Keywords:
Emergency, Musculoskeletal spine, Trauma, CT, MR, Technical aspects, Imaging sequences, Acute, Oedema
Authors:
R. Rajakulasingam1, N. Bhatt2, S. Choudhary2; 1Birmingham/UK, 2University hospital, Birmingham/UK
DOI:
10.26044/ecr2019/C-2669
Results
- 184 consecutive CT scans from 2016-2018 were included in our study.
The basic demographics of our study cohort detailing age and mechanism of injury are stated in (Fig 5)
- 131/184 patients (71%) had a cortical step. 125 were reported as acute compression fractures on CT (true positives),
6 had a step but were reported as chronic compression fractures (false positive) these were reviewed to represent severe osteoporotic wedge fractures/Kummel's disease,
confirmed as chronic clinically.
44 of the 125 patients had a subsequent MRI which confirmed an acute fracture.
- The demographics and morphology of the CT confirmed acute compression fracture group with a step sign is summarised below (Fig 6)
- 53/184 patients had no cortical step sign.
All 53 were concluded as having no acute fracture on CT (true negatives).
Of the 53,
12 patients had MRI to confirm a chronic wedge fracture.
3 patients had no cortical step sign but there was suspicion of an indeterminate fracture on CT.
In 2 of these patients an acute fracture was ruled out clinically,
with no further follow up imaging.
1 patient had subsequent MRI which confirmed chronic wedge compression.
Hence,
no false negative cases for the cortical step sign was seen.
Our results indicate that a cortical step,
independent of other mentioned signs,
has a high diagnostic accuracy in detecting an acute vertebral body compression fracture.
The number of cases of an acute step (131) was almost double the number of cases which exhibited other signs of an acute fracture- sclerotic fracture line (69) and loss in height (77 less than 25 percent height loss).
Although a sclerotic impaction fracture line has been documented as a reliable sign in current literature [6],
a slightly less but similar number of 45 cases showed a lucent fracture line.
Similarly,
nearly half (26/53) the number of cases of confirmed chronic wedge compression fracture showed less than 25 percent vertebral body height loss (Figs 8-9).
Thus,
an impaction fracture line and vertebral body height loss as stand-alone signs may not be as reliable in diagnosing an acute compression fracture.
Wedge compression fractures causing height loss in multiple vertebral bodies are known to be associated with benign osteoporotic aetiology rather than trauma.
There were only 6 cases (4.6%) where a cortical step was seen but a diagnosis of a chronic compression fracture was given due to severe osteoporotic compression with intravertebral cleft,
fragmentation and intact posterior elements,
indicating Kummel’s disease (Fig 10).
This potential false positive for the cortical step sign is important for radiologists to be aware of.
Intravertebral gas on CT and gas/fluid filled clefts on MRI are diagnostic of Kummel disease and was seen in all our false positive cases [3].The other common mimic of an endplate fracture seen in our study were schmorl's nodes.
(Fig 11) [4].Other potential mimics for a cortical step sign described in literature but not seen in our patient cohort are limbus vertebra and notochordal remnant [5].