother during pregnancy result in increased ligament looseness or laxity and are thought to possibly cross over the placenta and cause the baby to have lax ligaments while still in the womb. Other symptoms of complete dislocation include a shortening of the leg and limited ability to abduct the leg, or move it outward.

Diagnosis

Because the abnormalities of this hip problem often vary, a thorough physical examination is necessary for an accurate diagnosis of congenital hip dysplasia. The hip disorder can be diagnosed by moving the hip to determine if the head of the femur is moving in and out of the hip joint. One specific method, called the Ortolani test, begins with each of the examiner's hands around the infant's knees, with the second and third fingers pointing down the child's thigh. With the legs abducted (moved apart), the examiner may be able to hear a distinct clicking sound, called a hip click, with motion. If symptoms are present with a noted increase in abduction, the test is considered positive for hip joint instability. It is important to note this test is only valid a few weeks after birth.

The Barlow method is another test performed with the infant's hip brought together with knees in full bent position. The examiner's middle finger is placed over the outside of the hipbone while the thumb is placed on the inner side of the knee. The hip is abducted to where it can be felt if the hip is sliding out and then back in the joint. In older babies, if there is a lack of range of motion in one hip or even both hips, it is possible that the movement is blocked because the hip has dislocated and the muscles have contracted in that position. Also in older infants, hip dislocation may be present if one leg looks shorter than the other.

X-ray films can be helpful in detecting abnormal findings of the hip joint. X rays may also be helpful in finding the proper positioning of the hip joint for treatment. Ultrasound has been noted as a safe and effective tool for the diagnosis of congenital hip dysplasia. Ultrasound has advantages over x rays, as several positions are noted during the ultrasound procedure. This is in contrast to only one position observed during the x ray.