ACR Appropriateness Criteria® on Developmental Dysplasia of the Hip—Child

Definition 

Developmental dysplasia of the hip (DDH), formerly known as congenital dislocation of the hip, comprises a spectrum of abnormalities, including abnormal acetabular shape (dysplasia) and malposition of the femoral head, ranging from dislocatable hip and mild subluxation to fixed dislocation.

Incidence 

Developmental dysplasia of the hip affects 1.5 in 1,000 of the American caucasian population; it less frequently affects African Americans. It is 4 to 8 times more common in female individuals. It is also more common in patients with family histories of DDH, firstborns, large infants, and infants with histories of oligohydramnios. It is 3 times more common in the left hip than the right, likely because of the normal left occiput anterior position in utero, which places the left hip against the mother's spine and limits its abduction.

Etiology 

The origin and pathogenesis of DDH are probably multifactorial. Abnormal laxity of the ligaments and hip capsule is seen in patients and families with DDH. The maternal hormone relaxin may also be a factor. Mechanical factors of reduced in utero space and movement restriction are thought to be causative in conditions such as oligohydramnios and being first born. Extreme hip flexion with knee extension, as in breech position, tends to promote femoral head dislocation and leads to shortening and contracture of the iliopsoas muscle.

Natural History 

The natural history of DDH depends on the type and degree of hip abnormality. Mild dysplasia may never manifest clinically or become apparent until adult life, whereas severe dysplasia is most likely to present clinically during childhood. Most DDH identified during the newborn period represents hip laxity and immaturity. Sixty percent to 80% of abnormalities identified on physical examination and >90% identified on ultrasound resolve spontaneously [1, 2, 3, 4, 5]. Untreated subluxed and dislocated hips can lead to early degenerative joint disease and impaired function.

Diagnosis 

The diagnosis of DDH may be made by clinical examination or by imaging methods such as radiography or ultrasound. The timing and the selection of patients requiring imaging evaluation are controversial (Variant 1, Variant 2, Variant 3, Variant 4, Variant 5).

Variant 1. Patient aged < 4 months, positive physical findings (Ortolani or Barlow maneuver)

	Radiologic Procedure	Rating	Comments	RRL
	Ultrasound hips bilateral	7	Prefer to wait until the patient is aged ≥ 2 weeks to perform the ultrasound	None
	X-ray hips bilateral	2	Anteroposterior view	Medium

Note: Rating scale: 1 = least appropriate, 9 = most appropriate. RRL = relative radiation level.

Variant 2. Patient aged < 4 months, equivocal physical findings

	Radiologic Procedure	Rating	Comments	RRL
	Ultrasound hips bilateral	8	Prefer to wait until the patient is aged ≥ 2 weeks to perform the ultrasound	None
	X-ray hips bilateral	2	Anteroposterior view	Medium

Note: Rating scale: 1 = least appropriate, 9 = most appropriate. RRL = relative radiation level.

Variant 3. Patient aged < 4 months, breech presentation or positive family history, without physical findings

	Radiologic Procedure	Rating	Comments	RRL
	Ultrasound hips bilateral	6	Prefer to wait until the patient is aged ≥ 2 weeks to perform the ultrasound	None
	X-ray hips bilateral	2	Anteroposterior view	Medium

Note: Rating scale: 1 = least appropriate, 9 = most appropriate. RRL = relative radiation level.

Variant 4. Patient aged ≥ 4 months, clinically suspicious for developmental dysplasia of the hip (limited abduction or abnormal gait)

	Radiologic Procedure	Rating	Comments	RRL
	X-ray hips bilateral	8	Anteroposterior view	Medium
	Ultrasound hips bilateral	3		None

Note: Rating scale: 1 = least appropriate, 9 = most appropriate. RRL = relative radiation level.

