The hip socket is a soft, rubbery cartilage at birth and some children have greater laxity or looseness naturally. This laxity means the hip moves in and out of the socket fairly easily — just like in the child who has the anatomic changes associated hip dysplasia–but without any actual changes in the bone structure.
Hip dysplasia is first considered when the pediatrician performs a newborn exam. One of the special tests used most often to look for signs of an unstable hip is the Ortolani maneuver. This test is designed to detect if the hip is sliding in and out of the acetabulum. To perform the test, the doctor places the infant on a table in a supine position (on his or her back). The doctor then abducts the hips by moving the bent hips and knees apart. If the hip feels like it can be pushed out the back of the socket, this is considered abnormal. This is a sign of instability in the hip. As the hip is abducted further, the doctor might feel the ball portion (the femoral head) slide forward as it slips back into the socket. This is a positive Ortolani Maneuver and is also a sign of hip instability.
If the test is positive, the child will be watched closely or immediately placed in a special brace called a Pavlik harness. Treatment isn’t always required as some children seem to grow out of it. The Ortolani test doesn’t differentiate between children with true hip dysplasia and those who just have loose hips. Recently, the use of ultrasonography as an imaging tool has come into play with hip dysplasia. Ultrasound testing might also help doctors recognize who has a true case of hip dysplasia and is a good candidate for the harness treatment.
Two angles in particular can be measured with ultrasound images: femoral head displacement relative to the labrum (FHD-L) and total femoral head displacement (FHD-T). Children with an FHD-L of zero degrees (normal relationship of femoral head to the labrum) are more likely to have successful results with the Pavlik harness. These children probably just had loose cartilage and the head of the femur could slip into the socket easily. They may not have even needed the harness. By the time the harness was removed, the cartilage had tightened up and the hip remained in the socket without the harness.
In one recent study using ultrasound measurements, children with FHD-T angles less than -30 to -40 all failed treatment with the Pavlik harness. This angle indicates that the femoral head was displaced out and up away from the socket too far to be reduced by positioning with the harness. Additional treatment was needed — either with a wider hip angle using an abduction brace or with corrective surgery.
Without a clear way to really recognize children with very loose joints early on, a little prevention is advised. Double or triple diapering may be all that’s needed to ensure good hip socket position. The Pavlik harness does the same thing but holds the hips more effectively than the diapering. Ultrasound studies are not used routinely to confirm the diagnosis. If the Ortolani test is still positive after three or four weeks using the harness, then additional imaging studies might be helpful to guide further treatment. Hopefully in a month’s time, you will be able to move past this problem with no further intervention required.