Developmental dysplasia of the hip (DDH) encompasses a spectrum of physical and imaging findings. The child’s hip will not develop normally if it remains unstable and anatomically abnormal by walking age. Therefore, careful physical examination of all infants to diagnosis and treat significant DDH is critical to provide the best possible functional outcome. Regardless of the practice setting, all health professionals who care for newborns and infants should be trained to evaluate the infant hip for instability and to provide appropriate and early conservative treatment or referral.

Keywords

Developmental hip dysplasia

Acetabular dysplasia

Hip subluxation

Hip dislocation

Ortolani maneuver

Swaddling

Key points

Video of the Ortolani maneuver accompanies this article at http://www.pediatric.theclinics.com/

Introduction

Developmental dysplasia of the hip (DDH) encompasses a spectrum of physical and imaging findings, ranging from mild temporary instability to frank dislocation. The child’s hip will not develop normally if it remains unstable and anatomically abnormal by walking age. Therefore, careful physical examination of all infants to diagnosis and treat significant DDH is critical to provide the best possible functional outcome. Regardless of the practice setting, all health professionals who care for newborns and infants should be trained to evaluate the infant hip for instability and provide appropriate and early conservative treatment or referral. Unfortunately, musculoskeletal training in primary care residency programs and postgraduate education has received less attention than the prevalence of the condition warrants. Despite a normal newborn and infant hip examination, a late-onset hip dislocation still occurs in approximately 1 in 5000 infants as well as dysplasia in young adults.

Incidence and risk factors

The incidence of DDH varies from 1.5 to 25.0 per 1000 live births, depending on the criteria used for diagnosis, the population studied, and the method of screening. Relative risk rates are stated in the American Academy of Pediatrics’ (AAP) 2000 clinical practice guidelines, and the overall DDH risk is about 1 per 1000. Traditional risk factors for DDH include breech position, female sex, being the first born, and a positive family history. Breech presentation is probably the most important single risk factor, with DDH reported in 2% to 20% of male and female infants presenting in the breech position.1,2 Frank breech in a girl, with the hips flexed and knees extended, seems to have the highest risk. However, approximately 75% of DDH occurs in female infants without any other identified risk factors, so a careful physical examination of all infants’ hips is required.1

The risk for DDH also depends on environmental factors. Newborn infants have hip and knee flexion contractures because of their normal intrauterine position. These contractures resolve over time with normal developmental maturation. Animal studies have shown that forced hip and knee extension in the neonatal period leads to hip dysplasia and dislocation because of increased tension in the hamstring and iliopsoas muscles that stresses the hip capsule, which may have underlying laxity or instability.3 Comprehensive ultrasound screening during the immediate newborn period has demonstrated hip laxity in approximately 15% of infants.4,5 The combination of capsular laxity and abnormal muscle tension is the most likely mechanism of DDH for infants who are maintained with the lower extremities extended and wrapped tightly together. In contrast, cultures that carry their children in the straddle or jockey position, common in warmer climates, have very low rates of hip dislocation compared with cultures that wrap their infants tightly with the lower limbs together and extended (Fig. 1).6

Natural history

The natural history of mild dysplasia and instability noted in the first few weeks of life is typically benign, with up to 88% resolving by 8 weeks of age.7 However, the natural history of a child’s hip that remains subluxated or dislocated by walking age is poor. Normal development of the hip joint depends on a femoral head that is stable and concentrically reduced in the acetabulum, a requirement for both to form spherically. Looseness or laxity within the acetabulum is termed instability. A nonconcentric position is termed subluxation. The deformity of the femoral head and acetabulum is termed dysplasia. With dislocation or severe subluxation, during the second half of infancy and beyond, limited hip abduction occurs, which the parent may notice during diaper change. As the child reaches walking age, a limp and lower-limb-length discrepancy may be apparent.

With maturity and later in adulthood, patients may develop pain and degenerative arthritis in the hip, knee, and low back. Hip dysplasia, subluxation, and dislocation each have their own natural history. Subluxation may not be as well tolerated as dislocation if arthritis develops in early adulthood from excessive cartilage contact pressure. A completely dislocated hip with the femoral head located in the soft tissue may not cause functional problems other than knee or back pain or limp with limb-length discrepancy if the dislocation is unilateral. Completely dislocated hips, if bilateral with the femoral heads located in the soft tissues, may lead to severe waddling gait but can likewise be surprisingly pain free. Dislocated hips in which the femoral head cartilage is in contact with the bony pelvis may develop early arthritis by the fourth or later decades because of excessive wear of the femoral head cartilage on the pelvic bone. When arthritis develops in early adulthood, the burden of disability is high, with many requiring complex hip replacement at an early age. Over time, other diseases of the hip may occur and confound the natural history and outcome. These diseases includes trauma to the hip, infection, sickle cell disease, Perthes disease, slipped capital femoral epiphysis, and tuberculosis in resource-poor countries.8

Screening for developmental dysplasia of the hip

Screening for DDH is important because the condition may be initially occult, is easily treated when caught early, but difficult to treat later. When detected late, it may lead to long-term disability. Although detection in the neonatal period is ideal, a reasonable goal is to detect the subluxated or dislocated hip by 6 months of age. The physical examination is by far the most important means of detection. Radiography or sonography imaging should be used to confirm the suspicion of DDH. Despite all current methods of screening for DDH, most young adults with dysplasia who require a hip arthroplasty are not detected at birth.9

Physical examination

A proper examination of infants includes observation for lower-limb-length discrepancy, asymmetric thigh or gluteal folds, Ortolani sign or maneuver, and limited or asymmetric abduction.10...