Developmental dysplasia of the hip, also known as hip dysplasia, is a condition of unknown origin that involves abnormal growth and development of the hip joint. This includes any of the structures that form the hip joint such as the femur, and acetabulum. This abnormal growth and development can lead to instability of the hip joint and the potential for complete or partial loss of contact between the head of the femur and acetabulum. It can also lead to uneven loading of the hip joint in less severe cases.
If left untreated, hip dysplasia can result in pain, difficulty walking, decreased hip strength, and development of osteoarthritis at a relatively young age. Treatment is dependent on the age of the affected person. It includes stabilization in a special harness (Pavlik harness) or cast (Spica cast) for babies and infants, and surgical intervention including open reduction, capsulorrhaphy, and a femoral or acetabular osteotomy for older individuals.
Hip dysplasia is a condition resulting from abnormal development of one or more components of the hip joint such that weight is not distributed evenly over the joint surfaces. This typically leads to subluxation or dislocation of the hip joint, and predisposes the individual to the development of early osteoarthritis. Hip dysplasia is a disease of neonates and young children but can on occasion be diagnosed in older children or adults. Patient’s with hip dysplasia are more commonly females, first born children, have a family history of the disease and were breech presentation during labor. Breech refers to the baby being delivered legs-first rather than head-first. Most babies in the breech position are now delivered via Cesarian section rather than vaginally in order to avoid pathologies such as hip dysplasia. The left hip is more commonly involved than the right.
Unfortunately, not all forms of hip dysplasia can be diagnosed early on. Infants or children with hip dysplasia who were not diagnosed as newborns may initially be brought in to see a health care provider because of a limp without acute trauma. Children may also complain of hip pain, usually as a result of a complication of hip dysplasia such as subluxation or dislocation.
Newborns with hip dysplasia may have a small risk of having other associated conditions, such as Cerebral Palsy or Spina Bifida and further tests may be ordered to determine the presence of these conditions.
There is now a growing recognition that subtle hip dysplasia that creates essentially no symptoms as a baby or child will lead to uneven wearing of the hip joint. This will develop into premature hip arthritis when patients are in their 60’s 50’s or even 40’s.
Hip dysplasia is ideally picked up on routine physical exam screening of newborns. The screening physician should assess the newborn to ensure that each hip is appropriately positioned in the hip socket, and that the hip joint is not loose. Other physical exam findings that may be present include legs of different lengths, uneven skin folds on the thigh, or reduced mobility and flexibility on one side.
An important part of the newborn exam includes two special tests called the Barlow and Ortolani maneuvers. These tests are designed to check if the baby’s hips are either able to be dislocated or subluxed or are already dislocated and able to be put back in place (reduced). The physician performing the exam is looking to feel or hear a “clunk,” which is a sign of the femoral head either dislocating out of the hip socket or the femoral head going back into the hip socket. A “clunk” implies a positive test finding and further workup will be needed to assess the baby’s hip, including imaging studies.
Unfortunately, not all hip dysplasia is present at birth or in the immediate newborn period and therefore will not be picked up with Barlow and Ortolani maneuvers. Additionally, once the infant reaches 3 months of age, the Barlow and Ortolani maneuvers are no longer reliable tests for hip dysplasia.
In older children, different physical examination signs may be present. If the patient has the disease on one side only, Galleazi’s sign may be visible. This involves bringing the knees towards the chest making a 90-degree angle between the thigh and lower leg. Other findings include decreased mobility of the hip, especially in abduction, and leg length discrepancy. Of note, the length of the leg is not actually shorter but appears that way because the dislocated hip is sitting in a different place from the normal one.
The choice of imaging study to perform in order to confirm the diagnosis for hip dysplasia is dependent on the age of the infant or child. The femoral head is made up of cartilage in newborns, which will eventually turn into bone. X-rays do not assess cartilage very well and are typically more useful for assessment of bone. The cartilage begins to turn into bone (ossify) around 3-6 months of age. Therefore, x-rays begin to be a valuable imaging test around 4-5 months of age.
In younger infants less than 4 months old, ultrasound is the imaging study of choice, as it allows good visualization of the hip joint including the ability to see the cartilage. Ultrasound also eliminates the risks associated with radiation exposure form x-ray. In select cases where more information regarding the extent or severity of the disease is needed, a CT scan or an MRI may be performed as well.
Treatment for hip dysplasia is mainly determined by the age of the child. Non-operative treatment is pursued for children less than 6 months old and can be used in children up to 18 months old. The goal of non-operative treatment is to hold the head of the femur in place while the acetabulum develops around it and the ligaments and soft tissues tighten to hold the hip joint in place. If hip dysplasia is not treated, the child will be at risk of developing early osteoarthritis, persistent hip instability, and avascular necrosis.
In infants less than 6 months old, a special device known as a Pavlik harness is used for 6-12 weeks to hold the femoral head in the acetabulum. If the Pavlik harness does not work or if the child is between 6-18 months old when diagnosed, the treatment of choice is closed reduction and a Spica cast. A Spica cast is a special cast that covers the child’s trunk and both legs, preventing any movement. The Spica cast is applied after ensuring the femoral head has been reduced into the acetabulum. Closed reduction (as opposed to open, which requires surgery) is usually done with the child asleep under a general anesthetic. The Spica cast, like the Pavlik harness, is typically worn for 6-12 weeks. If the cast is not successful or the child is older than 18 months, surgical treatment options have been shown to be more effective.
If non-operative treatment is not successful or the child is older than 18 months when diagnosed, surgical intervention is the treatment of choice. Surgery involves open reduction, or surgery to put the hip back into place. A capsulorrhaphy may also be performed, which involves opening up the hip joint capsule and suturing the joint capsule in such a way as to prevent further dislocation and subluxation.
Another type of surgery that can be performed for the treatment of hip dysplasia is an osteotomy. An osteotomy involves cutting and repositioning one of more bones around the hip joint. The bone is removed and/or repositioned on either the acetabular or femoral side, which can help achieve better hip alignment and range of motion. Post-osteotomy use of a Spica cast in young children is an important component of treatment as it holds the hip in position during the healing process. Various osteotomies around the hip joint may be used to attempt to reposition and realign the hip joint in patients with symptomatic hip dysplasia who are in their teens or 20’s.