What are the management options for a 3.3 mm posterior displacement of the fifth sacral vertebra (S5) in relation to the fourth sacral vertebra (S4)?

Management of 3.3 mm Posterior Displacement of S5 in Relation to S4

For a 3.3 mm posterior displacement of S5 in relation to S4, non-operative management with a lumbosacral orthosis is recommended as the primary treatment approach, as this represents a stable sacral fracture that does not require surgical intervention. 1

Fracture Assessment and Classification

• CT scans are the gold standard for evaluating sacral fractures, as plain radiographs miss approximately 35% of sacral fractures 1
• MRI is particularly valuable for detecting associated soft tissue injuries and neurological compromise that may accompany the sacral displacement 1
• The 3.3 mm displacement falls within the range considered stable for sacral fractures, as displacements requiring surgical intervention typically exceed 5 mm 2

Treatment Approach Based on Displacement Magnitude

• For sacral displacements less than 5 mm without neurological compromise, non-operative management is the preferred approach 1
• A thoracolumbosacral orthosis (TLSO) is the recommended orthotic device for stable S5 fractures or displacements 1
• The orthotic should be worn for 6-12 weeks to allow for proper healing and to prevent further displacement 1

Monitoring and Follow-up

• Serial imaging (typically CT scans) at 2-week, 6-week, and 3-month intervals is recommended to ensure the displacement remains stable 1
• If the displacement increases beyond 5 mm or if neurological symptoms develop, surgical intervention should be reconsidered 2
• Pain management should be incorporated into the treatment plan alongside bracing 1

Surgical Considerations

• Surgery is generally reserved for sacral displacements that are:
  • Greater than 5 mm 2
  • Associated with neurological deficits 2
  • Rotationally or vertically unstable 1
• The Subaxial Injury Classification (SLIC) System can help guide management decisions for complex spinal injuries, though it is more commonly applied to cervical injuries 2

Special Considerations

• Lower sacral fractures (S4-S5) generally have better outcomes with non-operative management compared to higher sacral fractures 2
• For sacral chordoma (which should be ruled out as a cause of displacement), surgery is definitely indicated if the lesion arises from S4 and below 2
• The close relationship between functional sparing at different sacral segments means that preservation of S1 function is a good predictor of preserved function at more caudal segments 3

Potential Pitfalls

• Failing to recognize that sacral fractures or displacements are often associated with other pelvic ring injuries that may influence treatment decisions 1
• Assuming that bracing alone is sufficient for unstable fractures that require surgical fixation 1
• Not considering the patient's functional status, particularly regarding bowel and bladder function, which can be affected by sacral injuries 3

Activity Modification

• Weight-bearing status should be limited initially, with gradual progression as healing occurs 1
• Activities that increase axial loading on the spine should be avoided during the healing period 1
• Physical therapy focusing on core strengthening may be initiated after 6-8 weeks if healing is progressing appropriately 1