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.
Key points
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Research over the past decade has reinforced most of the principles and recommendations of the 2000 American Academy of Pediatrics’ Clinical Practice Guideline : Early Detection of Developmental Dysplasia of the Hip .
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A reasonable goal for the primary care physician should be to prevent hip subluxation or dislocation by 6 months of age using the periodic examination.
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The Ortolani maneuver, in which a subluxated or dislocated femoral head is gently reduced into the acetabulum with hip abduction by the examiner, is the most important clinical test for detecting dysplasia in the newborn.
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Safe swaddling, in which the hips are not extended and does not restrict hip motion, does not increase the risk for developmental hip dysplasia.
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Despite best practice, young adults will still present with hip dysplasia that was not detected at birth.
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.
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. 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.
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. Comprehensive ultrasound screening during the immediate newborn period has demonstrated hip laxity in approximately 15% of infants. 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 ).
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. 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.
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.
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. The Ortolani maneuver, in which a subluxated or dislocated femoral head is gently reduced into the acetabulum with hip abduction by the examiner, is the most important clinical test for detecting dysplasia in the newborn. The Ortolani maneuver is a continuous smooth examination starting with the hip flexed and adducted with gentle anterior pressure on the trochanter followed by gently abducting the hip while sensing (termed Segno dello scotto ) whether the hip slips into the acetabulum over the hypertrophied articular cartilage ( [CR] ). It answers the essential question: Is the femoral head dislocated and can it be reduced into the acetabulum? The examiner should not forcefully attempt to dislocate the femoral head. Although the Ortolani sign represents the palpable sensation of the femoral head moving into the acetabulum over the hypertrophied rim of the acetabular cartilage (termed the neolimbus ), isolated high-pitched clicks represent the movement of myofascial tissues from the trochanter, knee, or other soft tissue.
By about 3 months of age, a dislocated hip may become less mobile on physical examination, thus, limiting the usefulness and sensitivity of the Ortolani maneuver. However, at this time, restricted, asymmetric hip abduction becomes an important finding of hip dysplasia. Diagnosing bilateral DDH in older infants can be difficult because of the symmetry present when there is bilateral limited hip abduction. Other signs of a dislocated hip that are noticeable as infants reach walking age are a proximal thigh crease, a positive Galeazzi sign (in which the hips and knees are flexed 90° and the knee on the dislocated side appears lower), a wider-appearing perineum, a more prominent hip curvature, and a more proximally located posterior knee crease. By walking age, infants may have a delay in walking, a Trendelenburg limp, and a bilateral waddling gait if both hips are dislocated. On the other hand, mild hip dysplasia may have no symptoms or physical findings in infants or older children.
Radiography
Plain radiography becomes most useful by 4 to 6 months of age, when the femoral head’s secondary center of ossification (ossific nucleus) forms, a finding that occurs earlier in female infants. A single anteroposterior (AP) view of the entire pelvis is obtained, with positioning of the pelvis without rotation ( Fig. 2 ). Acetabular dysplasia, subluxation, and dislocation are easily detected on the radiographs if taken after the femoral head’s ossific nucleus has appeared. If subluxation or dislocation is noted, an AP view of the pelvis with the hips abducted can be done to document hip reducibility. However, there is debate whether minor radiographic variability in young infants (increased acetabular index) constitutes actual disease. Radiographic hip screening is traditionally indicated for infants with risk factors, such as a history of breech presentation or an abnormal physical examination at 4 months of age. An AP radiograph of the pelvis is obtained in newborns or infants if other conditions, such as congenital short femur, proximal focal femoral deficiency, septic hip infection, or coxa vara, are suspected.
Ultrasonography
The American Institute of Ultrasound in Medicine (AIUM) and the American College of Radiology (ACR) have published a joint guideline for the standardized performance of the infantile hip ultrasound. Ultrasonography can provide detailed static and dynamic imaging of the hip before femoral head ossification. Ultrasound hip imaging can be universal for all infants or selective for those at risk for having DDH. Because disease prevalence is low at 1% to 2%, universal ultrasound screening is not generally practiced in North America or in countries with limited resources. Many barriers to successful ultrasound screening programs in the United States include expense, lack of availability, lack of trained personnel to assure quality imaging and interpretation, inconvenience, subjectivity, a high false-positive rate, and controversy about effectiveness.
Universal ultrasound screening of all infants is practiced in many European countries, with programs typically showing a decrease in the number of hips needing surgical reduction after their programs were begun. Most recently, a large randomized controlled study of universal or selective ultrasound screening in Norway that was compared with a well-done physical examination showed higher treatment rates but no significant decrease in late cases of DDH. This same group of patients who underwent ultrasound screening and were followed to skeletal maturity did not have less acetabular dysplasia or degenerative change, although there was also no increased rate of avascular necrosis. Despite this screening program for DDH, 92% of young adults with hip dysplasia who required a total hip arthroplasty were not detected at birth. Results of these quality studies indicate that a well-performed physical examination in infants is the most important means of detecting instability; however, dysplasia is currently undetectable at birth for many adults.
In countries with very limited resources, even selective ultrasound screening is not typically available. The lack of ultrasound screening in low-income countries does not necessarily restrict the delivery of quality care for detecting and treating DDH. In these countries, primary prevention through education about proper swaddling, early detection with a properly performed physical examination by trained health care workers and early safe conservative treatment are the basis of an effective DDH program. Similar to the emphasis on conservative clubfoot treatment in countries with limited resources, education, primary prevention, early detection and treatment are need to be developed ( http://hipdysplasia.org ). Despite successful early prevention, undetected genetically determined acetabular dysplasia may still present in the young adult.
Ultrasound screening should not be performed before 3 to 4 weeks of age in infants with clinical signs or risk factors for DDH because of the normal physiologic laxity that typically resolves by 6 weeks of age. Most minor sonographic hip anomalies seen at 4 weeks to 4 months of age will resolve spontaneously. These anomalies include minor changes in morphology and subluxation ( uncoverage ) with stress maneuvers. Proper timing, performance, and interpretation of infantile hip ultrasound imaging per the guidelines of the AIUM and the ACR is critical to avoid undertreatment or overtreatment. If available, ultrasound imaging can be used to guide the reduction of a dislocated hip in infants who are being treated in a Pavlik harness or other hip abduction orthosis ( Fig. 3 ). With the current medicolegal climate that fosters defensive medicine, widespread ultrasonography has become the default ordered test, resulting in excessive referral and treatment as well as poor use of limited resources for infants with very mild dysplasia or laxity. Developing local/regional criteria for screening imaging and referral based on best resources, especially for ultrasonography, should promote more uniform and cost-effective treatment.
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