CASE 25 sacral fracture

 

A 24-year-old male presents following a motor vehicle collision. His primary complaint is of lower back pain. No focal neurological deficits are noted on his examination. An axial cut of his CT scan is shown in Figure 6–30.

 

 

 

Figure 6–30

 

Given the location of the vertical component of this patients sacral fracture; what is the rate of neurological deficit (either lower extremity symptoms or bowel, bladder, or sexual dysfunction) associated with this injury pattern?

1. 6%

2. 28%

3. 45%

4. 57%

 

Discussion

The correct answer is (B). The rate of neurologic injury associated with Denis Type II sacral fractures (through the sacral foramen) is 28%. The rate for Type I (lateral to the foramen) and Type III (medial to the foramen) injuries are 6% and 57%, respectively.

Nonsurgical treatment of sacral fractures is considered a reasonable option in all of the following scenarios, EXCEPT which of the following?

1. Neurologically intact patient with a displaced transverse fracture at the level of the S4 foramen.

2. A neurologically intact patient with a unilateral nondisplaced Denis Type II fracture involving the ventral sacral cortex.

3. A neurologically intact patient with a unilateral displaced Denis Type I fracture involving both the ventral and dorsal cortices.

4. A neurologically intact elderly patient with bilateral nondisplaced Denis Type II fracture involving only the ventral cortex.

Discussion

The correct answer is (C). Nonsurgical management is typically reserved for patients with a sacral fracture morphology that does not compromise spinopelvic stability. As such nondisplaced fractures that are below the SI Joint (response A) or only involving one cortex (responses B and D) may undergo these conservative treatment modalities.

The decision is made to treat the patient’s sacral fracture with percutaneous sacroiliac screws.

Which view will minimize the risk of iatrogenic foot drop due to aberrant hardware placement?

1. Inlet pelvic view

2. Obturator outlet pelvic view

3. Iliac oblique pelvic view

4. Outlet pelvic view

 

Discussion

The correct answer is (A). The pelvic inlet view will allow visualization of the anterior to posterior trajectory of the sacroiliac screw, thus allowing the surgeon to avoid anterior breach and lower lumbar root injury, which drapes over the ventral surface of the sacral ala.

All are radiographic findings that represent varying presentations of sacral dysmorphism EXCEPT which of the following?

1. The sacral alae are at the same level as the iliac crest on the outlet view

2. Recession of the anterior alar cortex on the axial CT view

3. Residual disc space between the upper two sacral segments on the outlet view

4. Paradoxical inlet view of the upper sacral segments on the AP or outlet views

Discussion

The correct answer is (D). This represents occult sacral fracture dislocation or U-type sacral fracture. Sacral dysmorphism is a collective term to describe multiple aberrations in sacral osteology that may preclude safe hardware placement if not recognized preoperatively. The sacral alar anatomy and slope are variable. Upper sacral segment abnormalities are common. Predictable dysplastic patterns can be easily identified using pelvic outlet and true lateral sacral plain radiographs along with CT scans and include:

 

1. The sacrum is not recessed within the pelvis on the outlet image.

2. Mammillary processes are seen on the outlet image.

3. The upper sacral foramen is dysmorphic on the outlet image.

4. The alar slope is acute on the lateral view.

5. A residual disc space between the upper two sacral segments is seen on the outlet image.

6. “Tongue-in-groove” SI articulations are noted on the CT scan.

 

 

Objectives: Did you learn...?

 

Denis classification of sacral fractures and corresponding frequency of neurologic injury?

 

 

Complications associated with the placement of percutaneous iliosacral screws? Characteristics of sacral dysmorphism?