Dysplasia of the Hip

Fig. 38.1

Extremely tight swaddling, in which the hips are forcefully maintained in extension and adduction, increases the risk of DDH. This infant is from the Amazon region of Ecuador, South America

../images/270913_2_En_38_Chapter/270913_2_En_38_Fig2_HTML.png — Fig. 38.2

(a, b) Carrying an older infant or young child on the back with hips abducted encourages healthy development of the hip. ((b) Courtesy of Byron McCord, MD)

Looseness of the femoral head within the acetabulum is termed instability. Nonconcentric position is subluxation, and deformity of the femoral head and acetabulum is dysplasia. The natural history of instability noted in the first few weeks of life is typically benign, and many cases resolve by 8 weeks of age. Conversely, the natural history of a hip that is subluxated or dislocated at walking age is poor.

With time, the child with DDH develops a limp, limb length discrepancy, and limited hip abduction. With bilateral dislocations the child will have lumbar hyperlordosis in addition to an abductor lurch (Fig. 38.3). With maturity the adult patient can develop painful, early-onset degenerative arthritis. Subluxation is often not as well tolerated as frank dislocation. Patients with balanced bilateral hip dislocations, or those who have not yet formed a false acetabulum, may have many years of pain-free ambulation. Other diseases of the hip may occur over the child’s lifetime and confound the natural history and outcome, including trauma, sickle cell disease, tuberculosis, and Perthes [1].

../images/270913_2_En_38_Chapter/270913_2_En_38_Fig3_HTML.jpg — Fig. 38.3

This boy with bilateral DDH ambulates with an abductor lurch on both sides, in which his trunk shifts laterally over each hip during stance phase. He also has increased lumbar lordosis because of coexisting hip flexion contractures, noted by his protuberant abdomen

Clinical Assessment

The physical examination in infants focuses on instability (Ortolani and Barlow maneuvers), whereas the exam in children older than 3 months identifies secondary changes including loss of passive abduction, shortening of the thigh with or without an extra thigh fold (Fig. 38.4), and leg length discrepancy or limp. The Ortolani maneuver gently reduces the subluxated or dislocated femoral head into the acetabulum by hip abduction [2] and is the basis of the proper examination of the newborn hip. This maneuver begins with the hip in an adducted position. The examiner’s hand holds the thigh loosely, with the index and middle fingers on the area of the greater trochanter and the thumb along the medial thigh. The hip is gently abducted while applying an anteriorly directed force through the trochanteric region, sensing whether the hip reduces. The Barlow maneuver assesses whether a reduced hip can be displaced by placing the hip in adduction and gently applying a posteriorly directed force to the proximal anterior thigh.

../images/270913_2_En_38_Chapter/270913_2_En_38_Fig4_HTML.jpg — Fig. 38.4

Extra thigh fold on right from femoral shortening associated with dislocation

Plain radiography becomes useful by 4–6 months of age, when the secondary center of ossification of the femoral head forms. Radiographic hip screening should be considered for the infant with risk factors for DDH or if diagnoses such as congenital short femur, proximal focal femoral deficiency, septic arthritis, or coxa vara are suspected.

The American Academy of Pediatrics recently published their revised guidelines for evaluation and referral of DDH in infants [3]. The authors believe screening is worthwhile to prevent a subluxated or dislocated hip by 12 months of age. The principles of prevention and early detection applied to all levels of health systems are outlined in Box 38.1.

Box 38.1 Principles for Evaluation and Referral of DDH

Physical examination of the infant hip including the Ortolani test is the primary basis of early detection.
Ultrasound to confirm dislocation, subluxation or dysplasia and the effects of treatment. Radiographs to confirm physical exam and for at risk hips when quality ultrasonography is not available (AP pelvic x-ray at 4–6 months).
Minor hip abnormalities on physical examination or imaging can resolve spontaneously, but the infant should be followed up on an individual basis.
Referral to an orthopedic specialist based on an unstable Ortolani exam alone at any age or asymmetric hip abduction after the neonatal period.
Although no screening program can completely eliminate DDH, periodic hip examinations during infancy can greatly reduce the risk of a dislocated hip at 1 year.
Tight swaddling of the hips should always be avoided and is most important for primary prevention [4].