lesions are graded as Type I, Type II, or Type III depending on degree of instability;
Bucholz noted that on postmortem dissection of pts w/ pelvic fractures that all injuries to pelvic ring had some injury to both anterior and posterior portions of the pelvis;
Type I
injuries for which the roentgenograms reveal only anterior rami frxs demonstrated at least hemorrhage & partial disruption of posterior SI ligaments;
Type II
lesion is similar to the AP compression lesion;
it is characterized by the presence of anterior instability and partial posterior instability.
Type III
lesion demonstrates complete anterior and posterior instability;
instability is secondary to both the bony and the ligamentous disruption of pelvic ring;
degree of ligamentous disruption is a key to stability because fracture alone will not produce instability without associated displacement and ligamentous disruption