The American Academy of Pediatrics (AAP) has developed a clinical practice guideline on the early detection of developmental dysplasia of the hip (DDH), which includes frank dislocation, partial dislocation, instability and inadequate formation of the acetabulum. Written by the AAP Committee on Quality Improvement, Subcommittee on Developmental Dysplasia of the Hip, the guideline points out that the term “developmental” is preferred over the term “congenital.” Developmental more accurately reflects the disorder because these abnormalities may not be present at birth. According to the guideline, newborn screening surveys suggest that dislocation of the hip may occur at a rate of 1.0 to 1.5 cases per 1,000 newborns.
The guideline, titled “Clinical Practice Guideline: Early Detection of Developmental Dysplasia of the Hip,” appears in the April 2000 issue of Pediatrics. It includes a discussion of the features of the disorder, including risk factors and methods of detection, and of the way in which the recommendations in the guideline were developed.
The AAP guideline states that the hip is at risk of dislocation in the 12th gestational week, in the 18th gestational week, in the final four weeks of gestation, when mechanical forces play a role, and in the postnatal period. Oligohydramnios and breech presentation are associated with an increased risk of DDH. Studies suggest that as many as 23 percent of infants with breech presentation are affected. Postnatally, positioning of the infant may play a role.
The incidence of DDH is higher in girls, perhaps because females are more susceptible than males to the maternal hormone relaxin, which may contribute to ligamentous laxity. The left hip is affected three times more often than the right hip, which may be related to the left occiput anterior position of most nonbreech infants.
The AAP guideline states that there are no pathognomonic signs for a dislocated hip. Asymmetry of the thigh or gluteal folds, limb length discrepancy and restricted motion (especially abduction) can be signs of a dislocated hip. The Ortolani and Barlow tests are useful for assessing hip stability in the newborn. A palpable “clunk” during either maneuver is considered a strongly positive sign for dislocation of the hip. A dislocatable hip is described as having a distinctive clunk, whereas a subluxable hip is characterized by a feeling of looseness, a sliding movement without the true clunks felt on the Ortolani and Barlow maneuvers. By eight to 12 weeks of age, the Ortolani and Barlow tests are no longer useful, regardless of the status of the femoral head. At this age, capsule laxity decreases and muscle tightness increases. According to the AAP guideline, the most reliable sign in the three-month-old infant is limitation of abduction. Other features of DDH at this age include asymmetry of the thigh folds, relative shortness of the femur with the hips and knees flexed (called the Allis or Galeazzi sign) and a discrepancy of leg lengths.
The AAP guideline notes that real-time ultrasonography is the most accurate method for imaging the hip in the first few months after birth. Ultrasonography provides visualization of the cartilage, hip stability and features of the acetabulum. Ultrasonography is identified as the technique of choice for clarifying a physical finding suggestive of DDH, for assessing a high-risk infant and for monitoring DDH. Radiographs are of limited value during the first few months of life but are more reliable in infants four to six months of age, when the ossification center develops in the femoral head. According to the guideline, ultrasonography and radiography are equally effective imaging studies for detecting DDH in infants four to six months of age.
The accompanying algorithm gives an overview of the recommendations for DDH screening in infants. The following summarizes the AAP recommendations:
All newborns should be screened by physical examination. Ultrasonography of all newborns is not recommended.
Referral to an orthopedist is recommended if a positive Ortolani or Barlow test is found on the newborn examination. Ultrasonography is not recommended in infants with positive findings, nor is radiographic examination of the pelvis and hips.
Developmental Dysplasia of the Hip
Algorithm for screening for developmental dysplasia of the hip.
Reprinted with permission from American Academy of Pediatrics Committee on Quality Improvement. Clinical practice guideline: early detection of developmental dysplasia of the hip. Pediatrics 2000;105:896–905.
The use of triple diapers in infants with physical signs suggestive of DDH during the newborn period is not recommended. The guideline notes that triple-diaper use is a common practice despite the lack of data on effectiveness.
If the physical examination at birth reveals “equivocally” positive findings (i.e., a soft click, mild asymmetry, but no Ortolani or Barlow sign), a follow-up hip examination should be performed when the infant is two weeks of age.
If the Ortolani or Barlow test is positive at the two-week examination, the infant should be referred to an orthopedist. Referral is deemed urgent but not an emergency.
If the Ortolani or Barlow test is negative at the two-week examination but other physical findings raise the suspicion of DDH, consideration should be given to referring the infant to an orthopedist or obtaining ultrasonography at age three to four weeks.
If the physical examination is negative at two weeks of age, follow-up is recommended at the scheduled well-baby periodic examinations.
If the results of the newborn examination are negative, consideration may be given to risk factors for DDH. These risk factors include the following: female infants, a family history of DDH and breech presentation.
The newborn risk of DDH is 19 per 1,000 in girls. If the newborn examination is negative or equivocally positive, the hips should be reexamined when the infant is two weeks of age.
Infants with a Positive Family History of DDH
When the family history is positive, the newborn risk is 9.4 per 1,000 for boys and 44.0 per 1,000 for girls. When the newborn examination is negative or equivocally positive in boys with a family history, reevaluation of the hips at two weeks of age is recommended. In girls with a family history of DDH, ultrasonographic examination at six weeks of age or radiographic examination of the pelvis and hips at four months of age is recommended.
The newborn risk of breech presentation is 120 per 1,000 for girls and 26 per 1,000 for boys. When the newborn examination is negative or equivocally positive in boys with breech presentation, reevaluation of the hips should be conducted at regular intervals. In girls, because of their absolute risk of 120 per 1,000, ultrasonographic examination at six weeks of age or radiographic evaluation of the pelvis and hips at four months of age is recommended. The guideline also notes that there is a high incidence of hip abnormalities in children born breech. For this reason, ultrasonographic examination remains an option in all children born breech.
The hips must be examined at every well-baby visit (two to four days for newborns discharged in less than 48 hours after delivery and by one month, two months, four months, six months, nine months and 12 months of age).