Duration of Acute Vertebral Fracture
A vertebral fracture is considered acute for up to 6 weeks after injury, though bone marrow edema on MRI typically resolves within 1 to 3 months, and clinical definitions vary from 6 to 12 weeks depending on the classification system used. 1
Time-Based Classification Framework
Standard Clinical Definitions
Less than 6 weeks: The American College of Radiology defines fractures of less than 6 weeks' duration as acute, particularly when considering vertebral augmentation procedures 1
Up to 3 months: Bone marrow edema on MRI, which is the radiologic hallmark of acute fracture, typically resolves within 1 to 3 months after injury 1
Traditional classification systems: The Willenegger and Roth classification defines early-onset (acute) infections as occurring within 3 weeks, delayed within 3-10 weeks, and late-onset beyond 10 weeks, though this applies specifically to fracture-related infections rather than fracture acuity itself 1
Alternative threshold: Some authors propose a 6-week cutoff to differentiate between acute and chronic infections in the fracture context 1
Important Nuance About "Acute" Definition
The definition of "acute" remains somewhat arbitrary and context-dependent, as there is no universally accepted time cutoff. 1 The classification depends on:
- Clinical presentation: Pain severity and functional impairment 1
- Radiologic findings: Presence of bone marrow edema on MRI 1
- Treatment considerations: Timing for intervention decisions 1
Radiologic Markers of Fracture Age
MRI Findings
Bone marrow edema: Present in acute fractures and typically resolves within 1-3 months, though this is not a precise measure of fracture age 1
Posterior wall intensity changes: On T1-weighted MRI, 83.5% of acute fractures show intensity changes in the posterior wall, which decreases to 41.7% after 6 months 2
Fluid-sensitive sequences: STIR or fat-saturated T2-weighted imaging are most helpful for detecting acute fractures 1
Plain Radiograph Findings
Vertebral height loss: Acute fractures rarely show significant collapse in the first 2 weeks after injury 2
Anterior vertebral height ratio (AVHR): An AVHR >75% combined with posterior wall intensity changes on MRI provides 87.1% specificity and 84.7% positive predictive value for diagnosing acute fracture 2
Clinical Course and Natural History
Pain Resolution Timeline
Acute pain duration: Most patients experience intense pain lasting 4-6 weeks at the fracture site 3
Gradual improvement: Most vertebral compression fractures show gradual improvement in pain over 2-12 weeks with variable return of function 1
Spontaneous resolution: Most patients have spontaneous resolution of pain within 6-8 weeks, even without medication 1
Common Pitfall to Avoid
Do not assume that vertebral body edema precisely indicates fracture age—the duration after an osteoporotic compression fracture is often not known with certainty, and edema can persist beyond the typical acute phase. 1 This is particularly important when:
- Patients present late after injury 1
- Multiple fractures of different ages are present 1
- Clinical examination is confusing due to multiple deformities 1
Treatment Implications Based on Fracture Age
Acute Phase (< 6 weeks)
Vertebral augmentation: Studies demonstrate superiority over placebo for pain reduction in patients with acute osteoporotic vertebral compression fractures of less than 6 weeks' duration 1
Conservative management: Appropriate first-line treatment with analgesics, limited bed rest, and physical therapy 1
Beyond Acute Phase (> 12 weeks)
Fracture age does not preclude intervention: Patients with vertebral compression fractures greater than 12 weeks have equivalent benefit from vertebral augmentation compared to those with fractures less than 12 weeks, suggesting fracture age does not independently affect outcomes 1
Failed conservative therapy threshold: Vertebral augmentation may be offered after 3 months of failed conservative therapy 1