What Does Minimally Displaced Rib Fractures Mean?
Minimally displaced rib fractures are fractures where the broken bone ends maintain greater than 90% cross-sectional overlap when viewed on CT imaging, meaning the bone fragments remain nearly aligned with minimal separation or offset. 1
Understanding the Classification System
The World Society of Emergency Surgery (WSES) and Chest Wall Injury Society (CWIS) established a standardized classification system in 2024 that defines rib fracture displacement based on cross-sectional overlap visible on chest CT scans 1:
- Non-displaced (minimally displaced): >90% cross-sectional overlap 1
- Offset: 50-90% cross-sectional overlap 1
- Displaced: >0 to <50% cross-sectional overlap 1
- Severely displaced: No cross-sectional overlap or overlapping ribs 1
The term "cross-sectional overlap" refers to how much of the bone's cortical and cancellous structure remains aligned when viewed on axial and multiplanar CT reformats. 1 This measurement provides better correlation of displacement severity than older methods and improves communication between healthcare providers. 1
Clinical Significance
Minimally displaced rib fractures (>90% overlap) are managed conservatively and do not require surgical stabilization. 2, 3 The high degree of bone contact means these fractures maintain structural integrity and will heal with appropriate pain control and respiratory support. 2
In contrast, displaced fractures with <90% overlap—particularly when three or more ipsilateral ribs in the 3-10 range are involved—become candidates for surgical stabilization of rib fractures (SSRF). 1, 4
Important Clinical Caveat
Research demonstrates that rib fractures can become more displaced over time, even when initially minimally displaced. 5 A 2021 study found that fracture displacement significantly increased in all rib groupings (except ribs 11-12) across all planes between initial and follow-up CT scans, with median time between scans of only 6 days. 5 This means:
- Initial "minimally displaced" fractures may progress to displaced fractures 5
- Clinical reassessment within 1-2 weeks is necessary to monitor for worsening displacement 2, 3
- Pain management strategies should account for potential progression 5
Practical Imaging Interpretation
When reviewing chest CT for rib fractures, the radiologist should assess 1:
- Percentage of cross-sectional overlap on axial images to classify displacement severity 1
- Fracture pattern: simple (single fracture line), wedge (butterfly fragment), or complex (multiple fragments spanning rib width) 1
- Anatomical location: anterior, lateral, or posterior zones 1
The 10% missed fracture rate on initial CT scans emphasizes the importance of careful systematic review. 5