Variant 5. Clinically suspicious for teratogenic dysplasia

	Radiologic Procedure	Rating	Comments	RRL
	X-ray hips bilateral	8	Anterioposterior view	Medium
	Ultrasound hips bilateral	5		None

Note: Rating scale: 1 = least appropriate, 9 = most appropriate. RRL = relative radiation level.

Clinical Evaluation 

The clinical evaluation of the hips for DDH should be performed at each well-baby visit. The American Academy of Pediatrics recommends well-baby visits at 1 to 2 weeks and at 2, 4, 6, 9, and 12 months of age. As part of the clinical evaluation, it is important to elicit risk factors for DDH. Examination findings suggesting DDH include positive Ortolani or Barlow test results, asymmetric skin folds, and shortening of the thigh observed on the dislocated side. The Ortolani test consists of abducting and gently lifting the flexed thigh and pushing the greater trochanter anteriorly; this test is designed to enable the already dislocated hip to be detected by causing the femoral head to slip into the acetabulum; a “clunk” should be felt or heard. The second test, introduced by Barlow, consists of a gentle maneuver, with the thumb of one hand placed over the femoral neck and the fingers placed over the greater trochanter to try to 1) gently adduct the thigh and dislocate the femoral head posteriorly and then 2) gently lift the thigh upward while abducting the leg with the fingers over the greater trochanter, endeavoring to relocate the femoral head in its socket. The Barlow test aims to elicit a dislocation followed by reduction and identifies unstable hips missed by the Ortolani test. Both tests are designed to detect instability between the femoral head and acetabulum, indicating ligamentous or capsular laxity.

In children aged >3 months, these tests are less likely to have positive results. In children aged >3 months, limitation of hip abduction and asymmetric thigh folds secondary to shortening are more useful clinical signs of DDH. Once a child is walking, there is a typical limp, and the child often toe-walks on the affected side. If both hips are dislocated, increased lumbar lordosis, prominent buttocks, and a waddling gait pattern are present. The physical examination may reveal a stable “clicking” hip, that is, a hip with no laxity but with a “click” elicited on the physical examination. The sensitivity and specificity of the clinical examination depend on the expertise of the evaluator. The effectiveness of clinical screening varies, depending on whether an orthopedic surgeon, experienced pediatrician, or intern performs the examination [6, 7, 8].

Radiographic Evaluation 

In the first month of life, when the femoral heads are composed entirely of cartilage, radiographs are of limited value unless a dislocation is present. Instability may be undetectable, and evaluation of acetabular development is influenced by the infant's position at the time the x-ray is taken. By 4 to 6 months of age, radiographs become more reliable (see Variant 4). They are readily available and relatively low in cost. Radiographs may be performed on patients with neuromuscular disorders, myelodysplasia, or arthrogryposis (teratologic dislocation) to assess other bony abnormalities.

Radiography of the pelvis should be obtained with the hips in the neutral position. The von Rosen view, with the legs at a 45° angle, abduction, and the thighs internally rotated, may be helpful in accentuating a dislocated hip that may not be apparent on routine views. The frog-leg view may be obtained to assess reduction when the neutral view is abnormal.

Dislocation or subluxation of the femoral head can be recognized by evaluating the relationship of the ossific nucleus of the femoral head and metaphysis to the acetabulum. The nucleus of the femoral head ossifies at approximately 4 months (50th percentile), with a normal range of 2 to 8 months [9]. The ossified femoral head nucleus allows easy evaluation of the relationship of the femoral head to the acetabulum. However, if the nucleus of the femoral head is not ossified, its position can be estimated. In addition to evaluating the relationship of the ossific nucleus of the femoral head, the relationship of the proximal femoral metaphysis to the acetabulum must also be evaluated [10].

As a child grows, adaptive changes of the hip joint and femur become more evident on routine radiography. In DDH, the roof of the acetabulum is vertically oriented, and often there is a delay in the appearance and growth of the ossific nucleus of the femoral head, compared to the normal hip.

