Todd Milbrandt, MD, MS
Developmental dysplasia of the hip (DDH) encompasses a spectrum of disorders related to abnormalities of the developing hip and includes frankly dislocated hips, instability, and a shallow acetabulum. The current term defined by the American Academy of Orthopedic Surgeons (AAOS) and the Pediatric Orthopaedic Society of North America (POSNA) emphasizes that DDH is not limited to congenital disorders but is an evolving condition that can change with growth and development. DDH is a separate condition from neuromuscular hip dysplasia, which occurs most frequently in patients with spasticity. The cause of DDH is likely a combination of genetic and environmental factors. A strong association between the female gender and DDH has been shown, with 80 percent of those affected being female. In addition, other risk factors include first born, breech position, a family history of DDH, and oligohydramnios.,
Making the diagnosis in the newborn depends primarily on the hip exam, which should be performed routinely at each visit in infants. The baby should be examined while relaxed. The child should be undressed, and the diaper removed. The leg should be gently abducted and adducted. The sensation of the femoral head moving in (Ortolani sign) or out (Barlow sign) of the femoral head with a soft shifting or clunk should be the trigger for treatment or further imaging. Infants with an unstable hip should be seen by a pediatric orthopedic specialist within 1 to 2 weeks for prompt treatment. Limited hip abduction on one or both sides is another physical exam finding which should prompt ultrasound. In addition, ultrasound imaging should also be obtained at 4 to 6 weeks of age when any risk factors are in place, including 1st degree relative with hip dysplasia or history of breech intrauterine positioning. A low threshold for ultrasound is prudent to ensure early diagnosis and treatment, and it is helpful for providers to know that this is an ultrasound study that requires significant skill. Patients at 6 to 8 weeks of age with ultrasound abnormalities should also be referred for pediatric orthopedic evaluation. As the child ages, the hip instability signs are no longer present. Changes in gait such as a limp or shortened limb is most common. Pain is not seen in toddlers with DDH. After 6 months of age, an AP pelvis x-ray is the best study to evaluate for hip dysplasia and provides more reliable images than ultrasound. As the child ages, undiagnosed DDH will begin to cause pain as the forces across the joint become more abnormal.
For clinically unstable or dislocated hips, the optimal initiation of treatment with the Pavlik harness is as early as possible which is successful in over 85 percent of the patients. For the patient with mild US abnormalities, a stable hip, and a normal clinical examination, treatment timing is controversial. If bracing fails, then a closed reduction and spica cast application is performed around 6 months of age. Some dislocated hips require a more invasive surgery to open the hip joint and reduce the hip. This can be coupled with either a cut in the femur or acetabulum (Figure 1). Some complex hips require making a 3-D model, using techniques readily available at Mayo Clinic, to fully understand the anatomy to ensure a successful surgery.
Older children should also be treated if they develop symptoms. Children over age 10-12 can be treated with a periacetabular osteotomy (Figure 2), which is technically demanding but leads to powerful deformity correction. Sometimes this is coupled with a hip arthroscopy to ensure any issues the inside of the joint are also addressed.
This combination of procedures has shown to decrease the rate of degenerative changes and delay hip replacement. This surgery should only be performed by highly trained and experienced surgeons as complications can occur. Finally, if the DDH is not reconstructible, a hip replacement in late adulthood when performed by a high-volume academic center can return function to a painful hip.
In conclusion, DDH is a common condition with reliable nonoperative treatment options if detected early. Surgery is required for older patients with a dislocated or unstable hip. The role of surgery for acetabular dysplasia in childhood is evolving, but primarily driven by symptoms. The treatment options for DDH are expanding and we are learning how to better assess the patient’s anatomy thus leading to the right intervention at the right time.
Mayo Clinic pediatric orthopedic services are available at Mayo Clinic Square in Minneapolis and at Mayo Clinic in Rochester. To refer a patient, please contact the Referring Physician Office or call 800-538-1515.