Clinical History
86-year-old patient who reported 5 days of lumbosacral pain after a fall on a bus.
Imaging Findings
X-RAY
Sacral fractures can often be difficult to visualize on an AP radiograph because of the inclination angle of the sacrum.
CT:
Multiple sacral fractures are observed. We will classify them following the two main classifications known for sacral fractures without other pelvic ring fractures:
DENIS CLASSIFICATION (Key point: to assess possible neurologic damage)
- Fig.1: ZONE 1 FRACTURES
These fractures are lateral to the sacral foramina.
- Fig.2 and Fig.3: ZONE 2 FRACTURES
These fractures involve one or more of the foramina. Neurologic deficits occur in a few cases.
- Fig.4: ZONE 3 FRACTURE
A transverse zone 3 fracture, subtype 2 (partial anterior translation and hyperkyphotic) is observed. This kind of fractures could be caused by a direct trauma. Neurologic damage was not found in our case.
ISLER CLASSIFICATION (Key point: to assess lumbosacral stability)
Sacral fractures have caused a type A lumbosacral injury: fracture line is lateral to L5-S1 facet, no lumbosacral instability was found (Fig.5).
Discussion
A- BACKGROUND [1, 2]
- Sacral fractures most commonly occur after pelvic ring injuries.
- Sacral fractures are generally classified into three categories:
1. Those associated to pelvic ring fractures: Letournel, Tile, and AO-ASIF classification systems.
2. Those that involve the lumbosacral junction (Isler classification).
3. Those intrinsic to the sacrum (Denis classification).
- Isolated sacral fractures are typically caused by high-energy traumas. They tend to associate with vertical shear pelvic fractures and are usually unstable.
- Sacral fractures associated with lateral compression pelvic fractures are usually stable.
B - CLINICAL PERSPECTIVE
This is a case of multiple sacral fractures without other pelvic ring fractures. Accordingly, we will be using Denis classification in the first place. Second, we will use Isler classification due to lumbosacral extension of these factures.
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C- DENIS CLASSIFICATION [3, 4]
(Key point: to assess possible neurologic damage)
1. Zone 1 fractures (Fig.1)
- These fractures are lateral to the sacral foramina.
Neurologic deficits are unlikely, although sciatic nerve or L5 nerve root could be damaged.
Sacral stress fractures occur in the sacral wing (zone 1).
2. Zone 2 fractures (Fig.2; Fig.3)
- These fractures involve one or more of the foramina.
Neurologic deficits occur in a few cases, presenting with unilateral lumbar or sacral radiculopathies.
- If a shear component is present, they are highly unstable.
3. Zone 3 fractures (Fig.4)
- These fractures involve the central sacral canal.
Neurologic damage is likely (sexual or sphincter dysfunction, bladder incontinence, saddle anaesthesia).
- Transverse zone 3 fractures are classified as zone 3 fractures (traverse the spinal canal). S1- S3 involvement, higher prevalence of bladder dysfunction.
Roy-Camille et al. and Strange-Vognsen and Lebech have further classified these fractures:
.
- Type 1: Simple flexion deformity of the sacrum, kyphotic angulation.
- Type 2: Partial anterior translation and hyperkyphotic (Fig.4).
- Type 3: Complete anterior translation with no fracture overlap.
- Type 4: Comminution of the S1 vertebral body caused by axial loading.
Transverse fractures have also been described based on morphology as H, U, lambda and T-shaped fractures.
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D- ISLER CLASSIFICATION [4]
(key point: to assess lumbosacral stability)
It is based on the injury at the lumbosacral junction (relative to the L5-S1 facet).
-Type A- lateral to L5-S1 facet, no lumbosacral instability (Fig.5).
-Type B- through the L5-S1 facet joint.
-Type C- medial to the facet joint, crossing into the neural arch (significant instability). Bilateral type III injuries may lead to lumbosacral dissociation.
Differential Diagnosis List
Multiple sacral fractures (without other pelvic ring fractures).
Pelvic fractures
Vertebral fractures
Final Diagnosis
Multiple sacral fractures (without other pelvic ring fractures).
