What Is Developmental Dysplasia of the Hip?
Hip joint consists of the ball part of femur called the femoral head and the socket of the pelvic bone called acetabulum. Developmental dysplasia of the hip (DDH) is a general term that refers to an abnormal relationship between the ball and socket of the hip joint in which there is an inadequate coverage of the ball by the socket or there is a dislocation of the ball from the socket (i.e. the ball is completely outside the socket). In some cases, the ball can slip in and out of the socket which is referred to as a dislocatable hip or an unstable hip. DDH can occur before birth, at birth, after birth, or during early childhood. In most patients, the diagnosis of DDH is made during the first year of life with neonatal and perinatal exams followed by a hip ultrasound. Sometimes, however, the signs of DDH are subtle and they go unnoticed until walking age or adolescence (adolescent hip dysplasia) when hip pain occurs. The diagnosis of a dislocated or dislocatable hip in infants is often challenging as it is not painful and does not limit the physical development of the child such as walking. It is important to identify DDH as early as possible and to treat this condition to prevent hip problems later in life.
Risk Factors for DDH
The cause of DDH is unknown, however, it is more common in babies who are born in breech presentation (feet first). There also seems to be a genetic component associated with DDH because children with a positive family history are more likely to have DDH than those without a history of hip disease in the family. It is also more common in females than in males and in first-born babies. Other risk factors include first born, low amniotic fluid level or tight uterus during pregnancy, and loose joint (ligamentous laxity). Swaddling of babies with legs straight also increases the risk.
How Is DDH Discovered?
The condition can be discovered by checking a baby's hips and, if suspected, performing an ultrasound of the hip. Your baby's doctor should look for:
A hip clunk
Limited hip movement
A difference in leg lengths
Increased skin folds on thighs
When both hips are dislocated, the leg lengths, skin folds, and hip movement are going to be the same which makes the diagnosis difficult without getting an ultrasound or a X-ray.
If the child walks, a waddling or swayed-back walking pattern
How Is DDH Treated?
The treatment for DDH depends on the child's age, the results of the hip exam and the results of the ultrasound or X-ray. Observation may be necessary, or more active treatment options may be recommended. These options may include the use of a Pavlik harness as well as surgery with or without traction if non-surgical treatments are unsuccessful.
Non-Surgical Treatment Methods
• Observation: The doctor may want to watch the child's hips closely if the hip exam shows a stable hip. Sometimes babies' hips are loose at birth but not dislocatable, and they may tighten on their own after a few weeks.
• Pavlik Harness: For babies less than 6 months of age, the doctor may recommend a soft, fabric brace called a Pavlik harness. The Pavlik harness keeps the hips in a “frog-leg” position, holding the ball of the thighbone in the hip socket. The harness is usually worn for 23 to 24 hours per day for a few weeks followed by a period of weaning off the brace for another few weeks. For 95% of babies treated with a Pavlik harness, no further treatment is ever needed.
Surgical Treatment Methods
• Closed Reduction with or without Bryant’s Traction: If the Pavlik harness is not keeping the baby's hips in place, the doctor may place the baby in light traction to loosen the muscles around the hip joint before surgery. At this time the effectiveness of home traction is unclear so some doctors use it but some don’t. This is an area of active research at TSRH. Bryant's traction uses soft wraps around the legs attached to weights. The baby will stay in traction for two to three weeks before surgery. Following this, the doctor attempts to place the hip into the socket while the child is under anesthesia. If successful, the baby is placed in a hip spica cast for up to three months. This is usually recommended for children between the ages of 6-24 months of age.
• Open Reduction: If the femoral head cannot be put back into the socket by a gentle manipulation, or it does not stay in the hip socket, or if the child is older than 24 months of age, an open reduction, in which the doctor has to do surgery to open the hip joint to remove the obstacles that are preventing the ball from staying in the socket. After surgery, the baby is placed in a spica cast.
• Pelvic Osteotomy: The term “osteotomy” refers to cutting through bone. A pelvic osteotomy may be required if the bony socket needs to be re-oriented to improve the coverage of the femoral head or to increase the chance of the femoral head staying in the socket. There are several types of pelvic osteotomies and the type that is required depends on the severity of DDH.