What is the next best imaging study or intervention for a suspected fracture superior to the femoral condyles on a lateral plain radiograph of the right knee?

Supracondylar Femur Fracture: Next Best Study

Order a CT scan of the knee without contrast to fully characterize the fracture extent, displacement, and comminution before surgical planning. 1

Rationale for CT as Next Step

When plain radiographs demonstrate or raise concern for a supracondylar femur fracture (fracture superior to the femoral condyles), CT is superior to radiographs for fracture detection and characterization. 1

• CT provides 100% sensitivity for detecting fractures around the knee compared to only 83% sensitivity for plain radiographs alone. 1
• CT is essential for accurate classification of complex fractures in this region, enabling precise preoperative planning for internal fixation. 2
• Multislice CT with three-dimensional reconstruction allows surgeons to visualize fracture lines, degree of displacement, articular involvement, and comminution patterns that are critical for determining the optimal surgical approach. 2

Why Not MRI First?

While MRI is the gold standard for soft tissue injuries (meniscal tears, ligamentous ruptures, occult fractures), it is not the appropriate next study when a fracture is already visible or strongly suspected on plain films. 1

• MRI is reserved for situations where radiographs are negative but clinical suspicion remains high for internal derangement or occult fracture. 1, 3
• In your case, the lateral radiograph already shows concerning findings for fracture—CT provides the bony detail needed for surgical decision-making. 1

Clinical Workflow Algorithm

1. Plain radiographs (already obtained): Minimum AP and lateral views identify the fracture. 1, 3
2. CT without contrast (next step): Characterize fracture geometry, measure displacement, assess articular surface involvement, and plan fixation strategy. 1, 2
3. MRI without contrast (optional, later): Consider only if there is concern for concomitant ligamentous injury (ACL, PCL, collateral ligaments) or meniscal pathology that would alter surgical management. 1
4. CT angiography (if indicated): Add CTA only if there are signs of vascular compromise (absent pulses, pallor, cool extremity), as popliteal artery injury can occur with high-energy supracondylar fractures. 4

Common Pitfalls to Avoid

• Do not order MRI as the immediate next study when a fracture is already identified on radiographs—this delays definitive surgical planning without adding actionable information about the bone injury. 1, 3
• Do not skip CT in favor of proceeding directly to surgery based on plain films alone, as underestimation of fracture complexity leads to inadequate fixation and poor outcomes. 1
• Do not forget to assess neurovascular status clinically before and after any manipulation, as supracondylar fractures can compromise the popliteal vessels and peroneal nerve. 4

When to Consider Additional Imaging

• Add CTA immediately if any vascular compromise is present (diminished pulses, expanding hematoma, bruit), as arterial injury requires emergent surgical repair. 4
• Consider MRI later (after fracture stabilization) if there is persistent instability or mechanical symptoms suggesting meniscal or ligamentous injury that was not addressed during initial fracture fixation. 1