AMERICAN ACADEMY OF PEDIATRICS Committee on Quality Improvement, Subcommittee on Developmental Dysplasia of the Hip Clinical Practice Guideline: Early Detection of Developmental Dysplasia of the Hip

Developmental dysplasia of the hip is the preferred term to describe the condition in which the femoral head has an abnormal relationship to the acetab­ ulum. Developmental dysplasia of the hip includes frank dislocation (luxation), partial dislocation (subluxation), instability wherein the femoral head comes in and out of the socket, and an array of radiographic abnormalities that reflect inadequate formation of the acetabulum. Be­ cause many of these findings may not be present at birth, the term developmental more accurately reflects the bio­ logic features than does the term congenital. The disorder is uncommon. The earlier a dislocated hip is detected, the simpler and more effective is the treatment. Despite new­ born screening programs, dislocated hips continue to be diagnosed later in infancy and childhood,1–11 in some instances delaying appropriate therapy and leading to a substantial number of malpractice claims. The objective of this guideline is to reduce the number of dislocated hips detected later in infancy and childhood. The target audience is the primary care provider. The target patient is the healthy newborn up to 18 months of age, excluding those with neuromuscular disorders, myelodysplasia, or arthrogryposis. ABBREVIATIONS. DDH, developmental dysplasia of the hip; AVN, avascular necrosis of the hip. BIOLOGIC FEATURES AND NATURAL HISTORY Understanding the developmental nature of developmental dysplasia of the hip (DDH) and the subsequent spectrum of hip abnor­ malities requires a knowledge of the growth and development of the hip joint.12 Embryologically, the femoral head and acetabulum develop from the same block of primitive mesenchymal cells. A cleft develops to separate them at 7 to 8 weeks’ gestation. By 11 weeks’ gestation, development of the hip joint is complete. At birth, the femoral head and the ace­ tabulum are primarily cartilaginous. The acetabulum continues to develop postnatally. The growth of the fibrocartilaginous rim (the labrum) that surrounds The recommendations in this statement do not indicate an exclusive course of treatment or serve as a standard of medical care. Variations, taking into account individual circumstances, may be appropriate. The Practice Guideline, “Early Detection of Developmental Dysplasia of the Hip,” was reviewed by appropriate committees and sections of the Amer­ ican Academy of Pediatrics (AAP) including the Chapter Review Group, a focus group of office-based pediatricians representing each AAP District: Gene R. Adams, MD; Robert M. Corwin, MD; Diane Fuquay, MD; Barbara M. Harley, MD; Thomas J. Herr, MD, Chair; Kenneth E. Matthews, MD; Robert D. Mines, MD; Lawrence C. Pakula, MD; Howard B. Weinblatt, MD; and Delosa A. Young, MD. The Practice Guideline was also reviewed by relevant outside medical organizations as part of the peer review process. PEDIATRICS (ISSN 0031 4005). Copyright © 2000 by the American Acad­ emy of Pediatrics. the bony acetabulum deepens the socket. Develop­ ment of the femoral head and acetabulum are inti­ mately related, and normal adult hip joints depend on further growth of these structures. Hip dysplasia may occur in utero, perinatally, or during infancy and childhood. The acronym DDH includes hips that are unstable, subluxated, dislocated (luxated), and/or have mal­ formed acetabula. A hip is unstable when the tight fit between the femoral head and the acetabulum is lost and the femoral head is able to move within (sub­ luxated) or outside (dislocated) the confines of the acetabulum. A dislocation is a complete loss of contact of the femoral head with the acetabulum. Disloca­ tions are divided into 2 types: teratologic and typi­ cal.12 Teratologic dislocations occur early in utero and often are associated with neuromuscular disorders, such as arthrogryposis and myelodysplasia, or with various dysmorphic syndromes. The typical disloca­ tion occurs in an otherwise healthy infant and may occur prenatally or postnatally. During the immediate newborn period, laxity of the hip capsule predominates, and, if clinically sig­ nificant enough, the femoral head may spontane­ ously dislocate and relocate. If the hip spontaneously relocates and stabilizes within a few days, subse­ quent hip development usually is normal. If sublux­ ation or dislocation persists, then structural anatomic changes may develop. A deep concentric position of the femoral head in the acetabulum is necessary for normal development of the hip. When not deeply reduced (subluxated), the labrum may become everted and flattened. Because the femoral head is not reduced into the depth of the socket, the acetab­ ulum does not grow and remodel and, therefore, becomes shallow. If the femoral head moves further out of the socket (dislocation), typically superiorly and laterally, the inferior capsule is pulled upward over the now empty socket. Muscles surrounding the hip, especially the adductors, become contracted, limiting abduction of the hip. The hip capsule con­ stricts; once this capsular constriction narrows to less than the diameter of the femoral head, the hip can no longer be reduced by manual manipulative maneu­ vers, and operative reduction usually is necessary. The hip is at risk for dislocation during 4 periods: 1) the 12th gestational week, 2) the 18th gestational week, 3) the final 4 weeks of gestation, and 4) the postnatal period. During the 12th gestational week, the hip is at risk as the fetal lower limb rotates medially. A dislocation at this time is termed terato­ logic. All elements of the hip joint develop abnor­ 896 PEDIATRICS Vol. 105 No. 4 April 2000 mally. The hip muscles develop around the 18th gestational week. Neuromuscular problems at this time, such as myelodysplasia and arthrogryposis, also lead to teratologic dislocations. During the final 4 weeks of pregnancy, mechanical forces have a role. Conditions such as oligohydramnios or breech posi­ tion predispose to DDH.13 Breech position occurs in �3% of births, and DDH occurs more frequently in breech presentations, reportedly in as many as 23%. The frank breech position of hip flexion and knee extension places a newborn or infant at the highest risk. Postnatally, infant positioning such as swad­ dling, combined with