When to Order Imaging for Developmental Dysplasia of the Hip-Child: ACR Appropriateness Decoded

When to Order Imaging for Developmental Dysplasia of the Hip-Child: ACR Appropriateness Decoded

You’re in a busy pediatric clinic evaluating a 6-week-old infant for a well-child check. The physical exam reveals a positive Barlow sign, raising suspicion for Developmental Dysplasia of the Hip (DDH). The next step is imaging, but the optimal modality depends critically on the patient’s age and the specific clinical question. Choosing between ultrasound and radiography isn’t just about preference; it’s about diagnostic accuracy and radiation safety. This guide decodes the American College of Radiology (ACR) Appropriateness Criteria to help you select the right study at the right time.

What Does ACR Developmental Dysplasia of the Hip-Child Cover?

This ACR guideline focuses on imaging for the initial evaluation and nonoperative surveillance of Developmental Dysplasia of the Hip in infants and young children. The recommendations are stratified by the child’s age and the findings on physical examination, from equivocal findings or risk factors (like breech presentation or family history) to definitive clinical signs of instability. The criteria address initial diagnostic imaging as well as follow-up imaging for children being treated nonoperatively, for example, with a Pavlik harness. This topic does not cover imaging for other pediatric hip conditions such as septic arthritis, Legg-Calvé-Perthes disease, or slipped capital femoral epiphysis. It also does not address postoperative imaging, which involves different clinical considerations and imaging protocols.

What Imaging Should I Order for Developmental Dysplasia of the Hip-Child? Recommendations by Clinical Scenario

The choice of imaging for suspected DDH is highly age-dependent, reflecting the developmental changes in the infant hip as cartilage ossifies into bone.

For a newborn younger than 4 weeks of age with an equivocal physical examination or risk factors for DDH, the ACR rates both hip ultrasound and pelvis radiography as Usually not appropriate. Imaging at this early stage is often avoided due to physiologic ligamentous laxity and immaturity of the acetabulum, which can lead to false-positive results. Clinical follow-up is typically preferred.

Once the child is between 4 weeks and 4 months of age with an equivocal exam or risk factors, or for any child younger than 4 months with clear physical findings of DDH, the recommendation shifts. In these scenarios, US hips is rated Usually appropriate. Ultrasound is the ideal modality in this age group as it provides excellent visualization of the cartilaginous femoral head and its relationship to the acetabulum without using ionizing radiation. Pelvis radiography remains Usually not appropriate because the femoral head has not yet ossified, making it invisible on x-ray.

A transition occurs between 4 to 6 months of age. For a child in this age range with concern for DDH, Radiography pelvis becomes Usually appropriate. As the capital femoral epiphysis begins to ossify, radiographs become more reliable for assessing hip morphology and stability. US hips is downgraded to May be appropriate, as it can still be useful but becomes technically more challenging and less reproducible with increasing ossification.

For a child older than 6 months of age with concern for DDH, Radiography pelvis is clearly the modality of choice and is rated Usually appropriate. At this stage, the ossific nucleus is well-formed, allowing for accurate measurements like the acetabular index via Hilgenreiner and Perkin lines. Hip ultrasound is considered Usually not appropriate.

For surveillance imaging in a child younger than 6 months with a known diagnosis of DDH undergoing nonoperative treatment in a harness, US hips is rated Usually appropriate. It allows for dynamic assessment of hip stability and monitoring of treatment progress without repeated radiation exposure. All other modalities, including radiography, MRI, and CT, are rated Usually not appropriate for routine surveillance in this context.

ACR Imaging Recommendations Table

Adult vs. Pediatric Developmental Dysplasia of the Hip-Child Imaging: Radiation Dose Tradeoffs

This ACR topic is exclusively pediatric, and the imaging recommendations are tailored to the unique anatomy and radiation sensitivity of infants and young children. The principle of As Low As Reasonably Achievable (ALARA) is paramount. Ultrasound is heavily favored in infants under 4-6 months precisely because it involves no ionizing radiation (0 mSv) and is highly effective at visualizing the unossified, cartilaginous structures of the infant hip. As the femoral head ossifies, radiography becomes necessary for accurate diagnosis. While pelvis radiography involves a low dose of radiation (0.03-0.3 mSv [ped]), the decision to use it is weighed against the decreasing utility of ultrasound. The goal is to minimize cumulative radiation exposure over a child’s lifetime. Advanced imaging like CT or MRI is rarely used for initial diagnosis or routine surveillance due to higher radiation dose (for CT) or the need for sedation (for MRI), and is reserved for complex cases or preoperative planning.

Imaging Protocol Details for Developmental Dysplasia of the Hip-Child

Once you’ve decided on the right study, the protocol matters. For radiography, proper positioning is critical to avoid misinterpretation of acetabular angles. For ultrasound, a standardized dynamic technique (e.g., Graf method) is essential for reproducibility. Our protocol guides cover technique, contrast, and reading principles for the studies recommended above. While CT is not a first-line imaging choice for initial diagnosis, understanding its protocol is relevant for complex cases or other clinical scenarios.

• CT Chest/Abdomen/Pelvis with IV Contrast

Tools to Help You Order the Right Study

Navigating imaging guidelines can be complex. GigHz offers a suite of tools designed to support evidence-based clinical decisions and streamline your workflow.

For clinical scenarios beyond Developmental Dysplasia of the Hip-Child, the ACR Appropriateness Criteria Lookup provides instant access to the full library of ACR guidelines, helping you find the right study for thousands of clinical variants.

To ensure studies are performed correctly, the Imaging Protocol Library offers detailed, step-by-step protocols for a wide range of imaging procedures, standardizing care and improving diagnostic quality.

To help manage and communicate radiation exposure with families, the Radiation Dose Calculator is a valuable tool for estimating cumulative dose and explaining relative radiation levels in an understandable way.

What is the best initial imaging test for a 2-month-old with a hip click?

For a 2-month-old infant (between 4 weeks and 4 months), the most appropriate initial imaging test is a hip ultrasound (US). The ACR rates US hips as “Usually appropriate” in this age group. Ultrasound is ideal because it does not use ionizing radiation and provides excellent visualization of the cartilaginous femoral head and its stability within the acetabulum.

Why is a hip x-ray not recommended for a 3-week-old infant?

In an infant younger than 4 weeks, both ultrasound and x-ray are rated “Usually not appropriate.” This is because newborns often have physiologic ligamentous laxity that can mimic true dysplasia, leading to false-positive results and unnecessary treatment. An x-ray is particularly unhelpful because the key anatomical structure, the femoral head, is still made of cartilage and is therefore not visible on a radiograph. Clinical re-evaluation after 4-6 weeks of age is the standard approach.

At what age does radiography become the preferred imaging for DDH?

Radiography (x-ray) of the pelvis becomes the preferred, “Usually appropriate” imaging modality starting around 4 to 6 months of age. By this time, the ossific nucleus of the femoral head has typically appeared, making it visible on x-ray and allowing for reliable measurements of hip alignment and acetabular development.

Is an MRI ever used for diagnosing DDH?

MRI is rated “Usually not appropriate” for the initial diagnosis or routine nonoperative surveillance of DDH. Its primary role is in complex cases, for preoperative planning before a closed or open reduction, or for postoperative assessment to confirm reduction and evaluate for complications like avascular necrosis. It is not a first-line tool due to its cost and the frequent need for sedation or anesthesia in young children.

What are the key risk factors for DDH that might prompt imaging?

Key risk factors that should lower the threshold for imaging (typically an ultrasound between 4 weeks and 4 months of age) include breech presentation, a positive family history of DDH, and female sex. The presence of these factors, even with a normal physical exam, may warrant imaging to screen for dysplasia.

How is imaging used to monitor a baby in a Pavlik harness?

For an infant under 6 months being treated with a Pavlik harness, hip ultrasound is the “Usually appropriate” method for monitoring treatment. It is performed periodically to assess the position and stability of the femoral head within the acetabulum. This allows the physician to confirm the harness is effective and to monitor for improvement over time, all without exposing the infant to ionizing radiation.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 12, 2026