IMAGING OF DEVELOPMENTAL DYSPLASIA OF THE HIP

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The purposes of this review are to help readers better understand hip dysplasia and to give specific guidelines as to how imaging aids in the diagnosis and follow-up of children suspected of or known to have developmental dysplasia of the hip (DDH).

Congenital dysplasia of the hip was the term formerly used to describe hip dysplasia in the young infant and child. The preferred description is now DDH, reflecting that not all dysplasia is present at birth.7, 13, 19 In recent years various medical organizations have suggested this change in nomenclature to more accurately describe the pathogenesis of hip dysplasia. Some children truly develop DDH after birth during the first months of life (Fig. 1). This change in terminology helps eliminate the blame placed on pediatricians or neonatologists who performed the neonatal hip examination of a child later found to have DDH.

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ETIOLOGY

The etiology of DDH is complex, with factors affecting both acetabular morphology and hip stability. If a shallow cartilaginous acetabulum provides poor structural support to the femoral head, the head is allowed to move, and stretching of the supporting ligamentous structures occurs. Alternatively, if the acetabular shape is adequate but the ligamentous support is lax, excess motion will cause deterioration of the acetabulum and progress to dysplasia. These two mechanisms are closely related.34

INCIDENCE AND DIAGNOSIS

In 1961, Palmen reported that 20 in 1000 newborns had unstable hips when stressed.24 Barlow, in 1962, found that 58% of neonatal instability spontaneously resolved by 7 days and 80% by 2 months.1 Although the numbers vary, the prevalence of dislocation is approximately 1.3 in 1000, and that of dislocatable hips requiring treatment is about 1.2 in 1000 newborns in North America and Western Europe. The majority of these are detectable by the Ortolani and Barlow clinical examinations. Imaging

RADIOGRAPHIC IMAGING

The hip can be evaluated with plain films, ultrasound, computed tomography (CT), and magnetic resonance (MR) imaging. Acquiring the information necessary for diagnosis, treatment, preoperative planning, and postoperative evaluation may require a combination of techniques that are complementary. The choice of study depends on the age of the child, the information sought, the expertise of the radiologist, and often the preferences of the orthopedic surgeon.

CT

CT is used in two settings for children with DDH. If a child is placed in a spica cast, the ultrasound window is usually too small to adequately image the hip. As an alternative, CT is used to document reduction (Fig. 4).16 A low-dose technique is employed to minimize radiation yet obtain diagnostic images.8 CT also is performed in children with severely dysplastic hips as a preoperative study to help the orthopedic surgeon plan the proper corrective procedures. Three-dimensional images,

Clinical Screening

Early detection of hip dysplasia has been a topic of interest since the mid-1900s. Roser30 first described that “flail hips could be dislocated by adduction of the leg and then reduced again by abduction.” Ortolani, however, deserves the credit for his 1939 description of the abduction “scatto” or snapping of a dislocated hip. Through his educational efforts, this test that bears his name is now part of widespread clinical screening for DDH. Barlow,1 Palmen,24 and others contributed

Neonatal Period

Neonates with abnormal physical examination need immediate attention with referral to an orthopedic surgeon (Fig. 8). Treatment using abduction devices is generally successful in the neonatal period, when the cartilaginous structures are growing rapidly and are pliable. If, in the judgment of the treating physician, an abduction harness is indicated, then ultrasound imaging is not necessary. Neonates with a hip “click” or an equivocal examination should be evaluated with ultrasound at 4 to 6

Abduction Harness

Soft abduction splints, such as the Pavlik harness, are used in young children to treat DDH. After reduction, if the hips are stable to clinical examination, there may be no need to document the hip position radiographically. If the hips are severely dysplastic and maintaining reduction is difficult, then radiographic documentation of hip position is advisable. Continued dislocation of a hip while in Pavlik harness stretches the posterior capsule and reduces chances of maintaining good

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  • Cited by (34)

    • CT in children's bones and joints: When, how and common findings

      2013, European Journal of Radiology
      Citation Excerpt :

      Acetabular dysplasia and abnormal position of the femoral head are the most important clinical features, resulting in abnormal growth of the involved skeletal parts [31]. Orthopaedic examination, plain film (in the older patient) and US (in neonates and infants) are sufficient to establish the diagnosis [32]. A potential role of CT in preoperative planning is to identify obstacles to closed reduction, such as hypertrophy of the pulvinar fat and an inverted labrum [33].

    • MR imaging of osseous lesions of the hip

      2013, Magnetic Resonance Imaging Clinics of North America
      Citation Excerpt :

      Lax ligamentous support to the hip may also allow excessive motion and facilitate the dysplasia. Morphologic changes may occur in a newborn or during the early hip development, and the term congenital hip dysplasia should be avoided.18 The acetabular deformity shifts the expected vertical component of the hip joint force away from the acetabular bone surface toward the superolateral capsular-labrum-complex, which acts as a secondary stabilizer, leading to excessive tension and shear stresses.19

    • Strategies to Improve Nonoperative Childhood Management

      2012, Orthopedic Clinics of North America
      Citation Excerpt :

      It should be remembered that 4 to 6 mm of subluxation is normal during the first few days of life.38 If the hip subluxates or dislocates, reduction is attempted (the Ortolani maneuver).33–36 The morphologic technique provides information related to the development of the femoral head and the acetabulum.

    • Diseases of the Hip

      2008, Pediatric Emergency Medicine
    • Developmental Dysplasia of the Hip

      2007, Pediatric Clinical Advisor
    • Diseases of the Hip

      2007, Pediatric Emergency Medicine
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    Address reprint requests to James S. Donaldson, MD, The Children's Memorial Hospital, Department of Radiology #9, 2300 Children's Plaza, Chicago, IL 60614

    *

    From the Department of Radiology, Northwestern University Medical School, Children's Memorial Medical Center; and the Department of Radiology, The Children's Memorial Hospital, Chicago, Illinois

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