Sacral Fractures
Sacral Fractures and SI Joint Dislocations
Epidemiology
- Considered pelvic ring injuries.
- Typical in:
- Young males with high-energy mechanisms.
- Insufficiency fractures seen in the elderly.
- Young males with high-energy mechanisms.
Anatomy
- Sacrum: Comprises S1 to S5 bodies.
- Rarely, S1 can be lumbarised or L5 sacralised.
- Contains 4 foramina.
- Rarely, S1 can be lumbarised or L5 sacralised.
- Nerve Roots:
- S1–S4 roots exit anteriorly through the foramina.
- S5 root exits below the sacrum.
- L5 root lies on the sacral ala, 2 cm medial to the SI joint.
- S1–S4 roots exit anteriorly through the foramina.
- SI Joint:
- Extends down to the level of the 3rd foramina.
- Inherently unstable due to poor bony congruity.
- Extends down to the level of the 3rd foramina.
- Stability is provided by:
- Ligaments:
- Anterior, interosseous, and posterior sacroiliac ligaments.
- Posterior sacroiliac ligament is the strongest and last to fail.
- Posterior sacroiliac ligament is the strongest and last to fail.
- Sacrotuberous and sacrospinous ligaments.
- Anterior, interosseous, and posterior sacroiliac ligaments.
- Ligaments:
Classification and Fracture Patterns
Denis Classification
Based on the fracture line’s relation to the foramina:
| Type | Features | Notes |
|---|---|---|
| Zone 1 | Lateral to foramina | 50% of all fractures, 5% neurologic injury. |
| Zone 2 | Through the foramina | 30% incidence, 30% neurologic injury. |
| Zone 3 | Medial to foramina | 20% incidence, 60% neurologic injury. |
- Zone 1 and 2 fractures:
- Tend to be vertical or oblique.
- Do not cause spinal instability but may result in pelvic instability.
- Tend to be vertical or oblique.
- Zone 3 fractures:
- May be vertical or horizontal.
- Horizontal fractures occur through the vestigial disc space due to hyperflexion.
- May be vertical or horizontal.
- Key Points:
- Any fracture may cause root or cauda equina injury.
- Spinal instability and spino-pelvic dissociation may occur with horizontal fractures.
- Pelvic instability may occur with vertical fractures.
- Comminuted or oblique fractures may result in instability of both spine and pelvis.
- Vertical shear injuries increase the likelihood of neurologic injury.
- Any fracture may cause root or cauda equina injury.
Crescent Fracture
- Iliac wing fracture that exits through the SI joint, possibly causing SI joint dislocation.
- Typically an LC2 injury.
Management Principles
Non-Operative Management
- Indicated for:
- Stable pelvic ring.
- Congruent SI joint.
- No cauda equina syndrome.
- Impacted sacral fractures (often stable, especially in LC injuries).
- Stable pelvic ring.
Goals of Surgery
- Reduce the SI joint and pelvic ring.
- In anterior and posterior ring injuries, stabilize the posterior ring first.
- In anterior and posterior ring injuries, stabilize the posterior ring first.
- Decompress neural injuries.
- Prevent iatrogenic neural injury.
- Stabilize the spine if necessary.
Methods of Stabilization
Percutaneous Iliosacral Screws
- Key Points:
- Typically 1 or 2 screws.
- Requires clear imaging and an experienced surgeon.
- Joint must be reducible through closed techniques.
- Can be performed with the patient in prone or supine position.
- Typically 1 or 2 screws.
- Main Risk: Injury to the L5 nerve root.
ORIF (Open Reduction and Internal Fixation)
- Preferred Technique: Posterior plates to restore tension band.
- Additional Considerations:
- May require anterior supplementation.
- Can be combined with iliosacral screws.
- Avoid over-compression of foramina when reducing fractures.
- May require anterior supplementation.
Lumbopelvic Fusion
- Indication: Spinal instability.
- Method: Fuse into the lumbar spine using plates or pedicle screws and bars.