The purpose of this study was to describe the
radiological characteristics of a previously unreported finding: posterior
iliac offset at the sacroiliac joint and to assess its association
with pelvic instability as measured by initial displacement and
early implant loosening or failure. Radiographs from 42 consecutive
patients with a mean age of 42 years (18 to 77; 38 men, four women)
and mean follow-up of 38 months (3 to 96) with Anteroposterior Compression
II injuries, were retrospectively reviewed. Standardised measurements
were recorded for the extent of any diastasis of the pubic symphysis,
widening of the sacroiliac joint, static vertical ramus offset and
a novel measurement (posterior offset of the ilium at the sacroiliac
joint identified on axial CT scan). Pelvic fractures with posterior
iliac offset exhibited greater levels of initial displacement of
the anterior pelvis (anterior sacroiliac widening, pubic symphysis
diastasis and static vertical ramus offset, p <
0.001,0.034 and
0.028, respectively). Pelvic fractures with posterior ilium offset
also demonstrated higher rates of implant loosening regardless of
fixation method (p = 0.05). Posterior offset of the ilium was found
to be a reliable and reproducible measurement with substantial inter-observer
agreement (kappa = 0.70). Posterior offset of the ilium on axial
CT scan is associated with greater levels of initial pelvic displacement
and early implant loosening. Cite this article:
