An APC type 1 involves slight widening of pubic symphysis and/or anterior sacroiliac (SI) joint. An APC II is a continuation of this force, and additionally involves a disrupted anterior SI joint, as well as sacrotuberous and sacrospinous ligaments. An APC III also involves disrupted posterior SI ligaments, causing complete SI joint disruption with potential translational and rotational displacement.
The reference by Young et al is a classic article that describes the Young and Burgess classification of pelvic ring injuries. They retrospectively analyzed pelvic ring radiographs and discussed four patterns of injury: anteroposterior compression, lateral compression, vertical shear, and a complex/combined pattern.
The reference by Burgess et al is a validation of the aforementioned classification and study, as they reviewed 210 consecutive patients who sustained a pelvic ring injury. They validated the classification scheme and found that overall blood replacement averaged: lateral compression, 3.6 units; anteroposterior compression, 14.8 units; vertical shear, 9.2 units; combined mechanical, 8.5 units. Overall mortality was: lateral compression, 7.0%; anteroposterior, 20.0%, vertical shear, 0%; combined mechanical, 18.0%.
1,2,4,5: An APC - 2 pelvic ring injury involves injury to all of these structures.
Young JW, Burgess AR, Brumback RJ, Poka A. Pelvic fractures: value of plain radiography in early assessment and management. Radiology. 1986 Aug;160(2):445-51.
PMID:3726125 (Link to Abstract)
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)