Toddler's Fracture
The most likely diagnosis is a toddler's fracture—a nondisplaced spiral fracture of the distal tibia that is frequently not visible on initial radiographs. 1
Clinical Presentation and Diagnosis
This 2-year-old boy presents with the classic triad for toddler's fracture:
- Acute refusal to bear weight following minor trauma (tripping while running) 2, 3
- Localized tenderness over the anterior tibia 3, 4
- Normal initial radiographs 1
The American College of Radiology explicitly states that approximately 10% of tibial fractures are only visible on follow-up radiographs and not on initial imaging, making this a well-recognized diagnostic challenge 1, 5. In one study, 41% of children with presumptive toddler's fracture by clinical criteria had negative initial radiographs but showed fracture evidence on follow-up films 1.
Why This is a Toddler's Fracture
Toddler's fracture is defined as a minimally displaced or nondisplaced spiral fracture of the distal tibial shaft (typically distal third) in ambulatory children aged 9 months to 3 years, caused by twisting injury during tripping, stumbling, or falling 2, 3, 6. This patient's mechanism (tripping on grass while running) and age (2 years) fit perfectly 3, 4.
The normal hip and knee examination effectively rules out:
- Septic arthritis (would show hip effusion, fever, elevated inflammatory markers) 7
- Hip pathology like Legg-Calvé-Perthes disease 7
- Femoral fractures 1
Management Approach
Treat this child presumptively as a toddler's fracture even with negative radiographs 3, 8:
Immobilization: Use a controlled ankle motion (CAM) boot or short leg back slab rather than a cast—these are associated with fewer complications, can be removed by family, and allow faster return to weight-bearing (average 2.5 weeks vs 2.8 weeks for cast) 3, 8
Analgesia: Short-course NSAIDs are appropriate 7
Follow-up strategy:
- Clinical reassessment in 1-2 weeks if symptoms persist 5, 7
- Repeat radiographs at 10-14 days will show periosteal reaction in 93% of initially radiograph-negative cases, confirming the diagnosis 8
- However, follow-up radiographs may be unnecessary for treatment planning since these fractures are universally stable and nearly all children regain weight-bearing by 4 weeks regardless of immobilization type 8
Orthopedic referral: Not needed for most uncomplicated cases 3
Critical Pitfalls to Avoid
Never assume normal initial radiographs rule out fracture in this clinical scenario 1, 5, 7. The combination of appropriate mechanism, age, localized tibial tenderness, and refusal to walk is diagnostic even without radiographic confirmation 3, 4.
Do not miss red flags for serious pathology 7:
- Fever >101.3°F would suggest septic arthritis requiring urgent ultrasound 7
- The "three As" (anxiety, agitation, high analgesic requirement) may indicate compartment syndrome or other serious pathology 7
- Worsening symptoms despite treatment warrant immediate reassessment—one case series documented a child initially discharged who returned with spinal discitis and epidural abscess 1
Consider non-accidental injury if red flags present 2, though the mechanism described here (witnessed minor trauma with appropriate injury pattern) is consistent with accidental injury 1.
Expected Course
Weight-bearing typically returns by 4 weeks, with 98% of children walking by this timepoint 8. No fractures displaced at any time point in a cohort of 192 patients, including 7 who received no immobilization, confirming the inherent stability of this fracture pattern 8.