These fractures are a combination of the two elemental fracture patterns: posterior column and posterior wall. The posterior column component is often nondisplaced, and the wall fracture is the more obvious component. The prevalence of this fracture is low (3.4% [Matta, Letournel]).
The posterior wall fractures involve the rim of the acetabulum, a portion of the retroacetabular surface, and a variable segment of the articular cartilage.
Posterior column fractures originate at the greater sciatic notch, pass through the roof or weight bearing dome and exit through the obturator ring. The result is a complete detachment of the posterior column, in this case associated with fractures of the posterior wall. The fracture is usually displaced posteriorly, medially, and in internal rotation, as the posterior column rotates about the ischial tuberosity. As the femoral head is driven through the posterior column and fractures it, it tends to open up the posterior column like a swinging door, moving posteriorly into the pelvis.
Posterior column and wall fractures may be associated with femoral head fractures.
The superior gluteal vessels and nerves can be at risk from displaced fragments.
High-energy trauma is the primary cause in younger individuals and association with other fractures and pelvic ring disruptions are common. Fractures secondary to moderate or minimal trauma are increasingly of concern in those over 60 years because of osteoporotic changes.