Developmental Dysplasia of the Hip From Birth to Six Months

232 The term “developmental dysplasia or dislocation of the hip” (DDH) refers to the complete spectrum of abnormalities involving the growing hip, with varied expression from dysplasia to subluxation to dislocation of the hip joint. Unlike the traditional term “congenital dysplasia or dislocation of the hip,” the designation DDH has been officially endorsed by the American Academy of Orthopaedic Surgeons, the American Academy of Pediatrics, and the Pediatric Orthopaedic Society of North America because it is not restricted to congenital dislocation of the hip and includes developmental problems of the hip.1,2 This more comprehensive term refers to alterations in hip growth and stability in utero, in the newborn period, and in the neonatal period that may result in dysplasia, ranging from subluxation to dislocation of the joint. Although congenital dysplasia or dislocation of the hip is the most common subset of disorders under the rubric DDH, the term also refers to hip disorders associated with neurologic disorders (e.g., myelomeningocele), connective tissue disorders (e.g., Ehlers-Danlos syndrome), myopathic disorders (e.g., arthrogryposis multiplex congenita), and syndromic conditions (e.g., Larsen syndrome). None of the hip abnormalities associated with those less common conditions is precisely or adequately addressed by the term congenital dislocation of the hip. The term “dysplasia” denotes an abnormality in development, such as an alteration in size, shape, or organization. Hip-joint dysplasia refers to alterations in the structure of the femoral head, the acetabulum, or both. The well-developed cup-shaped structure is absent in acetabular dysplasia and is replaced by a shallow saucer-shaped acetabulum that is not congruent with the femoral head. Dysplasia of the infant femoral head is difficult to evaluate radiographically because the proximal femoral ossific center does not appear until 4 to 7 months of age. Technological advances and