1. Alex Sun, MD Faculty Advisor: Peter Pham, MD
Sensitivity and specificity of sacral arcuate line disruption for fractures on plain radiography
Alex Sun, MD
Faculty Advisor: Peter Pham, MD

2. Background
Sacral fractures can occur in young adults after high energy trauma and elderly patients in low energy falls
Sacral fractures are frequently underdiagnosed
Only 49% of sacral fractures are diagnosed on initial hospital visit
Patients may go on to develop neurologic deficits due to inadequate treatment
Depending on location of fracture neurologic injury is common
Symptoms include lower extremity weakness
Urinary and rectal dysfunction
Sexual dysfunction

3. Treatment Non-operative management Operative management
Non-displaced fractures
No neurologic injury
Operative management
Displaced or unstable fractures
Associated pelvic ring disruption
Neurologic injury

4. Imaging
Lines represent roof of the anterior sacral foramina and neural grooves
Superior three arcs are most common seen
Abnormalities of the sacral arcuate lines are indicative of fracture

5. Imaging Specific findings that indicate SL disruption
Line discontinuity
Deformity
Displacement
Density change

6. Line discontinuity

7. Deformity
Angulation or buckling of lines

8. Displacement
Increased distance between arcs

9. Density Change
Compression or callus formation

10. Question and Hypothesis
How sensitive and specific are the sacral arcuate lines for sacral ala fractures?
No study has been conducted to evaluate the sensitivity and specific of SL.
Hypothesis: the sacral arcuate lines are both very sensitive and specific for sacral ala fractures

11. Method
Compiled a list of ~300 patients with documented sacral ala fractures seen on CT
Each patient must have initial pelvic radiograph
Age ranged from years old.
Pediatric and pregnant patients excluded
Insufficiency and pathologic fractures excluded
Retrospectively reviewed the initial AP pelvic radiographs.
Findings that indicate SL disruption
Line discontinuity, displacement, deformity, density change
Asymmetry
Record percentage of fractures on missed on initial plain film
Determine any limitations and confounding factors
Such bowel gas, osteopenia, positioning

12. Results Initial Diagnosis 20% 299 Patients 59 Excluded
186 Positive Radiographs
76% Sensitivity for all ages
84% Sensitivity for years old
59 Negative Radiographs

13. Results

14. Results

15. Marginal fractures Minimally displaced Above the sacral lines
Can be seen on radiograph but arcuate lines are intact

16. Conclusion
Sacral arcuate line disruption is sensitivity for sacral fractures
Particularly year old population
Evaluation sacral arcuate lines can improve sensitivity for sacral fractures
20% initial diagnosis on radiograph

17. Future Study Prospective blind study using a list of 50 cases:
10 cases will have sacral +/- pelvic fractures
Remaining cases will all have pelvic fractures
Recruit attending to review case set
MSK attending
Future QI project
Create primer/lecture to educate residents on specific findings
Compare sensitivity before and after primer/lecture.

18. Citation
Mehta S, Auerbach JD, Born CT, Chin KR. Sacral fractures. J Amer Acad Orthop Surg. 2006; 14(12):
Denis F, Davis S, Comfort T: Sacral fractures: an important problem. Retrospective analysis of 236 cases. Clin Orthop Relat Res 227:67–81, 1988
Digital image. American Academy of Orthopedic Surgeons. N.p., n.d. Web. 29 Aug
Bydon, Mohamad, MD, and Ziya L. Gokaslan, MD. "Sacral Fractures." Neurosurgical Focus 37.1 (2014): E12. Journal of Neurosurgery. Web. 25 Aug
Hak D, Baran S, Stahel P. Sacral Fractures: Current Strategies in Diagnosis and Management. ORTHOPEDICS. 1; 32: doi: /  
Jackson H, Kam J, Harris JH Jr, Harle TS. (1982). The sacral arcuate lines in upper sacral fractures. Radiology. Oct;145(1):35-9.