The injury shown in Video A reveals a right sided posterior ilium fracture, which is known as a crescent fracture. The presence of a crescent fracture is consistent with a lateral compression type 2 injury; this differentiates this from a type I injury. The ipsilateral anterior sacrum has a small impaction injury anteriorly while the contralateral SI joint has a minor amount of anterior sacral impaction indicative of a lateral compression type I injury.
The reference by Burgess et al is the primary source of the mechanism classification of pelvic ring injuries. Overall blood replacement averaged 5.9 units (lateral compression, 3.6 units; anteroposterior compression, 14.8 units; vertical shear, 9.2 units; combined mechanical, 8.5 units). Overall mortality was 8.6% (lateral compression, 7.0%; anteroposterior, 20.0%, vertical shear, 0%; combined mechanical, 18.0%).
1: The presence of a crescent fracture means this is at least a LC-2 injury. The left-sided fracture pattern is consistent with an LC-1 pattern.
3: A vertical shear fracture pattern would exhibit some vertical displacement and does not typically exhibit the crescent fragment.
4: The fracture pattern does not match an anterior-posterior compression pattern.
5: The fracture pattern does not match an anterior-posterior compression pattern.
Burgess AR, Eastridge BJ, Young JW, Ellison TS, Ellison PS Jr, Poka A, Bathon GH, Brumback RJ. Pelvic ring disruptions: effective classification system and treatment protocols. J Trauma. 1990 Jul;30(7):848-56.
PMID:2381002 (Link to Abstract)