What is the appropriate evaluation and treatment for a toddler with hip pain?

Toddler Hip Pain: Evaluation and Treatment

Initial Approach

Begin with plain radiographs of the hip and pelvis as the first imaging test, followed by urgent ultrasound if septic arthritis is suspected based on fever, inability to bear weight, or elevated inflammatory markers. 1

Critical First Steps

• Assess temperature immediately - fever >101.3°F (38.5°C) combined with inability to bear weight strongly suggests septic arthritis, which requires intervention within hours to prevent permanent joint damage 2, 3
• Obtain plain radiographs first in nearly all cases to screen for fractures (including toddler's fracture of the tibia), osteonecrosis, slipped capital femoral epiphysis, and Legg-Calvé-Perthes disease 1, 4
• Check inflammatory markers (ESR and CRP) alongside temperature, as all children with septic arthritis have at least two of these three criteria: fever, elevated ESR, or elevated CRP 3

Diagnostic Algorithm for Septic Arthritis vs. Transient Synovitis

High-Risk Features Requiring Urgent Ultrasound

If any two of the following are present, proceed immediately to hip ultrasound 3:

• Fever (temperature >37.5°C/99.5°F)
• Elevated ESR (≥20 mm/hour)
• Elevated CRP

Ultrasound-Guided Decision Making

• If effusion present on ultrasound AND two or more high-risk criteria: perform ultrasound-guided aspiration for cell count, Gram stain, and culture 1, 3
• If no effusion on ultrasound AND fewer than two high-risk criteria: septic arthritis is effectively ruled out 3
• Ultrasound is particularly useful in the pediatric population for identifying effusions before joint aspiration or surgical debridement 4

Treatment Based on Diagnosis

Septic Arthritis (Confirmed)

• Immediate surgical drainage (open arthrotomy or arthroscopic) combined with empirical antibiotics targeting Staphylococcus aureus (most common at all ages) and Kingella kingae (most common in children 6 months to 4 years) 5, 6
• Short-course antibiotics (2 weeks) are increasingly used in uncomplicated cases with good outcomes 5, 7
• Time is critical: functional sequelae including growth disturbances, osteonecrosis, chondrolysis, and permanent joint damage occur if treatment is delayed 5, 6

Transient Synovitis (Most Common Diagnosis)

• Bed rest and NSAIDs with regular temperature monitoring to exclude development of fever 8
• Transient synovitis is most common in children 3-10 years of age and typically presents with 1-3 days of hip pain and limping 8
• Re-evaluate if significant pain and limping persist 7-10 days after initial presentation 8

Other Diagnoses

• Toddler's fracture (spiral tibial fracture): Consider even with negative initial radiographs, as 10% only appear on follow-up films 1, 2
• Osteomyelitis: If suspected based on persistent symptoms or clinical deterioration, obtain MRI for definitive diagnosis 1
• Juvenile idiopathic arthritis: Consider if symptoms are chronic or recurrent 1

Critical Pitfalls to Avoid

• Never assume normal radiographs exclude fracture - approximately 10% of tibial fractures are only visible on follow-up radiographs 1, 2
• Never focus only on the reported pain site - hip pathology presents as thigh or knee pain in 30% of cases due to referred pain patterns 2
• Never delay evaluation when fever and inability to bear weight coexist - septic arthritis causes permanent damage within hours 2, 5
• Never rely on radiographs alone for acute hip pain - they have no significant impact on decision-making for differentiating septic arthritis from transient synovitis 3

Red Flags Requiring Immediate Action

• Severe pain or spasm on hip movement or palpation 8
• The "three As": anxiety, agitation, high analgesic requirement (sensitivity 80%, specificity 90% for serious pathology including compartment syndrome) 2
• Inability to bear weight combined with any systemic signs 2, 3
• Worsening clinical condition despite initial treatment - obtain MRI to evaluate for complications 5