ligamentous laxity, also has a role. The true incidence of dislocation of the hip can only be presumed. There is no “gold standard” for diagnosis during the newborn period. Physical ex­ amination, plane radiography, and ultrasonography all are fraught with false-positive and false-negative results. Arthrography (insertion of contrast medium into the hip joint) and magnetic resonance imaging, although accurate for determining the precise hip anatomy, are inappropriate methods for screening the newborn and infant. The reported incidence of DDH is influenced by genetic and racial factors, diagnostic criteria, the ex­ perience and training of the examiner, and the age of the child at the time of the examination. Wynne­ Davies14 reported an increased risk to subsequent children in the presence of a diagnosed dislocation (6% risk with healthy parents and an affected child, 12% risk with an affected parent, and 36% risk with an affected parent and 1 affected child). DDH is not always detectable at birth, but some newborn screen­ ing surveys suggest an incidence as high as 1 in 100 newborns with evidence of instability, and 1 to 1.5 cases of dislocation per 1000 newborns. The inci­ dence of DDH is higher in girls. Girls are especially susceptible to the maternal hormone relaxin, which may contribute to ligamentous laxity with the result­ ant instability of the hip. The left hip is involved 3 times as commonly as the right hip, perhaps related to the left occiput anterior positioning of most nonbreech newborns. In this position, the left hip resides posteriorly against the mother’s spine, potentially limiting abduction. PHYSICAL EXAMINATION DDH is an evolving process, and its physical find­ ings on clinical examination change.12,15,16 The new­ born must be relaxed and preferably examined on a firm surface. Considerable patience and skill are re­ quired. The physical examination changes as the child grows older. No signs are pathognomonic for a dislocated hip. The examiner must look for asymme­ try. Indeed, bilateral dislocations are more difficult to diagnose than unilateral dislocations because sym­ metry is retained. Asymmetrical thigh or gluteal folds, better observed when the child is prone, ap­ parent limb length discrepancy, and restricted mo­ tion, especially abduction, are significant, albeit not pathognomonic signs. With the infant supine and the pelvis stabilized, abduction to 75° and adduction to 30° should occur readily under normal circum­ stances. The 2 maneuvers for assessing hip stability in the newborn are the Ortolani and Barlow tests. The Ortolani elicits the sensation of the dislocated hip reducing, and the Barlow detects the unstable hip dislocating from the acetabulum. The Ortolani is per­ formed with the newborn supine and the examiner’s index and middle fingers placed along the greater trochanter with the thumb placed along the inner thigh. The hip is flexed to 90° but not more, and the leg is held in neutral rotation. The hip is gently abducted while lifting the leg anteriorly. With this maneuver, a “clunk” is felt as the dislocated femoral head reduces into the acetabulum. This is a positive Ortolani sign. The Barlow provocative test is per­ formed with the newborn positioned supine and the hips flexed to 90°. The leg is then gently adducted while posteriorly directed pressure is placed on the knee. A palpable clunk or sensation of movement is felt as the femoral head exits the acetabulum poste­ riorly. This is a positive Barlow sign. The Ortolani and Barlow maneuvers are performed 1 hip at a time. Little force is required for the performance of either of these tests. The goal is not to prove that the hip can be dislocated. Forceful and repeated examinations can break the seal between the labrum and the fem­ oral head. These strongly positive signs of Ortolani and Barlow are distinguished from a large array of soft or equivocal physical findings present during the newborn period. High-pitched clicks are com­ monly elicited with flexion and extension and are inconsequential. A dislocatable hip has a rather dis­ tinctive clunk, whereas a subluxable hip is character­ ized by a feeling of looseness, a sliding movement, but without the true Ortolani and Barlow clunks. Separating true dislocations (clunks) from a feeling of instability and from benign adventitial sounds (clicks) takes practice and expertise. This guideline recognizes the broad range of physical findings present in newborns and infants and the confusion of terminology generated in the literature. By 8 to 12 weeks of age, the capsule laxity decreases, muscle tightness increases, and the Barlow and Ortolani ma­ neuvers are no longer positive regardless of the sta­ tus of the femoral head. In the 3-month-old infant, limitation of abduction is the most reliable sign as­ sociated with DDH. Other features that arouse sus­ picion include asymmetry of thigh folds, a positive Allis or Galeazzi sign (relative shortness of the femur with the hips and knees flexed), and discrepancy of leg lengths. These physical findings alert the exam­ iner that abnormal relationships of the femoral head to the acetabulum (dislocation and subluxation) may be present. Maldevelopments of the acetabulum alone (ace­ tabular dysplasia) can be determined only by imag­ ing techniques. Abnormal physical findings may be absent in an infant with acetabular dysplasia but no subluxation or dislocation. Indeed, because of the confusion, inconsistencies, and misuse of language in the literature (eg, an Ortolani sign called a click by some and a clunk by others), this guideline uses the following definitions. AMERICAN ACADEMY OF PEDIATRICS 897 • A positive examination result for DDH is the Barlow or Ortolani sign. This is the clunk of dislocation or reduction. • An equivocal examination or warning signs include an array of physical findings that may be found in children with DDH, in children with another or­ thopaedic disorder, or in children who are com­ pletely healthy. These physical findings include asymmetric thigh or buttock creases, an apparent or true short leg, and limited abduction. These signs, used singly or in combination, serve to raise the pediatrician’s index of suspicion and act as a threshold for referral. Newborn soft tissue hip clicks are not predictive of DDH17 but may be confused with the Ortolani and Barlow clunks by some screening physicians and thereby be a rea­ son for referral.