The radiographic evaluation consists predominantly of a visual assessment; however, measurement of the acetabular index is an objective parameter that may be used in the diagnosis and follow-up of patients with DDH. The 95% tolerance interval for intraobserver variability is 8.35°, with interobserver variability exceeding intraobserver variability; this measurement error casts doubt on the reliability of the acetabular index based on a single reading [11, 12].

Ultrasound Evaluation 

A high-frequency linear array transducer should be used for ultrasound evaluation of the hip. Two methods have emerged: an acetabular morphology method proposed by Graf [13] and a dynamic stress technique.

In 1980, Graf [13] described a method of static ultrasound imaging in the coronal plane. In normal hips, the round, hypoechoic, speckled femoral head lies centered in the acetabulum. The Graf method is based on a single coronal image. The position of the femoral head, appearance of the bony acetabulum, and configuration of the cartilaginous acetabular rim, position of the cartilaginous labrum, and shape and echogenicity of the cartilaginous roof are all assessed, and the hip is assessed visually. An important adjunct in the evaluation of the hips by this method is the α angle. This angle is obtained by drawing a line along the lateral aspect of the ilium and another line from the lower iliac margin in the acetabular fossa to the lateral edge of the bony acetabular roof [14, 15].

Graf [13] developed a morphologic and geometric hip classification scheme (types I to IV) using an α angle, which measures the osseous acetabular roof angle, and a β angle, which defines the position of the echogenic fibrocartilaginous acetabular labrum. The hips are categorized according to the following classification:

Interobserver variability of subjective evaluation and of acetabular angle measurements [16, 17, 18, 19] raises concerns about the operator dependence of ultrasound evaluation for DDH and may explain the variability of ultrasound screening positive rates found in the literature.

Harcke and Grissom [20] and others developed the dynamic or real-time method, which attempts to visualize the Barlow and Ortolani maneuvers on ultrasound. This technique is performed in both the coronal and transverse planes, with and without stress. The modified Barlow maneuver is performed by holding the knee with the hip flexed 90° and in adduction. The femur is pushed (pistoned) posteriorly.

In 1993, at a meeting at the Alfred I. DuPont Institute in Wilmington, Delaware, a North American standard for hip ultrasound was agreed upon, which combines the two techniques. The standard consists of 1) a coronal view in the Graf format and 2) a transverse view with the hip flexed, with and without modified Barlow stress maneuver [14].

Other Imaging Modalities 

Computed tomography and magnetic resonance imaging may be used to evaluate DDH in patients in casts after surgery or attempted closed reduction to confirm that the hip has been successfully reduced, late presentations, complex hip dislocations, or avascular necrosis. The primary use of computed tomography in DDH is for follow-up purposes rather than for initial diagnosis. Magnetic resonance imaging may be used in complex dislocations and suspected avascular necrosis. Arthrography is used primarily in the operating room by the orthopedic surgeon to evaluate lateral displacement of the femoral head and congruity after closed reduction of the hip and to assess for labral infolding that might prevent proper reduction.

Timing of Evaluation 

The goal of a screening program is to detect all patients with DDH early on, when therapy is most effective and noninvasive, and to eliminate those patients without DDH in whom unnecessary treatment may be costly and harmful. Delayed diagnosis increases the risk for complications, and infants diagnosed after 6 months of age often require surgical correction. Two types of screening can be performed: generalized screening, in which all neonates are evaluated, and selective screening, in which only those at high risk are evaluated.

Generalized Screening 

Selective Screening 

Treatment 

It is widely assumed that early treatment results in improved outcome. Although there is agreement in the literature that patients with dislocation should be treated and that those with stable “clicking” hips should be followed clinically, there is some disagreement regarding the treatment of patients with unstable (lax, but not displaced) hips. Some advocate early treatment for every patient with instability [38]. Others prefer clinical observation [39] because a significant number of these patients (80%) progress spontaneously to clinically normal status [40].