Stages of Syndesmotic Changes in Vertebral Body
Syndesmotic changes in vertebral bodies progress through three distinct stages characterized by dysfunction, instability, and stabilization, with specific pathological findings at each stage.
Pathophysiological Stages of Syndesmotic Changes
Stage 1: Temporary Dysfunction
- Early degenerative findings with normal disc height
- Two substages:
- Stage 1A: Normal disc height without dehydration
- Stage 1B: Normal disc height with dehydration
- Mean vertical mobility: 2.0-2.2 mm 1
- Minimal clinical symptoms may be present
- Early inflammatory changes at sites of ligament and bone insertion
Stage 2: Instability
- Characterized by progressive disc height loss (decreased by less than 50%)
- Increased intervertebral mobility (mean vertical mobility of 2.6 mm) 1
- Development of segmental deformity
- Prominent fibrosis begins to form
- Syndesmophytes may begin to develop, particularly at the posterolateral rim 2
- More pronounced clinical symptoms including pain, sensory changes, and potential motor weakness
Stage 3: Definitive Stabilization
- Significant disc height reduction (decreased by at least 50%)
- Significantly reduced vertical mobility (mean 0.8 mm) 1
- Osteoligamentary repair mechanisms lead to stabilization
- Advanced syndesmophyte formation and potential fusion
- Potential for spinal stenosis due to posterior syndesmophyte formation 3
- Clinical symptoms may include decreased hand dexterity, gait instability, and sensory/motor dysfunction 4
Syndesmophyte Formation Patterns
Syndesmophytes are not randomly distributed around the vertebral rim but show preferential development:
- Most common at the posterolateral vertebral rim
- Least common at the posterior and anterior rim 2
- Distribution varies by vertebral level:
- Most pronounced posterolateral localization at T10-T11, T12-T12, and T12-L1
- Less localization at L2-L3 and L3-L4 2
Clinical Implications
The progression through these stages has important clinical implications:
- Early identification of syndesmotic changes can help prevent progression to advanced stages
- Patients with significant disc height reduction (Stage 3) may still have some mobility, requiring careful evaluation 1
- Posterior syndesmophytes can lead to symptomatic spinal stenosis, requiring different management approaches 3
- MRI is the preferred imaging modality for evaluating soft tissues and neural elements in patients with suspected myelopathy 4
Diagnostic Considerations
When evaluating syndesmotic changes:
- CT provides excellent sensitivity (94-100%) for identifying vertebral fractures and bony changes 5
- MRI is superior for evaluating ligamentous injuries and spinal cord damage 5
- Radiostereometric analysis (RSA) can be used to precisely measure intervertebral mobility through the degenerative stages 1
Important Caveats
- Inter-individual differences in mobility are pronounced even within the same disc degeneration stage 1
- A fully stable situation cannot be guaranteed even when disc height is reduced by more than 50% 1
- The presence of syndesmophytes does not always correlate with clinical symptoms
- Progression rates vary significantly between patients
- Posterior syndesmophytes, though less common, may have more significant clinical impact due to potential for spinal stenosis 3
Understanding these stages helps guide appropriate management and predict potential complications of syndesmotic changes in vertebral bodies.