Morphological analysis of the posterior elements of associated both-column acetabular fractures

It is still in dispute as to whether a posterior approach is applied to reduce the posterior fractures of associated both-column acetabular fractures (ABC-AFs).To analyze the morphological changes in the posterior elements including the posterior column (PC) and/or associated posterior wall (PW) fragments to provide a reference for surgical planning.The 3D computed tomography (CT) data of 100 cases of ABC-AFs were retrospectively analyzed using Mimics and 3-Matic software. The line distribution of the retroacetabular surface (RAS), the acetabular fossa, and the size of the PW fragments were analyzed.Fracture lines (n = 89) on RAS appeared in three patterns: transverse lines (n = 41) on the cephalic (65.8%) and caudal (29.3%) thirds; oblique lines (n = 34) on the mid-caudal thirds; and multifragmentary lines (n = 14). The lines of the displaced PW fragment (n = 61) were widely distributed in intra- and extra-articular regions. The mean radian of the PW fragments was >90° in 67.2% of cases and involved anteriorly to the vertex in 90.2% of cases. The average fracture span on the RAS was 0.60-1.00 in 63.9% of cases. The mean length of the spike of PW fragments was >20 mm in 80.3% of cases.For PC fractures, transverse lines on the cephalic third of RAS indicated a possibility of the anterior approach, while transverse lines on the distal third or oblique and multifragmentary lines suggest the posterior approach. A displaced PW fragment was involved more extensively both intra-and extra-articularly and may be optimally treated via a posterior approach.