What is the next most appropriate step for a 12-year-old boy with chronic right groin pain, hypothyroidism, and normal vital signs, who experiences pain with movement of the hip?

X-ray is the Most Appropriate Next Step for a 12-Year-Old Boy with Chronic Hip Pain

X-ray of the hip and pelvis should be obtained as the first imaging test for this 12-year-old boy with chronic right groin pain and pain with hip movement. 1

Clinical Presentation Analysis

This patient presents with:

• 12-year-old boy
• Right groin pain for three months (chronic)
• Known hypothyroidism
• Height in 50th percentile, weight in 90th percentile
• Normal vital signs
• Pain with hip movement

Diagnostic Approach

Initial Imaging

The American College of Radiology Appropriateness Criteria for chronic hip pain clearly recommends radiographs as the first imaging test in most, if not all, cases of chronic hip pain 1. This recommendation applies to pediatric patients with chronic hip pain as well.

Key reasons for starting with radiographs:

• Provides screening for common disorders such as arthritis or bone tumors
• Serves as an excellent baseline for comparison with more advanced imaging if needed
• Helps guide selection of additional imaging techniques if necessary
• Can provide specific information about bony abnormalities that may be causing the symptoms

Diagnostic Algorithm

1. X-ray (radiographs) of the hip and pelvis - First-line imaging

   • Should include AP view of the pelvis and additional views of the proximal femur
   • May reveal:
     • Slipped capital femoral epiphysis (common in adolescents)
     • Avascular necrosis
     • Femoroacetabular impingement
     • Early arthritis
     • Bone tumors
     • Fractures

2. If radiographs are negative or equivocal:

   • MRI without contrast would be the next appropriate step to evaluate:
     • Soft tissue abnormalities
     • Labral tears
     • Early inflammatory changes
     • Bone marrow edema
     • Stress injuries not visible on radiographs

Special Considerations

Hypothyroidism Relevance

The patient's hypothyroidism is an important clinical factor to consider:

• Hypothyroidism can affect bone development and metabolism 2
• It may contribute to delayed skeletal maturation
• Could potentially be associated with slipped capital femoral epiphysis, which is more common in overweight children (patient is in 90th percentile for weight)

Age-Specific Considerations

In pediatric patients with hip pain, important diagnoses to consider include:

• Slipped capital femoral epiphysis (SCFE)
• Legg-Calvé-Perthes disease
• Juvenile idiopathic arthritis 3
• Transient synovitis
• Stress fractures
• Osteomyelitis

Why Other Imaging Options Are Less Appropriate Initially

• CT scan: Higher radiation exposure without significant additional benefit as initial test 1
• MRI: More expensive and may require sedation; appropriate after radiographs if needed 1
• Ultrasound: Limited in evaluating deeper hip structures; better for specific soft tissue abnormalities 1, 4
• Analysis of fluid: Requires joint aspiration which is invasive and not indicated before basic imaging 1

Common Pitfalls to Avoid

1. Skipping radiographs: Going directly to advanced imaging without baseline radiographs can lead to missed diagnoses and inefficient care
2. Attributing symptoms to hypothyroidism alone: While hypothyroidism can affect musculoskeletal development, specific hip pathology should be ruled out
3. Overlooking referred pain: Hip pain can sometimes originate from the spine or knee, which may need evaluation if hip imaging is negative 1
4. Delaying diagnosis: Chronic hip pain in children requires timely evaluation to prevent complications, especially with conditions like SCFE

In conclusion, radiographs (x-rays) represent the most appropriate initial imaging study for this 12-year-old boy with chronic hip pain, providing valuable diagnostic information while minimizing radiation exposure and cost.